This work was supported by the National Institutes of Health [grant numbers R01AI29329, R01AI42552 and R01HL07470 to J.J.R.] and National Cancer Institute of the National Institutes of Health [grant number P30CA033572 to support City of Hope Integrative Genomics, Analytical Pharmacology, and Analytical Cytometry Cores]. The following reagent was obtained through the NIH AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: HIV BaL virus.

All animal care and procedures have been performed according to protocols reviewed and approved by the City of Hope Institutional Animal Care and Use Committee (IACUC) held by the principal investigator of this study (Dr. John Rossi, IACUC #12034). Human fetal liver tissue was obtained from Advanced Bioscience Resources (Alameda, CA), a nonprofit organization, in accordance with federal and state regulations. The vendor has its own Institutional Review Board (IRB) and is compliant with human subject protection requirements. Human PBMCs are isolated from discarded peripheral blood specimens from anonymous healthy donors from City of Hope Blood Donor Center (Duarte, CA), with no identification regarding age, race, gender, or ethnicity. IRB#/REF#: 97071/075546
1. General Aseptic Practice
<ol>
	<li>Perform tissue culture experiments in designated laminar flow cabinets.</li>
	<li>Keep tissue culture medium and supplements under sterile conditions and filter using a 0.22-&#181;m filtration unit prior to use.</li>
	<li>Preserve prepared human HSCs in sterile tubes and keep on ice until injection.</li>
	<li>As a result of severe immune deficiency, handle NSG mice aseptically. Wear a disposable surgery gown, hair cap, face mask, shoe covers, and gloves to prevent contamination. Sanitize the bench surface, irradiation holder, and induction chamber for anesthesia with chlorine dioxide based sterilant (e.g., Clidox) before and after experiments.</li>
	<li>Apply petroleum-based eye ointment after retro-orbital bleeding to prevent dry eyes.</li>
	<li>Change to antibiotic-containing diet to prevent infection due to retro-orbital bleeding.</li>
</ol>
2. Handling HIV Virus, Infected Rodents, and Virus-containing Blood/Tissue Samples
CAUTION: HIV is a class 3 human pathogen; the handling rules must be followed exactly.
<ol>
	<li>Handle HIV virus-containing samples in a designated BSL2+/3 laboratory space. Lock virus-containing reagents securely in a secondary container during transportation. Disinfect the outer surface of all containers by thorough wiping with 10% bleach and isopropanol prior to transportation.</li>
	<li>Keep all virus-containing wastes in designated waste containers with 2-3 layers of biohazardous waste bags. Prior to waste disposal, disinfect by generously spraying the waste with iodine/ethoxylated nonylphenol solution (e.g., Wescodyne) and autoclave.</li>
	<li>Wear personal protective equipment: hair cap, face cover, anti-splash face shield, shoe covers, disposable surgery gown, and double-layer gloves.</li>
	<li>Handle infected rodents with extreme caution. Conduct injections and blood collections while mice are under anesthesia (Steps 5.1-5.2, 6.3-6.5, 7.3, and 8.1-8.2).</li>
</ol>
3. Isolation of Hematopoietic Stem Cells
<ol>
	<li>Prepare collagenase/dispase solution for tissue digestion.
	<ol>
		<li>Dissolve collagenase/dispase powder to make stock solution at a concentration of 100 mg/mL, and store collagenase/dispase stock solution in 150 &#181;L aliquots at -20 &#176;C.</li>
		<li>For working collagenase solution, dilute 150 &#181;L of collagenase/dispase stock with 15 mL of RPMI 1640 supplemented with 10% FCS and 1% penicillin/streptomycin. 
		NOTE: The final concentration of collagenase/dispase for tissue digestion is 1 mg/mL.</li>
	</ol>
	</li>
	<li>With a sterile razor blade, cut fetal liver tissue (16-24 weeks gestation) into small pieces (approximately 2-3 mm3 in size) followed by digestion with collagenase/dispase solution (1 mg/mL) for 30 minutes at room temperature. Adjust the volume of digestion solution so that all tissue pieces are fully submerged. Use the back end of the syringe plunger to gently grind the tissue sample to facilitate digestion.</li>
	<li>Pass the digestion mixture through a 70-&#181;m sterile nylon mesh filter to acquire a single cell suspension.</li>
	<li>Enrich for CD34+ HSCs using a MACS system per manufacturer&#39;s instruction.</li>
	<li>Count the viable percentage of enriched CD34+ HSCs using a hemacytometer28 and proceed to intrahepatic injection into neonatal NSG mice.</li>
	<li>Freeze the remaining enriched CD34+ HSCs in freezing media (e.g., CryoStor CS2) and preserve cells in a liquid nitrogen tank. Upon future use, recount the viable percentage of thawed CD34+ HSCs prior to injection. With the use of freezing media, post-thaw viability is between 80 to 90%.</li>
</ol>
4. Intrahepatic Injection of Human CD34+ HSCs in Neonatal NSG Mice
NOTE: Neonatal NSG mice 2-3 days from birth are most suitable for this procedure, as they are strong enough to endure irradiation at half-lethal dose, while young enough to have totally impaired immune systems. No anesthesia is required for the HSC injection.
<ol>
	<li>Place the whole litter of neonatal NSG mice (typically 5-10 mice, both genders) in a sterile pie-shaped irradiation cage and expose to a total dose of 200-250 cGy gamma-ray radiation from a Caesium-137 radiation source. Ensure that radiation dose is within the range, as significant weight loss or even death can be observed when NSG mice are exposed to high doses of irradiation.12 
	NOTE: Radiation is a health hazard, personal protection against radiation should be taken.</li>
	<li>Following irradiation, inject each neonatal NSG mouse with 5 x 105 viable human CD34+ HSCs using a syringe/needle setup (Figure 1). Directly inject cells into the liver.</li>
</ol>
5. Engraftment Validation Through Retro-Orbital Bleeding and Flow Cytometry Analysis
<ol>
	<li>At 10-12 weeks post-HSC injection, anesthetize mice using an isoflurane/oxygen inhalation apparatus. Adjust the oxygen flow to maintain isoflurane percentage at 4-5%. Anesthesia takes 3-5 minutes, depending on individual mouse. Properly anesthetized mice show a slow and deep breathing pattern, and no reaction to toe-pinching stimulation.</li>
	<li>Collect 50-100 &#181;L of peripheral blood from each mouse through retro-orbital sampling28. Store blood samples in K2EDTA or heparinized blood collection tubes to prevent coagulation. 
	NOTE: Blood collection tubes are required to have anticoagulant coating so that mouse PBMCs can be isolated from whole blood for flow cytometry analysis. EDTA is known to inhibit enzymatic reactions such as PCR and qRT-PCR; thus, if downstream enzymatic reactions are required, use a heparinized blood collection apparatus.</li>
	<li>Centrifuge blood samples at 2,000 x g for 20 minutes at 4 &#176;C to pellet blood cells.
	<ol>
		<li>Transfer the plasma supernatants to new microcentrifuge tubes after centrifugation and store at -80 &#176;C if cytokine analysis is required.</li>
		<li>Lyse the red blood cells (RBCs) within the blood cell pellet at room temperature for 10 minutes using Red Blood Cell Lysis Buffer (Table of Materials). 
		NOTE: If plasma samples are not required, directly lyse the whole blood with lysis solution without centrifugation.</li>
	</ol>
	</li>
	<li>Pellet remaining blood cells after RBC lysis at 300 x g for 5 minutes at 4 &#176;C; aspirate the supernatant. Wash the cell pellets with 0.01% BSA containing DPBS, centrifuge at 300 x g for 5 minutes at 4 &#176;C and aspirate supernatant. Repeat the washing step one more time.</li>
	<li>Block cells with 100 &#181;L of 1x blocking cocktail (Table 3 for recipe) for 20 minutes at 4 &#176;C.</li>
	<li>After blocking, directly add each antibody solution into the cell suspension at a concentration of 2 &#181;L/106 cells and incubate at 4 &#176;C for 30 minutes. Antibodies for engraftment validation are: anti-human CD45 (leukocytes, RRID: AB_2732068), anti-human CD3 (T-cells, RRID: AB_396896), anti-human CD4 (helper T-cells, RRID: AB_397037), anti-human CD8 (cytotoxic T-cells, RRID: AB_2722501), anti-human CD14 (monocytes, RRID: AB_10373536), and anti-human CD19 (B-cells, RRID: AB_10373382). For suggested flow panel, please see Table 4 and Table of Materials for catalog numbers, RRIDs and lot numbers. 
	NOTE: Antibody staining in blocking solution eliminates non-specific binding of the anti-human antibodies toward mouse surface markers, as several surface markers share homology between human and mouse.</li>
	<li>Isolate human PBMCs from healthy donors and prepare single-stained flow cytometry compensation controls using purified human PBMCs. Alternatively, use fluorescence-labeled microspheres as compensation controls29.</li>
	<li>Analyze the peripheral blood samples using a flow cytometer and quantify the percentage of human CD45+ cells, human CD3+ cells, human CD14+ cells, and human CD19+ cells from total peripheral blood cells.
	<ol>
		<li>For downstream HIV infection and latency studies, calculate the percentage of CD4+ T-cells and CD8+ T-cells within the CD3+ cells. 
		NOTE: Typically, a CD4:CD8 ratio between 1.5 and 2.5 is observed prior to HIV infection30.</li>
	</ol>
	</li>
</ol>
6. Analysis of HIV Infection of hu-NSG Mice and Plasma Viral Load Using qRT-PCR
<ol>
	<li>Propagate HIV BaL viral stock in human PBMCs from healthy donors, harvest at day 10 post-infection, and titrate using p24 ELISA kit31.</li>
	<li>Select hu-NSG mice with more than 20% human CD45+ cells in the peripheral blood for HIV infection.</li>
	<li>Anesthetize hu-NSG mice using an isoflurane/oxygen inhalation apparatus (Step 5.1).</li>
	<li>After confirming animal is anesthetized, inject HIV BaL virus at a dose of 200 ng of p24 per mouse through intraperitoneal route. 
	NOTE: Be extremely cautious with the needle, do not reuse needles, and discard immediately after use into designated sharp container. Disinfect the area of injection after virus administration.</li>
	<li>Three weeks post-infection, anesthetize hu-NSG mice and collect peripheral blood through retro-orbital bleeding using heparinized capillary tubes and collection tubes.</li>
	<li>Separate plasma and blood cells by centrifugation at 2,000 x g for 20 minutes.</li>
	<li>Lyse RBCs. Block and stain remaining blood cells with antibodies for flow cytometry analysis (Section 5.3-5.8). 
	NOTE: Flow cytometry analysis should focus on comparing CD4:CD8 ratio before and after infection. Significant decrease in CD4+ cell count is expected, as the CD4 antigen serves as a co-receptor for viral entry.</li>
	<li>Use plasma samples to analyze the HIV viral load using qRT-PCR. Isolate viral RNA from plasma samples using a viral RNA mini kit. Perform qRT-PCR with HIV-1 LTR-specific primers and probe sets (sequence details in Table 5), using manufacturer&#39;s protocol.</li>
</ol>
7. Oral Administration of cART and Validation of Viral Suppression (optional)
NOTE: This step is optional for investigations regarding HIV prognosis, virology, or infection-related pathophysiology during the acute infection phase. cART treatment of HIV-infected hu-NSG is used to recapitulate HIV latency among human patients receiving cART. Successfully HIV-infected hu-NSG mice are given cART for 4 weeks. The cART regimen consists of tenofovir disoproxil fumarate (TDF; 300 mg/capsule), emtricitabine (FTC; 200 mg/capsule), and raltegravir (RAL; 400 mg/capsule). The dose of cART for treating HIV-infected hu-NSG mice is adjusted according to body surface area (Table 1, Equation 1, Table 2)32.
<ol>
	<li>Calculate the amount of each medication required for each cage during one week of treatment, taking into consideration the volume of the water bottle, the number of mice in each cage, and an average daily water intake of 4 mL per mouse. 
	NOTE: The key point in this step is to ensure that each mouse acquires its daily dose within 4 mL of drinking water.</li>
	<li>Grind all three medications with adjusted doses into fine powder and dissolve the powder mixture in sweetened water (e.g., Medidrop Suralose). Change the water bottle every week with freshly dissolved cART cocktail supplied in sweetened water. 
	NOTE: The drug powder may not dissolve immediately, shake vigorously to achieve a homogeneous suspension before returning the bottle to the holding cage.</li>
	<li>Collect peripheral blood samples via retro-orbital bleeding every two weeks and analyze both the CD4:CD8 ratio using flow cytometry (Section 5.3-5.8) and the plasma viral load using qRT-PCR (Section 6.6). 
	NOTE: Typically after 4 weeks of treatment, the plasma viral load decreases to below the detection limit and a typical CD4:CD8 ratio is restored.</li>
</ol>
8. Validation of Viral Rebound upon cART Withdrawal (optional)
NOTE: This step is critical in validating the latency model, as viral rebound upon cART withdrawal provides direct evidence of a latency reservoir. It is also recommended to serve as a control experiment for therapeutic investigations on HIV rebound suppressants.
<ol>
	<li>Plan for cART withdrawal after plasma viral loads from peripheral blood samples are below the detection limit and the CD4:CD8 ratio is restored to a range between 1.5 and 2.5.</li>
	<li>Collect peripheral blood samples through retro-orbital bleeding every 2 weeks after cART withdrawal. Closely monitor the change in plasma viral loads (Section 6.6) as well as the CD4:CD8 ratio (Section 5.3-5.8).</li>
</ol>

