Recently, gene coding for tryptophan-aspartate containing coat protein (TACO) has been recognized to play a crucial role in the survival of Mycobacterium tuberculosis within human macrophages. Since regulation of TACO gene is still poorly understood, the present study was addressed to explore the role of vitamins (A, C, D, and E) in TACO gene transcription. Such a study revealed that synergistic action of vitamin D-3 and retinoic acid (RA) had inherent ability to down-regulate TACO gene transcription in human macrophages. Based upon these results, we propose that synergistic action of RA + vitamin D may be of importance in the prevention/control of M. tuberculosis infection. (C) 2003 Elsevier Inc. All rights reserved.