The authors would like to thank the Animal Services team at The Pirbright Institute for their expertise in hatching, rearing, and culling birds and the expertise of Caroline Holt in aseptically removing the bursa of Fabricius. A.B. is funded through the Biotechnology and Biological Sciences Research Council (BBSRC) via grant BBS/E/I/00001845, K.D. is funded through the BBSRC via studentship BBS/E/I/00002115, and A.A. is funded through the National Centre for the Replacement, Refinement &#38; Reduction of Animals in Research (NC3Rs) via grant NC/R001138/1.

All procedures with animals must be ethically approved in advance. In our institution, all procedures are performed in accordance with the UK Animal (Scientific Procedures) Act 1986 under Home Office Establishment, Personal and Project licenses, after the approval of the internal Animal Welfare and Ethical Review Board (AWERB).
1. Preparation of chCD40L
<ol>
	<li>Culture HEK 293-msCD8-CD40L cells that stably express a soluble chCD40L construct in 1x Roswell Park Memorial Institute (RPMI) medium supplemented with 10% heat-inactivated (hi) fetal calf serum (FCS) and 1 &#181;g/mL puromycin at 37 &#176;C in an atmosphere containing 5% CO2. 
	NOTE: These cells are available from The Pirbright Institute following the signing of the appropriate material transfer agreement.</li>
	<li>Split the cells at a 1:5 density when confluent. Collect the supernatant (containing the soluble chCD40L construct) each time the cells are split, centrifuge it at 400 x g for 5 min to remove cellular debris, and store it at 4 &#176;C.</li>
	<li>When 500 mL of the supernatant has been collected, pool the liquid and filter-sterilize it through a 0.2 &#181;m filter.</li>
	<li>Concentrate the supernatant using centrifugal protein concentrators with a molecular-weight cutoff of 10 K according to the manufacturer&#8217;s instructions. Extract the concentrated supernatant from each column, pool it together, and filter-sterilize it by passing it through a 0.22 &#181;m syringe filter.</li>
	<li>Determine the final concentration to be used in experiments by serially diluting the chCD40L solution in 1x Iscove&#8217;s modified Dulbecco&#8217;s medium (IMDM) (described in step 2.4) and culturing primary bursal cells in the presence of the dilutions. Determine the number and percentage viability of the cells daily for up to a week. 
	NOTE: The lowest concentration where cell proliferation and viability are adequate is the concentration to use in the assay. This is likely to be between 1:20 and 1:50.</li>
</ol>
2. Preparation of Solutions for Chicken Primary Bursal Cell Isolation
<ol>
	<li>Prepare 1x Hanks&#8217; balanced salt solution (HBBS) with calcium (Ca) by adding 10 mL of 10x HBBS with Ca to 90 mL of sterile H2O and 0.47 &#181;L of 7.5% NaHCO3.</li>
	<li>Prepare collagenase D stock solution at 8 mg/mL in 1x HBBS with Ca. Filter-sterilize the solution through a 0.2 &#181;M filter. 
	NOTE: It is advisable to prepare 5 mL aliquots and freeze them at -20 &#176;C.</li>
	<li>Prepare 1x RPMI medium supplemented with 5% hi FCS. Store the media at 4 &#176;C.</li>
	<li>Prepare 1x 500 mL of IMDM supplemented with 8% hi FCS, 2% hi chicken serum, 50 mM &#946;-mercaptoethanol, 50 &#181;L of insulin-transferrin-sodium-selenite, and 1% penicillin/streptomycin. Store the media at 4 &#176;C. 
	NOTE: Prepare all the above-mentioned solutions in advance.</li>
	<li>Prepare 1x HBBS with Ca. Store the solution on ice.</li>
	<li>Prepare 1x HBBS without Ca by adding 10 mL of 10x HBBS without Ca to 90 mL of sterile H2O, 0.47 &#181;L of 7.5% NaHCO3, and EDTA at a final concentration of 10 mM. Store the solution on ice.</li>
	<li>Prepare 1x collagenase D solution by adding 5 mL of collagenase D stock solution to 13 mL of HBBS with Ca to make a total of 18 mL. Store the solution on ice. 
	NOTE: Prepare the solutions mentioned in steps 2.5&#8211;2.7 on the day of the experiment.</li>
</ol>
3. Removal of the Bursa of Fabricius (BF)
<ol>
	<li>Rear and hatch chickens in an appropriate, approved facility and humanely cull them at 2&#8211;3 weeks of age. 
	NOTE: Use institute-approved methods for culling.</li>
	<li>Collect the BF from each chicken using aseptic techniques. 
	NOTE: Use the protocols in place at the institution.
	<ol>
		<li>Place the carcass in dorsal recumbency and sterilize the skin and feathers overlaying the abdomen and thorax with a solution of 70% ethanol, diluted in water.</li>
		<li>Make a ventral midline incision in the lower abdomen using a sterilized scalpel or scissors.</li>
		<li>Locate the bursa of Fabricius, which is connected to the caudal section of the colon, cranial to the cloaca.</li>
		<li>Using sterilized forceps and scissors, cut the bursa of Fabricius free from the colon. Take care to avoid puncturing the gut.</li>
	</ol>
	</li>
	<li>Place the organ in cold PBS and transfer it to the laboratory on ice. 
	NOTE: Primary cells should be isolated as soon as possible after the organ harvest.</li>
</ol>
4. Isolation of Chicken Primary Bursal Cells
<ol>
	<li>Working in a microbiological safety cabinet, wash the BF at least 3x in 30 mL of cold PBS.</li>
	<li>Transfer the tissue to a Petri dish (92 mm in diameter, 21 mm in height) and add 5 mL of 1x collagenase D solution.</li>
	<li>Using sterile scissors or a scalpel blade, cut the BF into pieces of less than 5 mm in diameter.</li>
	<li>Incubate the tissue at 37 &#176;C with periodic gentle agitation for 30 min. 
	NOTE: The collagenase solution will begin to digest the tissue.&#160;</li>
	<li>Using a sterile Pasteur pipette, repeatedly aspirate the mixture to encourage disintegration of the tissue. If necessary, cut the tissue into smaller pieces.</li>
	<li>Add another 5 mL of 1x collagenase D solution to the tissue and incubate it at 37 &#176;C with periodic gentle agitation for another 30 min.</li>
	<li>Repeat steps 4.6 and 4.7 until the tissue is completely digested. 
	NOTE: There will be small granules that do not dissolve further.</li>
	<li>Pass the cell suspension through a 100 &#181;m cell strainer into 20 mL of 1x HBBS without Ca.</li>
	<li>Centrifuge the cell suspension at 400 x g for 5 min.</li>
	<li>Discard the supernatant and resuspend the pellet in 10 mL of 1x RPMI with 5% FCS.</li>
	<li>Either overlay 10 mL of the cell suspension on top of 5 mL of density gradient media containing polysucrose and sodium diatrizoate or underlay 5 mL of density gradient media beneath the 10 mL cell suspension. Ensure there is a clear interface between the two.</li>
	<li>Centrifuge the overlay at 900 x g for 20 min at 4 &#176;C. Lower or remove the centrifuge break. 
	NOTE: The cells should form a band at the interface between the cell media and the density gradient media.</li>
	<li>Using a sterile Pasteur pipette, remove the cells and place them in cold PBS. Wash the cells 3x by centrifuging them at 400 x g for 5 min and resuspending them in cold PBS.</li>
</ol>
5. Culture of Chicken Primary Bursal Cells
<ol>
	<li>Centrifuge the cell suspension at 400 x g for 5 min and resuspend them in 1x complete IMDM.</li>
	<li>Take an aliquot of the cell suspension, add it to a Trypan blue solution and count the number of viable cells that exclude the Trypan blue. Determine the number of cells and the percentage viability.</li>
	<li>Centrifuge the cell suspension at 400 x g for 5 min and resuspend it in complete IMDM supplemented with a 1:20 dilution of chicken CD40L at a density of 1 x 107 cells/mL. Titrate the concentrated supernatant containing the chCD40L to determine the optimal dilution, which is likely to lie in the range of 1:10 to 1:50.</li>
	<li>Culture the cells in either 96- or 24-well plates at 37 &#176;C for 48&#8211;72 h. U-bottomed 96-well plates are preferable to flat-bottomed plates. 
	NOTE: Cells can also be cultured at 40&#160;&#176;C</li>
</ol>
6. Infection of Chicken Primary Bursal Cells with IBDV
<ol>
	<li>48&#8211;72 h post-isolation, thaw an aliquot of the virus, vortex the sample, and store it on ice.</li>
	<li>Resuspend the primary bursal cells, take a 10-&#181;L aliquot of the cell suspension, add it to 10 &#181;L of a Trypan blue solution, and determine the number of cells and percentage viability.</li>
	<li>Dilute the virus in 1x complete IMDM to the appropriate multiplicity of infection (MOI) to make the virus inoculum and vortex.</li>
	<li>Centrifuge the cell suspension at 400 x g for 5 min.</li>
	<li>Remove the supernatant and resuspend the cells in the virus inoculum.</li>
	<li>Incubate the cell suspension at 37 &#176;C for 1 h with periodic agitation.</li>
	<li>Centrifuge the cell suspension at 400 x g for 5 min, remove the virus inoculum, and wash the cells in 1x complete IMDM media.</li>
	<li>Centrifuge the cell suspension at 400 x g for 5 min, remove the supernatant, and resuspend the cells in complete IMDM media supplemented with chicken CD40L at a density of 1 x 107 cells per mL.</li>
	<li>Culture the cells in either 96- or 24-well plates at 37 &#176;C. 
	NOTE: Cells can also be cultured at 40&#160;&#176;C</li>
</ol>
7. Quantification of IBDV Replication in Chicken Primary Bursal Cells
<ol>
	<li>At the desired time-point postinfection, resuspend the cells, transfer them to an appropriate tube, centrifuge them at 400 x g for 5 min and harvest the supernatant for virus titration by either plaque assay or TCID50 assay as per the Reed-Muench method15.</li>
	<li>Wash the cells in 1 mL of PBS and prepare them either for immunostaining with an antibody specific to IBDV, or extract RNA using an appropriate kit (following the manufacturer&#8217;s instructions) and perform reverse transcription quantitative polymerase chain reaction (RT-qPCR) using primers specific for an IBDV gene (Forward, GAGGTGGCCGACCTCAACT; Reverse, GCCCGGATTATGTCTTTGAAG). Mock-infected cell cultures should be used as a control.</li>
</ol>

