‘Biobead’-based TB vaccine shows potential in mice

While Bacillus Calmette-Guérin is the only approved tuberculosis vaccine, its variable efficacy, along with the rise of drug-resistant TB, means there is always room for an updated shot. A new candidate, based on “biobeads,” elicited an immune response in mice and could lay the path for a new approach to preventing the disease.

“Biobeads” are natural polyesters that some bacteria form into tiny spheres. In previous work, researchers led by Axel Heiser of AgResearch in New Zealand engineered biobeads, assembled by E. coli bacteria, to present antigens from tuberculosis bacteria called Mycobacterium, according to a statement. They found that these biobeads provoked cell-mediated immune responses in mice, but that they also presented E. coli proteins on their surface.

“From these observations, we developed the hypothesis that these proteins could also function as antigens,” Heiser said in the statement. “If produced in Mycobacteria instead of E. coli, such biobeads should carry mycobacterial antigens on their surface, including many as yet undiscovered antigens which would have the potential to induce protective immunity.”

To create their beads, the team had to modify their approach, since Mycobacteria don’t have the enzymes needed to assemble biobeads. Using new cloning methods, they created a form of Mycobacterium smegmatis—a strain of the bacterium that doesn’t cause TB but that does express the required enzymes. They chose this bacterium to sidestep the risk of the vaccine causing TB infection.

They tested the new vaccine in mice, where they saw an immune response that could potentially protect against TB. The researchers plan to conduct a challenge study to prove protection from the disease. They will also work on more efficient ways to produce and purify the vaccine, according to the statement.

The CDC estimated one-third of the world’s population to be infected with TB, with 10.4 million people worldwide falling sick with the disease in 2015. While questions have arisen over the efficacy of the BCG vaccine in different geographical areas, it is still widely used. A new vaccine would be a boon in the fight against the disease, with strains that do not respond to two of the most powerful antituberculosis drugs.

Some players looking to tamp down on TB include Duke University, which may have landed on a more effective antibiotic for bacterial infections and a team from UC San Francisco and the University of Queensland, which is working on a method to curb the growth of Mycobacteria.