'Trojan Horse' vaccines for malaria, TB and AIDS

By Mike Nagle

- Last updated on GMT

Related tags: Immune system

More effective and easier to administer 'Trojan horse' vaccines
could provide protection for the millions of people at risk from
malaria, TB and AIDS, thanks to a breakthrough from a global
research team.

The scientists, led by Prof Adrian Hill from the University of Oxford, have developed so called 'Trojan horse' vaccines that use virus DNA to get into a cell. However, the virus is genetically modified so that, once inside a cell, instead of reproducing and spreading, it produces both disease-killing antigens and other molecules designed to boost the immune system.

There are hundreds of millions of new cases of Malaria, TB and AIDS every year, resulting in nearly 8m deaths, according to the World Health Organisation (WHO).

These diseases are most prevalent in the developing world, yet many vaccines need to be kept frozen during transportation and storage. The WHO estimates that nearly half of all global vaccines are wasted, partly because they are stored improperly and therefore it is often very difficult for vaccines to be readily available to sufferers.

With his new vaccine in development, Prof Hill realised that, for it to be truly useful, he needed to make the vaccines easier to transport and store. He approached Cambridge Biostability to help solve the problem.

Howard Smith, technical and commercial manager at Cambridge Biostability told DrugResearcher.com: "The virus in the vaccine is extremely fragile; it normally has to be stored at -80°C."

"We can take an otherwise labile vaccine and embed it in a solid glass formulation. We remove the water and the vaccine becomes thicker and then solid. It is then as stable as the glass itself, which is totally inert,"​ he said, describing the first step in the process.

"We can control the density of the glass and create a vaccine in powder form."

The next step is to add a non-reactive, non-water liquid to turn the powder into a readily injectable form. The vaccines are then so stable, they can be preloaded into syringes or other injection devices. Indeed, Cambridge Biostability has data showing the vaccines are stable at 37°C for up to three years (and for 14 months at 55°C).

Smith added: "If something is going to degrade, it'll do it quite quickly and so if it has kept going that long, it's not going anywhere."

The new technology isn't limited by what is in the vaccine and Cambridge Biostability are also working with Panacea Biotec, India's second largest vaccine producer, to develop vaccines against diphtheria, tetanus, whooping cough, hepatitis B and haemophilus influenza B (a major cause of bacterial meningitis and pneumonia in children).

Most vaccines cause the immune system to produce antibodies to fight off infection. However, many pathogens live inside cells where they avoid being attacked because the antibodies can't get to them.

Not only can this new type of virus-vectored vaccine get inside the cell, it also contains genes that produce molecules designed to stimulate, or adjuvant, the body's natural immune system to elicit a stronger, more prolonged response.

"The virus-vectored vaccine is priming the immune system to recognise a part of the virus so that if you later get the disease, the immune system kicks in and stops the virus from becoming established,"​ said Smith.

The research is part of a global collaboration that also includes scientists from the University of Sheffield, UK and the US-based Wistar Institute. The Bill & Melinda Gates Foundation has given $10m (€7.7m) towards the research and the group's first aim is to proceed to Phase I trials of the most promising malaria candidate vaccine.

Related topics: Preclinical Research

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