Molecular and Immunological Studies on Feline Immunodeficiency Virus

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The purpose of the project is to clarify the genetic properties of feline immunodeficiency virus (FIV) and to know the pathogenetic mechanism of the virus in vivo by studying comprehensively from the molecular biological and immunological aspects. The study is still continuing but we obtained the following results.1) We isolated four and five FIV strains from cats in Taiwan and Argentina, respectively. Sequence analyzes of their env V3-V5 region revealed that Taiwanese isolates belonged to subtype C and four of the five Argentine isolates formad a new cluster designated as subtype E.2) We established novel methods to measure both the viral burden in the peripheral blood mononuclear cells and the neutralizing antibody titer against FIV.And then, we applied the methods to analyzes of FIV-infected cats.3) We obtained monoclonal antibodies (mAbs) recognizing feline CD4 and CD8 alpha molecules. Further, we cloned the cDNA of feline CD8 alpha and beta chains and expressed them in COS-7 cells … More , and analyzed the sequences of the cDNA and the mAbs.4) We cloned genes of feline Fas antigen and Fas ligand. The Fas gene was 942 bp long and has a homology with human and murine homologues at 55.6 and 47.9% at amino acid level, respectively. The Fas ligand gene was 840 bp long and has a homology with human and murine homologues at 88.7 and 78.2% at amino acid level, respectively. The Fas antigen and the ligand were expressed in various tissues and several cell lines. Further we obtained some evidence that the Fas antigen-ligand system was associated with the apoptosis observed in FIV-infected cats.5) We constructed FIV mutants which deleted AP-1 binding site, vif and ORF-A genes, and inoculated them into SPF cats. We found that vif gene is quite important for the viral infectivity and growth ability in vivo. On the other hand, we also found that the AP-1 binding site has a little responsibility for the viral growth ability, and ORF-A gene is dispensable but responsible for the viral growth ability significantly in vivo. Less