No abstract

Vitamin D deficiency is associated with susceptibility to tuberculosis (TB) in HIV-uninfected people in Europe, but it is not known whether such an association exists among HIV-infected people in subtropical Africa. We conducted a cross-sectional study to determine whether vitamin D deficiency was associated with susceptibility to active TB in and HIV-infected (n = 174) black Africans in Cape Town, South Africa. We also investigated whether there was evidence of seasonal variation in vitamin D status and TB notifications in this setting over an 8-y period.nmol/L) was present in 232 (62.7%) of 370 participants and was associated with active TB in both HIV-uninfected (odds ratio = 5.2, 95% confidence interval: 2.8-9.7; P < 0.001) and HIV-infected (odds ratio = 5.6, 95% confidence interval: 2.7-11.6; P < 0.001) people. We have previously reported that vitamin D deficiency is associated with susceptibility to TB in London and that this association is modified by polymorphisms in the vitamin D receptor and vitamin D binding protein (8,9). We have also shown that in vivo vitamin D supplementation enhances immunity to mycobacteria both in healthy people (10) and in a genetically defined subgroup of patients with active TB (11). Reports of seasonal variation in the prevalence of vitamin D deficiency (12) and TB incidence (13) in the United Kingdom provide further evidence that low vitamin D status may compromise antimycobacterial immunity in this setting.The prevalence of profound vitamin D deficiency among TB patients in tropical Africa is much lower than in Europe [reported in 0.3-11.2% of patients with TB in tropical Africa (14-17) vs. 64-84% of patients with TB in ]. The prevalence of vitamin D deficiency in TB patients with and without HIV infection in subtropical Africa has not previously been reported. There is particularly good reason to investigate this question in Cape Town, South Africa, because TB incidence in Cape Town is higher than elsewhere in South Africa (21) and the ability of sunlight to synthesize vitamin D is compromised during the winter in Cape Town (latitude 33°south) but not in Johannesburg (latitude 26°south) (22). We therefore conducted an observational study to determine whether vitamin D deficiency is associated with susceptibility to active TB in HIVinfected and HIV-uninfected adults in Cape Town and to investigate whether there is evidence of seasonal variation in vitamin D status and TB notifications in this setting.

Globally, far more men than women have tuberculosis. Although the cause of this bias is uncertain, epidemiological factors have historically been considered the driving force. Here, we discuss evidence that biological differences between the sexes may also be important and can affect susceptibility to mycobacterial infection. We discuss the possible underlying mechanisms, with particular focus on how sex hormones modulate the immune responses necessary for resistance to tuberculosis. Studying these differences may provide valuable insight into the components that constitute an effective immune response to this deadly pathogen.