An experimental vaccine provokes an immune response to 72 of the 90 known forms of Streptococcus pneumoniae in lab test animals, according to research published last week in Science Advances. The findings offer hope for creation of a vaccine that more thoroughly prevents diseases such as pneumonia, meningitis, and sepsis.
While previous iterations of the S. pneumoniae vaccine have played a large role in cutting the death rate from the bacteria in half, there remain limitations that have prevented them from being completely effective. One of the main obstacles has been that current vaccines have no mechanism to discern between harmful bacteria and harmless bacteria that is part of the microbiome.
In creating this new vaccine, the authors sought to get around this limitation through use of a two-pronged approach to S. pneumoniae prevention. Colocalization of two classes of complementary antigens allows one antigen to prevent colonization of the most aggressive serotypes and another to restrict virulence transition. This allows harmless bacteria to remain in place, preventing harmful bacteria from colonizing.
This approach also does not require the type of complex covalent chemistry required by some current vaccines. This could enable more sugars to be included as part of the vaccine, providing more complete coverage.
Image: How the new vaccine under development works. The circles represent strains of Streptococcus pneumoniae, the bacteria that causes pneumonia. The left side of the image shows the immune system attacking bacteria before it colonizes the body. The middle section shows forms of S. pneumoniae not covered by current immunizations settling in the body. The right portion shows the new vaccine attacking those bacteria only after they become problematic. Image courtesy of 'Jones et al., Sci. Adv. 2017;3: e1701797.'