Abstract
Avian influenza virus (H5N1) has caused serious infections in human beings. This virus has the potential to emerge as a pandemic threat in humans. Effective vaccines against H5N1 virus are needed. A recombinant Bombyx mori baculovirus, Bmg64HA, was constructed for the expression of HA protein of H5N1 influenza virus displaying on the viral envelope surface. The HA protein accounted for approximately 3% of the total viral proteins in silkworm pupae infected with the recombinant virus. Using a series of separation and purification methods, pure Bmgp64HA virus was isolated from these silkworm pupae bioreactors. Aluminum hydroxide adjuvant was used for an H5N1 influenza vaccine. Immunization with this vaccine at doses of 2 mg/kg and 0.67 mg/kg was carried out to induce the production of neutralizing antibodies, which protected monkeys against influenza virus infection. At these doses, the vaccine induced 1:40 antibody titers in 50% and 67% of the monkeys, respectively. The results of safety evaluation indicated that the vaccine did not cause any toxicity at the dosage as large as 3.2 mg/kg in cynomolgus monkeys and 1.6 mg/kg in mice. The results of dose safety evaluation of vaccine indicated that the safe dose of the vaccine were higher than 0.375 mg/kg in rats and 3.2 mg/kg in cynomolgus monkeys. Our work showed the vaccine may be a candidate for a highly effective, cheap, and safe influenza vaccine for use in humans.
Highlights
During the period of May through December of 1997, an outbreak of human influenza A (H5N1) infection in the Hong Kong of China gave the serious cause for concern [1]
There are several practical and scientific challenges to the development of H5N1 vaccines [7]. These include the high pathogenicity of wild-type H5N1 influenza viruses, reduced yields of candidate vaccine viruses in the embryos of fertilized hen’s eggs compared to yields of human influenza viruses, limited manufacturing capacity, and poor immunogenicity of H5 HA
That include inactivated viral vaccines based on H5N1 viruses isolated in 2004 [9,10] and a recombinant H5 HA subunit vaccine based on the H5N1 virus HA gene isolated in 1997, expressed in a baculovirus vector [11]
Summary
During the period of May through December of 1997, an outbreak of human influenza A (H5N1) infection in the Hong Kong of China gave the serious cause for concern [1]. There are several practical and scientific challenges to the development of H5N1 vaccines [7] These include the high pathogenicity of wild-type H5N1 influenza viruses, reduced yields of candidate vaccine viruses in the embryos of fertilized hen’s eggs compared to yields of human influenza viruses, limited manufacturing capacity, and poor immunogenicity of H5 HA. Despite these obstacles, several approaches have been used to generate candidate vaccines and a few have advanced to clinical trials [8]. A single dose of the vaccine containing 30 mg of H5 antigen, induced seroconversions, as determined by haemagglutinin inhibition, in 18 (90%) of 20 recipients [15]
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