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PARASITES CAUSING AFRICAN SLEEPING SICKNESS CONSTANTLY CHANGE THEIR COATS FOR DISGUISE
“African sleeping sickness is endemic to subSaharan African, and is always fatal if it’s not treated”, says Dr Gloria Rudenko of the University of Oxford. “Unfortunately the available drugs are also highly toxic. Vaccination is impossible since the single-celled organisms called trypanosomes, which get into our blood and cause the disease, have developed a highly sophisticated set of disguises, like wearing a series of different fur coats. By the time our bodies have learned how to recognise one coat, the trypanosomes have simply switched to another variation of the surface covering not recognised by our bodies’ defences”. African trypanosomes are very unusual parasites since they don’t hide from our bodies’ defences by penetrating our cells to escape detection, like malaria parasites do. Instead they swim free in our blood, multiplying and causing serious infections, constantly one step ahead of our immune systems. The parasites are covered in a dense layer of sugary protein, similar to a fur coat. Preventing them from making this coat does not result in ‘naked’ parasites, but causes the cells to stop dividing, presumably to prevent drastic dilution of the coat. The scientists have discovered that even very small reductions in the surface coat, like chinks in the armour, allow any normal individual to kill the trypanosome parasite. So finding out how the organism makes the surface coat will provide an excellent drug target. “During the course of a serious infection, trypanosomes can switch between hundreds of different surface coats”, says Dr Rudenko. “We need to find out how they switch between coats so that other researchers can develop a chemical method capable of disrupting it”.
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