Rhabdovirus infection induces public and private T cell responses in teleost fish

Many viruses induce a strong T cell response that contributes to the elimin ation of infected cells presenting viral peptides by MHC molecules. The str ucture and expression of genes encoding molecules homologous to mammalian a lpha beta TCRs have been recently characterized in rainbow trout and in sev eral teleost species, but the alpha beta T cell response against pathogens has not been directly demonstrated. To study the modifications of the T cel l repertoire during an acute viral infection in rainbow trout, we adapted t he immunoscope methodology, which consists of spectratyping the complementa rity-determining region 3 length of the TCR beta chain. We showed that the naive T cell repertoire is polyclonal and highly diverse in the naive rainb ow trout. Using viral hemorrhagic septicemia virus (VHSV), which provokes a n acute infection in rainbow trout, we identified skewed complementarity-de termining region 3 size profiles for several V betaJ beta combinations, cor responding to T cell clonal expansions during primary and secondary respons e to VHSV. Both public and private T cell expansions were shown by immunosc ope analysis of spleen cells from several infected individuals of a rainbow trout clone sharing the same genetic background. The public response to VH SV consisted of expansion of V beta 4J beta1 T cell, which appeared early d uring the primary response and was strongly boosted during the secondary re sponse.