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Are the PE‐PGRS proteins of Mycobacterium tuberculosis variable surface antigens?
Author(s) -
Banu Sayera,
Honoré Nadine,
SaintJoanis Brigitte,
Philpott Dana,
Prévost MarieChristine,
Cole Stewart T.
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.02813.x
Subject(s) - biology , mycobacterium tuberculosis , antigen , epitope , microbiology and biotechnology , membrane protein , gene , tuberculosis , genetics , medicine , pathology , membrane
Summary Mycobacterium tuberculosis H37Rv contains 67 PE‐PGRS genes, with multiple tandem repetitive sequences, encoding closely related proteins that are exceptionally rich in glycine and alanine. As no functional information was available, 10 of these genes were selected and shown to be expressed in vitro by reverse transcription–polymerase chain reaction (RT–PCR). Antibodies against five PE‐PGRS proteins, raised in mice by DNA vaccination, detected single proteins when the same plasmid constructs used for immunization were expressed in epithelial cells or in reticulocyte extracts, confirming that the PE‐PGRS proteins are antigenic. As expected from the conserved repetitive structure, the antibodies cross‐reacted with more than one PE‐PGRS protein, suggesting that different proteins share common epitopes. PE‐PGRS proteins were detected by West‐ern blotting in five different mycobacterial species ( M. tuberculosis , M. bovis BCG, M. smegmatis , M. marinum and M. gordonae ) and 11 clinical isolates of M. tuberculosis. Whole‐genome comparisons of M. tuberculosis predicted allelic diversity in the PE‐PGRS family, and this was confirmed by immunoblot studies as size variants were detected in clinical strains. Subcellular fractionation studies and immunoelectron microscopy localized many PE‐PGRS proteins in the cell wall and cell membrane of M. tuberculosis . The data suggest that some PE‐PGRS proteins are variable surface antigens.