作为最重要的鸟类免疫抑制和肿瘤疾病之一,马立克氏病(MD),由致癌马立克氏病病毒(MDV)引起,在过去的五十年中,在全球范围内造成了巨大的经济损失。近年来,在接种MD疫苗的鸡群中经常发生MD疫情,但主要致病因素和影响因素尚不清楚。在这里,我们分析了7株从中国荷瘤鸡中新分离的MDV菌株的致病性,发现它们都对鸡宿主具有致病性,其中四个MDV分离株,SDCW01、HNXZ05、HNSQ05和HNSQ01被认为是高毒力MDV(HV-MDV)株。在病毒感染实验的73天,MD的累积发生率为100%,93.3%,90%和100%,死亡率为83.3%,73.3%,60%和86.7%,分别,四种病毒。肿瘤的总发生率为50%,33.3%,30%和63.3%,分别,伴有明显的肝脾肿大和免疫器官严重萎缩。此外,四种商业MD疫苗对SDCW01、CVI988、HVT、CVI988+HVT,探索了814。出乎意料的是,在病毒后攻击的67天,这四种MD疫苗的保护指数(PI)仅为46.2%,38.5%,50%,28%,分别,接受单价CVI988或HVT的鸟类仍然发展成肿瘤,累积发生率为7.7%和11.5%,分别。据我们所知,这是同时比较不同疫苗株的多种市售MD疫苗的免疫保护效力的首次证明。我们的研究表明,在中国流行的HV-MDV变体可以显着突破目前广泛使用的经典MD疫苗的免疫保护。为了将来的工作,迫切需要发展小说,更有效的MD疫苗,以应对新出现的HV-MDV毒株或变体的新挑战,以可持续控制MD。
As one of the most important avian immunosuppressive and neoplastic diseases, Marek\'s disease (MD), caused by oncogenic Marek\'s disease virus (MDV), has caused huge economic losses worldwide over the past five decades. In recent years, MD outbreaks have occurred frequently in MD-vaccinated chicken flocks, but the key pathogenic determinants and influencing factors remain unclear. Herein, we analyzed the pathogenicity of seven newly isolated MDV strains from tumor-bearing chickens in
China and found that all of them were pathogenic to chicken hosts, among which four MDV isolates, SDCW01, HNXZ05, HNSQ05 and HNSQ01, were considered to be hypervirulent MDV (HV-MDV) strains. At 73 days of the virus infection experiment, the cumulative incidences of MD were 100%, 93.3%, 90% and 100%, with mortalities of 83.3%, 73.3%, 60% and 86.7%, respectively, for the four viruses. The gross occurrences of tumors were 50%, 33.3%, 30% and 63.3%, respectively, accompanied by significant hepatosplenomegaly and serious atrophy of the immune organs. Furthermore, the immune protection effects of four commercial MD vaccines against SDCW01, CVI988, HVT, CVI988+HVT, and 814 were explored. Unexpectedly, during the 67 days of post-virus challenge, the protection indices (PIs) of these four MD vaccines were only 46.2%, 38.5%, 50%, and 28%, respectively, and the birds that received the monovalent CVI988 or HVT still developed tumors with cumulative incidences of 7.7% and 11.5%, respectively. To our knowledge, this is the first demonstration of the simultaneous comparison of the immune protection efficacy of multiple commercial MD vaccines with different vaccine strains. Our study revealed that the HV-MDV variants circulating in
China could significantly break through the immune protection of the classical MD vaccines currently widely used. For future work, there is an urgent need to develop novel, more effective MD vaccines for tackling the new challenge of emerging HV-MDV strains or variants for the sustainable control of MD.