Longitudinal study of a human drug-induced model of autoantibody to cytoplasmic rods/rings following HCV therapy with ribavirin and interferon-α

The value of anti-rods and rings antibodies in Chinese population of Dalian City: A retrospective study

The study aimed to investigate the clinical significance of anti-rods and rings (anti-RR) antibodies in antinuclear antibodies (ANAs) test samples retrospectively. The laboratory data and clinical details of patients with positive anti-RR antibodies were collected and analysed between December 2017 and May 2022 in the First Affiliated Hospital of Dalian Medical University. A total of 72 665 patients were tested for ANAs. There were 45 632 patients discovered with positive ANAs (62.80%), only 131 patients presented with anti-RR antibodies (0.18%), among which only 68 patients were hospitalized patients with a definitive diagnosis. Among the 68 patients with a definitive diagnosis, 8 of 68 (11.8%) had autoimmune diseases, and 19 of 68 (27.9%) had renal diseases. Other diseases included liver disease, pulmonary disease, cerebral ischemia, cerebral infarction, chronic cardiac failure and venous thromboembolism. The detection rate of high titre(≥1:1000) anti-RR antibodies is significantly higher in autoimmune diseases.

The Role of Autoantibody Testing in Modern Personalized Medicine

Personalized medicine (PM) aims individualized approach to prevention, diagnosis, and treatment. Precision Medicine applies the paradigm of PM by defining groups of individuals with akin characteristics. Often the two terms have been used interchangeably. The quest for PM has been advancing for centuries as traditional nosology classification defines groups of clinical conditions with relatively similar prognoses and treatment options. However, any individual is characterized by a unique set of multiple characteristics and therefore the achievement of PM implies the determination of myriad demographic, epidemiological, clinical, laboratory, and imaging parameters. The accelerated identification of numerous biological variables associated with diverse health conditions contributes to the fulfillment of one of the pre-requisites for PM. The advent of multiplex analytical platforms contributes to the determination of thousands of biological parameters using minute amounts of serum or other biological matrixes. Finally, big data analysis and machine learning contribute to the processing and integration of the multiplexed data at the individual level, allowing for the personalized definition of susceptibility, diagnosis, prognosis, prevention, and treatment. Autoantibodies are traditional biomarkers for autoimmune diseases and can contribute to PM in many aspects, including identification of individuals at risk, early diagnosis, disease sub-phenotyping, definition of prognosis, and treatment, as well as monitoring disease activity. Herein we address how autoantibodies can promote PM in autoimmune diseases using the examples of systemic lupus erythematosus, antiphospholipid syndrome, rheumatoid arthritis, Sjögren syndrome, systemic sclerosis, idiopathic inflammatory myopathies, autoimmune hepatitis, primary biliary cholangitis, and autoimmune neurologic diseases.

The clinical value of indirect immunofluorescence for screening anti-rods and rings antibodies: A retrospective study of two centers in China

Objective

To investigate the distribution and clinical significance of the rods and rings (RR) pattern in various diseases.

Methods

A total of 169,891 patients in Peking Union Medical College Hospital (PUMCH) and 29,458 patients in Inner Mongolia People’s Hospital (IMPH) from January 2018 to December 2020 were included, and the results of ANA (antinuclear antibodies) and special antibodies were analyzed retrospectively.

Results

The positive rates of ANA and RR patterns were 34.84%, 0.16% in PUMCH, and 44.73%, 0.23% in IMPH. Anti-RR antibodies mainly appear in adults (≥ 41 years), mostly of low or medium fluorescence titers. Isolated RR patterns were mostly presented (60.30% and 69.12%, respectively), and the RR pattern mixed with the speckled pattern was most commonly observed among patients having two or more patterns. The RR pattern existed in a variety of diseases including hepatitis C, AIDs, pulmonary diseases, nephropathy diseases, and even healthy people. The highest prevalence of the RR pattern was observed in hepatic diseases, such as hepatic dysfunction (0.79%), hepatic cirrhosis (1.05%), PBC (0.85%), and AIH (0.65%), etc. The positive rate of specific antibodies in RR pattern cases was 31.25%, and anti-Ro52 (27, 20.61%) was the most common target antibody.

Conclusion

The RR pattern had a low prevalence in ANAs test samples and varied in different nationalities and regions. Except for hepatitis C, it could be observed in AIDs, pulmonary diseases, nephropathy, other hepatic diseases, and even healthy people, but the positive rate was slightly higher in hepatic diseases. Its mechanism of action and clinical relevance still need clarification.

High prevalence of antinuclear antibodies in patients with chronic hepatitis C virus infection

Background

Hepatitis C virus (HCV) infection is a serious public health concern due to its high prevalence and mortality rate. In chronic infection, HCV may induce autoimmune responses through the production of autoantibodies, including antinuclear antibodies (ANA).

Methods

We assessed the presence of ANA by indirect immunofluorescence using HEp-2 cells in 89 patients with chronic hepatitis C. We also collected data on epidemiological variables; clinical characteristics; and biochemical, hematological, molecular, and histopathological information from the patients to assess the impact of the presence of ANA in those patients.

Results

The prevalence of ANA in the patients was 20.2%, which was significantly higher than that found in healthy controls (2%). However, there was no association of this marker with epidemiological, clinical-laboratory, molecular or histopathological characteristics of hepatitis C, although a slightly higher prevalence of ANA was detected in women and in patients infected with subgenotype 1a. In a specific analysis, chronic HCV patients with the “rods and rings” cytoplasmic pattern had higher degrees of hepatic fibrosis than did ANA-negative patients.

Conclusions

The results confirm a greater predisposition to the presence of ANA in patients with HCV, which may be associated with a worse prognosis, especially in the presence of the “rods and rings” cytoplasmic pattern.

The relevance between anti-rods/rings antibody and different treatment regimens in chronic hepatitis C virus infection

The antibodies and other issues associated with immunity in chronic hepatitis C virus (HCV) have been widely investigated, especially non-organ-specific antinuclear antibodies. Rods-rings (RR) antibody patterns are frequently observed due to pegylated IFN-α (PEG-IFN)/ribavirin (RBV) treatment by indirect immunofluorescence (IIF). We evaluated the relevance between anti-RR and PEG-IFN/RBV and/or direct-acting antiviral (DAA) regimens in chronic HCV. Sampling was done after achieving a sustained virological response (SVR) for 178 patients (aged >18 years). Patients were grouped according to treatment protocols (Group 1 [G1]: PEG-IFN/RBV [n = 53], Group 2 [G2]: PEG-IFN/RBV and Telaprevir or Boceprevir [n = 31], Group 3 [G3]: second- and third-wave DAA and previously received PEG-IFN/RBV (n = 38), and Group 4 [G4]: second- and third-wave DAA [n = 56]). Anti-RR was investigated by IIF (Euroimmun AG) test. Overall, 27 (15.16%) patients were anti-RR positive and received PEG-IFN/RBV. The numbers of anti-RR positivity for G1/2/3/4 (%) were 16/3/8/0 (30.2/9.6/21/0), respectively (p < .001). The anti-RR positivity rate for G1/2/3 was 22.13% (27/122, p = .088). Anti-RR was positive in 17.5% (11/63) of G1/2/3 patients who did not achieve SVR after the first treatment. This rate was 27.1% (16/59) in patients with SVR after the first treatment in G1/2 and there was no difference between these two classified groups in terms of antibody titers (p = .915). Anti-RR was detected up to 172 months after SVR. In summary, anti-RR was positive in high rates in patients receiving PEG-IFN/RBV therapy. Frequent monitoring is needed during patient follow-up to get more data on the relationship between anti-RR titer, treatment regimens, and SVR.

