108 Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA.
Vet Microbiol. 2010 Feb 24;141(1-2):5-11. doi: 10.1016/j.vetmic.2009.07.030. Epub 2009 Aug 8.
A panel of 426 archived EHV-1 isolates collected (1951-2006) from equine abortions was analyzed using a real-time Taq-Man((R)) allelic discrimination PCR assay. Based on previous findings, isolates possessing adenine at nucleotide position 2254 (A(2254)) in ORF30 were classified as having a non-neuropathogenic genotype and those with guanine at 2254 (G(2254)) were designated as the neuropathogenic genotype. The resultant data demonstrated that viruses with the neuropathogenic genotype existed in the 1950s and isolates with this genotype increased from 3.3% in the 1960s to 14.4% in the 1990s. The incidence of EHV-1 isolates from 2000 to 2006 with G at position 2254 is 19.4%, suggesting that viruses with the neuropathogenic genotype are continuing to increase in prevalence within the latent reservoir of the virus, leading to greater risks for costly outbreaks of equine herpesvirus neurologic disease. Another highly significant finding was two isolates failed to react with either probe in the allelic discrimination assay. These isolates were found to possess an adenine to cytosine substitution at position 2258 (A(2258)-->C(2258)) in ORF30, in addition to A(2254)-->G(2254). Interestingly, the non-neuropathogenic RAC-H modified live vaccine strain of EHV-1 also contains both A(2254)-->G(2254) and A(2258)-->C(2258) substitutions. This finding clearly suggests that additional research is required before the genetic basis of the neuropathogenic phenotype in EHV-1 is fully understood.
从马流产胚胎中收集了 426 株存档的 EHV-1 分离株（1951-2006 年），并使用实时 Taq-Man((R))等位基因区分 PCR 分析。根据先前的发现，在 ORF30 中核苷酸位置 2254 处具有腺嘌呤（A(2254)）的分离株被归类为非神经致病性基因型，而在 2254 处具有鸟嘌呤（G(2254)）的分离株被指定为神经致病性基因型。结果数据表明，具有神经致病性基因型的病毒存在于 20 世纪 50 年代，并且具有这种基因型的分离株从 20 世纪 60 年代的 3.3%增加到 20 世纪 90 年代的 14.4%。从 2000 年到 2006 年，位置 2254 为 G 的 EHV-1 分离株的发生率为 19.4%，这表明具有神经致病性基因型的病毒在病毒潜伏库中的流行率持续增加，导致马疱疹病毒神经疾病的昂贵爆发的风险更大。另一个非常重要的发现是，有两个分离株在等位基因区分试验中均不能与任一探针反应。这些分离株被发现除了 A(2254)-->G(2254)外，在 ORF30 中还存在位置 2258 处腺嘌呤到胞嘧啶的取代（A(2258)-->C(2258)）。有趣的是，EHV-1 的非神经致病性 RAC-H 减毒活疫苗株也同时含有 A(2254)-->G(2254)和 A(2258)-->C(2258)取代。这一发现清楚地表明，在充分了解 EHV-1 神经致病性表型的遗传基础之前，还需要进行更多的研究。
