Streptococcus pneumoniae is the leading cause of bacterial pneumonia, one of the biggest killers of children under the age of 5 worldwide. The current first line of treatment for pneumococcal pneumonia and bacteraemia is beta-lactam antibiotics, which is contributing to increased antibiotic resistance. In the pre-antibiotic era serum therapy was successfully used for the treatment of pneumococcal infections. This used antibody rich serum raised in horses to treat patients with pneumococcal pneumonia and bacteraemia, clearing the infection. We propose to use the same approach to develop an antibiotic independent treatment using antibodies that target the pneumococcus.
Methods: MF1 outbred mice were infected intranasally with S.pneumoniae. Antibodies against the capsule and a panel of pneumococcal proteins were administered intraperitoneally 3-24h post infection. Disease progression was monitored using a clinical scoring system. Survival and bacterial load in the organs and blood were also monitored.
Results: Early administration of anti-capsular antibodies prevented disease progression at 3, 6 and 12 hours post infection. At 24 hours once bacteria are present within all organs clearance by anti-capsular antibodies was not observed. Antibodies against the chosen protein targets were not effective at clearing infection.
Conclusion: Early administration of anti-capsular antibodies prevented disease progression. We believe this approach could eventually be used in a clinical setting on patients showing symptoms of pneumonia and sepsis. For protein antibodies more work needs to be done to evaluate a larger panel of antibodies and what the protective epitopes are.