Bird Flu Vaccine
Immediately after the outbreak in 1997-1999 people started the search for a vaccine against avian flu virus.
Mice were used as a model of the immune system in mammals for the study of lethal avian influenza infection. Production of a vaccine against the H5N1 influenza virus in the chicken embryo is impossible because of the death of chicken embryos during infection with this virus and high levels of biosafety required to work with the virus and production of vaccines based on the virus.
To develop a vaccine based on whole virus used avirulent virus H5N4, isolated from migratory ducks, H5N1 and avirulent recombinant virus H5N1. The introduction of the vaccine prepared on the basis of non-pathogenic strain A/Duck/Singapore-Q/F119-3/97 (H5N3), antigenically related human virus, H5N1, in combination with alum or without them, resulting in complete protection against lethal control of infection with the H5N1 virus.
Protection against infection was observed in 70% of the animals when the vaccine was administered alone and in 100% of the animals when the vaccine was administered in combination with alum. The protective effect of vaccination correlated with the levels of virus-specific serum antibodies. These results suggest that in the event of a pandemic may use antigenically related, but not pathogenic influenza viruses as candidates for the vaccine.
Studies of DNA vaccines demonstrated that DNA vaccine encoding the hemagglutinin from A/Ty/Ir/1/83 (H5N8), which differs from A/HK/156/97 (H5N1) within 12% in HA1, prevents death of mice, but no disease when infected with H5N1. Hence, the DNA vaccine, made on the basis of a heterologous H5 strain did not protect mice from infection with avian influenza virus H5N1, but is useful in protecting mice from death.
Results of the study confirmed the usefulness of vaccination immunity, which stimulates cross-protection against a variety of viral subtypes, including viruses, presenting a potential pandemic threat.