Tuberculosis (TB) is probably triggered by the bacterium Mycobacterium tuberculosis (MTB), which infects the lungs and spreads through the air as a result of coughing. Every year 9 million new cases of TB are reported. A recent study has now identified a protein secreted by the TB bacteria that can be used as a new vaccine candidate. This protein also seems to improve TB diagnosis.
In this study, experts laid hands on a protein named EspC that causes a stronger immune response in people infected with the TB bacterium than any other known molecule. This protein is allegedly secreted by the TB bacterium, but not by the currently available vaccine BCG. Hence, the vaccine may fail to induce an immune response to this protein. Well, the protein can purportedly serve as a diagnostic tool.
“Despite most of the world’s population having had a BCG vaccination, there are still 9 million new cases of TB every year. So we urgently need to develop a more effective vaccine for TB. We’ve shown that EspC, which is secreted by the bacterium, provokes a very strong immune response, and is also highly specific to MTB. This makes it an extremely promising candidate for a new TB vaccine that could stimulate broader and stronger immunity than BCG. Surprisingly, our results also show that this molecule could underpin next-generation diagnostic blood tests that can rapidly detect latent TB infection,” stated senior author Professor Ajit Lalvani, from the National Heart and Lung Institute at Imperial College London.
EspC can supposedly underpin the next-generation of immune cell-based blood tests for TB infection, known as interferon-gamma release assays (IGRAs). It is anticipated to offer increased diagnostic sensitivity without compromising a test’s ability to discriminate between BCG-vaccination and TB infection. During the study, authors examined the way immune system responded to EspC in 45 people with active TB. While 27 participants were diagnosed with latent TB infection, other 27 were seemingly suffering from uninfected BCG-vaccinated controls.
EspC presumably elicited immune responses at least as strongly as other proteins known to be targeted by the immune system in people with active and latent TB infection. Two out of 27 BCG-vaccinated controls apparently demonstrated the specificity of the response. This is probably because the TB vaccine lacks genes that are essential for secreting EspC.
The study is published in Proceedings of the National Academy of Sciences.