Pathology of Equine Influenza virus (H3N8) in Murine Model.
Authors: Pavulraj Selvaraj, Bera Bidhan Chandra, Joshi Alok, Anand Taruna, Virmani Meenakshi, Vaid Rajesh Kumar, Shanmugasundaram Karuppusamy, Gulati Baldev Raj, Rajukumar K, Singh Rajendra, Misri Jyoti, Singh Raj Kumar, Tripathi Bhupendra Nath, Virmani Nitin
Journal: PloS one
Summary
# Equine Influenza Virus Pathogenesis in Laboratory Mice: A New Tool for Vaccine Development Equine influenza H3N8 undergoes constant antigenic drift, requiring frequent vaccine updates, yet the absence of a suitable small-animal model has hindered rapid screening of new vaccine candidates and therapeutic interventions. Researchers inoculated BALB/c mice intranasally with H3N8 virus (Clade 2, Florida sublineage) at 2×10⁶·²⁴ EID₅₀ and tracked disease progression, viral load, pathological changes, and immune responses over the infection period. All infected mice developed clinical signs between days 3–5 (weight loss, lethargy, dyspnoea) alongside characteristic respiratory tract lesions ranging from rhinitis through to diffuse interstitial pneumonia; viral replication in upper and lower respiratory tissues was confirmed via transmission electron microscopy, immunohistochemistry, quantitative PCR, and viral titration, with seroconversion and elevated serum lactate dehydrogenase levels mirroring natural equine infection. The disease pattern and pathological findings in mice were directly comparable to experimental and natural EIV infection in horses, establishing BALB/c mice as a validated small-animal model suitable for dissecting viral pathogenesis and conducting preliminary efficacy evaluations of vaccine candidates and antivirals. For equine professionals involved in vaccine protocols and therapeutic development, this model offers a more rapid, cost-effective screening pathway before moving promising interventions into equine field trials, potentially accelerating the response to emerging H3N8 variants.
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Practical Takeaways
- •This research establishes a laboratory model for testing new equine influenza vaccines before equine trials, accelerating development of improved vaccines against evolving virus strains
- •The mouse model demonstrates pathological patterns similar to natural horse infection, validating its use for screening therapeutic interventions and understanding viral pathogenesis
- •New vaccine candidates can be preliminarily evaluated in this cost-effective small animal model, reducing time and resources needed for full equine vaccination trials
Key Findings
- •BALB/c mice inoculated with EIV H3N8 developed clinical signs (weight loss, lethargy, dyspnea) between 3-5 days post-infection with pathological changes in respiratory tract (rhinitis, tracheitis, bronchitis, bronchiolitis, alveolitis, and diffuse interstitial pneumonia)
- •Virus recovery and active infection demonstrated in upper and lower respiratory tract through transmission electron microscopy, immunohistochemistry, virus titration, and qRT-PCR
- •Disease progression pattern, pathological lesions, and virus recovery in mice were comparable to natural and experimental EIV infection in equines
- •BALB/c mice model established as suitable small animal model for vaccine efficacy studies, vaccine candidate screening, and antiviral therapeutic testing against EIV H3N8