Potential vaccine against deadly bacterium found
doi:10.1038/nindia.2020.124 Published online 18 August 2020
An international research team has discovered a potential vaccine candidate that can neutralise infections caused by Streptococcus pyogenes1. This bacterium, classified into 220 serotypes based on specific cell-surface molecules, causes sore throat, skin disease, rheumatic fever, rheumatic heart disease and kidney infections.
The vaccine candidate protected mice against the bacterium, the researchers found. They say that it can act against several bacterial serotypes found in various geographical locations.
Scientists, including researchers from the Jawaharlal Nehru University in New Delhi and the Banaras Hindu University in Varanasi, used reverse vaccinology, a method that is used to scan gene sequences to find potential new vaccines. Using this method, they scanned the S. pyogenes genome and identified 52 genes with roles in bacterial adhesion and invasion.
These genes, found in bacterial serotypes prevalent in India, were then used to produce serine repeat antigen proteins, bacterial toxins known to activate a host’s immune responses.
The researchers used the bacterial toxins to produce antisera containing antibodies that can kill the bacteria by preventing their adhesion and invasion. They eventually identified an antiserum called SPy_2191, which blocked both bacterial adhesion and invasion.
SPy_2191 protected mice against five prevalent bacterial serotypes found in India, Israel, the UK and the US. This antiserum helped the mice produce enough antibodies that killed and cleared the bacteria from the lungs, liver, spleen and skin, suggesting its potential as a vaccine.
1. Sanduja, P. et al. Cross-serotype protection against group A Streptococcal infections induced by immunization with SPy_2191. Nat. Comm. (2020) doi:10.1038/s41467-020-17299-x