<ol>
	<li>Hoerr, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+aspects+of+immunosuppression+in+poultry.">Clinical aspects of immunosuppression in poultry.</a> Avian Diseases. 54 (1), 2-15 (2010).</li><li>Schermuly, J., 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=In+vitro+model+for+lytic+replication,+latency,+and+transformation+of+an+oncogenic+alphaherpesvirus.">In vitro model for lytic replication, latency, and transformation of an oncogenic alphaherpesvirus.</a> Proceedings of the National Academy of Sciences of the United States of America. 112 (23), 7279-7284 (2015).</li><li>Farhanah, M. I., 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=Bursal+immunopathology+responses+of+specific-pathogen-free+chickens+and+red+jungle+fowl+infected+with+very+virulent+infectious+bursal+disease+virus.">Bursal immunopathology responses of specific-pathogen-free chickens and red jungle fowl infected with very virulent infectious bursal disease virus.</a> Archives of Virology. , (2018).</li><li>Farhanah, M. I., 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=Bursal+transcriptome+profiling+of+different+inbred+chicken+lines+reveals+key+differentially+expressed+genes+at+3+days+post-infection+with+very+virulent+infectious+bursal+disease+virus.">Bursal transcriptome profiling of different inbred chicken lines reveals key differentially expressed genes at 3 days post-infection with very virulent infectious bursal disease virus.</a> Journal of General Virology. 99 (1), 21-35 (2018).</li><li>Guo, X., 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=Differential+expression+of+the+Toll-like+receptor+pathway+and+related+genes+of+chicken+bursa+after+experimental+infection+with+infectious+bursa+disease+virus.">Differential expression of the Toll-like receptor pathway and related genes of chicken bursa after experimental infection with infectious bursa disease virus.</a> Archives of Virology. 157 (11), 2189-2199 (2012).</li><li>He, X., 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=Differential+Regulation+of+chTLR3+by+Infectious+Bursal+Disease+Viruses+with+Different+Virulence.">Differential Regulation of chTLR3 by Infectious Bursal Disease Viruses with Different Virulence.</a> In Vitro and In Vivo. Viral Immunology. 30 (7), 490-499 (2017).</li><li>Ou, C., 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=Transcription+profiles+of+the+responses+of+chicken+bursae+of+Fabricius+to+IBDV+in+different+timing+phases.">Transcription profiles of the responses of chicken bursae of Fabricius to IBDV in different timing phases.</a> Virology Journal. 14 (1), 93 (2017).</li><li>Rasoli, 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=Differential+modulation+of+immune+response+and+cytokine+profiles+in+the+bursae+and+spleen+of+chickens+infected+with+very+virulent+infectious+bursal+disease+virus.">Differential modulation of immune response and cytokine profiles in the bursae and spleen of chickens infected with very virulent infectious bursal disease virus.</a> BMC Veterinary Research. 11, 75 (2015).</li><li>Ruby, T., 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=Transcriptional+profiling+reveals+a+possible+role+for+the+timing+of+the+inflammatory+response+in+determining+susceptibility+to+a+viral+infection.">Transcriptional profiling reveals a possible role for the timing of the inflammatory response in determining susceptibility to a viral infection.</a> Journal of Virology. 80 (18), 9207-9216 (2006).</li><li>Smith, J., 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=Analysis+of+the+early+immune+response+to+infection+by+infectious+bursal+disease+virus+in+chickens+differing+in+their+resistance+to+the+disease.">Analysis of the early immune response to infection by infectious bursal disease virus in chickens differing in their resistance to the disease.</a> Journal of Virology. 89 (5), 2469-2482 (2015).</li><li>Tregaskes, C. A., 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=Conservation+of+biological+properties+of+the+CD40+ligand,+CD154+in+a+non-mammalian+vertebrate.">Conservation of biological properties of the CD40 ligand, CD154 in a non-mammalian vertebrate.</a> Developmental &amp; Comparative Immunology. 29 (4), 361-374 (2005).</li><li>Kothlow, S., 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=CD40+ligand+supports+the+long-term+maintenance+and+differentiation+of+chicken+B+cells+in+culture.">CD40 ligand supports the long-term maintenance and differentiation of chicken B cells in culture.</a> Developmental &amp; Comparative Immunology. 32 (9), 1015-1026 (2008).</li><li>Dulwich, K. 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=Differential+gene+expression+in+chicken+primary+B+cells+infected+ex+vivo+with+attenuated+and+very+virulent+strains+of+infectious+bursal+disease+virus+(IBDV).">Differential gene expression in chicken primary B cells infected ex vivo with attenuated and very virulent strains of infectious bursal disease virus (IBDV).</a> Journal of General Virology. 98 (12), 2918-2930 (2017).</li><li>Soubies, S. 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=Propagation+and+titration+of+infectious+bursal+disease+virus,+including+non-cell-culture-adapted+strains,+using+ex+vivo-stimulated+chicken+bursal+cells.">Propagation and titration of infectious bursal disease virus, including non-cell-culture-adapted strains, using ex vivo-stimulated chicken bursal cells.</a> Avian Pathology. 47 (2), 179-188 (2018).</li><li>Reed, L., Muench, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+method+of+estimating+fifty+percent+endpoints.">A simple method of estimating fifty percent endpoints.</a> American Journal of Hygiene. 27, 494-497 (1938).</li><li>Hui, R. K., Leung, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+Expression+Profile+of+Chicken+Embryo+Fibroblast+DF-1+Cells+Infected+with+Cell-Adapted+Infectious+Bursal+Disease+Virus.">Differential Expression Profile of Chicken Embryo Fibroblast DF-1 Cells Infected with Cell-Adapted Infectious Bursal Disease Virus.</a> PLoS One. 10 (6), e0111771 (2015).</li><li>Li, Y. P., 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=Transcriptional+profiles+of+chicken+embryo+cell+cultures+following+infection+with+infectious+bursal+disease+virus.">Transcriptional profiles of chicken embryo cell cultures following infection with infectious bursal disease virus.</a> Archives of Virology. 152 (3), 463-478 (2007).</li><li>Lin, J., 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=Genome-wide+profiling+of+chicken+dendritic+cell+response+to+infectious+bursal+disease.">Genome-wide profiling of chicken dendritic cell response to infectious bursal disease.</a> BMC Genomics. 17 (1), 878 (2016).</li><li>Quan, R., 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=Transcriptional+profiles+in+bursal+B-lymphoid+DT40+cells+infected+with+very+virulent+infectious+bursal+disease+virus.">Transcriptional profiles in bursal B-lymphoid DT40 cells infected with very virulent infectious bursal disease virus.</a> Virology Journal. 14 (1), 7 (2017).</li><li>Wong, R. 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The authors have nothing to disclose.

