A retooled version of the vaccine currently used against tuberculosis
shows superior protection against the pathogen in animal studies, according
to a report by researchers from Germany, England, France, and the Netherlands.
The researchers engineered a vaccine strain of Mycobacterium
bovis that secretes listeriolysin, a protein that pierces the membranes
of phagosomes that harbor tuberculosis bacteria. This allows better T cell–mediated
immunity than is stimulated by the currently available vaccine, BCG, which
offers only little protection to adults and has limited efficacy against newly
emerging isolates of the tuberculosis bacterium. The researchers also deleted
the urease C gene of the bacille Calmette-Guérin strain, to create
the ideal pH environment for listeriolysin. In mouse studies, the new vaccine
strain offered significantly better protection against tuberculosis, not only
against the laboratory strain of the bacterium but also against a drug-resistant
strain that is increasingly spreading across the globe.
Stephenson J. TB Vaccine Boost. JAMA. 2005;294(11):1331. doi:10.1001/jama.294.11.1331-c