Acute severe autoimmune hepatitis with anti-rods and rings autoantibodies; literature first evidence

Autoimmune hepatitis (AIH) was defined as a progressive, chronic inflammatory autoimmune liver disease (ALD). The diagnosis of AIH requires the presence of characteristic clinical and laboratory features, and the exclusion of other clinical conditions that cause chronic hepatitis and cirrhosis. AIH can have an acute onset that mimics an acute viral or toxic hepatitis or an acute severe (fulminant, ASF) presentation that satisfies criteria for acute liver. Guidelines from the European Association for the Study of Liver Diseases define ALF with absence of pre-existing liver disease, acute onset of ≤ 26 weeks, coagulopathy (international normalised ratio (INR) ≥ 1.5), and presence of hepatic encephalopathy (HE). In recent years, autoantibodies (Aab) targeting subcellular structures described as the rods and rings (R&R) pattern in HEp-2 ANA have been presented as a unique and particular case of Aab generation. These R&R structures are composed of inosine monophosphate dehydrogenase type 2 (IMPDH2), and their formation can be induced in vitro by several small-molecule inhibitors. Aab targeting these relatively unknown structures has been observed in Hepatitis C virus (HCV) patients who have undergone treatment with pegylated interferona/ ribavirin (IFN/RBV) therapy. We presented and characterized a case patient with R&R and SMA Aab in AIH (ASF, fatal, without liver transplantation). To the best of our knowledge, this is the first evidence described in the Literature. Our early experience showed the R&R circulating Aab in one patient with Primary Biliary Cholangitis. This work now demonstrates that R&R Aab can also be present in AIH case.

Anti-rods/rings autoantibody and IMPDH filaments: an update after fifteen years of discovery

Autoantibodies to unknown subcellular rod and ring-shaped structures were first discovered in sera from hepatitis C patients in 2005. Early studies showed a strong association between these anti-rods/rings antibodies (anti-RR) and the standard of care interferon-α plus ribavirin combination therapy (IFN/RBV), suggesting that anti-RR are drug-induced autoantibodies. In the context of hepatitis C, anti-RR have been linked with relapse from or lack of response to IFN/RBV in some patient cohorts. However, examples of anti-RR in other diseases and healthy individuals have also been reported over the years, although anti-RR remains a rare autoantibody response in general. The advent of new direct-acting antiviral drugs for chronic hepatitis C and studies of anti-RR from different parts of the world are also beginning to change the perception of anti-RR. The nucleotide biosynthetic enzyme inosine monophosphate dehydrogenase (IMPDH) has been identified as the major autoantigen recognized by anti-RR. Coincidentally, the assembly of IMPDH into micron-scale rod and ring-shaped structures was discovered around the same time as anti-RR. Knowledge of the fundamental biological properties and cellular functions of these structures, referred to as "IMPDH filaments" by cell biologists, has advanced in parallel to anti-RR antibodies. Recent studies have revealed that IMPDH filament assembly is a mechanism to prevent feedback inhibition of IMPDH and is therefore important for the increased nucleotide production required in hyperproliferating cells, like activated T cells. Fifteen years later, we review the history and current knowledge in both the anti-RR autoantibody and IMPDH filament fields. TAKE-HOME MESSAGE: Anti-rods/rings are recognized as an example of a drug-induced autoantibody in hepatitis C patients treated with interferon and ribavirin, although new studies suggest anti-rods/rings may be detected in other contexts and may depend on unknown environmental or genetic factors in different populations. Recent data suggest that the assembly of IMPDH into rod and ring structures, the targets of anti-rods/rings autoantibody, is a mechanism for hyperproliferating cells, like activated T cells, to maintain increased guanine nucleotide levels to support rapid cell division.

Autoantibodies to intracellular "rods and rings" structures in two patients with autoimmune hepatitis treated with azathioprine

In vitro, inhibition of the synthesis of guanosine monophosphate (GMP) by various drugs such as ribavirin, acyclovir, azathioprine, and mycophenolic acid leads to the formation of subcellular structures in cultured cells. Autoantibodies targeting these cellular structures can be detected as "rods and rings" (RR) patterns by immunofluorescence. In vivo, autoantibodies to RR have been almost exclusively associated with hepatitis C virus patients treated with pegylated interferon-α and ribavirin. However, longitudinal data for other patient groups are scarce. Here, we reviewed 276 sequential immunofluorescence results from 127 patients with autoimmune hepatitis for the presence of RR patterns. Of 102 patients exposed to drugs known to induce RR in vitro, two patients under long-term azathioprine therapy were positive for this pattern. This is the first report of anti-RR in patients with autoimmune hepatitis and in patients treated with azathioprine.

Anti-rod and ring antibodies in patients with chronic hepatitis C using direct-acting antivirals

Anti-rods and rings (anti-RR) antibody induction is related to the combination of interferon and ribavirin in the treatment of hepatitis C virus (HCV) infection. If the main factor leading to this autoimmune reaction is the combination of these drugs, is not well known, but in vitro studies shows that ribavirin alone can induce rods and rings structures. New direct-acting antivirals (DAAs) permit HCV treatment without needing interferon but may be associated with ribavirin in the most difficult-to-treat patients. The aim of this study is to evaluate the occurrence of anti-RR in patients with chronic HCV infection, before and after 12 weeks of treatment with DAAs, with and without ribavirin. From Jun 2016 to Oct 2017, 52 HCV-infected patients were screened for anti-RR before and after DAA therapy, including sofosbuvir, daclatasvir, simeprevir, and ribavirin. Serum samples were analyzed using indirect immunofluorescence. The anti-RR was present in 11 (21%) of the 52 patients (51.9% male and mean age of 59.1 years) before using DAAs. All of them had been previously treated and previous exposed to interferon/ribavirin, with exposure time to ribavirin associated with the presence of anti-RR. After 12 weeks of DAA treatment, 3 patients (5.7%) developed the antibody in low titers, and two of them (66%) were interferon/ribavirin experienced. Only one of the 29 naïve patients (3.44%) developed anti-RR during the current treatment. Anti-RR was present in patients previously treated with interferon/ribavirin and can emerge after DAA treatment probably at a lower frequency than after interferon/ribavirin treatment.

IMP dehydrogenase rod/ring structures in acral melanomas

Acral lentiginous melanoma (ALM) is a rare subtype of melanoma with aggressive behavior. IMPDH enzyme, involved in de novo GTP biosynthesis, has been reported to assemble into large filamentary structures called rods/rings (RR) or cytoophidium (cellular snakes). RR assembly induces a hyperactive state in IMPDH, usually to supply a high demand for GTP nucleotides, such as in highly proliferative cells. We investigate whether aggressive melanoma tumor cells present IMPDH-based RR structures. Forty-five ALM paraffin-embedded tissue samples and 59 melanocytic nevi were probed with anti-IMPDH2 antibody. Both the rod- and ring-shaped RR could be observed, with higher frequency in ALM. ROC curve analyzing the proportions of RR-positive cells in ALM versus nevi yielded a 0.88 AUC. Using the cutoff of 5.5% RR-positive cells, there was a sensitivity of 80% and specificity of 85% for ALM diagnosis. In ALM, 36 (80%) showed RR frequency above the cutoff, being classified as RR-positive, compared with only 9 (15%) of the nevi (p < .001). Histopathology showed that 71% of the RR-positive specimens presented Breslow thickness > 4.0mm, compared with only 29% in the RR-low/negative (p = .039). We propose that screening for RR structures in biopsy specimens may be a valuable tool helping differentiate ALM from nevi and accessing tumor malignancy.

