This study evaluated the immunomodulatory effect of quercetin on improving cross protection of porcine reproductive and respiratory syndrome virus-1 (PRRSV-1) modified-live virus (MLV) vaccine against highly pathogenic (HP)-PRRSV-2 challenge. Ex vivo experiments demonstrated that quercetin significantly enhanced type I interferon-regulated genes (IRGs) and type I and II interferon (IFN), and significantly decreased pro- and anti-inflammatory cytokine expressions in HP-PRRSV-inoculated monocyte-derived macrophages. In vivo experiments divided pigs (4-week-old; n = 24) into four groups of six pigs. Group 1 and group 2 were immunized with PRRSV-1 MLV vaccine at 0 dpv (day post vaccination). Group 2 also received oral administration of quercetin at 0–49 dpv. Group 3 was injected with PRRSV-1 MLV vaccine solvent at 0 dpv. Group 4 served as strict control. Group 1–3 were challenged intranasally with HP-PRRSV at 28 dpv and immune and clinical parameters were monitored weekly until 49 dpv. Group 1 demonstrated significantly reduced HP-PRRSV viremia, rectal temperature and clinical scores, and significantly improved average daily weight gain (ADWG), compared to group 3. Group 2 demonstrated significantly increased IFN regulatory factor 3, stimulator of IFN genes, IFNα, and significantly decreased transforming growth factor beta (TGFβ) mRNA expressions, compared to group 1. The animals demonstrated significantly reduced HP-PRRSV viremia, but did not demonstrate any further improved PRRSV-specific antibody responses, rectal temperature, clinical scores, and ADWG as compared to group 1. Our findings suggest that quercetin up-regulates IRGs, IFNα, and down-regulates TGFβ mRNA expressions which may contribute to further reducing number of viremic pigs and HP-PRRSV viremia which were conferred by PRRSV-1 MLV vaccine. Our findings also suggest that quercetin may serve as an effective oral immunomodulator for improving cell-mediated immune defense to HP-PRRSV.

这项研究评估了槲皮素对改善猪繁殖与呼吸综合症病毒1（PRRSV-1）改良活病毒（MLV）疫苗对高致病性（HP）-PRRSV-2攻击的交叉保护的免疫调节作用。体内实验表明槲皮素显着增强了I型干扰素调节基因（IRG）和I型和II型干扰素（IFN），并显着降低了HP-PRRSV接种的单核细胞衍生巨噬细胞中促炎和抗炎细胞因子的表达。体内实验将猪（4周龄； n = 24）分为四组，每组六只。第1组和第2组在0 dpv（接种后第2天）用PRRSV-1 MLV疫苗免疫。第2组也以0-49 dpv口服槲皮素。第3组以0 dpv注射PRRSV-1 MLV疫苗溶剂。第4组严格控制。1-3组在28 dpv时用HP-PRRSV鼻内攻击，并每周监测免疫和临床指标直至49 dpv。与第3组相比，第1组证明了HP-PRRSV病毒血症，直肠温度和临床评分的显着降低，并且平均每日体重增加（ADWG）显着提高。第2组证明了IFN调节因子3，IFN基因的刺激物，IFNα和与第1组相比，转化生长因子β（TGFβ）mRNA表达显着降低。与之相比，动物表现出HP-PRRSV病毒血症显着降低，但与PRRSV特异性抗体反应，直肠温度，临床评分和ADWG相比，没有进一步改善第一组。我们的发现表明槲皮素上调IRGs，IFNα，并下调TGFβmRNA表达，这可能有助于进一步减少PRRSV-1 MLV疫苗所致的病毒猪和HP-PRRSV病毒血症的数量。我们的研究结果还表明，槲皮素可作为有效的口服免疫调节剂，用于改善细胞介导的针对HP-PRRSV的免疫防御。