In this study, we describe the successful culture of chicken primary bursal cells ex vivo in the presence of soluble chCD40L and demonstrate that these cells can support the replication of an attenuated strain and a very virulent strain of IBDV. This ex vivo model can be used to determine how the cells respond to an IBDV infection13, which has distinct advantages over in vivo and in vitro studies.
When harvesting the BF, it is critical to not puncture the gut so as to avoid bacterial contamination of the isolated bursal cells. In addition, it is important to isolate the primary cells as soon as possible after the organ harvest to limit cell death. The need to use chCD40L is a limitation of the technique; however, work conducted by Soubies et al. shows that the use of phorbol 12-myristate 13-acetate (PMA) to prolong bursal cell viability instead of chCD40L14 may enable the model to be adopted by a greater number of laboratories. The protocol outlined above determines the optimal concentration of chCD40L empirically, by culturing primary B cells in serially diluted concentrations of the molecule and observing cell proliferation and viability. One potential modification to the protocol could be to purify the chCD40L molecule and to add a specific concentration to the cell culture media to avoid batch-to-batch variability.
In vivo studies have shown that following IBDV infection, there is an increase in the expression of genes involved in pro-inflammatory cytokine responses, Type I IFN responses, and apoptosis in the BF5,9,10. However, following infection, there is an influx of inflammatory cells and effector T cells into the BF, which differ in the genes they express compared to the infected B cell population9. It is, therefore, difficult to interpret how infected cells respond to IBDV. To address this, some research groups have characterized the transcriptional response of cells infected with IBDV in culture16,17,18,19,20. These in vitro studies have the advantage of well-defined MOIs and time-points postinfection. However, in vitro studies have typically been characterized in either fibroblast cells16,17,20 or dendritic cells18. While providing some insight into host cell-IBDV interactions, the current belief is that the infection of B cells is crucial to the pathogenesis of IBDV and, therefore, the relevance of the data cannot be overinterpreted. Prior to our ex vivo bursal cell culture model, only one study had characterized the cellular response of B cells to IBDV infection19; however, this study utilized an immortalized B cell line that was transformed due to infection with ALV, limiting the conclusions that could be made. In contrast, the ex vivo model of IBDV infection described here allows researchers to retain the advantages of in vitro studies, such as defined MOIs and time-points, while studying the interactions of the virus with its relevant host cell. As the primary bursal cells are obtained from uninfected BF tissue, there are no inflammatory or T cells present, and we have demonstrated by flow cytometry (using standard conditions) that, following chCD40L stimulation, 97% of the cell population is positive for the B cell marker Bu-1 (data not shown). Given that 3% of the cells are Bu-1 negative, it will be interesting to determine whether these cells become infected with IBDV and explore their gene expression and contribution to the pathogenesis.
We anticipate that the ex vivo chicken primary bursal cell culture model can also be expanded to study the host cell-virus interactions of other B-cell tropic viruses infecting chickens, such as ALV or REV, and could also be expanded to other avian species (e.g., ducks or turkeys). The ability to culture primary bursal cells ex vivo also opens up the possibility to study aspects of the pathogenesis and immunosuppression caused by these viruses without the need to infect birds. As in vivo studies cause significant morbidity, this will have a substantial impact on the replacement, refinement, and reduction of the use of animals in research.
In summary, the ex vivo chicken primary bursal cell culture model described here has the potential to expand the understanding of how avian B-cell tropic viruses interact with their host cells while reducing the number of birds used in in vivo infection studies. The techniques can be applied to multiple lymphoid organs, multiple viruses, and, potentially, multiple species of birds, making it an attractive model that can contribute to the avian virology and immunology fields.

