Estimating the proportions of different ancestries in admixed populations is very important in population genetics studies, and it is particularly important for detecting population substructure effects in case-control association studies. In this work, a set of 48 ancestry-informative insertion-deletion polymorphisms (INDELs) were selected with the goal of efficiently measuring the proportions of three different ancestries (sub-Saharan African, European, and Native American) in mixed populations. All selected markers can be easily analyzed via multiplex PCR and detected with standard capillary electrophoresis. A total of 593 unrelated individuals representative of European, African, and Native American parental populations were typed, as were 380 individuals from three Brazilian populations with known admixture patterns. As expected, the interethnic admixture estimates show that individuals from southern Brazil present an almost exclusively European ancestry; Afro-descendant communities in the Amazon region, apart from the major African contribution, present some degree of admixture with Europeans and Native Americans; and a sample from Belém, in the northeastern Amazon, shows a significant contribution of the three ethnic groups, although with a greater European proportion. In summary, a panel of ancestry-informative INDELs was optimized and proven to be a valuable tool for estimating individual and global ancestry proportions in admixed populations. The ability to accurately infer interethnic admixtures highlights the usefulness of this marker set for assessing population substructure in association studies, particularly those conducted in Brazilian and other Latin American populations sharing trihybrid ancestry patterns.

Human T cell lymphotropic virus type II (HTLV-II) infection is endemic in a number of indigenous populations in North, Central, and South America. In the present study we have employed serological and molecular methods to identify HTLV-II infection in Indian communities in the Amazon region of Brazil. Sera (1324) from 25 different Indian communities were analyzed by ELISA and Western blot. One hundred and four samples (7.8%) from a number of culturally distinct and geographically unrelated populations were found to have reactivities consistent with HTLV-II infection. Of these, 67 were from the Kayapo Indian communities, which had an overall seroprevalence rate of greater than 30%. In addition, high seroprevalence rates were observed in three other communities, the Munduruku, Arara do Laranjal and the Tyrio, suggesting that there are additional foci of endemic infection in the Amazon region. In the Kayapo, seroprevalence rates tended to increase with age, supporting the importance of sexual transmission of the virus, and family studies demonstrated that vertical transmission is also an important route of infection. Restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of a region of the env gene demonstrated that the Kayapo are infected with the HTLV-IIa subtype. Moreover, nucleotide sequence analysis of the LTR demonstrated that this belonged to a distinct HTLV-IIa phylogenetic group. The identification of HTLV-IIa in the Kayapo is, as far as we are aware, the first identified endemic focus of infection by this subtype of HTLV-II in the Americas.

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Molecular studies have demonstrated the existence of at least two major subtypes of human T-cell lymphotropic virus type 2 (HTLV-2), designated HTLV-2a and HTLV-2b. To further investigate the heterogeneity of this family of viruses, we have characterized the HTLV-2 subtypes present in several urban areas in Brazil. DNAs from peripheral blood mononuclear cells of a large number of infected individuals, the majority of whom were intravenous drug abusers, were analyzed by using PCR with restriction fragment length polymorphism and nucleotide sequencing analysis. Restriction fragment length polymorphism analysis of the env region suggested that all individuals were infected with the HTLV-2a subtype, and this was confirmed by nucleotide sequence analysis. In contrast, nucleotide sequence analysis of the long terminal repeat demonstrated that although the viruses were more related to the HTLV-2a than to the HTLV-2b subtype, they clustered in a distinct phylogenetic group, suggesting that they may represent a new and distinct molecular subtype of HTLV-2. This conclusion was supported by nucleotide sequence analysis of the pX region, which demonstrated that the Tax proteins of the Brazilian viruses differed from that of prototype HTLV-2a isolates but were more similar to that of HTLV-2b in that they would be expected to have an additional 25 amino acids at the carboxy terminus. In transient expression assays, the extended Tax proteins were found to be much more potent transactivators of the virus long terminal repeat than the Tax protein of the prototype HTLV-2a subtype. The studies suggest that the Brazilian viruses analyzed in this study, while being phylogenetically related to the prototypic HTLV-2a seen in North America, are phenotypically more related to HTLV-2b and can be justifiably classified as a new molecular subtype, which has been tentatively designated HTLV-2c.

