Temperature modulates the protein dynamics of the antigen presentation pathway in VHSV IVb-infected rainbow trout (Oncorhynchus mykiss) cell lines

Rainbow trout face challenges due to climate change, increasing their susceptibility to pathogens like viruses. The endogenous antigen presentation pathway is essential for antiviral immunity by presenting intracellular antigens to cytotoxic lymphocytes. While previous studies show impaired expression of antigen presentation molecules at suboptimal temperatures, little is known about how temperature affects the protein function of the antigen presentation pathway during viral infections. This study aims to understand how temperature modulates the antigen presentation pathway in rainbow trout infected with the viral hemorrhagic septicemia virus (VHSV) IVb. Rainbow trout cell lines were exposed to 4 °C, 14 °C, and 20 °C and sampled at 1-, 4-, and 9-days post-infection (dpi). The cell surface expression of MHC-I and beta 2-microglobulin (β2m), the proteasome activity, β2m release and the secretion of IFN-I, were analyzed. Over the course of nine days, VHSV IVb-infected cells exposed to 14 °C and 20 °C, exhibited impaired MHC-I/β2m surface expression. In addition, proteasome activity was higher at 9 dpi at 14 °C and 20 °C, suggesting an increase in viral peptide processing. Release of β2m into the media, correlated with MHC-I recycling and trafficking, was detected at 14 °C. Also, differences in secretion of IFN I were observed between control and infected cells at 14 °C and 20 °C. However, no differences were observed at 4 °C, suggesting a reduced metabolic activity, impairing the virus' ability to downregulate the antigen presentation pathway. These results highlight temperature-dependent modulation of antigen presentation and viral processing, emphasizing the critical role of temperature in immune responses agaisnt viruses.