Department of Animal Science, The University of Tennessee, Knoxville, TN, United States.
College of Fisheries, Jimei University, Xiamen, China.
Front Immunol. 2021 Apr 2;12:629480. doi: 10.3389/fimmu.2021.629480. eCollection 2021.
Passive immunization with specific egg yolk antibodies (immunoglobulin Y, IgY) is emerging as a promising alternative to antibiotics to control bacterial infections. Recently, we developed a novel conjugate vaccine that could trigger a strong immune response in rabbits directed against enterobactin (Ent), a highly conserved siderophore molecule utilized by different Gram-negative pathogens. However, induction of Ent-specific antibodies appeared to be affected by the choice of animal host and vaccination regimen. It is still unknown if the Ent conjugate vaccine can trigger a specific immune response in layers for the purpose of production of anti-Ent egg yolk IgY. In this study, three chicken vaccination trials with different regimens were performed to determine conditions for efficient production of anti-Ent egg yolk IgY. Purified Ent was conjugated to three carrier proteins, keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA) and CmeC (a subunit vaccine candidate), respectively. Intramuscular immunization of Barred Rock layers with KLH-Ent conjugate four times induced strong immune response against whole conjugate vaccine but the titer of Ent-specific IgY did not change in yolk with only a 4 fold increase detected in serum. In the second trial, three different Ent conjugate vaccines were evaluated in Rhode Island Red pullets with four subcutaneous injections. The KLH-Ent or CmeC-Ent conjugate consistently induced high level of Ent-specific IgY in both serum (up to 2,048 fold) and yolk (up to 1,024 fold) in each individual chicken. However, the Ent-specific immune response was only temporarily and moderately induced using a BSA-Ent vaccination. In the third trial, ten White Leghorn layers were subcutaneously immunized three times with KLH-Ent, leading to consistent and strong immune response against both whole conjugate and the Ent molecule in each chicken; the mean titer of Ent-specific IgY increased approximately 32 and 256 fold in serum and yolk, respectively. Consistent with its potent binding to various Ent derivatives, the Ent-specific egg yolk IgY also inhibited growth of a representative strain. Together, this study demonstrated that the novel Ent conjugate vaccine could induce strong, specific, and robust immune response in chickens. The Ent-specific hyperimmune egg yolk IgY has potential for passive immune intervention against Gram-negative infections.
被动免疫用特定的卵黄抗体（免疫球蛋白 Y，IgY）正成为抗生素控制细菌感染的一种有前途的替代品。最近，我们开发了一种新型的结合疫苗，能够在兔子中引发针对肠杆菌素（Ent）的强烈免疫反应，肠杆菌素是一种高度保守的铁载体分子，被不同的革兰氏阴性病原体利用。然而，Ent 特异性抗体的诱导似乎受到动物宿主和疫苗方案选择的影响。目前尚不清楚 Ent 结合疫苗是否能在蛋鸡中引发针对 Ent 的特异性免疫反应，从而生产抗 Ent 的卵黄 IgY。在这项研究中，进行了三次不同方案的鸡接种试验，以确定有效生产抗 Ent 卵黄 IgY 的条件。纯化的 Ent 分别与三种载体蛋白（血蓝蛋白（KLH）、牛血清白蛋白（BSA）和 CmeC（亚单位疫苗候选物）偶联。用 KLH-Ent 结合物四次肌肉内免疫斑岩鸡，诱导强烈的针对整个结合疫苗的免疫反应，但卵黄中的 Ent 特异性 IgY 滴度没有变化，仅在血清中检测到 4 倍增加。在第二项试验中，用 4 次皮下注射在罗得岛红鸡中评估了三种不同的 Ent 结合疫苗。KLH-Ent 或 CmeC-Ent 结合物在每个鸡的血清（高达 2048 倍）和卵黄（高达 1024 倍）中始终诱导高水平的 Ent 特异性 IgY。然而，用 BSA-Ent 疫苗接种仅暂时和适度地诱导 Ent 特异性免疫反应。在第三次试验中，10 只白来航鸡用 KLH-Ent 三次皮下免疫，导致每只鸡对整个结合物和 Ent 分子均产生一致和强烈的免疫反应；卵黄中的 Ent 特异性 IgY 的平均滴度分别增加了约 32 和 256 倍。Ent 特异性卵黄 IgY 与其与各种 Ent 衍生物的强烈结合一致，也抑制了代表性菌株的生长。总之，这项研究表明，新型的 Ent 结合疫苗能够在鸡中诱导强烈、特异和强大的免疫反应。Ent 特异性高免卵黄 IgY 有可能对革兰氏阴性感染进行被动免疫干预。
