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The human leukocyte antigen (HLA) system has a major role in the regulation of the immune response as it is involved in the defense against pathogens. Evidence for association with tuberculosis (TB) is more consistent for class II than for class I HLA genes. TB is important among indigenous peoples in South America, not only because of its historical role in regional depopulation, but also because it is still widespread. The aim of this study was to evaluate the association of HLA class II alleles, haplotypes and genotypes and tuberculin skin test response (TST) in 76 individuals of the Aché population. Poisson Regression was employed to assess risk genotypes. DRB1*04, DQA1*03 and DQB1*03:02 were associated with TST response in this population., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

A sample of 103 randomly chosen healthy individuals from Alegrete, RS, Brazil, was tested for the CCR5delta32 allele, which is known to influence susceptibility to HIV-1 infection. The CCR5delta32 allele was identified by PCR amplification using specific primers flanking the region of deletion, followed by electrophoresis on a 3% agarose gel. The data obtained were compared to those reported for other populations and interpreted in terms of Brazilian history. The individuals studied came from a highly admixed population. Most of them were identified as white (N = 59), while blacks and browns (mulattoes) were N = 13 and N = 31, respectively. The observed frequencies, considering the white, black and brown samples (6.8, 3.8, and 6.4%, respectively), suggest an important European parental contribution, even in populations identified as black and brown. However, in Brazil as a whole, this allele shows gradients indicating a relatively good correlation with the classification based on skin color and other physical traits, used here to define major Brazilian population groups.

We have studied the hypervariable D1S80 locus in 185 individuals from five South American Indian tribes, integrating these results with previous investigations. Three alleles (*18, *24 and *30) were common to all tribes, but their frequencies varied between northern and southern populations. Brazilian tribes have a high frequency of *30 (average 35%) while in Argentinian and Chilean Indian populations this allele is present, on average, in 7% of the chromosomes only. Allele *24, the most common in other ethnic groups, was observed in 10% and 25% of northern and southern Amerindians respectively. Genetic distance and dendrogram analyses placed the Argentinian and Chilean tribes closer to Brazilian Caucasians, suggesting non-Indian admixture among them.

We have studied the hypervariable locus D1S80 in 75 white and 53 black Brazilians from Porto Alegre, a southern Brazilian population, and in 50 Brazilian Indians from the Xavante and Zoró tribes. Allele frequencies were significantly different among the three ethnic groups, mainly because of the higher frequencies of alleles *21, *22, *28, and *34 and the lower frequency of allele *18 in individuals of African ancestry and the higher frequencies of alleles *18 and *30 in Brazilian Indians. In the Indian group a restriction in the number of alleles (7) and genotypes (15) was found. The data suggest that the D1S80 locus is a useful interpopulation marker. This is the first report of its allele frequencies in Amerindians.

Summary Neural tube defects (NTDs) have been associated with abnormalities of folate metabolism. Methylenetetrahydrofolate reductase (MTHFR) is the regulatory enzyme for the conversion of homocysteine to methionine. The C677T mutation in the MTHFR gene affects folate distribution, and homozygosity for the T allele may be associated with an increased risk of NTDs. A second mutation, an A1298C transversion in this same gene, is also associated with an increased risk for NTDs but only in conjunction with the 677T allele. A low incidence of NTDs has been observed in high-altitude populations; however, these studies did not provide information about the allele distribution of genes involved in folate metabolism. This investigation compares allele frequencies of the C677T and A1298C polymorphisms between Quechua people living at 3200–4200 m in the Peruvian Central Andes and an Aché group living at low altitude. Allele frequencies at both loci were not significantly different between the two populations. The absence of the 677T/677T genotypes and of the 677T/1298C arrangement in both groups may indicate a genetic contribution to reduced risk for NTDs; however, factors other than altitude are likely responsible for the low variant allele frequencies in these populations. [ABSTRACT FROM AUTHOR]

The apolipoprotein E (APOE) polymorphism was investigated in 186 individuals from six South American Indian tribes, and the results integrated with those previously presented for this ethnic group. The three APOE alleles commonly reported in other populations were also observed in South Amerindians with a highly heterogeneous distribution. As in other populations, APOE*3 was the most common allele (51-98%) followed by APOE*4 (2-47%). These two isoforms were identified in all tribes, but APOE*2 was observed among the Wai Wai (2%) and Mataco (4%) only. No previous indications of inter-ethnic admixture were observed among the Wai Wai, but the introduction of this allele among the Mataco through non-Indian sources cannot be excluded. An 186 Angehorigen sechs sudamerikanischer Indianerstamme wurde der Apolipoprotein E (APOE)-Polymorphismus untersucht. Die Ergebnisse werden im Zusammenhang mit bereits bekannten Ergebnissen fur diese ethnische Gruppe diskutiert. Die drei APOE-Allele, die im allgemeinen in anderen Bevolkerungen vorkommen, wurden mit einer sehr heterogenen Verteilung auch bei den sudamerikanischen Indianern beobachtet. Wie in anderen Bevolkerungen war das APOE*3-Allel das haufigste (51-98%), gefolgt vom APOE*4-Allel (2-47%). Diese zwei Allele wurden bei allen Stammen beobachtet, das APOE*2-Allel wurde dagegen nur bei den Wai Wai (2%) und den Mataco (4%) gefunden. Wahrend eine Einfuhrung dieses Allels aus nicht indianischen Quellen bei den Mataco nicht ausgeschlossen werden kann, gab es fur die Wai Wai bisher keine Anhaltspunkte fur eine inter-ethnische Durchmischung. Le polymorphisme de l'alipoproteine E (APOE) a ete analyse chez 186 individus de six tribus indiennes d'Amerique du Sud et les resultats ont ete integres a ceux deja connus pour ces groupes ethniques. Les trois alleles APOE frequemment rencontres dans d'autres populations, sont egalement observes parmi les amerindiens d'Amerique du Sud, avec une distribution extremement heterogene. Comme ailleures, l'allele APOE*3 est le plus repandu (51-98%), suivi par l'APOE*4 (2-47%). Ces deux isoformes ont ete identifiees dans toutes les tribus, mais APOE*2 a seulement ete observe chez les Wai Wai (2%) et chez les Mataco (4%). On n'a pas d'informations qui appuieraient l'existence de melange inter-ethnique chez les Wai Wai, mais l'introduction de cet allele chez les Mataco par l'intermediaire de sources non indiennes, ne peut etre exclue. [ABSTRACT FROM AUTHOR]

It has been suggested that average genetic similarity, as assessed by blood genetic markers, could influence mate choice in humans. In the present study, average genetic similarity was assessed in 183 couples submitting to paternity determinations in relation to six blood group systems and three HLA loci. Couples in which the putative father was excluded were compared with those in which such exclusion did not occur, and real couples were compared to random pairs. The differences were all statistically non-significant. Possible reasons for the different results found in the previous sample and in the present study are considered. [ABSTRACT FROM PUBLISHER]