Pathology of Equine Influenza virus (H3N8) in Murine Model

Abstract

Equine influenza viruses (EIV)—H3N8 continue to circulate in equine population throughout the world. They evolve by the process of antigenic drift that leads to substantial change in the antigenicity of the virus, thereby necessitating substitution of virus strain in the vaccines. This requires frequent testing of the new vaccines in the in vivo system; however, lack of an appropriate laboratory animal challenge model for testing protective efficacy of equine influenza vaccine candidates hinders the screening of new vaccines and other therapeutic approaches. In the present investigation, BALB/c mouse were explored for suitability for conducting pathogenecity studies for EIV. The BALB/c mice were inoculated intranasally @ 2×106.24 EID50 with EIV (H3N8) belonging to Clade 2 of Florida sublineage and monitored for setting up of infection and associated parameters. All mice inoculated with EIV exhibited clinical signs viz. loss in body weights, lethargy, dyspnea, etc, between 3 and 5 days which commensurate with lesions observed in the respiratory tract including rhinitis, tracheitis, bronchitis, bronchiolitis, alveolitis and diffuse interstitial pneumonia. Transmission electron microscopy, immunohistochemistry, virus quantification through titration and qRT-PCR demonstrated active viral infection in the upper and lower respiratory tract. Serology revealed rise in serum lactate dehydrogenase levels along with sero-conversion. The pattern of disease progression, pathological lesions and virus recovery from nasal washings and lungs in the present investigations in mice were comparable to natural and experimental EIV infection in equines. The findings establish BALB/c mice as small animal model for studying EIV (H3N8) infection and will have immense potential for dissecting viral pathogenesis, vaccine efficacy studies, preliminary screening of vaccine candidates and antiviral therapeutics against EIV.

Protective efficacy of inactivated reverse genetics based equine influenza vaccine candidate adjuvanted with Montanide^TM Pet Gel in murine model

“…Earlier studies on various Influenza A viruses viz. H3N8 in BALB/c mice [20,21], H3N2 virus in ferrets [12] and H9N2 in broiler chickens [28] had similar findings.…”

“…Group C animals were not given any treatment and served as unimmunized -uninfected control ( Table 1). The vaccine dosage -15 μg of viral protein in immunodiffusion (SRD) content, total protein content of virus was utilized in the current study [20,21]. Group A mice were immunized with the vaccine formulation -15 μg of viral protein in μl intramuscularly on both the flanks on day 0 of the animal experimentation followed by booster doses -μg of viral protein on day 21 and 35 post immunization.…”

“…Total histopathological score. Grades of 0 to 5 were given for each of the parameters with 0 indicating no pathological change while 5 indicating severe histopathological changes as described in our previous studies [20,21].…”

“…The quality and quantity of the purified RNA was determined by Nanodrop and stored at -80°C for further analysis by qRT-PCR. The qRT-PCR assay was carried out using primers targeting nucleoprotein (NP) gene, TaqMan probe, standards and TaqMan Fast Virus 1-Step Master Mix (Applied Biosystems) for quantification of virus copy numbers [20].…”

Effect of the Selection Pressure of Vaccine Antibodies on Evolution of H9N2 Avian Influenza Virus in Chickens

“…Previous studies have shown that serial passaging of the influenza virus in nonimmunized animals can lead to increased pathogenicity and transmission of the virus (Guarnaccia et al,2013,Li et al,2014,Murcia et al,2012,Pavulraj et al,2015. Moreover, the infectivity of virus serially passaged without selection pressure of vaccine antibodies also increases (Jin et al,2018,Shanmuganatham et al,2016.…”