Immunoreactivity and morphological changes of bursal follicles in chickens infected with vaccine or wild-type strains of the infectious bursal disease virus

• DOI: 10.1292/jvms.14-0599
• Publication Date: 2015-04-09T22:09:59Z
• Authors: Naoyuki AIHARA; Noriyuki HORIUCHI; Nanase HIKICHI; Mariko OCHIAI; Yuko HOSODA; Yoko ISHIKAWA; Yoko SHIMAZAKI; Koji OISHI
• Keywords: 0301 basic medicine; 2. Zero hunger; 03 medical and health sciences; Bursa of Fabricius; Avian Pathology; Animals; Viral Vaccines; Birnaviridae Infections; Chickens; Infectious bursal disease virus; Poultry Diseases; 3. Good health

Infectious bursal disease (IBD) is characterized by immunosuppression due to the depletion of lymphocytes in the atrophied bursa of Fabricius (BF). We have sometimes encountered contradictory findings: chickens infected with the vaccine IBD virus (IBDV) strain have sometimes exhibited a highly atrophied BF, but not immunosuppression. In this study, chickens administered vaccine or wild-type strains of IBDV were later vaccinated with the B1 strain of the Newcastle disease virus (NDV). Bursal changes were examined histologically with a focus on the bursal follicle. The immunoreactivity to NDV was also evaluated with the hemagglutination inhibition test. In gross examination, we observed a few chickens with a severely atrophied BF in vaccine strain-administered groups (vaccine groups), and the level of severity was the same as that in the wild-type strain-administered group (wild-type group). However, these chickens retained humoral antibody responses to NDV and were revealed to possess a higher number of bursal follicles than those of the wild-type group. These results indicated that macroscopic evaluation dose not accurately reflect the immunoreactivity and degree of bursal damage in IBDV-administered chickens. We also found non-immunosuppressed chickens in the wild-type group. These non-immunosuppressed chickens retained a significantly higher number of normal follicles and total follicles according to our statistical analysis. Furthermore, a high correlation coefficient between the NDV-HI titer and the number of normal follicles was found in the wild-type group. These results implied that the retained number of normal follicles is important for the immunoreactivity of chickens infected with IBDV.