The allele frequencies of six VNTRs (D1S80, D4S43, ApoB 3’ VNTR, von Willebrand factor VNTR-I, DXS52 and DYS19) in 123 Amerindians from five tribes (Arara, Wayana-Apalai, Wayampi, Yanomama and Kayapo) were compared with three other Brazilian populations: Whites, Blacks, and individuals of Japanese extraction. The data clearly distinguished the four populations, and measurements of diversity show a decreasing average heterozygosity from Blacks to Whites, Japanese, and Indians. Seven novel alleles were observed; amongst them, two small DYS19 alleles and a large D4S43 allele occurred only in Indians, and may be useful genetic markers for this population. Other prominent features of the Amerindians were: (1) high frequency of ApoB allele 46; (2) absence of a shorter variant of D4S43 allele 1; (3) high frequency, limited to one tribe, of allele 12 of the von Willebrand VNTR. The study also demonstrated a heterogeneity of the Indian tribes, due to both different allele frequencies and the presence or absence of specific alleles. Gst was 0.106 for the five Indian populations, and 0.065 for Whites, Blacks and Japanese. H_S and H_T demonstrated that 11 % of the total diversity among Amerindians is caused by interpopulational variability, as compared with 7% for the other three racial groups. In contrast, diversity within each tribe is usually low, as demonstrated by a low average number of alleles per locus. These findings indicate that the study of a small number of tribes may not be representative of the variability of Amerindians, even if a large number of individuals are studied. To capture the whole range of genetic variability of Amerindians, it is necessary to study a large number of populations. The limited genetic diversity thus far observed for Amerindians seems to reflect both a genuine decrease of diversity and a bias caused by the study of limited numbers of tribes.

SummaryA polymorphism in the coagulation factor XIII gene (FXIII Val34Leu) has been recently described to confer protection for arterial and venous thrombosis and to predispose to intracerebral hemorrhage. At present it is known that FXIII Val34Leu is prevalent in Caucasians, but information upon its distribution in different ethnic groups is scarce. We investigated the prevalence of FXIIIVal34Leu in 450 unrelated subjects of four ethnic groups: 97 Caucasians (Brazilians of European descent and Portuguese), 149 Blacks (Brazilians, and Africans from Cameroon, Zaire and Angola), 40 Asians (Japanese descendents) and 164 Amerindians from South America. PCR amplification of exon 2 of FXIII gene followed by MseI restriction-digestion was employed to define the genotypes. FXIIIVal34Leu was detected in 44.3% of the Caucasians, in 28.9% of the Blacks, in 2.5% of the Asians and in 51.2% of the Amerindians. These data confirm that FXIII Val34Leu is highly prevalent in Caucasians and indicate that it is rarer in populations of African origin. The very high frequency among Amerindians indicates that FXIII Val34Leu is not absent among Asians, and since it has a very low prevalence in Japanese, a heterogeneity in its distribution in Asia may be inferred. Taken together, our data showed that FXIII Val34Leu exhibits a significant ethnic heterogeneity, a finding that is relevant for studies relating this polymorphism with thrombotic and bleeding disorders.