The global poultry industry is essential to secure enough food for an expanding human population. However, immunosuppression is the threat to food security and the welfare of affected birds and represents a key economic challenge to the industry. The majority of cases of immunosuppression in chickens are caused by the infection with immunosuppressive viruses, with those most responsible for impairing acquired immunity having a tropism for T and B lymphocytes1. In birds, the majority of B cells are located within an organ known as the bursa of Fabricius (BF). B cells are susceptible to infection with several immunosuppressive viruses, including those that cause lysis, such as IBDV and Marek&#39;s disease virus (MDV), and those that cause transformation, such as avian leukosis virus (ALV) and reticuloendotheliosis virus (REV).
In order to develop better strategies for controlling these infections, it is essential to characterize the interaction of the viruses with chicken B cells. However, when B cells are removed from a bird, they do not survive well in ex vivo culture2, making it difficult to perform a thorough analysis of the interactions of IBDV with chicken B cells, or the early events following ALV or REV infection. Consequently, many host cell-virus interactions have been studied in vivo3,4,5,6,7,8,9,10. Although these studies are informative, they involve the use of infected birds which suffer from diseases that can be severe.
The CD40 ligand is a molecule that induces B cell proliferation11. Following identification of the gene encoding chicken CD40L (chCD40L), a soluble fusion protein was engineered that, when added to the culture media, induced the proliferation of chicken primary B cells ex vivo12. In 2015, B cells cultured in this fashion were found to support the replication of MDV2 and in 2017, we and others found that primary bursal cells stimulated with chCD40L could be used as a model to study IBDV replication13,14. Here, we describe the isolation and culture of chicken primary bursal cells, the infection of the cells with IBDV, and the quantification of viral replication. Although we describe the method in the context of the BF, this could be applied to isolate and culture cells from different lymphoid organs.

<table>
	<tbody>
		<tr>
			<td>RPMI-1640 Medium</td>
			<td>Merck</td>
			<td>R8758-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>gibco by Life Technologies</td>
			<td>10099-141</td>
			<td>heat-inactivate at 56&#176;C for 1 hour</td>
		</tr>
		<tr>
			<td>Puromycin Dihydrochloride</td>
			<td>Thermo Fisher Scientific</td>
			<td>A1113802</td>
			<td></td>
		</tr>
		<tr>
			<td>Nalgene Rapid-Flow Sterile Disposable Filter with a PES membrane</td>
			<td>Thermo Fisher Scientific</td>
			<td>168-0045</td>
			<td></td>
		</tr>
		<tr>
			<td>Pierce Protein Concentrator PES (10K MWCO, 20ml)</td>
			<td>Thermo Fisher Scientific</td>
			<td>88528</td>
			<td></td>
		</tr>
		<tr>
			<td>0.22&#181;m Millex-GP Syringe Filter</td>
			<td>Merck</td>
			<td>F7648</td>
			<td></td>
		</tr>
		<tr>
			<td>Hanks&#39; Balanced Salt Solution (HBBS) + CaCl2 + MgCl2</td>
			<td>gibco by Life Technologies</td>
			<td>14060-040</td>
			<td></td>
		</tr>
		<tr>
			<td>Hanks&#39; Balanced Salt Solution (HBBS) - CaCl2 - MgCl2</td>
			<td>gibco by Life Technologies</td>
			<td>14180-046</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid solution (EDTA)</td>
			<td>Merck</td>
			<td>03690-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Iscove&#39;s Modified Dulbecco&#39;s Medium (IMDM) (1 X) + GlutaMAX</td>
			<td>gibco by Life Technologies</td>
			<td>31980-030</td>
			<td></td>
		</tr>
		<tr>
			<td>Chicken Serum</td>
			<td>Merck</td>
			<td>C5405-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoethanol 50mM</td>
			<td>gibco by Life Technologies</td>
			<td>31350-010</td>
			<td></td>
		</tr>
		<tr>
			<td>insulin-transferrin-sodium-selenite</td>
			<td>gibco by Life Technologies</td>
			<td>41400-045</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase D</td>
			<td>Roche Diagnostics GmbH</td>
			<td>11088882001</td>
			<td></td>
		</tr>
		<tr>
			<td>100&#181;m Cell Strainer</td>
			<td>Corning</td>
			<td>431752</td>
			<td></td>
		</tr>
		<tr>
			<td>Histopaque-1083</td>
			<td>Merck</td>
			<td>10831-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan Blue solution</td>
			<td>Merck</td>
			<td>T8154-20ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Nunc96 Well-Polystyrene Round Bottom Microwell Plates</td>
			<td>Thermo Fisher Scientific</td>
			<td>163320</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon 24-well Clear Flat Bottom TC-treated Multiwell Cell Culture Plate, with Lid, Sterile</td>
			<td>Corning</td>
			<td>353047</td>
			<td></td>
		</tr>
		<tr>
			<td>Rneasy Mini Kit</td>
			<td>Qiagen</td>
			<td>74104</td>
			<td></td>
		</tr>
	</tbody>
</table>

