Evaluation of mixtures of purified Haemophilus influenzae outer membrane proteins in protection against challenge with nontypeable H. influenzae in the chinchilla otitis media model

Abstract

Nontypeable Haemophilus influenzae (NTHi) is one of the leading causative agents of bacterial otitis media, and no vaccine has been shown to be effective against it. Three outer membrane lipoproteins of NTHi have been investigated extensively and are leading candidates for inclusion in a vaccine against this organism. Hi-PAL (P6), recombinant PCP (rPCP), and e (P4) proteins are antigenically conserved among NTHi strains and elicit bactericidal and protective antibodies. A genetic fusion of the rPCP and Hi-PAL proteins has also been reported. Mixtures of these proteins were used for active immunization experiments in the chinchilla model of otitis media. Chinchillas were immunized either with a mixture of all three lipoproteins or with the mixture of rPCP-PAL hybrid plus e protein. When these animals were challenged with a NTHi strain injected directly into the middle ears, no protection from infection or disease, as measured by otoscopy, was observed in either group. However, effusion and inflammation measured by tympanometry were significantly reduced in animals immunized with the three lipoproteins. Animals that had been immunized with either whole NTHi cells or total outer membranes and then challenged with the homologous strain were significantly protected from both infection and disease, as determined by tympanometry and otoscopy. Unlike other animal antisera, chinchilla antisera against the purified proteins had no bactericidal activity against NTHi but did fix complement on the cell surface. Thus, the chinchilla immune responses to mixtures of these lipoproteins differ from the immune responses observed in other animal species. Further evaluation of these proteins for their vaccine potential remains to be done.

Identification and characterization of an immunogenic outer membrane protein of Campylobacter jejuni

“…1A). In order to analyze whether expression of Omp18 in these plasmids was promoted by the vector, the ⍀-Spc fragment, which contains a strong transcription stop signal (7), was inserted between the p lac promoter of the vector and the cloned insert. No difference in the expression of Omp18 was observed in E. coli strains harboring pIVB11 or pIVB12 or the pIVB11:⍀-Spc or pIVB12:⍀-Spc derivatives, respectively, indicating that the gene encoding Omp18 was expressed in E. coli from an endogenous C. jejuni promoter sequence on the cloned fragment.…”

“…Related proteins have been described in a wide variety of bacterial species (6,8,14,17,24,35,38), in which they generally play an important role in the host immune response. In addition, PAL P6 of H. influenzae is suggested to be an important antigen for the induction of protective immunity (7,20). The amino acid sequence of Omp18 shows a consensus sequence for a precursor signal sequence and a cysteine residue at position 19 which is known to be the cleavage site for signal sequence peptidase II (31).…”

Moraxella catarrhalis‐induced purulent otitis media in the rat middle earL

“…Whole formalin-fixed M. caturrkulis for subcutaneous immunization were prepared according to a modified version of the method described by Green and co-workers (9). In brief, strain 12075 was grown for 4 h in BHI to an O D at 490 nm of 0.5.…”

Detoxified lipooligosaccharide from nontypeable Haemophilus influenzae conjugated to proteins confers protection against otitis media in chinchillas

“…This study showed significant differences in the clinical signs of OM between the control and conjugate-immunized groups. Other studies with outer membrane proteins (23) or P6 (13) as immunogens showed no differences between vaccinated animals and controls. Reduction of severity may be due to the neutralization effect of anti-LOS antibodies (IgG) elicited by the dLOS-protein conjugates in the ME cavity since ME inflammation may be induced by endotoxin (LOS) and/or peptidoglycan remaining in the ME after viable bacteria have been eliminated (12,29,42).…”