Detection of polyreactive immunoglobulin G facilitates diagnosis in children with autoimmune hepatitis.

OBJECTIVE: The detection of autoantibodies is essential to diagnose autoimmune hepatitis (AIH). Particularly in children, specificity of autoantibodies decreases due to lower titers being diagnostic and being present not only in AIH but also in other liver diseases. Recently, quantification of polyreactive IgG (pIgG) for detection of adult AIH showed the highest overall accuracy compared to antinuclear antibodies (ANA), anti-smooth muscle antibodies (anti-SMA), anti-liver kidney microsomal antibodies (anti-LKM) and anti-soluble liver antigen/liver pancreas antibodies (anti-SLA/LP). We aimed to evaluate the diagnostic value of pIgG for pediatric AIH. DESIGN: pIgG, quantified using HIP1R/BSA coated ELISA, and immunofluorescence on rodent tissue sections were performed centrally. The diagnostic fidelity to diagnose AIH was compared to conventional autoantibodies of AIH in training and validation cohorts from a retrospective, European multi-center cohort from nine centers from eight European countries composed of existing biorepositories from expert centers (n = 285). RESULTS: IgG from pediatric AIH patients exhibited increased polyreactivity to multiple protein and non-protein substrates compared to non-AIH liver diseases and healthy children. pIgG had an AUC of 0.900 to distinguish AIH from non-AIH liver diseases. pIgG had a 31-73% higher specificity than ANA and anti-SMA and comparable sensitivity that was 6-20 times higher than of anti-SLA/LP, anti-LC1 and anti-LKM. pIgG had a 21-34% higher accuracy than conventional autoantibodies, was positive in 43-75% of children with AIH and normal IgG and independent from treatment response. CONCLUSION: Detecting pIgG improves the diagnostic evaluation of pediatric AIH compared to conventional autoantibodies, primarily owing to higher accuracy and specificity.

An open-label randomised-controlled trial of azathioprine vs. mycophenolate mofetil for the induction of remission in treatment-naive autoimmune hepatitis.

BACKGROUND & AIMS: Patients with autoimmune hepatitis (AIH) almost invariably require lifelong immunosuppressive treatment. There is genuine concern about the efficacy and tolerability of the current standard combination therapy of prednisolone and azathioprine. Mycophenolate mofetil (MMF) has emerged as an alternative option. The aim of this study was to compare MMF to azathioprine as induction therapy for AIH. METHODS: In this 24-week, prospective, randomised, open-label, multicentre superiority trial, 70 patients with treatment-naive AIH received either MMF or azathioprine, both in combination with prednisolone. The primary endpoint was biochemical remission defined as normalisation of serum levels of alanine aminotransferase and IgG after 24 weeks of treatment. Secondary endpoints included safety and tolerability. RESULTS: Seventy patients (mean 57.9 years [SD 14.0]; 72.9% female) were randomly assigned to the MMF plus prednisolone (n = 39) or azathioprine plus prednisolone (n = 31) group. The primary endpoint was met in 56.4% and 29.0% of patients assigned to the MMF group and the azathioprine group, respectively (difference, 27.4 percentage points; 95% CI 4.0 to 46.7; p = 0.022). The MMF group exhibited higher complete biochemical response rates at 6 months (72.2% vs. 32.3%; p = 0.004). No serious adverse events occurred in patients who received MMF (0%) but serious adverse events were reported in four patients who received azathioprine (12.9%) (p = 0.034). Two patients in the MMF group (5.1%) and eight patients in the azathioprine group (25.8%) discontinued treatment owing to adverse events or serious adverse events (p = 0.018). CONCLUSIONS: In patients with treatment-naive AIH, MMF with prednisolone led to a significantly higher rate of biochemical remission at 24 weeks compared to azathioprine combined with prednisolone. Azathioprine use was associated with more (serious) adverse events leading to cessation of treatment, suggesting superior tolerability of MMF. IMPACT AND IMPLICATIONS: This randomised-controlled trial directly compares azathioprine and mycophenolate mofetil, both in combination with prednisolone, for the induction of biochemical remission in treatment-naive patients with autoimmune hepatitis. Achieving complete remission is desirable to prevent disease progression. Patients assigned to the mycophenolate mofetil group reached biochemical remission more often and experienced fewer adverse events. The findings in this trial may contribute to the re-evaluation of international guidelines for the standard of care in treatment-naive patients with autoimmune hepatitis. TRIAL REGISTRATION NUMBER: #NCT02900443.

