A new TB vaccine is at hand – Prof. Helen McShane

A new TB vaccine is at hand – Prof. Helen McShane

Nearly 100 years ago, scientists developed a vaccine against tuberculosis. Today, there are 10 million new cases worldwide and 1.6 million deaths of the disease each year. These cases are becoming more difficult to treat because the virus responsible for the disease can resist antibiotics.

Helen McShane, professor of vaccinology at the University of Oxford, UK, however, believes that several new TB vaccines are being developed and that a growing optimism is emerging. It could save millions of lives, she said, but additional efforts are needed to rebadure the general public that vaccines are safe and effective.

How common is tuberculosis?

"Tuberculosis is the leading cause of death from infectious disease. It overshadows HIV, which can be increasingly treated with antiretrovirals. Africa and Asia are hardest hit, but several countries are making real progress. Tuberculosis rates are generally decreasing thanks to better diagnosis and follow-up, and rapid treatment once the disease has been identified. However, we need to accelerate the pace and intensify TB control measures.

"In Western Europe, the number of people affected is slowly decreasing – there are about 5,000 new cases a year in the UK. In Eastern Europe, drug-resistant TB is a particular problem because it is very difficult to treat once infected.

Is there not already a vaccine against tuberculosis?

"The BCG vaccine is the only licensed TB vaccine to date. It was first developed in 1921 and was offered to 3 billion people worldwide. If the vaccine is given at birth, it offers good protection against what is called a disseminated disease, ie, tuberculosis outside the lungs. However, it confers variable protection against pulmonary tuberculosis (lung disease) ".

Why?

"British data show that the BCG vaccine is 80% effective against pulmonary TB, but a study in India showed that it was not working as well. It appears to be less effective in areas where TB is widespread. There are a number of theories to explain this situation, but the most obvious explanation is that exposure to nontuberculous mycobacteria (NTMs) – insects from the same family as tuberculosis that usually do not cause no disease – harms the effectiveness of the virus. BCG vaccine. The more you live near the equator, the more you are exposed to the MNT and the less effective the BCG is. That's why so many scientists are working on new vaccines.

Why has it proved difficult to develop a new TB vaccine?

"It is difficult to develop a new TB vaccine for three main reasons. First, TB is very smart. If you are infected with TB, the bacteria that causes the disease are hiding in your immune system. This makes it difficult for your immune system to eliminate the infection.

& # 39; Second, we do not know what kind of immune response will protect (the person from TB), and therefore what kind of immune response we need from a new vaccine. On the other hand, if you are developing a new meningococcal vaccine, for example, you can look for a particular type of immune response. If you detect this immune response after vaccination, you would know that the vaccine worked. Therefore, we can not rely on the immune response induced by new vaccines. Therefore, we need to conduct very large and expensive clinical trials (human) on TB vaccines in areas where the disease is prevalent, to determine whether or not a vaccine is preventing people with TB.

Third, the use of animal models in tuberculosis research is also problematic. For many diseases, there is an established animal model that can tell us a lot about the operation of a vaccine or treatment before moving on to human testing. In tuberculosis, we do not know which animal model best predicts the performance of a vaccine in humans. & # 39;

In the face of these challenges, how do scientists develop new vaccines?

"I'm part of the TBVAC 2020 consortium that brings together researchers from TB vaccines from across Europe, as well as scientists from Africa and Southeast Asia.

"What's unique about this group is the strength of its collaborative spirit. Researchers are very open about sharing data and samples, creating a real sense of cohesion. It also allows greater efficiency on the ground, as it reduces duplication and pool expertise. Collaboration accelerates the pace of progress.

"Teams are designing and testing vaccines in animal models, testing vaccines in humans to measure the immune response, and collaborating with vaccine development experts to advance laboratory research to clinical trials. Some are working on the genetic engineering of the BCG vaccine to make it better, others are trying to make a vaccine with a weakened strain of TB, and my own team is taking some of the insect's protein and pbading it on to the system. immune system using a virus. to stimulate an immune response.

Where are we from a new TB vaccine?

"In 2000, no new TB vaccine was tested in clinical trials. Today, there are more than a dozen, many of which come from the European consortium of vaccine developers TBVAC.

"The key result of last year came from a trial of M72 / AS01, a potential TB vaccine developed by GSK. In a trial conducted among African adults already infected with TB but showing no symptoms, the vaccine candidate was 54% effective in preventing people from developing the disease. This is a strong sign that it protects them from TB and is a really important outcome for the field. & # 39;

You mentioned that some strains of TB are resistant to drugs. Could a TB vaccine solve this problem?

"Antimicrobial resistance is a huge global health challenge. A vaccine that prevents TB means that fewer antibiotics are needed. This reduces the development of drug resistance.

"In addition to vaccines that prevent infection, researchers are starting to think about using therapeutic vaccines. A vaccine that could stimulate the human immune response could work with drugs to accelerate healing (by helping antibiotics to work better). & # 39;

Who is the main target of a new TB vaccine?

"There are three: infants, especially in Africa, people living with HIV, adolescents and young people – a particularly important group considering the economic impact that the disease may have and the fact that young adults are responsible for much of the spread of the disease. & # 39;

Why do adolescents and young people spread TB more than other age groups?

"They develop a smear-positive disease – which is the most contagious form. Infants do not develop smear-positive disease and therefore do not transmit TB in the same way. "

In countries where TB is common, are anti-vaccine activists a problem?

"The anti-vaccine lobby is a global problem. It was once presumed that it only affected rich areas where people had forgotten how deadly vaccine-preventable diseases were, but this is no longer the case. I think we need a sustained education program to show how well vaccines are tested, safe and effective. Vaccines save two to three million lives a year – an effective TB vaccine could help increase that number. "

This interview has been modified for its length and clarity.

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