Schistosomiasis vaccine development: update on human clinical trials

Abstract

Schistosomiasis causes significant levels of morbidity and mortality in many geographical regions of the world. The disease is caused by infections with parasitic blood flukes known as schistosomes. The control of schistosomiasis over the last several decades has been centered on the mass drug administration (MDA) of praziquantel (PZQ), which is the only drug currently available for treatment. Despite the concerted efforts of MDA programs, the prevalence and transmission of schistosomiasis has remained largely unchecked due to the fact that PZQ is ineffective against juvenile schistosomes, does not prevent re-infection and the emergence of PZQ-resistant parasites. In addition, other measures such as the water, sanitation and hygiene programs and snail intermediate hosts control have had little to no impact. These drawbacks indicate that the current control strategies are severely inadequate at interrupting transmission and therefore, implementation of other control strategies are required. Ideally, an efficient vaccine is what is needed for long term protection thereby eliminating the current efforts of repeated mass drug administration. However, the general consensus in the field is that the integration of a viable vaccine with MDA and other control measures offer the best chance of achieving the goal of schistosomiasis elimination. This review focuses on the present status of schistosomiasis vaccine candidates in different phases of human clinical trials and provide some insight into future vaccine discovery and design.

Investigating Immunization With Nucleotide Enzymes of Schistosoma mansoni: Nucleoside Diphosphate Kinase and Adenylosuccinate Lyase as New Antigenic Targets Against Schistosomiasis

“…vaccine agents that have advanced to clinical tests (Sm-TSP-2, Sm-p80, and Sm14) (9). Thus, studies that seek to identify new immunogens for this disease, such as the recombinant enzymes NDPK and ADSL of S. mansoni, remain an urgent need for the development of a vaccine formulation.…”

“…Due to the retention of eggs in the liver, intestine and spleen, there is the occurrence of fibrosis and organ calcification, in addition to hepatosplenomegaly ( 26 , 27 ). There are still no vaccines available for schistosomiasis and there are few potential vaccine agents that have advanced to clinical tests (Sm-TSP-2, Sm-p80, and Sm14) ( 9 ). Thus, studies that seek to identify new immunogens for this disease, such as the recombinant enzymes NDPK and ADSL of S. mansoni , remain an urgent need for the development of a vaccine formulation.…”

“…The immune response to S. mansoni infection has been extensively studied with the objective of identifying antigens that can elucidate the protective response in immunized individuals. Although there are no vaccines available for human use against schistosomiasis, a study with potential candidates in the clinical phase and in experimental models supports the feasibility of developing an effective vaccine (9).…”

“…Due to the inadequacies and limitations of the approaches to control schistosomiasis centered on treatment with PZQ, it is necessary to develop a vaccine for this parasitosis (9). The immune response to S. mansoni infection has been extensively studied with the objective of identifying antigens that can elucidate the protective response in immunized individuals.…”

Bioinformatics evaluation of the homologues ofSchistosoma mansonibiomarker proteins of bladder cancer in otherSchistosomaspecies

“…There were also case reports of travelers who were infected during their stay in endemic areas and were treated with praziquantel, but resulted in treatment failure (Secor and Montogomery, 2015). Vaccine development against this disease has experienced more failure than successes, (although there is currently a vaccine trial going on for schistosomiasis in Africa (Molehin, 2020); therefore, the identification of molecular targets that can induce protective immunity is highly desirable.…”