NIAID supports research on a variety of vaccine approaches that could potentially lead to a safe and effective preventive vaccine for West Nile virus (WNV). These approaches include vaccines containing cocktails of individual WNV proteins and chimeric vaccines, which combine genes from more than one virus into a single vaccine. A third approach involves DNA vaccines, in which DNA that codes for a particular virus protein is combined with bacterial DNA, and the combined product is injected directly into the skin of the person or animal being vaccinated.
Currently, there is no licensed WNV vaccine for people. In 2005, the U.S. Department of Agriculture licensed a DNA vaccine to prevent WNV in horses, and since then, at least four other types of WNV vaccines have been approved for use in horses. Because federal regulations for veterinary products are less stringent than those intended for human use, products developed for animals can proceed at a faster pace.
WNV vaccine research conducted and supported by NIAID includes
- Early-stage research by scientists at Oregon Health and Science University who used hydrogen peroxide treatment as a way to develop inactivated vaccines. This method is being investigated to develop vaccines for a number of illnesses, including West Nile fever and neuroinvasive disease, yellow fever, and dengue.
- A vaccine grown in insect cells that has been shown to produce protective antiviral antibodies in mice infected with WNV and has been shown to prevent WNV disease in horses. This research was conducted by the biotech company L2 Diagnostics, LLD, of New Haven, Connecticut. It remains to be seen if the product will be advanced for use in humans.
- A candidate vaccine made with portions of two WNV proteins is being developed by Hawaii Biotech, Inc., in Aiea, Hawaii. Early research on this product was funded by NIAID. The company has completed a Phase I trial of the vaccine, which successfully demonstrated safety and immunogenicity.
- NIAID-supported researchers at Duke University are working on a WNV vaccine made of immune proteins (called mast cell-activating peptides, or MCAPs) that would be formulated for delivery as a dry nasal powder. The use of MCAPs to create vaccines that can be administered through the nose might be applicable to other diseases as well.
- NIAID provided initial support to the biotech firm Acambis to develop a live attenuated recombinant vaccine for WNV called ChimeriVax. The chimeric vaccine is derived from the well-established yellow fever 17D vaccine, in which two genes from the yellow fever vaccine virus, including the gene for the viral envelope protein, are replaced with comparable genes from WNV. Several successful Phase I and Phase II trials were conducted in various populations of healthy volunteers. ChimeriVax was acquired by Sanofi Pasteur in 2008.
- NIAID scientists are developing a molecularly engineered, live attenuated chimeric West Nile/dengue vaccine. In this candidate vaccine, genes coding for two proteins from dengue-type 4 virus (a related flavivirus) were replaced with the corresponding WNV genes. The candidate vaccines have been further weakened by deleting additional portions of dengue viral genetic material. Several vaccine candidates have been tested in Phase I clinical trials; further trials are planned with varying doses of vaccine and in older healthy individuals.
In collaboration with the San Diego biotech firm Vical and the Centers for Disease Control and Prevention (CDC), scientists from the NIAID Vaccine Research Center developed a DNA-based investigational WNV virus vaccine. This vaccine candidate was tested in Phase I and II clinical trials, and it has been licensed by CDC to Vical.