Discovery of a new human T-cell lymphotropic virus (HTLV-3) in Central Africa
- Sara Calattini†1,
- Sébastien Alain Chevalier†1,
- Renan Duprez1,
- Sylviane Bassot1,
- Alain Froment2,
- Renaud Mahieux†1 and
- Antoine Gessain†1Email author
© Calattini et al; licensee BioMed Central Ltd. 2005
Received: 20 April 2005
Accepted: 09 May 2005
Published: 09 May 2005
Human T-cell Leukemia virus type 1 (HTLV-1) and type 2 (HTLV-2) are pathogenic retroviruses that infect humans and cause severe hematological and neurological diseases. Both viruses have simian counterparts (STLV-1 and STLV-2). STLV-3 belongs to a third group of lymphotropic viruses which infect numerous African monkeys species. Among 240 Cameroonian plasma tested for the presence of HTLV-1 and/or HTLV-2 antibodies, 48 scored positive by immunofluorescence. Among those, 27 had indeterminate western-blot pattern. PCR amplification of pol and tax regions, using HTLV-1, -2 and STLV-3 highly conserved primers, demonstrated the presence of a new human retrovirus in one DNA sample. tax (180 bp) and pol (318 bp) phylogenetic analyses demonstrated the strong relationships between the novel human strain (Pyl43) and STLV-3 isolates from Cameroon. The virus, that we tentatively named HTLV-3, originated from a 62 years old Bakola Pygmy living in a remote settlement in the rain forest of Southern Cameroon. The plasma was reactive on MT2 cells but was negative on C19 cells. The HTLV 2.4 western-blot exhibited a strong reactivity to p19 and a faint one to MTA-1. On the INNO-LIA strip, it reacted faintly with the generic p19 (I/II), but strongly to the generic gp46 (I/II) and to the specific HTLV-2 gp46. The molecular relationships between Pyl43 and STLV-3 are thus not paralleled by the serological results, as most of the STLV-3 infected monkeys have an "HTLV-2 like" WB pattern. In the context of the multiple interspecies transmissions which occurred in the past, and led to the present-day distribution of the PTLV-1, it is thus very tempting to speculate that this newly discovered human retrovirus HTLV-3 might be widespread, at least in the African continent.
Three types of Primate T-cell lymphotropic viruses (PTLVs) have been discovered so far in primates . While two of them i.e. PTLV-1 and PTLV-2 include human (HTLV-1, HTLV-2) and simian (STLV-1, STLV-2) viruses, the third type (STLV-3) consists only, so far, of simian strains. Sequence comparisons of STLV-3 proviruses indicated that these strains are highly divergent from HTLV-1 (60% nucleotide similarity), HTLV-2 (62%), or STLV-2 (62%) prototype sequences. In all phylogenetic analyses, STLV-3 viruses cluster in a highly supported group, indicating an evolutionary lineage independent from PTLV-1 and PTLV-2. Nevertheless, STLV-3 lineage is composed of at least three subtypes that are corresponding more or less to the geographical origin of the virus (East, West or Central Africa) [2–9]. Most of the viruses belonging to the PTLV-1 type cannot be separated into distinct phylogenetic lineages according to their species of origin. Their intermixing has therefore been inferred as an evidence for past or recent interspecies transmission episodes. The hypothesis of viral transmission from monkeys to humans is supported by an increasing number of observations . Thus, it has been proposed that HTLV strains related to STLV-3 might infect human populations living in areas where STLV-3 is present.
Cameroon has a remarkable diversity of retroviruses. All the subtypes of HIV-1 group M (A to H) are present, subtype-recombinant strains co-circulate, and HIV-1 groups O and N have been reported. Besides, HTLV-1 subtypes B and D as well as HTLV-2 type A and B are also present in Cameroonian individuals, while STLV-1 and STLV-3 strains have been isolated from several non-human primates (NHPs) species living in this region [3, 4, 8]. We therefore conducted a study to search for HTLV variants in Cameroonian individuals with HTLV-1/2 indeterminate serology. This survey was approved by both the national (Cameroon Ministry of Health and their National Ethics committee) and local authorities (village chief) with information to each participant. An oral informed consent was obtained from each participant (adults or parents for minors). A series of 240 blood samples was obtained from Bakola (n = 64) and Baka (n = 65) Pygmies, while others (n = 111) were obtained from Bantous (mainly from the Fang, Mvae and Ngumba tribes). All these individuals (117 women and 123 men, mean age 44, range 10–75 years) live in remote villages in the rain forest area of the Southern part of Cameroon.
