A highly immunogenic putative Mycobacterium kansasii lipoprotein

The resurgence of tuberculosis, the emergence of multiple drug resistant tuberculosis, and the increasing prevalence of mycobacterial disease in AIDS patients have increased the importance of defining new mycobacterial antigens that can be utilized in the development of improved diagnostic reagents and more effective vaccines. In this report, a highly immunogenic Mycobacterium kansasii protein (MK35) and the gene encoding this antigen were characterized. MK35 gene probes reacted with genomic DNA from M. avium, M. bovis BCG, M. intracellulare and M. tuberculosis but not with DNA isolated from nine other mycobacterial species. Nucleotide sequence analysis showed that the MK35 gene encodes a 26 kDa protein which contains a consensus bacterial lipoprotein processing sequence. In addition, detergent-phase separation studies strongly suggested that MK35 is a lipoprotein. Skin test assays demonstrated that MK35 elicited a strong response in guinea pigs sensitized with M. kansasii but did not react in M. tuberculosis-sensitized guinea pigs. These results further suggest that mycobacterial lipoproteins are immunogenic antigens that should be considered in the development of new mycobacterial vaccines and diagnostic reagents.