Virulence factors of Moraxella catarrhalis outer membrane vesicles are major targets for cross-reactive antibodies and have adapted during evolution

Abstract

Moraxella catarrhalis is a common human respiratory tract pathogen. Its virulence factors associated with whole bacteria or outer membrane vesicles (OMVs) aid infection, colonization and may induce specific antibodies. To investigate pathogen-host interactions, we applied integrated bioinformatic and immunoproteomic (2D-electrophoresis, immunoblotting, LC-MS/MS) approaches. We showed that OMV proteins engaged exclusively in complement evasion and colonization strategies, but not those involved in iron transport and metabolism, are major targets for cross-reacting antibodies produced against phylogenetically divergent M. catarrhalis strains. The analysis of 31 complete genomes of M. catarrhalis and other Moraxella revealed that OMV protein-coding genes belong to 64 orthologous groups, five of which are restricted to M. catarrhalis. This species showed a two-fold increase in the number of OMV protein-coding genes relative to its ancestors and animal-pathogenic Moraxella. The appearance of specific OMV factors and the increase in OMV-associated virulence proteins during M. catarrhalis evolution is an interesting example of pathogen adaptation to optimize colonization. This precisely targeted cross-reactive immunity against M. catarrhalis may be an important strategy of host defences to counteract this phenomenon. We demonstrate that cross-reactivity is closely associated with the anti-virulent antibody repertoire which we have linked with adaptation of this pathogen to the host.

Interspecies Outer Membrane Vesicles (OMVs) Modulate the Sensitivity of Pathogenic Bacteria and Pathogenic Yeasts to Cationic Peptides and Serum Complement

“…Hence, it is of interest to investigate the protective potency of OMVs in the light of their specificity to react with a target cell. In the present study, we used our well-characterized OMVs from Moraxella catarrhalis Mc6 [4,21] as model vesicles and characterized their protective potential against model membrane-active agents in various interspecies combinations. First, we examined the protective activity of OMVs in bacterial intra- and interspecies systems and mode of observed protection, showing by HPLC-UV, zeta potential measurement, and o-nitrophenyl-β-D-galactopyranoside ONPG-based permeabilization assay, highly effective sequestration.…”

Neuropeptides SP and CGRP Diminish theMoraxella catarrhalisOuter Membrane Vesicle- (OMV-) Triggered Inflammatory Response of Human A549 Epithelial Cells and Neutrophils

“…Furthermore, since M. catarrhalis can induce apoptosis in primary alveolar epithelial cells and A549 cells through engagement of surface protein UspA1 to human CEACAM1 molecule [ 53 ], we can hypothesize that OMV-stimulated apoptosis could be at least in part mediated by this surface bacterial protein. Accordingly, as already mentioned, the presence of UspA1 in OMVs from Mc6 strain was confirmed by LC-MS/MS analysis [ 35 ]. Here, we have documented the expression of the CEACAM1 receptor on a certain fraction of A549 cells that also supports this hypothesis.…”

“…Furthermore, M. catarrhalis diminishes A549 inflammation through engagement of the CEACAM1-binding motif using bacterial surface ubiquitous protein UspA1—which in turn abrogates the TLR2- and NF- κ B-triggered inflammatory response [ 46 ]. Having confirmed both the presence of UspA1 (ligand for CEACAM1) in OMVs from Mc6 strain [ 35 ] and CEACAM1 expression on a certain fraction of A549 cells (this study), our results regarding proinflammatory action of M. catarrhalis OMVs do not contradict the previous studies since, (i) studied here, OMVs were potent stimulants only in the presence of IL-1 β and (2) the diminished, but not abolished, proinflammatory response was documented both for UspA1-containing and UspA1-deficient OMVs [ 4 ]. Since changes in the CEACAM1 expression patterns of different fractions of A549 cells can alter their diverse functions [ 38 ], the confirmation of CEACAM1 expression is essential in studies on the interaction between M. catarrhalis and this line.…”

“…The OMVs were collected from the culture supernatants following ultrafiltration and ultracentrifugation ( Figure 1(b) ). The proteomic analysis of Mc6 OMVs conducted by LC-MS/MS spectrometry revealed that pivotal outer membrane proteins packaged in these vesicles were OmpCD, OmpE, UspA1, Hag/MID, CopB, MhuA, TbpA, TbpB, LbpB, OMP M35, and MipA [ 35 ]. Mc6 OMVs contained LOS serotype A as determined previously [ 36 ].…”

Complement evasion by the human respiratory tract pathogens Haemophilus influenzae and Moraxella catarrhalis

“…M. catarrhalis produces large numbers of OMVs, and these nanoparticles carry most proteins also seen in the parent cell [94]. By using an integrated bioinformatic and immunoproteomic approach, the protein content in OMVs has been thoroughly analysed by Augustyniak et al [95]. Their study revealed that M. catarrhalis has adapted to the human host by a distinct path of evolution as compared to other Moraxella subspecies.…”