RETROVIRAL VECTOR-TRANSDUCED CELLS EXPRESSING THE CORE POLYPROTEIN INDUCE FELINE IMMUNODEFICIENCY VIRUS-SPECIFIC CYTOTOXIC T-LYMPHOCYTES FROM INFECTED CATS

The core polyprotein of feline immunodeficiency virus (FIV) was expres sed in primary feline T-lymphocytes using a retroviral vector. These c ells were used as antigen-presenting stimulator cells (APSC) for the i n vitro induction of cytotoxic T-lymphocytes (CTL) from feline periphe ral blood mononuclear cells (PBMC). CTL from 4 cats chronically infect ed with the Petaluma strain of FIV specifically lysed autologous FIV-i nfected targets in an MHC-restricted manner. The CD8 phenotype of more than 70% of the induced effector cells (97% for cells from one cat) w as consistent with MHC class I-restricted cytotoxicity. In addition, i t was possible to detect low levels of core polyprotein-specific lysis from effector cells of two of the FIV-infected cats. When observed, t he level of lysis, measured as a percentage of specific In-111 release , was lower for the transgenic gag-expressing targets than for FIV-inf ected targets. The difference in killing may reflect the low level of core polyprotein expressed in the transgenic cells compared with FIV-i nfected cells. FIV-specific CTL were not detected in either PBMC stimu lated with cells transduced by a retroviral vector without the FIV gag sequence or PBMC from an uninfected cat stimulated with autologous tr ansgenic APSC. The detection of FIV-specific CTL from infected cats fo llowing stimulation with transgenic APSC suggests a role for retrovira l vectors in determining CTL specific for individual lentiviral protei ns in protective immunity.