A Global Survey Of Transcript Expression In Rainbow Trout Leukocytes During The Early Response To Viral Hemorrhagic Septicemia Virus Infection     Caroline L. O’Farrell,1,2 Nikta Vaghefi,2 Pierre Boudinot,2 Abdenour Benmansour2   1Molecular Biology, American Type Culture Collection, 10801 University Boulevard, Manassas, VA; 2Institut National de la Recherche, Unité de Virologie et Immunologie Moléculaires, Jouy-en-Josas Cedex, France     Viral infections induce changes in the expression of host cell genes. A global knowledge of these modifications should help to better understand virus/host cell interactions. We used the suppressive subtractive hybridization (SSH) methodology in the viral hemorrhagic septicemia virus (VHSV) model of infection with rainbow trout Oncorhynchus mykiss to examine viral-induced changes in host gene expression. We infected rainbow trout leukocytes with VHSV, and total RNA from infected and mock-infected cells was compared at 40 hr post-infection. Twenty-four viral-induced genes were ultimately retrieved from the subtracted cDNA library, and their differential expression was further confirmed by semi-quantitative RT-PCR and northern blot hybridizations. Among these sequences, three have already been described as VHSV-induced genes. Nine sequences that have not been previously attributed to viral infection in trout and had known homologues were chosen for further study and extended to full-length cDNA using 5’and 3’RACE. They were subsequently classified into three functional subsets. Four genes were homologous to mammalian interferon responsive genes, three were similar to chemo-attractant molecules, and two had nucleic acid binding domains. The identification of these new viral-induced transcripts provide a framework for future functional studies of rainbow trout immunity.