The 240 plasma were tested at a 1/40 dilution for the presence of HTLV-1/2 antibodies with a highly sensitive immunofluorescence test (IF), that uses MT2 and C19 as HTLV-1 and HTLV-2 viral antigen producing cells respectively. This test also allows the detection of STLV-3 positive samples [4, 5]. The 48 plasma that were IF reactive on MT2, C19 or both, were further tested by western blot (WB HTLV BLOT 2.4; Genelabs Diagnostics, Singapore). Among the 48 samples tested, 4 and 11 WB patterns were very evocative of HTLV-1 and HTLV-2 infection respectively, while 27 exhibited diverse HTLV incomplete patterns, including some HTLV-1 indeterminate gag profile (HGIP). Six samples were WB negative. High-molecular weight DNA was extracted from the 48 blood samples and was first subjected to PCR using human β-globin specific primers, to ensure that DNA was amplifiable. They were then subjected to two series of PCR using degenerated tax and pol primers designed on highly conserved regions that are common to all PTLVs. The tax primers are the following: SCTaxoutse: 5'-CTHTAYGGRTACCCHGTCTACGT-3' and SCTaxoutas: 5'-AGGGGAGBCGAGGGATAAGG-3' corresponding to nucleotides 7279 to 7301 and 7455 to 7474 respectively of the prototype STLV-3PHA969 sequence (GenBank accession number Y07616). The pol primers are SCPOL1outse: 5'-TTAAACCDGARCGCCTCCAGGC-3' (nt 2485 to 2506) SCPOL1outas: 5'-GGDGTDCCYTTRGAGACCCA-3' (nt 3201 to 3220) and SCPOL1inse: 5'-TAYHHAGGRCCAGGMAATAACCC-3' (nt 2556 to 2578).
In conclusion, we have demonstrated in this report the presence of a new human retrovirus in the peripheral blood cells of a Central African native. This virus is closely related to STLV-3. In the context of multiple interspecies transmissions that have occurred in the past and led to the present-day distribution of the PTLV-1 , we suggest that HTLV-3 might be widespread, throughout the African continent. HTLV-3 infection seems to be reflected by an HTLV indeterminate serological WB pattern. This raises an important public health question regarding the effectiveness of the current commercially available screening and confirmation tests for detecting this new HTLV type. Key research priorities are now to investigate the transmission modes of this virus as well as possible pathogenic associations.
Nucleotide accession number
The tax and pol accession number for the sequences determined in this study are: [GenBank:DQ020492, GenBank:DQ020493] respectively.
Wolfe et al. recently reported in an abstract the presence of two novel HTLV viruses . Whether or not these viruses are related to the new strain described here (HTLV-3 Pyl43) remains to be determined by further comparative studies.
List of abbreviations used
Primate T Lymphotropic Viruses
Human T Cell Lymphotropic Virus
Polymerase Chain Reaction
Non Human Primates
HTLV Gag Indeterminate Profile
This work was supported by a grant from l'Association de Recherche sur le Cancer (ARC # 4781) to RM and fellowships from le Ministère de la Recherche to SAC and Virus Cancer Prévention association to SC. RM is supported by INSERM. SC and SAC contributed equally to the laboratory work. RM and AG share senior authorship on this work. We also thank Dr Timothy Stinear for his critical comments.
