Central and peripheral reservoirs of feline immunodeficiency virus in cats: a review.
The lymphotropic lentiviruses feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV) enter cells by sequential interaction with primary receptors CD134 or CD4, respectively, and subsequently with chemokine receptors. The host-cell range for FIV is broader than that for HIV, but whether this is a function of receptor expression is unknown. Lack of reagents specific to feline molecules has limited detection and analysis of receptors and their interaction with viral components. Here, the expression of CD134 and CXCR4 on feline T and B lymphocytes, dendritic cells (DCs) and macrophages was examined and the kinetics of FIV replication were assessed. Quantification of CD134 mRNA by real-time PCR indicated expression in all leukocytes, with significantly more transcripts in CD4(+) lymphocytes than in other leukocytes. Antibodies against human CD134 bound inconsistently to feline leukocytes. CXCR4 was detected with antibody clone 12G5 on the surface of monocyte-derived cells only, but gene transcripts were present in all cells, with the highest copy number in lymphocytes. CXCR4 expression decreased and CD134 expression increased with cell activation in lymphocytes. A subtype B biological isolate of FIV infected DCs, macrophages and lymphocytes, with the highest replication in CD4(+) lymphocytes, whilst cloned FIV P14 infected all cells, but replicated less efficiently. Although viral replication was lower in DCs and macrophages than in lymphocytes, DCs expressed specific receptors and were infected productively with FIV, as indicated by viral ultrastructure and DNA detection. These results may implicate altered function of DCs in the induction of specific immunity against FIV.