Long-term persistence of anti-rods and rings antibodies in patients with chronic hepatitis C after antiviral treatment

Anti-rods and rings (anti-RR) antibodies are related to hepatitis C virus (HCV) in patients treated with pegylated interferon (PEG-IFN) and ribavirin (RBV). Only RBV induces rods/rings structures in vitro; but in vivo, the antibody appearance is related to the combination of these drugs, because data about patients using just one of these drugs alone is missing. Some studies suggest disappearance of these antibodies over time. The aim of this study was to describe the occurrence of anti-RR in patients with chronic hepatitis C treatment-naïve or previously PEG-IFN/RBV-experienced, evaluating the persistence of anti-RR antibodies long after PEG-IFN/RBV treatment. From 2016 to 2017, 70 HCV-infected patients were screened for anti-RR using indirect immunofluorescence. Demographic and clinical data about previous treatments against HCV were assessed. Thirty-four patients (49%) had been previously treated with PEG-IFN/RBV and the average time since they had received the last antiviral treatment was 85.4 months. Anti-RR seropositivity was detected in 16 patients (23%), and all of these had used PEG-IFN/RBV (corresponding to 47% of experienced patients). Previous antiviral treatment and previous exposure time to RBV were associated with anti-RR positivity. Median time elapsed since last treatment was similar between anti-RR-positive and anti-RR-negative patients. Anti-RR seropositivity was not observed in treatment-naïve patients, but was detected in almost half of patients previously treated with PEG-IFN and RBV, even after a long period without exposure to these drugs. This antibody was related to extended prior exposure to ribavirin.

Association of Autoantibody to Rods and Rings with Hepatitis C Outcome and Viral Load

Despite the current availability of more potent drugs, hepatitis C virus (HCV) infection is still treated with a combination of IFN-α and ribavirin in many countries. Interferon/ribavirin therapy can induce the appearance of autoantibodies to Rods and Rings (anti-RR), which have been associated to a poorer prognosis. The aim of this study was to investigate the prevalence of anti-RR antibodies before and after ribavirin therapy and to look for a possible association with HCV infection outcome. In this context, anti-RR antibodies were detected by IFI on HEp-2 cells in 142 patients under ribavirin therapy (G1: 74 patients with a positive posttreatment HCV-PCR and G2: 68 patients with a negative posttreatment HCV-PCR, matched in age and gender), 84 kidney transplant recipients (KTRs) under mycophenolate and 158 controls (30 with systemic lupus erythematosus, 37 with rheumatoid arthritis, and 91 healthy blood donors). No patient had anti-RR antibody before IFN-α/ribavirin therapy, while 27 (19%) developed the anti-RR pattern under treatment. The anti-RR antibody was absent in all KTRs and the 158 controls. The frequency of anti-RR antibody was significantly higher in G1 (27; 36.48%) than in G2 (0), p < 0.001. Moreover, and in G1, anti-RR antibody was more frequent in nonresponders (NR) patients (23, 56.1%) than in relapsers (REL) (4, 12.1%); p < 0.001, OR [95%CI] = 9.26 [2.75-31.18]. Moreover, anti-RR antibody titer was significantly higher in NR patients (3,200 [1,600-6,400]) comparatively to REL patients (800 [500-1,400]), p = 0.002. Likewise, log of viral load postribavirin therapy was significantly higher in anti-RR positive patients (6.24 ± 0.64) than in anti-RR negative (4.69 ± 1.06), p < 0.001. Based on these findings, ribavirin-induced anti-RR autoantibody seems to be associated with a more frequent nonresponse to IFN-α/ribavirin therapy with a significant higher HCV viral load.

Long-term antiviral hepatitis C treatment associated with Rods and Ring Cytoplasmic antibodies

Aim

Clinical description of a patient diagnosed with chronic hepatitis C virus infection, which associated a rare anti-cytoplasmic pattern, known as “Rods and Ring”.

Method

Clinical case report.

Results

A 76-year old female patient with chronic hepatitis C virus infection under treatment for several months with pegylated Interferon-Ribavirin (started eight months ago) presented for clinical and biological evaluation of the therapeutic response.

Conclusion

This is the first reported clinical case of a patient with cytoplasmic filamentous rods and rings autoantibodies associated with chronic hepatis C from the Clinical Hospital IRGH Prof. Dr. O. Fodor Cluj-Napoca, Romania. The presence of these antibodies appears to be triggered by antiviral therapy. Although these are newly identified antibodies, they could be used as serological markers for detecting patients at risk of developing associated autoimmune pathologies or nonresponders to the antiviral therapy. Likewise, their detection could identify patients with occult hepatitis C infection.

Primary biliary cholangitis with contemporary presence of anti-mithocondrial and anti-rods and rings autoantibodies: literature first case

Primary biliary cholangitis, previously known as primary biliary cirrhosis (PBC), is the most common autoimmune diseases of the liver (ALD). Patients with PBC may present with typical biliary pattern symptoms. Also the presence of anti-mitochondrial autoantibodies (AMAs) is the laboratory hallmark of PBC, which molecular target antigens are members of 2-oxoacid dehydrogenase complex of enzymes. In recent years, autoantibodies (Aab) targeting subcellular structures described as the rods and rings (R&R) pattern in HEp-2 ANA have been presented as a unique and particular case of Aab generation. These R&R structures are composed of inosine monophosphate dehydrogenase type 2 (IMPDH2), and their formation can be induced in vitro by several small-molecule inhibitors. Aab targeting these relatively unknown structures have been almost exclusively observed in hepatitis C virus (HCV) patients who have undergone treatment with pegylated interferon-a/ribavirin (IFN/RBV) therapy. Literature showed that anti-RR Aab have not been found in no treatment-naïve HCV patients or in patients from any other disease. Now we present and characterized a case patient with contemporary presence of AMAs and R&R Aab in PBC, without any laboratory evidence of HCV and/or other hepatic virus infection. For our knowledge, this is the first case described in the Literature. R&R Aab in patients without any clinical/laboratory signs or symptoms of Hepatitis virus and without pharmacological therapy open the window to the alternative scenario: the association of these Aab to ALD. Our work demonstrated that R&R Aab can be present in PBC case. The interesting idea suggested that R&R Aab may be present also in AMA-negative PBC and they can considered a new possible diagnostic tool in this specific clinical condition. Other study and cases are needed but the presence of R&R Aab linked with AMAs and PBC may be explained by alterations in immune regulation caused by autoimmunity in a particular genetic background.

Ribavirin induces widespread accumulation of IMP dehydrogenase into rods/rings structures in multiple major mouse organs

Ribavirin (RBV) is a guanosine analogue triazole most commonly used in the treatment of chronic hepatitis C (HCV) infection. Although its mechanism of action is a matter of debate, several possibilities have been proposed, including depletion of guanine nucleotides through inhibition of inosine monophosphate dehydrogenase (IMPDH). IMPDH has been shown to assemble into micron-scale rod- and ring-shaped structures (rods/rings or RR), also called "IMPDH filaments," both in vitro and in vivo. Formation of RR structures can occur naturally, potentially to influence IMPDH activity, or when de novo guanosine monophosphate biosynthesis or IMPDH itself are inhibited by nutrient deprivation or drugs like RBV. Numerous studies have also reported the occurrence of autoantibodies targeting RR structures (anti-RR) in HCV patients previously treated or under treatment with interferon-α and ribavirin (IFN/RBV) combination therapy. For this brief study, we considered the strong association between RR autoantibodies and IFN/RBV treatment, and the lack of data assessing how RBV affects RR formation in a variety of tissues in vivo. First, RR structures formed in the spleen and pancreas of normal mice without any treatment. Then, in RBV-treated mice, we detected RR structures in a number of tissues, including stomach, liver, spleen, kidney, brain, skin, and cardiac and skeletal muscle. We made several intriguing observations: predominance of RR structures in the mucosa and submucosa layers of the stomach wall; a high proportion of RR-positive cells in the cerebral cortex, suggesting that RBV actually crosses the blood-brain barrier; and a higher ratio of rings to rods in the epidermis compared to the dermis layer of the skin. Screening for RR structures appears to be a useful method to track tissue penetration of RBV and the many RR-inducing drugs previously identified.

