Sialivac: an intranasal homologous inactivated split virus vaccine containing bacterial sialidase for the control of avian influenza in poultry.

A simple, effective inactivated avian flu vaccine composed of three homologous highly pathogenic (HP) H5N1 strains combined with Clostridium perfringens type A 107 sialidase/neuramindase and chitosan as a trans epithelial carrier adjuvant applied intranasally to poultry is described. Poultry were vaccinated with an inactivated, solvent split, chitosan adjuvanted intranasal (IN) vaccine with and without C. perfringens sialidase and the resulting serum IgG antibody measured by haemagglutination inhibition (HI) and mucosal IgA by ELISA. The clinical effectiveness was demonstrated by disease intervention field trials, where the ability of an intranasal vaccine containing three homologous inactivated solvent split HP H5N1 strains, C. perfringens sialidase and chitosan was successful in controlling the disease in intensively reared commercial chickens. Evidence is presented by demonstrating effective intervention with IN vaccine during outbreaks in poultry previously vaccinated with commercial heterologous H5N2 intramuscular (IM) vaccine and reassorted H5N1 Re-1 vaccine which had failed to protect intensively reared birds. Intervention with the IN vaccine in such flocks completely halted the infection within 2-5 days. Survivors ceased to excrete live virus. Stimulation of the common mucosal immune system (CMIS) and the early production of secretory IgA and subsequently humoral IgG demonstrated by laboratory controlled experiments and field studies revealed the ability of intranasally vaccinated birds to resist lethal virus challenge. A strategy of mucosal immunisation is recommended to reduce the incidence of disease in intensively reared poultry and thus minimise the generation and transfer of mutated highly pathogenic subtypes to humans and other animals.