Determining Protein D Antibody Suppression by OMP26.

Acute otitis media (AOM) is one of the most prevalent diseases in young children, and healthcare-related costs are estimated to be $6 billion in the US each year. AOM is also the most common ailment for which antibiotics are prescribed. Considering all of these challenges and the rising concerns over antibiotic resistant bacteria, it is important to develop a vaccine to protect against AOM. Two proteins, OMP26 and Protein D, are currently leading protein vaccine candidates for one of the main bacterial causes of AOM: nontypeable Haemophilus influenzae (NTHi). On their own, the proteins produce a robust antibody response in mice. However, we recently showed that when the two proteins are combined into a single formulation, Protein D antibodies are suppressed. We first hypothesized that OMP26 and Protein D must physically interact to induce such suppression. However, here, we describe the results of our studies, which employed column chromatography and other biochemistry techniques, which suggest that OMP26 and Protein D do not directly interact. Further studies are underway to determine the mechanism behind Protein D antibody suppression and to assess several experimental strategies to overcome the suppression.