Investigating the role of the base mismatches within the hairpin ends of vaccinia virus genome in viral life cycle

• Author / Creator

  Shenouda, Mira M.M.

• The genome of poxviruses consists of a double-stranded DNA that is flanked by two AT-rich hairpin ends encoding mismatched nucleotides. These mismatched structures are composed of incompletely base paired regions forming extra-helical loops. Though the functionality of these mismatches has not yet been firmly established, their presence is conserved among all completely sequenced poxviruses. Thus, the focus of this project has been to study the function(s) of the hairpin ends and the mismatches within them.
  These ends of the poxvirus genome have been very difficult to study using conventional recombination-based genome editing methods. Using synthetic genome assembly methods, I have modified these ends to remove some of the mismatches. We showed that simply altering the sequence of the 70bp hairpin ends attenuates the virus. Specifically, our results showed that removing most of these mismatches suppressed the growth of the virus. However, these modifications do not affect viral genome replication nor the resolution reactions that generate monomeric genomes. The most penetrant of these telomeric mutations caused about a 12-fold increase in the proportion of defective viral particles. However, these defective particles still packaged DNA. Finally, our microscopy data suggests that altering the hairpin ends affects virion maturation, causing the accumulation of defective immature virions in infected cells. We also showed that these forms of mutant viruses exhibited decreased virulence in immunocompromised mice. However, these attenuated strains can still be used as vaccines to protect against a lethal challenge in immunocompetent animals.

• Subjects / Keywords

  • Vaccinia Virus
  • Vaccinia--Research

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-p8nh-9803

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.