The World Health Organization estimates that the number of children killed by pneumonia fell by half to less than 1 million in the decade that ended in 2015. Part of the credit for that goes to vaccines introduced during that time, which target as many as 23 strains of the Streptococcus pneumoniae bacteria that cause the disease.
Now, scientists led by the University of Buffalo say they have developed a vaccine that may triple that level of protection. In animal tests, the vaccine prompted an immune response to 72 strains of the bug, they revealed in a paper published in the journal Science Advances. A new company called Abcombi Biosciences has been formed to further develop the vaccine.
The key to boosting the vaccine's potency was figuring out how to work with polysaccharides—sugars that are unique to each different strain of S. pneumoniae. Traditional pneumonia vaccines, like Pfizer’s Prevnar 13, create a bond between these sugars and a specific protein. That bond prompts the body to find and destroy each strain before the bacteria can spread through the body.
Instead of creating individual bonds for each strain, the University of Buffalo researchers took a tiny fat bubble called a liposome and added proteins to its surface. When those proteins interact with polysaccharides, it prompts an immune response. Tests in mice and rabbits confirmed immunity to 72 strains, according to a press release.
"The advantage of our approach is that we don't have to apply the more complex covalent chemistry that is required for Prevnar," said the study’s co-lead author, Blaine Pfeifer, Ph.D., associate professor of chemical and biological engineering at the University at Buffalo's School of Engineering and Applied Sciences, in the release. "As a result, we can extend beyond the 13 types of sugars, potentially providing universal coverage against bacteria that cause pneumonia, meningitis, sepsis and other types of pneumococcal disease.”
Although vaccines like Prevnar and Merck’s Pneumovax 23 have greatly reduced the burden of pneumonia around the world, scientists are looking for new technologies to provide better protection against the many strains of the bacteria that cause the disease. Gates Foundation-backed Arsanis is working on monoclonal antibodies to prevent the disease in high-risk hospital patients, for example. And several antibiotics are performing well in late-stage trials, including Paratek Pharmaceuticals’ omadacycline and Nabriva Therapeutics’ lefamulin.
The technology developed at the University of Buffalo is designed to make it simple to add sugars in order to broaden the potential immune response. That could prove important, particularly if less common strains of S. pneumoniae become more prevalent in the future, or new antibiotic-resistant strains emerge.
"We've made tremendous progress fighting the spread of pneumonia, especially among children,” Pfeifer said. “But if we're ever going to rid ourselves of the disease, we need to create smarter and more cost-effective vaccines."