ISOLATION OF A NOVEL SIMIAN T-CELL LYMPHOTROPIC VIRUS FROM PAN-PANISCUS THAT IS DISTANTLY RELATED TO THE HUMAN T-CELL LEUKEMIA LYMPHOTROPICVIRUS TYPE-I AND TYPE-II

An unusual serological profile against human T-cell leukemia/lymphotro pic virus type I and II (HTLV-I and -II) proteins was reported in seve ral human Pygmy tribes in Zaire and Cameroon with serum antibodies rea ctive with gp21 and p24. Here we describe a similar pattern of serum a ntibodies in a colony of captive pygmy chimpanzees and the isolation o f a novel retrovirus, simian T-cell lymphotropic virus from Pan panisc us (STLV(pan-p)), from the peripheral blood mononuclear cells of sever al seropositive animals. Cocultures of peripheral blood mononuclear ce lls from three seropositive pygmy chimpanzees with human cord blood mo nonuclear cells led to the expression of an HTLV-I- and HTLV-II-relate d virus initially demonstrated by electron microscopy. Furthermore, se veral of these cocultures became immortalized T-cell lines expressing the CD4(+) CD8(+) DR(+) phenotype of mature activated T cells. Souther n blotting and DNA sequencing of a PCR fragment of viral DNA from thes e cell cultures demonstrated a distant evolutionary relationship of th ese viruses to HTLV-I and -II and distinct from the known STLV isolate s. We designated this virus STLV(pan-p). A genealogical analysis of th e captive pygmy chimpanzees colony, originated from wild caught animal s, revealed a prevalence of seropositive offspring from infected mothe rs, as also observed with HTLVs. The presence in this old African Grea t Ape species of a virus which is genetically quite distinct from HTLV -I and -II could provide new insights in the phylogenesis of STLVs and HTLVs and be instrumental in the discovery of related human viruses.