Simian T-cell leukemia virus (STLV) infection in wild primate populations in Cameroon: evidence for dual STLV type 1 and type 3 infection in agile mangabeys (Cercocebus agilis)

Abstract

Three types of human T-cell leukemia virus (HTLV)-simian T-cell leukemia virus (STLV) (collectively called primate T-cell leukemia viruses [PTLVs]) have been characterized, with evidence for zoonotic origin from primates for HTLV type 1 (HTLV-1) and HTLV-2 in Africa. To assess human exposure to STLVs in western Central Africa, we screened for STLV infection in primates hunted in the rain forests of Cameroon. Blood was obtained from 524 animals representing 18 different species. All the animals were wild caught between 1999 and 2002; 328 animals were sampled as bush meat and 196 were pets. Overall, 59 (11.2%) of the primates had antibodies cross-reacting with HTLV-1 and/or HTLV-2 antigens; HTLV-1 infection was confirmed in 37 animals, HTLV-2 infection was confirmed in 9, dual HTLV-1 and HTLV-2 infection was confirmed in 10, and results for 3 animals were indeterminate. Prevalences of infection were significantly lower in pets than in bush meat, 1.5 versus 17.0%, respectively. Discriminatory PCRs identified STLV-1, STLV-3, and STLV-1 and STLV-3 in HTLV-1-, HTLV-2-, and HTLV-1- and HTLV-2-cross-reactive samples, respectively. We identified for the first time STLV-1 sequences in mustached monkeys (Cercopithecus cephus), talapoins (Miopithecus ogouensis), and gorillas (Gorilla gorilla) and confirmed STLV-1 infection in mandrills, African green monkeys, agile mangabeys, and crested mona and greater spot-nosed monkeys. STLV-1 long terminal repeat (LTR) and env sequences revealed that the strains belonged to different PTLV-1 subtypes. A high prevalence of PTLV infection was observed among agile mangabeys (Cercocebus agilis); 89% of bush meat was infected with STLV. Cocirculation of STLV-1 and STLV-3 and STLV-1-STLV-3 coinfections were identified among the agile mangabeys. Phylogenetic analyses of partial LTR sequences indicated that the agile mangabey STLV-3 strains were more related to the STLV-3 CTO604 strain isolated from a red-capped mangabey (Cercocebus torquatus) from Cameroon than to the STLV-3 PH969 strain from an Eritrean baboon or the PPA-F3 strain from a baboon in Senegal. Our study documents for the first time that (i) a substantial proportion of wild-living monkeys in Cameroon is STLV infected, (ii) STLV-1 and STLV-3 cocirculate in the same primate species, (iii) coinfection with STLV-1 and STLV-3 occurs in agile mangabeys, and (iv) humans are exposed to different STLV-1 and STLV-3 subtypes through handling primates as bush meat.

FIG. 1.

Detection of HTLV-1- and HTLV-2-cross-reactive antibodies in sera from agile mangabeys (Cercocebus agilis) by using a line immunoassay (INNO-LIA HTLV confirmation; Innogenetics). The HTLV antigens include recombinant proteins and synthetic peptides which are either common to HTLV-1 and HTLV-2 or specific to one of the two viruses. The first three control lines contain human IgG in different concentrations and are followed by four confirmation lines (two gag and two env HTLV-1 and HTLV-2 antigen lines) and three discriminatory lines (two gag HTLV-1 peptides and one env HTLV-2 peptide) at the bottom of the strip. Plasma samples from HTLV-1- and HTLV-2-negative and -positive individuals are shown as controls on the left. Lanes labeled 01-CM1040 and 01-CM1129 represent STLV-1-seropostive Cercocebus agilis; lane 01-CM1053 represents STLV-3-seropositive Cercocebus agilis, and lanes 01-CM1038 and 01-CM1106 represent STLV-1- and STLV-3-seropositive Cercocebus agilis. Lane 01-CM1003 represents an example of plasma with indeterminate serology.

FIG. 2.

PAUP* NJ tree of a 219-bp tax-rex fragment including sequences from reference strains of each PTLV type and subtype with the bootstrap values (in percentages) and P values (**, P < 0.001; *, P < 0.05) noted on the branches.

FIG. 3.

Phylogenetic relationships among new STLV-1 strains from Cercocebus agilis, Cercopithecus cephus, Gorilla gorilla, Mandrillus sphinx, Miopithecus ogouensis, and Cercopithecus pogonias and known STLV-1 and HTLV-1 strains from the different subtypes. Phylogenetic relationships were determined using LTR (A) and env (B) sequences as described in Materials and Methods. The numbers along the branches are the bootstrap values (in percentages), and two asterisks indicate that the branch has a P value of <0.001 in the ML analysis. Horizontal branch lengths are drawn to scale.

FIG. 3.

Phylogenetic relationships among new STLV-1 strains from Cercocebus agilis, Cercopithecus cephus, Gorilla gorilla, Mandrillus sphinx, Miopithecus ogouensis, and Cercopithecus pogonias and known STLV-1 and HTLV-1 strains from the different subtypes. Phylogenetic relationships were determined using LTR (A) and env (B) sequences as described in Materials and Methods. The numbers along the branches are the bootstrap values (in percentages), and two asterisks indicate that the branch has a P value of <0.001 in the ML analysis. Horizontal branch lengths are drawn to scale.

FIG. 4.

Phylogenetic relationships among new STLV-3 strains from Cercocebus agilis and known STLV-3 strains from different primate species. Phylogenetic relationships were determined using LTR sequences as described in Materials and Methods. The bootstrap values (in percentages) and P values (**, P < 0.001; *, P < 0.05) are indicated on the branches.