Hyderabad: A group of scientists has found a new candidate for tuberculosis (TB) vaccine, which could be more effective than the existing BCG vaccine, the first and only vaccine for the fatal disease.
The efficiency of the BCG vaccine is not 100% which is why there has been a need for a better working vaccine.
In a study published in the Journal of Clinical and Vaccine Immunology, three scientists have identified a new candidate for the development of a more effective TB vaccine.
“Rv1860 (the newly found candidate) was found to stimulate CD8+ T cells, a subset that strongly correlates with the protective immunity in several human and primate studies,” said Vijaya Satchidanandam of the Indian Institute of Science (IISc) and the lead author of the study.
The vaccine uses a dead or weakened pathogen, which is responsible for causing the disease, to stimulate the immune system. This way, a vaccine shot prepares the body to be ready with the defence mechanism by letting the immune system know the threat.
But in the case of TB, a measured protective immune response has not been established yet.
CD8+ T cells, a subset of T cells, are a type of white blood cells. Their role in TB protection has increasingly been recognized. “Rv1860 is a protein secreted by Mycobacterium tuberculosis. It is the deadly pathogen that causes tuberculosis—but not always,” the study says.
An infection of this kind of TB is not considered an active TB disease. In most cases, the bacterium just hangs around in the body in a dormant state and such people are said to have latent TB. The researchers called this group as Group I. The lifetime probability of Group I to get active TB disease is only 10%. They usually lead a normal, healthy life. People with a poor immune response who get infected and proceed to active TB earlier than others were identified as Group II.
The study was based on finding the difference between the immune response of the two groups and the triggers.
For this study, 30 healthy latently infected TB volunteers (Group I) and 20 TB patients with active disease (Group II) were recruited. “Blood samples of both groups were treated with various peptides derived from our candidate-Rv1860. These peptides represent small parts of the protein Rv1860,” IISc said.
In measuring the immune response, researchers found significant production of one or more cytokines, which are chemicals through which immune cells coordinate with each other while fighting a pathogen. It was also found that CD8+ T cells are predominately secreted by these cytokines. The responses were higher in healthy latently infected individuals than those with active disease.
“This study was done on human subjects who were not HIV-positive—the most natural disease setting and hence the positive results are highly encouraging,” said Satchidanandam. The researchers would now validate the results with a larger human cohort.
Apart from scientists at IISc, the study was also co-conducted by Dr. Rajni Rani, a senior staff scientist at the National Institute of Immunology, Dr. Mohan Rao Kotnur, a chest physician at M.S. Ramaiah Memorial Hospital and Dr. Anand Sridharan, a microbiologist at the National Tuberculosis Institute.