Evaluating Sm-p80 Vaccine Cross-Species Protection against Schistosoma haematobium in Hamsters

Background:

Schistosomiasis remains a major health problem affecting over 230 million people worldwide. Despite control efforts, clear limitations, such as re-infection rates and drug resistance, necessitate the development of a vaccine for long term protection against the disease. Schistosoma mansoni antigen, Sm-p80, is a protein involved in host immune evasion by schistosomes due to its role in parasite membrane biogenesis. Previous Sm-p80-based vaccination studies have consistently shown high levels of protection against S. mansoni infections in animal models. We therefore hypothesize that induction of specific host immune responses through Sm-p80-based vaccination would provide the opportunity to control urinary schistosomiasis caused by S. haematobium infection. In this study, we evaluated the cross-species protective efficacy of Sm-p80 vaccine against S. haematobium infections in hamsters.

Methods:

DNA vaccine was prepared by cloning the coding sequence of Sm-p80 into VR1020 plasmid. Sm-p80/VR1020 plasmid was isolated and then purified on Sepharose column. Recombinant protein vaccine was generated by cloning the coding sequence for Sm-p80 gene in pCold II vector and expressed in Escherichia coli followed by affinity chromatography. Two groups of hamsters were immunized with either delivery vehicle only (control group) or DNA/protein vaccine (vaccinated group) and subsequently challenged with 200 S. haematobium cercariae. Sm-p80-specific antibody titers were measured by ELISA. Vaccine efficacy was determined by worm reduction and tissue egg load.

Results:

Immunization with Sm-p80 vaccine elicited a balanced Th1/Th2 response as shown by the significant production of Sm-p80-specific IgG antibodies in the immunized animals when compared to controls. Significant reduction in worm burden (26.9%) was observed in vaccinated hamsters when compared to the controls. However, there was no reduction in tissue egg loads between the two groups.

Conclusion:

The results presented in this study demonstrated that immunizations with Sm-p80 vaccine conferred cross-species protection against S. haematobium infections thereby reinforcing Sm-p80 as a promising vaccine that could provide relief for both intestinal and urinary schistosomiasis.