Background: Despite routine vaccination, equine influenza outbreaks occur due to disparities of virus strains between vaccine and field, and immunity gaps between vaccinations.
Objectives: To evaluate whether a combination of adjuvants can enhance immune responses to equine influenza virus (EIV) vaccines.
Study design: In vivo experimental study.
Methods: Eight mixed-breed horses were immunised intramuscularly with a recombinant canarypox-based EIV vaccine, either alone or in combination with monophosphoryl lipid A (MPL) and polyinosinic-polycytidylic acid (poly I:C). A single vaccine dose was administered, and serum samples were collected before immunisation and at 2, 8, and 24 weeks post-immunisation to assess the humoral immune response. Peripheral blood mononuclear cells (PBMCs) were isolated to evaluate immunomodulatory cytokine expression and characterise recall cellular immune responses. Additionally, bone marrow and lymph node cells were analysed to assess memory cell responses.
Results: The combination of MPL and poly I:C significantly enhanced serum IgG antibody concentrations and haemagglutination inhibition (HI) titres against H3N8 A/equine/Kyonggi/SA01/2011 (Florida sub-lineage clade 1) and maintained these for up to 24 weeks post-immunisation. This combination led to increased cytokine mRNA expression and interferon-gamma (IFN-γ) responses in PBMCs. Enhanced memory B cell responses were also observed in the 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.
Main limitations: A viral challenge experiment was not included.
Conclusions: The use of MPL and poly I:C as adjuvants in EIV vaccines significantly improved immune responses by enhancing humoral immunity, memory cell responses, and antigen-specific cellular immunity.
背景:马流感(Equine influenza，EI)是一种由甲型流感病毒H3N8亚型引起的高度传染性呼吸系统疾病。尽管进行常规疫苗接种，但由于疫苗株与野外毒株之间的差异，以及疫苗接种间的免疫空窗期，马流感(EI)仍有爆发的风险。 目的:评估佐剂组合能否增强马流感病毒(EIV)疫苗的免疫反应。 研究设计:体内实验研究。 方法:8匹混种马通过肌肉注射免疫重组金丝雀痘病毒载体的EIV疫苗，接种方式为单独接种疫苗或与单磷酰脂A(MPL)和聚肌胞酸(poly I:C)联合使用。疫苗接种仅进行一次，血清样本在接种前、以及接种后第2、8和24周采集，用于评估体液免疫反应。从外周血分离的单核细胞(Peripheral blood mononuclear cells， PBMCs)中检测免疫调节细胞因子表达并评估细胞免疫记忆反应。此外，本研究还采样骨髓和淋巴结细胞以评估记忆细胞反应。 结果:MPL与poly I:C的组合显著增强了针对H3N8 A/equine/Kyonggi/SA01/2011(佛罗里达支系1型分支)的血清IgG抗体水平和血凝抑制(HI)滴度，并在接种后维持该水平长达24周。此外，该佐剂组合还提高了PBMC细胞因子mRNA的表达和γ干扰素(IFN‐γ)的反应。在免疫后第8周时，在骨髓和淋巴结中也观察到了增强的记忆B细胞反应。而且，在体外使用H3N8 EIV再刺激后，该佐剂组合诱导了更高频率的CD4⁺和CD8⁺ T细胞反应。 主要局限:本研究未进行攻毒实验。 结论:使用MPL和poly I:C作为EIV疫苗的佐剂可通过提升体液免疫、记忆细胞反应及抗原特异性细胞免疫，从而显著提高整体免疫反应。.
Keywords: cytokines; equine influenza virus; horse; immune response; monophosphoryl lipid A; polyinosinic‐polycytidylic acid; vaccine.
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