Abstract Book - Pathology and Laboratory Medicine - University of ...

ABSTRACT #30BASIC SCIENCESGRADUATE STUDENTPOSTER presentationRole of CXCL10 and its receptor CXCR3 in Coxsackievirus B3-induced viralmyocarditisYe Qiu 1 , Mary Zhang, Maged Hemida, Xin Ye, Paul Hanson and Decheng Yang1Department of Pathology and Laboratory Medicine, UBC; 2 The Institute of Heat and Lung Health,St. Paul's Hospital42Background /objectivesCoxsackievirus B3 (CVB3) is a predominant pathogen in viral myocarditis, an inflammatory disease of themyocardium. In our previous studies using a CVB3-myocarditis mouse model, we found that CXCL10, aninterferon (IFN) γ-inducible secreted chemokine expressed by immune cells, was dramatically up-regulated duringCVB3 infection and the expression level of CXCL10 was always correlated with the severity of myocarditis at thelater stage of infection. However, the details about the role of CXCL10 in CVB3-induced viral myocarditis remainobscure. Generally, two mechanisms contribute to pathogenesis of viral infections: 1) direct cell injury due to virusamplification, and 2) damage of the tissue as a result of over-reactive immune response. Our recent data suggest thatCXCL10 induces premature cell death and recruitment of NK cells, while persistent over-expression of CXCL10 inthe heart initiates exaggerated immune responses which does harm to heart function, hinting that CXCL10 may playdual functional role in determining outcome of CVB3 infection: 1) inhibiting the virus via inducing cell apoptosis andrecruitment of NK cells at the early phase of infection, and 2) inducing exaggerated immune responses at late phaseof infection, resulting in fetal gene expression and cardiac disruption/remodeling. CXCL10 activate the downstreampathway via interaction with its receptor CXCR3. CXCR3 exists in three alternative splicing forms, A, B and alt.It has been reported that CXCR3-A mediates cell proliferation while CXCR3-B mediates inhibition of cell growth.Hence, we frame our hypothesis that expression of different splicing forms of CXCR3 critically contributes to the dualfunction of CXCL10 in CVB3 infection: 1) up-regulation of CXCR-B during the early stage of infection activates thepro-apoptotic genes, leading to cell death; 2) up-regulation of CXCR3-A during the late stage of infection results infetal gene expression and subsequent cell growth.Methods1) To detect changes of expression of CXCR-A and CXCR-B in different phases of CVB3 infection, expression level ofthe two splicing forms during CVB3 infection were measured by RT-PCR in sham- and CVB3-infected HeLa cells. 2)To uncover the relationship between different splicing forms of CXCR3 and CXCL10-induced downstream pathwaysduring CVB3 infection, CXCL10 antagonists were designed and used. Considering the N-terminus of CXCL10 playsa critical role in receptor activation, we designed different CXCL10 antagonists by deleting or changing several aminoacids at the N-terminus of CXCL10 and tested if they can attenuate the function of CXCR3 in a CVB3-infectedmouse cardiomyocyte HL-1 cell line. Expression of pro-apoptotic gene p53 and its responsive genes p21 and p27, aswell as viral capsid proteins VP1 was detected by western blot to serve as the indicator of CXCR-B's function.ResultsWild-type CXCL10 was shown to up-regulate p21, p27 and p53 and inhibit viral protein VP1 at 16 hours postinfection, while this effect could be reversed by CXCL10-Ant-d4, an antagonist with deletion of ten amino acids in theN-terminus of wild-type CXCL10, in a dose dependent manner.ConclusionsWith only quite preliminary data, no critical conclusions can be drawn.2012 * Oral/Poster Presentations