Classical swine fever (CSF) is a highly contagious and economically damaging disease. Classical swine fever virus (CSFV) lapinized vaccine C-strain against CSF worldwide lacks the capacity for the serological differentiation between infected and vaccinated animals (DIVA). To develop a marker C-strain complying with the DIVA principle, we generated and evaluated mutants rHCLV-E2F117A, rHCLV-E2G119A, and rHCLV-E2P122A, which harbor the single amino acid mutation at ¹¹⁷F, ¹¹⁹G or ¹²²P of the monoclonal antibody HQ06-recognized epitope on the E2 glycoprotein in rabbits and pigs. Viral intravenous administration demonstrated that all the mutants retain the phenotype of C-strain in rabbits, including fever response induction and replication in the spleen. Notably, the HQ06-recognized epitope did not react with the antibodies induced by rHCLV-E2P122A in rabbits, in contrast with C-strain and other two mutants. Intramuscular administration of rHCLV-E2P122A in pigs induced anti-CSFV neutralizing antibodies but not antibodies against the HQ06-recognized epitope at 28 days post-inoculation. Collectively, our data demonstrate that rHCLV-E2P122A is a promising marker vaccine candidate against CSF.

古典猪瘟（CSF）是一种具有高度传染性和经济破坏性的疾病。世界范围内针对CSF的经典猪瘟病毒（CSFV）融合疫苗C株缺乏在感染动物和疫苗接种动物（DIVA）之间进行血清学区分的能力。为了开发符合DIVA原理的标记C菌株，我们生成并评估了突变体rHCLV-E2F117A，rHCLV-E2G119A和rHCLV-E2P122A，它们在¹¹⁷ F，¹¹⁹ G或¹²²处具有单个氨基酸突变兔和猪E2糖蛋白上单克隆抗体HQ06识别的表位的P。病毒静脉内给药证明，所有突变体在兔中都保留了C株的表型，包括发烧反应的诱导和在脾脏中的复制。值得注意的是，与C株和其他两个突变体相比，在兔中HQ06识别的表位不与rHCLV-E2P122A诱导的抗体反应。在猪中肌肉注射rHCLV-E2P122A会在接种后28天诱导抗CSFV中和抗体，但不会诱导针对HQ06识别表位的抗体。总体而言，我们的数据表明，rHCLV-E2P122A是针对脑脊液的有前途的标志疫苗候选药物。