Immune Response-Dependent Assembly of IMP Dehydrogenase Filaments

Inosine monophosphate dehydrogenase (IMPDH) catalyzes the conversion of IMP to xanthosine monophosphate, the rate-limiting step in de novo guanosine monophosphate (GMP) synthesis. In cultured cells, IMPDH polymerizes into micron-scale filamentous structures when GMP synthesis is inhibited by depletion of purine precursors or by various drugs, including mycophenolic acid, ribavirin, and methotrexate. IMPDH filaments also spontaneously form in undifferentiated mouse embryonic stem cells and induced pluripotent stem cells, hinting they might function in various highly proliferative cell types. Therefore, we investigated IMPDH filament formation in human and murine T cells, which rely heavily on de novo guanine nucleotide synthesis to rapidly proliferate in response to antigenic challenge. We discovered extensive in vivo IMPDH filament formation in mature T cells, B cells, and other proliferating splenocytes of normal, adult B6 mice. Both cortical and medullary thymocytes in young and old mice also showed considerable assembly of IMPDH filaments. We then stimulated primary human peripheral blood mononuclear cells ex vivo with T cell mitogens phytohemagglutinin (PHA), concanavalin A (ConA), or antibodies to CD3 and CD28 for 72 h. We detected IMPDH filaments in 40–60% of T cells after activation compared to 0–10% of unstimulated T cells. Staining of activated T cells for the proliferation marker Ki-67 also showed an association between IMPDH filament formation and proliferation. Additionally, we transferred ovalbumin-specific CD4⁺ T cells from B6.OT-II mice into B6.Ly5a recipient mice, challenged these mice with ovalbumin, and harvested spleens 6 days later. In these spleens, we identified abundant IMPDH filaments in transferred T cells by immunofluorescence, indicating that IMPDH also polymerizes during in vivo antigen-specific T cell activation. Overall, our data indicate that IMPDH filament formation is a novel aspect of T cell activation and proliferation, and that filaments might be useful morphological markers for T cell activation. The data also suggest that in vivo IMPDH filament formation could be occurring in a variety of proliferating cell types throughout the body. We propose that T cell activation will be a valuable model for future experiments probing the molecular mechanisms that drive IMPDH polymerization, as well as how IMPDH filament formation affects cell function.

Autoantibodies to cytoplasmic rods and rings in patients with hepatitis C virus infection treated with direct-acting antivirals: The role of prior treatment with interferon plus ribavirin

INTRODUCTION

The cytoplasmic rods-rings (RR) pattern is found in hepatitis C (HCV) patients treated with interferon-ribavirin when studied with ANA-IIF. Ribavirin aggregates/induces antigenic changes in IMPDH-2, an enzyme necessary for ribavirin action.

PATIENTS AND METHOD

Prospective search for anti-RR autoantibodies (HEp-2, INOVA) in patients treated with direct-acting antivirals (DAAs) from October 2015 to June 2017. HCV-negative patients from up to June 2016 acted as controls. Anti-RR was analyzed at baseline and, mainly, during treatment and follow-up. The Chi-square test, Student's t-test and a logistic regression analysis were performed.

RESULTS

Between October 2015 and June 2016, 1258 men and 2389 women who were HCV-negative and 137 men and 112 women who were HCV-positive patients were studied. Approximately 22.9% of HCV-negative and 13.2% of HCV-positive were ANA-IIF-positive (p<0.05). Three HCV-negative (0.08%) and 23 (9.2%) HCV-positive patients had anti-RR (p<0.001). A total of 122 patients received DAAs; 30 received DAA+RBV; 46 pre-treated with IFN-RBV received DAA; 31 pre-treated with IFN-RBV received DAA+RBV; 16 received IFNpeg-RBV; and 24 received IFN-RBV-DAA. None of the 122 DAA-treated patients showed anti-RR; anti-RR were identified in 14.8% of those treated with DAA-RBV; in 25.9% of those pre-treated with IFN-RBV receiving DAA; in 22.2% of IFN-RBV-pre-treated patients who received DAA+RBV; in 7.4% of those treated with IFNpeg-RBV and in 29.6% of those treated with IFNpeg-RBV-DAA. The multivariate analysis showed significant associations between anti-RR and "Exposure to IFN" and "Time of exposure to RBV".

CONCLUSIONS

Anti-RR autoantibodies were detected only in patients with current or past treatments with RBV, even in cases in which only DAAs were later administered.

Reference standards for the detection of anti-mitochondrial and anti-rods/rings autoantibodies

Background:

Anti-mitochondrial antibodies (AMA) are found in >90% of primary biliary cholangitis patients. Anti-rods/rings antibodies (anti-RR) are most commonly associated with interferon-α and ribavirin treatment in hepatitis C patients. Clinical laboratories routinely screen for AMA and anti-RR using indirect immunofluorescence on HEp-2 cells (HEp-2-IFA). Therefore, we sought to establish reference materials for use in AMA and anti-RR testing.

Methods:

AMA-positive and anti-RR-positive human plasma samples (AMA-REF and RR-REF), identified as potential reference materials based on preliminary data, were further validated by multiple laboratories using HEp-2-IFA, immunoprecipitation (IP), western blotting, IP-western, line immunoassay (LIA), addressable laser bead immunoassay (ALBIA), and ELISA.

Results:

AMA-REF showed a strong positive cytoplasmic reticular/AMA staining pattern by HEp-2-IFA to ≥1:1280 dilution, and positive signal on rodent kidney/stomach/liver tissue. AMA-REF reacted with E2/E3, E3BP, E1α, and E1β subunits of the pyruvate dehydrogenase complex by IP and western blotting, and was positive for AMA antigens by LIA, ALBIA, and ELISA. RR-REF showed a strong positive rods and rings staining pattern by HEp-2-IFA to ≥1:1280 dilution. RR-REF reacted with inosine monophosphate dehydrogenase by IP, IP-western, and ALBIA. RR-REF also produced a nuclear homogenous staining pattern by HEp-2-IFA, immunoprecipitated proteins associated with anti-U1RNP antibody, and reacted weakly with histones, nucleosomes, Sm, and nRNP/Sm by LIA.

Conclusions:

AMA-REF and RR-REF are useful reference materials for academic or commercial clinical laboratories to calibrate and establish internal reference standards for immunodiagnostic assays. AMA-REF and RR-REF are now available for free distribution to qualified laboratories through Plasma Services Group.

Compositional complexity of rods and rings

Rods and rings (RRs) are large linear- or circular-shaped structures typically described as polymers of IMPDH (inosine monophosphate dehydrogenase). They have been observed across a wide variety of cell types and species and can be induced to form by inhibitors of IMPDH. RRs are thought to play a role in the regulation of de novo guanine nucleotide synthesis; however, the function and regulation of RRs is poorly understood. Here we show that the regulatory GTPase, ARL2, a subset of its binding partners, and several resident proteins at the endoplasmic reticulum (ER) also localize to RRs. We also have identified two new inducers of RR formation: AICAR and glucose deprivation. We demonstrate that RRs can be disassembled if guanine nucleotides can be generated by salvage synthesis regardless of the inducer. Finally, we show that there is an ordered addition of components as RRs mature, with IMPDH first forming aggregates, followed by ARL2, and only later calnexin, a marker of the ER. These findings suggest that RRs are considerably more complex than previously thought and that the function(s) of RRs may include involvement of a regulatory GTPase, its effectors, and potentially contacts with intracellular membranes.

Autoantibodies against "rods and rings"-related IMPDH2 in hepatitis C genotype 1 and DAA therapy in a "real life" cohort

Autoantibodies against inosine-5'-monophosphate-dehydrogenase-2 (IMPDH2; "rods and rings" pattern) develop in chronic hepatitis C (CHC) patients under treatment with peg-interferon (IFN) and ribavirin (RBV), an inhibitor of IMPDH2. We investigated the influence of the alternative therapy with direct-acting antivirals (DAA)/ribavirin on anti-IMPDH2 autoantibody generation and the use of anti-IMPDH2 development as a marker for therapy outcome (sustained virologic response, SVR). We analyzed a "real life" cohort of 104 unselected CHC genotype 1 (GT1) patients treated with IFN/first-generation DAA/RBV prospectively compared to a historic cohort of 59 IFN/RBV-treated CHC GT1 patients. First-generation DAA were boceprevir (BOC) or telaprevir (TPR). Serum autoantibodies were tested by indirect immunofluorescence (IFA) using recombinant IMPDH2 expressing HEK293 cells and native HEp2-cells as substrates. 64/163 (39%) CHC patients turned anti-IMPDH2 positive during therapy, but only 43/163 (26%) showed also "rods and rings" structures. 99/163 (61%) were tested as anti-IMPDH2 negative. 53/104 (51%) CHC patients undergoing IFN/DAA/RBV therapy were anti-IMPDH2 positive and 38/104 (37%) were in parallel anti-"rods and rings" positive. HCV clearance/SVR rate after IFN/DAA/RBV therapy and anti-IMPDH2 status were not significantly dependent. CHC GT1 patients treated with IFN/first-generation DAA/RBV developed anti-IMPDH2 autoantibodies comparable to previous studies including patients under IFN/RBV therapy. Anti-IMPDH2 titers show no use as a marker for therapy outcome in CHC GT1 patients.

De novo autoimmune hepatitis after liver transplantation: A focus on glutathione S-transferase theta 1

De novo autoimmune hepatitis (DAIH) is a rare clinical condition with features that resemble those of autoimmune hepatitis (AIH) in patients undergoing liver transplantation (LT) for nonautoimmune liver disease. The diagnosis of this entity has been based on the presence of biochemical and histological patterns similar to those observed in the primary AIH, although several considerations must be taken into account. The impact of DAIH on graft survival is relevant, and early diagnosis and treatment is associated with a good longterm outcome. Although glutathione S-transferase theta 1 (GSTT1) alloimmune recognition has been shown to be involved in the pathogenesis of DAIH, further studies are necessary to fully determine its pathogenic mechanisms and risk factors. We review the pathophysiology, the most common histological patterns, the treatment strategies, and the longterm outcomes of DAIH after LT with a special focus on GSTT1. Liver Transplantation 23:75-85 2017 AASLD.

The Presence of Autoantibodies to Cytoplasmic Rod and Ring Particles in the Serum of Patients with Chronic Hepatitis C Virus Infection

BACKGROUND

Chronic hepatitis C virus (HCV) is associated with extra hepatic autoimmune disorders, while peg-IFNa-2a/RBV combination therapy may exacerbate these conditions. Autoantibodies to cytoplasmic structures, called rod and ring particles (RR), have strong associations with these patients and are identified by HEp-2 cells.

OBJECTIVES

Our purpose was to study the correlation of autoantibodies to cytoplasmic rod and ring particles in the serum of patients with chronic HCV infection with their response to standard therapy.

METHODS

Serum samples were gathered from 120 patients with HCV infection (40 naive treatments, 40 with sustained virological response (SVR), and 40 with relapse response) during peg-IFNa-2a/RBV combination therapy and analyzed for the presence of RR antibodies by IIF on commercially available HEp-2 cell substrate slides from Euroimmun (Lu beck, Germany).

RESULTS

Anti-rod and ring (anti-RR) autoantibodies were detected in only the serum of 1 out of 120 patients (0.8%), which belonged to a patient (out of 40) with relapse response (2.5%). No correlation was found between the types of response to peg-IFNa-2a/RBV combination therapy and the presence of anti-RR autoantibodies.

CONCLUSIONS

The only HCV patient with RR autoantibodies previously had received IFN/ribavirin antiviral therapy. The presence of these autoantibodies is extremely rare in Iranian HCV patients. Further studies are warranted to determine the role of genetic background and geographical pattern in the prevalence of these novel autoantibodies worldwide.

Anti-rods/rings autoantibody seropositivity does not affect response to telaprevir treatment for chronic hepatitis C infection

PURPOSE

Autoantibodies to intracellular 'rods and rings' structures (anti-rods/rings or anti-RR) are strongly associated with hepatitis C (HCV) patients treated with interferon-α/ribavirin (IFN/RBV) and are linked with non-responsiveness to IFN/RBV or relapse, especially in Italian patients. This is the first study to determine whether there is any correlation of anti-RR with non-responsiveness to IFN/RBV treatment in patients also treated with telaprevir (TPV), one of several new therapies for chronic HCV recently implemented.

METHODS

From 2013 to 2014, 52 HCV-infected patients were treated with IFN/RBV and TPV at five Italian clinics. Patient sera were collected and analyzed by indirect immunofluorescence for the presence of anti-RR antibodies. Patients were classified as anti-RR positive or anti-RR negative, and then various biological and clinical variables were analyzed to compare the two groups, including gender, age, HCV genotype, previous IFN/RBV treatment, and IFN/RBV/TPV treatment outcome.

RESULTS

Of these 52 HCV patients treated with IFN/RBV/TPV, 10/32 (31%) who previously received IFN/RBV were anti-RR positive, compared to 0 of 20 treatment-naïve patients. Anti-RR-positive patients relapsed more than anti-RR-negative patients (3/10, 30% vs. 2/42, 5%; p < 0.05). However, zero anti-RR-positive patients were non-responsive, and frequencies of sustained virological response were similar (anti-RR positive: 7/10, 70% vs. anti-RR negative: 33/42, 79%).

CONCLUSIONS

Overall, the data suggest that anti-RR seropositivity is not associated with resistance to TPV treatment in this patient cohort, but monitoring anti-RR-positive patients for relapse within the first 6 months after treatment may be useful.

Differential capacity of therapeutic drugs to induce Rods/Rings structures in vitro and in vivo and generation of anti-Rods/Rings autoantibodies

Some HCV patients using ribavirin and interferon alpha (IFN-α) develop anti-rods and rings (RR) autoantibodies, the main target of which is inosine monophosphate dehydrogenase (IMPDH), the rate-determining enzyme in de novo GTP biosynthesis. In vitro inhibition of IMPDH by ribavirin induces RR formation. Here we investigate whether other commonly used drugs that interfere with GTP biosynthesis can induce RR structures in vitro and vivo and elicit generation of autoantibodies. HEp-2 cells treated for 24h with ribavirin, mycophenolic acid (MPA), azathioprine, methotrexate or acyclovir were positive for RR structures. However, adefovir, entecavir, tenofovir and lamivudine did not induce RR structures in these cells. Structures induced by ribavirin in HEp-2 cells are stable after 24h drug-washout, while structures induced by other drugs are relatively labile, disappearing within 2h. Looking at patients treated with these drugs, HCV patients treated with ribavirin (n=17) showed higher average percentage of RR-positive peripheral mononuclear cells than autoimmune patients treated with RR-inducing immunosuppressant drugs (n=21). Serum from 173 autoimmune patients who had been treated with MPA, azathioprine or methotrexate was tested for presence of anti-RR autoantibodies, and only one sample was found to be positive. Conversely, of 48 anti-RR autoantibody positive samples identified at Fleury Laboratories over 30months, 94% were from HCV patients treated with ribavirin plus IFN-α. These data indicate that RR structures can be induced by a variety of drugs in vitro and in vivo, but anti-RR autoantibody production is mostly restricted to HCV patients under ribavirin+IFN-α treatment.

