A TB40/E-derived human cytomegalovirus genome with an intact US-gene region and a self-excisable BAC cassette for immunological research

Biotechniques. 2017 Nov 1;63(5):205-214. doi: 10.2144/000114606.

Abstract

For immunological research on the human cytomegalovirus (HCMV), a virus that combines the broad cell tropism of clinical isolates, efficient replication in cell culture, the complete set of MHC-I modulator genes, and suitability for genetic engineering is desired. Here, we aimed to generate a genetically complete derivative of HCMV strain TB40/E as a bacterial artificial chromosome (BAC) with a self-excisable BAC cassette. The BAC cassette was inserted into the US2-US6 gene region (yielding TB40-BACKL7), relocated into the UL73/UL74 region with modifications that favor excision of the BAC cassette during replication in fibroblasts, and finally the US2-US6 region was restored, resulting in BAC clone TB40-BACKL7-SE When this BAC clone was transfected into fibroblasts at efficiencies >0.1%, replicating virus that had lost the BAC cassette appeared within 2 weeks after transfection, grew to high titers, and displayed the broad tropism of the parental virus. The degree of MHC-I down-regulation by this virus was consistent with functional restoration of US2-US6. To enable detection of infected cells by flow cytometry, an enhanced green fluorescent protein (EGFP)-expression cassette was inserted downstream of US34A, yielding the fluorescent virus RV-TB40-BACKL7-SE-EGFP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromosomes, Artificial, Bacterial / genetics*
  • Cloning, Molecular
  • Cytomegalovirus / genetics*
  • Cytomegalovirus / immunology
  • Cytomegalovirus / physiology
  • Cytomegalovirus Infections / immunology
  • Fibroblasts / virology
  • Foreskin / cytology
  • Genes, MHC Class I / genetics
  • Genes, MHC Class I / immunology
  • Genome, Viral / genetics*
  • Green Fluorescent Proteins / genetics
  • Human Umbilical Vein Endothelial Cells
  • Humans
  • Male
  • Primary Cell Culture
  • RNA-Binding Proteins / genetics*
  • Transfection
  • Viral Envelope Proteins / genetics*
  • Viral Proteins / genetics*
  • Viral Tropism
  • Virus Replication
  • Whole Genome Sequencing

Substances

  • RNA-Binding Proteins
  • US2 protein, Varicellovirus
  • US6 protein, Human cytomegalovirus
  • Viral Envelope Proteins
  • Viral Proteins
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins