Human T lymphotropic virus type 1 subtype C melanesian genetic variants of the Vanuatu Archipelago and Solomon Islands share a common ancestor.
BACKGROUND
Melanesia is endemic for human T lymphotropic virus type 1 (HTLV-1) subtype C. In 2005, we identified 4 infected women from Ambae Island, Vanuatu. Subsequently, 4247 Ni-Vanuatu originating from 18 islands were enrolled to define HTLV-1 epidemiological determinants and to characterize the viral strains molecularly.


METHODS
Plasma from 1074 males and 3173 females were screened for HTLV-1/2 antibodies by particle agglutination (PA) and an immunofluorescence assay (IFA). Positive and/or borderline samples were then tested by a Western blot (WB) confirmatory assay. DNAs were amplified to obtain a 522-bp env gene fragment. Phylogenetic and molecular-clock analyses were performed.


RESULTS
Of 4247 samples, 762 were positive and/or borderline by IFA/PA, and 26 of them were confirmed to be HTLV-1 positive by WB. The overall HTLV-1 seroprevalence was 0.62%. Viral transmission was found within families of infected index case patients. A geographic heterogeneity of HTLV-1 seroprevalence was observed among the islands. All 41 of the new env sequences belonged to HTLV-1 subtype C. Phylogenetic and molecular-clock analyses suggested that Ni-Vanuatu and Solomon Islander strains emerged from a common ancestor ~10,000 years ago.


CONCLUSIONS
The Vanuatu archipelago is endemic for HTLV-1 with a diversity of subtype C variants. These strains were probably introduced into Vanuatu during ancient migration of the original settlers a few thousand years ago.
Cassar
Olivier
O
Laboratoire d'Epidemiologie Moleculaire, Institut Pasteur de Nouvelle-Caledonie, Noumea, France.
Capuano
Corinne
C
Bassot
Sylviane
S
Charavay
Françoise
F
Duprez
Renan
R
Afonso
Philippe V
PV
Abel
Myriam
M
Walter
Helene
H
Mera
Woreka
W
Martin
Paul M V
PM
Chungue
Eliane
E
Gessain
Antoine
A
D000293:Adolescent; D000328:Adult; D000371:Agglutination; D005075:Biological Evolution; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005455:Fluorescent Antibody Technique; D015686:Gene Products, env / Q000235:genetics; D014644:Genetic Variation; D015481:HTLV-I Antibodies / Q000097:blood*; D015490:HTLV-I Infections / Q000453:epidemiology*; D015368:Human T-lymphotropic virus 1 / Q000145:classification / Q000235:genetics* / Q000276:immunology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D018445:Infectious Disease Transmission, Vertical; D008297:Male; D008542:Melanesia / Q000453:epidemiology; D008875:Middle Aged; D017720:Molecular Epidemiology; D010375:Pedigree; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012424:Rural Population; D016036:Seroepidemiologic Studies; D013045:Species Specificity; D009514:Vanuatu / Q000453:epidemiology
D015686:Gene Products, env; D015481:HTLV-I Antibodies