Old TB vaccine can improve immune response to TB in HIV patients

Keith Alcorn
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This article is more than 21 years old.

An old form of vaccine against tuberculosis has shown promise in people with HIV, researchers from Dartmouth Medical School and the National Public Health Institute of Finland report in the November 7th issue of the journal AIDS.

The vaccine is based on inactivated mycobacteria, a method of vaccination demonstrated to prevent tuberculosis in humans and animals prior to the introduction of the live TB vaccine known as BCG in the 1950s.

However, BCG is not effective in preventing the development of tuberculosis in people with HIV, so researchers decided to test the old method of vaccination to see if it could protect HIV-positive people.

Glossary

mycobacteria

Family of bacteria that includes the causes of tuberculosis and MAI.

boosting agent

Booster drugs are used to ‘boost’ the effects of protease inhibitors and some other antiretrovirals. Adding a small dose of a booster drug to an antiretroviral makes the liver break down the primary drug more slowly, which means that it stays in the body for longer times or at higher levels. Without the boosting agent, the prescribed dose of the primary drug would be ineffective.

randomised controlled trial (RCT)

The most reliable type of clinical trial. In a trial comparing drug A with drug B, patients are split into two groups, with one group receiving drug A and the other drug B. After a number of weeks or months, the outcomes of each group are compared.

efficacy

How well something works (in a research study). See also ‘effectiveness’.

immunisation

Immunisation is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body’s own immune system to protect the person against subsequent infection or disease.

 

The study was done in Finland where BCG vaccine is routinely administered at birth. A cohort of 39 HIV patients, mainly men, were divided into two groups to receive a five-dose course of the killed vaccine, Mycobacterium vaccae, or a control vaccine for Hepatitis B. Parallel studies were also conducted on HIV- negative subjects.

"The multiple-dose course of the inactivated vaccine boosted immunity against TB both in those with HIV and those without TB," said Dr C. Fordham von Reyn of Dartmouth Medical School in the USA. "The vaccine was also safe and did not adversely affect the patients' underlying HIV infection."

The researchers looked for mycobacteria-specific cellular immune responses in patients with CD4 cell counts above 200 cells/mm3 (median CD4 cell count 12 months after immunisation was 682 cells/mm3 in the M.vaccae recipients).

The study served as the basis for a large-scale trial Dartmouth researchers have been conducting since 2001 in Dar es Salaam, Tanzania with Muhimbili Hospital Medical Center. The five-year $3 million NIH funded study is the only efficacy trial of a new TB vaccine currently under way in the world. The Tanzania trial will enroll more than 2000 HIV-infected patients to determine if the boosted immunity detected in the Finnish study actually reduces the risk of tuberculosis among HIV infected people in Tanzania at high risk of the disease.

Further information on this website

Resources on TB at this website

Reference

Vuola JM et al. Immunogenicity of an inactivated mycobacterial vaccine for the prevention of HIV-associated tuberculosis: a randomized controlled trial. AIDS 17: 2351-2355, 2003.

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