How to Meet the Last OIE Expert Surveillance Panel Recommendations on Equine Influenza (EI) Vaccine Composition: A Review of the Process Required for the Recombinant Canarypox-Based EI Vaccine

Abstract

Vaccination is highly effective to prevent, control, and limit the impact of equine influenza (EI), a major respiratory disease of horses. However, EI vaccines should contain relevant equine influenza virus (EIV) strains for optimal protection. The OIE expert surveillance panel annually reviews EIV evolution and, since 2010, the use of Florida clade 1 and 2 sub-lineages representative vaccine strains is recommended. This report summarises the development process of a fully- updated recombinant canarypox-based EI vaccine in order to meet the last OIE recommendations, including the vaccine mode of action, production steps and schedule. The EI vaccine ProteqFlu contains 2 recombinant canarypox viruses expressing the haemagglutinin of the A/equine/Ohio/03 and A/equine/Richmond/1/07 isolates (Florida clade 1 and 2 sub-lineages, respectively). The updated EI vaccine was tested for efficacy against the representative Florida clade 2 EIV strain A/equine/Richmond/1/07 in the Welsh mountain pony model. Protective antibody response, clinical signs of disease and virus shedding were compared with unvaccinated control ponies. Significant protection was measured in vaccinated ponies, which supports the vaccine registration. The recombinant canarypox-based EI vaccine was the first fully updated EI vaccine available in the EU, which will help to minimise the increasing risk of vaccine breakdown due to constant EIV evolution through antigenic drift.

The Immunity Gap Challenge: Protection against a Recent Florida Clade 2 Equine Influenza Strain

“…However, heterogeneity between vaccine and challenge strains was limited in these studies. Despite the significant time between V2 and the experimental infection (i.e., 158 days), the clinical outcome measured in the vaccinated group in the present study was similar to the outcome measured in ponies vaccinated with (1) an EI vaccine based on a canarypox-vectored vaccine expressing the haemagglutinin gene of EIV and experimentally infected with EIV 14 days after the second immunisation [ 35 ] and (2) a whole inactivated EI vaccine as well as experimental infection with EIV 14 or 15 days after V2 [ 12 , 26 ]. The clinical protection achieved in the current study was also similar or superior to the one recorded in ponies vaccinated with an ISCOM-based EI vaccine and experimentally infected with EIV 14 days [ 25 ] or 78 days after V2 [ 14 ], respectively.…”

“…While it has not been demonstrated experimentally, sterilising immunity may also occur at peaks of immunity induced by subsequent boost immunisations (V3, V4, etc.) [ 35 ]. It is important to note that the infectious dose was delivered by individual nebulisation, which significantly increases the amount of virus inhaled by ponies when compared with the historical room nebulisation procedure previously used in numerous EI vaccine studies.…”

Success and Limitation of Equine Influenza Vaccination: The First Incursion in a Decade of a Florida Clade 1 Equine Influenza Virus that Shakes Protection Despite High Vaccine Coverage

“…For the few cases where serum were obtained at the onset of disease, it appears that infection could be explained in half of the cases by a lower than expected SRH antibody titer at the time of contact with EIV (irrespective of the time since last immunization). With the exception of horse #6, which had an SRH antibody titer above the 154 mm 2 threshold, other vaccinated horses had average titers (between 93 and 129 mm 2 ), probably high enough to significantly reduce the clinical signs of disease but insufficient to induce sterilizing immunity, which is rarely measured [35], even in optimal study conditions.…”

Вакцины Против Гриппа Лошадей

“…Вакцина ProteqFlu ® («Merial Ltd.», Франция) -единственная живая рекомбинантная векторная вакцина против гриппа лошадей, которая применяется в практическом коневодстве с 2003 года (33). В качестве вектора для экспрессии генов НА вирусов гриппа лошадей A/equine/Ohio/03 (H3N8) и A/equine/Richmond/1/07 (H3N8) в этой вакцине используется рекомбинантный вирус оспы канареек (Сanarypox, ALVAC) (54,55). Вак-цина безопасна, поскольку рекомбинантный вирус оспы канареек вызывает абортивную инфекцию в клетках млекопитающих (56).…”