West Nile Virus DNA vaccine produces neutralizing antibodies in phase I trial - DNA

West Nile Virus DNA vaccine produces neutralizing antibodies in phase I trial
June 27, 2006
Therapeutics Daily
Vical Incorporated (VICL) announced that in a phase I clinical trial, a West Nile virus (WNV) vaccine candidate administered using Vical's proprietary DNA delivery technology was safe and well tolerated, and produced neutralizing antibody WNV-specific responses in all 11 healthy volunteers who returned for follow-up testing after completing the three-dose vaccination schedule.
The phase I, open-label clinical trial study was sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and conducted at the NIH Clinical Center. The data were presented at the American Society of Gene Therapy (ASGT) 2006 Annual Meeting in Baltimore, MD, by Julie E. Martin, DO, a trial investigator and research scientist at NIAID's Dale and Betty Bumpers Vaccine Research Center (VRC), which developed the vaccine.
The DNA vaccine used in the phase I trial incorporates genetic material encoding precursor membrane (prM) and envelope (E) proteins from the West Nile virus. Vical has secured a license from the U.S. Centers for Disease Control and Prevention for technology used in the vaccine. This WNV vaccine candidate was jointly developed by the VRC, NIAID, NIH and Vical under a Cooperative Research and Development Agreement (CRADA), and Vical has an option to secure exclusive commercialization rights from the NIH under the CRADA.
"This vaccine was previously shown to be highly immunogenic in animal studies, and the high rate of seroconversion in humans, as measured in this study by neutralizing antibody titers, adds to the growing body of evidence demonstrating immunogenicity with DNA vaccines in humans as well," said David C. Kaslow, MD, Vical's chief scientific officer. "Furthermore, the data encourage investigation of vaccines against diseases caused by other flaviviruses such as yellow fever, Japanese encephalitis, and dengue, as well as other diseases for which antibody responses may be protective."
The vaccine used in the phase I trial contained a single plasmid (closed loop of DNA) encoding precursor membrane (prM) and envelope (E) proteins from the West Nile virus. Fifteen subjects were enrolled and 12 completed the vaccination schedule, which consisted of three 4 mg doses of vaccine at 1-month intervals via intramuscular needle-free injection.
The vaccine was well tolerated, and there were no severe adverse reactions to the vaccine. Among the 12 volunteers who completed the 3-dose vaccination schedule, 11 returned for follow-up testing. WNV-specific neutralizing antibody responses were detected in all 11, as well as in some subjects following just 2 doses.
West Nile virus belongs to a group of disease-causing viruses known as flaviviruses that are usually spread by ticks or mosquitoes. WNV was first isolated in Uganda in 1937. It is most common in Africa, West Asia, Europe, and the Middle East. In the Western Hemisphere, it was found for the first time in 1999 in the New York City area. It subsequently spread to other parts of the United States, and by 2004 had been found in birds and mosquitoes in every state except Alaska and Hawaii.
According to the U.S. Centers for Disease Control and Prevention (CDC), WNV caused 2949 cases of disease and 116 deaths in the United States in 2005. Human cases have now been reported throughout the continental United States as well as in Canada and Mexico.
WNV infection in humans usually causes only mild symptoms-fever, headache, body aches, skin rash, and swollen lymph glands. If WNV enters the brain, however, it can cause life-threatening encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). Most cases of disease occur in elderly people and those with impaired immune systems. Although licensed WNV vaccines exist for horses, there are no specific vaccines or treatments approved for human WNV disease.
This article was prepared by Virus Weekly editors from staff and other reports.