Efficacy of the 26-Kilodalton Outer Membrane Protein and Two P5 Fimbrin-Derived Immunogens To Induce Clearance of Nontypeable Haemophilus influenzae from the Rat Middle Ear and Lungs as Well as from the Chinchilla Middle Ear and Nasopharynx

Abstract

The rat middle ear and lung clearance model has been used to show that the nontypeable Haemophilus influenzae 26-kDa outer membrane protein OMP26 is highly efficacious as a mucosal immunogen, inducing significantly enhanced clearance in immunized rats upon direct challenge of these two anatomic sites. Similarly, the chinchilla model of middle ear and nasopharyngeal clearance has been used to show that two P5 fimbrin adhesin-derived immunogens, LB1 and lipoprotein D (LPD)-LB1(f) 2,1,3 , are highly efficacious as parenteral immunogens. Both induced significantly augmented clearance of nontypeable H. influenzae upon challenge of these sites. Here, these three nontypeable H. influenzae immunogens in addition to six bovine serum albumin and keyhole limpet hemocyanin conjugates of the synthetic peptide LB1(f) were assayed for relative efficacy in the reciprocal rodent model system. OMP26 was assayed in the chinchilla host by a parenteral immunization route, with clearance of the middle ear and nasopharynx used as outcome measures. Both LB1 and LPD-LB1(f) 2,1,3 were assayed in the rat host with a mucosal immunization route and clearance of nontypeable H. influenzae from the lungs and middle ears as outcome measures. Both of the immunogens were found to induce a high-titered and specific immune responses in the heterologous host system. Moreover, each was found to be highly efficacious in the reciprocal host system, providing strong support for the continued development and inclusion of both OMP26 and P5 fimbrin-derived peptides as candidate vaccine antigens directed at otitis media caused by nontypeable H. influenzae.Developing an effective immunogen and selecting an appropriate adjuvant and dosing regimen for a vaccine to prevent otitis media is an important endeavor, particularly given the rapid increase in antibiotic-resistant strains of the bacteria responsible (2, 8) and the increasing costs of treatment (9,11,18,28). Several outer membrane proteins of nontypeable Haemophilus influenzae, its lipooligosaccharide, and synthetic peptides and recombinant proteins derived from nontypeable H. influenzae outer membrane proteins and detoxified lipooligosaccharide conjugates have all been investigated as possible immunogens against bacterial otitis media in both the rat and chinchilla models (1, 3, 5-7, 10, 17, 19, 20, 22-24, 26, 29).The P5 fimbrin is a protein with four surface-exposed loops, some of which appear to be quite heterogeneous (31), and has a role in adherence (4, 29). Studies in the rat and chinchilla models have found that this antigen is protective (4, 32), particularly when the vaccine is based on loop 3, which can be divided into three groups (3). Three peptides have been designed for this region (LB1 1 , LB1 2 , and LB1 3 ). This antigen protects against infection via an antibody-mediated mechanism, since both active immunization and passive transfer of anti-LB1 serum significantly reduced the severity and incidence of otitis media in chinchillas (3,22). Immunization with these peptides requires conjugat...

Lipooligosaccharides Containing Phosphorylcholine Delay Pulmonary Clearance of NontypeableHaemophilus influenzae

“…NTHi elicits a robust antibody response directed against a number of different surface moieties, and a substantial number of studies indicate that at least a subset of these antibodies may confer protection and/or bacterial clearance (1,4,8,19,21,29,33,35,36,38,66). Additional data indicate that cell-mediated immunity may also be important in the clearance or containment of NTHi infection in COPD patients (20).…”

Epitope-specific immune recognition of the nontypeableHaemophilus influenzaeouter membrane protein 26

“…Adult chinchillas (Chinchilla lanigera) were also included in this study and were examined using otoscopy or tympanometry prior to inclusion to confirm the absence of clinically recognizable signs of middle ear infection. Pre-immune serum samples, collected by cardiac puncture, were tested to determine the presence of pre-existing antibodies to NTHi-OMP 18 and only sero-negative animals were used in the study. All chinchilla experiments were conducted at Nationwide Children's Hospital Research Institute, Columbus, Ohio.…”

“…Previous investigations have identified the efficacy of OMP26 as a potential vaccine antigen. [16][17][18] The current study examined the immunological recognition of T-and B-cell epitopes within truncated OMP26 to further characterize this vaccine candidate.…”

Antibodies Specific for the High-Molecular-Weight Adhesion Proteins of NontypeableHaemophilus influenzaeAre Opsonophagocytic for both Homologous and Heterologous Strains

“…Haemophilus proteins P2 and P6 have each been demonstrated to be specific targets of human bactericidal antibodies (42,43), and immunization of animals with the P6 protein has been demonstrated to modify the course of experimental disease (22). Immunization of animals with the P5-fimbrin adhesion protein, another leading vaccine candidate, or with peptides derived from the protein has also been demonstrated to modify the course of experimental infection in chinchillas and rats (4,5,37). Other proteins demonstrating protection against nontypeable Haemophilus disease following immunization in various experimental systems include recombinant HtrA (40), transferrin receptor (62), OMP26 (24,37), and lipoprotein D (1,2,49).…”

“…Immunization of animals with the P5-fimbrin adhesion protein, another leading vaccine candidate, or with peptides derived from the protein has also been demonstrated to modify the course of experimental infection in chinchillas and rats (4,5,37). Other proteins demonstrating protection against nontypeable Haemophilus disease following immunization in various experimental systems include recombinant HtrA (40), transferrin receptor (62), OMP26 (24,37), and lipoprotein D (1,2,49). It is notable that a recent clinical trial reported that immunization of children with a protein D-pneumococcal polysaccharide conjugate vaccine was partially protective against both pneumococcal and Haemophilus otitis media (49).…”