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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+propagation+of+HIV-1+on+peripheral+blood+mononuclear+cells.">Isolation and propagation of HIV-1 on peripheral blood mononuclear cells.</a> Nature protocols. 3, 363 (2008).</li><li>Reagan-Shaw, S., Nihal, M., Ahmad, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dose+translation+from+animal+to+human+studies+revisited.">Dose translation from animal to human studies revisited.</a> FASEB journal: official publication of the Federation of American Societies for Experimental Biology. 22 (3), 659-661 (2008).</li><li>Han, Y., Wind-Rotolo, M., Yang, H. -. C., Siliciano, J. D., Siliciano, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+approaches+to+the+study+of+HIV-1+latency.">Experimental approaches to the study of HIV-1 latency.</a> Nature reviews. Microbiology. 5 (2), 95-106 (2007).</li><li>Marsden, M. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV+Latency+in+the+Humanized+BLT+Mouse.">HIV Latency in the Humanized BLT Mouse.</a> Journal of virology. 86 (1), 339-347 (2012).</li><li>Karpel, M. E., Boutwell, C. L., Allen, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BLT+humanized+mice+as+a+small+animal+model+of+HIV+infection.">BLT humanized mice as a small animal model of HIV infection.</a> Current opinion in virology. 13, 75-80 (2015).</li><li>Durand, C. M., Blankson, J. N., Siliciano, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developing+strategies+for+HIV-1+eradication.">Developing strategies for HIV-1 eradication.</a> Trends in immunology. 33 (11), 554-562 (2012).</li><li>Van Lint, C., Bouchat, S., Marcello, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV-1+transcription+and+latency:+an+update.">HIV-1 transcription and latency: an update.</a> Retrovirology. 10, 67 (2013).</li><li>Xu, L., Zhang, Y., Luo, G., Li, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+roles+of+stem+cell+memory+T+cells+in+hematological+malignancies.">The roles of stem cell memory T cells in hematological malignancies.</a> Journal of hematology &amp; oncology. 8, 113 (2015).</li><li>Chun, T. -. W., Moir, S., Fauci, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV+reservoirs+as+obstacles+and+opportunities+for+an+HIV+cure.">HIV reservoirs as obstacles and opportunities for an HIV cure.</a> Nature immunology. 16 (6), 584-589 (2015).</li><li>Redel, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HIV-1+regulation+of+latency+in+the+monocyte-macrophage+lineage+and+in+CD4++T+lymphocytes.">HIV-1 regulation of latency in the monocyte-macrophage lineage and in CD4+ T lymphocytes.</a> Journal of leukocyte biology. 87 (4), 575-588 (2010).</li><li>Laird, G. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+Quantification+of+the+Latent+Reservoir+for+HIV-1+Using+a+Viral+Outgrowth+Assay.">Rapid Quantification of the Latent Reservoir for HIV-1 Using a Viral Outgrowth Assay.</a> PLoS pathogens. 9 (5), e1003398 (2013).</li></ol>