'Rod and ring' formation from IMP dehydrogenase is regulated through the one-carbon metabolic pathway

'Rods and rings' (RRs) are conserved, non-membrane-bound intracellular polymeric structures composed, in part, of inosine monophosphate dehydrogenase (IMPDH), a key enzyme leading to GMP and GTP biosynthesis. RR formation is induced by IMPDH inhibitors as well as glutamine deprivation. They also form upon treatment of cells with glutamine synthetase inhibitors. We now report that depriving cells of serine and glycine promotes RR formation, and we have traced these effects to dihydrofolate reductase (DHFR) and serine hydroxymethyltransferase-2 (SHMT2), pivotal enzymes in one-carbon metabolism and nucleotide biosynthesis. RR assembly is likewise induced upon DHFR inhibition by methotrexate or aminopterin as well as siRNA-mediated knockdown of DHFR or SHMT2. Because RR assembly occurs when guanine nucleotide biosynthesis is inhibited, and because RRs rapidly disassemble after the addition of guanine nucleotide precursors, RR formation might be an adaptive homeostatic mechanism, allowing IMPDH to sense changes in the one-carbon folate pathway.

Report on the second International Consensus on ANA Pattern (ICAP) workshop in Dresden 2015

The second meeting for the International Consensus on Antinuclear antibody (ANA) Pattern (ICAP) was held on 22 September 2015, one day prior to the opening of the 12th Dresden Symposium on Autoantibodies in Dresden, Germany. The ultimate goal of ICAP is to promote harmonization and understanding of autoantibody nomenclature, and thereby optimizing ANA usage in patient care. The newly developed ICAP website www.ANApatterns.org was introduced to the more than 50 participants. This was followed by several presentations and discussions focusing on key issues including the two-tier classification of ANA patterns into competent-level versus expert-level, the consideration of how to report composite versus mixed ANA patterns, and the necessity for developing a consensus on how ANA results should be reported. The need to establish on-line training modules to help users gain competency in identifying ANA patterns was discussed as a future addition to the website. To advance the ICAP goal of promoting wider international participation, it was agreed that there should be a consolidated plan to translate consensus documents into other languages by recruiting help from members of the respective communities.

Anti-rods/rings autoantibody generation in hepatitis C patients during interferon-α/ribavirin therapy

Chronic inflammation associated with hepatitis C virus (HCV) infection can lead to disabling liver diseases with progression to liver cirrhosis and hepatocellular carcinoma. Despite the recent availability of more effective and less toxic therapeutic options, in most parts of the world the standard treatment consists of a weekly injection of pegylated interferon α (IFN-α) together with a daily dose of ribavirin. HCV patients frequently present circulating non-organ-specific autoantibodies demonstrating a variety of staining patterns in the indirect immunofluorescence assay for antinuclear antibodies (ANA). Between 20% to 40% of HCV patients treated with IFN-α and ribavirin develop autoantibodies showing a peculiar ANA pattern characterized as rods and rings (RR) structures. The aim of this article is to review the recent reports regarding RR structures and anti-rods/rings (anti-RR) autoantibody production by HCV patients after IFN-α/ribavirin treatment. Anti-RR autoantibodies first appear around the sixth month of treatment and reach a plateau around the twelfth month. After treatment completion, anti-RR titers decrease/disappear in half the patients and remain steady in the other half. Some studies have observed a higher frequency of anti-RR antibodies in relapsers, i.e., patients in which circulating virus reappears after initially successful therapy. The main target of anti-RR autoantibodies in HCV patients is inosine-5’-monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme involved in the guanosine triphosphate biosynthesis pathway. Ribavirin is a direct IMPDH2 inhibitor and is able to induce the formation of RR structures in vitro and in vivo. In conclusion, these observations led to the hypothesis that anti-RR autoantibody production is a human model of immunologic tolerance breakdown that allows us to explore the humoral autoimmune response from the beginning of the putative triggering event: exposure to ribavirin and interferon.

Clinical correlates of the "rods and rings" antinuclear antibody pattern

The "rods and rings" (RR) antinuclear antibody (ANA) pattern is believed to be restricted to hepatitis C virus (HCV) infection and related to the treatment. This is a 4-year retrospective study of all patients with RR pattern from the 20,000 serum samples received at the Hospital Universitari de Bellvitge for ANA testing. Two control groups with HCV patients without RR pattern: ANA-positive (n = 74) and ANA negative (n = 75) were included. Eighty-seven patients had samples with the RR pattern. Seventy-three were infected with HCV (prevalence of 15% in the HCV population). The RR pattern could not be related to ribavirin treatment, clinical status, biochemistry data, hepatic fibrosis, IL28B genotype, HCV genotype or the presence of autoantibodies related with autoimmune hepatitis. As 14 cases presented other diseases, mainly of autoimmune origin, the presence of RR antibodies may also be explained by alterations in immune regulation caused by autoimmunity or HCV in a particular genetic background.

Report of the First International Consensus on Standardized Nomenclature of Antinuclear Antibody HEp-2 Cell Patterns 2014-2015

During the 12th International Workshop on Autoantibodies and Autoimmunity held in Sao Paulo, Brazil, on August 28, 2014, a full day session was devoted to establishing a consensus on the nomenclature of staining patterns observed in the antinuclear antibody (ANA) indirect immunofluorescence test on HEp-2 cells. The current report summarizes the collective agreements with input from the host Brazilian and international communities that represented research, clinical, and diagnostic service laboratories. Patterns are categorized in three major groups (nuclear, cytoplasmic, and mitotic patterns) and each pattern has been defined and described in detail. The consensus nomenclature and representative patterns are made available online at the international consensus on antinuclear antibody pattern (ICAP) website (www.ANApatterns.org). To facilitate continuous improvement and input, specific comments on ICAP are encouraged and these will be discussed in subsequent ICAP meetings. The ultimate goal with the establishment of the ICAP is to promote harmonization and understanding of autoantibody test nomenclature, as well as interpretation guidelines for ANA testing, thereby optimizing usage in patient care.

Report of the First International Consensus on Standardized Nomenclature of Antinuclear Antibody HEp-2 Cell Patterns 2014-2015

During the 12th International Workshop on Autoantibodies and Autoimmunity held in Sao Paulo, Brazil, on August 28, 2014, a full day session was devoted to establishing a consensus on the nomenclature of staining patterns observed in the antinuclear antibody (ANA) indirect immunofluorescence test on HEp-2 cells. The current report summarizes the collective agreements with input from the host Brazilian and international communities that represented research, clinical, and diagnostic service laboratories. Patterns are categorized in three major groups (nuclear, cytoplasmic, and mitotic patterns) and each pattern has been defined and described in detail. The consensus nomenclature and representative patterns are made available online at the international consensus on antinuclear antibody pattern (ICAP) website (www.ANApatterns.org). To facilitate continuous improvement and input, specific comments on ICAP are encouraged and these will be discussed in subsequent ICAP meetings. The ultimate goal with the establishment of the ICAP is to promote harmonization and understanding of autoantibody test nomenclature, as well as interpretation guidelines for ANA testing, thereby optimizing usage in patient care.

