U.S. National Poultry Research Center, U.S. Department of Agriculture, Agricultural Research Service, 934 College Station Road, Athens, GA 30605, USA.
J Gen Virol. 2020 May;101(5):542-552. doi: 10.1099/jgv.0.001403. Epub 2020 Mar 5.
Marek's disease virus (MDV), a causative agent of Marek's disease, has evolved its virulence partly because the current control strategies fail to provide sterilizing immunity. 3 (GaHV-3) and turkey herpesvirus have been developed as bivalent vaccines to improve upon the level of protection elicited by single formulations. Since the passage of vaccines can result in attenuation, a GaHV-3 strain 301B/1 was cloned as a bacterial artificial chromosome (BAC) by inserting the -F replicon into the virus genome. A fully infectious virus, v301B-BAC, was reconstituted from the 301B/1 BAC clone and had similar growth kinetics comparable to that of the parental 301B/1 virus with strong reactivity against anti-301B/1 chicken sera. Protective efficacies of v301B-BAC, parental 301B/1, and SB-1 vaccine were evaluated against a very virulent MDV Md5 challenge. Clinical signs were significantly lower in the v301B-BAC vaccinated groups (24-25 %), parental 301B/1 (29 %) compare to that of non-vaccinated control (100%) and the removal of BAC sequences from v301B-BAC genome further reduced this to 17 %. The protective indices of v301B-BACs (75-76 %) were comparable with those of both the 301B/1 and the SB-1 vaccine (71%). Removal of the -F replicon resulted in a reconstituted virus with a protective index of 83 %. The shedding of challenge virus was notably lower in the v301B-BAC, and v301B-delBAC vaccinated groups. Overall, the protective efficacy of the 301B-BAC-derived vaccine virus against a very virulent MDV challenge was comparable to that of the parental 301B/1 virus as well as the SB-1 vaccine virus.
马立克氏病病毒（MDV）是马立克氏病的病原体，其毒力部分是由于当前的控制策略未能提供绝育免疫。3（GaHV-3）和火鸡疱疹病毒已被开发为二价疫苗，以提高单一配方引起的保护水平。由于疫苗的传代可能导致减毒，因此通过将 -F 复制子插入病毒基因组，克隆了 GaHV-3 株 301B/1 作为细菌人工染色体（BAC）。从 301B/1 BAC 克隆中重建了完全传染性病毒 v301B-BAC，其生长动力学与亲本 301B/1 病毒相似，对抗 301B/1 鸡血清具有强烈反应性。针对非常强毒力的 MDV Md5 攻毒，评估了 v301B-BAC、亲本 301B/1 和 SB-1 疫苗的保护效力。临床症状在 v301B-BAC 接种组（24-25%）、亲本 301B/1（29%）中明显低于未接种对照（100%），并且从 v301B-BAC 基因组中去除 BAC 序列进一步将其降低至 17%。v301B-BAC 的保护指数（75-76%）与 301B/1 和 SB-1 疫苗的保护指数（71%）相当。去除 -F 复制子导致具有保护指数为 83%的重组病毒。在 v301B-BAC 和 v301B-delBAC 接种组中，攻毒病毒的脱落明显降低。总体而言，301B-BAC 衍生疫苗病毒对非常强毒力 MDV 攻毒的保护效力与亲本 301B/1 病毒和 SB-1 疫苗病毒相当。
