Antibodies against outer membrane proteins of Moraxella catarrhalis and nontypeable Haemophilus influenzae cross-react with various pathogens of human respiratory tract

Abstract

Event Abstract Back to Event Antibodies against outer membrane proteins of Moraxella catarrhalis and nontypeable Haemophilus influenzae cross-react with various pathogens of human respiratory tract Daria Augustyniak1*, Joanna Bonarowska1, Paweł Mackiewicz2 and Zuzanna Drulis-Kawa1 1 University of Wroclaw, Department of Pathogen Biology and Immunology, Institute of Genetics and Microbiology, Poland 2 University of Wroclaw, Department of Genomics, Faculty of Biotechnology, , Poland Introduction: Moraxella catarrhalis and nontypaeble Haemophilus influenzae are important, human-restricted respiratory tract pathogens [1,2]. Outer membrane proteins (OMPs) of these bacteria are their most immunogenic antigens and targets for the host immune response [3,4]. The goal of the study was to quantitatively and qualitatively assess the reactivity of anti-OMPs antibodies against cross-reactive and surface-exposed epitopes of other important pathogens of human respiratory tract. Materials and Methods: Antisera were obtained from six groups of mice, each immunized with OMPs isolated from different Moraxella catarrhalis strains (anti-OMPMc sera) or nontypeable Haemophilus influenzae strains (anti-OMPNTHi sera). OMPs were isolated using Zwittergent 3-14 procedure [4]. The titers of cross-reactive antibodies were measured by whole-cell ELISA whereas their specificities with bacterial OMPs was confirmed by Western-blot according to described methods [4]. The studied pathogens were: Pseudomonas aeruginosa including cystic fibrosis (CF) and non-cystic fibrosis (non-CF) strains, Burkholderia cepacia (CF), Acinetobacter baumanii, Haemophilus parainfluenzae and additionally Candida albicans. To find potential cross-reactive antigens and epitopes in these pathogens, we performed BLAST searches of their protein databases using as a query M. catarrhalis and H. influenzae OMPs for which immune reaction was proved. Results: We found statistically significant homologues especially to Moraxella OMP CopB, E and CD as well as to Haemophilus OMP P1, P4, D15 and Tbp1. Majority of the found homologues are peripheral or outer membrane proteins and could be involved in the cross immune reactions. In whole-cell ELISA we found cross-reactive epitopes in all studied pathogens of respiratory tract. We found that among analyzed anti-OMPMc and anti-OMPNTHi sera, the several were medium or highly cross-reactive. The cross-reactive titers in anti-OMPMc sera were in the range 1:200 – 1:1500 that was 500 – 1000-fold lower than titers for homologous strains. The cross-reactivity of anti-OMPNTHi sera were in the range 1:2000 – 1:11000 that was 4 – 20-fold lower than for homologous counterparts. The reactivity of some cross-reactive antibodies was confirmed with OMPs of tested strains. The differences in recognition of cross-reactive surface epitope between CF and non-CF strains were dependent on used antisera rather than particular strain. Within anti-OMPMc sera the weakest reactivity was usually detected for A. baumanii whereas the highest for C. albicans. In the case of anti-OMPNTHi sera the weakest reactivity was observed for C. albicans and the highest for H. parainfluenzae. The sera with greater cross-reactive potency were found within anti-OMPNTHi ones. Conclusion: The results indicate that IgG antibodies induced against OMPs of particular M.catarrhalis and H.influenzae recognize cross-reactive surface-exposed epitopes in multiple strains of respiratory pathogens. The biological role of this phenomenom is supposed to be confirm in antibody-dependent functional assays. The presence of cross-reactivity should be take under consideration in immunodiagnostic tests for respiratory pathogens.