Identification Of Two Novel Human T-Lymphotropic Viruses Among Central African Hunters

Background: HTLV-1 diversity appears to have resulted from multiple cross-species transmissions of STLV-1. However, little is known whether contact between humans and infected nonhuman primates (NHPs) continues to contribute to the emergence of novel HTLVs. Methods: We investigated HTLV diversity among 930 central Africans reporting contact with NHP blood through hunting, butchering, and keeping primate pets. Plasma samples were tested serologically using EIA and WB assays. Sequences from several viral regions were PCR amplified from PBL DNA of WB reactive persons followed by phylogenetic analysis with known PTLVs. Results: Proviral sequences were PCR-amplified from 13 WB reactive persons. Phylogenetic analysis revealed infection of two hunters with novel viruses we designated HTLV-3 and HTLV-4. HTLV-3 falls within the genetic diversity of STLV-3, a virus not seen before in humans. HTLV-4 is distinct and nearly genetically equidistant from all known HTLVs/STLVs and formed of a new phylogenetic lineage. Eleven persons were also infected with a broad diversity of HTLV-1, including STLV-1 from mandrills (n = 3) and other STLV-1 variants (n = 2) not previously seen in humans. Conclusions: We identify in this population two new HTLVs and demonstrate greater HTLV diversity than previously recognized. These findings also suggest that NHP exposure contributes to HTLV emergence.