Background/Purpose: The hallmark of SLE is pathogenic autoantibody (aab) production that is closely associated with organ damage. Anti-dsDNA aab are specific to SLE; their deleterious effects are mediated by direct binding of aab or anti-dsDNA containing immune complexes to tissue antigen and TLRs leading to stimulation of inflammatory pathways. Current therapies include immunosuppressive/cytotoxic drugs with significant potential toxicities.  Protease inhibitors (PIs) such as nelfinavir, in addition to direct anti-viral properties, are safe and well-tolerated and have been shown to have immunomodulatory effects. Previous studies have shown that nelfinavir inhibits murine anti-dsDNA aab binding by ELISA. We hypothesized that nelfinavir would similarly inhibit binding of human anti-dsDNA antibodies from SLE subjects, decrease pro-inflammatory cytokine gene expression in stimulated peripheral blood mononuclear cells (PBMC) and inhibit anti-DNA aab binding to mouse glomeruli ex-vivo.

Methods: Sera from 4 SLE subjects with elevated serum anti-DNA aab and increased disease activity (SLEDAI of ≥4) were incubated with increasing concentrations of nelfinavir (1 µM, 10 µM, and 100 µM) and added to the ELISA plate followed by spectrophotometric analysis. Healthy PBMC were stimulated with lipopolysaccharide (LPS)(5µg/mL) or high-mobility group box 1 protein (HMGB1)(10µg/mL) and incubated with nelfinavir (1 µM, 10 µM, and 100 µM).  Cytokine gene expression (IL-6, IL-12α, TNFα, INFα, IL-1β) and IFN inducible gene expression (IFIT1, MX1, IFI44, and OAS1) were measured in the PBMCs by PCR. The glomerular binding assay was used to measure inhibitory effects of nelfinavir on murine anti-DNA aab binding to glomerular antigen(s) with and without DNase treatment.

Results: Nelfinavir at 1, 10 and 100 µM concentrations resulted in 59%, 60% and 56% inhibition of DNA binding by ELISA respectively (p=0.01, p=0.02, p=0.01). Increasing concentrations of nelfinavir incubated with LPS-stimulated PBMC resulted in decreased gene expression of IL-12α (99%, 99%, and 99%), TNFα (90%, 90%, and 90%), IFNα (99%, 99%, and 99%) and IL1β (64%, 51%, and 24%). IL6 gene expression was decreased with 1 and 10µM concentrations but increased with 100 µM concentration.  HMGB1 stimulated PBMC demonstrated increased expression of TNFα, IL12α, IFNα, IL1β and the IFN inducible genes IFIT 1, MX1, IFI44 and OAS1 that was inhibited by nelfinavir with no clear dose response. IL6 gene expression was not increased by HMGB1 although addition of nelfinavir inhibited the expressed levels. The 100 µM concentration of nelfinavir abrogated glomerular binding of murine anti-DNA aab to glomerular antigens.

Conclusion: Nelfinavir inhibits human anti-dsDNA binding to dsDNA and murine anti-DNA aab binding to glomerular antigen. Additionally, nelfinavir reduces expression of pro-inflammatory cytokines and IFN inducible genes in LPS and HMGB-1 stimulated PBMC suggesting that the mechanism for inhibition may be interference with the antigen binding site of the anti-dsDNA aab. We plan to use these measures as biologic outcome measures for a phase IIa clinical trial exploring the in-vivo inhibitory effects of nelfinavir in SLE patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effects-of-nelfinavir-on-anti-dsdna-antibody-binding-and-pro-inflammatory-cytokine-gene-expression/