The authors disclose no conflicts of interest.

Immunocompromised mice engrafted with human cells/tissue present human-like physiological characteristics and are a tremendous value for pathology, pathophysiology, and immunology studies concerning human-specific diseases. Among multiple strains of immunocompromised mice, the NOD.Cg-PrkdcscidIl2rgtm1Wji (NSG) model is the most immunodeficient due to its lack of both innate and adaptive immunity, as well as ablated mouse-specific cytokine signaling3,12,19. Therefore, NSG mice have been extensively utilized in the humanization process, and it is well established that human cells repopulate in the murine peripheral blood, lymphoid and myeloid tissues, and that the mice exhibit appropriate human immune responses to infectious stimulations such as HIV27,33.
Due to the host restriction of HIV, preclinical animal studies of HIV virology and infection prognosis were previously limited to non-human primates infected with simian immunodeficiency virus (SIV, the non-human primate version of HIV)3. Scientific advancements in stem cell research and the generation of NSG mice have opened up the possibility of conducting HIV research on small murine animals with lower cost and faster experimental turnover. Currently, NSG humanization can be achieved through transplantation of 1) fetal tissues and human HSCs (BLT model), 2) human PBMCs (PBL model), and 3) human HSCs (SRC model). The BLT model offers the highest engraftment efficiency as well as comprehensive development of both lymphoid and myeloid functions34,35, but is technically demanding. The PBL model is the most convenient to establish but has a short experimental window upon engraftment resulting from GVHD; additionally it only offers decent peripheral T-cell responses and lacks lymphoid and myeloid development. For these reasons, we employed the SRC model in this protocol, with adaptations to meet the requirements for HIV investigations. The hu-NSG model is completely devoid of immune function and efficient at bone marrow homing upon radiation and transplantation; furthermore, it allows viral challenge and subsequent investigations at a younger age, avoiding the development of age-related pathological problems known to the NOD strain background. Although T-cells in the hu-NSG model are educated in a mouse thymic environment and are only H2-restricted, multiple, if not all, subsets of human immune cells can develop in and colonize mouse lymphoid and myeloid organs. Noticeably, gut-associated lymphoid tissue of the hu-NSG model is also reconstituted with human immune cells; thus, this model could potentially support HIV mucosal transmission, similar to the BLT model22,23.
One of the major obstacles to eradicating HIV is the existence of a latency reservoir among patients treated with suppressive cART33,36,37,38,39. Latently infected cells remain quiescent, and contribute to HIV viral rebound upon cART withdrawal. Latency reservoirs are anatomically located in the liver, spleen, brain, and other lymphoid tissues, and are mainly composed of memory CD4+ T-cells36,40,41. As reported by our group, the hu-NSG model fully supports development of the T-cell lineage, making it suitable for pathological modeling of HIV latency. We showed this model is highly susceptible to viral infection and subsequently to the cART regimen via oral administration. Dramatic viral rebound occurs immediately upon cART withdrawal, which fully supports the existence of a latency reservoir. Latently infected memory CD4+ T-cells can be isolated from the lymphoid organs of HIV-infected hu-NSG during cART, and viral outgrowth assays recapitulate viral rebound ex vivo41. The hu-NSG model and the HIV infection/cART regimen described in this protocol thus have broad applications in fields related to HIV virology, infection prognosis, latency pathophysiology, and antiretroviral therapeutics development.
The hu-NSG mouse model in this protocol requires irradiation and intrahepatic injection of HSCs at day 2-3 after birth; therefore, in-house breeding and specific housing conditions are required. Although neonatal HSC transplantation generally yields high engraftment efficiencies, in some cases severe GVHD can occur. In some cases, a significant decrease in peripheral CD45+ cell count can be observed upon infection, and in extreme conditions, peripheral blood CD45+ depletion can be observed; therefore, blood collection and flow cytometry analysis can be challenging. One of the major limitations of this hu-NSG mouse model lies within the chimeric nature of its T-cells. T-cells in the hu-NSG mouse model are educated within the mouse thymic environment and are H2-restricted instead of being HLA-restricted; therefore, full recapitulation of the dynamic changes of T-cell subsets upon infection is less likely. Further, although the hu-NSG mouse model exhibits good susceptibility to HIV-1 infection, the observed plasma viral load can be several-fold lower than in the BLT model, possibly due to incomprehensive reconstitution of human lymphoid and myeloid functions.
In summary, the hu-NSG mouse depicted in this protocol offers an easy and efficient methodology for generating a humanized mouse model for HIV virology and latency studies, as an alternative to the BLT model. Despite its limitations in comprehensive lymphoid and myeloid development, the hu-NSG model has been proven susceptible to infection and responsive to cART treatment or other therapeutics22,23,24. The latency pathology model established according to this protocol recapitulates HIV viral rebound in vivo and latently infected memory CD4+ T-cells can be further isolated for additional investigation.