Assessing the efficacy and safety of mycophenolate mofetil versus azathioprine in patients with autoimmune hepatitis (CAMARO trial): study protocol for a randomised controlled trial.

BACKGROUND: Currently, the standard therapy for autoimmune hepatitis (AIH) consists of a combination of prednisolone and azathioprine. However, 15% of patients are intolerant to azathioprine which necessitates cessation of azathioprine or changes in therapy. In addition, not all patients achieve complete biochemical response (CR). Uncontrolled data indicate that mycophenolate mofetil (MMF) can induce CR in a majority of patients. Better understanding of first-line treatment and robust evidence from randomised clinical trials are needed. The aim of this study was to explore the potential benefits of MMF as compared to azathioprine, both combined with prednisolone, as induction therapy in a randomised controlled trial in patients with treatment-naive AIH. METHODS: CAMARO is a randomised (1:1), open-label, parallel-group, multicentre superiority trial. All patients with AIH are screened for eligibility. Seventy adult patients with AIH from fourteen centres in the Netherlands and Belgium will be randomised to receive MMF or azathioprine. Both treatment arms will start with prednisolone as induction therapy. The primary outcome is biochemical remission, defined as serum levels of alanine aminotransferase and immunoglobulin G below the upper limit of normal. Secondary outcomes include safety and tolerability of MMF and azathioprine, time to remission, changes in Model For End-Stage Liver Disease (MELD)-score, adverse events, and aspects of quality of life. The study period will last for 24 weeks. DISCUSSION: The CAMARO trial investigates whether treatment with MMF and prednisolone increases the proportion of patients in remission compared with azathioprine and prednisolone as the current standard treatment strategy. In addition, we reflect on the challenges of conducting a randomized trial in rare diseases. TRIAL REGISTRATION: EudraCT 2016-001038-91 . Prospectively registered on 18 April 2016.

Systematic review of response criteria and endpoints in autoimmune hepatitis by the International Autoimmune Hepatitis Group.

BACKGROUND & AIMS: Autoimmune hepatitis (AIH) has been well characterised and codified through the development of diagnostic criteria. These criteria have been adapted and simplified and are widely used in clinical practice. However, there is a need to update and precisely define the criteria for both treatment response and treatment. METHODS: A systematic review was performed and a modified Delphi consensus process was used to identify and redefine the response criteria in autoimmune hepatitis. RESULTS: The consensus process initiated by the International Autoimmune Hepatitis Group proposes that the term 'complete biochemical response' defined as 'normalization of serum transaminases and IgG below the upper limit of normal' be adopted to include a time point at 6 months after initiation of treatment. An insufficient response by 6 months was a failure to meet the above definition. Non-response was defined as '<50% decrease of serum transaminases within 4 weeks after initiation of treatment'. Remission is defined as liver histology with a Hepatitis Activity Index <4/18. Intolerance to treatment was agreed to stand for 'any adverse event possibly related to treatment leading to potential drug discontinuation'. CONCLUSIONS: These definitions provide a simple and reproducible framework to define treatment response and non-response, irrespective of the therapeutic intervention. A consensus on endpoints is urgently required to set a global standard for the reporting of study results and to enable inter-study comparisons. Future prospective database studies are needed to validate these endpoints. LAY SUMMARY: Consensus among international experts on response criteria and endpoints in autoimmune hepatitis is lacking. A consensus on endpoints is urgently required to set a global standard for the reporting of study results and to enable the comparison of results between clinical trials. Therefore, the International Autoimmune Hepatitis Group (IAIHG) herein presents a statement on 5 agreed response criteria and endpoints: complete biochemical response, insufficient response, non-response, remission, and intolerance to treatment, which can be used to guide future reporting.

Quantification of polyreactive immunoglobulin G facilitates the diagnosis of autoimmune hepatitis.

