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Efforts continue to find effective TB vaccine

Tuberculosis kills nearly 2 million people worldwide every year. One-third of the world’s population is infected with the bacterial disease. Even in the US, where the disease is thought to be under control, tuberculosis infected nearly 9,300 people last year.

Rates of tuberculosis in the US declined steadily in the mid-1900s, and by 1983 scientists at the Centers for Disease Control and Prevention predicted the disease would be eradicated by 2000. But the HIV epidemic in the 1980s contributed to a spike in tuberculosis cases, since people with the virus are more susceptible. And with increased global travel and immigration, the goal of eradication has grown out of reach.

The disease has persisted in part because of the lack of an effective vaccine. Plus, a growing number of cases have become resistant to antibiotics. Researchers at St Louis University (SLU) want to find better ways to prevent and treat the disease as part of an international call to action.

“The slope of cases is declining again, but it’s a wake-up call that it’s going to be hard to eradicate something that’s infected a third of the world,” said Dr Daniel Hoft, director of St Louis University’s division of infectious diseases, allergy and immunology.

One avenue of research involves the delivery method for the vaccine. It is usually administered just under the skin, producing a blister and small scar in most people. Researchers at SLU, funded partially through the Bill and Melinda Gates Foundation, have studied an oral version. They found that combining it with the skin shot seems to produce a better immune response, particularly in the lungs where the germs tend to settle.

A vaccine for TB has been available for nearly 100 years, but it isn’t effective at stopping the spread of the disease. The vaccine is thought to protect against life-threatening TB complications, including meningitis, in childhood. The World Health Organisation recommends all babies in countries with high TB rates (not including the US) get vaccinated as soon as possible after birth.

“It hasn’t made a dent in the overall prevalence of the disease although it has saved many lives in the first five years of life,” Hoft said. “We’ve been trying to understand a lot more about what (the vaccine) does and doesn’t do and how can we develop a better vaccine to lower prevalence.”

The researchers also are recruiting in St Louis for a small trial where volunteers will undergo a blood filtering process to separate white blood cells before and after vaccination. Those cells will then be studied for more clues about how the vaccine works.

Tuberculosis is caused by bacteria that can spread through the air when an infected person coughs or sneezes. The bacteria usually infect the lungs but can also reach the kidneys, spine and brain. In most people, the immune system keeps the bacteria in check without symptoms. If the disease activates, it usually can be treated and cured.

If people don’t have access to treatment, or don’t complete the six- to nine-month drug regimen, the bacteria can become resistant to antibiotics.

About 3,000 people have latent tuberculosis cases in Missouri, and the state records an additional 100 active infections each year. About one-third of the cases come from the St Louis region. Illinois reported 342 active tuberculosis cases last year. Only people with active infections can spread the disease to family members and others in close contact. Internationally, tuberculosis remains a top-10 killer.

“The failure to control TB is a direct consequence of the gross inequities in the distribution of wealth and health care both within and between countries. Control of TB is ultimately a question of justice and human rights,” a World Health Organization position paper says.

On the treatment side, SLU is part of a trial in Africa with 350 people who have drug-resistant TB. Currently the only option for people with drug-resistant tuberculosis is to get daily shots for six months plus take oral drugs for nearly three years. Patient compliance is low, and the side effects can include hearing loss and kidney disease. The cost is up to $500,000 for a three-year regimen compared to $18,000 for a case that responds to typical antibiotics, according to the CDC.

In the trial, one group will get the standard treatment and another will get a new drug given orally to replace the injections. If the treatment is safe and effective, it could become a more practical method for tackling the epidemic. “We really need this not only to make it easier for people but to have a better chance of not having more drug resistance occurring,” Hoft said.

Agencies. Efforts continue to find effective TB vaccine. Daily Times, September 5, 2017.

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