Neuroinvasiveness of the MR766 strain of Zika virus in IFNAR-/- mice maps to prM residues conserved amongst African genotype viruses

PLoS Pathog. 2021 Jul 26;17(7):e1009788. doi: 10.1371/journal.ppat.1009788. eCollection 2021 Jul.

Abstract

Zika virus (ZIKV) strains are classified into the African and Asian genotypes. The higher virulence of the African MR766 strain, which has been used extensively in ZIKV research, in adult IFNα/β receptor knockout (IFNAR-/-) mice is widely viewed as an artifact associated with mouse adaptation due to at least 146 passages in wild-type suckling mouse brains. To gain insights into the molecular determinants of MR766's virulence, a series of genes from MR766 were swapped with those from the Asian genotype PRVABC59 isolate, which is less virulent in IFNAR-/- mice. MR766 causes 100% lethal infection in IFNAR-/- mice, but when the prM gene of MR766 was replaced with that of PRVABC59, the chimera MR/PR(prM) showed 0% lethal infection. The reduced virulence was associated with reduced neuroinvasiveness, with MR766 brain titers ≈3 logs higher than those of MR/PR(prM) after subcutaneous infection, but was not significantly different in brain titers of MR766 and MR/PR(prM) after intracranial inoculation. MR/PR(prM) also showed reduced transcytosis when compared with MR766 in vitro. The high neuroinvasiveness of MR766 in IFNAR-/- mice could be linked to the 10 amino acids that differ between the prM proteins of MR766 and PRVABC59, with 5 of these changes affecting positive charge and hydrophobicity on the exposed surface of the prM protein. These 10 amino acids are highly conserved amongst African ZIKV isolates, irrespective of suckling mouse passage, arguing that the high virulence of MR766 in adult IFNAR-/- mice is not the result of mouse adaptation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood-Brain Barrier
  • Capillary Permeability
  • Genotype
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Viral Envelope Proteins / genetics*
  • Virulence / genetics*
  • Zika Virus / genetics*
  • Zika Virus / metabolism
  • Zika Virus / pathogenicity*
  • Zika Virus Infection / virology*

Substances

  • Viral Envelope Proteins
  • prM protein, Flavivirus

Grants and funding

This research was supported by the Research Program on Emerging and Re-emerging Infectious Diseases of the Japan Agency for Medical Research and Development (AMED, Grant Number JP19fk0108035. https://www.amed.go.jp/en/program/list/11/02/002.html. S.T. and C.K.L.). E.N. was supported in part by the Daiichi Sankyo Foundation of Life Science, Japan (http://www.ds-fdn.or.jp/support/studying_abroad.html). A.S. holds an Investigator grant (APP1173880) from the National Health and Medical Research Council (NHMRC) of Australia (https://www.nhmrc.gov.au/). The project was also funded in part by an NHMRC Project grant APP1144950 (A.S.), JSPS KAKENHI Grant Number JP20K07530 (https://www.jsps.go.jp/english/index.html. E.N.) and AMED Grant Number JP19fk0108067 (C.K.L.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.