Assembly of IMPDH2-based, CTPS-based, and mixed rod/ring structures is dependent on cell type and conditions of induction

Inhibition of guanosine triphosphate (GTP) and cytidine triphosphate (CTP) biosynthetic pathways induces cells to assemble rod/ring (RR) structures, also named cytoophidia, which consist of the enzymes cytidine triphosphate synthase (CTPS) and inosine-5'-monophosphate dehydrogenase 2 (IMPDH2). We aim to explore the interaction of CTPS and IMPDH2 in the generation of RR structures. HeLa and COS-7 cells were cultured in normal conditions or in the presence of 6-diazo-5-oxo-L-norleucine (DON), ribavirin, or mycophenolic acid (MPA). Over 90% of DON-treated cells presented RR structures. In HeLa cells, 35% of the RR structures were positive for IMPDH2 alone, 26% were CTPS alone, and 31% were IMPDH2/CTPS mixed, while in COS-7 cells, 42% of RR were IMPDH2 alone, 41% were CTPS alone, and 10% were IMPDH2/CTPS mixed. Ribavirin and MPA treatments induced only IMPDH2-based RR. Cells were also transfected with an N-terminal hemagglutinin (NHA)-tagged CTPS1 construct. Over 95% of NHA-CTPS1 transfected cells with DON treatment presented IMPDH2-based RR and almost 100% presented CTPS1-based RR; when treated with ribavirin, over 94% of transfected cells presented IMPDH2-based RR and 37% presented CTPS1-based RR, whereas 2% of untreated transfected cells presented IMPDH2-based RR and 28% presented CTPS1-based RR. These results may help in understanding the relationship between CTP and GTP biosynthetic pathways, especially concerning the formation of filamentous RR structures.

Anti-rods/rings: a human model of drug-induced autoantibody generation

In recent years, autoantibodies targeting subcellular structures described as the rods and rings pattern in HEp-2 ANA have been presented as a unique case of autoantibody generation. These rod and ring structures (RR) are at least partially composed of inosine monophosphate dehydrogenase type 2 (IMPDH2), and their formation can be induced in vitro by several small-molecule inhibitors, including some IMPDH2 inhibitors. Autoantibodies targeting these relatively unknown structures have been almost exclusively observed in hepatitis C virus (HCV) patients who have undergone treatment with pegylated interferon-α/ribavirin (IFN/RBV) combination therapy. To date, anti-RR antibodies have not been found in treatment-naïve HCV patients or in patients from any other disease groups, with few reported exceptions. Here, we describe recent advances in characterizing the RR structure and the strong association between anti-RR antibody response and HCV patients treated with IFN/RBV, detailing why anti-RR can be considered a human model of drug-induced autoantibody generation.

Microinjection of specific anti-IMPDH2 antibodies induces disassembly of cytoplasmic rods/rings that are primarily stationary and stable structures

BACKGROUND

Our laboratory previously reported interesting rods 3-10 μm long and rings 2-5 μm diameter (RR) in the cytoplasm of mammalian cells. Experimental evidence show that both inosine-5'-monophosphate dehydrogenase 2 (IMPDH2) and cytidine triphosphate synthetase (CTPS) are components of RR structures. Several cell types, including mouse embryonic stem cells, and cell lines, such as mouse 3 T3 and rat NRK, naturally present RR structures, while other cells can present RR when treated with compounds interfering with GTP/CTP biosynthetic pathways. In this study, we aimed to investigate the dynamic behavior of these RR in live cells.

RESULTS

RR were detected in >90% of COS-7 and HeLa cells treated with 1 mM ribavirin or 6-Diazo-5-oxo-L-norleucine (DON) for 24 h, and in 75% of COS-7 cells treated with 1 mM mycophenolic acid (MPA) for the same period of time. Microinjection of affinity-purified anti-IMPDH2 antibodies in live COS-7 cells treated with ribavirin, DON, or MPA showed mature forms of RR presented as stable and stationary structures in 71% of cells. In the remaining 29% of cells, RR acquired erratic movement and progressively disassembled into fragments and disappeared within 10 min. The specific stationary state and antibody-dependent disassembling of RR structures was independently confirmed in COS-7 and HeLa cells transfected with GFP-tagged IMPDH2.

CONCLUSIONS

This is the first demonstration of disassembly of RR structures upon microinjection of anti-IMPDH2 antibodies that led to the disappearance of the molecular aggregates. The disassembly of RR after microinjection of anti-IMPDH2 antibody further strengthens the notion that IMPDH2 are major building blocks of RR. Using two independent methods, this study demonstrated that the induced RR are primarily stationary structures in live cells and that IMPDH2 is a key component of RR.

Interferon-ribavirin therapy induces serum antibodies determining 'rods and rings' pattern in hepatitis C patients

A cytoplasmic antigen associated to inosine-5'-monophosphatedehydrogenase 2 eliciting specific antibodies (antirods and rings, RR) has been identified in patients with chronic hepatitis C who were exposed to pegylated interferon (PI) and ribavirin (RBV). The significance of anti-RR in these patients merits to be investigated. Sera from 88 chronic hepatitis C virus (HCV)-infected patients undergoing PI-RBV therapy were analysed for the presence of RR pattern by indirect immunofluorescence on HEp-2 substrate (Inova Diagnostics, San Diego, CA, USA). Anti-RR antibodies developed de novo in 32 patients independently of any demographic and virological feature, but with a significant association with cumulative exposure to PI-RBV (P = 0.0089; chi-square test). RR pattern was significantly more frequent in relapsers than in patients achieving sustained virological response (56% vs 30%; P = 0.0282, chi-square test). Anti-RR titre ranged from 1:80 to 1:1280, but significantly declined following treatment cessation. Anti-RR develop de novo in a substantial proportion of patients exposed to PI-RBV in relation to the duration of treatment exposure. Further investigations are necessary to unravel the mechanisms leading to the formation of these autoantibodies.

Induction of cytoplasmic pattern in the form of "rods and rings" through the treatment of hepatitis C: a case report

Female patient, complaining of weakness and pain in hypogastric, was admitted to the emergency department of the University Hospital of the West of Paraná (HUOP). During the interview reported treatment of chronic infection with hepatitis C virus (HCV) with peginterferon and ribavirin. Among the laboratory tests ordered, the search for self-antibodies against cellular antigens, traditionally known as antinuclear factor, showed fluorescence shaped like rods and/or rings in the cytoplasm of cells. This study attempts to clarify the relationship between this pattern not yet completely understood and the clinical picture of the patient. This pattern is characterized by 3-10 μm rods or rings with 2-5 μm in diameter scattered throughout the cytoplasm of the cell. Therefore, this new standard has been designated as "rods and rings" (RR). The antigenic target of this reaction was identified as inosine-5'-monophosphate dehydrogenase type 2 (IMPDH2) which is a key enzyme in the synthesis of purine nucleotides. The IMPDH2 enzyme aggregated or modified shaped RR in those patients treated with ribavirin may become antigenic and induce an autoimmune response. It is possible that interferon alpha stimulates the occurrence of anti-RR reactivity apparently induced by ribavirin. So far it is not known why the standard RR in HEp2 cells occurs only in a fraction of patients with HCV. Previous studies presented in this paper allow affirming that these antibodies associated with the standard RR are strongly related to hepatitis C. Moreover, it can be stated that the occurrence of anti-RR reactivity is promoted by combination therapy with interferon and ribavirin.