Because establishing suitable animal models for human diseases is key to finding a cure, appropriate animals models have long been pursued and improved over time. Multiple strains of immunocompromised murine models have been developed that permit the engraftment of human cells and/or tissues and the subsequent execution of humanized functions1,2. Such humanized mouse models are critical for investigations of human-specific diseases3,4,5.
Acquired immune deficiency syndrome (AIDS) resulting from infection with human immunodeficiency virus (HIV) is one example. Prior to the establishment of humanized mouse models, ethical and technical limitations confined HIV/AIDS preclinical animal studies to non-human primates3. However, the high expenses and requirements for specialized care for such animal hinder HIV/AIDS studies in typical academic settings. HIV primarily infects human CD4+ T-cells and impacts the development and immune responses of other human immune cells such as B-cells, macrophages, and dendritic cells6; therefore, small animal models transplanted with functional human immune systems are in high demand.
A breakthrough came in 1988, when CB17-scid mice with a Prkdcscid mutation were developed and showed successful engraftment of the human immune system1. The Prkdcscid mutation results in defective T- and B-cell functions and an ablated adaptive immune system in mice, thereby enabling the engraftment of human peripheral blood mononuclear cells (PBMCs), hematopoietic stem cells (HSCs), and fetal hematopoietic tissues7,8. Nonetheless, low levels of engraftment are frequently observed in this model; possible causes are 1) residual innate immune activity modulated via natural killer (NK)-cells and 2) the late-stage development of mouse T- and B-cells (leakiness)5. The subsequent development of the non-obese diabetic (NOD)-scid mouse model achieved dramatic down-regulation of NK-cell activity; thus, it is able to support a higher level and more sustainable engraftment of human immune system components9. To further suppress or impede development of innate immunity, mouse models bearing truncation or total knockout of the interleukin-2 receptor &#947;-chain (Il2rg) in the (NOD)-scid background were established. Il2rg, also known as common cytokine-receptor &#947;-chain, is an indispensable component of various cytokine receptors10,11,12,13. Strains such as NOD.Cg-PrkdcscidIl2rgtm1Wji (NSG) and NODShi.Cg-PrkdcscidIl2rgtm1Sug (NOG) present robust disruption of mouse cytokine signaling and complete ablation of NK-cell development, in addition to severe impairment of adaptive immunity14,15,16.
Three humanized mouse models bearing a scid mutation and Il2rg knockout are frequently employed in HIV/AIDS research: the BLT (Bone marrow/Liver/Thymus) model, the PBL (Peripheral Blood Leukocyte) model, and the SRC (SCID Repopulating Cell) model3. The BLT model is created via surgical transplantation of human fetal liver and thymus under the mouse kidney capsule accompanied with intravenous injection of fetal liver HSCs3,17,18. The BLT mouse model offers high engraftment efficacy, development of human hematopoietic cells in all lineages, and establishment of a strong human immune system; additionally, T-cells are educated in a human autologous thymus and exhibit HLA-restricted immune responses4,5,17,19. However, the requirement for surgical procedures remains the major drawback of the BLT model. The PBL mouse model is established by intravenous injection with human peripheral lymphoid cells. The PBL model offers convenience and yields successful T-cell engraftment, but its application is limited due to insufficient B-cell and myeloid cell engraftment, low engraftment levels overall, and the onset of severe graft-versus-host disease (GVHD)3,20. The SRC mouse model is established through injection of human HSCs into newborn or young adult SCID mice. It exhibits average engraftment efficiency above 25% (assessed as peripheral blood CD45 percentage) and supports the multiple-lineage development of injected HSCs and the elaboration of an innate human immune system. However, the limitation of the SRC model is that the T-cell response is mouse H2-restricted instead of human HLA-restricted14,21.
The SRC mouse model is considered a facile and reliable model for preclinical HIV/AIDS small animal studies, exemplified by the consistent engraftment of a human immune system and successful hematopoietic development. We previously reported the establishment of a NSG Hu-SRC-SCID (hu-NSG) mouse model and described its application in HIV replication and latency studies22,23,24. This hu-NSG mouse model exhibits high levels of bone marrow homing, susceptibility to HIV infection, and recapitulation of HIV infection and pathogenesis. Additionally, the hu-NSG mouse model responds appropriately to combinatorial antiretroviral therapy (cART) and recapitulates plasma viral rebound upon cART withdrawal, confirming the establishment of an HIV latency reservoir25,26,27. This HIV latency reservoir is further substantiated by the production of replication-competent HIV viruses ex vivo induced by human resting CD4+ T-cells isolated from infected and cART-treated hu-NSG mice.
Herein, we describe the detailed protocol for establishment of the hu-NSG mouse model from neonatal NSG mice, including procedures related to HIV infection and cART treatment for latency development. We expect this protocol to offer a new set of approaches in HIV animal studies regarding HIV virology, latency, and treatment.

<table>
	<tbody>
		<tr>
			<td>CD34 MicroBead Kit, human</td>
			<td>MiltenyiBiotec</td>
			<td>130-046-703</td>
			<td></td>
		</tr>
		<tr>
			<td>CryoStor CS2</td>
			<td>Stemcell Technologies</td>
			<td>07932</td>
			<td></td>
		</tr>
		<tr>
			<td>NOD.Cg-PrkdcscidIl2rgtm1Wji </td>
			<td>The Jackson Laboratory</td>
			<td>005557</td>
			<td>Order breeders instead of experimental mice</td>
		</tr>
		<tr>
			<td>IsoFlo</td>
			<td>Patterson Veterinary</td>
			<td>07-806-3204</td>
			<td>Order through animal facility, restricted item</td>
		</tr>
		<tr>
			<td>Clidox disinfectant</td>
			<td>Fisher Sicentific</td>
			<td>NC9189926</td>
			<td></td>
		</tr>
		<tr>
			<td>Wescodyne</td>
			<td>Fisher Sicentific</td>
			<td>19-818-419</td>
			<td></td>
		</tr>
		<tr>
			<td>Hamilton 80508 syringe/needle</td>
			<td>Hamilton</td>
			<td>80508</td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Blood collection tube (K2EDTA)</td>
			<td>BD Bioscience</td>
			<td>367843</td>
			<td></td>
		</tr>
		<tr>
			<td>Blood collection tube (Heparin)</td>
			<td>BD Bioscience</td>
			<td>365965</td>
			<td></td>
		</tr>
		<tr>
			<td>Capillary tube (Heparinized)</td>
			<td>Fisher Sicentific</td>
			<td>22-362574</td>
			<td></td>
		</tr>
		<tr>
			<td>Red Blood Cell Lysis Buffer</td>
			<td>Sigma Aldrich</td>
			<td>11814389001</td>
			<td></td>
		</tr>
		<tr>
			<td>QIAamp Viral RNA mini kit</td>
			<td>Qiagen</td>
			<td>52906</td>
			<td></td>
		</tr>
		<tr>
			<td>TaqMan Fast VIrus 1-step Master Mix</td>
			<td>Thermofisher</td>
			<td>4444434</td>
			<td></td>
		</tr>
		<tr>
			<td>HIV-1 P24 ELISA (5 Plate kit)</td>
			<td>PerkinElmer</td>
			<td>NEK050B001KT</td>
			<td></td>
		</tr>
		<tr>
			<td>IgG from human serum</td>
			<td>Sigma Aldrich</td>
			<td>I4506-100MG</td>
			<td></td>
		</tr>
		<tr>
			<td>IgG from mouse serum</td>
			<td>Sigma Aldrich</td>
			<td>I5381-10MG</td>
			<td></td>
		</tr>
		<tr>
			<td>BB515 Mouse Anti-Human CD45 (clone HI30)</td>
			<td>BD Biosciences</td>
			<td>564586</td>
			<td>RRID: AB_2732068, LOT 6347696</td>
		</tr>
		<tr>
			<td>PE-Cy7 Mouse Anti-Human CD3 (Clone SK7)</td>
			<td>BD Biosciences</td>
			<td>557851</td>
			<td>RRID: AB_396896, LOT 6021877</td>
		</tr>
		<tr>
			<td>Pacific Blue Mouse Anti-Human CD4 (Clone RPA-T4)</td>
			<td>BD Biosciences</td>
			<td>558116</td>
			<td>RRID: AB_397037, LOT 6224744</td>
		</tr>
		<tr>
			<td>BUV395 Mouse Anti-Human CD8 (Clone RPA-T8)</td>
			<td>BD Biosciences</td>
			<td>563795</td>
			<td>RRID: AB_2722501, LOT 6210668</td>
		</tr>
		<tr>
			<td>APC-Alexa Fluor 750 Mouse Anti-Human CD14 (TuK4)</td>
			<td>ThermoFisher</td>
			<td>MHCD1427</td>
			<td>RRID: AB_10373536, LOT 1684947A</td>
		</tr>
		<tr>
			<td>PE Mouse Anti-Human CD19 (SJ25-C1)</td>
			<td>ThermoFisher</td>
			<td>MHCD1904</td>
			<td>RRID: AB_10373382, LOT 1725304B</td>
		</tr>
	</tbody>
</table>

humanized nod/scid/il2r&#947;null (hu-nsg) mouse model for hiv replication and latency studies

