Leishmaniasis is a parasitic disease that kills about 60,000 people annually. It spreads by the bite of infected female sand flies. Visceral leishmaniasis infects about 500,000 people annually mainly in India, Bangladesh, Nepal, Sudan and Brazil. The most common drugs to treat leishmaniasis have serious side effects and are expensive. Symptoms of visceral leishmaniasis include fever, weight loss, and abnormalities of the liver and spleen. As there is no effective vaccine for the visceral, or internal, form of leishmaniasis till date there is an increase in the death rate due to the disease. Peter H. Seeberger, Ph.D., of the Laboratory for Organic Chemistry at the Swiss Federal Institute of Technology (ETH) in Zurich developed a fundamentally new vaccine for the disease. The research team consisted of scientists from the Swiss Tropical Institute in Basel and Pevion Inc., a biotech company focusing on virosomal delivery systems.
The results of the research findings were reported in ACS Chemical Biology, one of 34 peer-reviewed journals published by the American Chemical Society, the world’s largest scientific society. Several leishmaniasis candidate vaccines are in various stages of development. The vaccine is a new genre of carbohydrate-based vaccines. Carbohydrates are chemical compounds that include sugar which are linked together. The vaccine is not only useful in humans but can be used to protect pets (dogs) against leishmaniasis. Carbohydrate vaccines are used in everyday medicine, including vaccines to immunize against meningitis and other bacterial infections, mainly in small children in the United States. Those vaccines use carbohydrates isolated from the actual bacteria responsible for the diseases.The carbohydrates act as antigens, which stimulate the immune system to produce antibodies. But now synthetic carbohydrates are used as antigens in order to control the purity and composition and avoid possible contamination. But one major drawback with carbohydrate vaccines is the difficulty in getting them to produce a strong immune response. Vaccine manufacturers achieve this by adding a booster substance called adjuvant. Seeberger’s vaccine against leishmaniasis combines the delivery vehicle, immune-stimulating antigen and adjuvant into one package.
The delivery vehicle is an influenza virosome that is an empty envelope of the influenza virus. They contain none of the infectious genetic material of the flu viruses. The virosome also acts as an adjuvant, boosting the immune response of the vaccine. The antigen is a synthetic carbohydrate similar to substances on the surface of the leishmaniasis bacteria. Seeberger’s group is planning to test the vaccine on animals. WHO assigned a high priority to development of a leishmaniasis vaccine because of the huge human toll and the lack of any effective treatment.
