Current Progress with Moraxella Catarrhalis Antigens As Vaccine Candidates

The success of the immunization programs against Haemophilus influenzae type b and, more recently, Streptococcus pneumoniae in developed and some developing countries has demonstrated that invasive disease caused by these bacteria can be very effectively controlled by vaccination. There is also evidence that pneumococcal vaccines can reduce the incidence of acute otitis media in children. More complete control of this disease would be achieved if infections caused by Moraxella catarrhalis and nontypeable H. influenzae, the other common agents of otitis media in children and of a number of respiratory-associated infections in both children and adults, could also be controlled. Since these bacteria do not possess capsules and are not known to secrete exotoxins, the search for vaccine candidates has focused on the conserved epitopes exposed on the bacterial outer membrane. In this article, we review the contribution of M. catarrhalis to disease and recent advances in the development and testing of various vaccine candidates against this bacterium, including those still in the development stage and those approaching clinical trials. Recommendations are proposed for approaches needed for the standardization of assays and use of appropriate animal models for quality-control testing of these vaccine candidates. Regulatory issues surrounding vaccines of this type are also discussed.