Are the PE‐PGRS proteins of <i>Mycobacterium tuberculosis</i> variable surface antigens?

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…