Experimental vaccines in animal models for schistosomiasis

Abstract

Considerable morbidity and mortality results from the affliction of an estimated 200 million people worldwide by several species of schistosomes; 779 million are exposed to the disease in 74 different countries. Even though anti-parasitic drugs and other control measures, including public hygiene and snail control are available, the advent of an effective vaccine still remains the most potentially powerful means for the control of this disease. The putative vaccine could be administered to small children prior to the time when their contact with infected water is maximal, so as to prevent severe infection in the subsequent years. This review attempts to summarize the status of schistosome vaccine development with special emphasis on functionally important vaccine candidates. The importance of utilizing both murine and nonhuman primate models as a prerequisite for clinical trials is discussed.

Murine schistosomiasis as a model for human schistosomiasis mansoni: similarities and discrepancies

“…Pearce et al (1988) reported that paramyosin stimulates T lymphocytes from vaccinated mice to produce lymphokines that activate macrophages to kill schistosomula. In fact, the experimental vaccines in animal models for schistosomiasis were largely reviewed by Siddiqui et al (2008) and need not to be rereviewed.…”

Schistosomiasis vaccines

“…At present, to our knowledge, Sm-p80 is the sole schistosome vaccine candidate that has been tested for its prophylactic, antifecundity and therapeutic efficacy in different vaccine formulations and approaches (e.g., naked DNA alone; recombinant protein with adjuvants; and prime with DNA, followed by boosting with protein plus adjuvants) in two experimental animal models (mouse and baboon) of infection and disease. 16,[50][51][52][53][54][55][56][57][58][59][60][61][62] Furthermore, the validity of Sm-p80 as a viable vaccine candidate has been reinforced by the work of five "research groups" who have independently demonstrated reproducible and consistent protective efficacy in mice following challenge infection using calpain or its peptides as an antigen (Nagoya City University Medical School, Nagoya, Japan; 63 [50][51][52][53][54][55][56][57][58][59][60][61][62] ). Sm-p80-based vaccine formulations have three protective effects: worm reduction, antifecundity effect and protection against acute schistosomiasis.…”

“…The list of antigens and associated prophylactic efficacy has been extensively reviewed in the last few years. 10,12,16,27,[42][43][44][45] From all of these antigens, only one S. hematobium antigen, Sh-28-GST, has advanced into clinical trials, though this occurred over a decade ago and detailed findings are not available. 46 Another important schistosome antigen, Sm-14, a fatty acid binding protein has also been developed for clinical trials.…”

“…We believe that host-exposed schistosome proteins that undertake such essential functions will be effective targets for a schistosomiasis vaccine. 16 In this regard, our group has targeted a host interactive schistosome protein, calpain (Sm-p80) which plays an important role in the surface membrane renewal of schistosomes, a phenomenon which is widely considered to be a mechanism employed by hemo-helminths to evade host immunity. 49 PZQ-based morbidity control for schistosomiasis has been useful but there are distinct disadvantages associated with this strategy.…”

“…15 There is now general agreement among experts in the field that durable and sustained reduction in the disease spectrum and transmission can only be obtained through long-term protection via vaccination linked with chemotherapy. 10,15,16 An effective anti-schistosome vaccine would contribute greatly to a decrease in morbidity associated with schistosomiasis via protective immune responses leading to reduced worm burdens and decreased egg production.…”