Schistosomiasis vaccine development: approaches and prospects

Abstract

Mounting evidence for acquired immunity to schistosomiasis in humans supports the case for immunological intervention. On the other hand, rapid reinfection poses a threat to younger age groups due to the slow maturation of natural resistance. However, rational approaches, based on advances in immunology and molecular biology, have substantially increased the odds of producing an effective vaccine. Since the parasite cannot replicate in the human host and serious morbidity generally occurs only after a relatively long period of heavy worm burden, complete protection against infection is not essential. The chances of success would increase if more than one of the various host/parasite interphases were targeted, for example reducing morbidity through decreased worm loads as well as through suppression of egg production. Several promising schistosome antigens have now reached an advanced phase of development and are currently undergoing independent confirmatory testing according to a standardized protocol. A few molecules are being contemplated for scaled-up production but, so far, only one has reached the stage of industrial manufacture and safety testing. Since schistosomiasis cannot realistically be controlled by a single approach, vaccination is envisaged to be implemented in conjunction with other means of control, notably chemotherapy.

Sm14 gene expression in different stages of the Schistosoma mansoni life cycle and immunolocalization of the Sm14 protein within the adult worm

“…Therefore, much effort has been devoted to research for vaccine development. Recently, the World Health Organization selected six molecule candidates to compose a subunit vaccine against schistosomiasis (3). One of them is Sm14, a 14-kDa Schistosoma mansoni antigen that induces partial protection in mice following vaccination and cercarial challenge (4).…”

Schistosoma mansoni heat shock protein 70 elicits an early humoral immune response in S. mansoni infected baboons

“…Thus, much research has been done to identify and characterize antigens that may have vaccine and/or diagnostic potential. The application of the recombinant DNA techniques to the studies of Schistosoma antigens has provided some remarkable findings, with definitive characterization of many different antigens (Bergquist 1995, Hamilton et al 1998, Davis 2000. The humoral immune response to S. mansoni has been shown to be directed against a great number of egg, larval and adult stage antigens of the parasite.…”

Identification of immunodominant epitopes of Schistosoma mansoni vaccine candidate antigens using human T cells

“…Among schistosome proteins tested as immunogens in experimental immunization protocols, Sm14 and paramyosin are two promising molecules to compose a subunit vaccine against schistosomiasis (Bergquist 1995). Paramyosin or Sm97 is a myofibrillar protein of 97 kDa located in the muscles and tegument of schistosome worms (Pearce et al 1988 naive mice, in an early stage of the challenge infection, results in partial but significant reduction in worm burden (Lanar et al 1986).…”