Berlin Institute of Health, Institute of Virology, Charité-Universitätsmedizin Berlin (corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin), Berlin, Germany.
Unité des Virus Émergents (Aix-Marseille University, IRD 190, Inserm 1207, IHU Méditerranée Infection), Marseille, France.
mSphere. 2019 Jul 3;4(4):e00295-19. doi: 10.1128/mSphere.00295-19.
Outbreaks of the emerging arbovirus chikungunya virus (CHIKV) affect millions of individuals in Asia, Africa, and Latin America. Vector competence can be changed dramatically by single amino acid exchanges located predominantly within the CHIKV E1 and E2 envelope proteins, which are associated with enhanced transmissibility by anthropophilic mosquitoes. Commonly used reference assays for molecular surveillance cover only a few adaptive mutations within the envelope domains and have not been validated for all CHIKV genotypes. The recognized landscape of CHIKV adaptive mutations is thus likely incomplete. We designed two nested reverse transcription-PCR (RT-PCR) assays that cover hot spots of viral adaptation to vectors within the E1 and E2 genomic domains. Primers were designed in conserved genomic regions to allow broad usability across CHIKV genotypes. The sensitivity of both assays was at least equivalent to E1- and E2-based reference assays and robust among CHIKV genotypes at 51.4 IU/reaction (E1, 95% confidence interval [CI], 39.8 to 78.9) and 4.0 IU/reaction (E2, 95% CI, 2.0 to 7.4). Upon analysis of the complete known CHIKV genomic diversity, up to 11 nucleotide mismatches with CHIKV variants occurred under oligonucleotide binding sites of reference assays, potentially limiting assay sensitivity, whereas no critical mismatches occurred in the new assays. Specificity testing with nine alphaviruses representing all serocomplexes showed amplification of Mayaro virus and O'nyong-nyong virus by the E1-based assay, but not by the E2-based assay. The high sensitivity and specificity of the new E2-based assay may allow its diagnostic usage in resource-limited settings. The combined new assays allow improved molecular epidemiological surveillance of CHIKV globally. The life cycle of arboviruses relies on efficient infection of and transmission by arthropod vectors. Adaptation to new vectors can thus dramatically increase the geographic range of an arbovirus. Several adaptive mutations enhance chikungunya virus (CHIKV) transmissibility by different mosquito species. The appearance of those adaptive mutations has led to large-scale CHIKV outbreaks in Asia, Africa, and Europe. Molecular surveillance of circulating CHIKV strains for adaptive mutations contributes to precise risk assessments and efficient vector control and provides new insight into the evolution of vector adaptation. Existing assays for molecular CHIKV surveillance are limited by poor coverage of known adaptive mutations, low sensitivity, and cost-intensive deep sequencing approaches, preventing universal application. We developed two highly sensitive nested RT-PCR assays that cover hot spots of vector adaptation in CHIKV envelope domains. The new assays allow unprecedented molecular surveillance across all CHIKV genotypes and diagnostic use in resource-limited settings globally.
正在出现的虫媒病毒基孔肯雅病毒 (CHIKV) 的爆发影响了亚洲、非洲和拉丁美洲的数百万人。通过主要位于 CHIKV E1 和 E2 包膜蛋白中的单个氨基酸交换,可以显著改变媒介效能,这与嗜人蚊子的传播能力增强有关。常用于分子监测的常用参考检测方法仅涵盖包膜结构域内的少数适应性突变,并且尚未针对所有 CHIKV 基因型进行验证。因此,公认的 CHIKV 适应性突变景观可能并不完整。我们设计了两种嵌套逆转录-PCR (RT-PCR) 检测方法,涵盖了 E1 和 E2 基因组结构域中病毒适应媒介的热点。引物设计在保守的基因组区域内,以允许在 CHIKV 基因型之间广泛使用。两种检测方法的敏感性至少与基于 E1 和 E2 的参考检测方法相当,并且在 51.4 IU/反应(E1,95%置信区间 [CI],39.8 至 78.9)和 4.0 IU/反应(E2,95%CI,2.0 至 7.4)之间在 CHIKV 基因型中稳健。在分析完整的已知 CHIKV 基因组多样性时,参考检测方法的寡核苷酸结合位点下与 CHIKV 变体发生多达 11 个核苷酸不匹配,这可能限制了检测的敏感性,而新检测方法中没有发生关键的不匹配。用代表所有血清复合物的九种甲病毒进行特异性检测显示,E1 基检测方法可扩增 Mayaro 病毒和 O'nyong-nyong 病毒,但 E2 基检测方法不行。新的基于 E2 的检测方法的高灵敏度和特异性可能允许其在资源有限的环境中用于诊断。新的组合检测方法允许在全球范围内改进 CHIKV 的分子流行病学监测。虫媒病毒的生命周期依赖于节肢动物媒介的有效感染和传播。因此,对新媒介的适应可以极大地增加虫媒病毒的地理范围。一些适应性突变可增强基孔肯雅病毒 (CHIKV) 通过不同蚊子物种的传播能力。这些适应性突变的出现导致了亚洲、非洲和欧洲的大规模 CHIKV 爆发。对循环 CHIKV 株中适应性突变的分子监测有助于进行精确的风险评估和有效的媒介控制,并为媒介适应的进化提供新的见解。现有的分子 CHIKV 监测检测方法存在已知适应性突变覆盖率低、灵敏度低以及成本高昂的深度测序方法等局限性,从而无法普遍应用。我们开发了两种高度敏感的嵌套 RT-PCR 检测方法,可覆盖 CHIKV 包膜结构域中媒介适应的热点。新的检测方法允许对所有 CHIKV 基因型进行前所未有的分子监测,并在全球资源有限的环境中进行诊断使用。