| Schistosomiasis is a serious threat to the public health. Nowadays in China, endemic for schistosomiasis japonica, there are more than eight hundred thousand patients and near one hundred million people being threatened according to the countrywide investigation in 2003. Because of the increased morbidity in recent years, schistosomiasis japonica has been focused by Chinese government as one of the infectious diseases that should be controlled in stress.The comprehensive measures for controlling schistosomiasis were based on the population chemotherapy by praziquantel, combined with propaganda of health and killing snails in endemic areas, which have made great achievements. However, the control task is being challenged by the change of natural circumstance and decreased financial aid and the most important challenge is high ratio of reinfection after chemotherapy due to large numbers of reservoir hosts and difficulties in controlling the areas with Oncomelania hupensis. In 1980s the worldwide scientists reached consensus that is the priority to develop an effective anti-schistosomiasis vaccine in order to prevent reinfection after chemotherapy.During the past decades the vaccine and its basic immunological researches were mainly concerned on schistosomiasis mansoni. This is due to the life cycle of Schistosoma mansoni being easy to maintain in the laboratory and the epidemic areas of schistosomiasis mansoni being much broader than schistosomiasis japonica. Moreover, there are several aspects in S. japonicum, e.g. retention time of schistosomula in the skin, migration speed and laying eggs, different from S. mansoni. Thus, based on the relevant knowledge, we should carry out fundamental immunological research work in purpose of developing effective and specific vaccine against schistosomiasis japonica.For a long time, the dominant strategy for vaccine development was to mimic protective immune response in hosts after natural infection. From 1960s to 1980, the concomitant immunity induced by adult worms in host body was thought to prevent invading schistosomula. However, in the early1990s it was suspected in mouse and rat model. Although the newly transformed larvae were found to be killed by IgE-dependent eosinophil-mediated cytotoxicity (ADCC) in vitro, no document has reported the similar phenomenon in vivo. The immuno-epidemiological investigations of population in endemic areas showed that the high level of IgE was related with the resistance to reinfection. However, those vaccine candidate antigens identified from schistosome gene library with IgE antibody have only showed low levels of protective immunity in vaccinated animal models, i.e. adult worm burden was reduced by less than 40 per cent. Later, the theory of ADCC for vaccine was challenged by the potential blocking antibodies. It was discovered that the immune reponse in naturally infected hosts shifts from Th1 type at early stage to Th2 type at chronic stage, eventually preventing host from deadly pathological lesions and parasites per se from steriling immunity. This might be genetically inherited during long-term co-evolution and the parasites in host could only induce non-sterilizing immunity rendering low level of protection. Meanwhile, attenuated cercariae (AC) were found to induce much higher level of protection in various animal models than any candidate antigen. It has been documented that vaccination with no matter γ-irradiated S. mansoni cercariae or ultraviolet-attenuated S. japonicum cercariae, no matter once or multiple times, even no matter in mouse and rat or in big primates such as pigs and buffaloes, could all reduce adult worm burden in hosts by 60 to 80 per cent. Although this kind of vaccine, due to safety and ethical problem, is not realistic to be used, the researches about its immunological mechanisms will help us clarify theory about acquired immunity in natural infection and develop a novel strategy for the vaccine against schistosomiasis.Many studies have suggested that the protection is provided mainly by cellular immunity. Afte...
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