EVIDENCE OF FELINE IMMUNODEFICIENCY VIRUS-REPLICATION IN CULTURED KUPFFER CELLS

Objective: To determine if cultured feline Kupffer cells (KC) are as p ermissive for feline immunodeficiency virus (FIV) as cultured human li ver macrophages are for HIV. Two types of infection likely to be relev ant to the in vivo situation were used. KC were infected with either f ree virus or autologous infected peripheral blood mononuclear cells (P BMC). Methods: Feline KC were isolated by centrifugal elutriation from collagenase-perfused liver; cultured cells were characterized by thei r morphological appearance and their erythrophagocytotic properties. A fter infection, viral replication was measured by enzyme-linked immuno sorbent assay, reverse transcriptase activity, immunofluorescence assa y, in situ hybridization and electron microscopic observations. Result s: Three days after isolation, 85% of cultured KC were able to interna lize red blood cells; 45% were CD4-positive and 65% expressed a 24 kD protein thought to be a receptor for FIV (CD9). After the addition of autologous infected PBMC or cell-free supernatant of chronically infec ted IRC4 cells to KC cultures, a peak of viral replication was detecte d at day 28. Antigen revealed by immunofluorescence assay was present in only 0.4%, and viral RNA was detected by in situ hybridization in 2 % of the infected cells. Conclusions: FIV can replicate in cultured fe line KC without inducing any cytopathic effect, which suggests that th ese cells may play a role in the physiopathology of FIV infection.