DIVERSIFICATION OF CHEMOKINE CCL19 GENES IN SALMONIDS AND THEIR ROLE IN RAINBOW TROUT NASAL IMMUNITY
Ali Sepahi, University of New Mexico
Ali Sepahi, Elisa Casadei, Irene Salinas
Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, NM
Chemokines are small cytokines with several immune roles including migration and compartmentalization of lymphocytes. Chemokine genes have diversified in teleosts but the functional consequences of this diversification are poorly understood. Previously, chemokine CCL19 was found to be the main innate immune gene up-regulated in the nasal tissue of rainbow trout following intranasal vaccination with a viral vaccine. The goal of this study was to characterize all the CCL19 genes in salmonids and identify which of these genes have specialized roles in nasal immunity. We performed bioinformatics data searches using previously published CCL19 sequences for teleosts and other vertebrates. Results show a dramatic expansion of CCL19 genes in salmonids, with 7 genes identified in the trout genome. These genes share very low sequence identities and are located in four different chromosomes in Atlantic salmon. Tissue distribution studies and in vivo vaccination studies show that CCL19a (-1 and -2) is the main CCL19 form expressed in mucosal lymphoid tissues and responsive to nasal viral vaccination. In vivo nasal delivery of trout recombinant CCL19a1 induced enlargement of the nasal lamina propria, morphological changes in nasal MHC-II+ cells, increase in numbers of nasal CD8+ cells and up-regulation of immune genes related to antigen presentation and antiviral cellular immune responses. Our results demonstrate that expansion of CCL19 genes in salmonids resulted in acquisition of molecules with specialized mucosal immune roles, in this case nasal antiviral immune responses.