Immunization with the biologically active lectin domain of PapGII induces strong adhesion-inhibiting antibody responses but not protection against avian pathogenic Escherichia coli.

The aim of this study was to investigate whether immunization with the sugar binding domain of PapGII (PapGII196) was able to protect chickens against avian pathogenic Escherichia coli. PapGII196 was expressed, purified by Ni-NTA column chromatography and shown to retain its biological activity, as demonstrated by binding to its receptor, globoside. PapGII196 was tested as a vaccine in specific pathogen free broilers and also by vaccinating breeders and assessing protection in their offspring, and using aerosol exposure or air sac inoculation for challenge. Notwithstanding a strong anti-PapGII196 serum IgG response in vaccinated birds in all experiments and inhibition of haemagglutination by serum from PapGII196-vaccinated birds, chickens were not protected against avian pathogenic E. coli. These findings suggest that PapGII may not be a useful candidate for inclusion in vaccines against avian pathogenic E. coli.

Efficacy of a new tetravalent coryza vaccine against emerging variant type B strains.

Outbreaks of infectious coryza have been reported in vaccinated flocks in different countries, indicating that new serotype(s) of Haemophilus paragallinarum may have evolved. Several field isolates from vaccinated flocks in the US, Ecuador, Argentina and Zimbabwe were examined and, apart from one serotype C strain, all were typed as serotype B. An inactivated commercial trivalent vaccine, containing serotypes A, B and C, protected against challenge with the serotype C isolate but protection against challenge with serotype B isolates was weaker, suggesting that they might represent a new variant immunotype. An experimental tetravalent oil adjuvant vaccine, containing one of the serotype B isolates, appeared immunogenic against all isolates after one vaccination. Its efficacy and safety were further tested in layer chickens housed under field conditions. Chickens were vaccinated at 8 and 16 weeks of age while controls were unvaccinated. Vaccinates and controls were challenged with type A, B, C and variant type B at 25, 45 or 65 weeks of age. There was good protection (P<0.05) against all four immunotypes after all challenges. No systemic reactions were observed and local reactions were similar to those found with the commercial trivalent vaccine. The tetravalent vaccine may therefore be a good choice for control of new field isolates.