Research from Sweden suggests that adding the drug tucaresol to plasmid DNA influenza vaccines could offer longer-lasting and more efficient protection against the influenza virus. The findings appear in the October 2004 issue of the Journal of Virology.
Annual flu epidemics continue to pose major health problems worldwide despite yearly vaccination efforts. Studies indicate protection offered by the current vaccine to be short-lived and only capable of targeting specific strains of the virus. Because influenza strains are highly variable, a vaccine with higher efficacy is necessary.
DNA vaccines differ from traditional vaccines in that they are entirely gene-based and are designed to target genes intracellularly. Researchers are actively pursuing Plasmid DNA (pDNA) vaccines as a favorable new form of vaccination as studies show they are quick to generate (days or weeks vs. months or years), are cost effective, and could offer long-term protection against various infectious diseases.
The pDNA vaccine specific to this study contains conserved genes from the flu virus, and although safer due to its lack of live viral strains, has shown to be weaker in inducing immune responses. Tucaresol, a drug that stimulates the immune system, is capable of interacting with molecules on the surface of T cells and was recently noted for its ability to enhance immune responses resulting from pDNA vaccinations.
"Optimally, such a vaccine should be capable of inducing protection against heterologous virus strains and should induce long-lived responses and be highly efficient," say the researchers.
In the study mice challenged with two strains of the influenza virus were immunized with the pDNA vaccine and administered tucaresol. Researchers found that the combination provided enhanced protection, resulting in increased survival in both groups due to elevated immune response.
"Our data suggest a simple and direct modification to enhance gene gun-based pDNA immunization against influenza," say the researchers. "Such a vaccination strategy is predicted to be safe and efficient and would result in long-lasting protection against heterologous strains of the virus."
(J. Charo, J.A. Lindencrona, L.M. Carlson, J. Hinkula, R. Kiessling. 2004. Protective efficacy of a DNA influenza virus vaccine is markedly increased by the coadministration of a Schiff base-forming drug. Journal of Virology, 78. 20: 11321-11326.)