Phenotypic and functional characteristics of FIV infection in the bone marrow stroma

Human (HIV) and feline (FIV) immunodeficiency virus has been reported to infect bone marrow (BM) and stroma, followed by a loss in normal hematopoiesis. However, the magnitude and nature of HIV and FIV pathogenesis of the BM/stromal network are still unclear. In the current studies, pathogenesis of stromal cells was evaluated using the FIV model. Fourteen specific-pathogen-free cats inoculated with the four different strains (FIV(UK8), FIV(Bang), FIV(Shi), or FIV(Pet)) were monitored for FIV infection in the peripheral blood mononuclear cells (PBMC), BM cells, and stromal cells. All inoculated cats became positive for FIV in the PBMC by 7 weeks p.i. and 13 of 14 cats had FIV in the BM cells by 7-13 weeks p.i. FIV was detected in macrophages and stromal fibroblasts from FIV(UK8)-, FIV(Bang)-, and FIV(Shi)-infected cats but not from FIV(Pet)-infected cats and only transiently in cells from FIV(Shi)-infected cats. The ability of the supernatants from FIV-infected stromal cells to sustain the growth of uninfected BM cells was decreased 35-46% when compared to the supernatants from uninfected stromal cells. These results suggest that the FIV infection of the stroma alters normal hematopoietic function(s) and that the infected stromal cells can also serve as a reservoir for FIV infection.