BACKGROUND AND AIMS: Detection of autoantibodies is a mainstay of diagnosing autoimmune hepatitis (AIH). However, conventional autoantibodies for the workup of AIH lack either sensitivity or specificity, leading to substantial diagnostic uncertainty. We aimed to identify more accurate serological markers of AIH with a protein macroarray. APPROACH AND RESULTS: During the search for more-precise autoantibodies to distinguish AIH from non-AIH liver diseases (non-AIH-LD), IgG antibodies with binding capacities to many human and foreign proteins were identified with a protein macroarray and confirmed with solid-phase ELISAs in AIH patients. Subsequently, polyreactive IgG (pIgG) was exemplarily quantified by reactivity against human huntingtin-interacting protein 1-related protein in bovine serum albumin blocked ELISA (HIP1R/BSA). The diagnostic fidelity of HIP1R/BSA binding pIgG to diagnose AIH was assessed in a retrospective training, a retrospective multicenter validation, and a prospective validation cohort in cryoconserved samples from 1,568 adults from 10 centers from eight countries. Reactivity against HIP1R/BSA had a 25% and 14% higher specificity to diagnose AIH than conventional antinuclear and antismooth muscle antibodies, a significantly higher sensitivity than liver kidney microsomal antibodies and antisoluble liver antigen/liver pancreas antigen, and a 12%-20% higher accuracy than conventional autoantibodies. Importantly, HIP1R/BSA reactivity was present in up to 88% of patients with seronegative AIH and in up to 71% of AIH patients with normal IgG levels. Under therapy, pIgG returns to background levels of non-AIH-LD. CONCLUSIONS: pIgG could be used as a promising marker to improve the diagnostic workup of liver diseases with a higher specificity for AIH compared to conventional autoantibodies and a utility in autoantibody-negative AIH. Likewise, pIgG could be a major source of assay interference in untreated AIH.

Histological activity despite normal ALT and IgG serum levels in patients with autoimmune hepatitis and cirrhosis.

BACKGROUND & AIMS: In autoimmune hepatitis (AIH), normal levels of transaminases and IgG define biochemical remission and are considered the best surrogate markers for histological remission. This study assessed whether this also applies to patients with AIH cirrhosis. METHODS: In this European multicentric study, we included 125 biopsies from 113 patients with AIH and histologically proven cirrhosis; 105 biopsies from 104 patients with AIH without cirrhosis served as controls. Biochemical parameters were available within 4 weeks of biopsy. AIH activity was graded according to the modified Hepatitis Activity Index (mHAI), with mHAI ≥4/18 considered to indicate risk of disease progression. RESULTS: In total, 47 out of 125 liver biopsies were obtained from patients with AIH cirrhosis and normal ALT levels at time of biopsy. Only 26% (12/47) of those livers showed histological remission (mHAI <4/18), whereas 36% (17/47) showed moderate to high histological activity (mHAI ≥6/18). In patients with noncirrhotic AIH, 88% (46/52 biopsies) of cases with normal ALT levels had histological remission and only 4% (2/52) had an mHAI ≥6/18 (p <0.001). The addition of IgG to define complete biochemical remission only slightly improved the association with histological remission in the limited number of patients with AIH cirrhosis available for analysis [29% (5/17) of biopsies with mHAI <4/18]. ALT correlated closely with mHAI in AIH without cirrhosis but poorly in AIH with cirrhosis. CONCLUSIONS: In contrast to patients with noncirrhotic AIH, in patients with AIH cirrhosis, who are at risk of disease progression, normal ALT levels and potentially also complete biochemical remission are poor surrogate markers of histological remission. Thus, new biomarkers are needed to monitor disease activity and progression in patients with AIH cirrhosis. LAY SUMMARY: Autoimmune hepatitis (AIH) is an inflammatory disease of the liver that usually responds to immunosuppressive therapy. Serum transaminases and IgG levels within the normal ranges define complete biochemical remission and are considered as surrogate markers for histological disease activity. Here, we show that those biochemical markers are not sufficient to indicate low disease activity in patients with AIH and already established cirrhosis. Consequently, until better biomarkers for disease activity are found, only liver biopsy can reliably indicate disease activity in the presence of cirrhosis. Additional investigations, such as measurements of liver stiffness, should be undertaken to monitor non-invasively for disease progression in patients with AIH and established cirrhosis.

High discontinuation rate of azathioprine in autoimmune hepatitis, independent of time of treatment initiation.

