Susanna Dunachie: Tropical Immunology
Melioidosis is a neglected tropical disease, and a major infectious killer in South East Asia. Melioidosis particularly affects people with diabetes. Dr Dunachie studies how the patients' own immune system fight the disease, with the aim of designing a vaccine that could stop people getting sick and dying.
This is a podcast from the Nuffield Department of Medicine. Today Dr Susanna Dunachie tells us about her research in tropical immunology.
Q: Can you tell us a little bit about the diseases that you study?
SD: I have been based in Bangkok, Thailand for four years. There were a number of diseases I studied: melioidosis, scrub typhus and malaria. The main disease I studied was melioidosis. This is a disease many people have not heard of, caused by a gram negative bacterium: Burkholderia pseudomallei, that lives in the environment and causes a lot of disease in Thailand, South East Asia and Northern Australia.
The disease it causes is a sepsis illness, where people come to hospital and they might have bad pneumonia, sepsis, blood poisoning and perhaps renal dysfunction or abscesses. The disease can cause anything. Unfortunately, it has a very high mortality rate: in the hospital I worked at in North East Thailand, the mortality of patients coming to hospital with melioidosis was around 40% and this was when they got the correct antibiotics and ITU (Intesive Therapy Unit) care.
Q: Are some people more likely to get this disease than others?
SD: The main people who contract this disease have diabetes. Two thirds of the people in my study had diabetes (type 2 diabetes) and other people have some problem with their immune system, such as renal disease, chronic lung disease, drinking too much alcohol or older age.
Q: What can we do to help these patients?
SD: I am an immunologist, as well as a physician, and my work is trying to find a vaccine for melioidosis and other bugs that hide inside cells. I have set up a longitudinal study of patients with melioidosis and tracked these people over a year, trying to see how people fight the disease naturally. I take people's blood and look at the white blood cells and try to see which bits of the bacteria - which antigens - the white blood cells are making immune response to: I try to understand the pathways involved to get protection. Once we understand, that it can help us design a vaccine which we would then use to target at-risk people such as diabetics in the region.
Q: What are the most important lines of research that have emerged in the last 5-10 years?
SD: For melioidosis, a lot of research has been done at the Mahidol Oxford Tropical Medicine Research Unit where I was based. I have Thai colleagues who are working on therapies. There have been some really outstanding drug trials, for example comparing two antibiotics head-to-head, comparing follow-on tablet antibiotic regimens, and a lot of research into diagnostics as well because melioidosis is difficult to diagnose. Other research by colleagues is trying to understand susceptibility: why some people get it and others don’t.
Q: Why does this line of work matter and why should we fund it?
SD: Melioidosis is a neglected tropical disease. It is a major killer in North East Thailand: it is one of the biggest infectious killers, up there with HIV and TB. It is very, very under-recognised. The hospital I was working in had four hundred cases a year and it is likely that many other hospitals in the region have these numbers as well, although it is not always accurately diagnosed. In fact, if you go looking you will find it right across South East Asia, including in countries with very large populations such as India, Bangladesh and Indonesia. At the moment my colleagues are working on the epidemiology to try to define just how many people are infected but potentially over a billion people are living in countries known to have melioidosis.
Q: How does your work fit into translational medicine within the department?
SD: What we see is a lot of disease and death from melioidosis. If we are able to find a vaccine, we would be able to take it forward and test it out in models, test it in clinical trials and then get a vaccine to people to stop them getting sick and dying.
This interview was recorded in September 2015.