Characterizing the Mycobacterium tuberculosis Rv2707 protein and determining its sequences which specifically bind to two human cell lines.

The Rv2707 gene encoding a putative alanine- and leucine-rich protein was found to be present in all Mycobacterium tuberculosis complex strains (by PCR) and its transcription was shown by RT-PCR in all but M. bovis and M. microti. Antibodies raised against Rv2707 peptides specifically recognized the native protein by Western blot and were able to locate this protein on the M. tuberculosis membrane by immunoelectron microscopy. A549 and U937 cells lines were used in binding assays involving synthetic peptides covering the whole Rv2707 protein. High A549 cell-binding peptide 16083 (281 QEEWPAPATHAHRLGNWLKAY 300) was identified. Peptides 16072 (61 LFGPDTLPAIEKSALSTAHSY 80) and 16084 (301 RIGVGTTTYSSTAQHSAVAA 320) presented high specific binding to both A549 and U937 cells. Cross-linking assays revealed that peptide 16084 specifically bound to a 40-kDa and a 50-kDa U937 cell membrane protein. High activity binding peptides (HABPs) 16083 and 16084 were able to inhibit M. tuberculosis invasion of A549 cells. Our results suggest that these sequences could be part of the binding sites used by the bacillus for interacting with target cells, and thus represent good candidates to be tested in a future subunit-based, multiepitope, antituberculosis vaccine.