Selective activation of inflammation factors by human parvovirus B19 and human bocavirus VP1 unique region on H9c2 cardiomyocyte

Human parvovirus B19 (B19) and human bocavirus 1 (HBoV) are the only known pathogenic parvoviruses, and are responsible for a variety of diseases in human beings. Mounting evidence indicates a strong association between B19 infection and cardiac disorders including myocarditis, dilated cardiomyopathy and heart failure. However, very limited information about the role of HBoV in cardiac disorders is known. To elucidate the effects of B19 and HBoV on cardiac disorders, we expressed EGFP-conjugate constructs of B19-VP1 unique region (VP1u) and HBoV-VP1u, along with the mutants EGFP-B19-VP1uD175A and EGFP-HBoV-VP1uV12A, in H9c2 cells by stable transfection. The protein expression levels of EGFP, EGFP-B19-VP1u, EGFP-B19-VP1uD175A, EGFP-HBoV-VP1u and EGFP-HBoV-VP1uV12A in H9c2 cells were observed under a fluorescence microscope and confirmed by western blotting. Secreted phospholipase A2 (sPLA2) activity was detected in B19-VP1u and HBoV-VP1u but not B19-VP1uD175A and HBoV-VP1uV12A recombinant proteins. Significantly higher expression levels of MCP2 and IP-10 mRNA were detected in H9c2 cells that were transfected with pEGFP-B19-VP1u, compared with in those cells transfected with pEGFP-HBoV-VP1u, pEGFP-B19-VP1uD175A or pEGFP-HBoV-VP1uV12A. Significantly higher protein levels of IL-1β and IL-6 were detected in H9c2 cells transfected with pEGFP-B19-VP1u or pEGFP-HBoV-VP1u, compared with in those cells transfected with pEGFP-B19-VP1uD175A or pEGFP-HBoV-VP1uV12A. Notably, significantly higher expression of both TNF-α and NF-κB was observed only in H9c2 cells transfected with pEGFP-B19-VP1u, but not in those cells transfected with pEGFP-HBoV-VP1u, pEGFP-B19-VP1uD175A or pEGFP-HBoV-VP1uV12A. These findings, to our knowledge for the first time, reveal the difference between B19-VP1u and HBoV-VP1u in H9c2 cells and provide insight into the roles of B19-VP1u and HBoV-VP1u in the pathogenesis of cardiac inflammation.