an ex vivo chicken primary bursal-cell culture model to study infectious bursal disease virus pathogenesis

Infectious bursal disease virus (IBDV) is a birnavirus of economic importance to the poultry industry. The virus infects B cells, causing morbidity, mortality, and immunosuppression in infected birds. In this study, we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with IBDV, and the quantification of viral replication. The addition of chicken CD40 ligand significantly increased cell proliferation fourfold over six days of culture and significantly enhanced cell viability. Two strains of IBDV, a cell-culture adapted strain, D78, and a very virulent strain, UK661, replicated well in the ex vivo cell cultures. This model will be of use in determining how cells respond to IBDV infection and will permit a reduction in the number of infected birds used in IBDV pathogenesis studies. The model can also be expanded to include other viruses and could be applied to different species of birds.

Chicken Primary Bursal Cells Can Be Cultured in the Presence of Chicken CD40L
When chicken primary bursal cells were cultured in the presence of soluble chCD40L, the number of cells increased fourfold from 9.02 x 105 to 3.63 x 106 per mL over a period of 6 days, in contrast to when it was absent (p &#60;0.05) (Figure 1A). Cell viability was also significantly improved, for example from 25% at day 3 post-culture in the absence of chCD40L to 48% in the presence of chCD40L (p &#60;0.05) (Figure 1B)13.
Chicken Primary Bursal Cells Can Support the Replication of Both Cell-culture Adapted and Very Virulent Strains of IBDV
Mock-infected and infected cell cultures were fixed 18 h postinfection, labeled with a monoclonal antibody against IBDV VP2 and a secondary antibody conjugated to Alexa Fluor 488, and counterstained with DAPI. Infected cells had evidence of green fluorescence around the nucleus (Figure 2A), consistent with the presence of IBDV in the cytoplasm. This was evident for two strains of IBDV, a cell-culture adapted strain, D78, and a very virulent strain, UK661 (Figure 2A). At 5, 18, 24, and 48 h postinfection, RNA was extracted from infected cultures and subjected to RT-qPCR with primers specific to a conserved region of the IBDV VP4 gene. The expression of VP4 was first normalized to the house-keeping gene TBP and then expressed as fold change relative to mock samples in a &#916;&#916;Ct analysis. IBDV VP4 expression increased to 16,603 copies at 48 h postinfection with D78 and 38,632 copies at 48 h postinfection with UK661. Taken together, these data demonstrate that the chicken primary bursal cells could support the replication of cell-culture-adapted and very virulent IBDV strains13.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58489/58489fig1.jpg" /> 
Figure 1: Chicken primary bursal cells can be cultured in the presence of chicken CD40L. Chicken primary bursal cells were cultured in the presence or absence of chCD40L (black bars and white bars, respectively). (A) The number of live cells and (B) the percentage of viable cells were determined at the indicated time-points postinfection. The data shown are representative of at least three replicate experiments, the error bars represent the standard deviation of the mean, and the statistical significance was determined using a paired Student&#39;s t-test at each time-point, * p &#60;0.05. This figure has been modified with permission from Dulwich et al.13.
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58489/58489fig2.jpg" /> 
Figure 2: Chicken primary bursal cells can support the replication of both cell-culture adapted and very virulent strains of IBDV. (A) Chicken primary bursal cells were mock-infected or infected with either D78 or UK661 and a sample from each culture was fixed, labeled and imaged: IBDV VP2, green; nuclei, blue. Scale bar = 7 &#181;m. (B) RNA was extracted at the indicated time-points postinfection, reverse-transcribed, and a conserved region of the IBDV VP4 gene was amplified by quantitative PCR. The log10 fold change in VP4 copy number was normalized to the TBP housekeeping gene and expressed relative to mock-infected samples as per the 2-&#916;&#916;CT method. The data shown are representative of at least three replicate experiments, and the error bars represent the standard deviation of the mean. This figure has been modified with permission from Dulwich et al.13.

Watch this Scientific Journal Video about An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis at JoVE.com

An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Here we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with infectious bursal disease virus, and the quantification of viral replication.

An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Infectious bursal disease virus (IBDV) is a birnavirus of economic importance to the poultry industry. The virus infects B cells, causing morbidity, ...

an-ex-vivo-chicken-primary-bursal-cell-culture-model-to-study

Nanyang Technological University

Research

JoVE Journal

Immunology and Infection

8.9K Views.  The Pirbright Institute. Here we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with infectious bursal disease virus, and the quantification of viral replication.

Video: An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Detection of Infectious Virus from Field-collected Mosquitoes by Vero Cell Culture Assay

Mosquitoes transmit a number of distinct viruses including important human pathogens such as West Nile virus, dengue virus, and chickungunya virus. Many of these viruses have intensified in their endemic ranges and expanded to new territories, necessitating effective surveillance and control programs to respond to these threats. One strategy to monitor virus activity involves collecting large numbers of mosquitoes from endemic sites and testing them for viral infection. In this article, we describe how to handle, process, and screen field-collected mosquitoes for infectious virus by Vero cell culture assay. Mosquitoes are sorted by trap location and species, and grouped into pools containing &le;50 individuals. Pooled specimens are homogenized in buffered saline using a mixer-mill and the aqueous phase is inoculated onto confluent Vero cell cultures (Clone E6). Cell cultures are monitored for cytopathic effect from days 3-7 post-inoculation and any viruses grown in cell culture are identified by the appropriate diagnostic assays. By utilizing this approach, we have isolated 9 different viruses from mosquitoes collected in Connecticut, USA, and among these, 5 are known to cause human disease. Three of these viruses (West Nile virus, Potosi virus, and La Crosse virus) represent new records for North America or the New England region since 1999. The ability to detect a wide diversity of viruses is critical to monitoring both established and newly emerging viruses in the mosquito population.

