Abortions caused by Neospora caninum are a serious problem in cattle production and require effective immunoprophylaxis. The objective of this work was to assess the humoral immune response to four recombinant (r) N. caninum antigens in cattle after immunisation and challenge. MIC1 and MIC3 proteins from the micronemes, SRS2 from the surface of tachyzoites, and GRA7 from the dense granules were expressed as truncated recombinant proteins in Escherichia coli. Cationic liposomes (Lip) and CpG oligodeoxynucleotides (CpG-ODNs) were used as adjuvant. Steers were assigned to three groups of six steers each and were inoculated twice subcutaneously, 21 days apart. The rP + Lip + CpG-ODN group received the truncated recombinant proteins rMIC1, rMIC3, rSRS2 and rGRA7 formulated with the adjuvant; the Lip + CpG-ODN group received the adjuvant alone; and the PBS group received sterile phosphate-buffered saline. All steers were subcutaneously challenged with the NC-1 strain of N. caninum 35 days after the second dose of immunisation. Steers from the rP + Lip + CpG-ODN group developed specific IgG, IgG1 and IgG2 against the four recombinant proteins after immunisation. After challenge, IgG against rMIC1 and rMIC3 was detected in rP + Lip + CpG-ODN group and against rSRS2 and rGRA7 in all groups. IgG1 and IgG2 against the four recombinant proteins remained high after challenge in the rP + Lip + CpG-ODN group. Indirect ELISA detected anti-N. caninum antibodies after challenge in all groups, with the highest level of antibodies being detected in the rP + Lip + CpG-ODN group. The recombinant vaccine formulated with rMIC1, rMIC3, rSRS2 and rGRA7 using Lip + CpG-ODN as adjuvant was immunogenic in cattle and the humoral immune response after challenge was enhanced in vaccinated cattle.

犬新孢子虫引起的流产是牛生产中的一个严重问题，需要有效的免疫预防。这项工作的目的是评估牛在免疫和攻击后对四种重组（r）犬新孢子虫抗原的体液免疫反应。来自微线体的 MIC1 和 MIC3 蛋白、来自速殖子表面的 SRS2 和来自致密颗粒的 GRA7 在大肠杆菌中表达为截短的重组蛋白。使用阳离子脂质体（Lip）和CpG寡脱氧核苷酸（CpG-ODN）作为佐剂。将公牛分为三组，每组 6 头，皮下接种两次，间隔 21 天。 rP+Lip+CpG-ODN组接受佐剂配制的截短重组蛋白rMIC1、rMIC3、rSRS2和rGRA7； Lip+CpG-ODN组仅接受佐剂； PBS组给予无菌磷酸盐缓冲盐水。在第二次免疫接种后 35 天，所有阉牛都用犬新孢子虫 NC-1 菌株进行皮下攻击。 rP + Lip + CpG-ODN 组的牛在免疫后针对四种重组蛋白产生了特异性 IgG、IgG1 和 IgG2。攻击后，rP + Lip + CpG-ODN 组中检测到针对 rMIC1 和 rMIC3 的 IgG，所有组中均检测到针对 rSRS2 和 rGRA7 的 IgG。 rP + Lip + CpG-ODN 组攻击后，针对四种重组蛋白的 IgG1 和 IgG2 仍然很高。间接ELISA在所有组中攻击后均检测到抗犬新孢子虫抗体，其中在rP+Lip+CpG-ODN组中检测到最高水平的抗体。 以Lip+CpG-ODN为佐剂，以rMIC1、rMIC3、rSRS2和rGRA7配制的重组疫苗在牛体内具有免疫原性，并且接种牛体内攻毒后的体液免疫反应增强。