New TB vaccine shows potential to combat TB meningitis

A team of Johns Hopkins researchers recently developed a vaccine that prevents the virulent TB bacterium from crossing the blood-brain barrier, showing promise to combat TB meningitis.

TB brain infections, even when recognized early, can be fatal because although certain strains of TB can cross the blood-brain barrier, many medicines cannot. If the new vaccine proves to be effective in human clinical trials, it provides hope to combat this often fatal disease.

"Once TB infects the brain, our treatment options have modest effect at best, so preventing brain infection in the first place is the only fool-proof way to avert neurologic damage and death," Lead Investigator Sanjay Jain, M.D., said. "Unfortunately, our sole preventive weapon, the traditional BCG vaccine, has a spotty track record in terms of efficacy."

The BCG vaccine has other shortcomings as well. The vaccine contains live bacteria, so patients with compromised immune systems, such as HIV-positive patients, cannot use it. The new vaccine, however, does not use live bacteria and offers hope to this demographic, as one-third of all HIV-positive people have TB infections.

In trials of the new vaccine, researchers used guinea pigs as subjects; the details of the federally-funded study can be found in the June 11 edition of the PLOS ONE journal. Researchers found that lethal strains of TB have a protein called PknD, which helps the infection cross the blood-brain barrier. The vaccine was created to halt this process.

In trials, the researchers found the vaccine to be effective at minimizing the bacteria's ability to pass into the brain. Guinea pigs given the new vaccine had more bacteria present in the lungs than guinea pigs treated with the current vaccine, but infections in the brain plummeted.

"What this tells us is that even in the presence of full-blown lung infection, the new vaccine somehow blunted TB's ability to infect and damage the brain," Investigator Ciaran Skerry, Ph.D., said.

The vaccine must still be tested on humans before approved for use, but if it is approved the vaccine will alter the way in which TB is fought today.