The way Dr. Joseph Kim sees it, the field of influenza vaccine development could use an extreme makeover.
“Every year, three flu strains are selected by the flu experts around the world, which determines which strains the vaccine makers should make and stock for the coming fall,” Dr. Kim, president and CEO of San Diego–based Inovio Biomedical Corp., said in an interview. “They can guess right, or they can guess wrong; but every year, you have to change the vaccine. You can't stockpile from the previous year, because the flu strains could change.”
Scientists don't accept this approach for most other common vaccines, he noted, including the one for measles, mumps, and rubella. “That doesn't get changed from year to year, but our society has accepted the fact that the one for influenza does,” he said.
Dr. Kim would like to change that paradigm.
Since 2005, he and his associates at Inovio have been developing DNA-based influenza vaccines capable of providing broad protection against existing as well as newly emerging, unknown seasonal and pandemic influenza strains. To design vaccines, the company developed a process known as SynCon, a way of targeting consensus proteins from multiple strains of H1N1, H2N2, H3N2, and H5N1, “which have collectively caused greater than 90% of all seasonal and pandemic flu events in people in the last 100-plus years,” Dr. Kim said. “We felt that those were very good targets.”
What separates Inovio's SynCon approach from that of other DNA vaccine manufacturers is that the SynCon vaccines demonstrate potential to protect against new strains of influenza that do not specifically match the vaccine.
“So, if the 2009 H1N1 virus mutates, there is no plan B,” Dr. Kim said. “There is no backup option; 2009 swine flu could be a big problem or not. No one can predict accurately.”
Origins of an Alternative
DNA-based influenza vaccines began to draw serious attention about 6 years ago, when infectious diseases experts around the globe expressed concern about a pandemic of H5N1 influenza virus, noted Dr. William Schaffner, chair of the department of preventive medicine at Vanderbilt University, Nashville, Tenn.
“That galvanized the international community,” he said. “Since that time, the United States government and private capital have gone into research to develop more improved influenza vaccines and to improve the vaccine technology. There has been more research into those areas in the past 5 or 6 years than there has been in the previous 50 years. That's stunning.”
The concept of DNA vaccines first emerged in the early 1990s, when researchers discovered that immunizing animals with plasmids—a circular string of DNA that encodes for a specific antigen or vaccine target—generates vaccine responses.
“The beauty of this technology is speed,” said Vijay B. Samant, president and CEO of San Diego–based Vical, which develops DNA vaccines. “It's not cell culture. It's not egg-based. It's simple fermentation and two purification steps. It does not require the manufacturer to handle the pathogen. All it needs is a gene sequence; that's good enough for us to make the vaccine.”
“Instead of delivering the viruses themselves in some form, you're taking a very simple plasmid, which is a circular string of DNA, and you're putting in a genetic blueprint designed for a specific target, in this case hemagglutinin,” Dr. Kim explained. “Once you inject that into muscle cells or skin cells, it uses our own cellular machinery to manufacture those proteins as antigens, and presents them in a customized way. It's like mimicking viral infection without the side effects and replication. DNA vaccines can never replicate. They do not infect; they do not cause disease, ever.”
Delivery Poses Challenges
Until recently, Dr. Kim and other researchers in the field faced a barrier to the advancement of DNA vaccines: inefficient delivery.
However, a technology developed in the 1990s known as in vivo electroporation is proving to be an effective way to deliver DNA vaccines.
Electroporation works like this: After a DNA vaccine is injected into the upper arm or into skin, a short, controlled electrical pulse is delivered into that tissue, either from the same needle or from a surrounding needle. This brief pulse of current “coaxes the cell membranes to open up their pores,” Dr. Kim said. “That brings in the DNA. We remove the electric field and the pores close up. This has been shown in animal species to be effective in up to a 1,000-fold increase in DNA vaccine uptake. The whole procedure takes a couple of seconds.”