Detection and Role of Feline Apolipoprotein B mRNA-editing Enzyme Catalytic Polypeptide Subunit 3G-Like Protein in Feline Cells and Tissues

The innate host defence system is designed to resist pathogenic microorganism infections. Despite the compelling scientific evidence, our understanding of the full potential of the mechanism is still unclear due to the complex interactions between hosts and invaders. We previously reported latency in cat mucosal infected with low-dose cell-associated feline immunodeficiency virus (102 and 103 infected cells). Here we investigated the expression of Apolipoprotein B mRNA-editing enzyme catalytic subunit 3G (APOBEC3G or A3G) in feline cells and tissues and whether its presence antagonizes the viral pre-integration complex resulting in partial or complete FIV latency. Total RNA and protein lysates were collected from cell lines, blood, and tissue samples. Real-time RT-PCR and western blot assays were used to quantify fA3G-like protein in cats exposed to high versus low-dose cell-associated FIV. We consistently detected fA3G-like protein in mock T-cell lines (E-CD4+, MYA-1, Crandell feline kidney cells) and primary bone marrow-derived macrophages with variable expressions in feline peripheral blood mononuclear cells (PBMC). In addition, the fA3G-like protein was found to interact with FIV group-specific antigen (Gag) protein through immunoprecipitation assays. The protein expression was utterly abrogated following FIV infection. However, in lytic FIV infection (in vivo), fA3G-like protein decreased in early post-infection, whereas latently infected cats showed stable expression. These data are the first report of the fA3G-like protein expression in felines and its abrogation in lytic but not in latent FIV-infected individuals. These results might provide new insight into the role of fA3G-like protein in the host defence mechanism against retrovirus infections.