ScienceDaily (Aug. 24, 2007) — The integration of an immune-enhancing protein into two new smallpox vaccine candidates elicited superior immune responses, efficacy and safety in mice say researchers from the U.S.

Following the declaration of global eradication of smallpox in 1979, vaccinations for the general public were discontinued. Today, the virus poses threat as an agent of biological warfare, leaving half of the worldwide population susceptible to serious disease or death in the event of an attack. Severe adverse effects resulting from the currently licensed Dryvax vaccine emphasize the need for new preventative methods.

Researchers developed two new vaccine candidates integrating the immune-enhancing protein Interleukin-15 (IL-15) and tested for efficacy in mice challenged with smallpox. Wyeth IL-15 included a strain of the vaccinia virus derived from the Dryvax vaccine and MVA IL-15 incorporated a modified strain of the vaccinia virus Ankara which is currently being considered as a substitute for the Dryvax vaccine. The Wyeth IL-15 vaccine resulted in a 1,000-fold reduction in lethality and highly increased cellular and humoral immune responses. Additionally, mice vaccinated with Wyeth IL-15 fully survived a lethal intranasal challenge ten months after vaccination. The second candidate MVA IL-15 also demonstrated greater immunogenicity and efficacy than Dryvax.

“By integrating IL-15 cytokine into Wyeth and MVA strains, we have developed two smallpox vaccine candidates with greater immunogenicity and efficacy yet with more-attenuated virulence than the currently licensed Dryvax vaccine suitable for contemporary populations,” say the researchers.

These findings are reported in the August 2007 issue of the Journal of Virology.

Reference: L.P. Perera, T.A. Waldmann, J.D. Mosca, N. Baldwin, J.A. Berzofsky, S.K. Oh. 2007. Development of smallpox vaccine candidates with integrated interleukin-15 that demonstrate superior immunogenicity, efficacy, and safety in mice. Journal of Virology, 81. 16: 8774-8783).

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