BACKGROUND: Guidelines regarding treatment for autoimmune hepatitis (AIH) favour two strategies for azathioprine (AZA) introduction: concurrent with steroids at induction or delayed by 2-4 weeks. The safety and efficacy of both strategies have been unexplored. METHODS: We established a cohort of 900 AIH patients from 12 centres in 7 European countries. There were 631 patients who used AZA as part of the therapeutic regimen. We distinguished two groups: patients with early AZA (<2 weeks) or delayed AZA initiation (≥2 weeks). Primary outcome was discontinuation of AZA in the first year of treatment. Cox regression and propensity score matching was performed to determine difference in outcomes between groups. RESULTS: Patients with early AZA initiation had significantly lower transaminases and bilirubin at baseline. Discontinuation rates of AZA did not differ between early and delayed starters (16.6% vs 14.2%), which did not reach statistical significance (hazard ratio 0.97, 95% confidence interval 0.61-1.55, P = .90). Stratification according to baseline disease activity or propensity score matching did not alter the results. Main reason for AZA discontinuation was intolerance to treatment (14.0% vs 13.2%, P = .78) with nausea and vomiting as main side effects. AIH remission rates were comparable among groups. CONCLUSION: The discontinuation rate of AZA in AIH treatment is ~15% in the first year of treatment. Early or delayed AZA initiation does not differ in remission and discontinuation rates in AIH induction therapy. Our data suggest that either strategy may be used as part of AIH treatment.

Features and outcome of AIH patients without elevation of IgG.

BACKGROUND & AIMS: High IgG levels are considered a hallmark of autoimmune hepatitis (AIH). A subgroup of patients with AIH has IgG within the normal range despite evidence of clinical disease activity. The clinical significance of this biomarker has not been explored. METHODS: In a European multicentre study we compared biochemical, clinical and histological features from patients with AIH and normal IgG-values at diagnosis to an age- and sex-matched control group of patients with typical AIH presenting with elevated IgG. Data were assessed at diagnosis, after 12 months of therapy and at last follow-up. RESULTS: Out of 1,318 patients with AIH, 130 (10%) had normal IgG at presentation. Histological and biochemical parameters at diagnosis, as well as treatment response, showed no difference between groups. Stable remission off treatment was achieved more commonly in the normal IgG group than in the typical AIH group (24 vs. 8%; p = 0.0012). Patients of the control group not only had higher IgG levels (29.5 ± 5.8 vs. 12.5 ± 3.2 g/L; p <0.0001), but also a higher IgG/IgA ratio (9.3 ± 6.9 vs. 5.4 ± 2.4; p <0.0001) at diagnosis. The IgG/IgA ratio only declined in patients with typical AIH and was no longer different between groups after 12 months (6.3 ± 4.3 vs. 5.5 ± 2.2; p = 0.1), indicating a selective increase of IgG in typical AIH and its suppression by immunosuppression. Autoantibody titres were higher in the typical AIH group, but not when controlled for IgG levels. CONCLUSIONS: Compared to AIH with typical biochemical features, patients with normal IgG levels at diagnosis (i) show similar biochemical, serological and histological features and comparable treatment response, (ii) appear to lack the selective elevation of serum IgG levels observed in typical active AIH disease, (iii) may represent a subgroup with a higher chance of successful drug withdrawal. LAY SUMMARY: A characteristic feature of autoimmune hepatitis (AIH) is an elevation of immunoglobulin G (IgG), which is therefore used as a major diagnostic criterion, as well as to monitor treatment response. Nevertheless, normal IgG does not preclude the diagnosis of AIH. Therefore, we herein assessed the features of patients with AIH and normal IgG in a large multicentre study. This study demonstrates that about 10% of all patients with AIH have normal IgG; these patients are indistinguishable from other patients with AIH with respect to biochemical markers, liver histology, disease severity and treatment response, but might represent a subgroup with a higher chance of remission after drug withdrawal.

Profiling the patient with autoimmune hepatitis on calcineurin inhibitors: a real-world-experience.

