Schistosome vaccines: a critical appraisal

Current Status of Vaccines for Schistosomiasis

“…Vaccination against schistosomes can be targeted towards the prevention of infection and/or to the reduction of parasite fecundity. A reduction in worm numbers is the "gold standard" for antischistosome vaccine development, with the migrating schistosomulum stage likely to be the major vaccine target of protective immune responses (99,163). However, as schistosome eggs are responsible for both pathology and transmission, a vaccine targeted at parasite fecundity and egg viability also appears entirely appropriate.…”

Schistosomes—proteomics studies for potential novel vaccines and drug targets

“…Despite promising preliminary results, tests with six selected antigens (glutathione-S-transferase (SmGST), triose phosphate isomerase (TPI), paramyosin, 23 kDa integral membrane tetraspanin protein (Sm23), myosin heavy chain (IrV5) and 14 kDa fatty acid binding protein (Sm14)) by independently contracted laboratories in the Schistosoma mansoni/ mouse experimental system showed disappointing results [20]. In addition, all these antigens, with the exception of Sm23, are not expected to display an extracellular location and are instead cytosolic or cytoskeletal components, which raises doubts about the mechanisms of how they trigger the immune effector system [21]. Currently, Phase I and II clinical trials in humans are underway using S. hematobium glutathione-S-transferase; on the basis of previous results it is hoped that vaccination with this antigen should help to limit pathology and improve the efficiency of Praziquantel [22].…”

Control of Schistosomiasis

“…Several investigations have confirmed that the severity of clinical disease is dependent on intensity of infection rather than simply the presence or absence of infection (Lehman et al,1976 ;Chen and Mott, 1988) implying that even an incomplete immunity may be of considerable value. An excellent review on the search for a schistosome vaccine was published not too long ago by Wilson and Coulson (2006). These authors rightly chronicled the search for the discovery of candidate vaccine molecules to have transited through mining crude extracts, monoclonal antibody targets, anti-idiotypes, expression library screening and immunogenicity.…”

“…The early disappointment that was recorded with the vaccination of mice with crude worm extracts or purified components, followed by cercarial challenge (Sadun and Lin,1959 ;Murrell et al, 1975) and utilizing the idea of concomitant immunity (Smithers and Terry, 1969) were equally reviewed. Wilson and Coulson (2006) concluded that the sequencing of S. mansoni transriptome and genome and the development of proteomic and microarray technologies has drastically improved the possibilities for identiflying novel vaccine candidates, particularly proteins secreted from or exposed at the surface of schistosomula and adult worms. The parameters of an attenuated schistosome vaccine has been evaluated in the Olive Baboon (Kariuki et al, 2004).…”