Cholesterol has been reported to play an important role during Mycobacterium tuberculosis infection and during its dormant state inside the host. We present the determination of proteomic profiles of M. tuberculosis H37Rv in the presence of cholesterol as the sole carbon source under exponential growth and in two in vitro dormancy phases (NRP1 and NRP2). Using 2D-PAGE, we detected that M. tuberculosis expressed a high diversity of proteins in both exponential and non-replicative phases. We also found that cholesterol was involved in the overexpression of some proteins related to sulfur metabolism (CysA2), electron transport (FixB), cell wall synthesis (Ald), iron storage (BfrB), protein synthesis (Tig and EF-Tu) and dormancy maintenance (HspX and TB 31.7). According to our results we propose that proteins Ald, BfrB, FadA5 and TB31.7 are likely to play a fundamental role during in vitro dormancy of M. tuberculosis in the presence of cholesterol, helping to counteract its intracellular hostile microenvironment.

ICL could be used in combination with other M. tuberculosis antigens to improve the sensitivity and specificity of current serological TB diagnostic methods.

Leprosy is an infectious disease caused by Mycobacterium leprae, which is a noncultivable bacterium. One of the principal goals of leprosy research is to develop serological tests that will allow identification and early treatment of leprosy patients. M. habana is a cultivable nonpathogenic mycobacterium and candidate vaccine for leprosy, and several antigens that cross-react between M. leprae and M. habana have been discovered. The aim of the present study was to extend the identification of cross-reactive antigens by identifying M. habana proteins that reacted by immunoblotting with antibodies in serum samples from leprosy patients but not with antibodies in sera from tuberculosis (TB) patients or healthy donors (HDs). A 28-kDa antigen that specifically reacted with sera from leprosy patients was identified. To further characterize this antigen, protein spots were aligned in two-dimensional polyacrylamide gels and Western blots. Spots cut out from the gels were then analyzed by mass spectrometry. Two proteins were identified: enoyl-coenzyme A hydratase (lipid metabolism; ML2498) and antigen 85B (Ag85B; mycolyltransferase; ML2028). These proteins represent promising candidates for the design of a reliable tool for the serodiagnosis of lepromatous leprosy, which is the most frequent form in Mexico.Intradermal immunization with killed Mycobacterium leprae renders mice immune to infection with viable M. leprae (28). This protection is long lasting and systemic. However, when other mycobacteria are used to immunize mice against infection with viable M. leprae bacilli, they have been shown to be either ineffective (i.e., Mycobacterium duvalii) or to confer only partial protection (i.e., M. bovis BCG) (29). In 1985 and then 1989, Mycobacterium habana TMC 5135 was found to be as effective as M. leprae in protecting mice against footpad infection (32, 33). This was surprising, since Shepard et al. found that among a large panel of mycobacteria tested, only M. leprae and BCG were able to confer protection (30).M. habana was first described following its isolation from 35 cases of pulmonary tuberculosis (TB) (40); subsequently, it was found to be closely related to the species Mycobacterium simiae serovar 1 and is now known as M. simiae serotype 1 (20). In 1996, Khoo et al. demonstrated that M. habana TMC 5135 and several M. simiae strains differed in their polar glycopeptidolipid (GPL) compositions, conferring sufficient specificity for identification of M. habana as a distinct serotype of M. simiae (14).M. habana is a cultivable organism, protects mice against Mycobacterium ulcerans challenge, and offers consistent protection against infection with Mycobacterium tuberculosis H37Rv and other strains of M. tuberculosis (11,12). Some studies suggest that the secretory antigens released by actively growing M. habana bacilli are protective against M. tuberculosis infections (6,8). Recent experimental data indicate that M. habana TMC 5135 and M. habana IPK-220 strains, which differ in the fine structure of their mycolates, a...

Mycobacterium leprae , a non-cultivable bacteria, is the causative agent of leprosy. Despite huge effort from WHO leprosy remains a public health problems in some parts of the world. One of the principal goals of leprosy research is to develop serological tests that will allow identification and early treatment of leprosy patients. In this work, M. habana a cultivable non-pathogenic mycobacterium and candidate vaccine for leprosy, was used to obtain soluble antigenic extracts (MHSE). By Western blot (WB) analysis MHSE proteins were reacted with sera form lepromatous leprosy patients (LL), active tuberculosis patients (TB) and healthy donors (H) from an endemic leprosy area. LL sera diluted 1:2,000 showed reactivity with a 28-30 KDa doublet antigen in MHSE. No reactivity with these bands was observed at 1:2,000 or lower sera dilutions of TB or H donors. After performing two dimension PAGE and WB analysis with the same sera, the doublet band was shown to have several spots. Further characterization was done using Tandem Mass Spectrometry (LC/ESI-MS/MS) and two proteins were identified: enoyl- coenzyme A hydratase (lipid metabolism) and antigen 85B (Ag85B, mycolyltransferase). These proteins represent promising candidates for the design of a reliable tool for the serodiagnosis of the infectious form of leprosy.