When we are exploring the prevalence data on Group B Streptococcus (GBS) infection in humans, the resulting 15% global fatality rate of the pathogen seems to be a small number. When it is translated to numbers it’s huge; around 100,000 deaths can be prevented by just taking a maternal vaccine for GBS. But the sad part is that there is no such vaccine available against GBS infection till now. In this discussion let us understand GBS infections and how vaccines are made and the current vaccines under development and trials.
GBS is a gram-positive opportunistic pathogen present in the gastrointestinal and urogenital tract of humans. It is considered to be one of the main causatives of neonatal deaths. Even the infection appears as late-onset to the child, which may lead to septicemia, meningitis and even death. Antibiotics like Penicillin can kill the pathogen, the lack of proper screening and availability of antibiotics is considered to be a major problem in poor and developing countries. In India, as a part of my research, I had visited many hospitals and inquired about GBS screening. However, none of these hospitals screened for Group B Streptococcus routinely. Lack of proper screening and scarcity of antibiotics in poor and developing countries make the infection more devastating. So this makes the need for a GBS vaccine alarming.
The difference in capsular polysaccharides makes GBS divided into 10 serotypes (Ia, Ib, and II-IX) of which Ia, Ib, II, III, and V were found to be more prevalent. Targeting this capsular polysaccharide was the first approach to develop an effective vaccine against GBS. But in 2014 WHO convention suggests that a vaccine based on capsular polysaccharides was less immunogenic and suggested a conjugate vaccine that will be more effective. To date companies like Novartis and Pfizer are carrying out successful clinical trials for capsular polysaccharide conjugate vaccines. But still, several problems exist while considering a polysaccharide vaccine against this. These include serotype switching, diversity in the serotypes across different geographical locations and immune interference between conjugate vaccines against many other microbes. And also these vaccines were not effective against non-capsular GBS. This made the scientists search for a protein vaccine.
Many protein vaccines are now under preclinical and clinical trials. MinervaX Inc. had recently come with a novel protein candidate for developing the GBS vaccine. It is a protein the only vaccine comprises of a fusion of highly immunogenic and protective protein domains from two surface proteins of GBS (N-terminals of AlphaC and Rib, GBS-NN). These proteins have shown broad distribution among most GBS serotypes (Ia, Ib, II, III, IV, V and VIII), which will be going to develop into a promising vaccine against GBS. After phase, I trials the results are looking highly promising. GlaxoSmithKline had identified a vaccine candidate in GBS pili proteins, which induced the immune response against different GBS serotypes in preclinical studies. Like the above mentioned, several protein vaccines against this are in the developmental stage.
Due to the problems like serotype switching, serotype diversity across the globe makes the development of Group B Streptococcus vaccine lagging, A potential maternal vaccine is the need of the hour and it can cure thousands of lives. Awareness campaigns for effective screening during pregnancy should be carried out across the globe among medical practitioners as well as patients and measures for active research in developing GBS vaccine can help us to see more smiling faces.
Dr. Noble K Kurian, presently working as a post-doctoral fellow at Molecular and Cellular Biology Laboratory, National Institute for Research in Reproductive Health (ICMR), Mumbai under the mentorship of Dr. Deepak Modi. His current research interests include exploring the host-pathogen interactions during pregnancy, with a focus on GBS infection and preterm birth. He had a doctoral degree in bacterial melanin research from Cochin University of Science and Technology, Kochi.