Simian T-cell lymphotropic virus type 1 from Mandrillus sphinx as a simian counterpart of human T-cell lymphotropic virus type 1 subtype D

Abstract

A recent serological and molecular survey of a semifree-ranging colony of mandrills (Mandrillus sphinx) living in Gabon, central Africa, indicated that 6 of 102 animals, all males, were infected with simian T-cell lymphotropic virus type 1 (STLV-1). These animals naturally live in the same forest area as do human inhabitants (mostly Pygmies) who are infected by the recently described human T-cell lymphotropic virus type 1 (HTLV-1) subtype D. We therefore investigated whether these mandrills were infected with an STLV-1 related to HTLV-1 subtype D. Nucleotide and/or amino acid sequence analyses of complete or partial long terminal repeat (LTR), env, and rex regions showed that HTLV-1 subtype D-specific mutations were found in three of four STLV-1-infected mandrills, while the remaining monkey was infected by a different STLV-1 subtype. Phylogenetic studies conducted on the LTR as well as on the env gp21 region showed that these three new STLV-1 strains from mandrills fall in the same monophyletic clade, supported by high bootstrap values, as do the sequences of HTLV-1 subtype D. These data show, for the first time, the presence of the same subtype of primate T-cell lymphotropic virus type 1 in humans and wild-caught monkeys originating from the same geographical area. This strongly supports the hypothesis that mandrills are the natural reservoir of HTLV-1 subtype D, although the possibility that another monkey species living in the same area could be the original reservoir of both human and mandrill viruses cannot be excluded. Due to the quasi-identity of both human and monkey viruses, interspecies transmission episodes leading to such a clade may have occurred recently.

FIG. 1

Sequence alignment of 79 amino acids corresponding to a fragment of the p27/rex protein obtained for two African HTLV-1 subtype D variants (H2-3 and 230101), five mandrill STLV-1 strains (Mnd7, Mnd9, Mnd13, Mnd15, and Mnd18), and representative strains of all other known HTLV-1 subtypes, i.e., subtypes A (strain ATK), B (strain EL), and C (strain Mel5).

FIG. 2

LTR nucleotide sequence alignment of two complete (Mnd9 and Mnd13) and two partial (Mnd15 and Mnd18) STLV-1 strains from mandrills, two other prototypes of African STLV-1 strains (STLVAG and STLVCH), two HTLV-1 subtype B strains from Pygmies (H24 and 12503), and all three partial or complete HTLV-1 subtype D LTR sequences available (H2-3, Pyg19, and CMR229), obtained with the CLUSTAL W program and minimal manual editing. Arrows indicate HTLV-1–STLV-1 subtype D-specific mutations. Dots indicate sequence identity with HTLV-1 strain ATK.

FIG. 2

LTR nucleotide sequence alignment of two complete (Mnd9 and Mnd13) and two partial (Mnd15 and Mnd18) STLV-1 strains from mandrills, two other prototypes of African STLV-1 strains (STLVAG and STLVCH), two HTLV-1 subtype B strains from Pygmies (H24 and 12503), and all three partial or complete HTLV-1 subtype D LTR sequences available (H2-3, Pyg19, and CMR229), obtained with the CLUSTAL W program and minimal manual editing. Arrows indicate HTLV-1–STLV-1 subtype D-specific mutations. Dots indicate sequence identity with HTLV-1 strain ATK.

FIG. 3

Phylogenetic tree generated by the NJ method with a 522-bp fragment encompassing most of the gp21 and the carboxyl terminus of gp46 for the four new sequences from mandrill STLV-1 strains Mnd9, Mnd13, Mnd15, and Mnd18, 39 other STLV-1 sequences, and 93 HTLV-1 sequences. An HTLV-2 sequence (MO) was used as an outgroup to root the tree. The numbers at some nodes or branches (bootstrap values) indicate frequencies of occurrence for 500 trees. The bar represents 0.01 nucleotide substitution per site or 1% divergence.

FIG. 4

Phylogenetic tree generated by the NJ method with the complete LTR (755 bp long in the HTLV-1 strain ATK reference sequence) of sequences from two mandrill STLV-1 strains, Mnd9 and Mnd13, 7 other STLV-1 sequences, and 39 HTLV-1 sequences recovered from the databases. The numbers at some nodes or branches (bootstrap values; in italics) indicate frequencies of occurrence for 500 trees. The bar represents 0.01 nucleotide substitution per site or 1% divergence.