Adjuvant combination enhances immune response of equine influenza virus vaccine in horses.
Authors: Dong-Ha Lee, Eun-Bee Lee, Jong-Pil Seo, Eun-Ju Ko
Journal: Equine veterinary journal
Summary
# Editorial Summary: Adjuvant Combination Enhances Immune Response of Equine Influenza Virus Vaccine in Horses Despite routine vaccination programmes, equine influenza continues to cause outbreaks due to strain mismatch between vaccine and field viruses, alongside immunity waning between vaccination intervals—a persistent challenge in equine preventive medicine. Lee and colleagues investigated whether combining two immunological adjuvants, monophosphoryl lipid A (MPL) and polyinosinic-polycytidylic acid (poly I:C), could augment the immune response to a recombinant canarypox-based EIV vaccine in eight mixed-breed horses receiving a single intramuscular dose. The adjuvant combination significantly elevated serum IgG antibody concentrations and haemagglutination inhibition titres against H3N8 (Florida sub-lineage clade 1), maintaining protective levels for up to 24 weeks, whilst also driving enhanced interferon-gamma responses and increased frequencies of both CD4+ and CD8+ T cells following antigen restimulation; memory B cell responses were notably strengthened in bone marrow and lymph node samples at 8 weeks post-vaccination. Whilst the study design lacked a viral challenge phase to confirm clinical protection, the findings suggest that MPL and poly I:C adjuvants merit evaluation as a practical strategy to improve vaccine efficacy and potentially extend immunity intervals between boosters—particularly valuable for equine operations managing vaccination schedules and disease risk in populations exposed to circulating EIV strains.
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Practical Takeaways
- •Adding MPL and poly I:C adjuvants to equine influenza vaccines significantly improves immune response durability and strength, potentially reducing outbreak risk between vaccination intervals
- •The enhanced cellular and humoral immunity suggests adjuvanted vaccines may provide better protection against field strains that differ from vaccine strains
- •This approach could reduce immunity gaps between routine vaccinations, though viral challenge studies are still needed to confirm clinical efficacy in natural infection scenarios
Key Findings
- •MPL and poly I:C adjuvant combination significantly enhanced serum IgG antibody concentrations and hemagglutination inhibition (HI) titres against H3N8 EIV and maintained them for up to 24 weeks post-immunisation
- •The adjuvant combination increased cytokine mRNA expression and interferon-gamma (IFN-γ) responses in peripheral blood mononuclear cells (PBMCs)
- •Enhanced memory B cell responses were observed in bone marrow and lymph nodes at 8 weeks post-immunisation
- •MPL and poly I:C induced higher frequencies of CD4+ and CD8+ T cells following in vitro restimulation with H3N8 EIV