Expression Dynamics of Innate Immunity in Influenza Virus-Infected Swine.
Authors: Montoya María, Foni Emanuela, Solórzano Alicia, Razzuoli Elisabetta, Baratelli Massimiliano, Bilato Dania, Córdoba Lorena, Del Burgo Maria Angeles Martín, Martinez Jorge, Martinez-Orellana Pamela, Chiapponi Chiara, Perlin David S, Del Real Gustavo, Amadori Massimo
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Innate Immune Response to Cross-Species Influenza Strains in Pigs Different influenza virus strains demonstrate markedly variable pathogenicity in pigs depending on their host origin, with swine-adapted H3N2 causing significant pulmonary lesions and viral replication, whilst equine and canine H3N8 strains produced minimal clinical signs despite triggering measurable immune responses. Using infected pigs necropsied at 3, 6, and 21 days post-inoculation, researchers tracked innate immunity markers including interferon-alpha, interleukin-6, and serum amyloid A across bronchoalveolar fluid and serum samples across five virus strains. The swine-adapted virus provoked robust early interferon-alpha responses in respiratory secretions by day 3, though this did not correlate with increased local gene expression, whilst surprisingly the equine strain elicited serum amyloid A production in lung fluid despite minimal viral replication—suggesting cross-species strains trigger distinct immune signatures independent of infectious titre. Critically, cytokine gene and protein expression persisted well beyond active viral replication in all groups, indicating prolonged innate immune dysregulation that may contribute to secondary complications or extended recovery periods. These findings suggest that whilst equine and canine influenza strains pose limited direct pathogenic risk to pigs, their capacity to stimulate atypical immune responses warrants consideration when assessing zoonotic or interspecies transmission risks in mixed-species facilities.
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Practical Takeaways
- •Equine influenza virus can cross the species barrier to infect pigs but causes minimal clinical disease, raising questions about equine-to-swine transmission risk and the potential for asymptomatic shedding
- •Different influenza strains trigger distinct innate immune profiles; cross-species strains may cause prolonged immune dysregulation even with low active replication, complicating diagnosis and recovery assessment
- •Understanding that some zoonotic influenza strains (avian, seal) can replicate in swine with moderate lesions suggests pig farms may serve as mixing vessels for pandemic influenza strain development
Key Findings
- •Swine-adapted H3N2 influenza induced high viral replication and pulmonary lesions with robust IFN-alpha and IL-6 responses in bronchoalveolar fluid at day 3 post-infection
- •Avian and seal H3N8 strains caused moderate pulmonary lesions and viral replication, while equine and canine H3N8 strains produced minimal pathological signs and barely detectable replication
- •Equine H3N8 strain triggered serum amyloid A response despite minimal viral replication, suggesting innate immune activation independent of active infection
- •All non-swine-adapted virus strains induced prolonged cytokine gene expression extending well beyond the period of active viral replication