Association between HLA-DR4 haplotypes and tuberculin skin test response in the Aché population

A next generation sequencing combined genome-wide association study identifies novel tuberculosis susceptibility loci in Chinese population

The genetic factors of tuberculosis (TB) susceptibility have been widely recognized. Here we performed a two-stage study in 616 TB patients and 709 healthy controls to systematically identify the genetic markers of TB susceptibility. In the discovery stage, we identified 93 single nucleotide polymorphisms (SNPs) and 3 human leucocyte antigen (HLA) class II alleles that had potential associations with TB susceptibility. In the validation stage, we confirmed that 6 nominally significant SNPs, including 2 novel missense variants at RAB17 and DCTN4 (odds ratio (OR) = 1.40, P = 4.98 × 10^-3 and OR = 2.30, P = 3.17 × 10^-2 respectively), were associated with the predisposition to TB. Moreover, our study found that HLA-II allele DQA1*05:05 (P = 0.0011, OR = 1.44, 95%CI = 1.15-1.77) was a TB susceptibility locus for the first time. This study comprehensively investigated the genetic variants that were associated with TB susceptibility and provided insight into the tuberculosis pathogenesis.

ACE2 polymorphisms as potential players in COVID-19 outcome

The clinical condition COVID-19, caused by SARS-CoV-2, was declared a pandemic by the WHO in March 2020. Currently, there are more than 5 million cases worldwide, and the pandemic has increased exponentially in many countries, with different incidences and death rates among regions/ethnicities and, intriguingly, between sexes. In addition to the many factors that can influence these discrepancies, we suggest a biological aspect, the genetic variation at the viral S protein receptor in human cells, ACE2 (angiotensin I-converting enzyme 2), which may contribute to the worse clinical outcome in males and in some regions worldwide. We performed exomics analysis in native and admixed South American populations, and we also conducted in silico genomics databank investigations in populations from other continents. Interestingly, at least ten polymorphisms in coding, noncoding and regulatory sites were found that can shed light on this issue and offer a plausible biological explanation for these epidemiological differences. In conclusion, there are ACE2 polymorphisms that could influence epidemiological discrepancies observed among ancestry and, moreover, between sexes.

The role of variants from the innate immune system genes in tuberculosis and skin test response in a Native American population

Native American populations show higher tuberculosis (TB) mortality and infectivity rates than non-Native populations. Variants in the innate immune system seem to have an important role on TB susceptibility. The role of some innate immune system variants in TB susceptibility and/or skin test response (PPD) were investigated in the Aché, a Native American population. Complement receptor 1 and toll like receptor 9 variants were associated with anergy to PPD and protection to TB, respectively. These findings demonstrate an important role of the innate immune system variants in TB susceptibility.

Variability of innate immune system genes in Native American populations-relationship with history and epidemiology

OBJECTIVES

The immune system of a host, defending him/her against invading pathogens, has two main subsystems: innate immunity and acquired immunity. There are several evidences showing that Native American populations are immunologically different from non-Native populations. Our aim was to describe the variability of innate immune system genes in Native American populations.

MATERIALS AND METHODS

We investigated heterozygozities and patterns of population differentiation (FST ) of 14 polymorphisms related to the innate immune response in five Native American populations (Aché, Guarani-Kaiowá, Guarani-Ñandeva, Kaingang, and Xavante) and the results were compared with the three major world population data (YRI, CEU, and CHB) available at the 1,000 genomes database.

RESULTS

Mean heterozygosities ranged between 0.241 ± 0.057 (Aché) and 0.343 ± 0.033 (Kaingang), but no significant differences were observed (Friedman test, P = 0.197). Mean heterozygosities were also not significantly different when Amerindians were pooled and compared with the 1000 genomes populations (Friedman test, P = 0.506). When the Native American populations were grouped as Amerindians, a significantly higher FST value (0.194) was observed between the Amerindian and African populations. The Ewens-Watterson neutrality test showed that these markers are not under strong selective pressure.

DISCUSSION

Native American populations present similar levels of heterozygosity as those of other continents, but are different from Africans in the frequency of polymorphisms of innate immune genes. This higher differentiation is probably due to demographic processes that occurred during the out-of-Africa event.

T cells and adaptive immunity to Mycobacterium tuberculosis in humans

The adaptive immune response mediated by T cells is critical for control of Mycobacterium tuberculosis (M. tuberculosis) infection in humans. However, the M. tuberculosis antigens and host T-cell responses that are required for an effective adaptive immune response to M. tuberculosis infection are yet to be defined. Here, we review recent findings on CD4(+) and CD8(+) T-cell responses to M. tuberculosis infection and examine the roles of distinct M. tuberculosis-specific T-cell subsets in control of de novo and latent M. tuberculosis infection, and in the evolution of T-cell immunity to M. tuberculosis in response to tuberculosis treatment. In addition, we discuss recent studies that elucidate aspects of M. tuberculosis-specific adaptive immunity during human immunodeficiency virus co-infection and summarize recent findings from vaccine trials that provide insight into effective adaptive immune responses to M. tuberculosis infection.

Mortality from contact-related epidemics among indigenous populations in Greater Amazonia

European expansion and contact with indigenous populations led to catastrophic depopulation primarily through the introduction of novel infectious diseases to which native peoples had limited exposure and immunity. In the Amazon Basin such contacts continue to occur with more than 50 isolated indigenous societies likely to make further contacts with the outside world in the near future. Ethnohistorical accounts are useful for quantifying trends in the severity and frequency of epidemics through time and may provide insight into the likely demographic consequences of future contacts. Here we compile information for 117 epidemics that affected 59 different indigenous societies in Greater Amazonia and caused over 11,000 deaths between 1875 and 2008, mostly (75%) from measles, influenza, and malaria. Results show that mortality rates from epidemics decline exponentially through time and, independently, with time since peaceful contact. The frequency of documented epidemics also decreases with time since contact. While previous work on virgin soil epidemics generally emphasizes the calamity of contacts, we focus instead on improvements through time. The prospects for better survivorship during future contacts are good provided modern health care procedures are implemented immediately.