OBJECTIVE: Therapy for autoimmune hepatitis (AIH) consists of steroid induction therapy, followed by maintenance therapy with azathioprine. However, up to 20% of patients experience either insufficient response or intolerance on first-line therapy. Calcineurin inhibitors (CNIs) are frequently used when first-line therapy fails. Although a number of studies report on efficacy, less is known on the patient trajectory before switch to CNIs. Our aim was to describe the road toward CNI therapy in AIH patients. METHODS: Patients with an AIH diagnosis who used CNIs as either second- or third-line treatment were included in the study. Reason for switch to CNI was assessed as either an insufficient response or intolerance to prior therapy. Efficacy was assessed by normalization of transaminases at last moment of follow-up. RESULTS: Final analysis included 20 patients who were treated with CNIs. Ten patients were treated with tacrolimus and ten patients received cyclosporine. In patients who used CNI treatment as third-line therapy (n = 13), duration of first-line therapy was almost twice as long as duration of second-line therapy (2.58 years vs. 1.33 years; P = 0.67). Patients treated with tacrolimus had relatively high trough levels (7.6 ng/mL) and more (minor) adverse events. Fifty-five percent of patients had normalization of transaminases at last moment of follow-up. CONCLUSION: CNI treatment in AIH as second- or third-line therapy is effective in ~50% of patients. The trajectory before switch varies considerably between patients.

Rapid Response to Treatment of Autoimmune Hepatitis Associated With Remission at 6 and 12 Months.

BACKGROUND & AIMS: Changes in serum levels of transaminases immediately after initiation of treatment for autoimmune hepatitis (AIH) might be associated with biochemical markers of remission and liver-related events. We assessed the outcomes of patients with vs without rapid response to treatment of AIH in a large international cohort. METHODS: We performed a retrospective cohort study, collecting data from 2 independent cohorts of adults with AIH from 12 centers in 7 countries in Europe. We collected information on patient demographics; serologic, histologic, and biochemical analyses; and treatment. We used a receiver operating characteristic curve and Youden index to calculate the optimal percentage decrease in level of aspartate aminotransferase (AST) after 8 weeks of treatment that associated with normalization of transaminase levels after 26 weeks of treatment with predniso(lo)ne (primary outcome) in the first (discovery) cohort (n = 370). We evaluated the results in the second (validation) cohort (n = 370). Secondary outcomes were liver-related death or transplantation. We performed univariate and multivariable logistic and Cox regression with correction for confounders. RESULTS: A significant decrease in level of AST after 8 weeks of treatment was significantly associated with normalization of transaminase levels at 26 and 52 weeks (P < .001); a decrease of more than 80% in level of AST was associated with optimal normalization. In both cohorts, rapid responders (≥80% decrease in level of AST after 8 weeks) were more likely to achieve normalization of transaminases at 26 and 52 weeks when compared to non-rapid responders. Rapid responders in the discovery cohort had lower risk of liver-related death or transplantation (adjusted hazard ratio 0.18; 95% CI 0.05-0.63; P = .007), although this was not confirmed in the validation cohort. Results from measurement of alanine aminotransferase did not differ significantly from those of AST for the primary outcome. Slow responders (without normalization of transaminases after 1 year) had the highest risk of liver transplantation or liver-related death. CONCLUSIONS: In a retrospective study of patients with AIH, we found that a rapid response to treatment, based on level of AST after 8 weeks, associates with normalization of transaminase levels in the following year. Patients with a rapid response also have a lower risk of liver-related death or transplantation than patients without this rapid response.

Clinical management of autoimmune hepatitis.

Autoimmune hepatitis is a rare and chronic liver disease that is characterised by increased serum transaminases and immunoglobulin G, inflammatory liver histology and presence of circulating autoantibodies. An autoimmune hepatitis diagnosis justifies life-long treatment in most patients in order to prevent development of cirrhosis and end-stage liver disease. The cornerstone of treatment is steroid induction therapy followed by maintenance therapy with azathioprine, which is effective in most cases. For patients who do not respond to standard treatment, second-line treatment with other immunosuppressants can be effective. Treatment should be aimed at biochemical remission of the disease, which is defined as normalization of transaminases and immunoglobulin G. Patients should be monitored intensively during the first months of treatment in order to monitor side-effects, assess symptoms and individualise treatment. Specialist consultation should be sought in difficult-to-treat patients. Future studies and networking initiatives should result in optimization of current treatment strategies in autoimmune hepatitis.

Predniso(lo)ne Dosage and Chance of Remission in Patients With Autoimmune Hepatitis.

