Assessment of the Protective Effect of the Humoral Immune Response against Major Moraxella catarrhalis Surface Antigens on Otitis Media Manifestation in Egyptian Children

Abstract

Purpose: Moraxella catarrhalis is a human-restricted mucosal pathogen that is recognized as a common cause of acute otitis media in young children. It also leads to exacerbation of chronic obstructive pulmonary disease in adults. The financial burden imposed by M. catarrhalis colonization and infection on the global health care systems is significantly rising. However, till now there is no licensed vaccine against M. catarrhalis. In this study we aim at investigating the association between the serum antibodies' response against chosen major M. catarrhalis surface antigens and the incidence of acute otitis media in Egyptian children. Methods & Materials: Nasal swabs were collected for bacterial isolation and blood samples were obtained for antibody response evaluation from children admitted to an Egyptian educationcal hospital. Eighty-one samples were obtained from children diagnosed with otitis media (OM) and 37 samples from children showing other symptoms. Identification and characterization of M. catarrhalis was performed. Sera of M. catarrhalis positive samples were separated and stored. Preparation of bacterial antigens was performed via extraction of outer membrane vesicles, and then ELISA technique was used to evaluate the humoral immune response produced against three major M. catarrhalis outer membrane proteins. Results: M. catarrhalis was present in 26% of otitis media samples and 51.5% of non-otitis media ones. IgG antibodies against the ubiquitous surface protein A1 (UspA1) were significantly higher in non- otitis media children than those having otitis media. Antibodies produced against other surface antigens like the ubiquitous surface proteins A2 (UspA2) and the M. catarrhalis outer membrane protein B (CopB) were generally higher in non-otitis media group but not statistically significant. Conclusion: The high antibody level against the UspA1 surface protein of M. catarrhalis was associated with decrease in the incidence of acute otitis media among the collected samples. The findings suggest that antibodies against the UspA protein could be playing some protective role against M. catarrhalis infections.