- Slattery JP, Franchini G, Gessain A: Genomic evolution, patterns of global dissemination, and interspecies transmission of human and simian T-cell leukemia/lymphotropic viruses. Genome Res. 1999, 9: 525-540.PubMedGoogle Scholar
- Goubau P, Van Brussel M, Vandamme AM, Liu HF, Desmyter J: A primate T-lymphotropic virus, PTLV-L, different from human T-lymphotropic viruses types I and II, in a wild-caught baboon (Papio hamadryas). Proc Natl Acad Sci U S A. 1994, 91: 2848-2852.PubMed CentralView ArticlePubMedGoogle Scholar
- Courgnaud V, Van Dooren S, Liegeois F, Pourrut X, Abela B, Loul S, Mpoudi-Ngole E, Vandamme A, Delaporte E, Peeters M: 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). J Virol. 2004, 78: 4700-4709. 10.1128/JVI.78.9.4700-4709.2004.PubMed CentralView ArticlePubMedGoogle Scholar
- Meertens L, Mahieux R, Mauclere P, Lewis J, Gessain A: Complete sequence of a novel highly divergent simian T-cell lymphotropic virus from wild-caught red-capped mangabeys (Cercocebus torquatus) from Cameroon: a new primate T-lymphotropic virus type 3 subtype. J Virol. 2002, 76: 259-268. 10.1128/JVI.76.1.259-268.2002.PubMed CentralView ArticlePubMedGoogle Scholar
- Meertens L, Gessain A: Divergent simian T-cell lymphotropic virus type 3 (STLV-3) in wild-caught Papio hamadryas papio from Senegal: widespread distribution of STLV-3 in Africa. J Virol. 2003, 77: 782-789. 10.1128/JVI.77.1.782-789.2003.PubMed CentralView ArticlePubMedGoogle Scholar
- Meertens L, Shanmugam V, Gessain A, Beer BE, Tooze Z, Heneine W, Switzer WM: A novel, divergent simian T-cell lymphotropic virus type 3 in a wild-caught red-capped mangabey (Cercocebus torquatus torquatus) from Nigeria. J Gen Virol. 2003, 84: 2723-2727. 10.1099/vir.0.19253-0.View ArticlePubMedGoogle Scholar
- Takemura T, Yamashita M, Shimada MK, Ohkura S, Shotake T, Ikeda M, Miura T, Hayami M: High prevalence of simian T-lymphotropic virus type L in wild ethiopian baboons. J Virol. 2002, 76: 1642-1648. 10.1128/JVI.76.4.1642-1648.2002.PubMed CentralView ArticlePubMedGoogle Scholar
- Van Dooren S, Salemi M, Pourrut X, Peeters M, Delaporte E, Van Ranst M, Vandamme AM: Evidence for a second simian T-cell lymphotropic virus type 3 in Cercopithecus nictitans from Cameroon. J Virol. 2001, 75: 11939-11941. 10.1128/JVI.75.23.11939-11941.2001.PubMed CentralView ArticlePubMedGoogle Scholar
- Van Dooren S, Shanmugam V, Bhullar V, Parekh B, Vandamme AM, Heneine W, Switzer WM: Identification in gelada baboons (Theropithecus gelada) of a distinct simian T-cell lymphotropic virus type 3 with a broad range of Western blot reactivity. J Gen Virol. 2004, 85: 507-519. 10.1099/vir.0.19630-0.View ArticlePubMedGoogle Scholar
- Mahieux R, Pecon-Slattery J, Gessain A: Molecular characterization and phylogenetic analyses of a new, highly divergent simian T-cell lymphotropic virus type 1 (STLV-1marc1) in Macaca arctoides. J Virol. 1997, 71: 6253-6258.PubMed CentralPubMedGoogle Scholar
- Varma M, Rudolph DL, Knuchel M, Switzer WM, Hadlock KG, Velligan M, Chan L, Foung SK, Lal RB: Enhanced specificity of truncated transmembrane protein for serologic confirmation of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by western blot (immunoblot) assay containing recombinant envelope glycoproteins. J Clin Microbiol. 1995, 33: 3239-3244.PubMed CentralPubMedGoogle Scholar
- Zrein M, Louwagie J, Boeykens H, Govers L, Hendrickx G, Bosman F, Sablon E, Demarquilly C, Boniface M, Saman E: Assessment of a new immunoassay for serological confirmation and discrimination of human T-cell lymphotropic virus infections. Clin Diagn Lab Immunol. 1998, 5: 45-49.PubMed CentralPubMedGoogle Scholar
- Wolfe N, Heneine W, Carr JK, Garcia A, Shanmugam V, Tamoufe U, Torimiro J, Prosser A, LeBreton M, Mpoudi-Ngole E, Mccutchan F, Birx DL, Folks T, Burke DS, Switzer WM: Discovery of New Human T-lymphotropic Viruses Reveals Frequent and Ongoing Zoonotic Retrovirus Introductions. Conference on Retroviruses and Opportunistic Infections. 2005, http://www.retroconference.org/2005/cd/Abstracts/25714.htm. Boston, Massachusetts, USAGoogle Scholar
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