Treatment of hepatitis C-virus-related glomerulonephritis

Potential role of ACE2-related microRNAs in COVID-19-associated nephropathy

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for coronavirus disease (COVID-19), potentially have severe kidney adverse effects. This organ expressed angiotensin-converting enzyme 2 (ACE2), the transmembrane protein which facilitate the entering of the virus into the cell. Therefore, early detection of the kidney manifestations of COVID-19 is crucial. Previous studies showed ACE2 role in various indications of this disease, especially in kidney effects. The MicroRNAs (miRNAs) in this organ affected ACE2 expression. Therefore, this review aims at summarizing the literature of a novel miRNA-based therapy and its potential applications in COVID-19-associated nephropathy. Furthermore, previous studies were analyzed for the kidney manifestations of COVID-19 and the miRNAs role that were published on the online databases, namely MEDLINE (PubMed) and Scopus. Several miRNAs, particularly miR-18 (which was upregulated in nephropathy), played a crucial role in ACE2 expression. Therefore, the antimiR-18 roles were summarized in various primate models that aided in developing the therapy for ACE2 related diseases.

Infection-Related Glomerulonephritis

Acute postinfectious glomerulonephritis or infection-related glomerulonephritis has been associated with several viral or bacterial infections. Group A beta-hemolytic streptococcal infection is the prototypical cause of postinfectious glomerulonephritis and the main focus of this discussion. The clinical spectrum can vary widely, from asymptomatic microscopic hematuria incidentally detected on routine urinalysis to rapidly progressive glomerulonephritis with acute kidney injury requiring emergent dialysis. Other important causes include glomerulonephritis associated with endocarditis and ventriculoatrial shunt infections. Multiple renal pathologic conditions have been associated with hepatitis B and C infections.

Infection-Induced Kidney Diseases

Infection induced kidney diseases are of concern for clinicians because timely detection and treatment of infections may cure or limit the extent of injury inflicted by microorganisms causing the infections. Infections can cause kidney injury by either direct invasion, or indirectly by immune mediated mechanisms, which manifest as post-infectious glomerulonephritis, or infection-related glomerulonephritis. Clinical manifestations may be acute or chronic depending on the microorganisms, endemic/epidemic nature and source of infection. All microbials virus, bacteria, mycobacteria, fungus, and protozoa have been implicated in kidney diseases either causing direct kidney injuries or immune-mediated injuries. Infection control practices in large parts of world is limited by poverty, social behavior, high population density, deforestation, inadequate access to safe drinking water, and poor health care facilities. Although, antimicrobials and vaccinations have successfully eradicated and cured many infectious diseases; however injudicious antimicrobial use and emergence of resistant organisms complicated the disease severity like secondary renal amyloidosis with chronic persistent infection. Re-emergence of various infections has been a recent pattern in developed world leading to uncertain diagnostic challenges, and association with kidney diseases.

Hepatitis C-related cryoglobulinemic neuropathy: potential role of oxcarbazepine for pain control

BACKGROUND

Peripheral neuropathy is one most common, limiting and invalidating neurological symptom in subjects with hepatitis C virus and mixed cryoglobulinemia. Notably, the medical therapy proposed to eradicate HCV, can frequently exacerbate the painful neuropathy. Therefore, neuropathy therapies are insufficient and inadequate, and comprise immunosuppressive drugs, such as steroid or cyclosporine, intravenous immunoglobulin or plasma exchange. These have shown variable success in case reports, with a presumably temporary effect, but with major side effects.

METHODS

We assessed the effects of oxcarbazepine treatment in 67 cases of cryoglobulinemia related neuropathy, who did not respond to either steroid or Gabapentin, or Pregabalin. Oxcarbazepine was chosen based on the promising preliminary results.

RESULTS

Patients treated with Oxcarbazepine showed a rapid, discrete and persistent relief of polyneuropathic signs, without consistent side effects, and with a limited interaction with concomitant drugs.

CONCLUSIONS

These data favor the use of oxcarbazepine as a useful tool in the management of neuropathic pain associated with Hepatitis-C cryoglobulin neuropathy.

Interferon Therapy for HCV-Associated Glomerulonephritis: Meta-Analysis of Controlled Trials

Background

A relationship between hepatitis C virus (HCV) infection and chronic glomerulonephritis (GN) has been asserted on the grounds of epidemiological and experimental data. Although this suggests a role for an antiviral approach to HCV-associated GN instead of the more conventional immunosuppressive (or supportive) therapy, the optimal management of HCV-related glomerulonephritis remains controversial.

Objective

To compare antiviral with immunosuppressive therapy for HCV-associated GN.

Design

Meta-analysis of controlled clinical trials (CCTs) of the two treatments (antiviral versus immunosuppressive) of HCV-associated GN.

Methods

We used the fixed or random effects model of DerSimonian and Laird, with heterogeneity and sensitivity analyses. The rate of proteinuria and serum creatinine decrease after therapy for HCV-associated GN were regarded as the most reliable outcome end-points.

