Immune regulation and transcriptomic profiling of chicken CD8⁺ T cells in response to infection with the IBV strain K047-12 during in vitro culture

Infectious bronchitis virus (IBV) is a highly contagious virus in poultry causing significant economic losses. Despite the implementation of various vaccines, the continuous emergence of regional variants had made complete protection challenging. T cell responses are critical for immunity against viral infections; however, a deeper understanding in avian T cell-mediated immune responses to IBV is still needed. In this study, we isolated splenocytes form 4–to 8-week-old specific-pathogen free (SPF) chickens and investigated their immune responses to the IBV strain K047-12. The IBV infection induced CD25high T cells during in vitro splenocyte culture and elevated gene expression of IL10 and IL12B, indicating T cell activation and a regulatory immune reaction. To further characterize CD8⁺ T cell–specific responses, we sorted CD44+ CD8⁺ T cells following IBV infection and performed transcriptomic analysis using two independent biological replicates per group. As result, IBV infection modulated multiple immune-related pathways, including the cytokine–cytokine interaction and TGF-β signaling pathways. Moreover, infected CD8⁺ T cells exhibited upregulation of IL6R, IL7R and NFKB1 genes associated with memory precursor and activated T cell status (CD44+), suggesting a potential shift toward a memory-like state. These findings suggest that IBV infection promotes activation and differentiation of CD8⁺ T cells, potentially driving a shift toward a memory-like phenotype. This information could enhance the understanding of avian antiviral T cell immunity and support the development of T cell–based protective strategy targeting IBV variants.