On the other hand, most of the mice immunized with the adenovirus containing the HA protein showed only mild weight loss and survived H5N1 infection. It was also found that full length HA vaccine gave a complete protection against the H5N1 strain.
The mice which is immunized with full-length HA vaccine developed strong T-cell responses. Hence this recombinant vaccine offers a greater therapeutic value. Even if H5N1 mutates, the vaccine is still offers protection against the disease.
Based on the superior degree of protection that they found in mice vaccinated with full-length HA vaccine, Dr. Gambotto's group along with David E. Swayne, D.V.M., Ph.D., at the U.S. Department of Agriculture, tested the vaccine’s effectiveness in chickens. Chickens were injected with the vaccine and the empty vector both intranasally and subcutaneously. The chickens were then challenged with a dose of whole H5N1 virus 10,000 times greater than the dose given to the mice.
It was found that all of the chickens that were immunized subcutaneously survived exposure to H5N1 and developed strong HA-specific antibody responses and showed no clinical signs of disease. On the other hand 50% of those that were immunized intranasally died. All of the chickens immunized with the empty vector (intranasally and subcutaneously) died within two days of H5N1 exposure.
Dr. Gambotto and his colleagues suggest that these live vaccines can be used in combination with the traditional inactivated influenza vaccines.
Hence the research team concludes by saying that the new vaccine would have the ability to contain outbreaks of mutant strains. Further trails in the humans have to be conducted in order to understand the efficiency of the vaccine in humans.
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