Efficacy of a canarypox-vectored recombinant vaccine expressing the hemagglutinin gene of equine influenza H3N8 virus in the protection of ponies from viral challenge.

OBJECTIVE: To determine onset and duration of immunity provided by a 2- or 3-dose series of a new canarypox-vectored recombinant vaccine for equine influenza virus (rCP-EIV vaccine) expressing the hemagglutinin genes of influenza H3N8 virus strains A/eq/Kentucky/94 and A/eq/Newmarket/2/93 in ponies. ANIMALS: Forty-nine 1- to 3-year-old male Welsh Mountain Ponies that were seronegative for equine influenza virus. PROCEDURES: Vaccinated and control ponies were challenged with aerosolized influenza virus A/eq/Sussex/89 (H3N8), representative of the Eurasian lineage of circulating influenza viruses. In trial 1, control ponies and ponies that received rCP-EIV vaccine were challenged 2 weeks after completion of the 2-dose primary vaccination program. In trial 2, ponies were challenged 5 months after 2 doses of rCP-EIV vaccine or 1 year after the first boosting dose of rCP-EIV vaccine, administered 5 months after completion of the primary vaccination program. After challenge, ponies were observed daily for clinical signs of influenza and nasal swab specimens were taken to monitor virus excretion. RESULTS: The challenge reliably produced severe clinical signs consistent with influenza infection in the control ponies, and virus was shed for up to 7 days. The vaccination protocol provided clinical and virologic protection to vaccinates at 2 weeks and 5 months after completion of the primary vaccination program and at 12 months after the first booster. CONCLUSION AND CLINICAL RELEVANCE: The rCP-EIV vaccine provided protection of ponies to viral challenge. Of particular importance was the protection at 5 months after the second dose, indicating that this vaccine closes an immunity gap between the second and third vaccination.

Comparison of genome segments 2, 7 and 10 of bluetongue viruses serotype 2 for differentiation between field isolates and the vaccine strain.

Bluetongue (BT) virus serotype 2 (BTV 2) was first confirmed in Tunisia in February 2000 and has since spread northward and westward, infecting several other countries and islands, including Corsica, where clinical disease was reported in October 2000. BT was again reported on the Island in July 2001, some six months after a vaccination campaign against BTV 2. The molecular relationship between isolates of the BTV 2 Corsican wild-type viruses from 2000 and 2001, and the attenuated BTV 2 vaccine were determined by comparing corresponding sequences of genome segments 2, 7 and 10 with each other and with already published sequences available in the genome database. Complete genetic stability was observed between the isolates of the Corsican BTV 2. There was some divergence between the nucleotide sequences of segment 10 obtained from the wild-type and vaccine virus strains. Based on these differences, primers were selected that could be used in RT-PCR to differentiate between the wild-type and the vaccine viruses.