SATURDAY, SEPTEMBER 24, 2016

New vaccine could protect 800 million at risk for schistosomiasis

Researchers are targeting a new vaccine that could protect close to 800 million people in more than 75 developing countries at risk of a widespread parasitic disease, according to a recent study.

The Schistosoma mansoni parasite is endemic in 76 countries and causes schistosomiasis, a disease that causes an annual loss of up to 30 million disability-adjusted life years, the most of all neglected tropical diseases. Infection with the disease causes progressive liver or urinary bladder tissue damage from fibrosis and increased severity of subsequent infections with other pathogens, the Journal of Parasitology reports.

"Infection with schistosomes increases the severity of subsequent infection with other pathogens, namely, Plasmodium falciparum, Leishmania spp., Toxoplasma gondii, Mycobacteria, Entamoeba histolytica, Staphylococcus aureus, and Salmonella," Hatem Tallima and Rashika El Ridi, the co-authors of the study, said, according to the Journal of Parasitology. "Schistosomiasis also may predispose individuals to infection with human immunodeficiency and hepatitis C virus."

Praziquantel has been used as a cost-effective and efficacious treatment for schistosomiasis. The drug does not, however, prevent reinfection and it requires repeated treatment.

The widespread and mass use of Praziquantel has resulted in parasite resistance. A vaccine against the parasitic disease is needed to more effectively control infection.

The new vaccine candidate, developed by Tallima and El Ridi, is based on the excretory-secretory products of the S. mansoni parasite. The researchers tested ESPs, which elicited innate and acquired immunity against schistosomiasis. A series of six experienced revealed a highly significant 62 to 78 percent reduction in challenge worm burden when compared to untreated control groups.

Tallima and El Ridi are looking to move forward after the successful reproduction of their results in multiple experiments.

"Concerted efforts are needed toward elucidation of the molecular basis of protection, implementation of independent trials, antigen (good manufacturing practices) production, and pre-clinical and clinical studies," Tallima and El Ridi said, according to the Journal of Parasitology. "Concurrently, we are planning to investigate whether a sterilizing schistosomiasis vaccine might be reached via improvement of ESP selection, singly or in a mixture, and immunization regimen, namely, ESP and type-2 cytokine dose and injection site and schedule."

The study was supported by Egypt's Science and Technology Development Fund, the Journal of Parasitology reports.