Genetic and biological characterizationof Zika virus from human cases imported through Shenzhen Port

During February to March 2016, a total of 13 Zika virus (ZIKV) cases were imported into China by travelers. Infection with ZIKV in humans results in fever, rash and has been associated with microcephaly as well as Guillain-Barre syndrome. ZIKV is a mosquito-borne flavivirus and Aedes mosquitoes are the main transmission vector species. Since Aede s are prevalent throughout China, ZIKV has the potential to become widely disseminated if not properly controlled. The genetic and biological characteristics of ZIKV should be thoroughly studied in order to enact effective countermeasures. A novel ZIKV strain (SZ_SMGC-1) was successfully isolated from the sera of an imported case returning to China from Fiji and Samoa at the Shenzhen Port. The entire viral genome was sequenced and compared to whole ZIKV genomes downloaded from GenBank. Results showed that SZ_SMGC-1 possesses the highest nucleotide identity (99.9%) to ZIKV from Fiji and Samoa, and also has high nucleotide identity (99.0%–99.4%) to ZIKV from Venezuela. Additionally, ZIKV is know to have evolved into distinct Asian and African lineages, and our phylogenetic analyses showed that the ZIKVs isolated from all imported cases into China clustered into the Asian lineage. To study the biological characteristics of ZIKV, SZ_SMGC-1 was used to infect different cell lines including the mosquito- derived C6/36, monkey-derived Vero and hamster-derived BHK-21 cells. Infection with SZ_SMGC-1 in vitro resulted in considerable cytopathic effects (CPE) to mammalian cells and supported replication of the virus to high titers, but did not cause readily observable CPE in C6/36 cells despite virus replication to comparable titers with mammalian cell lines. Interestingly, two clones of Vero and BHK-21 cell lines were used in the present study, respectively, but ZIKV SZ_SMGC-1 replicated much quicker to high virus titers in one clone than the other. Furthermore, there are no effective vaccine or drug for ZIKV until now. The results of the genetic and biological characteristics and the sensitive cell lines form the basis for further investigation into the pathogenesis and development of an effective medical countermeasure against ZIKV.