Ethical regulations and technical challenges for research in human pathology, immunology, and therapeutic development have placed small animal models in high demand. With a close genetic and behavioral resemblance to humans, small animals such as the mouse are good candidates for human disease models, through which human-like symptoms and responses can be recapitulated. Further, the mouse genetic background can be altered to accommodate diverse demands. The NOD/SCID/IL2r&#947;null (NSG) mouse is one of the most widely used immunocompromised mouse strains; it allows engraftment with human hematopoietic stem cells and/or human tissues and the subsequent development of a functional human immune system. This is a critical milestone in understanding the prognosis and pathophysiology of human-specific diseases such as HIV/AIDS and aiding the search for a cure. Herein, we report a detailed protocol for generating a humanized NSG mouse model (hu-NSG) by hematopoietic stem cell transplantation into a radiation-conditioned neonatal NSG mouse. The hu-NSG mouse model shows multi-lineage development of transplanted human stem cells and susceptibility to HIV-1 viral infection. It also recapitulates key biological characteristics in response to combinatorial antiretroviral therapy (cART).

Flow cytometry analysis is frequently performed to validate the purity of isolated HSCs, evaluate engraftment levels, profile immune responses to viral infection, and survey cART efficacy. A typical antibody panel contains 4-6 individual fluorescently labeled antibodies; thus, a flow cytometer with multiple lasers and a wide selection of filters is crucial for achieving accurate results.
For initial engraftment validation, the human CD45+ cell count can range from 20% to 80%, and subsets of human leukocytes should appear as discrete populations on the flow dot-plot (Figure 2). The ratio of CD4:CD8 stays between 1.5 and 2.5 for a healthy individual; significant CD4+ depletion is typically observed upon viral infection, yielding a lower ratio of CD4:CD8; and restoration of the healthy ratio is observed upon cART treatment (Figure 3).
qRT-PCR gives a detection limit of 40 RNA copies/mL of plasma; proper dilutions are required prior to the experiment. Plasma viral loads detected using qRT-PCR throughout the course of the infection and cART regimen can be plotted and used to evaluate the efficiency of infection and cART (Figure 4).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58255/58255fig1.jpg" /> 
Figure 1. Syringe/needle setup used for intrahepatic injection. 
The custom-made Hamilton 80508 syringe/needle setup includes a 30-gauge, 51-mm-long needle with a beveled edge and an attached 50-&#181;L glass syringe. Maximum injection volume in this procedure is 25 &#181;L. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58255/58255fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58255/58255fig2.jpg" /> 
Figure 2. Flow cytometry data represent successful engraftment and the developments of lymphoid and myeloid cells in the peripheral blood. 
Successfully prepared peripheral blood samples should have discrete population separations, and a well-engrafted hu-NSG mouse should have T-cell, B-cell and monocyte positive populations presented in the peripheral blood. A CD4:CD8 chart is recommended for ratio calculation. a) Successful engraftment showed more than 25% CD45+ human leukocytes in the peripheral blood; discrete population of b) B-cells, c) monocytes, d) T-cells among human CD45+ leukocyte; e) CD4+ helper T-cells and f) CD8+ cytotoxic T-cells are well separated, and g) yields a ratio between 1.5 to 2.5 in this uninfected hu-NSG. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58255/58255fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58255/58255fig3.jpg" /> 
Figure 3. CD4+ cell count changes throughout the course of viral infection, cART and cART withdraw. 
As infection progresses, the CD4:CD8 ratio decreases from 1.5-2.5 to &#62;1.0, CD4:CD8 ratio has been served as a clinical parameter in evaluating HIV prognosis as well as treatment efficacies. a) Representative flow data indicating the change in CD4:CD8 ratios during the experimental course; b) Comparison trend chart indicating the effectiveness of cART, which can be identified as restored percentage of CD4+ T cells. Detection of CD4+ T cell count by flow cytometry. N: number of tested mice = 6; Error bars: means &#177; SEM. * p &#60;0.05, ** p &#60;0.01, ***p &#60;0.001, **** p &#60;0.0001, ns: no significant different. Two-way ANOVA analysis is employed.&#160;Figure is reprinted with permission22.&#160;<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58255/58255fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58255/58255fig4.jpg" /> 
Figure 4. Changes of serum viral RNA copy numbers throughout the course of viral infection, cART and cART withdraw 
Detection of plasma viremia in the HIV-infected hu-NSG mice by qRT-PCR. The shaded area indicates the time period during which the mice received cART (from Day 28 to Day 70 as shown). The limit of detection (indicated by the dashed line) of the PCR assay is (~110-160 RNA copies/mL) in 50 to 80 &#181;L of plasma obtained through the tail vein. Star (*) indicates viral RNA not detected in cART treated animals at Day 56. Serum viral RNA copy number analyzed from peripheral blood samples serves as direct evidence concerning the degree of viral infection. It should be in the agreement with the CD4 flow analysis. N: number of tested mice = 6; Error bars: means &#177; SEM. * p &#60;0.05, ** p &#60;0.01, *** p &#60;0.001, **** p &#60;0.0001, ns: no significant different. Two-way ANOVA analysis is employed.&#160;Figure is reprinted with permission22.&#160;<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58255/58255fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Equation" src="/files/ftp_upload/58255/58255eq1.jpg" /> 
Equation 1. Dose translation based on body surface area (BSA). 
Equation for translating human dose to dosing against small experimental animals. The Km factor can be found in Table 2.
<table border="0" cellpadding="0" cellspacing="0" width="418">
	<colgroup>
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:219px;">Medication</td>
			<td style="width:199px;">Daily Dose (mg)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tenofovir disoproxil fumarate</td>
			<td>300</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Emtricitabine</td>
			<td>200</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Raltegravir</td>
			<td>800</td>
		</tr>
	</tbody>
</table>
Table 1. Daily dose of individual medication in cART regimen
<table border="0" cellpadding="0" cellspacing="0" width="401">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="24">
			<td height="24" style="height:24px;width:103px;">Species</td>
			<td style="width:95px;">Weight (kg)</td>
			<td style="width:99px;">BSA (m2)</td>
			<td style="width:105px;">Km factor</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Human&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Adult</td>
			<td>60</td>
			<td>1.6</td>
			<td>37</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Child</td>
			<td>20</td>
			<td>0.8</td>
			<td>25</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Mouse</td>
			<td>0.02</td>
			<td>0.0007</td>
			<td>3</td>
		</tr>
	</tbody>
</table>
Table 2. Weight, BSA and Km factor chart for dose conversion
<table border="0" cellpadding="0" cellspacing="0" width="387">
	<colgroup>
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:132px;">Reagent</td>
			<td style="width:113px;">Volume (&#956;l)*</td>
			<td style="width:143px;">Final Concentration</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">0.01% BSA in PBS</td>
			<td>98</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">10 mg/ml human IgG</td>
			<td>1</td>
			<td>100 &#956;g/ml</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">10 mg/ml mouse IgG</td>
			<td>1</td>
			<td>100 &#956;g/ml</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;"></td>
			<td>100</td>
			<td></td>
		</tr>
		<tr height="39">
			<td colspan="3" height="39" style="height:39px;width:388px;">* Recipe is for one cell sample blocked in 100 &#956;l blocking cocktail. Adjust the volume accordingly with sample numbers.</td>
		</tr>
	</tbody>
</table>
Table 3. Blocking cocktail for isolated blood cells
<table border="0" cellpadding="0" cellspacing="0" width="395">
	<colgroup>
		<col />
		<col />
		<col span="2" />
	</colgroup>
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:95px;">Antibody</td>
			<td style="width:101px;">Fluorophore</td>
			<td style="width:100px;">Ex. Max</td>
			<td style="width:100px;">Em. Max</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CD45</td>
			<td>BB515</td>
			<td>490 nm</td>
			<td>515 nm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CD3</td>
			<td>PE-Cy7</td>
			<td>496 nm</td>
			<td>785 nm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CD4</td>
			<td>Pacific Blue</td>
			<td>401 nm</td>
			<td>452 nm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CD8</td>
			<td>BUV395</td>
			<td>348 nm</td>
			<td>395 nm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CD14</td>
			<td>APC-Alexa 750</td>
			<td>650 nm</td>
			<td>774 nm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">CD19</td>
			<td>PE</td>
			<td>496 nm</td>
			<td>578 nm</td>
		</tr>
	</tbody>
</table>
Table 4. Suggested multi-color flow panel
<table border="0" cellpadding="0" cellspacing="0" width="429">
	<colgroup>
		<col span="2" />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="20">
			<td colspan="2" height="20" style="height:20px;width:128px;">Forward Primer</td>
			<td colspan="3" style="width:301px;">5&#39;-GCCTCAATAAAGCTTGCCTTG -3&#39;</td>
		</tr>
		<tr height="20">
			<td colspan="2" height="20" style="height:20px;">Reverse Primer</td>
			<td colspan="3">5&#39;-GGCGCCACTGCTAGAGATTTT -3&#39;</td>
		</tr>
		<tr height="20">
			<td colspan="2" height="20" style="height:20px;">Probe*</td>
			<td colspan="3">5&#39;-AAGTAGTGTGTGCCCGTCTGTTAGTGTTGACT -3&#39;</td>
		</tr>
		<tr height="20">
			<td colspan="5" height="20" style="height:20px;">* 5&#39;-FAM, 3&#39;-Black Hole Quenche 1</td>
		</tr>
	</tbody>
</table>
Table 5. HIV-1 LTR Primers and probe

