Tuberculosis remains a major global health threat. One method of reducing the incidence of the disease is to vaccinate the person with the so called BCG vaccine.
Although more than 3 billion doses of the BCG vaccine have been administered to fight tuberculosis, the ability of the BCG vaccine to protect adults is very limited. This has led us to ponder over the effectiveness of the vaccine in preventing the disease.
A new strategy to enhance the immunogenicity of BCG has been suggested by researchers. In addition they have described a novel vaccine strain with high efficacy against tuberculosis.
The researchers have engineered a BCG strain that secretes a protein called listeriolysin, which punches holes in the membranes of phagosomes where M. tuberculosis is located, allowing better T cell-mediated immunity.
The new form of the vaccine is active at a pH of 5.8, and thereby eliminating the need for utilizing the urease C gene of BCG that normally plays a role in pH neutralization of the phagosome. The lack of urease C allows phagosomal acidification and provides an ideal pH environment for listeriolysin.
The new BCG vaccine strain has been found to protect mice against tuberculosis significantly better than the parental BCG. Superior protection is not only induced against the laboratory strain of M. tuberculosis but also against a clinical isolate of the Beijing/W family, a strain of tuberculosis that is spreading all over the world, is drug-resistant, and is responsible for the most threatening disease outbreaks.