January 8th, 2007 11:53 EST
NIH reports progress in vaccine development for avian influenza
Washington -- The U.S. Department of Health and Human Services (HHS) awarded a $102.6 million, four-year contract to Alabama-based BioCryst Pharmaceuticals January 4 to develop the company’s influenza antiviral drug, peramivir, and the National Institutes of Health (NIH) has begun testing in people of a DNA vaccine that could prevent avian flu.
In laboratory studies, peramivir has been effective against several influenza strains. Funding under the contract will support studies to determine if peramivir can be an effective treatment for seasonal and life-threatening influenza, including H5N1.
Other research also may examine the drug's potential to prevent influenza infection.
H5N1 is the highly pathogenic strain of bird flu that has reached pandemic levels among birds in Asia and has spread to Africa and Europe, causing the deaths of more than 200 million birds. Since 2003, the virus has been transmitted to 261 people in 10 countries, killing 157, according to the World Health Organization.
Nearly all human cases have come from direct contact with infected poultry. There have been a few cases of person-to-person transmission, but the virus does not transmit easily among people. Experts fear that if the virus mutates to become easily transmissible among people, a worldwide pandemic could result.
"Our antiviral strategy includes not only stockpiling existing antiviral drugs but also seeking out new antiviral medications to further broaden our capabilities to treat and prevent all forms of influenza,” said HHS Secretary Michael Leavitt in a January 4 statement.
Four antiviral medications -- amantadine (brand name Symmetrel®), rimantadine (Flumadine®), zanamavir (Relenza®) and oseltamivir (Tamiflu®) -- are approved by the U.S. Food and Drug Administration to treat and prevent influenza. When used for prevention, they are 70-90 percent effective in preventing illness in healthy adults, according to the U.S. Centers for Disease Control and Prevention (CDC).
People can be infected with influenza types A, B and C viruses. H5N1 is a subtype of influenza A. Wild birds are the natural hosts for all known subtypes of influenza A viruses.
All the antiviral medications may be effective for influenza A viruses, but only oseltamivir and zanamivir are effective for influenza B viruses. According to CDC, recent evidence shows that a high proportion of circulating influenza A viruses in the United States have developed resistance to amantadine and rimantadine.
Peramivir is a member of the same class of antiviral drugs as oseltamivir, which is taken by mouth, and zanamivir, which is used in an inhaler. But peramivir is being studied as a drug that can be administered parenterally, meaning by using a needle to inject the drug into a vein or muscle.
The injectable drug may be especially useful in hospital settings, where it can be given to people with life-threatening flu on admission to emergency rooms. Other advantages are the potential for high levels of the drug to travel quickly through the body and its ability to be given to people too ill to take medications by mouth.
DNA VACCINE FOR AVIAN FLU
The first human trial of a DNA vaccine designed to prevent H5N1 avian influenza infection began December 21, 2006, at NIH in Maryland.
Scientists from the Vaccine Research Center (VRC) at the NIH National Institute of Allergy and Infectious Diseases (NIAID) designed the vaccine. The vaccine does not contain infectious material from the flu virus.
Unlike conventional flu vaccines, developed by growing the flu virus in hens' eggs and administered as a weakened or killed form of the virus, DNA-based vaccines contain only parts of the flu virus's genetic material. In the body, the DNA tells human cells to make proteins that act as a vaccine against the virus.
"An effective H5N1 influenza vaccine would provide a potentially life-saving advance against a global health threat," said NIAID Director Anthony Fauci in a January 2 statement.
VRC Director Gary Nabel and VRC scientists recognized the potential for using new vaccine technology against influenza. Effective vaccines long have been available for flu, but supply reliability and manufacturing capacity have been problems.
With the spread of avian flu, new strains have emerged that have drifted genetically from initial strains detected in Southeast Asia. With this study, the investigators hope to learn whether new technologies, such as DNA vaccines, can protect against such viruses.
"This vaccine,” Nabel said, “is aimed at newer strains of the H5N1 virus that currently pose a threat in Indonesia and represents an example of our ability to respond to shifting viruses with modern technology."
The study will enroll 45 volunteers between ages 18 and 60; 15 will receive placebo injections and 30 will receive three injections of the investigational vaccine over two months and will be followed for a year.
More information about influenza is available on the NIAID Web site.
For ongoing coverage of the disease and efforts to combat it, see Bird Flu (Avian Influenza).
(USINFO is produced by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)By Cheryl Pellerin
USINFO Staff Writer