The success of Mycobacterium tuberculosis lies in its ability to survive in macrophage phagosome and resist the killing mechanisms of macrophages. However, the precise survival strategies used by this bacillus remain to be elucidated. We have assumed that the survival of mycobacteria is mediated by the active production of mycobacterial proteins and this requires induction of mycobacterial promoters when the bacteria are inside macrophages. To study this phenomenon, a Host Pathogen Interaction Analysis vector (pHP85) was developed in our laboratory. I have constructed a genomic library of local isolates in M. tuberculosis H37Ra and M. bovis BCG using this vector. The library was used to infect THP-1 cells and many macrophage induced promoters were identified. I am also working on the characterization of few selected promoters and their downstream genes.

We are trying to analyze differences between the type strains of M. tuberculosis and field strains at the genomic level using molecular techniques. Genomic fluidity among M. tuberculosis isolates from Kerala is studied based on nonrandom deletions like RDs (Region of Difference), RvDs and TbD1 (Tuberculosis specific Deletion 1). Subtractive hybridization is also employed to find out genetic variability among the isolates. The regions that show differences will be sequenced and used as probes to pull out full-length clones. The entire genes will be cloned, sequenced and functionally characterized.

Increasing drug resistance is major problem in Tuberculosis. The target genes of most of the drugs and the mutations that cause drug resistance have been described. We are identifying the mutations that are present in the local strains in such genes and will make a database on the available mutations that confer drug resistance to develop a molecular assay for drug resistance.Rapid identification of mycobacteria is an urgent requirement for efficient therapy. Since the insertion sequence IS6110 is absent in a large percentage of local strains, we are working on a multiplex PCR for genus and species specific identification of mycobacteria. This will be tested in field samples.We are also screening plant based compounds for generating leads in the drug discovery program running in our laboratory.

The main objective of my study is to obtain a concrete authentic data on the different fingerprint pattern of the local isolates of Mycobacterium tuberculosis from Kerala, using IS6110 and MIRU-VNTR fingerprinting and to evaluate the epidemiological relation between the isolates.
We are also trying to identify peptide epitope(s) which could be used to develop a serodiagnosis for easy and early detection of tuberculosis infection.

An effective vaccine against Tuberculosis is an urgent necessity. BCG has given variable results in different regions. One of the probable reasons for the failure of BCG is that it contains immunosuppressive as well as immunoenhancing epitopes. We would like to screen for the immunoenhancing property of selected mycobacterial epitope in a background that is free of any suppressive epitope and in a relatively “clean” system. Therefore we are evaluating the immunostimualtory activity of selected mycobacterial antigens in a Hepatitis B antigen background and will compare it to the effect of the antigen in a mycobacterial background.

Mycobacterium interacts with macrophages and is able to modulate them for their own benefit. I am interested in characterizing mycobacterial genes that can modulate macrophage functions and in identifying the mechanisms by which these modulations take place.

I am interested in identifying the pathways that are involved in host-pathogen interaction in case of M. tuberculosis-macrophage interactions using field isolates and macrophage cell lines.