Resumo

Mycoplasma hyopneumoniae and Mycoplasma flocculare are closely related genetically and both colonize the swine respiratory tract. Despite of their similarities, M. hyopneumoniae is pathogenic, being to, the causative agent of enzootic porcine pneumonia, while M. flocculare is a commensal bacterium. In this work, we are performing a comparative analysis of ortholog surface proteins between these two species, searching for differences that could explain the virulence of M. hyopneumoniae and the lack of it in M. flocculare. Surface proteins mediate interactions between bacteria and their host species and can be antigens with potential use in diagnostic or vaccination and potential targets for the development of new therapeutic drugs for pathogenic mycoplasmas. A total of 170 ortholog pairs of putative surface proteins were individually aligned, using ClustalW algorithm available in the MEGA 5.05 software package, and had their topologies predicted, using the TopPred, Phobius and TMHMM programs. This allowed the identification of 148 proteins whose orthologs in the two species present differences in putative extracellular domains in terms of insertions/deletions of amino acid stretches (of 5 aa or more) and/or lower similarity (at least 30% lower than that of adjacent sequences). Among these proteins, 3 pairs of hypothetical proteins were selected for additional studies, because their differences presented in extracellular portion, which could be in contact with host immune system. The differential domains of these proteins will be expressed in Escherichia coli and their recombinant versions will be functionally studied using immunological assays and protein-protein interaction assays in order to assess their possible involvement with presence or absence of the pathogenicity.