Scientists with the U.S. Food and Drug Administration's Office of Blood Research and Review recently developed a live-attenuated vaccine for visceral leishmaniasis, a tropical disease that infects 12 million people annually.
Visceral leishmaniasis is caused by the Leishmania protozoan and represents the most severe form of the disease. The parasite spreads when sand flies bite humans and parasites disrupt the human immune system causing liver and spleen damage.
The OBRR scientists are developing a live-attenuated vaccine by studying its effects in mice and hamsters. They created the vaccine by eliminating certain genes in the Leishmania protozoan, including a gene that regulates growth and one that affects a metabolic enzyme.
Researchers could also use the process used for the leishmaniasis vaccine to create vaccine candidates for other parasitic pathogens that infect blood cells including malaria and babesia.
While leishmaniasis typically affects tropical and subtropical countries like Brazil, Sudan, India, Nepal and Bangladesh, millions of American travelers and military personnel are at risk when visiting endemic areas. The disease is spreading because of international travel and occasional cases were reported in the southwest United States. Global warming could also allow the disease to spread to more northern states.
There are currently no effective vaccines available for leishmaniasis and chemotherapy is one of the few methods of treatment. Approximately 50,000 people die each year from the infection.