Virologists working on DNA vaccines for H5N1 virus
September 4, 2008, 12:00 am TWN
TAIPEI, Taiwan -- Scientists at the Academia Sinica are working on developing some novel vaccines for the avian influenza H5N1 virus and DNA-based vaccines have proven to be capable of providing protection for various H5N1 strains, researchers at the institution said yesterday.
A team of researchers at Taiwan's leading academic body has also discovered that once new virus strains are found, the strains' genetic information can be incorporated into the vaccine database to produce new vaccines that can induce immunity against new strains of H5N1, one of the academics said.
The findings of the team, led by David Ho of the Rockefeller University and Chi-huey Wong of Academia Sinica's Genomics Research Center, were published on Sept. 2 in the online edition of the publication "Proceedings of the National Academy of Sciences".
The team started its research two years ago with the focus on hemagglutinin, or HA — a type of glycoprotein molecule that can be found on the surface of all H5N1 viruses and plays a vital role in the viral infection process, according to a press release of the Academia Sinica.
After analyzing hundreds of hemagglutinin samples that were collected from various H5N1 strains, an identical gene sequence — dubbed "Consensus HA" — were found on all specimens.
The sequence was later genetically engineered to produce the prototype vaccines.
During experiments, lab mice that have been inoculated were found to develop immunity of various H5N1 strains, including the strains found in Vietnam, Indonesia, Turkey, and southern China.
"When infected by the Indonesian strain of H5N1, 80 percent of the subject mice survived, " said Ting-jen Rachel Cheng of the Genomics Research Center.
"Meanwhile, 100-percent survival rates were found among all mice that were exposed to the other three strains," she said.
However, DNA-based vaccines have one distinct drawback.
"Based on the experiments (and) research done by other scientists, DNA-based vaccines are prone to elicit weak immune response, " said Chen Ming- wei, a post-graduate student at National Yang-Ming University and the paper's lead author.
The team therefore decided to enhance the vaccines' effects with an electroporation device developed by Ho, Chen said, adding that the device injects the vaccine into the muscle while generating a brief electrical pulse to "push" the DNA into the cells.
"Delivered in this way, the DNA-based vaccine induced quite drastic immune responses, and protected mice against most of the avian flu strains tested," he said.
The newly developed vaccines have been transferred to the Development Center for Biotechnology — a Taiwan-based non- profit organization — to undergo animal safety tests, according to the Academia Sinica.
After further testing is completed by the end of 2008, the vaccine will be submitted to the U.S. Department of Health and the Food and Drug Administration as a new drug awaiting human trials. Once approved, the phase-I clinical trial in humans can be carried out.