Attenuation of Zika Virus by Passage in Human HeLa Cells

Li Li; Natalie D Collins; Steven G Widen; Emily H Davis; Jaclyn A Kaiser; Mellodee M White; M Banks Greenberg; Alan D T Barrett; Nigel Bourne; Vanessa V Sarathy

doi:10.3390/vaccines7030093

Attenuation of Zika Virus by Passage in Human HeLa Cells

Vaccines (Basel). 2019 Aug 20;7(3):93. doi: 10.3390/vaccines7030093.

Authors

Li Li¹, Natalie D Collins^{2

3}, Steven G Widen⁴, Emily H Davis¹, Jaclyn A Kaiser², Mellodee M White⁵, M Banks Greenberg⁵, Alan D T Barrett^{1

6

7}, Nigel Bourne^{2

5

6

7}, Vanessa V Sarathy^{8

9

10}

Affiliations

¹ Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA.
² Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA.
³ Viral Disease Branch, Walter Reed Army Institute for Research, Silver Spring, MD 20910, USA.
⁴ Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA.
⁵ Department of Pediatrics, University of Texas Medical Branch, Galveston, TX 77555, USA.
⁶ Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX 77555, USA.
⁷ Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77555, USA.
⁸ Department of Pathology, University of Texas Medical Branch, Galveston, TX 77555, USA. vvsarath@utmb.edu.
⁹ Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX 77555, USA. vvsarath@utmb.edu.
¹⁰ Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77555, USA. vvsarath@utmb.edu.

Abstract

Zika virus (ZIKV) is a mosquito-borne Flavivirus. Previous studies have shown that mosquito-transmitted flaviviruses, including yellow fever, Japanese encephalitis, and West Nile viruses, could be attenuated by serial passaging in human HeLa cells. Therefore, it was hypothesized that wild-type ZIKV would also be attenuated after HeLa cell passaging. A human isolate from the recent ZIKV epidemic was subjected to serial HeLa cell passaging, resulting in attenuated in vitro replication in both Vero and A549 cells. Additionally, infection of AG129 mice with 10 plaque forming units (pfu) of wild-type ZIKV led to viremia and mortality at 12 days, whereas infection with 10³ pfu of HeLa-passage 6 (P6) ZIKV led to lower viremia, significant delay in mortality (median survival: 23 days), and increased cytokine and chemokine responses. Genomic sequencing of HeLa-passaged virus identified two amino acid substitutions as early as HeLa-P3: pre-membrane E87K and nonstructural protein 1 R103K. Furthermore, both substitutions were present in virus harvested from HeLa-P6-infected animal tissue. Together, these data show that, similarly to other mosquito-borne flaviviruses, ZIKV is attenuated following passaging in HeLa cells. This strategy can be used to improve understanding of substitutions that contribute to attenuation of ZIKV and be applied to vaccine development across multiple platforms.

Keywords: HeLa cells; Zika virus; Zika virus NS1; Zika virus prM; attenuation; flavivirus.