Vaccine breakthrough may protect against deadly form of pneumonia

Researchers at Yeshiva University's Albert Einstein College of Medicine in New York have created an experimental vaccine that protects against a common and especially deadly form of pneumococcal pneumonia by using a synthetic replacement of a toxin-producing gene.

Serotype three is a pneumococcal strain not included in pediatric pneumonia vaccines because even a dead version of the virus can cause inflammation so severe that it may result in a strong case of the disease or even death.

By focusing on replacing a gene in serotype three that codes for pneumolysin, a toxin produced by all pneumococcal strains, with a synthetic version, inflammation response in mice  was reduced without reducing an immune response.

"Our idea was to design a live vaccine that would stimulate the immune system sufficiently to ward off disease but wouldn't lead to the severely damaging inflammatory response that this strain can cause," J. Robert Coleman, the lead author of the study, said. "The novelty of this approach lies in the fact that the gene's expression would be reduced, but not eliminated. Previous approaches to genetic regulation of virulence relied on knocking out genes, which eliminates their expression completely."

While the method has been used to reduce gene expression in viral pathogens, this is the first time that gene customization has been successful in controlling virulence in bacteria. This might lead to a range of pneumococcal vaccines based on weakened strains.

The National Foundation for Infectious Diseases estimates that 175,000 people are hospitalized with pneumococcal pneumonia in the United States each year, with pneumococcus causing 34,500 bloodstream infections and 2,200 cases of meningitis annually. There are 4,800 deaths caused by pneumonia each year, which is higher than any other vaccine-preventable disease in the United States.