Plum Island Animal Disease Center, ARS, USDA, Greenport, NY 11944, USA.
Plum Island Animal Disease Center, APHIS, USDA, Greenport, NY 11944, USA.
Viruses. 2020 Oct 20;12(10):1185. doi: 10.3390/v12101185.
African swine fever virus (ASFV) is currently the most dreaded infectious disease affecting the global swine production industry. There is no commercial vaccine available, making the culling of infected animals the current solution to control outbreaks. Effective experimental vaccines have been developed by deleting virus genes associated with virulence. Deletion of the ASFV 9GL gene (∆9GL) has resulted in the attenuation of different ASFV strains, although the degree of attenuation varies across isolates. Here, we investigated the possibility of the increased safety of the experimental vaccine strain ASFV-G-Δ9GL by deleting two additional virus genes involved in pathogenesis, CD2v, a CD2 like viral encoded gene from the EP402R open reading frame (ORF), and C-type lectin-like viral gene, encoded from the EP153R ORF. Two new recombinant viruses were developed, ASFV-G-Δ9GL/ΔCD2v and ASFV-G-Δ9GL/ΔCD2v/ΔEP153R, harboring two and three gene deletions, respectively. ASFV-G-Δ9GL/ΔCD2v/ΔEP153R, but not ASFV-G-Δ9GL/ΔCD2v, had a decreased ability to replicate in vitro in swine macrophage cultures when compared with parental ASFV-G-Δ9GL. Importantly, ASFV-G-Δ9GL/ΔCD2v and ASFV-G-Δ9GL/ΔCD2v/ΔEP153R induced almost undetectable viremia levels when inoculated into domestic pigs and failed to protect them against challenge with parental virulent ASFV-Georgia, while ASFV-G-Δ9GL offered robust protection during challenge. Therefore, the deletion of CD2-like and C-type lectin-like genes significantly decreased the protective potential of ASFV-G-Δ9GL as a vaccine candidate. This study constitutes an example of the unpredictability of genetic manipulation involving the simultaneous deletion of multiple genes from the ASFV genome.
非洲猪瘟病毒（ASFV）是目前对全球养猪业造成威胁最大的传染病。目前尚无商业化疫苗可用，因此只能通过扑杀感染动物来控制疫情。通过删除与毒力相关的病毒基因，已经开发出有效的实验疫苗。删除 ASFV 的 9GL 基因（∆9GL）已导致不同 ASFV 株的减毒，尽管不同分离株的减毒程度有所不同。在这里，我们通过删除与发病机制相关的两个额外病毒基因 CD2v 和 C 型凝集素样病毒基因，研究了实验疫苗株 ASFV-G-Δ9GL 增加安全性的可能性，CD2v 是来自 EP402R 开放阅读框（ORF）的一种类似 CD2 的病毒编码基因，C 型凝集素样病毒基因则来自 EP153R ORF。开发了两种新的重组病毒，ASFV-G-Δ9GL/ΔCD2v 和 ASFV-G-Δ9GL/ΔCD2v/ΔEP153R，分别携带两个和三个基因缺失。与亲本 ASFV-G-Δ9GL 相比，ASFV-G-Δ9GL/ΔCD2v/ΔEP153R 在猪巨噬细胞培养物中的体外复制能力降低，但 ASFV-G-Δ9GL/ΔCD2v 则没有。重要的是，当接种到家猪体内时，ASFV-G-Δ9GL/ΔCD2v 和 ASFV-G-Δ9GL/ΔCD2v/ΔEP153R 引起的病毒血症水平几乎检测不到，并且不能保护它们免受亲本强毒 ASFV-Georgia 的攻击，而 ASFV-G-Δ9GL 则在攻毒时提供了强大的保护。因此，CD2 样和 C 型凝集素样基因的缺失显著降低了 ASFV-G-Δ9GL 作为候选疫苗的保护潜力。本研究为 ASFV 基因组中多个基因的同时缺失的遗传操作的不可预测性提供了一个实例。
