THE FELINE LYMPHOID-CELL LINE MBM AND ITS USE FOR FELINE IMMUNODEFICIENCY VIRUS ISOLATION AND QUANTITATION

We report on the development of a feline T lymphoblastoid cell line ob tained from the peripheral blood mononuclear cells (PBMC) of a specifi c pathogen free cat and designated MBM. The cells are pan-T+, CD4(-) a nd CD8(-) and remained interleukin-2-dependent and concanavalin A-depe ndent throughout the period of observation. MBM cells have proved at l east as sensitive as fresh blasts to infection with cell-free stocks o f three feline immunodeficiency virus (FIV) isolates. Upon infection, they exhibit a lytic cytopathic effect. Repeated attempts to establish a chronic infection have failed. Using a limiting cell dilution metho d, it has been shown that MBM cells may be more sensitive than fresh b lasts as substrate for isolating FIV from the PBMC of infected cats. T hese studies have also shown that considerable individual variations e xist in the virus loads present in the PBMC of naturally infected cats , and that load size does not appear to correlate with cat age, clinic al status, CD4/CD8 ratio and titer of serum neutralizing antibody.