New Vaccine Puts Up Stronger Fight Against Both Tuberculosis And Leprosy
By C. Rajan, contributing writer
Researchers at the University of California Los Angeles have prepared a new and improved variant of an existing vaccine, which is found to offer stronger protection against the two major infectious diseases, tuberculosis (TB) and leprosy. The study has been published in the journal Infection and Immunity.
The current vaccine used for these conditions is the Bacille Calmette-Guerin vaccine (BCG). However, BCG provides only partial protection against both TB and leprosy, so a more potent vaccine is needed to combat both diseases, according to the researchers who proceeded to develop this more effective vaccine.
The researchers have found that a recombinant variant of BCG, rBCG30, over-expresses Antigen 85B, a highly abundant protein which is also expressed by the tuberculosis bacterium. This recombinant variant is superior to BCG in protecting against tuberculosis in animal models, and also offers cross protection against leprosy. Moreover, it was found that boosting rBCG30 with the Antigen 85B protein provides considerably stronger protection against leprosy.
"This is the first study demonstrating that an improved vaccine against tuberculosis also offers cross-protection against Mycobacterium leprae, the causative agent of leprosy," said Dr. Marcus A. Horwitz, professor of medicine and microbiology, immunology and molecular genetics, and the study's senior author. "That means that this vaccine has promise for better protecting against both major diseases at the same time. It is also the first study demonstrating that boosting a recombinant BCG vaccine further improves cross-protection against leprosy," he added.
Tuberculosis is a highly contagious and potentially fatal lung disease, which is caused by the microbe, Mycobacterium tuberculosis. According to the WHO, TB is the second greatest killer worldwide due to a single infectious agent, next only to HIV/AIDS. In 2012, there were 8.6 million TB cases diagnosed and about 1.3 million deaths due to TB.
Leprosy is one of the oldest known contagious diseases which has affected people worldwide. It is a chronic, mutilating disease caused by the microbe, Mycobacterium leprae. According to the WHO, globally, there are more than 230,000 new cases of leprosy per year. Most cases of leprosy occur in countries where tuberculosis is endemic, and these two infectious diseases are often found side-by-side. Hence, a single vaccine that can protect effectively against both diseases would benefit developing countries where these diseases are most prevalent.
This most recent study was conducted in an animal model of leprosy. However, a Phase 1 human trial for rBCG30 has already proven that it is safe and significantly more effective than BCG, and it is the only candidate replacement vaccine for BCG tested thus far to satisfy both of these key clinical criteria.
According to the researchers, the next step will be to test the efficacy of the rBCG30 vaccine in humans against TB. If it succeeds, then the researchers would test its effectiveness in humans against leprosy.
In another recent and related study at UCLA, researchers reported that they have identified a protein which prevents infected patients from developing the active form of tuberculosis. The study, conducted in partnership with researchers from Harvard University School of Public Health and the University of Michigan School of Medicine, was published in the journal Science Translational Medicine.
The protein, interleukin-32, was discovered to play a key role in protecting people infected with Mycobacterium tuberculosis against developing the active TB disease condition and it acts as a biomarker of adequate host defense against TB. This discovery could help doctors identify those who are at the greatest risk for the disease, and it could pave the way for new treatment strategies for tuberculosis.