Comparative studies of the replication of African and Asian strains of Zika virus

Zika virus (ZIKV) is a mosquito-borne virus and can cause severe diseases. Based on phylogenetic analysis, ZIKV can be classified into African and Asian lineages. Clinical studies indicated that these two lineages of ZIKV exhibit differences in their pathogenicity. To understand how these two lineages of ZIKV may be different from each other, I compared the replication of two strains of ZIKV, MR766, and H/PF/2013, which belong to the African lineage and the Asian lineage, respectively. These two strains of ZIKV were produced in either Huh7 human hepatoma cells or Vero green monkey kidney cells, and their infectivity and growth curves were comparatively analyzed in HeLa cervical carcinoma cells, Vero cells, and HepG2 human hepatoblastoma cells. I found that these two strains of ZIKV exhibited differences in their plaque morphologies, cytopathic effects and growth curves. These effects also differed depending on whether the viruses were prepared in Huh7 cells or Vero cells. In addition, I also found that these two strains of ZIKV could induce autophagy in their host cells, although with different induction kinetics, and they could also induce the expression of autophagy-related genes including Atg4B, Beclin-1, and AKT. Interestingly, the ZIKV NS2B and NS4A proteins, but not its envelope protein, were found to colocalize with autophagosomes, indicating the possible involvement of autophagosomes in the replication of ZIKV. My study thus provided important information for understanding why these two strains of ZIKV differ in their pathogenicity in patients.

寨卡病毒（Zika virus, ZIKV）是一种虫媒病毒，可引发重症疾病。经系统发育分析，寨卡病毒可分为非洲支系与亚洲支系。临床研究表明，这两类支系的寨卡病毒在致病性上存在差异。为探究两类寨卡病毒支系间的差异机制，本研究选取分别隶属于非洲支系与亚洲支系的两株寨卡病毒毒株MR766与H/PF/2013，对其复制特性进行比较分析。上述两株寨卡病毒分别在Huh7人肝癌细胞（Huh7 human hepatoma cells）与Vero绿猴肾细胞（Vero green monkey kidney cells）中扩增制备，随后在HeLa宫颈癌细胞（HeLa cervical carcinoma cells）、Vero细胞及HepG2人肝母细胞瘤细胞（HepG2 human hepatoblastoma cells）中对比分析其感染性与生长曲线。研究发现，两株寨卡病毒在噬斑形态、细胞病变效应及生长曲线方面均存在显著差异，且该差异同样受病毒制备所用细胞系的影响。此外，本研究还发现，两株毒株均可诱导宿主细胞发生自噬，但诱导动力学存在明显区别；二者还均可上调自噬相关基因（autophagy-related genes）的表达，涉及Atg4B、Beclin-1及AKT。值得关注的是，寨卡病毒NS2B与NS4A蛋白（而非包膜蛋白）可与自噬体（autophagosomes）共定位，提示自噬体可能参与寨卡病毒的复制过程。本研究为阐释两株寨卡病毒在患者体内致病性差异的内在机制提供了重要实验依据。