15 - A Novel Approach to Bacterial Vaccines: Haemophilus influenzae as a Paradigm

Background: The H. influenzae type b vaccines target the type b capsule and therefore have no impact on the nontypable (unencapsulated) H. influenzae (NTHi). NTHi has become the most common cause of otitis media and is the most common isolate from patients with exacerbations of Chronic Obstructive Pulmonary Disease (COPD). Therefore, NTHi is an appropriate target for vaccine development.

Methods: To characterize potential vaccine targets, the core outer proteins of NTHi present in the available sequenced genomes were identified through genomic bioinformatics. The structures of the outer proteins were analyzed through comparison with the available structures of homologues characterized by X-ray crystallography. Sequenced conserved outer regions of these proteins were analyzed for their protective capacity in the infant rat model of H. influenzae infection. 

Results: Nine peptides that were protective in the infant rat model were used in a novel vaccine to immunize chinchillas, the most established animal model of otitis media. Chinchillas (40 vaccinated and 41 controls) were infected with NTHi 86-028NP. The vaccinated group cleared infection more quickly than the control group as indicated by significantly decreased positive findings on video-otoscopy (p< 0.0001) and tympanometry (p=0.0002) on day 7, and presence of middle ear fluid obtained by aspiration (p=0.0001) on day 10 post infection.  Similarly, in the mouse model of NTHi pulmonary clearance, the vaccinated group (n=5) reduced infection more rapidly than the control group (n= 5), p=0.008.

Conclusion: These data demonstrate the effectiveness of the Bacterial Vaccine Polypeptide methodology in development of a vaccine against NTHi with protection in relevant preclinical models of both otitis media and pulmonary clearance. The methods are applicable to other bacteria, and this approach to a Bacterial Vaccine Polypeptide against NTHi serves as a paradigm for development of similar vaccines to protect against other bacterial infections.