Discussion
Immune reaction to viral invasion is important to combat virus growth and to minimize any damage that can be imposed on the host cells [30]. In this study, the host immune response in the bursa of Fabricius, an organ mainly colonized by B lymphocytes, was assessed upon infection by the avian virus NDV genotype VII IBS002 and genotype VIII AF2240.
The cell population in the chicken bursa was evaluated by flow cytometry and the results showed that in normal chickens, this organ was predominantly occupied by B lymphocytes while the T lymphocyte and macrophage populations were at minimal cell numbers. Different from the cell population changes in chicken spleen upon NDV infection where CD4+ and CD8+ cells declined in their cell numbers …show more content…
IgM+ B cell was then further enriched from the chicken bursa to further understand the effects of inflammatory stress towards the development of humoral immunity that plays an important role to induce protection via the synthesis of effective antibodies against the virus [44]. As B lymphocytes were observed to be depleted in the bursa upon infection with the virus, the apoptosis assay was carried out. Apoptosis is a controlled cell death mode which is implicated in the pathogenesis of viruses that causes diseases [45]. The hallmarks of apoptosis including cell membrane blebbing, DNA fragmentation and Phosphatidylserine (PS) externalization [46] were evaluated by the AO/PI assay and Annexin V analysis in this study. Our results based on the trypan blue assay showed that NDV AF2240 reduced viability in and induced higher apoptotic cell rate in chicken bursa when compared to NDV IBS002. The changes were significantly observed since day 3 post infection. This result was in line with the Annexin V study which also showed that NDV AF2240 induced higher rate of apoptosis in the bursa than NDV IBS002. In the AO/Pi assay, cells showing characteristics of apoptotic cells such as membrane blebbing, chromation condensation and up taking propidium iodide stain were evaluated. Similar to the Annexin V results, our AO/Pi results demonstrated that the time course infection of NDV AF2240 induced greater magnitude of apoptosis in chicken bursa of Fabricius compared to IBS002. From our results, the cell cycle analysis showed that NDV AF2240 resulted in a higher population of sub G0/G1 compared to IBS002, showing that apoptotic events were higher during NDV AF2240 infection as sub G0/G1 indicated DNA fragmentation, which is also one of the apoptotic cells’ characteristics. The lower degree of B cell depletion in the bursa of NDV IBS002 infected chicken through apoptosis might contribute to
Immune reaction to viral invasion is important to combat virus growth and to minimize any damage that can be imposed on the host cells [30]. In this study, the host immune response in the bursa of Fabricius, an organ mainly colonized by B lymphocytes, was assessed upon infection by the avian virus NDV genotype VII IBS002 and genotype VIII AF2240.
The cell population in the chicken bursa was evaluated by flow cytometry and the results showed that in normal chickens, this organ was predominantly occupied by B lymphocytes while the T lymphocyte and macrophage populations were at minimal cell numbers. Different from the cell population changes in chicken spleen upon NDV infection where CD4+ and CD8+ cells declined in their cell numbers …show more content…
IgM+ B cell was then further enriched from the chicken bursa to further understand the effects of inflammatory stress towards the development of humoral immunity that plays an important role to induce protection via the synthesis of effective antibodies against the virus [44]. As B lymphocytes were observed to be depleted in the bursa upon infection with the virus, the apoptosis assay was carried out. Apoptosis is a controlled cell death mode which is implicated in the pathogenesis of viruses that causes diseases [45]. The hallmarks of apoptosis including cell membrane blebbing, DNA fragmentation and Phosphatidylserine (PS) externalization [46] were evaluated by the AO/PI assay and Annexin V analysis in this study. Our results based on the trypan blue assay showed that NDV AF2240 reduced viability in and induced higher apoptotic cell rate in chicken bursa when compared to NDV IBS002. The changes were significantly observed since day 3 post infection. This result was in line with the Annexin V study which also showed that NDV AF2240 induced higher rate of apoptosis in the bursa than NDV IBS002. In the AO/Pi assay, cells showing characteristics of apoptotic cells such as membrane blebbing, chromation condensation and up taking propidium iodide stain were evaluated. Similar to the Annexin V results, our AO/Pi results demonstrated that the time course infection of NDV AF2240 induced greater magnitude of apoptosis in chicken bursa of Fabricius compared to IBS002. From our results, the cell cycle analysis showed that NDV AF2240 resulted in a higher population of sub G0/G1 compared to IBS002, showing that apoptotic events were higher during NDV AF2240 infection as sub G0/G1 indicated DNA fragmentation, which is also one of the apoptotic cells’ characteristics. The lower degree of B cell depletion in the bursa of NDV IBS002 infected chicken through apoptosis might contribute to