We describe a method to process and screen field-collected mosquitoes for a diversity of viruses by Vero cell culture assay. By employing this technique, we have detected 9 different viruses from 4 taxonomic families in mosquitoes collected in Connecticut.

Mosquitoes transmit a number of distinct viruses including important human pathogens such as West Nile virus, dengue virus, and chickungunya virus. Many ...

Parasite Induced Genetically Driven Autoimmune Chagas Heart Disease in the Chicken Model

The Trypanosoma cruzi acute infections acquired in infancy and childhood seem asymptomatic, but approximately one third of the chronically infected cases show Chagas disease up to three decades or later. Autoimmunity and parasite persistence are competing theories to explain the pathogenesis of Chagas disease 1, 2. To separate roles played by parasite persistence and autoimmunity in Chagas disease we inoculate the T. cruzi in the air chamber of fertilized eggs. The mature chicken immune system is a tight biological barrier against T. cruzi and the infection is eradicated upon development of its immune system by the end of the first week of growth 3. The chicks are parasite-free at hatching, but they retain integrated parasite mitochondrial kinetoplast DNA (kDNA) minicircle within their genome that are transferred to their progeny. Documentation of the kDNA minicircle integration in the chicken genome was obtained by a targeted prime TAIL-PCR, Southern hybridizations, cloning, and sequencing 3, 4. The kDNA minicircle integrations rupture open reading frames for transcription and immune system factors, phosphatase (GTPase), adenylate cyclase and phosphorylases (PKC, NF-Kappa B activator, PI-3K) associated with cell physiology, growth, and differentiation 3, 5-7, and other gene functions. Severe myocarditis due to rejection of target heart fibers by effectors cytotoxic lymphocytes is seen in the kDNA mutated chickens, showing an inflammatory cardiomyopathy similar to that seen in human Chagas disease. Notably, heart failure and skeletal muscle weakness are present in adult chickens with kDNA rupture of the dystrophin gene in chromosome 1 8. Similar genotipic alterations are associated with tissue destruction carried out by effectors CD45+, CD8&gamma;&delta;+, CD8&alpha; lymphocytes. Thus this protozoan infection can induce genetically driven autoimmune disease.

The inoculation of Trypanosoma cruzi in fertile eggs prior to incubation renders the parasite kDNA minicircle integration in embryo cells genome. Crossbreeding reveals the vertical transfer of the mutations to progeny. The kDNA integrates into coding regions at several chromosomes and the chickens die with an inflammatory autoimmune heart disease.

The Trypanosoma cruzi acute infections acquired in infancy and childhood seem asymptomatic, but approximately one third of the chronically infected cases ...

A Primary Neuron Culture System for the Study of Herpes Simplex Virus Latency and Reactivation

Herpes simplex virus type-1 (HSV-1) establishes a life-long latent infection in peripheral neurons. This latent reservoir is the source of recurrent reactivation events that ensure transmission and contribute to clinical disease. Current antivirals do not impact the latent reservoir and there are no vaccines. While the molecular details of lytic replication are well-characterized, mechanisms controlling latency in neurons remain elusive. Our present understanding of latency is derived from in vivo studies using small animal models, which have been indispensable for defining viral gene requirements and the role of immune responses. However, it is impossible to distinguish specific effects on the virus-neuron relationship from more general consequences of infection mediated by immune or non-neuronal support cells in live animals. In addition, animal experimentation is costly, time-consuming, and limited in terms of available options for manipulating host processes. To overcome these limitations, a neuron-only system is desperately needed that reproduces the in vivo characteristics of latency and reactivation but offers the benefits of tissue culture in terms of homogeneity and accessibility.
Here we present an in vitro model utilizing cultured primary sympathetic neurons from rat superior cervical ganglia (SCG) (Figure 1) to study HSV-1 latency and reactivation that fits most if not all of the desired criteria. After eliminating non-neuronal cells, near-homogeneous TrkA+ neuron cultures are infected with HSV-1 in the presence of acyclovir (ACV) to suppress lytic replication. Following ACV removal, non-productive HSV-1 infections that faithfully exhibit accepted hallmarks of latency are efficiently established. Notably, lytic mRNAs, proteins, and infectious virus become undetectable, even in the absence of selection, but latency-associated transcript (LAT) expression persists in neuronal nuclei. Viral genomes are maintained at an average copy number of 25 per neuron and can be induced to productively replicate by interfering with PI3-Kinase / Akt signaling or the simple withdrawal of nerve growth factor1. A recombinant HSV-1 encoding EGFP fused to the viral lytic protein Us11 provides a functional, real-time marker for replication resulting from reactivation that is readily quantified. In addition to chemical treatments, genetic methodologies such as RNA-interference or gene delivery via lentiviral vectors can be successfully applied to the system permitting mechanistic studies that are very difficult, if not impossible, in animals. In summary, the SCG-based HSV-1 latency / reactivation system provides a powerful, necessary tool to unravel the molecular mechanisms controlling HSV1 latency and reactivation in neurons, a long standing puzzle in virology whose solution may offer fresh insights into developing new therapies that target the latent herpesvirus reservoir.

The protocol describes an efficient and reproducible model system to study herpes simplex virus type 1 (HSV-1) latency and reactivation. The assay employs homogenous sympathetic neuron cultures and allows for the molecular dissection of virus-neuron interactions using a variety of tools including RNA interference and expression of recombinant proteins.

Herpes simplex virus type-1 (HSV-1) establishes a life-long latent infection in peripheral neurons. This latent reservoir is the source of recurrent ...

