Pneumolysin, the pore-forming toxin produced by Streptococcus pneumoniae, may have an application as an immunogenic carrier protein in future pneumococcal conjugate vaccines. Most of the 90 S. pneumoniae serotypes identified produce pneumolysin; therefore, this protein may confer non-serotype-specific protection against pneumococcal infections such as pneumonia, meningitis, and otitis media. However, as pneumolysin is highly toxic, a nontoxic form of pneumolysin would be a more desirable starting point in terms of vaccine production. Previous pneumolysin mutants have reduced activity but retain residual toxicity. We have found a single amino acid deletion that blocks pore formation, resulting in a form of pneumolysin that is unable to form large oligomeric ring structures. This mutant is nontoxic at concentrations greater than 1,000 times that of the native toxin. We have demonstrated that this mutant is as immunogenic as native pneumolysin without the associated effects such as production of the inflammatory mediators interleukin-6 and cytokine-induced neutrophil chemoattractant KC, damage to lung integrity, and hypothermia in mice. Vaccination with this mutant protects mice from challenge with S. pneumoniae. Incorporation of this mutant pneumolysin into current pneumococcal vaccines may increase their efficacy.

Moraxella catarrhalis is a common cause of lower respiratory tract infection in adults with chronic obstructive pulmonary disease (COPD).Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States and in the world (1, 29, 39). The course of COPD is characterized by intermittent exacerbations of the disease, and many of these exacerbations are caused by bacterial infection (35). Bacterial infection of the respiratory tract is associated with substantial morbidity and mortality in adults with COPD, and strategies to prevent these infections would have an important impact on the course of the disease (27). One such strategy is the development of vaccines. Elucidating human immune responses to bacteria which cause exacerbations of COPD will serve as a guide for the development of vaccines to prevent bacterial infection in patients with COPD.Several lines of evidence implicate Moraxella catarrhalis as an important cause of exacerbations of COPD. (i) A subset of patients with exacerbations have sputum smears which show a predominance of gram-negative diplococci on Gram staining and yield nearly pure cultures of M. catarrhalis (6,22,30). (ii) Pure cultures of M. catarrhalis are recovered from samples collected from patients experiencing exacerbations by using methods which reliably reflect lower airway bacteriology (13,14,23,31,38,40) Outer membrane protein (OMP) CD is a 45-kDa protein which has been the subject of investigation as a potential vaccine antigen for M. catarrhalis. OMP CD has several characteristics to suggest that it will be an effective vaccine. It is present in all strains of M. catarrhalis and has epitopes that are present on the surface of the intact bacterium (24, 32). The presence of surface-exposed epitopes suggests that potentially protective antibodies would be able to bind OMP CD on the whole bacterial cell. OMP CD is highly conserved among strains of M. catarrhalis (18,25). Three lines of evidence suggest that immunization with OMP CD will induce protective antibodies. First, immunization of experimental animals with OMP CD induces bactericidal antibodies (41). Second, both mucosal and systemic immunization with recombinant OMP CD enhance pulmonary clearance of M. catarrhalis in a mouse pulmonary challenge model (26). Finally, the level of serum antibodies to OMP CD in infants and children is inversely correlated with the severity of otitis media with effusion, suggesting that antibodies to OMP CD play a protective role (15).In a previous study levels of immunoglobulin to OMP CD were measured in serum and sputum samples from three groups, including 10 healthy adults, 10 adults with COPD who were free of colonization by M. catarrhalis, and 10 adults with COPD who experienced exacerbations due to M. catarrhalis (24). The concentration of serum immunoglobulin G (IgG) to OMP CD was significantly higher in the COPD group with exacerbations than in the COPD group without colonization and the healthy controls. A clear-cut rise in levels of immuno-