Effects of avian infectious bronchitis virus antigen on eggshell formation and immunoreaction in hen oviduct

The aim of this study was to determine the mechanism by which the avian infectious bronchitis virus (IBV) affects eggshell formation. Attenuated IBV (aIBV group) or vehicle (control group) was injected into the oviductal magnum lumen of White Leghorn laying hens. The changes in the expression of genes related to eggshell formation (collagen types I and V, and CaBP-D28K), densities of cytotoxic cells (CD8⁺ and TCR-γδ⁺ T cells), and gene expression of molecules related to cytotoxic immunoreaction (B-NK, perforin, granzyme, and IL-2) and proinflammatory cytokines (IL-1β, IL-6 and IFN-γ) were examined by quantitative reverse transcriptase polymerase chain reaction or immunohistochemistry in the isthmus and uterus. Gene expression of IL-1β and IL-6receptors in the tubular gland cells of the isthmus and uterus was analyzed by reverse transcriptase polymerase chain reaction. Gene expression of collagen type I, but not collagen type V, in the isthmus and CaBP-D28K in the uterus was decreased in the aIBV group compared with that in the control. The frequencies of CD8⁺ cells and TCR-γδ⁺ T cells in the isthmus and uterus were significantly higher in the aIBV group than in the control group. The expression of cytotoxic molecular and proinflammatory cytokines was also higher in the aIBV group than in the control. The expression of IL-6 receptor, but not IL-1β receptor, was identified in the tubular gland cells in the isthmus and uterus. These results suggest that IBV infection causes disorder of eggshell formation by disturbing gene expression of collagen type I in the isthmus and CaBP-D28K in the uterus, probably via the effects of substances from cytotoxic cells and proinflammatory cytokines.