No abstract

A longitudinal study, spanning 25 years and great demographic and cultural change, found a persistently high prevalence of human T-lymphotropic virus type II (HTLV-II) in the Xikrin Kayapo Indians of Brazil. More than 10% of the children continue to develop immune reactions to the virus in infancy, a sharp increase in seroprevalence occurs between ages 15 and 30 years, and prevalence in older woman still approaches 100%. This suggests that the major modes of transmission (breast milk and sexual activity) have not changed. The demonstration of stable maintenance of HTLV-II in one ethnic group makes migration theories of its dispersal more plausible. However, the infection may not be a negligible burden on population survival: at least 1 of 62 persons followed until age 40 years died of possible tropical spastic paraparesis (TSP).

Characterization of population genetic variation and structure can be used as tools for research in human genetics and population isolates are of great interest. The aim of the present study was to characterize the genetic structure of Xavante Indians and compare it with other populations. The Xavante, an indigenous population living in Brazilian Central Plateau, is one of the largest native groups in Brazil. A subset of 53 unrelated subjects was selected from the initial sample of 300 Xavante Indians. Using 86,197 markers, Xavante were compared with all populations of HapMap Phase III and HGDP-CEPH projects and with a Southeast Brazilian population sample to establish its population structurePrincipal Components Analysis showed that the Xavante Indians are concentrated in the Amerindian axis near other populations of known Amerindian ancestry such as Karitiana, Pima, Surui and Maya and a low degree of genetic admixture was observed. This is consistent with the historical records of bottlenecks experience and cultural isolation. By calculating pair-wise Fst statistics we characterized the genetic differentiation between Xavante Indians and representative populations of the HapMap and from HGDP-CEPH project. We found that the genetic differentiation between Xavante Indians and populations of Ameridian, Asian, European, and African ancestry increased progressively. Our results indicate that the Xavante is a population that remained genetically isolated over the past decades and can offer advantages for genome-wide mapping studies of inherited disorders.

The human platelet alloantigen 9bw (HPA-9bw, Max a ) is an epitope of GPIIb and differs by 2602G>A single nucleotide polymorphism (SNP), resulting in a Val/Met substitution at amino acid 837 (Noris et al., 1995). Alloantibodies against Max a are involved in the development of neonatal alloimmune thrombocytopenia (NAIT) (Kaplan et al., 2005;Raj et al., 2009). The frequency of HPA-9b allele is low at 0·003 in the Dutch population (Noris et al., 1995), 0·002 in United States (Peterson et al., 2005) and 0·0 in China (Xu et al., 2009). However, Peterson and coworkers found six cases involving alloantibodies anti-HPA-9bw among 217 cases not resolved on NAIT, suggesting that HPA-9bw may be the third most important trigger for NAIT, after HPA-1a and HPA-5b (Peterson et al., 2005). In such studies, HPA-3b allele was present in all individuals with HPA-9b allele.The HPA frequencies vary among distinct populations. In the literature, there are no data for the allelic frequencies of HPA-9 system in the South American population. In this study, we used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to determine the HPA-9 and HPA-3 allelic frequencies in Brazilian blood donors and Amazon Indians. The study was approved by the University Research Ethics Committee (CEP 0793/08). Blood samples from 1073 unrelated Brazilian blood donors and 120 Amazon Indians (Xikrin Kayapo Indians) were collected. DNA was isolated using a commercial kit (QIAamp DNA Blood mini kit, Qiagen, Hilden, Germany) and genotyped by PCR-RFLP using BstNI restriction enzyme for HPA-9 and Fok I for HPA-3. Control samples were used and we performed the sequencing in selected samples containing the SNPs to confirm the region studied.The results of genotype and allelic frequencies of HPA-9 and HPA-3 systems in Brazilian blood donors and Xikrin Indians are shown in Table 1. We found that the frequencies of the genotypes HPA-9a/9a, 9a/9b and 9b/9b were 99·72, 0·28 and 0% in Brazilian blood donors and 100, 0 and 0% in Amazon Indians, respectively. HPA-3a/3a, 3a/3b and 3b/3b had frequencies of 41·29, 46·50 and 12·21% in Brazilian blood donors and 41·67, 52·50 and 5·83% in Amazon Indians. The analysis by statistical χ 2 with significance level of 0·05 showed that no statistically significant differences were found regarding the HPA-9a, HPA-9b, HPA-3a and HPA-3b allelic frequencies between Brazilian blood donors (0·999, 0·001, 0·645, 0·355) and Xikrin Indians (1·0, 0·0, 0·679, 0·321). Using sequencing methods for selected samples we confirmed the corresponding SNPs; however, we did not find any other polymorphisms such as those described by the study of Hallé and coworkers in which they found mutations on GPIIb exon 26 (2614C>A and 2645C>T) and intron 26 (IVS26+89G>A) (Hallé et al., 2008). All individuals carrying the HPA-9b allele also had the HPA-3b allele.The HPA-9 allelic frequencies found in Brazilians are quite similar to those reported by studies performed with Dutch, North American and Chinese individuals as mentioned e...

RESUMO - INTRODUÇÃOEm nossas viagens anuais às reservas indíge-nas Xavantes de Sangradouro e São Marcos, observamos seis casos com um mesmo quadro clínico de fraqueza progressiva, emagrecimento progressivo, perda da massa muscular e dificuldade motora. Dos seis casos observados, dois ocorreram em Sangradouro, um dos quais evoluiu para caquexia e morte e o outro faz parte deste nosso relatório; quatro ocorreram em São Marcos, um dos quais faz parte deste relatório, outros dois evoluíram para caquexia e morte, o quarto encontra-se em caquexia. Quatro casos não tinham condições de ser removidos para centros hospitalares de grandes cidades para uma investigação precisa, devido a não caminharem, não conseguirem ficar em pé e caquexia. Dos seis casos, dois eram irmãos do mesmo sexo masculino em São Marcos, dois eram irmãos de sexo contrário da aldeia Auxiliadora em São Marcos, pertencentes a famílias extensas. Os índios atribuíam a doença à feitiçaria.Diante da gravidade dos casos e da evolução inexorável para a morte, num período de 1 a 2 anos, de jovens entre 15 e 25 anos de idade, insistimos para que nos procurassem na Universidade Federal de São Paulo (Hospital São Paulo) para diagnóstico e esclarecimento da patologia.Os Xavantes tiveram um aumento demográfico notável sobretudo nas reservas de Sangradouro e São Marcos, com uma natalidade anual em cada reserva de 50 a 60 crianças, contando com assistên-cia e zelo dos missionários católicos da ordem de Dom Bosco. A população total de todas as reservas Xavantes aproxima-se de 20 mil.Os Xavantes aceitaram no passado o Projeto Arroz da FUNAI, que veio minorar o problema da fome 1 . Na mudança de hábito alimentar, o arroz passou a ser consumido em quantidade. O arroz passou a ser muito valorizado pelos índios, permanecendo em suas roças anuais após o término do Projeto Arroz, com o fim dos subsídios para mecanização em roças de cerrado.