Human T-Lymphotropic virus type 1 (HTLV-1): a new subgroup within the cosmopolitan subtype.

EIRIN ME, JONES L, BERINI C, DILERNIA D, DELFINO C, BIGLIONE M

Leuven

Conferencia; 15th International Conference on Human Retrovirology: HTLV and related viruses; 2011

The International Retrovirology Association

IntroductionHTLV-1 is classified in seven subtypes (a-g) most ofthem restricted to specific regions (b-e), while the Cosmopolitansubtype (a) is worldwide distributed. Cosmopolitansubtype has experimented a degree of moleculardiversity giving rise to five subgroups: Transcontinental(A), Japanese (B), West African (C), North African (D)and Black Peruvian (E).Objectiveto confirm the classification of four HTLV-1 highlydivergent strains as a new subgroup within the Cosmopolitansubtype.Materials and methodsLTR sequences from 65 HTLV-1 positive Buenos Airesresidents were retrospectively studied. Phylogeny of LTRregion was studied by three different methods (ML, MPand NJ). A similitude index (SI) was estimated as themean number of nucleotide substitutions from eachsubgroup (intra-subgroup) or between sequences from agiven subgroup against all from other subgroups (intersubgroup)(script described in the R Statistical PackageLanguage http://www.R-project.org).ResultsThe three phylogenetic methods were consistent, showinga well supported monophyletic clade that includedtwo Peruvian sequences clustering with two references(Bl3 from Peru and Br4 from Brazil) previouslydescribed as divergent, branching off all known subgroups(82% bootstrap, ML). The similitude analysisshowed a SI intra-subgroup similar to those obtainedfor A-D subgroups and a SI inter-subgroup similar tosubgroups A and D. Following nomenclature, it wasnamed subgroup F.ConclusionsThis study confirms the existence of a highly divergentmonophyletic clade within the Cosmopolitan subtypecomposed of sequences from Peruvian and Brazilianindividuals and suggest that more studies should be performedin this South-American area where the last subgroups(E and F) has been detected.