Research Project
6643782
DESCRIPTION (provided by applicant): One of the most challenging aspects of new vaccine development for viruses, bacteria and parasites is overcoming problems of antigenic variation. The development of vaccines against pathogens, which cause otitis media are being vigorously pursued by many groups, but is complicated in a significant way due to their antigenic diversity. Our incomplete understanding of the pathogenic mechanisms used by each of the three major bacterial species (nontypeable Haemophlius influenzae (NTHI), Streptococcus pneumoniae and Moraxella catarrhalis), their viral co-pathogens (Influenza, Rhinovirus, Adenovirus etc) and our inadequate understanding of the pediatric immune response during OM has presented multiple unique challenges. NTHI, a major bacterial pathogen of Otitis Media (OM) in children exhibits considerable strain-to-strain variation. The major outer membrane proteins (OMP) appear to be the major target of serum antibody and important targets of vaccine development. Immunological studies consistently show the antibody is directed to immunodominant, linear epitopes in surface loop structures of the OMPs which are strain dependent, undergo antigenic variation and leave the child unprotected against other circulating NTHI escape variants and strains. Detailed studies of two of these OMPs, the P2 and P5 proteins suggest that some regions of these OMPs exhibit less sequence variation. Thus using selected peptides from this result in the production of more broadly bactericidal antibody following immunization. Immunological and biophysical studies examining surface probability, hydrophilicity, flexibility, and antigenicity plots, strongly suggest that additional, more highly conserved regions of the protein, which are poorly immunogenic under natural conditions, could become immunogenic. Antigenic variation promoted through selective genetic instability is obviously a successful immunological strategy employed by many microbial pathogens. Coupling this to selective and focused immunodominance on the protein structure serves to prevent the immune system from recognizing other antigenic structures on the molecule. These "decoying" epitopes of the OMPs structure results in isolate-, strain- or serotype-specific antibody responses. The host immune system appears fixated on these more visible decoying epitopes at the cost of fully recognizing other conserved and protective epitopes within and between surface protein structures. The objective of this proposal is to further test the technology of immune dampening as a strategy to refocus the immune responses away from immunodominant, non-protective or serotype-restricted epitopes in P2 and P5, towards more broadly protective epitopes which (under natural conditions) are relatively less antigenic. The immune dampened and refocused P2 and P5 will be tested singly and in combination for their ability to induce cross strain protective antibody. Immune dampening technology provides for a new approach to circumventing the issues of antigenic variation and could help into the creation of more broadly protective vaccines against a variety of bacterial, viral and parasitic diseases of man and animals.
