We combined two tuberculosis (TB) genome-wide association studies (GWAS) from Ghana and The Gambia with subsequent replication totalling 11,425 participants. A significant association with disease was observed at SNP rs4331426 located in a gene-poor region on chromosome 18q11.2 (P=6.8×10−9, OR=1.19, 95%CI=1.13-1.27). Our finding shows that GWAS can identify novel loci for infectious causes of mortality even in Africa where levels of linkage disequilibrium are particularly low.

The human immunity-related GTPase M (IRGM) has been shown to be critically involved in regulating autophagy as a means of disposing cytosolic cellular structures and of reducing the growth of intracellular pathogens in vitro. This includes Mycobacterium tuberculosis, which is in agreement with findings indicating that M. tuberculosis translocates from the phagolysosome into the cytosol of infected cells, where it becomes exposed to autophagy. To test whether IRGM plays a role in human infection, we studied IRGM gene variants in 2010 patients with pulmonary tuberculosis (TB) and 2346 unaffected controls. Mycobacterial clades were classified by spoligotyping, IS6110 fingerprinting and genotyping of the pks1/15 deletion. The IRGM genotype −261TT was negatively associated with TB caused by M. tuberculosis (OR 0.66, CI 0.52–0.84, Pnominal 0.0009, Pcorrected 0.0045) and not with TB caused by M. africanum or M. bovis (OR 0.95, CI 0.70–1.30. P 0.8). Further stratification for mycobacterial clades revealed that the protective effect applied only to M. tuberculosis strains with a damaged pks1/15 gene which is characteristic for the Euro-American (EUAM) subgroup of M. tuberculosis (OR 0.63, CI 0.49–0.81, Pnominal 0.0004, Pcorrected 0.0019). Our results, including those of luciferase reporter gene assays with the IRGM variants −261C and −261T, suggest a role for IRGM and autophagy in protection of humans against natural infection with M. tuberculosis EUAM clades. Moreover, they support in vitro findings indicating that TB lineages capable of producing a distinct mycobacterial phenolic glycolipid that occurs exclusively in strains with an intact pks1/15 gene inhibit innate immune responses in which IRGM contributes to the control of autophagy. Finally, they raise the possibility that the increased frequency of the IRGM −261TT genotype may have contributed to the establishment of M. africanum as a pathogen in the West African population.

Current endeavour focuses on human genetic factors that contribute to susceptibility to or protection from tuberculosis (TB). Monocytes are crucial in containing Mycobacterium tuberculosis infection, and the monocyte chemoattractant protein-1 (MCP-1) cytokine plays a role in their recruitment to the site of infection. The G allele of the MCP-1 promoter polymorphism at position -2581 relative to the ATG transcription start codon has been described to be associated in Mexican and Korean TB patients with increased susceptibility to TB. We genotyped this and additional MCP-1 variants in sample collections comprising more than 2000 cases with pulmonary TB and more than 2300 healthy controls and 332 affected nuclear families from Ghana, West Africa, and more than 1400 TB patients and more than 1500 controls from Russia. In striking contrast to previous reports, MCP-1 -2581G was significantly associated with resistance to TB in cases versus controls [odds ratio (OR) 0.81, corrected P-value (P(corr)) = 0.0012] and nuclear families (OR 0.72, P(corr) = 0.04) and not with disease susceptibility, whereas in the Russian sample no evidence of association was found (P = 0.86). Our and other results do not support an association of MCP-1 -2581 with TB. In the Ghanaian population, eight additional MCP-1 polymorphisms were genotyped. MCP-1 -362C was associated with resistance to TB in the case-control collection (OR 0.83, P(corr) = 0.00017) and in the affected families (OR 0.7, P(corr) = 0.004). Linkage disequilibrium (LD) and logistic regression analyses indicate that, in Ghanaians, the effect results exclusively from the MCP-1 -362 variant, whereas the effect of -2581 may in part be explained by its LD with -362.

The 5-lipoxygenase (ALOX5)-derived lipid mediators leukotrienes and lipoxins have regulatory functions in inflammation by modulating activities of immune cells and cytokine production. Recently, it was shown in ALOX5-/- mice that host control of Mycobacterium tuberculosis is regulated by 5-lipoxygenase (5-LO). ALOX5 polymorphisms were genotyped in 1916 sputum-positive patients with pulmonary tuberculosis (TB) from Ghana and in 2269 exposed, apparently healthy controls. Polymorphisms of a variable number of tandem repeats (VNTR) of the ALOX5 promoter and of the exonic non-synonymous variant g.760G>A were analysed by fragment length determination and fluorescence resonance energy transfer, respectively, and DNA sequencing. Mycobacterial lineages of >1400 isolates were differentiated biochemically and genetically. Carriers of one variant (n repeats not equal 5) and one wild-type VNTR allele (n = 5) or of the exonic allele g.760A had a higher risk of TB [P(corrected) = 0.026, odds ratio (OR) 1.19 (95% CI 1.04-1.37) and P(corrected) = 0.026, OR 1.21 (95% CI 1.04-1.41), respectively]. The association of the exonic variant was stronger in infections caused by the mycobacterial lineage M. africanum West-African 2 [P(corrected) = 0.024, OR 1.70; (95% CI 1.2-2.6)]. Determination of haplotypes revealed the strongest associaton with TB for the 'non-5/760A' haplotype compared with the 'non-5/760G' haplotype (P = 0.003, OR 1.50). Our observation of an association of ALOX5 variants with susceptibility to TB contributes evidence of the importance of 5-LO products to the regulation of immune responses to M. tuberculosis.

SummaryThe current strategy for the interruption of transmission of lymphatic filariasis in areas where the disease is co-endemic with onchocerciasis is repeated annual mass treatment of endemic communities with ivermectin and albendazole. These drugs are not recommended for use in pregnancy. Pregnant women are excluded on the basis of their last menses. This exclusion criterion based on recall carries some inherent errors, leading sometimes to inadvertent exposure of foetuses to these drugs. This study set out to document the extent of inadvertent exposure of pregnant women to albendazole and ivermectin and assess the relative risk of congenital malformations because of inadvertent treatment with these drugs in early pregnancy. The study was conducted in the Ahanta West District of Ghana. Local pregnancy revelation norms were studied, followed by a household survey of women aged 15-45 years to assess drug administration coverage. All infants born within 42 weeks of the mass drug treatment were examined to document any congenital malformations. Mothers who had lost any such infants responded to a verbal autopsy to ascertain the probable cause of death. Health facilities and local Traditional Birth Attendants were also visited to review maternity records. Of 2985 women of childbearing age (15-49 years) who were interviewed, 343 were pregnant during the mass drug administration. The sensitivity of the last menstrual period in detecting pregnancy and thus being excluded from treatment was 0.854 (293 of 343). Some pregnant women 50 of 343 (14.6%) had thus been inadvertently treated. This represents 1.7% of women in fertile age group (15-49 years).Of the six children found with some congenital malformations in these communities, one had been exposed to the drugs in-utero. The relative risk for congenital malformation after exposure was 1.05 (P ¼ 1.0). Two of nine reported spontaneous abortions had been exposed to the drugs (P ¼ 0.62). We conclude that the local mode of excluding pregnancy in the current programme, while not perfect, is sufficiently effective and reliable for such a public health intervention; and importantly, that there is no evidence of a higher risk of congenital malformation or abortions in those who are inadvertently exposed.