From 2000 to 2017 the Sabin Vaccine Institute partnered with the Texas Children’s Hospital Center for Vaccine Development at Baylor College of Medicine in Houston, Texas to develop safe, effective and low-cost vaccines for infectious and neglected tropical diseases. Baylor College of Medicine and Texas Children’s Hospital Center for Vaccine Development continue this research as of May 2017.
Schistosomiasis is a parasitic disease that places a heavy burden on the world’s poorest populations, particularly in Africa.
About the Vaccine
Sabin Vaccine Institute Product Development Partnership (Sabin PDP) launched the Schistosomiasis Vaccine Initiative in 2008 through funding from Mr. and Mrs. Morton and Chris Hyman and the Blavatnik Family Foundation to advance the development and global accessibility of a low-cost, safe and effective vaccine for schistosomiasis. Working together with a network of global partners, the Sabin PDP advanced research and development of a safe and efficacious vaccine to prevent schistosomiasis. As of May 2017, Baylor College of Medicine and the Texas Children’s Hospital’s Center for Vaccine Development continue this research.
This project drives the development of Sm-TSP-2/Alhydrogel® schistosomiasis vaccine, which targets intestinal schistosomiasis caused by Schistosoma mansoni. Sm-TSP-2 has great potential as a vaccine candidate to prevent schistosomiasis. Studies performed in populations living in schistosomiasis-endemic areas found that people who hadn’t been infected with schistosomiasis in the last ten years – and who are therefore likely immune from the disease – were the only ones that exhibited an immune response against Sm-TSP-2. This indicates that an immune response against this antigen may be associated with protection against schistosomiasis. Later studies showed that vaccinating mice with this antigen protected them from schistosomiasis infection.
Phase 1 clinical trials for Sm-TSP-2 are ongoing in the United States and Brazil. This work could ultimately lead to the first vaccine to prevent schistosomiasis infection.
Schistosomiasis is a disabling disease responsible for the loss of up to 70 million productive years of life globally every year. In 2015, 218 million people around the world required schistosomiasis treatment, approximately 90 percent of whom were in Africa. The WHO estimates that schistosomiasis results in approximately 200,000 deaths annually, though it is difficult to calculate the exact number due hidden impacts of schistosomiasis, like liver failure and bladder cancer. In endemic areas, chronic schistosomiasis has a significant impact on child development due to anemia, impaired growth and poor school performance in children.
Schistosomiasis is an acute and chronic parasitic disease caused by infection with Schistosoma worms. Schistosomiasis infection occurs through contact with schistosome larvae, which grow in freshwater snails before being released into the surrounding water. As a result, people who come in frequent contact with contaminated water sources – notably children at play and women conducting domestic chores – are the most susceptible to contracting schistosomiasis.
Once inside the body, Schistosoma larvae develop into adult worms that can live for years inside the blood vessels around the intestines or bladder. The body’s reaction to eggs produced by adult worms induces debilitating symptoms, including anemia, malnutrition and bloody stool or urine. Chronic schistosomiasis can cause severe kidney, spleen or liver damage, and has even been associated with bladder cancer.
One form of urogenital schistosomiasis – female genital schistosomiasis (FGS) – is one of the most common gynecologic conditions in sub-Saharan Africa, affecting as many as 150 million girls and women. FGS has a particularly significant impact on global health as an important co-factor in HIV transmission; FGS leaves its sufferers at a three-fold higher risk of contracting HIV.
Why We Need a Vaccine
In 2012, the World Health Assembly adopted a resolution for the global elimination of schistosomiasis. The current global strategy to control schistosomiasis is based on large-scale treatment of at-risk populations with the drug praziquantel.
Despite increased support for schistosomiasis control efforts, prevalence of this disease has increased by more than 30 percent over the last decade. Most people living in schistosomiasis-endemic communities are at a constant risk of re-infection due to continued, regular exposure to contaminated water. As a result, these populations require regular treatment to control schistosomiasis, in some areas as frequently as every year. Mass drug administration programs currently reach only 28.2 percent of those requiring treatment for schistosomiasis around the world, and increased movement of infected populations due to political unrest or urbanization is helping schistosomiasis spread to new areas.
An effective preventative vaccine would represent an important tool in schistosomiasis control and elimination. It is currently not feasible to deliver schistosomiasis treatment to communities frequently enough to interrupt transmission of the disease. Praziquantel is currently the only drug used to treat schistosomiasis, leaving no alternative method of treatment should drug resistance become widespread. An effective vaccine would eliminate the need for regular mass drug administration by preventing re-infection following treatment.