Gary A Levy

Gary A Levy, BSc, MD, ARLAT, FRCPC

The focus of work in our laboratory has been to characterize unique molecules that participate in immune coagulation and to examine their role in human disease.

We have identified the molecules tissue factor and fgl2/fibroleukin, which are membrane associated serine proteases. These molecules play pivotal roles in the pathogenesis of viral hepatitis (fgl2/fibroleukin), allo- and xenograft rejection (tissue factor and fgl2). The importance of these molecules can be best shown by the fact that treatment of mice with high titered neutralizing antibodies to fgl2 prevents the lethality of fulminant viral hepatitis caused by murine hepatitis virus strain 3 (MHV-3).
Our research will focus over the next five years on:
  • The role of FGL2/fibroleukin in human and experimental viral hepatitis
  • The role of tissue factor and FGL2 in xenograft rejection (funded by the Heart and Stroke Foundation of Canada, co-investigator Dr. D. Grant)
  • CIHR Group Grant 'Cellular and Molecular Basis of Organ Injury.' Dir: Dr. G. Levy and 5 principal investigators Drs. G. Downey, O. Rotstein, P. Marsden, L. Zhang, and M. Cybulsky. The group was first funded by CIHR 10 years ago and the focus of the work is to: 1) promote scientific excellence and advance the state of knowledge in organ injury; 2) to promote research to allow advances to move from the bench to the bedside; and 3) to foster an environment for the training of future scientific leaders.
  • Molecular characterization of the proximal human and murine fgl2/fibroleukin promoter
    The overall objective of this set of studies is to examine the basic regulatory features involved in viral induced fgl2 gene transcription. We have initiated studies to map the upstream promoter region of the murine and human fgl2 genes and defined a region from -372 to -306 upstream from the ATG translation initiation site to be responsive to the nucleocapsid protein of strains of MHV that induce fulminant hepatitis. Functional promoter activity will be assessed by transient transfection studies in which cells will be cotransfected with a construct containing a relevant viral protein and a set of fgl2 promoter/luciferase deletion constructs. Binding sites for putative transcriptional regulatory molecules will be assessed by electromobility shift assays and super shift assays (EMSA).
  • Structure and function of fgl2/fibroleukin
    A recombinant murine fgl2 protein has now been generated using a baculovirus expression system. Fgl2 expressed in vesicles containing phospholipids has prothrombinase activity, whereas soluble fgl2 protein has potent immunosuppressive activity and can inhibit leukocyte-endothelial cell interactions. The experiments proposed will determine if these two functions are linked or can be assigned to different regions of the molecule.

    To accomplish this, a set of truncated constructs and constructs in which candidate serine residues have been mutated have been generated. The active catalytic site of the serine protease (prothrombinase) will be determined by an assessing prothrombinase activity in: a) fgl2 proteins generated by transient transfection studies using the fgl2 constructs in which candidate regions containing serine residues are deleted, or b) by site directed mutagenesis of candidate serine residues. The importance of the transmembrane domain will similarly be assessed by expressing protein in which this region has been truncated. Similarly, the region of the fgl2 protein required for the immunosuppressive activity will be assessed using native and truncated proteins to study their ability to inhibit mixed lymphocyte reaction cytotoxic T cell responses and endothelial-leukocyte adherence.
  • Pathobiology of fgl2/fibroleukin
    The physiological role of fgl2 will be assessed in mice in which the fgl2 gene has been disrupted using targeted homologous recombination. The mice will be studied primarily, but not exclusively, for the effect of deletion of fgl2 on: a) viral replication (MHV-3); b) susceptibility/resistance to MHV-3 infection; and c) ability of susceptible mice to mount a Th1/Th2 anti-viral response. Fgl2-deficient mice will also be used to assess the role of fgl2 on cytokine-induced fetal loss syndrome.
  • Significance
    Collectively, these studies will not only characterize the role of fgl2/fibroleukin in fulminant viral hepatitis but will also provide insights into the regulation of this gene which will have important therapeutic implications for patients with a broad spectrum of diseases in which thrombosis plays an integral component.
Transplant Direct. 2017 Oct;3(10):e213
Echeverri J, Goldaracena N, Singh AK, Sapisochin G, Selzner N, Cattral MS, Greig PD, Lilly L, McGilvray ID, Levy GA, Ghanekar A, Renner EL, Grant DR, McCluskey SA, Selzner M
Genes Chromosomes Cancer. 2017 May 31;:
Dewaele B, Libbrecht L, Levy G, Brichard B, Vanspauwen V, Sciot R, Debiec-Rychter M
World J Gastroenterol. 2017 Apr 21;23(15):2673-2684
Bartczak A, Zhang J, Adeyi O, Amir A, Grant D, Gorczynski R, Selzner N, Chruscinski A, Levy GA
Nat Chem Biol. 2016 Oct 10;:
Levy G, Habib N, Guzzardi MA, Kitsberg D, Bomze D, Ezra E, Uygun BE, Uygun K, Trippler M, Schlaak JF, Shibolet O, Sklan EH, Cohen M, Timm J, Friedman N, Nahmias Y
J Vis Exp. 2016;(115)
Chruscinski A, Huang FY, Ulndreaj A, Chua C, Fehlings M, Rao V, Ross HJ, Levy GA
Clin Gastroenterol Hepatol. 2016 Aug 24;
Levitsky J, Goldberg D, Smith AR, Mansfield SA, Gillespie BW, Merion RM, Lok AS, Levy G, Kulik L, Abecassis M, Shaked A
Am J Transplant. 2016 Aug 22;
Knaak M, Goldaracena N, Doyle A, Cattral MS, Greig PD, Lilly L, McGilvray ID, Levy GA, Ghanekar A, Renner EL, Grant DR, Selzner M, Selzner N
Transplant Direct. 2015 Sep;1(8):e30
Goldaracena N, Spetzler VN, Sapisochin G, J E, Moritz K, Cattral MS, Greig PD, Lilly L, McGilvray ID, Levy GA, Ghanekar A, Renner EL, Grant DR, Selzner M, Selzner N
Liver Transpl. 2016 Jun 17;
Doyle A, Adeyi O, Khalili K, Fischer S, Dib M, Goldaracena N, Dillon J, Grant D, Cattral M, McGilvray I, Greig P, Ghanekar A, Lilly L, Renner E, Levy G, Selzner N
Hepatobiliary Surg Nutr. 2016 Apr;5(2):118-26
Sapisochin G, Goldaracena N, Laurence JM, Levy GA, Grant DR, Cattral MS

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Director, Live Liver Donor Program, Multi-Organ Transplant, Toronto General Hospital
Professor, Department of Laboratory Medicine and Pathobiology, University of Toronto
Professor, Department of Immunology, University of Toronto