The X chromosome and X-linked variants have largely been ignored in genome-wide and candidate association studies of infectious diseases due to the complexity of statistical analysis of the X chromosome. This exclusion is significant, since the X chromosome contains a high density of immune-related genes and regulatory elements that are extensively involved in both the innate and adaptive immune responses. Many diseases present with a clear sex bias, and apart from the influence of sex hormones and socioeconomic and behavioural factors, the X chromosome, X-linked genes and X chromosome inactivation mechanisms contribute to this difference. Females are functional mosaics for X-linked genes due to X chromosome inactivation and this, combined with other X chromosome inactivation mechanisms such as genes that escape silencing and skewed inactivation, could contribute to an immunological advantage for females in many infections. In this review, we discuss the involvement of the X chromosome and X inactivation in immunity and address its role in sexual dimorphism of infectious diseases using tuberculosis susceptibility as an example, in which male sex bias is clear, yet not fully explored.

BackgroundStudies investigating the influence of toll-like receptor (TLR) polymorphisms and tuberculosis susceptibility have yielded varying and often contradictory results in different ethnic groups. A meta-analysis was conducted to investigate the relationship between TLR variants and susceptibility to tuberculosis, both across and within specific ethnic groups.MethodsAn extensive database search was performed for studies investigating the relationship between TLR and tuberculosis (TB) susceptibility. Data was subsequently extracted from included studies and statistically analysed.Results32 articles involving 18907 individuals were included in this meta-analysis, and data was extracted for 14 TLR polymorphisms. Various genetic models were employed. An increased risk of TB was found for individuals with the TLR2 rs3804100 CC and the TLR9 rs352139 GA and GG genotypes, while decreased risk was identified for those with the AG genotype of TLR1 rs4833095. The T allele of TLR6 rs5743810 conferred protection across all ethnic groups. TLR2 rs5743708 subgroup analysis identified the A allele to increase susceptibility to TB in the Asian ethnic group, while conferring protection in the Hispanic group. The T allele of TLR4 rs4986791 was also found to increase the risk of TB in the Asian subgroup. All other TLR gene variants investigated were not found to be associated with TB in this meta-analysis.DiscussionAlthough general associations were identified, most TLR variants showed no significant association with TB, indicating that additional studies investigating a wider range of pattern recognition receptors is required to gain a better understanding of this complex disease.

Admixture is a well known confounder in genetic association studies. If genome-wide data is not available, as would be the case for candidate gene studies, ancestry informative markers (AIMs) are required in order to adjust for admixture. The predominant population group in the Western Cape, South Africa, is the admixed group known as the South African Coloured (SAC). A small set of AIMs that is optimized to distinguish between the five source populations of this population (African San, African non-San, European, South Asian, and East Asian) will enable researchers to cost-effectively reduce false-positive findings resulting from ignoring admixture in genetic association studies of the population. Using genome-wide data to find SNPs with large allele frequency differences between the source populations of the SAC, as quantified by Rosenberg et. al's -statistic, we developed a panel of AIMs by experimenting with various selection strategies. Subsets of different sizes were evaluated by measuring the correlation between ancestry proportions estimated by each AIM subset with ancestry proportions estimated using genome-wide data. We show that a panel of 96 AIMs can be used to assess ancestry proportions and to adjust for the confounding effect of the complex five-way admixture that occurred in the South African Coloured population.

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This is the first report of the association of human HLA types and M. tuberculosis strain genotype, highlighting that both host and pathogen genetics need to be taken into consideration when studying tuberculosis disease development.

Genome-wide association studies (GWAS) have implicated single nucleotide polymorphisms (SNPs) on chromosomes 2p15, 6q25, 7p15.2, 7q21, 8q24, 10q11, 10q26, 11q13, 17q12, 17q24, 19q13, and Xp11, with prostate cancer (PCa) susceptibility and/or tumour aggressiveness, in populations of African, European, and Asian ancestry. The objective of this study was to confirm these associations in South African Mixed Ancestry and White men. We evaluated 17 prioritised GWAS SNPs in South African cases (331 Mixed Ancestry and 155 White) and controls (178 Mixed Ancestry and 145 White). The replicated SNP associations for the different South African ethnic groups were rs7008482 (8q24) (p = 2.45 × 10−5), rs6983267 (8q24) (p = 4.48 × 10−7), and rs10993994 (10q11) (p = 1.40 × 10−3) in Mixed Ancestry men and rs10993994 (p = 1.56 × 10−9) in White men. No significant associations were observed for the analyses stratified by disease aggressiveness in the individual and the combined population group analysis. The present study demonstrates that a number of known PCa susceptibility variants may contribute to disease susceptibility in South African men. Larger genetic investigations extended to other South African population groups are warranted to confirm the role of these and other SNPs in disease susceptibility.

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Background: Acceptance of DOTS stratergy in the Indian RNTCP has certainly brought encouraging success in the management of TB cases within the country. However there are challenges to be met in the programme implementation, before the RNTCP objectives are finally realized. One such challenge is the social stigma associated with the TB patients. The study attempts to find out the concerns of the TB patients who receive the DOTS within the same community. Objective: To know the major concerns of the TB patients who are receiving the DOTS from the DOTS providers within the same community/village Methods & Materials: An interview was conducted of 256 patients who are receiving the DOTS within their communities/villages across the five development blocks of Munger district of Bihar Results: Of all the TB patients who were interviewed 53 percent reported that they wanted to hide from the community that they have TB but they have to reveal it to others about their disease because they have to take the DOTS from the providers within the village. Of all those interviewed, 47 percent said that taking DOTS had a negative impact on them with respect to social discrimination within the community. 53 percent reported that because of DOTS several people in the community knew that they have TB which led to the discrimination. Conclusion: Notions restricting the acceptance of TB patients are still prevalent in the minds of people and require a propagation of frequent IEC campaigns to remove superstitutions amongst the people.