Delivering tuberculosis (TB) vaccine intravenously (IV) dramatically improves potency, a new study in Nature shows.
The study tested several routes and doses of the only commercially available human TB vaccine, Bacille Calmette-Guérin (BCG) in highly susceptible rhesus macaques,.
A colony of macaques was separated into six groups: unvaccinated, standard human injection, stronger dose but same injection route, mist, injection plus mist, and finally, the stronger dose of BCG delivered as a single shot directly into the vein.
Six months after BCG vaccination, the macaques were challenged with virulent Mycobacterium tuberculosis. Notably, nine out of ten macaques that received intravenous BCG vaccination were highly protected, with six macaques showing no detectable levels of infection.
The data demonstrating that IV BCG immunisation results in markedly increased antigen-responsive T cells, including T cells systemically and throughout the lung parenchyma, and unprecedented protection against Mycobacterium tuberculosis challenge represent a major step forward, the researchers say.
"The effects are amazing," said senior author Dr JoAnne Flynn. "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.”
Next, the researchers plan to test whether lower doses of intravenous BCG could offer the same level of protection.