Associate Professor, Department of Biochemistry
Ï㽶ÊÓƵ Biology and Viral Infections
McIntyre Medical Building, Room 805
3655 Promenade Sir William Osler
Office: Room 805B; Lab: Room 805
Montreal, Quebec H3G 1Y6
Tel: 514-398-8110; Lab: 514-398-5779
Fax: 514-398-7052
selena.sagan [at] mcgill.ca
2009 – PhD, University of Ottawa, Ottawa
Research Interests
MicroÏ㽶ÊÓƵs and Viral Infections
Viruses have been demonstrated to alter the expression of human microÏ㽶ÊÓƵs, cause specific degradation of microÏ㽶ÊÓƵs, and even encode their own, virally-derived microÏ㽶ÊÓƵs. These can all aid in maintaining viral latency, evasion of immune responses, and ultimately can dictate the outcomes of viral infections. Conversely, human microÏ㽶ÊÓƵs can alter the immune system and directly regulate responses to viral infections. Numerous broadly antiviral microÏ㽶ÊÓƵs have now been identified; however, their targets and roles in viral infections remain mysterious. What are the target genes of these microÏ㽶ÊÓƵs? How do they influence the viral life cycle? What is their role in modulating the immune response and disease pathogenesis? Can they be targeted for antiviral therapy? The answers to these questions will provide a broader understanding of the role of microÏ㽶ÊÓƵs in viral infections, immune responses, and disease pathogenesis.
Mechanisms governing HCV genome stability and viral Ï㽶ÊÓƵ accumulation
Hepatitis C virus (HCV) is a global health problem, affecting approximately 3% of the world population, including more than 268,000 Canadians. MicroÏ㽶ÊÓƵ-122 (miR-122) is a highly abundant liver-specific microÏ㽶ÊÓƵ that was demonstrated to have a genetic interaction with two sites within the 5’ untranslated region of the HCV genome. This is an unusual microÏ㽶ÊÓƵ interaction as it promotes viral Ï㽶ÊÓƵ accumulation both in cell culture and in vivo. Recent work suggests that miR-122 has at least three roles in the HCV life cycle: 1) it acts as an Ï㽶ÊÓƵ chaperone to repress an alternative secondary structure and allows the viral internal ribosomal entry site (IRES) to form; 2) it stabilizes the viral Ï㽶ÊÓƵ from pyrophosphatases and subsequent exoribonuclease-mediated decay; and 3) it promotes HCV translation. We are currently using novel pull-down and Ï㽶ÊÓƵ analysis strategies to analyze miR-122 complexes in HCV-infected cells, to determine the host and viral factors involved in, and the mechanism of, this unusual microÏ㽶ÊÓƵ-target Ï㽶ÊÓƵ interaction. These studies will help to identify novel host-virus interactions, and will define new targets for therapeutic intervention.
Dynamic Structure of Viral Ï㽶ÊÓƵs
The viral Ï㽶ÊÓƵ genome of positive-sense Ï㽶ÊÓƵ viruses is highly complex, as it must serve as a template for translation, replication, as well as packaging of the viral genome. As such, viral Ï㽶ÊÓƵs must be dynamic structures associated with numerous host and viral Ï㽶ÊÓƵ-binding proteins. Using structural probing strategies, including Selective 2' Hydroxyl Acylation analyzed by Primer Extension (SHAPE), we are currently analyzing viral Ï㽶ÊÓƵ structure, in vitro and in vivo in numerous contexts. Combined with pull-down strategies we hope to learn more about Ï㽶ÊÓƵ binding proteins and Ï㽶ÊÓƵ structures important for viral Ï㽶ÊÓƵ translation, replication and packaging.
Host and Viral Determinants of Zika Virus Fitness
Zika virus (ZIKV) is an emerging mosquito-borne pathogen of tremendous public health concern. The World Health Organization estimates that as many as 2.2 billion people are at risk of ZIKV infection. Currently, there are no vaccines or antiviral therapies to treat ZIKV infection and our understanding of the virus and its pathogenesis is limited. Although historically a benign infectious agent, recent introduction of ZIKV to the Western Hemisphere resulted in an explosive epidemic in South America associated with novel pathogenicity, including Guillain-Barré syndrome and fetal microcephaly. While genomic analyses have revealed that ZIKV has undergone evolution since its discovery, little is known regarding the impact of these polymorphisms on ZIKV pathogenesis. As such, we hypothesized that the contemporary strain(s) of ZIKV have evolved ways to increase viral fitness, counter the host immune response, and promote fetal pathogenesis. To investigate this, we performed comparative analyses of several ZIKV isolates in cell culture to identify phenotypic differences between historical and contemporary isolates. Subsequently, we have generated several chimeric viruses and we are using these to identify the region(s) of the viral genome responsible for phenotypic differences in viral Ï㽶ÊÓƵ accumulation, particle production and evasion of host innate immune responses in both human and mosquito cells. In addition, together with Dr. Martin Richer (Ï㽶ÊÓƵ) we have developed an immunocompetent mouse model of infection. Our lab is using comparative analyses, chimeric viruses, and site-directed mutagenesis to determine the impact of viral evolution on ZIKV fitness, infectivity, replication, and pathogenesis. Our preliminary data also indicates that ZIKV is able to induce a robust immune response in our immunocompetent mouse model and we are characterizing the immune response to infection with both the African and Asian lineage isolates. Together, these new tools will allow us to directly address the impact of viral polymorphisms, and will elucidate host and viral determinants of ZIKV fitness and pathogenesis.
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