KMAN Publication Inc. Journal of Poultry Sciences and Avian Diseases 2981-135X 4 Serial Number 15 2026 06 01 Comparative Histopathology and Immunogenicity of two Commercially Available Infectious Bronchitis GI-13 Vaccine Strains in Broiler Chickens Comparative Histopathology and Immunogenicity of two Commercially Available Infectious Bronchitis GI-13 Vaccine Strains in Broiler Chickens 1 11 10.61838/kman.jpsad.13 EN Journal Article <table> <tbody> <tr> <td> <p>Vaccine development is a lengthy process, and safety and efficacy studies are crucial before and after a vaccine's commercial use. The aim of this study was to evaluate the immunogenicity and histopathological effects of two commercially produced Infectious Bronchitis vaccines from the GI-13 lineage in young chickens. Seventy-five broiler chickens were divided into three groups of 25 (groups 1-3). At 21 days of age, the chickens were vaccinated through the ocular route. The first two groups were vaccinated against IB, while the last group served as the control group and remained unvaccinated. Using ELISA, the humoral immune response, as measured by antibodies, was assessed 3 weeks post-vaccination. Five days after vaccine administration, histopathology of the trachea and kidney was examined in vaccinated and control group chickens, and real-time PCR was performed to determine the RNA virus load in tracheal swabs. The results confirmed that both vaccines elicited serum antibody responses of 0.2618±0.1358 (Mean OD±Standard Deviation) in the first group and 0.2789±0.1164 in the second group, both of which were higher than those of the control group. Despite some variations between them, the difference was not statistically significant (p&gt;0.05). However, the 793/B-like vaccine in group 2 had much higher histopathological lesion scores in the kidney (Group 1: 2.600±0.8944 and 3.800±0.4472 for Group 2) and the trachea (Group 1 scored a mean of 1.800±0.4472, while the second group scored a higher mean of 2.800±0.8367) (p&lt;0.05), indicating that different vaccines may cause varying changes in the microscopic structure of tissues. Real-time RT-PCR analysis with 24 and 24.42 CT values for the first and second vaccinated groups, respectively, revealed no preference for vaccine strains, indicating similar viral loads. In conclusion, these findings suggest that both vaccines are immunogenic and, despite potentially having the same replication rate, one vaccine may be safer, causing less damage to target tissues in chickens. This means that choosing the right vaccine is important for controlling poultry diseases and managing poultry health.</p> </td> </tr> </tbody> </table> https://www.journals.kmanpub.com/index.php/jpsad/article/download/6086/11620