P27-PPE36 (Rv2108) Mycobacterium tuberculosis Antigen – Member of PPE Protein Family with Surface Localization and Immunological Activities

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Le Moigne, Vincent | Mahana, Wahib

Edité par CCSD ; InTech -

International audience. The largest and most distinctive class of mycobacteria-specific genes encode a group of 167 proteins of repetitive sequence belonging to the pe and ppe families. The uniqueness of the ppe genes is illustrated by the fact that these genes are restricted to mycobacteria (Cole et al.,1998; Voskuil et al., 2004 (b)). The Rv2108 gene belongs to this family and furthermore is highly specific for the Mycobacterium tuberculosis (Mtb) complex group of mycobacterium (containing notably Mycobacterium africanum, Mycobacterium canettii, Mycobacterium microti,Mycobacterium pinnipedi, Mycobacterium bovis and M. bovis BCG strain). This gene was described by Chevrier et al., (2000) and used as a molecular probe to develop a rapid test for the detection and identification of this group of mycobacteria. Rv2108 is a gene coding for the protein P27-PPE36, member of the PPE protein family of Mycobacterium tuberculosis, a group of protein thought to be of immunological significance despite the fact that the exact role of the PPE proteins stills unknown.The P27-PPE36 protein was produced as a recombinant protein in Escherichia coli. Theexpressed protein is immunologicaly active and recognized by sera from infected patients. It was used to generate specific polyclonal and monoclonal anti-P27-PPE 36 antibodies. These antibodies were used to study the immunochemical characterization of P27-PPE36, to verify its presence in Mycobacterium bovis BCG and clinical Mtb isolates, and to characterize and localize it in a parietal position in M. tuberculosis cells.Using an ELISA test we found that the antibody immune response to P27-PPE36 in the sera of patients was dominated by an IgA antibody response accompanied by the absence of IgG response.The immune response against the P27-PPE36 protein was investigated in mice. It wasstudied in the context of different pathogen associated molecular patterns (PAMPs).BALB/c mice were immunized either with the P27-PPE36 recombinant protein in Freund’sadjuvant or in phosphate saline buffer (PBS), with a pcDNA3 plasmid containing the geneencoding the P27-PPE36 protein, or with the Escherichia coli bacteria expressing the P27-PPE36 protein genetically fused into the flagellin. We found that P27-PPE36 expressed intothe flagellin led to the strongest cellular responses, where we obtained the highestproduction of IFN- and cell proliferation, an indication of specific Th1-like orientation ofthe immune response.

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