Watch this Scientific Journal Video about Humanized NOD/SCID/IL2rÃŽÂ³null hu-NSG Mouse Model for HIV Replication and Latency Studies at JoVE.com

Humanized NOD/SCID/IL2r&#947;null (hu-NSG) Mouse Model for HIV Replication and Latency Studies

This protocol provides a method to establish humanized mice (hu-NSG) via intrahepatic injection of human hematopoietic stem cells into radiation-conditioned neonatal NSG mice. The hu-NSG mouse is susceptible to HIV infection and combinatorial antiretroviral therapy (cART) and serves as a suitable pathophysiological model for HIV replication and latency investigations.

Ethical regulations and technical challenges for research in human pathology, immunology, and therapeutic development have placed small animal models in ...

humanized-nodscidil2rnull-hu-nsg-mouse-model-for-hiv-replication

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

15.5K Views.  Beckman Research Institute of City of Hope. This protocol provides a method to establish humanized mice (hu-NSG) via intrahepatic injection of human hematopoietic stem cells into radiation-conditioned neonatal NSG mice. The hu-NSG mouse is susceptible to HIV infection and combinatorial antiretroviral therapy (cART) and serves as a suitable pathophysiological model for HIV replication and latency investigations.

Video: Humanized NOD/SCID/IL2rγnull (hu-NSG) Mouse Model for HIV Replication and Latency Studies

Genotypic Inference of HIV-1 Tropism Using Population-based Sequencing of V3

Background: Prior to receiving a drug from CCR5-antagonist class in HIV therapy, a patient must undergo an HIV tropism test to confirm that his or her viral population uses the CCR5 coreceptor for cellular entry, and not an alternative coreceptor. One approach to tropism testing is to examine the sequence of the V3 region of the HIV envelope, which interacts with the coreceptor.
Methods: Viral RNA is extracted from blood plasma. The V3 region is amplified in triplicate with nested reverse transcriptase-PCR. The amplifications are then sequenced and analyzed using the software, RE_Call. Sequences are then submitted to a bioinformatic algorithm such as geno2pheno to infer viral tropism from the V3 region. Sequences are inferred to be non-R5 if their geno2pheno false positive rate falls below 5.75%. If any one of the three sequences from a sample is inferred to be non-R5, the patient is unlikely to respond to a CCR5-antagonist.

HIV tropism can be inferred from the V3 region of the viral envelope. V3 is PCR amplified in triplicate using nested RT-PCR, sequenced, and interpreted using bioinformatic software. Samples with with 1 or more sequence(s) with low g2P scores are classified as non-R5 virus.

Background: Prior to receiving a drug from CCR5-antagonist class in HIV therapy, a patient must undergo an HIV tropism test to confirm that his or her ...

Dissecting Host-virus Interaction in Lytic Replication of a Model Herpesvirus

In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral cytokine production1,2. In order to colonize the host, viruses are obligate to evade host antiviral responses and manipulate signaling pathways. Unraveling the host-virus interaction will shed light on the development of novel therapeutic strategies against viral infection.
Murine &gamma;HV68 is closely related to human oncogenic Kaposi's sarcoma-associated herpesvirus and Epsten-Barr virus3,4. &gamma;HV68 infection in laboratory mice provides a tractable small animal model to examine the entire course of host responses and viral infection in vivo, which are not available for human herpesviruses. In this protocol, we present a panel of methods for phenotypic characterization and molecular dissection of host signaling components in &gamma;HV68 lytic replication both in vivo and ex vivo. The availability of genetically modified mouse strains permits the interrogation of the roles of host signaling pathways during &gamma;HV68 acute infection in vivo. Additionally, mouse embryonic fibroblasts (MEFs) isolated from these deficient mouse strains can be used to further dissect roles of these molecules during &gamma;HV68 lytic replication ex vivo.
Using virological and molecular biology assays, we can pinpoint the molecular mechanism of host-virus interactions and identify host and viral genes essential for viral lytic replication. Finally, a bacterial artificial chromosome (BAC) system facilitates the introduction of mutations into the viral factor(s) that specifically interrupt the host-virus interaction. Recombinant &gamma;HV68 carrying these mutations can be used to recapitulate the phenotypes of &gamma;HV68 lytic replication in MEFs deficient in key host signaling components. This protocol offers an excellent strategy to interrogate host-pathogen interaction at multiple levels of intervention in vivo and ex vivo.
Recently, we have discovered that &gamma;HV68 usurps an innate immune signaling pathway to promote viral lytic replication5. Specifically, &gamma;HV68 de novo infection activates the immune kinase IKK&beta; and activated IKK&beta; phosphorylates the master viral transcription factor, replication and transactivator (RTA), to promote viral transcriptional activation. In doing so, &gamma;HV68 efficiently couples its transcriptional activation to host innate immune activation, thereby facilitating viral transcription and lytic replication. This study provides an excellent example that can be applied to other viruses to interrogate host-virus interaction.

