Role of Oral Vitamin D as an Adjunct Therapy in Category I Pulmonary Tuberculosis Along With Assessment of Immunological Parameters. (Double-blind, Randomized, Placebo-Controlled, Clinical Trial)

Tuberculosis and vitamin D deficiency are important public health problems in India. In recently published studies from our center, up to 90% of the apparently healthy subjects in Delhi were classified either as as vitamin D insufficient or deficient by using serum 25(OH)D cut off levels of 20 ng/ml and 32 ng/ml respectively. Before the advent of effective antitubercular therapy, patients with tuberculosis were advised treatment and rest at sanatorium where sunshine was available in plenty. In the western literature, there have been reports associating vitamin D deficiency with tuberculosis in terms of incidence and beneficial response following addition of vitamin D to antitubercular therapy. A few pilot studies have shown that sputum conversion rate is higher in patients with tuberculosis supplemented with vitamin D.

In the above context the mechanisms linking vitamin D deficiency and its effect on tuberculosis are currently under investigation. In order to understand the link two types of studies have been conducted (a) clinical studies associating vitamin D deficiency and tuberculosis and (b) in-vitro assessment of molecular immune changes related to vitamin D exposure. With the currently available knowledge, the linkage between the two disorders is being explained by the broad role of vitamin D deficiency in modulation of cell-mediated immunity.

Patients with military tuberculosis are characterized by decreased levels of Th1 cytokines and increased levels of IL-10 compared with the healthy infected and noninfected controls. Current literature suggests that long-term control of M. tuberculosis infection is associated with elevated Th1 responses and concomitant inhibition of the Th2 response

Peripheral blood mononuclear cells have been shown to express vitamin D receptors. Incubation of macro¬phages with physio¬logical concentration of 1,25 (OH)D [10-9M] results in inhibition of intracellular growth of Mycobacterium tuberculosis. 1,25-dihydroxycholecalciferol, has significant immunomodulatory effects leading to (a) shift in cytokine profile of T-helper (Th1 to Th2) and (b) reduced antigen presentation, reduced production of Th1-promoting cytokines, reduced expression of co-stimulatory molecules in the antigen-presenting cell. In addition, it was demonstrated that the addition of vitamin D3 derivatives inhibits the differentiation of IFN-gamma-producing Th1 cells while it augments the differentiation of IL-4- or IL-10-producing Th2 cells.

There are no systematic data from our country assessing association between vitamin D deficiency and tuberculosis and the possible role of vitamin D related modulation in the tuberculosis specific cellular immune response. The present study has been planned with the following hypothesis