Isolation of Zika Virus Imported from Tonga into Australia

This study and case reporting was approved by the Forensic and Scientific Services Human Ethics Committee. Results Of all isolation attempts, only the serum-derived SMB was positive, with a Ct value of 29. To further amplify viable virus, the serum-derived SMB was then inoculated in duplicate onto C6/36 cells and intrathoracically into pools of ≤10 Ae. aegypti mosquitoes. Cell and supernatant fractions from cultures and mosquitoes were individually screened by RT-PCR. Mean±SD Ct values for the culture samples were 16.13±0.74 and 18.76±0.62 for the cells and supernatant, respectively, and a mean±SD Ct of 18.22±1.27 was obtained from 25 pools of positive Ae. aegypti. The SMB-recovered ZIKV isolate TS17-2016 was passaged in C6/36 cells 4 times yielding 50% tissue culture infectious dose (TCID50) viral titers of 6.80, 9.15, 9.80 and 8.00 log10 TCID50/mL for passages 1, 2, 3 and 4, respectively. The mean±SD titer of the positive mosquito pools was 3.47±0.67 log10 TCID50/mL. The SMB viral titers were below the TCID50 assay threshold of detection. Complete E gene sequences were determined for the TS17-2016 isolate and other strains imported recently into Australia via viremic travelers (GenBank accession numbers KX216632, KX216633, KX216634, KX216636, KX216637, KX216638, KX216639, KX380262 and KX380263). Phylogenetic analysis (Fig. 1) of the TS17-2016 ZIKV isolate (GenBank accession number KX216635) demonstrated the virus belonged to the Asian lineage together with con...
Source: PLOS Currents Outbreaks - Category: Epidemiology Authors: Source Type: research