Date: Sunday, November 8, 2015
Session Type: ACR Poster Session A
Session Time: 9:00AM-11:00AM
Background/Purpose: B19 virus (B19V) is common, infects all ages, and is associated with various clinical syndromes including SLE-like autoimmunity. We previously demonstrated that B19 NS1, a superfamily 3 (SF3) viral helicase, is expressed in human cells non-permissive for virion production, damages host cell DNA by single strand nicking and bulky adduct formation, induces apoptosis, and produces apoptotic bodies (ApoBods) that are internalized by phagocytic cells. We hypothesized that ApoBods containing B19 NS1-modified DNA could break tolerance to self DNA. We developed an in vivo mouse model in which mice were inoculated with B19 NS1-induced ApoBods; we then examined serum dsDNA antibody production and tissue damage.
Methods: A baculovirus expression vector was used to tranduce B19 NS1 in HEp-G2 cells. ApoBods were harvested from culture supernatants at 72 hours post transduction. ApoBods generated by an inducer of apoptosis, staurosporine, were used as a positive control for ApoBods. BALB/c mice were untreated or injected subcutaneously with PBS, or 25 µg, 50 µg or 100 µg, respectively, of B19 NS1-induced ApoBods or staurosporine-induced ApoBods. Pristane, known to induce a lupus-like murine disease, was used as a positive control for autoimmunity induction. Serum dsDNA antibodies were examined with a Crithidia luciliae indirect immunofluorescence assay (IFA) using an anti-mouse IgG conjugate and quantitated with an in-house dsDNA ELISA. Paraffin-embedded tissue sections were examined for immune cell infiltration and damage.
Results: The Crithidia assay demonstrated positive kinetoplast and nuclear fluorescence staining with sera from mice treated with pristane, staurosporine ApoBods, or B19 NS1 ApoBods. dsDNA antibody by ELISA from 100 µg B19 NS1 ApoBod treated mice was significantly higher than untreated (p<0.0001), PBS-treated (p<0.0001), 100 µg Staurosporine ApoBod-treated (p<0.0006), and pristane-treated mice (p<0.02). Tissue histology revealed immune cell infiltration in kidney, brain, liver, and heart in treated groups, but not in untreated or PBS control groups.
Conclusion: B19 NS1 ApoBod inoculation induces dsDNA autoantibodies and tissue damage. While B19 NS1 ApoBod-, staurosporine ApoBod-, and pristane-treated mice all had tissue damage and dsDNA antibody by Crithidia testing, the B19 NS1 ApoBod-treated group had significantly elevated dsDNA antibody by ELISA compared to the other groups. This study supports the hypothesis that B19V and possibly other SF3 helicase-expressing viruses, such as Epstein-Barr virus, can induce tissue damage and dsDNA antibody production above that seen with ApoBods alone; dsDNA antibody production may be induced through helicase modification of self DNA.
To cite this abstract in AMA style:Pirttinen H, Puttaraksa K, Lagier RJ, Naides SJ, Gilbert L. Human Parvovirus B19 Nonstructural Protein 1 (NS1) Helicase Breaks Tolerance to Self dsDNA: A Model for Viral Induction of Autoimmunity [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/human-parvovirus-b19-nonstructural-protein-1-ns1-helicase-breaks-tolerance-to-self-dsdna-a-model-for-viral-induction-of-autoimmunity/. Accessed November 18, 2019.
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