Immunogenicity of Calvenza-03 EIV/EHV® Vaccine in Horses: Comparative In Vivo Study

Abstract

Equine influenza (EI) is a highly contagious acute respiratory disease of equines that is caused mainly by the H3N8 subtype of influenza A virus. Vaccinating horses against EI is the most effective strategy to prevent the infection. The current study aimed to compare the kinetics of EI-specific humoral- and cell-mediated immunity (CMI) in horses receiving either identical or mixed vaccinations. Two groups of horses were previously (six months prior) vaccinated with either Calvenza 03 EIV EHV® (G1) or Fluvac Innovator® (G2) vaccine. Subsequently, both groups received a booster single dose of Calvenza 03 EIV EHV®. Immune responses were assessed after 10 weeks using single radial hemolysis (SRH), virus neutralization (VN), and EliSpot assays. Our results revealed that Calvenza-03 EIV/EHV®-immunized horses had significantly higher protective EI-specific SRH antibodies and VN antibodies. Booster immunization with Calvenza-03 EIV/EHV® vaccine significantly stimulated cell-mediated immune response as evidenced by significant increase in interferon-γ-secreting peripheral blood mononuclear cells. In conclusion, Calvenza-03 EIV/EHV® vaccine can be safely and effectively used for booster immunization to elicit optimal long persisting humoral and CMI responses even if the horses were previously immunized with a heterogeneous vaccine.

Equine Influenza Virus and Vaccines

“…Inactivated whole virus EI vaccines have been reported to elicit immune responses to both the antigenically variable regions on the viral surface glycoproteins (HA and NA) as well as the more conserved viral proteins such as the NP and M1 matrix protein, believed to induce some level of cross-protection [ 99 , 123 ]. More recently, Pavulraj and coworkers demonstrated that immunization of horses with Calvenza-03 EIV/EHV ® , an inactivated EI vaccine containing Carbimmune ® as an adjuvant, effectively stimulates protective EIV-specific humoral and CMI responses in vaccinated horses [ 124 ]. Specifically, the authors showed that a booster immunization of horses with Calvenza-03 EIV/EHV ® maintained protective antibodies as measured by single radial hemolysis (SRH) for 6 months in vaccinates that received homologous first vaccine dose and 10 weeks when horses received a heterologous first vaccine dose.…”

Understanding the Divergent Evolution and Epidemiology of H3N8 Influenza Viruses in Dogs and Horses

“…Divergence occurred roughly after the appearance of Kentucky/5/2002, California/8560/2002, and Newmarket/5/2003 preC (Figure 1), so that the first full-genome samples from the FC2, FC1 and CIV clades are Richmond/1/2007, Wisconsin/1/2003, ca/Florida/242/2003, respectively. These FC2 and FC1 sequences are currently (or closely match) the EIV formulations frequently manufactured and used for vaccination (29).…”

“…It is unclear to what degree low vaccine effectiveness or antigenic mismatch have contributed to recently observed 'breakthrough' outbreaks (20,(24)(25)(26)(27). Recommendations for vaccine formulations are regularly proposed by the World Organization for Animal Health (formerly Office International des Epizooties, OIE) expert surveillance panel (28), but strain inclusion varies in different vaccine formulations (29). The potential for horses to be sources of zoonotic disease given their close association with humans makes EIV an identified neglected disease threat of concern (30,31).…”

Expression of recombinant Florida clade 2 hemagglutinin in baculovirus expression system: A step for subunit vaccine development against H3N8 equine influenza virus

“…Various commercial vaccines and vaccine candidates were developed to control EI in equines including modified live vaccines (MLVs) ( Townsend et al ., 2001 , Youngner et al ., 2001 , Tabynov et al ., 2014 ), whole inactivated vaccines ( Paillot et al ., 2013 , Pavulraj et al ., 2021 ), subunit ( Paillot and Prowse, 2012 ), DNA vaccines ( Soboll et al ., 2003 , Landolt et al ., 2010 ) these antibody responses differ substantially in that particle mediated DNA vaccination does not induce an immunoglobulin A (IgA, recombinant canarypox vector vaccines ( Toulemonde et al ., 2005 ; Paillot et al ., 2006 ), recombinant equine herpesvirus vaccine ( Van de Walle et al ., 2010 ), and reverse genetics-based vaccines ( Ohta et al ., 2021 , 2022 ). The majority of commercially available vaccines in Egypt do not include representatives of FC2 strains.…”