Abstract
BackgroundThe recent discoveries of novel human T-lymphotropic virus type 3 (HTLV-3) and highly divergent simian T-lymphotropic virus type 3 (STLV-3) subtype D viruses from two different monkey species in southern Cameroon suggest that the diversity and cross-species transmission of these retroviruses are much greater than currently appreciated.ResultsWe describe here the first full-length sequence of a highly divergent STLV-3d(Cmo8699AB) virus obtained by PCR-based genome walking using DNA from two dried blood spots (DBS) collected from a wild-caught Cercopithecus mona monkey. The genome of STLV-3d(Cmo8699AB) is 8913-bp long and shares only 77% identity to other PTLV-3s. Phylogenetic analyses using Bayesian and maximum likelihood inference clearly show that this highly divergent virus forms an independent lineage with high posterior probability and bootstrap support within the diversity of PTLV-3. Molecular dating of concatenated gag-pol-env-tax sequences inferred a divergence date of about 115,117 years ago for STLV-3d(Cmo8699AB) indicating an ancient origin for this newly identified lineage. Major structural, enzymatic, and regulatory gene regions of STLV-3d(Cmo8699AB) are intact and suggest viral replication and a predicted pathogenic potential comparable to other PTLV-3s.ConclusionWhen taken together, the inferred ancient origin of STLV-3d(Cmo8699AB), the presence of this highly divergent virus in two primate species from the same geographical region, and the ease with which STLVs can be transmitted across species boundaries all suggest that STLV-3d may be more prevalent and widespread. Given the high human exposure to nonhuman primates in this region and the unknown pathogenicity of this divergent PTLV-3, increased surveillance and expanded prevention activities are necessary. Our ability to obtain the complete viral genome from DBS also highlights further the utility of this method for molecular-based epidemiologic studies.
Highlights
The recent discoveries of novel human T-lymphotropic virus type 3 (HTLV-3) and highly divergent simian Tlymphotropic virus type 3 (STLV-3) subtype D viruses from two different monkey species in southern Cameroon suggest that the diversity and cross-species transmission of these retroviruses are much greater than currently appreciated
Comparing the STLV-3d(Cmo8699AB) genome with other prototypical primate T-lymphotropic virus (PTLV) suggests that this virus is highly divergent and has equidistant nucleotide identity from PTLV-1 (62%), PTLV-2 (64%), PTLV-4 (64%), and PTLV-5 (62%)
PTLV-3 from Cameroon (STLV-3(Cto604), HTLV-3(Pyl43), and HTLV-3(Lobak18)) are distantly related to other PTLV-3 subtype B strains from West-Central Africa ((HTLV3(Cam2026ND), STLV-3(NG409), STLV-3(PPAF3), and STLV-3(Lal9589NL) sharing < 90% nucleotide identity. Since both PTLV-3 lineages are presently known as B subtypes, we propose re-naming them as subtypes B1 and B2
Summary
The recent discoveries of novel human T-lymphotropic virus type 3 (HTLV-3) and highly divergent simian Tlymphotropic virus type 3 (STLV-3) subtype D viruses from two different monkey species in southern Cameroon suggest that the diversity and cross-species transmission of these retroviruses are much greater than currently appreciated. Simian and human T-lymphotropic viruses (STLV and HTLV, respectively) are diverse deltaretroviruses consisting of four broad primate T-lymphotropic virus (PTLV) groups. A total of three individuals from southern Cameroon with reported nonhuman primate (NHP) exposures were found to be infected with the recently identified HTLV-3 [1,7,8]. There is currently no evidence that STLV-5 has crossed into humans These recent discoveries of novel HTLVs and STLVs suggest a greater diversity of PTLVs than is currently appreciated
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