CD8+ Thymic Lymphocytes Express Reduced Levels of CD8β and Increased Interferon γ in Cats Perinatally Infected with the JSY3 Molecular Clone of Feline Immunodeficiency Virus

Biological isolates of feline immunodeficiency virus (FIV) cause a relative expansion of activated single-positive CD8+ (SP CD8+) lymphocytes within the thymus of infected cats. In this study, thymic SP CD8+ lymphocytes were analyzed from cats inoculated as neonates with a pathogenic molecular clone of FIV, JSY3, which was previously derived from the wild-type biological isolate FIVNCSU-1 (NCSU-1). Four cats were inoculated intraperitoneally with NCSU-1 and compared with 11 cats inoculated with JSY3. Five control cats matched in litter and age were administered an intraperitoneal sham inoculum. Between 12 and 16 weeks postinoculation, interferon-γ (IFN-γ) mRNA was quantified by RT-PCR in freshly isolated thymocytes and peripheral blood mononuclear cells (PBMCs). The quantity of IFN-γ mRNA was increased more than 10-fold in thymocytes and PBMCs of 13 of 13 FIV-inoculated cats as compared with the sham-inoculated controls. IFN-γ mRNA coenriched with magnetically sorted CD8+ PBMCs and single-positive (SP) CD...