Saliva, Salivary Gland, and Hemolymph Collection from Ixodes scapularis Ticks

Ticks are found worldwide and afflict humans with many tick-borne illnesses. Ticks are vectors for pathogens that cause Lyme disease and tick-borne relapsing fever (Borrelia spp.), Rocky Mountain Spotted fever (Rickettsia rickettsii), ehrlichiosis (Ehrlichia chaffeensis and E. equi), anaplasmosis (Anaplasma phagocytophilum), encephalitis (tick-borne encephalitis virus), babesiosis (Babesia spp.), Colorado tick fever (Coltivirus), and tularemia (Francisella tularensis) 1-8. To be properly transmitted into the host these infectious agents differentially regulate gene expression, interact with tick proteins, and migrate through the tick 3,9-13. For example, the Lyme disease agent, Borrelia burgdorferi, adapts through differential gene expression to the feast and famine stages of the tick's enzootic cycle 14,15. Furthermore, as an Ixodes tick consumes a bloodmeal Borrelia replicate and migrate from the midgut into the hemocoel, where they travel to the salivary glands and are transmitted into the host with the expelled saliva 9,16-19.
As a tick feeds the host typically responds with a strong hemostatic and innate immune response 11,13,20-22. Despite these host responses, I. scapularis can feed for several days because tick saliva contains proteins that are immunomodulatory, lytic agents, anticoagulants, and fibrinolysins to aid the tick feeding 3,11,20,21,23. The immunomodulatory activities possessed by tick saliva or salivary gland extract (SGE) facilitate transmission, proliferation, and dissemination of numerous tick-borne pathogens 3,20,24-27. To further understand how tick-borne infectious agents cause disease it is essential to dissect actively feeding ticks and collect tick saliva. This video protocol demonstrates dissection techniques for the collection of hemolymph and the removal of salivary glands from actively feeding I. scapularis nymphs after 48 and 72 hours post mouse placement. We also demonstrate saliva collection from an adult female I. scapularis tick.

Saliva, Salivary Gland, and Hemolymph Collection from Ixodes scapularis Ticks

The collection of infected tick hemolymph, salivary glands, and saliva is important to study how tick-borne pathogens cause disease. In this protocol we demonstrate how to collect hemolymph and salivary glands from feeding Ixodes scapularis nymphs. We also demonstrate saliva collection from female I. scapularis adults.

Ticks are found worldwide and afflict humans with many tick-borne illnesses. Ticks are vectors for pathogens that cause Lyme disease and tick-borne ...

An In vitro Co-infection Model to Study Plasmodium falciparum-HIV-1 Interactions in Human Primary Monocyte-derived Immune Cells

Plasmodium falciparum, the causative agent of the deadliest form of malaria, and human immunodeficiency virus type-1 (HIV-1) are among the most important health problems worldwide, being responsible for a total of 4 million deaths annually1. Due to their extensive overlap in developing regions, especially Sub-Saharan Africa, co-infections with malaria and HIV-1 are common, but the interplay between the two diseases is poorly understood. Epidemiological reports have suggested that malarial infection transiently enhances HIV-1 replication and increases HIV-1 viral load in co-infected individuals2,3. Because this viremia stays high for several weeks after treatment with antimalarials, this phenomenon could have an impact on disease progression and transmission.
The cellular immunological mechanisms behind these observations have been studied only scarcely. The few in vitro studies investigating the impact of malaria on HIV-1 have demonstrated that exposure to soluble malarial antigens can increase HIV-1 infection and reactivation in immune cells. However, these studies used whole cell extracts of P. falciparum schizont stage parasites and peripheral blood mononuclear cells (PBMC), making it hard to decipher which malarial component(s) was responsible for the observed effects and what the target host cells were4,5. Recent work has demonstrated that exposure of immature monocyte-derived dendritic cells to the malarial pigment hemozoin increased their ability to transfer HIV-1 to CD4+ T cells6,7, but that it decreased HIV-1 infection of macrophages8. To shed light on this complex process, a systematic analysis of the interactions between the malaria parasite and HIV-1 in different relevant human primary cell populations is critically needed.
Several techniques for investigating the impact of HIV-1 on the phagocytosis of micro-organisms and the effect of such pathogens on HIV-1 replication have been described. We here present a method to investigate the effects of P. falciparum-infected erythrocytes on the replication of HIV-1 in human primary monocyte-derived macrophages. The impact of parasite exposure on HIV-1 transcriptional/translational events is monitored by using single cycle pseudotyped viruses in which a luciferase reporter gene has replaced the Env gene while the effect on the quantity of virus released by the infected macrophages is determined by measuring the HIV-1 capsid protein p24 by ELISA in cell supernatants.

An In vitro Co-infection Model to Study Plasmodium falciparum-HIV-1 Interactions in Human Primary Monocyte-derived Immune Cells

We have developed an in vitro malaria-HIV-1 co-infection model to study the impact of Plasmodium falciparum on the HIV-1 replicative cycle in human primary monocyte-derived macrophages. This versatile system can easily be adapted to other primary cell types susceptible to HIV-1 infection.

Plasmodium falciparum, the causative agent  of the deadliest form of malaria, and human immunodeficiency virus type-1 (HIV-1) are among the most important ...

Isolation, Purification and Labeling of Mouse Bone Marrow Neutrophils for Functional Studies and Adoptive Transfer Experiments

Neutrophils are critical effector cells of the innate immune system. They are rapidly recruited at sites of acute inflammation and exert protective or pathogenic effects depending on the inflammatory milieu. Nonetheless, despite the indispensable role of neutrophils in immunity, detailed understanding of the molecular factors that mediate neutrophils' effector and immunopathogenic effects in different infectious diseases and inflammatory conditions is still lacking, partly because of their short half life, the difficulties with handling of these cells and the lack of reliable experimental protocols for obtaining sufficient numbers of neutrophils for downstream functional studies and adoptive transfer experiments. Therefore, simple, fast, economical and reliable methods are highly desirable for harvesting sufficient numbers of mouse neutrophils for assessing functions such as phagocytosis, killing, cytokine production, degranulation and trafficking. To that end, we present a reproducible density gradient centrifugation-based protocol, which can be adapted in any laboratory to isolate large numbers of neutrophils from the bone marrow of mice with high purity and viability. Moreover, we present a simple protocol that uses CellTracker dyes to label the isolated neutrophils, which can then be adoptively transferred into recipient mice and tracked in several tissues for at least 4 hr post-transfer using flow cytometry. Using this approach, differential labeling of neutrophils from wild-type and gene-deficient mice with different CellTracker dyes can be successfully employed to perform competitive repopulation studies for evaluating the direct role of specific genes in trafficking of neutrophils from the blood into target tissues in vivo.

