Clinical associations and potential novel antigenic targets of autoantibodies directed against rods and rings in chronic hepatitis C infection

Abstract

BackgroundChronic hepatitis C virus (HCV) infection is frequently associated with extrahepatic autoimmune disorders while interferon (IFN) and ribavirin treatment may exacerbate these conditions. Autoantibodies from HCV patients identify a novel indirect immunofluorescence (IIF) pattern on HEp-2 cells characterized by cytoplasmic rods and rings (RR). Our objectives were to determine the prevalence and clinical associations of RR autoantibodies in HCV patients, and identify related novel autoantibody targets.MethodsSera from 315 patients with HCV (301 treatment naive, 14 treated with interferon and/or ribavirin) were analyzed for the presence of RR antibodies by IIF on commercially available HEp-2 cell substrates. Antibodies to inosine monophosphate dehydrogenase 2 (IMPDH2) and cytidine triphosphate synthase 1 (CTPS1) were detected by addressable laser bead assay and other potential targets were identified by immunoscreening a protein microarray. Clinical and demographic data including HCV genotype, mode of infection, prior antiviral therapy, and histological findings were compared between RR antibody positive (RR+) and negative (RR-) patients.ResultsThe median age of the HCV cohort was 51 years, 61% were male, and 76% were infected with HCV genotype 1 (G1). Four percent (n=14) had been treated with IFN-based therapy (IFN monotherapy, n=3; IFN/ribavirin, n=11); all had a sustained virologic response. In total, 15 patients (5% of the cohort) were RR+. RR+ and RR- patients had similar demographic and clinical characteristics including age, sex, mode of HCV infection, prevalence of the G1 HCV genotype, and moderate to severe fibrosis. Nevertheless, RR+ patients were significantly more likely than RR- cases to have been treated with IFN-based therapy (33% vs. 3%; adjusted odds ratio 20.5 [95% confidence interval 5.1-83.2]; P<0.0005). Only 1/10 RR positive sera had detectable antibodies to IMPHD2 and none had antibodies to CTPS1. Potentially important autoantibody targets identified on protein arrays included Myc-associated zinc finger protein (MAZI) and ankyrin repeat motif.ConclusionThe majority of HCV patients with RR autoantibodies previously received IFN/ribavirin antiviral therapy. Further studies are necessary to determine the genesis of intracellular RR and elucidate the clinically relevant autoantigens as well as the clinical and prognostic significance of their cognate autoantibodies.

Assembly of IMPDH2-Based, CTPS-Based, and Mixed Rod/Ring Structures Is Dependent on Cell Type and Conditions of Induction

“…Reports have shown the presence of anti-RR autoantibodies in up to 70% of HCV patients under interferon-a plus ribavirin treatment (Seelig et al, 2011;Covini et al, 2012;Keppeke et al, 2012). Stinton et al (2013), using an addressable laser bead immunoassay with beads conjugated to IMPDH2 and CTPS1 enzymes, found that only one out of ten anti-RR-positive serum samples had antibodies to IMPDH2 and none reacted with CTPS1. Probst et al (2013), using HEK293 cells expressing CTPS or IMPDH2 in a recombinant cell-based indirect immunofluorescence assay, analyzed 33 anti-RRpositive sera.…”

“…Anti-RR positive sera from HCV patients recognized only IMPDH2-based RR structures HCV patients that have undergone ribavirin/interferon-a therapy develop autoantibodies that recognize RR structures in a standard ANA-HEp-2 test (Covini et al, 2012;Keppeke et al, 2012;Carcamo et al, 2013;Stinton et al, 2013;Novembrino et al, 2014). It has been consistently shown that these autoantibodies recognize the IMPDH2 enzyme in roughly 70% of anti-RR positive samples (Seelig et RR components remains unknown.…”

Antinuclear antibodies – what to do with them?

“…Ten wzór fluorescencji występuje u chorych z zakażeniem HCV. Wykazano, że autoprzeciwciała tego typu swoiście reagują z dehydrogenazą inozyno-5'-mo nofosforanu (IMPDH2) [8].…”

“…This pattern of fluorescence is observed in patients with HCV infection. It has been demonstrated that such autoantibodies react specifically with inosine-5'-mono phosphate dehydrogenase (IMPDH2) [8].…”

Loukoumasomes Are Distinct Subcellular Structures from Rods and Rings and Are Structurally Associated with MAP2 and the Nuclear Envelope in Retinal Cells

“…Interestingly, mutations in the IMPDH1 gene, but not IMPDH2, result in the occurrence of a number of closely related retinal diseases [16–19]. Studies on RR have used cell cultures in which IMPDH2 is the higher expressed isotype [3–5, 8, 20]. However, IMPDH1 has also been shown to form RR structures [21, 22].…”