Infection of cats by injection with DNA of a feline immunodeficiency virus molecular clone

Establishment of infection of animals with a viral clone will be important for investigating viral determinants of pathogenesis and monitoring sequence changes in the viral genome in vivo and may find utility as a means of immunization with live-attenuated virus. To test the efficiency of intramuscular (i.m.) injection of cloned proviral plasmid DNA for establishing feline immunodeficiency virus (FIV) infection in specific pathogen-free (SPF) cats, groups of cats were inoculated by the i.m. route with 300, 100, or 30 micrograms of plasmid DNA containing the infectious molecular clone, FIV-pPPR. A fourth group of cats was inoculated intradermally with 30 micrograms of FIV-pPPR plasmid DNA. For comparison, a fifth group received 10(3) TCID50 of a live virus stock of FIV-pPPR by intraperitoneal inoculation. Inoculation by i.m. injection with 100 to 300 micrograms of infectious FIV-pPPR proviral DNA produced infection detectable by both antiviral antibody and virus isolation from peripheral blood mononuclear cells. Inoculation by i.m. injection with 30 micrograms of proviral DNA resulted in infection in two of three inoculated cats. Intradermal injection with 30 micrograms of proviral DNA induced infection in one of three cats. Induction of antiviral antibody and viremia was delayed in cats inoculated with 30 micrograms compared to cats inoculated with either 100 or 300 micrograms of proviral DNA. This study indicates that cloned FIV proviral DNA may replace infectious virion preparations as inocula for pathogenesis and immunization studies.