Prevalence and Phylogenetic Analysis of HTLV–I Isolates in Cameroon, Including Those of the Baka Pygmy

Our previous analysis of an HTLV–I isolate (CMR229) from a Cameroonian Pygmy demonstrated that the isolate is distinct from typical HTLV–ls of the “Central African group,” which has a close similarity to HTLV–I–related simian viruses (STLV–I) in Africa. In this study, we analyzed six new HTLV–ls from Cameroon consisting of three isolates from the Pygmy and three from the Bantu to examine further the genetic features of HTLV–I in Cameroon, especially in the Pygmy. A phylogenetic tree based on the long terminal repeats (LTR) region showed that all the new HTLV–ls belong to the Central African group. On the other hand, an env–based analysis of CMR229 confirmed the previous finding derived from LTR–based analysis that CMR229 has a similarity to African STLV–Is, but is distinct from the typical Central African group of HTLV–I. This suggests that multiple interspecies transmissions from non–human primates to humans have occurred in Central Africa, resulting in the presence of two distinct HTLV–I strains in this area. In addition, it seems likely that the Pygmy harbors the heterogeneous HTLV–I strains from which the main HTLV–I population spread into the Bantu.