We describe a protocol to identify key roles of host signaling molecules in lytic replication of a model herpesvirus, gamma herpesvirus 68 (&gamma;HV68). Utilizing genetically modified mouse strains and embryonic fibroblasts for &gamma;HV68 lytic replication, the protocol permits both phenotypic characterization and molecular interrogation of virus-host interactions in viral lytic replication.

In response to viral infection, a host develops various defensive responses, such as activating innate immune signaling pathways that lead to antiviral ...

Using the BLT Humanized Mouse as a Stem Cell based Gene Therapy Tumor Model

Small animal models such as mice have been extensively used to study human disease and to develop new therapeutic interventions. Despite the wealth of information gained from these studies, the unique characteristics of mouse immunity as well as the species specificity of viral diseases such as human immunodeficiency virus (HIV) infection led to the development of humanized mouse models. The earlier models involved the use of C. B 17 scid/scid mice and the transplantation of human fetal thymus and fetal liver termed thy/liv (SCID-hu) 1, 2 or the adoptive transfer of human peripheral blood leukocytes (SCID-huPBL) 3. Both models were mainly utilized for the study of HIV infection.
One of the main limitations of both of these models was the lack of stable reconstitution of human immune cells in the periphery to make them a more physiologically relevant model to study HIV disease. To this end, the BLT humanized mouse model was developed. BLT stands for bone marrow/liver/thymus. In this model, 6 to 8 week old NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) immunocompromised mice receive the thy/liv implant as in the SCID-hu mouse model only to be followed by a second human hematopoietic stem cell transplant 4. The advantage of this system is the full reconstitution of the human immune system in the periphery. This model has been used to study HIV infection and latency 5-8.
We have generated a modified version of this model in which we use genetically modified human hematopoietic stem cells (hHSC) to construct the thy/liv implant followed by injection of transduced autologous hHSC 7, 9. This approach results in the generation of genetically modified lineages. More importantly, we adapted this system to examine the potential of generating functional cytotoxic T cells (CTL) expressing a melanoma specific T cell receptor. Using this model we were able to assess the functionality of our transgenic CTL utilizing live positron emission tomography (PET) imaging to determine tumor regression (9).
The goal of this protocol is to describe the process of generating these transgenic mice and assessing in vivo efficacy using live PET imaging. As a note, since we use human tissues and lentiviral vectors, our facilities conform to CDC NIH guidelines for Biosafety Level 2 (BSL2) with special precautions (BSL2+). In addition, the NSG mice are severely immunocompromised thus, their housing and maintenance must conform to the highest health standards (<a href="http://jaxmice.jax.org/research/immunology/005557-housing.html" target="_blank">http://jaxmice.jax.org/research/immunology/005557-housing.html</a>).

The generation and characterization of tumor specific T cells using humanized mice is described here. Human thymic tissue and genetically modified human hematopoietic stem cells are transplanted into immunocompromised mice. This results in the reconstitution of an engineered human immune system allowing for in vivo examination of anti-tumor immune responses.

Small animal models such as mice have been extensively used to study human  disease and to develop new therapeutic interventions. Despite the wealth of  ...

Humanized Mouse Model to Study Bacterial Infections Targeting the Microvasculature

Neisseria meningitidis causes a severe, frequently fatal sepsis when it enters the human blood stream. Infection leads to extensive damage of the blood vessels resulting in vascular leak, the development of purpuric rashes and eventual tissue necrosis. Studying the pathogenesis of this infection was previously limited by the human specificity of the bacteria, which makes in vivo models difficult. In this protocol, we describe a humanized model for this infection in which human skin, containing dermal microvessels, is grafted onto immunocompromised mice. These vessels anastomose with the mouse circulation while maintaining their human characteristics. Once introduced into this model, N. meningitidis adhere exclusively to the human vessels, resulting in extensive vascular damage, inflammation and in some cases the development of purpuric rash. This protocol describes the grafting, infection and evaluation steps of this model in the context of N. meningitidis infection. The technique may be applied to numerous human specific pathogens that infect the blood stream.

Neisseria meningitidis is a human specific pathogen that infects blood vessels. In this protocol human microvessels are introduced into a mouse by grafting human skin onto immunocompromised mice. Bacteria adhere extensively to the human vessels, leading to vascular damage and development of the purpuric rash typically observed in human cases.

Neisseria meningitidis causes a severe, frequently fatal sepsis when it enters the human blood stream. Infection leads to extensive damage of the blood ...

Pairwise Growth Competition Assay for Determining the Replication Fitness of Human Immunodeficiency Viruses

In vitro fitness assays are essential tools for determining viral replication fitness for viruses such as HIV-1. Various measurements have been used to extrapolate viral replication fitness, ranging from the number of viral particles per infectious unit, growth rate in cell culture, and relative fitness derived from multiple-cycle growth competition assays. Growth competition assays provide a particularly sensitive measurement of fitness since the viruses are competing for cellular targets under identical growth conditions. There are several experimental factors to consider when conducting growth competition assays, including the multiplicity of infection (MOI), sampling times, and viral detection and fitness calculation methods. Each factor can affect the end result and hence must be considered carefully during the experimental design. The protocol presented here includes steps from constructing a new recombinant HIV-1 clone to performing growth competition assays and analyzing the experimental results. This protocol utilizes experimental parameter values previously shown to yield consistent and robust results. Alternatives are discussed, as some parameters need to be adjusted according to the cell type and viruses being studied. The protocol contains two alternative viral detection methods to provide flexibility as the availability of instruments, reagents and expertise varies between laboratories.

Growth competition between nearly isogenic viruses provides a sensitive measurement for determining relative replication fitness. The protocols described here include the construction of recombinant HIV-1 clones, virus propagation and growth competition and analysis methods optimized to yield sensitive and consistent results.

In vitro fitness assays are essential tools for determining viral replication fitness for viruses such as HIV-1. Various measurements have been used to ...

Measurement of In Vitro Integration Activity of HIV-1 Preintegration Complexes

HIV-1 envelope proteins engage cognate receptors on the target cell surface, which leads to viral-cell membrane fusion followed by the release of the viral capsid (CA) core into the cytoplasm. Subsequently, the viral Reverse Transcriptase (RT), as part of a namesake nucleoprotein complex termed the Reverse Transcription Complex (RTC), converts the viral single-stranded RNA genome into a double-stranded DNA copy (vDNA). This leads to the biogenesis of another nucleoprotein complex, termed the pre-integration complex (PIC), composed of the vDNA and associated virus proteins and host factors. The PIC-associated viral integrase (IN) orchestrates the integration of the vDNA into the host chromosomal DNA in a temporally and spatially regulated two-step process. First, the IN processes the 3&#39; ends of the vDNA in the cytoplasm and, second, after the PIC traffics to the nucleus, it mediates integration of the processed vDNA into the chromosomal DNA. The PICs isolated from target cells acutely infected with HIV-1 are functional in vitro, as they are competent to integrate the associated vDNA into an exogenously added heterologous target DNA. Such PIC-based in vitro integration assays have significantly contributed to delineating the mechanistic details of retroviral integration and to discovering IN inhibitors. In this report, we elaborate upon an updated HIV-1 PIC assay that employs a nested real-time quantitative Polymerase Chain Reaction (qPCR)-based strategy for measuring the in vitro integration activity of isolated native PICs.

