The Journal of Parasitology, the official journal of the American Society of Parasitologists, announced the test results of immunization combinations in mice. Researchers are seeking the correct vaccine antigen that will ensure effective immunization against this parasite.
Snails can carry this parasite to humans, typically in places lacking water sanitation facilities. Although mortality is low, schistosomiasis can cause progressive liver or urinary bladder tissue damage. Subsequent infections can be more severe after a first exposure to schistosomiasis.
The drug praziquantel has been effective in killing this parasite. However, it does not prevent infection, and there is concern that the parasite will develop resistance to the drug, which is now in widespread use. A vaccine is needed.
Looking for the correct antigen, researchers in the current study focused on excretory-secretory products (ESP) of the Schistosoma mansoni parasite. These products are released during the early and later stages of infection. The researchers hypothesized that attacking ESP-induced immune responses would lead to almost total elimination of the parasite.
In the current study, the researchers first immunized mice and two weeks later exposed the mice to the parasite. Six experiments consistently showed a highly significant 62 per cent to 78 per cent reduction in challenge worm burden compared to untreated controls.
These experiments have shown consistent, reproducible results in repeated tests. The next steps toward a schistosomiasis vaccine should be to clarify the molecular basis of protection and move toward production of the antigen, independent trials, and preclinical and clinical studies.