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Tracing the Pos-Columbian origin of the
Brazilian HTLV-1 strains using the viral and host genetic markers
Alcantara L.C.J. 1,2, Galvão-Castro B. 1,2.
1 Escola Bahiana de Medicina e Saúde Pública/Fundação
Bahiana para Desenvolvimento das Ciências – Salvador, Bahia, Brasil; 2
Laboratório Avançado de Saúde Pública, Centro de Pesquisas Gonçalo Moniz,
Fundação Oswaldo Cruz, Salvador, Bahia, Brasil.
lalcan@cpqgm.fiocruz.br
The endemicity of the HTLV-1 suggests the
possibility of this virus to have infected human populations since thousand of
years. The presence of HTLV-1 infected Efe Mbuti Pygmies and the separation of
the African and non-Africans human populations being estimated to have occurred
75,000-287,000 years ago had shown that this genic flow occurred normally from
pygmies to the neighboring populations. With the HTLV-1 endemicity among the
ameridians, we could conclude that this vírus was also present in the American
continent a long time ago, and it was brougth, probably, to the American
continent around 15,000-35,000 years, during one or more Asian infected people
migrations by the Bering Streit. In the last years, the use of the phylogenetic
analysis of the HTLV-1 LTR region has shown seven genetic subtypes: a; b; c; d;
e; f and g. The a subtype is divided into five subgroups: Transcontinental (A),
Japanese (B), West African (C), North African (D), and Black Peruvian (E). Only
the strains of the A subgroup have been isolated from different endemic and
no-endemics areas throughout the American continent. These strains must have
been carried out of Africa by their human host either during the pre-Columbian
ancient human migrations out of Africa, or possibly during the pos-Columbian
slave trade between the XVI and XIX centuries. The strains of the Subgroup C
were identified in the American places like the Caribbean area and French
Guiana, excluding Brazil, where most people were brought from the West African
continent, during the slave trade. Our analysis, studing the virus and host
genetic markers, suggest that the Brazilian HTLV-1 strains could be originated
from South African regions. Although historical date shows West Africa as the
common region from where Africans were brought to Brazil, there are also
evidences that Africans were also brought from other regions of the South
African Continent. In our phylogenetic analysis, the South African cluster is
characterized by low levels of diversity in the LTR region (0.5%), suggesting a
recent introduction of HTLV-1 in Brazil. This introduction is most
probably the result of Bantu population migration in the last 3,000
years, or due to the recent migrations (less than 300 years) to the
gold mines in South Africa. The heterogeneity of HTLV-1 distribution
shows little evidence of adaptation or natural selection, providing
this virus as an excellent evolutionary model, which may lead to new
insights for controlling the spread and genetic evolution of this
important human pathogens.
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