Início da vida sexual em adolescentes escolares: um estudo transversal sobre comportamento sexual de risco em Abaetetuba, Estado do Pará, BrasilOnset of sexual intercourse among adolescent students: a cross-sectional study of sexual risk behavior in Abaetetuba, Pará State, Brazil Inicio de la vida sexual en escolares adolescentes: un estudio transversal sobre el comportamiento sexual de riesgo en Abaetetuba, Estado de Pará, Brasil RESUMOA adolescência é uma fase da vida compreendida entre 10 e 19 anos de idade, caracterizada pelos conflitos e descobertas. Nessa fase, os adolescentes começam a viver suas primeiras experiências sexuais, podendo apresentar comportamentos com risco de infecções por DST/Aids, os quais podem ser: início precoce da vida sexual e uso inconsistente de preservativo. Este estudo teve por objetivo identificar a idade da primeira relação sexual e o uso do preservativo em adolescentes escolares de 14 a 19 anos de idade, alunos do ensino médio, matriculados na rede pública estadual no Município de Abaetetuba, Estado do Pará, Brasil, no ano de 2010. Para a coleta de dados utilizou-se um questionário com perguntas fechadas, autopreenchível, pré-codificado, anônimo, adaptado da "Pesquisa de Comportamento, Atitudes e Práticas da População Brasileira sobre DST/Aids, 2008", realizada pelo Ministério da Saúde. Para os testes estatísticos utilizaram-se os softwares STATISTICA ® v.6.0 e BioEstat 5.0. Foram entrevistados 603 adolescentes, sendo 61,03% (368) mulheres e 38,97% (235) homens, com média de idade de 17,14 anos. Já havia iniciado sua vida sexual 49,25% dos adolescentes (297) com média de idade na primeira relação sexual de 15,23 anos. A iniciação sexual precoce esteve associada ao sexo masculino (OR = 3,72; IC95% 2,13-6,47; p < 0,0001). O uso do preservativo na primeira relação sexual esteve associado ao gênero, sendo que as mulheres tiveram uso mais consistente nessa ocasião (OR = 2,04; IC95% 1,20-3,47; p = 0,011). Não usaram preservativo na primeira relação 27,95% dos adolescentes, sendo estes 66,26% homens. Observou-se comportamento sexual de risco na amostra estudada, em especial na população masculina. Palavras INTRODUÇÃOA palavra "adolescência" tem origem no latim, derivada do verbo adolescere que denota "crescer", "desenvolver-se", "tornar-se maior" ou então, "crescer até a maturidade" 1,2,3,4,5 8,9 . A escolha deste parceiro sexual ocorre inicialmente de maneira discreta; contudo, vai-se tornando cada vez mais intensa até que esse adolescente tenha sua primeira relação sexual, a qual vem acontecendo cada vez mais cedo 10,11 .A iniciação sexual é um evento marcante na vida de um adolescente. Ao mesmo tempo em que lhe permite adentrar em um mundo de novas descobertas, pode inseri-lo em um grupo de vulnerabilidade a doenças sexualmente transmissíveis (DST) e aids. Essa inserção pode ter como desfecho, também, a ocorrência de gravidez na adolescência, aborto e outros problemas de ordem biológica, socioeconômica e psicológica 12,13,14,15,16 .Identificam-se na literatura estudos que enf...

BackgroundMeasurement of malaria endemicity is typically based on vector or parasite measures. A complementary approach is the detection of parasite specific IgG antibodies. We determined the antibody levels and seroconversion rates to both P. vivax and P. falciparum merozoite antigens in individuals living in areas of varying P. vivax endemicity in Pará state, Brazilian Amazon region.Methodology/Principal FindingsThe prevalence of antibodies to recombinant antigens from P. vivax and P. falciparum was determined in 1,330 individuals. Cross sectional surveys were conducted in the north of Brazil in Anajás, Belém, Goianésia do Pará, Jacareacanga, Itaituba, Trairão, all in the Pará state, and Sucuriju, a free-malaria site in the neighboring state Amapá. Seroprevalence to any P. vivax antigens (MSP1 or AMA-1) was 52.5%, whereas 24.7% of the individuals were seropositive to any P. falciparum antigens (MSP1 or AMA-1). For P. vivax antigens, the seroconversion rates (SCR) ranged from 0.005 (Sucuriju) to 0.201 (Goianésia do Pará), and are strongly correlated to the corresponding Annual Parasite Index (API). We detected two sites with distinct characteristics: Goianésia do Pará where seroprevalence curve does not change with age, and Sucuriju where seroprevalence curve is better described by a model with two SCRs compatible with a decrease in force of infection occurred 14 years ago (from 0.069 to 0.005). For P. falciparum antigens, current SCR estimates varied from 0.002 (Belém) to 0.018 (Goianésia do Pará). We also detected a putative decrease in disease transmission occurred ∼29 years ago in Anajás, Goianésia do Pará, Itaituba, Jacareacanga, and Trairão.ConclusionsWe observed heterogeneity of serological indices across study sites with different endemicity levels and temporal changes in the force of infection in some of the sites. Our study provides further evidence that serology can be used to measure and monitor transmission of both major species of malaria parasite.