A vaccine against Asian schistosomiasis

There is continued transmission of schistosomiasis japonica in China and Philippines despite highly effective control programs that focus on the application of the highly effective drug praziquantel (PZQ). The massive Three Gorges Dam across the Yangtze River in Southern China, soon to be completed, is expected to significantly increase schistosomiasis transmission and introduce the disease into areas currently unaffected. After long-term experience it is generally accepted that PZQ chemotherapy, although the cornerstone of current control programs, does have significant limitations. Furthermore, efficient drug delivery requires a substantial infrastructure to regularly cover all parts of an endemic area. Although there is not yet clear-cut evidence for the existence of PZQ-resistant schistosome strains, decreased susceptibility to the drug has been observed in several countries. As a result, a protective vaccine represents an essential component for the long-term control of schistosomiasis. This article briefly reviews aspects of anti-schistosome protective immunity that are important in the context of vaccine development. The current status in the development of vaccines against Schistosoma japonicum will then be discussed as will new approaches that may improve on the efficacy of available vaccines, and aid in the identification of new targets for immune attack. With new and extensive data becoming available from the S. japonicum genome project, the prospects for developing an effective vaccine are encouraging. The challenges that remain are many but it is crucial that the momentum towards developing effective anti-schistosome vaccines is maintained.