Temporal evolution of human autoantibody response to cytoplasmic rods and rings structure during anti-HCV therapy with ribavirin and interferon-α

Autoantibodies to inosine monophosphate dehydrogenase-2 (IMPDH2), an enzyme involved in de novo biosynthesis of guanine nucleotides, are observed in a subset of hepatitis C virus (HCV) patients receiving interferon alpha (IFN-α) plus ribavirin. Anti-IMPDH2 antibodies display a peculiar cytoplasmic "rod/ring" (RR) pattern in IIF-HEp-2. We examined the dynamics of anti-RR autoimmune response with respect to immunoglobulin isotypes, titer, avidity, and protein targets in 80 sequential samples from 15 HCV patients (plus 12 randomly selected anti-RR-positive, totalizing 92 samples) collected over an 18-month period, including samples collected before, during, and after IFN-α + ribavirin treatment. Immunoprecipitation showed reactivity with the 55 kDa IMPDH2 protein in 12/15 patients (80 %) and 11/15 (73 %) reacted with IMPDH2 in a sandwich ELISA. During treatment, anti-IMPDH2 autoantibodies hit their highest levels after 6-12 months of treatment and decreased post-treatment, while anti-HCV antibodies levels were stable over time. Anti-IMPDH2 IgM levels increased up until the sixth month of treatment and remained stable thereafter, while IgG levels increased steadily up to the twelfth month. Both IgG and IgM decreased during the post-treatment period. IgG avidity increased steadily up to the twelfth month of treatment. In conclusion, this study showed that the temporal kinetics of IFN-α + ribavirin-induced humoral autoimmune response to IMPDH2 exhibited a considerably delayed pace of increase in antibody levels and avidity as well as in isotype class switch in comparison with a conventional humoral response to infectious agents. These unique findings uncover intriguing differences between the autoimmune response and the immune response to exogenous agents in humans.

Glutamine deprivation initiates reversible assembly of mammalian rods and rings

Rods and rings (RR) are protein assemblies composed of cytidine triphosphate synthetase type 1 (CTPS1) and inosine monophosphate dehydrogenase type 2 (IMPDH2), key enzymes in CTP and GTP biosynthesis. Small-molecule inhibitors of CTPS1 or IMPDH2 induce RR assembly in various cancer cell lines within 15 min to hours. Since glutamine is an essential amide nitrogen donor in these nucleotide biosynthetic pathways, glutamine deprivation was examined to determine whether it leads to RR formation. HeLa cells cultured in normal conditions did not show RR, but after culturing in media lacking glutamine, short rods (<2 μm) assembled after 24 h, and longer rods (>5 μm) formed after 48 h. Upon supplementation with glutamine or guanosine, these RR underwent almost complete disassembly within 15 min. Inhibition of glutamine synthetase with methionine sulfoximine also increased RR assembly in cells deprived of glutamine. Taken together, our data support the hypothesis that CTP/GTP biosynthetic enzymes polymerize to form RR in response to a decreased intracellular level of glutamine. We speculate that rod and ring formation is an adaptive metabolic response linked to disruption of glutamine homeostasis.

Ultrastructure of cytoplasmic and nuclear inosine-5'-monophosphate dehydrogenase 2 "rods and rings" inclusions

Inosine-5'-monophosphate dehydrogenase catalyzes the critical step in the de novo synthesis of guanosine nucleotides: the oxidation of inosine monophosphate to xanthosine monophosphate. This reaction can be inhibited by specific inhibitors, such as ribavirin or mycophenolic acid, which are widely used in clinical treatment when required to inhibit the proliferation of viruses or cells. However, it was recently found that such an inhibition affects the cells, leading to a redistribution of IMPDH2 and the appearance of IMPDH2 inclusions in the cytoplasm. According to their shape, these inclusions have been termed "Rods and Rings" (R&R). In this work, we focused on the subcellular localization of IMPDH2 protein and the ultrastructure of R&R inclusions. Using microscopy and western blot analysis, we show the presence of nuclear IMPDH2 in human cells. We also show that the nuclear pool has an ability to form Rod structures after inhibition by ribavirin. Concerning the ultrastructure, we observed that R&R inclusions in cellulo correspond to the accumulation of fibrous material that is not surrounded by a biological membrane. The individual fibers are composed of regularly repeating subunits with a length of approximately 11 nm. Together, our findings describe the localization of IMPDH2 inside the nucleus of human cells as well as the ultrastructure of R&R inclusions.

Autoimmune features in metabolic liver disease: a single-center experience and review of the literature

Non-alcoholic steatohepatitis (NASH) is the progressive phenotype of non-alcoholic fatty liver disease associated with the metabolic syndrome. The existence of autoimmune features in NASH has been reported, but its significance remains unclear. We herein report the autoantibody profile of 54 patients with histologically proven NASH and further determined the development of autoimmunity in three different murine NASH models (monosodium glutamate, CDAA (choline-deficient L-amino acid-defined), and TSOD (Tsumura Suzuki, Obese Diabetes)) at 48 weeks of age. Forty-eight percent (26/54) of NASH cases were positive for antinuclear (ANA) or antimitochondrial antibody and manifested histological signs of overlap with autoimmune hepatitis and primary biliary cirrhosis, respectively. These patients were significantly older (60 ± 10 versus 50 ± 16 years), more frequently women (81 % versus 43 %), and with more severe portal inflammatory infiltrate compared with patients without autoimmunity. In one third of mice, regardless of the model, we observed a marked lymphoid infiltrate with non-suppurative cholangitis, and several cases were ANA-positive, but none AMA-positive. Our data suggest that autoimmunity may share some pathogenetic traits with the chronic inflammation of NASH, possibly related to advanced age.

Molecular cell biology and immunobiology of mammalian rod/ring structures

Nucleotide biosynthesis is a highly regulated process necessary for cell growth and replication. Cytoplasmic structures in mammalian cells, provisionally described as rods and rings (RR), were identified by human autoantibodies and recently shown to include two key enzymes of the CTP/GTP biosynthetic pathways, cytidine triphosphate synthetase (CTPS) and inosine monophosphate dehydrogenase (IMPDH). Several studies have described CTPS filaments in mammalian cells, Drosophila, yeast, and bacteria. Other studies have identified IMPDH filaments in mammalian cells. Similarities among these studies point to a common evolutionarily conserved cytoplasmic structure composed of a subset of nucleotide biosynthetic enzymes. These structures appear to be a conserved metabolic response to decreased intracellular GTP and/or CTP pools. Antibodies to RR were found to develop in some hepatitis C patients treated with interferon-α and ribavirin. Additionally, the presence of anti-RR antibodies was correlated with poor treatment outcome.

Development of a recombinant cell-based indirect immunofluorescence assay (RC-IFA) for the determination of autoantibodies against "rings and rods"-associated inosine-5'-monophosphate dehydrogenase 2 in viral hepatitis C

BACKGROUND AND AIMS

Autoantibodies against so-called "rings and rods" structures, as determined by indirect immunofluorescence assay (IFA) using the human cell line HEp-2, have been described in chronic hepatitis C virus (HCV) infected patients treated with interferon/ribavirin. Recently, cytidine triphosphate synthase (CTPS) and inosine-5'-monophosphate dehydrogenase 2 (IMPDH2), the enzyme inhibited by ribavirin, were proposed as the target antigens. We wanted to confirm the identification and setup a robust system for autoantibody testing in routine laboratories.

METHODS

CTPS and IMPDH2 were individually expressed in HEK293 cells and the recombinant cells were used in IFA (RC-IFA) to analyze sera from 33 anti-"rings and rods" antibody positive individuals with unknown diagnosis, 50 patients with chronic HCV infection, 100 with autoimmune hepatitis, 50 with primary biliary cirrhosis and 50 healthy blood donors.

RESULTS

We found that all sera with anti-"rings and rods" reacted with recombinant IMPDH2 but none with CTPS. In western blot or ELISA, anti-IMPDH2 positive sera reacted only weakly, if at all, with Escherichia coli derived recombinant IMPDH2 indicating that the autoantibody reaction probably depends on the 3-dimensional conformation of the antigen. A rabbit hyperimmune serum raised against bacterially expressed IMPDH2 produced the ring/rods pattern in IFA using HEp-2.

CONCLUSIONS

We conclude, that IMPDH2 is indeed the main target of anti-"rings and rods" while CTPS is an unlikely target. Moreover, the novel RC-IFA test system allows a standardized semi-quantitative determination of anti-IMPDH2 basing on a defined recombinant antigen.