We describe a protocol for isolation and purification of neutrophils from mouse bone marrow by density gradient centrifugation and for neutrophil labeling using CellTracker dyes. This represents a simple, fast, reproducible and economical method for obtaining large numbers of neutrophils for downstream functional studies or adoptive transfer and tracking experiments.

Neutrophils are critical effector cells of the innate immune system. They are rapidly recruited at sites of acute inflammation and exert protective or ...

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (HRSV) infections present a broad spectrum of disease severity, ranging from mild infections to life-threatening bronchiolitis. An important part of the pathogenesis of severe disease is an enhanced immune response leading to immunopathology.	Here, we describe a protocol used to investigate the immune response of human immune cells to an HRSV infection. First, we describe methods used for culturing, purification and quantification of HRSV. Subsequently, we describe a human in vitro model in which peripheral blood mononuclear cells (PBMCs) are stimulated with live HRSV. This model system can be used to study multiple parameters that may contribute to disease severity, including the innate and adaptive immune response. These responses can be measured at the transcriptional and translational level. Moreover, viral infection of cells can easily be measured using flow cytometry. Taken together, stimulation of PBMC with live HRSV provides a fast and reproducible model system to examine mechanisms involved in HRSV-induced disease.

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection

Human respiratory syncytial virus (HRSV) can cause severe bronchiolitis in young infants. Part of the pathogenesis of severe HRSV disease is caused by the host immune response. Stimulation of primary human immune cells with HRSV provides a fast and reproducible model system to study activation of inflammatory pathways and infection.

Human respiratory syncytial  virus (HRSV) infections present a broad spectrum of disease severity, ranging  from mild infections to life-threatening ...

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV is an RNA virus of the Flaviviridae family. ZIKV is mainly transmitted by mosquitoes, but can also be spread by maternal to fetal vertical transmission as well as sexual contact. To date, there are no reliable treatment or vaccine options available to protect those infected by the virus. The development of a reproducible, effective Zika virus infectious cell culture system is critical for studying the molecular mechanisms of ZIKV replication as well as drug and vaccine development. In this regard, a protocol describing a mammalian cell-based in vitro Zika virus culture system for viral production and growth analysis is reported here. Details on the formation of plaques by Zika virus on a cell monolayer and plaque assay for measuring viral titer are presented. Viral genome replication kinetics and double-stranded RNA genome replicatory intermediates are determined. This culture platform was utilized to screen against a library of a small set of cytokines resulting in the identification of interferon-&#945; (IFN-&#945;), IFN-&#946; and IFN-&#947; as potent inhibitors of Zika viral growth. In summary, an in vitro infectious Zika viral culture system and various virological assays are demonstrated in this study, which has the potential to greatly benefit the research community in elucidating further the mechanisms of viral pathogenesis and the evolution of viral virulence. Antiviral IFN-alpha can further be evaluated as a prophylactic, post-exposure prophylactic, and treatment option for Zika virus infections in high-risk populations, including infected pregnant women.

Zika Virus Infectious Cell Culture System and the In Vitro Prophylactic Effect of Interferons

Zika Virus (ZIKV), an emerging pathogen, is linked to fetal developmental abnormalities and microcephaly. The establishment of an effective infectious cell culture system is crucial for studies of ZIKV replication as well as vaccine and drug development. In this study, various virological assays pertaining to ZIKV are illustrated and discussed.

Zika Virus (ZIKV) is an emerging pathogen that is linked to fetal developmental abnormalities such as microcephaly, eye defects, and impaired growth. ZIKV ...

Rescue and Characterization of Recombinant Virus from a New World Zika Virus Infectious Clone

Infectious cDNA clones allow for genetic manipulation of a virus, thus facilitating work on vaccines, pathogenesis, replication, transmission and viral evolution. Here we describe the construction of an infectious clone for Zika virus (ZIKV), which is currently causing an explosive outbreak in the Americas. To prevent toxicity to bacteria that is commonly observed with flavivirus-derived plasmids, we generated a two-plasmid system which separates the genome at the NS1 gene and is more stable than full-length constructs that could not be successfully recovered without mutations. After digestion and ligation to join the two fragments, full-length viral RNA can be generated by in vitro transcription with T7 RNA polymerase. Following electroporation of transcribed RNA into cells, virus was recovered that exhibited similar in vitro growth kinetics and in vivo virulence and infection phenotypes in mice and mosquitoes, respectively.

This protocol describes the recovery of infectious Zika virus from a two-plasmid infectious cDNA clone.

Infectious cDNA clones allow for genetic manipulation of a virus, thus facilitating work on vaccines, pathogenesis, replication, transmission and viral ...

The Madagascar Hissing Cockroach as an Alternative Non-mammalian Animal Model to Investigate Virulence, Pathogenesis, and Drug Efficacy

Many aspects of innate immunity are conserved between mammals and insects. An insect, the Madagascar hissing cockroach from the genus Gromphadorhina, can be utilized as an alternative animal model for the study of virulence, host-pathogen interaction, innate immune response, and drug efficacy. Details for the rearing, care and breeding of the hissing cockroach are provided. We also illustrate how it can be infected with bacteria such as the intracellular pathogens Burkholderia mallei, B. pseudomallei, and B. thailandensis. Use of the hissing cockroach is inexpensive and overcomes regulatory issues dealing with the use of mammals in research. In addition, results found using the hissing cockroach model are reproducible and similar to those obtained using mammalian models. Thus, the Madagascar hissing cockroach represents an attractive surrogate host that should be explored when conducting animal studies.

We present a protocol to utilize the Madagascar hissing cockroach as an alternative non-mammalian animal model to conduct bacterial virulence, pathogenesis, drug toxicity, drug efficacy, and innate immune response studies.

Many aspects of innate immunity are conserved between mammals and insects. An insect, the Madagascar hissing cockroach from the genus Gromphadorhina, can ...