New Insights in HTLV-I Phylogeny by Sequencing and Analyzing the Entire Envelope Gene

Abstract

The HTLV-I envelope plays a major role in the process of target cell infection. It is implied in the recognition of the viral receptor(s), penetration of the viral genetic material, and induction of host immunity to the virus. It is thus important to study the genetic variability of the viral env gene as well as its variation in terms of evolution. In a new approach to these features, we sequenced the entire env gene of 65 HTLV-I isolates originating from Gabon, French Guiana, West Indies, and Iran, such isolates representing all major HTLVI phylums but the Australo-Melanesian one. The sequences obtained and all PTLV-I (HTLV-I and STLV-I) env sequences available in the literature were analyzed. Phylogenetic studies using different algorithms (minimum evolution, neighbor joining, maximum parsimony, and maximum likelihood) gave the same clear-cut results. Newly sequenced HTLV-I isolates described in this report allocated in three well-defined subtypes: Cosmopolitan, Central African, and a new distinct one that we termed "Maroni" subtype (present in the Maroni Basin, French Guiana, and West Indies). Clearly, the most divergent PTLV-I strains present in Asia- Australo-Melanesia as well as African and Asian STLV-I derived from the same node in the phylogenetic tree as isolates of the Central African subtype. In addition, we showed that within each PTLV-I subtype, groups of isolates may be characterized by nonrandom and systematically associated mutations.

A gorilla reservoir for human T-lymphotropic virus type 4

“…The env sequences of this gorilla shared 98% nucleotide identity to STLV-1 from olive baboons ( Papio anubis ), which have a broad geographic distribution, including Cameroon. The 9584Ggo sequence also showed 99% nucleotide identity to HTLV-1 subtype F env sequences from Gabon, 31 which was confirmed by phylogenetic analysis (Figure 6). We consistently obtained STLV-1 env sequences in repeat PCR reactions using dried blood spot DNA from this gorilla.…”

“…The significance of these co-infections is currently unknown, but could lead to genetic recombination as occurs in other dual retroviral infections. The STLV-1 in this gorilla clustered with HTLV-1 subtype F from persons living in Gabon 41 and thus, could be the primate origin of these human infections since the geographic range of G. gorilla extends west from the Congo River into Cameroon, Gabon, Central African Republic and mainland Equatorial Guinea. Gorilla 9584 was from near the southern border of Cameroon, a border which Cameroon also shares with Gabon and primate bushmeat hunting and consumption are known to occur in Gabon, further supporting this possibility.…”