Last month, a team of researchers from the Centre for Molecular Medicine at the Jawaharlal Nehru University in New Delhi working on the BCG (Bacillus Calmette–Guérin), a vaccine commonly used to treat cases of tuberculosis have been able to improve the efficacy the treatment by a factor of 50 in mice. This was achieved by giving the mice an anti-leprosy drug clofazimine for a month in combination with BCG. Tuberculosis (mycobacterium tuberculosis) and leprosy (mycobacterium leprae) are caused by the same genus of bacteria known as mycobacterium which causes significant infections especially in mammals.
The team of researchers observed that the bacterial load was 50 time less in groups of mice that were given the combination of the two drugs in comparison with the ones that were given the BCG on its own.
The scientist behind this discovery explain that clofazimine, the anti-leprosy drug enhances the production of long lasting memory cells called the central memory T cells or Tcm, also referred to as T lymphocyte. These cells are responsible for recognising numerous pathogens such as infectious diseases as well as cancers by having memorised their antigens following an initial invasion. Tcm cells then convert into large numbers of effector memory cells or Tem cells, which are directly responsible for eliminating pathogens. The team, led by Professor Gobardhan Das has been able to nearly double the pool of Tcm cells by administering the anti-leprosy drug in mice that were already treated with BCG. Professor Das has said:
“Our study suggests that clofazimine (anti-leprosy drug) treatment enhances the pool of Tcm cells induced by the BCG vaccine, and these cells have the potential to continuously replace Tem cells at the site of infection” adding that “Therefore, clofazimine might function as an effective immune modulator to enhance the efficacy of BCG vaccination in humans. Adults who have already been vaccinated with BCG can be given another dose of BCG along with clofazimine anti-leprosy drug. Since mice were protected for 3-4 months, we can conservatively say that the vaccine protection could last for 40 years in humans,”
The team of scientists have acknowledged that the next logical step would be to carry these tests in primates if further funding was available.
The BCG vaccine has been subjected to numerous efficacy trials over the past decades and results over its protective efficacy remains controversial due to conflicting data . Recent trials in the United Kingdom indicate that BCG has a 60 to 80 percent efficacy against severe forms of tuberculosis in children, particularly meningitis, and its efficacy against pulmonary diseases varies geographically. The BCG does not seem to protect against the disease when it is given to people already infected with mycobacterium tuberculosis and results widely vary with regards to geographical location. Until recently it was not possible to establish whether the protective effect of BCG vaccination against the disease was from its action in preventing the initial acquisition or limiting the progression from infection to a full blown clinical disease.