The tuberculosis (TB) vaccine is far from infallible, but new animal research suggests the problem is not the vaccine but how it is delivered.
When given to monkeys intravenously rather than as an injection, the vaccine was much more effective, researchers from the University of Pittsburgh and the U.S. National Institute of Allergy and Infectious Diseases found.
"The effects are amazing," said researcher JoAnne Flynn, a professor of microbiology and molecular genetics at the Pitt Center for Vaccine Research. "When we compared the lungs of animals given the vaccine intravenously versus the standard route, we saw a 100,000-fold reduction in bacterial burden. Nine out of 10 animals showed no inflammation in their lungs."
Flynn's team tested several ways of giving the vaccine at different doses. The vaccine has been around for 100 years and is one of the most widely used vaccines in the world.
Six months after giving the monkeys the vaccine, the researchers exposed the monkeys to TB and then looked for signs of the lung infection.
All of the animals given the standard human dose had lung inflammation, and the amount of TB bacteria in their lungs was only a little less than in the animals that were not vaccinated, the investigators found.
Those given the intravenous vaccine, however, had virtually no TB bacteria in the lungs, and only one monkey in this group developed lung inflammation.
"The reason the intravenous route is so effective is that the vaccine travels quickly through the bloodstream to the lungs, the lymph nodes and the spleen, and it primes the T-cells before it gets killed," Flynn explained in a university news release.
Before giving the TB vaccine to humans this way, researchers have to prove that it is safe and practical. An intravenous vaccine requires more skill to administer and has a higher risk of infection. And animal research doesn't always pan out in humans.
"We're a long way from realizing the translational potential of this work," Flynn said. "But eventually we do hope to test in humans."
The report was published online Jan. 1 in the journal Nature.
For more on tuberculosis, head to the U.S. Centers for Disease Control and Prevention.