The PPIase Active Site of Legionella pneumophila Mip Protein Is Involved in the Infection of Eukaryotic Host Cells

Abstract

We analysed eight monoclonal antibodies (mAbs) directed against the Mip (macrophage infectivity potentiator) protein, a virulence factor of the intracellular pathogen Legionella pneumophila. Mip belongs to the FK506-binding proteins (FKBPs) and exhibits peptidyl prolyl cis/trans isomerase (PPIase) activity. Five of the mAbs recognised epitopes in the C-terminal, FKBP-homologous domain of Mip, which is highly conserved among all Legionella species. Upon immunological binding to Mip, all but one of these mAbs caused inhibition of the PPIase activity in vitro. mAb binding to the N-terminal domain of Mip did not influence its enzymatic activity. All but one of the PPIase inhibiting mAbs were able to significantly inhibit the early establishment and initiation of an intracellular infection of the bacteria in Acanthamoeba castellanii, the natural host, and in the human phagocytic cell line U937. These data demonstrate for the first time that for the virulence-enhancing property of the L. pneumophila Mip protein, an intact active site of the enzyme is an essential requirement.

A Burkholderia pseudomallei Macrophage Infectivity Potentiator-Like Protein Has Rapamycin-Inhibitable Peptidylprolyl Isomerase Activity and Pleiotropic Effects on Virulence

“…However, subsequent work on a parvulinlike PPIase indicated that vanishingly low levels of enzyme activity might suffice to ensure protection against loss of PPIase function (16). Consequently, targeting the PPIase domain of L. pneumophila Mip with activity-neutralizing monoclonal antibodies inhibited Legionella infection of cells, and FK506 or rapamycin inhibited transmigration of L. pneumophila across NCl-H292 lung epithelial cells (19,42). In addition, removal of the PPIase domain of L. pneumophila Mip attenuated virulence in guinea pig model of infection (25).…”

Opportunistic pathogens enriched in showerhead biofilms

“…L. pneumophila constitutes a broad relatedness group, however, so detection of a representative of the group does not indicate a pathogen. Because of the potential human health implication of this detection, we conducted quantitative PCR (QPCR) assays with a L. pneumophila-specific primer pair that targets a pathogenesis gene, the macrophage infectivity potentiator (mip) gene (20)(21)(22)(23)(24), to screen a subset of samples. Thirty-six samples (16 water and 20 swabs, representing 10 cities) were tested in duplicate reactions, including samples with positive L. pneumophila detection by sequence.…”

The Neisseria meningitidis Macrophage Infectivity Potentiator Protein Induces Cross-Strain Serum Bactericidal Activity and Is a Potential Serogroup B Vaccine Candidate

“…Although contradictory evidence has been presented for the requirement of the active enzyme site within the protein for virulence of Legionella (22,33), many of the studies described above clearly demonstrated that expression of microbial MIP (and homologues) appeared to have direct relevance to the survival of important human pathogens that have intracellular stages in their life cycles (20).…”