TEMPO AND MODE OF PTLV EVOLUTION

Abstract

O-44 We performed phylogenetic and molecular clock analyses to unravel the divergence times and transmission pathways of human and simian T-cell lymphotropic viruses (HTLV/STLV). Three HTLV/STLV (together PTLV) types have been characterized: PTLV-I found in humans and most old world simian species, PTLV-II found in humans and pygmy chimpanzees and STLV-L only found in baboons. Within PTLV-I, the oldest phylogenetic lineages are found in Asian macaques. The Melanesian/Australian HTLV-I subtype c most probably originated through interspecies transmission from Indonesian macaques to humans migrating to these islands around 30 000 to 60 000 years ago. Using these dates, the transmission of Asian PTLV-I to African simians and humans, resulting in an explosive spread of this virus in Africa, could be dated around 10 000 to 20 000 years ago. The HTLV-I subtypes Ia, Ib, Id, Ie and If have a separate African simian origin, dating from less than 300 years ago (subtype If originating from Mandrillus sphinx) up to 10 000 years ago (subtype Ia, Ib, Id and Ie). The cosmopolitan HTLV-Ia was spread over the world due to post-Columbian human migrations. Within PTLV-II, human and simian viruses are phylogenetically well separated. Both clades have an African origin. Three HTLV-II subtypes exist, HTLV-IId is found in Efe pygmies from Congo and HTLV-IIa and IIb are found in Amerindian tribes, drug users and a few Africans. Most probably HTLV-IIa and IIb were brought to America as a result of the migrations of the human host over the Bering strait, 10 000 to 35 000 years ago. Using this date, it was calculated that STLV-II, originated 100 000 to 400 000 years ago, long after the speciation of pygmy chimpanzees and humans, implying that both STLV-II and HTLV-II originated from an interspecies transmission. HTLV-IId separated from the other HTLV-II subtypes 20 000 to 70 000 years ago. HTLV-IIa and IIb in drug users seem to evolve 50 to 200 times faster than in Amerindians and pygmies. Using these divergence times and BLV as outgroup, we calculated that the origin of PTLV was either in Africa or in Asia around 300 000 to 1 million years ago, while STLV-L and PTLV-II separated from each other in Africa very shortly after (280 000 to 980 000 years ago).