RESUMO
The purpose of the present in vivo study was to evaluate correlation of the virulence of the infectious bursal disease virus with the rate of apoptotic changes of the immature B lymphocytes in Bursa Fabricius [BF] and lymphoid cells of spleen. Experimental study. 21-day-old SPF chicks of leghorn breed.90 chicks were divided into three groups [TEST-IBDV, TEST -VAC and Control] of30 chicks each. Inoculation of the TEST-IBDV, TEST -VAC and Control groups were done with 1R-499 serotype of high-virulence infectious bursal disease Virus [WIBDV], D78 intermediate vaccine and normal saline, respectively. Furthermore, 20 chicks were categorited into two groups [Test and Control] of 10 chicks each. Test and Control groups were inoculated with WIBDV and normal saline, respectively. 3 days after inoculation, samples of BF and splenic tissues were sent to Pathology Lab for LM, H and Esatinig and TUNEL studies. Kruskal-Wallis, ANOVA and Mann-Whimeytest.LM and H and E staining showed many significant differences among groups. Furthermore, we showed VP2 and VP5, INF-gamma and TNF-alpha were the major inductive factors for development of apoptosis in the immature B lymphocytes of BF and spleen.The present in vivo research showed that there is always a significant correlation between the virulence of the virus and the rate of apoptotic changes in the BF tissue. Moreover, apoptosis can be considered as a definite factor in the pathogenesisof infectious bursaldisease [IBD]