A new DNA vaccine can be pumped unprecedented amounts of influenza proteins in the blood of mice, making them resistant to influenza virus . The experimental vaccine, described in the next month of Nature Biotechnology , could lead to a vaccine against human influenza that uses up to 1000 times less DNA than current experimental vaccines. Experts say it improves the chances that the vaccine would gain Food and Drug Administration (FDA) for use in people.
Many researchers and health officials fear that the foreign DNA in a vaccine could slip into human chromosomes and interfere with their function. To minimize the amount of DNA in a vaccine against influenza, researchers at the Karolinska Institute in Stockholm, Sweden, have turned to an alphavirus called Semliki Forest virus (SFV). After entering a cell, most viruses produce mRNAs encoding the proteins. SFV, however, jazzed this process with both coding for proteins and churning new copies of mRNA, which significantly accelerates the production of proteins. Instead of using the virus itself, the team created DNA segments corresponding to RNA regions SFV that dictate how the virus replicates. To this DNA, they nailed to a gene that encodes the influenza antigen.
In laboratory experiments with hamster cells, the DNA vaccine created mRNA that both copied as it would in the alphavirus and antigen product. When researchers injected vaccine in mice, levels of antibodies and immune system cells, lymphocytes were up to 1000 fold higher than in mice that received the vector vaccine. They found that the vaccine based on alphavirus confers immunity against influenza comparable to that of a DNA vaccine vector, but requires up to 1000 times less DNA. Another advantage is that self-destructs DNA vaccine in about a week, further reducing the chances that he can infiltrate the chromosomes.
But it is still unknown whether the DNA will integrate into the chromosomes, said John Polo, a molecular biologist at Chiron Technologies Center for Gene Therapy in San Diego, California, which is developing similar vaccines for HIV and herpes virus. sharply cut levels of DNA in a vaccine, he says, "can give you a strong advantage" to avoid integration.
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