Tuberculosis vaccine breakthrough is a significant step forward

Researchers have developed a new type of tuberculosis (TB) vaccine and used it on monkeys with simian immunodeficiency virus (SIV). The results suggest it may be possible to develop a TB vaccine that will work for most people with HIV, meaning thousands of lives could be saved each year.

What is the research about?

The University of Pittsburgh has carried out research on macaques monkeys with SIV (the simian equivalent to HIV). The study has been done to explore how effective it is to provide a TB vaccination directly into the bloodstream through a vein. This is called an intravenous (IV) vaccine. Currently, a TB vaccine exists that is injected into the skin but it has limited effectiveness.

The research follows a 2020 study in which monkeys without SIV were given IV TB vaccines and went on to develop immunity against TB.

Why is this research important?

TB is the leading cause of death for people with HIV. But the current TB vaccine is not recommended for people with HIV who are virally unsuppressed. This is because it contains a small dose of the live bacteria that causes TB so it is dangerous to people with compromised immune systems. In addition, the current TB vaccine does not protect most adults and adolescents so it is mostly given to infants and children.

What did they find out?

This study involved 15 macaques without SIV and 19 macaques with SIV.

In the SIV-negative group, seven of the macaques were given an IV TB vaccination. In the SIV-positive group, 12 were given an IV TB vaccination. The non-vaccinated monkeys were observed as control groups.

After three weeks, all the macaques who had been vaccinated were given antibiotics to kill the live bacteria in the vaccine. This was done to test if the vaccine had enough time to encourage the monkeys’ immune systems to protect against TB without the vaccine itself producing TB infection in the monkeys with SIV. The theory was proven to be correct as none of the monkeys with SIV became ill from the vaccine.

Nine out of the 12 monkeys with SIV (75%) who were vaccinated did not develop TB after being exposed to it. The remaining 4 monkeys who developed TB had the most advanced form of SIV.

Among the seven monkeys without SIV, none developed TB.

What does this mean for HIV services?

A new TB vaccine for humans is a long way off, but this is an important development. It means that it may be possible to provide people with HIV with safe and effective protection from TB, regardless of how advanced their HIV is.

The next step will be to test the IV TB vaccine without providing antibiotics after three weeks to see if the vaccine makes monkeys with SIV ill or not. Testing will also happen on a different type of TB vaccine which can ‘self-destruct’ before causing TB in a compromised immune system.

Reacting to the findings, Dr Charles Scanga from the University of Pittsburgh’s Department of Microbiology and Molecular Genetics, said: “Prevention in the form of a realistic TB vaccination strategy is going to be key to saving hundreds of thousands of lives each year. And I'm hopeful that our study is a big step in that direction.”