Nucleotide sequence analysis and serologic characterization of a 27-kilodalton Mycobacterium intracellulare lipoprotein

Abstract

Disseminated mycobacteremia resulting from Mycobacterium avium-Mycobacterium intracellulare complex (MAC) infections frequently contribute to the morbidity and mortality seen in AIDS patients. To better understand the immunopathology of MAC disease and to identify molecules that may have potential diagnostic and vaccine utility, an immunoreactive M. intracellulare protein (MI43) and the gene encoding this antigen were characterized. Southern blot hybridizations demonstrated that MI43 gene probes reacted only with genomic DNA from M. intracellulare, M. avium, and Mycobacterium asiaticum and not with DNA isolated from 11 other mycobacterial species. Nucleotide sequence analysis showed that the MI43 gene encodes a 27-kDa protein which contains a consensus bacterial lipoprotein processing sequence. Detergent-phase separations and metabolic labeling with [3H]palmitate also suggested that MI43 is a lipoprotein. Serological assays demonstrated that recombinant MI43 fusion proteins react with sera from M. avium-infected mice, sera from patients with MAC disease, and sera from patients with active tuberculosis. These results further suggest that mycobacterial lipoproteins are important immunogens that should be considered in the development of improved mycobacterial vaccines and diagnostic reagents.

Molecular and Immunological Analyses of the Mycobacterium avium Homolog of the Immunodominant Mycobacterium leprae 35-Kilodalton Protein

“…Intradermal injection of 10 g of each antigen was used for recall. specific, these were unable to distinguish between MAC and M. tuberculosis on an immunological basis (1,8,15,17,19,20,28). Such distinction would be of benefit in the early treatment of diseases caused by these organisms, as the currently used skin test reagents for detection of M. avium exposure lack specificity (10).…”

“…These studies have included the identification a number of protein antigens of the MAC, through the screening of expression libraries with anti-MAC monoclonal antibodies (MAbs) (18-20, 28, 29) or the identification of homologs of known antigens from other mycobacterial species (2,23). Some of these antigens, such as the secreted antigen 85B, are common to all mycobacteria (23), while others, including the immuno-genic 19-and 27-kDa lipoproteins of M. intracellulare, are restricted to a few mycobacterial species (19,20) and as such may be useful candidates for the specific detection of MAC infection. While a number of these antigens were immunogenic, being recognized by the host immune response or able to elicit delayed-type hypersensitivity (DTH) in MAC-sensitized guinea pigs, none were able to show adequate immunological discrimination between the MAC and M. tuberculosis (1,8,15,17,19,20,28).…”

Mycobacterium smegmatis laminin‐binding glycoprotein shares epitopes with Mycobacterium tuberculosis heparin‐binding haemagglutinin

“…As the mass spectrometry method used is known to dissociate non-covalently associated molecules, it suggests that the post-translational modification borne by the M. smegmatis histone-like protein is covalent. Attempts to label the M. smegmatis histone-like protein metabolically using [ 3 H]-palmitate were unsuccessful, suggesting that the protein does not bear a lipid modification (Nair et al, 1993). To characterize the modification further, the protein was hydrolysed in acidic conditions, and the hydrolysis products were analysed by gas chromatography combined with mass spectrometry.…”

Nucleotide sequence analysis and seroreactivities of the 65K heat shock protein from Mycobacterium paratuberculosis

“…However, the promoter sequence of the M. paratuberculosis gene was similar to that of the M. leprae gene but not identical to those of any of the other mycobacterial promoters that have been sequenced. Inverted sequences similar to those found upstream and downstream of PTB65K have also been identified for several mycobacterial structural genes (38,40,51).…”