Measurement of In Vitro Integration Activity of HIV-1 Preintegration Complexes

This report describes an in vitro assay for measuring the human immunodeficiency virus type 1 (HIV-1) preintegration complex (PIC)-associated integration activity in the cytoplasmic extracts of acutely infected cells. The integration of PIC-associated HIV-1 DNA into heterologous target DNA is quantified by using a nested real-time polymerase chain reaction strategy.

HIV-1 envelope proteins engage cognate receptors on the target cell surface, which leads to viral-cell membrane fusion followed by the release of the ...

Influenza A Virus Studies in a Mouse Model of Infection

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone considering direct medical and hospitalization expenses and work absenteeism2. Animal models are crucial in Influenza A virus (IAV) studies to evaluate viral pathogenesis, host-pathogen interactions, immune responses, and the efficacy of current and/or novel vaccine approaches as well as antivirals. Mice are an advantageous small animal model because their immune system is evolutionarily similar to that found in humans, they are available from commercial vendors as genetically identical subjects, there are multiple strains that can be exploited to evaluate the genetic basis of infections, and they are relatively inexpensive and easy to manipulate. To recapitulate IAV infection in humans via the airways, mice are first anesthetized prior to intranasal inoculation with infectious IAVs under proper biosafety containment. After infection, the pathogenesis of IAVs is determined by monitoring daily the morbidity (body weight loss) and mortality (survival) rate. In addition, viral pathogenesis can also be evaluated by assessing virus replication in the upper (nasal mucosa) or lower (lungs) respiratory tract of infected mice. Humoral responses upon IAV infection can be rapidly evaluated by non-invasive bleeding and secondary antibody detection assays aimed at detecting the presence of total or neutralizing antibodies. Here, we describe the common methods used to infect mice intranasally (i.n) with IAV and evaluate pathogenesis, humoral immune responses and protection efficacy.

Influenza A viruses (IAVs) are important human respiratory pathogens. To understand the pathogenicity of IAVs and to perform preclinical testing of novel vaccine approaches, animal models mimicking human physiology are required. Here, we describe techniques to evaluate IAV pathogenesis, humoral responses and vaccine efficacy using a mouse model of infection.

Influenza viruses cause over 500,000 deaths worldwide1 and are associated with an annual cost of 12 - 14 billion USD in the United States alone ...

Establishment of the Dual Humanized TK-NOG Mouse Model for HIV-associated Liver Pathogenesis

Despite the increased life expectancy of patients infected with human immunodeficiency virus-1 (HIV-1), liver disease has emerged as a common cause of their morbidity. The liver immunopathology caused by HIV-1 remains elusive. Small xenograft animal models with human hepatocytes and human immune system can recapitulate the human biology of the disease&#39;s pathogenesis. Herein, a protocol is described to establish a dual humanized mouse model through human hepatocytes and CD34+ hematopoietic stem/progenitor cells (HSPCs) transplantation, to study liver immunopathology as observed in HIV-infected patients. To achieve dual reconstitution, male TK-NOG (NOD.Cg-Prkdcscid Il2rgtm1Sug Tg(Alb-TK)7-2/ShiJic) mice are intraperitoneally injected with ganciclovir (GCV) doses to eliminate mouse transgenic liver cells, and with treosulfan for nonmyeloablative conditioning, both of which facilitate human hepatocyte (HEP) engraftment and human immune system (HIS) development. Human albumin (ALB) levels are evaluated for liver engraftment, and the presence of human immune cells in blood detected by flow cytometry confirms the establishment of human immune system. The model developed using the protocol described here resembles multiple components of liver damage from HIV-1 infection. Its establishment could prove to be essential for studies of hepatitis virus co-infection and for the evaluation of antiviral and antiretroviral drugs.

This protocol provides a reliable method to establish humanized mice with both human immune system and liver cells. Dual reconstituted immunodeficient mice achieved via intrasplenic injection of human hepatocytes and CD34+ hematopoietic stem cells are susceptible to human immunodeficiency virus-1 infection and recapitulate liver damage as observed in HIV-infected patients.

Despite the increased life expectancy of patients infected with human immunodeficiency virus-1 (HIV-1), liver disease has emerged as a common cause of ...

High Throughput In Vitro Assessment of Latency Reversing Agents on HIV Transcription and Splicing

HIV remains incurable due to the existence of a reservoir of cells that harbors stable and latent form of the virus, which stays invisible to the immune system and is not targeted by the current antiretroviral therapy (cART). Transcription and splicing have been shown to reinforce HIV-1 latency in resting CD4+ T cells. Reversal of latency by the use of latency reversal agents (LRAs) in the &#34;shock and kill&#34; approach has been studied extensively in an attempt to purge this reservoir but has thus far not shown any success in clinical trials due to the lack of development of adequate small molecules that can efficiently perturb this reservoir. The protocol presented here provides a method for reliably and efficiently assessing latency reversal agents (LRAs) on HIV transcription and splicing. This approach is based on the use of an LTR-driven dual color reporter that can simultaneously measure the effect of an LRA on transcription and splicing by flow cytometry. The protocol described here is adequate for adherent cells as well as the cells in suspension. It is useful for testing a large number of drugs in a high throughput system. The method is technically simple to implement and cost-effective. In addition, the use of flow cytometry allows the assessment of cell viability and thus drug toxicity at the same time.

A high throughput protocol for functional assessment of HIV efficient reactivation and clearance of latent proviruses is described and applied by testing the impact of interventions on HIV transcription and splicing. Representative results of the effect of latency reversing agents on LTR-driven transcription and splicing are provided.

HIV remains incurable due to the existence of a reservoir of cells that harbors stable and latent form of the virus, which stays invisible to the immune ...

Identification of Nucleolar Factors During HIV-1 Replication Through Rev Immunoprecipitation and Mass Spectrometry

The HIV-1 infectious cycle requires viral protein interactions with host factors to facilitate viral replication, packaging, and release. The infectious cycle further requires the formation of viral/host protein complexes with HIV-1 RNA to regulate the splicing and enable nucleocytoplasmic transport. The HIV-1 Rev protein accomplishes the nuclear export of HIV-1 mRNAs through multimerization with intronic cis-acting targets - the Rev response element (RRE). A nucleolar localization signal (NoLS) exists within the COOH-terminus of the Rev arginine-rich motif (ARM), allowing the accumulation of Rev/RRE complexes in the nucleolus. Nucleolar factors are speculated to support the HIV-1 infectious cycle through various other functions in addition to mediating mRNA-independent nuclear export and splicing. We describe an immunoprecipitation method of wild-type (WT) Rev in comparison to Rev nucleolar mutations (deletion and single-point Rev-NoLS mutations) in the presence of HIV-1 replication for mass spectrometry. Nucleolar factors implicated in the nucleocytoplasmic transport (nucleophosmin B23 and nucleolin C23), as well as cellular splicing factors, lose interaction with Rev in the presence of Rev-NoLS mutations. Various other nucleolar factors, such as snoRNA C/D box 58, are identified to lose interaction with Rev mutations, yet their function in the HIV-1 replication cycle remain unknown. The results presented here demonstrate the use of this approach for the identification of viral/host nucleolar factors that maintain the HIV-1 infectious cycle. The concepts used in this approach are applicable to other viral and disease models requiring the characterization of understudied pathways.

Here we describe Rev immunoprecipitation in the presence of HIV-1 replication for mass spectrometry. The methods described can be used for the identification of nucleolar factors involved in the HIV-1 infectious cycle and are applicable to other disease models for the characterization of understudied pathways.

The HIV-1 infectious cycle requires viral protein interactions with host factors to facilitate viral replication, packaging, and release. The infectious ...