BACKGROUND & AIMS: Patients with autoimmune hepatitis (AIH) commonly receive induction therapy with predniso(lo)ne followed by maintenance therapy with azathioprine. European Association for Study of the Liver clinical practice guidelines advise a predniso(lo)ne dose range of 0.50-1 mg/kg/day, which leaves room for practice variation. We performed a multicenter study to determine the efficacy of different dose ranges of predniso(lo)ne induction therapy in a large European cohort of patients with AIH. METHODS: We performed a retrospective cohort study using a comparative effectiveness design. We collected data from 451 adults with AIH who began treatment from 1978 through 2017 at 9 centers in 5 European countries. We assigned patients to a high-dose group (initial predniso(lo)ne dose ≥0.50 mg/kg/day; n = 281) or a low-dose group (<0.50 mg/kg/day; n = 170). Logistic regression was performed to determine difference in outcomes between the groups. The primary outcome was normal serum levels of transaminases at 6 months after initiation of therapy. RESULTS: There was no significant difference in rates of normalization of transaminases between the high-dose predniso(lo)ne group and the low-dose group (70.5% vs 64.7%; P = .20). After multivariable logistic regression with correction for confounders, there was no difference in the likelihood of normalization of transaminases between the groups (odds ratio, 1.21; 95% CI, 0.78-1.87; P = .38). Patients given an initial high dose of predniso(lo)ne received more predniso(lo)ne over time than patients started on a lower dose (median doses over 6 months: 3780 mg vs 2573 mg) (P < .01). CONCLUSIONS: In a retrospective study of patients with AIH in Europe, we found that the dose of predniso(lo)ne to induce remission in patients with AIH is less relevant than assumed. An initial predniso(lo)ne dose below 0.50 mg/kg/day substantially decreases unnecessary exposure to predniso(lo)ne in patients with AIH.

Reasons why the diagnosis of serrated polyposis syndrome is missed.

OBJECTIVES: Serrated polyposis syndrome (SPS) is a relatively new and under-recognized colorectal cancer (CRC) predisposition syndrome. Previous studies have reported miss-rates of SPS diagnosis varying from 40 to 82%. As SPS patients and their first-degree relatives have an increased risk of CRC, early recognition is important. We aimed to determine the miss-rate of SPS and to determine the reasons for missed diagnosis. PATIENTS AND METHODS: We retrospectively identified all patients diagnosed with at least one colorectal polyp or carcinoma detected at our tertiary referral center between January 1986 and July 2013 using the nationwide pathology registry. On the basis of cumulative polyp count with size and location, SPS patients were identified. We checked whether the SPS diagnosis was made in the medical files and, if not, what might have been the reason for missing the diagnosis. RESULTS: We randomly assessed 5000 patients, of whom 25 patients fulfilled the WHO criteria for SPS. In six patients, no previous SPS diagnosis had been made, leading to a miss-rate of 24.0% (95% confidence interval: 7.3-40.7). The reasons for missed diagnosis were polyps removed before establishment of the WHO criteria, unavailable pathology reports, and failure to apply the criteria by the clinician. CONCLUSION: The miss-rate for the diagnosis of SPS is considerable, even during longer follow-up with repeated colonoscopies. A preventable reason for missing SPS cases is failure to apply the WHO criteria. Awareness of this CRC predisposition syndrome needs to be raised to decrease the miss-rate of SPS.

An in Situ Generated Palladium on Aluminum Oxide: Applications in Gram-Scale Matsuda-Heck Reactions.

In situ generated palladium on aluminum oxide provides an active catalytic system for Matsuda-Heck reactions in gram-scale. The novel catalyst proceeded through a significantly higher catalytic activity compared to the classical Pd/C system. Based on the high catalytic activity the first α,ß,ß-triarylation of methyl acrylate in good yields could be provided in one-step.

Iron Trichloride and Air Mediated Guanylation of Acylthioureas. An Ecological Route to Acylguanidines: Scope and Mechanistic Insights.

Recently we introduced iron trichloride as an environmentally benign and cost-efficient reagent for the synthesis of N-benzoylguanidines. This highly attractive synthetic approach grants access to a broad spectrum of N-benzoylguanidines under mild conditions in short reaction times. In this work we present an extended scope of our methodology along with the results obtained from mechanistic studies via in situ IR spectroscopy in combination with LC (liquid chromatography)-MS analyses. On the basis of these new mechanistic insights we were able to optimize the synthetic protocol and to develop an alternative mechanistic proposal. In this context the symbiotic roles of iron trichloride and oxygen in the guanylation process are highlighted.