Suppression of feline immunodeficiency virus replication in vitro by a soluble factor secreted by CD8(+) T lymphocytes

Mitogen-activated lymphoblasts isolated from the blood and lymph nodes, but not the spleen, of domestic cats acutely infected with the Petaluma or Gla sgow, isolates of feline immunodeficiency virus (FIV), suppressed the repli cation of FIV in the MYA-1 T-cell line in a dose-dependent manner. This eff ect was not limited to the homologous isolate of FIV. The suppressor activi ty declined with progression to chronic infection, with lower levels of act ivity detectable only in the lymph nodes. Immunization of domestic cats wit h whole inactivated FIV vaccine elicited profound suppressor activity in bo th the blood and lymph nodes. The suppressor activity was associated with t he CD8(+) T-cell subpopulation, the effect did not appear to be major histo compatibility complex-restricted, and was mediated by a soluble factor(s). This activity may be associated with the control of virus replication durin g both the asymptomatic stages of FIV infection, and in the protective immu nity observed in cats immunized with whole inactivated virus vaccines.