Globally, although the vast majority of people have been vaccinated, more people die from TB than from any other infectious disease. Bacille Calmette-Guerin (BCG) is the only commercially available human tuberculosis vaccine. It is a live attenuated vaccine made from attenuated bovine Mycobacterium tuberculosis suspension. BCG has a history of more than 100 years and is one of the most widely used vaccines in the world, but its efficacy varies greatly.
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Research Results
Given that monkeys are extremely susceptible to Mycobacterium tuberculosis (TB), in a new study, researchers from (NIAID) of the National Institute of Allergy and Infectious Diseases and the University of Pittsburgh School of Medicine found that intravenous TB vaccine can highly protect monkeys from Mycobacterium tuberculosis infection, by studied on monkeys, and compared to the current standard route of delivery, TB vaccine injected directly into the skin provides very little protection.
This finding suggests that simply changing the delivery mode of TB vaccine may significantly enhance its protective ability. The results are published in the journal Nature.
“The effect is very remarkable. We found a 100000-fold reduction in the bacterial burden in the lungs of the monkeys given the TB vaccine intravenously compared to the standard monkeys given the TB vaccine through the skin, and 9 of the 10 monkeys that received the intravenous injection had no inflammation in their lungs. ” said Dr. JoAnne Flynn, a professor of microbiology and molecular genetics at the Vaccine Research Center at the University of Pittsburgh School of Medicine.
The idea for an intravenous TB vaccine came from an early experiment by the paper’s correspondent, Dr. Robert Seder, form the Vaccine Research Center of the National Institute of Allergy and Infectious Diseases. Seder has found that intravenous malaria vaccine is more effective in both animals and humans.
2. Introduction to Experiment
To test whether this vaccine is effective for TB, Flynn and his colleagues tested several delivery routes and doses of the TB vaccine, or BCG. They divided a group of monkeys into six groups: unvaccinated monkeys, monkeys given standard vaccine doses through skin injections, monkeys given larger doses through skin injections, monkeys given vaccines through skin injections and sprays, and monkeys given larger doses at one time through intravenous injections. Six months later, they exposed the monkeys to Mycobacterium tuberculosis and monitored them for signs of infection.
All monkeys who received standard vaccine dose delivery had persistent pulmonary inflammation, and the average amount of Mycobacterium tuberculosis in their lungs was only less than that of unvaccinated monkeys. Monkeys given larger doses of the vaccine through skin injections and monkeys given vaccines through skin injections and sprays provided similar moderate protection against TB. The intravenous vaccine, on the other hand, provided almost complete protection; the monkeys who received the intravenous vaccine had almost no tuberculosis in their lungs, and only one of the monkeys in this group had inflammation of the lungs.
“The reason why intravenous delivery is so effective is that the TB vaccine travels quickly through the bloodstream to the lungs, lymph nodes and spleen and prepares T cells to launch an immune attack before they are killed,” Flynn explained.
Flynn and his team found BCG and activated T cells in the lungs of all monkeys given the vaccine intravenously. In other groups, BCG could not be detected in the lung tissue, and the T cell response was relatively weak. Next, they plan to test whether lower doses of intravenous BCG provide the same level of protection without side effects such as temporary lung inflammation.
But before applying this method to humans, scientists need to know that it is not only safe but also practical. Intravenous vaccination requires more skill and has a higher risk of infection. “We are still a long way from realizing the transformational potential of this research, but we eventually hope to test it in humans,” Flynn said.