A P5 peptide that is homologous to peptide 10 of OprF from Pseudomonas aeruginosa enhances clearance of nontypeable Haemophilus influenzae from acutely infected rat lung in the absence of detectable peptide-specific antibody

Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen asso ciated with otitis media and the exacerbation of chronic bronchitis. This s tudy reports the vaccine potential of three peptides representing conserved regions of the NTHi P5 outer membrane protein which have been fused to a p romiscuous measles virus F protein T-cell eptitope (MVF). The peptides corr espond to a region in surface loop one (MVF/L1A), the central region of loo p four (MVF/L4), and a C-terminal region homologous to peptide 10 of OprF f rom Pseudomonas aeruginosa (MVF/H3). Immunization of rats with MVF/H3 was t he most efficacious in significantly reducing the number of viable NTHi in both the broncho-alveolar lavage fluid (74%) and lung homogenates (70%), co mpared to control rats. Importantly, despite significantly increased rates of clearance, immunization with MVF/H3 elicited poor antibody responses, su ggesting that cell-mediated rather than humoral responses play an important role in the enhanced clearance of NTHi in this model.