We have shown that therapeutic doses of Vitamin D (in the form of 2 doses of cholecalciferol at monthly intervals), given to patients with active pulmonary TB, can lead to proportionately greater weight gain and more rapid radiographic clearing of disease as compared to placebo.
It has recently been proposed that vitamin D accelerates resolution of host inflammatory responses and this may contribute to the improvement observed in vitamin D supplemented TB therapy
. Here we illustrate that vitamin D supplementation enhances mycobacterial-antigen induced IFN-g secretion in patients with Deficient 25-hydroxyvitamin D levels, thereby improving cell mediated immunity against M. tuberculosis.
25-hydroxyvitamin D is recognized as an important immune-modulator in TB. 1, 25 (OH) 2 D3 binding with VDRs activates cathelicidin-mediated mycobacterial killing
[1, 2] whilst 25-hydroxyvitamin D deficiency increases the susceptibility and vulnerability to TB
[3, 4]. G interferon (IFN-γ) is a proinflammatory cytokine, which plays a critical role in resistance to MTB infection
. Infection with MTB induces T lymphocytes, natural killer cells and alveolar macrophages to express IFN-g and induces IFN-γ-driven monokines that regulate granuloma formation
. IFN-g responses have been shown to be depressed in patients with advanced forms of tuberculosis
. We observed a significant improvement in MTBs-induced IFN-g responses after 12 weeks of ATT in vitamin D ‘Deficient’ patients who received 25-hydroxyvitamin. This is the first vitamin D supplementation study where groups have been stratified into those with differing disease severity and also according to their baseline serum 25-hydroxyvitamin D levels.
Previous reports by Ulrichs et al. have shown that IFN-g producing cells against ESAT6 in tuberculosis patients increase post-tuberculosis therapy
. However, we were unable to demonstrate any difference in ESAT6-induced IFN- γ responses between patients prior to and post-treatment. This is in concordance with a recent report by Coussens et al.
 that did not show any change in ESAT-6 induced IFN-g in patients post-antituberculous therapy. ESAT6 and culture filtrate protein 10 (CFP10) are both encoded by the region of difference 1 (RD1) present in M. tuberculosis and in virulent M. bovis, but absent from M. bovis BCG and environmental mycobacteria
. Antigen based interferon g release assays (IGRAs) have a varied sensitivity in endemic and non-endemic settings, attributable to exposure to environmental mycobacterial and M. tuberculosis and resulting T cell IFN-g responses
. M. tuberculosis whole sonicate (MTBs) contains cross reactive epitopes to M. bovis BCG vaccine strain and environmental mycobacteria and therefore, can induce potent cytokine responses from T cells, macrophages and other polymorphonuclear cells. MTBs induced responses have been useful in differentiating severity of disease in TB. Patients with advanced disease display decreased IFN-g responses
. We observed that after 12 weeks of ATT, the Class III severity groups had significant increases in MTBs-induced IFN-g responses. This increase in mycobacterial-antigen induced IFN-g responses represents host immunity in patients with advanced pulmonary disease, possibly leading to improved resolution of the disease. Further analysis of to determine the impact of host 25- hydroxyvitamin D levels on immune recovery revealed that in patients who received vitamin D supplementation, MTBs-induced IFN-g secretion was significantly increased after 12 week of anti-tuberculous therapy only in patients who had ‘Deficient’ 25-hydroxyvitamin D levels (< 20 ng/mL) at initiation of treatment whilst this immune recovery was absent for TB patients with ‘Deficient’ 25- hydroxyvitamin D levels in the placebo group. This data suggests a role for 25-hydroxyvitamin D supplementation in boosting host immunity particularly in those with deficient 25 hydroxyvitamin D levels. It is possible that only patients with ‘Deficient’ 25 hydroxyvitamin D levels showed an improvement perhaps due to a critical level of 25-hydroxyvitamin D required by the host for optimal activation of IFN-g secretion and because this limit was already reached in the other 25-hydroxyvitamin D groups where no enhancement of mycobacterial antigen-induced IFN-g response was observed.
Weight gain is routinely followed as an outpatient marker of clinical improvement in TB and we observed improvements in clinical status; i.e.; weight gain compared to the placebo group. This corresponds with the earliest reports of the benefits of vitamin D in TB patients published in 1848
 that describes disease arrest, weight gain and reduction in mortality in patients with TB treated with cod liver oil compared to standard therapy alone. More recently, Martineau et al. demonstrated that a single oral dose of 2.5 mg (100,000 IU) of ergocalciferol significantly reduced growth of mycobacteria
. A randomized, placebo controlled study on 67 Indonesian patients, by Nursyam et al.
 reported that pulmonary TB patients given 420,000 IU of vitamin D over 6 weeks had significantly higher sputum conversion rates as compared to placebo (p 0.002). Martineau et al.
 showed that 100,000 IUs of 25-hydroxyvitamin D3 supplementation significantly improved sputum conversion rates in patients with the Taq1 25-hydroxyvitamin D receptor polymorphism of the tt genotype. We speculate that this occurred due to broader effects of 25-hydroxyvitamin D on muscle, vascular and homeostasis
We also found that the vitamin D treatment group had lesser disease (compared to placebo) by chest radiography after 12 weeks of therapy. This finding is consistent with a recent small placebo controlled trial on 24 children in Egypt that reported greater clinical and radiographic recovery after 1000 IUs of oral vitamin D supplementation
 and a case report of an African –American patient with refractory, drug sensitive TB who improved only after being treated with 1,200,000 IU of ergoclaciferol
However, two recently published large randomised, controlled trials by Martineau
 and Wejse et al.
 found no difference in clinical outcomes or mortality after 10 mg (400,000 IU) of 25-hydroxyvitamin D3 and 300,000 IUs of cholecalciferol or placebo were given to 146 pulmonary TB patients in London, United Kingdom and 365 TB patients in Guinea-Bissau. It maybe speculated that the differences in response to 25-hydroxyvitamin D seen between our study and Wejse’s could be due to variations in VDR polymorphisms, variability in 25-hydroxyvitamin D dosages or differing levels of baseline serum 25-hydroxyvitamin D levels.
We found 25-hydroxyvitamin D supplementation to be very safe, even in patients without deficiency. Only two patients in the vitamin D arm died during the study; one death was due to respiratory failure occurring within the initial 2 weeks of antituberculous therapy. It can be speculated whether this was a paradoxical response leading to acute lung injury.
We used a ‘higher’ dose than the 2 recent negative studies reported by Wejse and Martineau et al., but closer to therapeutic recommendations
[29–31]. We speculate that this may account for the differences observed in the 2 groups at 12 weeks. We consider it a limitation of our study that we were unable to follow our patients to the end of treatment (6 months). It is possible that the benefits of 25-hydroxyvitamin D replacement may become more apparent between the groups with longer follow up.
Another limitation of our study is that we did not collect information on dietary intakes However the study groups were well matched at enrolment and represented a variety of socioeconomic and ethnic groups, which may reduce the possibility that one study arm was disproportionately better nourished.