Results

We identified six studies involving 145 unique patients with HCV-associated GN. Pooling of study results demonstrated that proteinuria decreased more commonly after IFN than corticosteroid therapy (OR 1.92 (95% CI, 0.39; 9.57), NS), P-test for heterogeneity, 0.06 (I2=52.9%). In a sensitivity analysis including only CCTs using standard IFN-doses, OR was 3.86 (95% CI, 1.44; 10.33, (P=0.007)), P-test for heterogeneity, 0.18 (I2=35.9%). No improvement of serum creatinine after IFN compared to immunosuppressive therapy was noted (OR, 0.59 (95% CI, 0.21; 1.65), NS), P-test for heterogeneity, 0.76 (I2=0%). Only three CCTs gave information on the rate of proteinuria decrease over follow-up (OR, 5.08 (95% CI, 0.69; 37.31), NS). A few major side effects were noted after IFN administration.

Conclusions

Our meta-analysis indicates that standard IFN-doses were more effective than immunosuppressive therapy in lowering proteinuria of patients with HCV-related glomerulonephritis. However, no significant improvement in serum creatinine was seen by IFN or steroid therapy across the studies. Also, information on proteinuria recurrence after the completion of antiviral therapy was not sufficient. Prospective, randomized trials based on combined antiviral therapy (pegylated IFN plus ribavirin) with adequate dose and follow-up are required to assess the efficacy and safety of antiviral treatment of HCV-associated glomerulonephritis.

A Case of Cryoglobulinemic Membranoproliferative Glomerulonephritis Induced by Hepatitis C Virus

A 61-year-old man with bilateral purpura of the lower limbs and subsequent edema, was hospitalization after renal dysfunction developed. The presence of hepatitis C virus (HCV) RNA and cryoglobulin and the finding of membranoproliferative glomerulonephritis on renal biopsy led to a diagnosis of HCV-related glomerulonephritis due to cryoglobulinemia. Because of the pre-existence of nephrotic syndrome and the continuously increasing serum level of creatinine, treatment with cryofiltration, interferon, and steroids was started. After 5 cryofiltration sessions, the cryocrit level had decreased to 1% and the levels of serum creatinine and proteinuria had also decreased. However, 3 weeks after the start of treatment, nephrotic syndrome developed again and was accompanied by lower-extremity mononeuropathy and renal dysfunction. Thereafter, the patient showed disorientation, an affective disorder, and delirium, and his condition gradually deteriorated. Radiological examination of the head and examination of the cerebrospinal fluid showed no abnormalities. Despite the withdrawal of the interferon therapy and the reduction of the steroid dose, the patient's conditions remained unchanged, and the level of consciousness deteriorated. Although cryofiltration had beneficial effects and plasma exchange was continuously performed, the patient died on the 74th hospital day. Because of the significant changes due to ventilatory support and hemorrhage associated with disseminated intravascular coagulation, the autopsy findings did not allow us to definitively determine whether the symptoms had been caused by the HCV-related membranoproliferative glomerulonephritis or the interferon therapy or both. We have reported this case to provide insight into whether interferon therapy should be administered for HCV-related membranoproliferative glomerulonephritis with marked neurological symptoms due to cryoglobulinemia.

Hepatitis C virus-related glomerulonephritis with acute kidney injury requiring hemodialysis that improved with virus removal and eradication using double-filtration plasmapheresis without interferon

A 66-year-old, hepatitis C virus (HCV)-positive woman was admitted to our hospital with oliguria, systemic edema, and rapid deterioration of renal function. Laboratory examination showed increased serum creatinine and decreased serum albumin levels, complement activity, and cryoglobulin positivity. The HCV RNA genotype was found to be 1b, and the viral load was high. Kidney biopsy examination showed type I membranoproliferative glomerulonephritis with capillary deposition of IgM and C3, indicating HCV-related glomerulonephritis. After hospitalization, hemodialysis was immediately required because of uremia and oliguria. Her renal function did not improve despite corticosteroid therapy. To treat the increasing HCV load, virus removal and eradication by double-filtration plasmapheresis therapy without interferon was performed, since the patient was allergic to interferon therapy. This treatment improved renal function and allowed the withdrawal from hemodialysis. This report presents a case of successful VRAD without interferon therapy in a patient with HCV-related glomerulonephritis and acute kidney injury that required hemodialysis.

Extrahepatic manifestations of hepatitis C virus (HCV)

Hepatitis C virus (HCV) is an infectious disease that often remains asymptotic and unrecognised until complications of the virus arise. These often include extrahepatic manifestations of the virus, which first bring patients into contact with the medical profession. First recognised in the 1990s several syndromes and conditions have now been linked to hepatitis C, while others are still emerging. In some patients, extrahepatic manifestations can be the dominant feature, while hepatic disease is mild. Some conditions have an established association with the virus with a proven pathophysiological and epidemiology, such as cryoglobulinaemia. Others have consistently been found to be seen in patients with HCV, but the underlying cause of these conditions is not clearly understood. These include porphyria cutanea tarda. Many other autoimmune conditions are commonly seen in the patients with HCV as well as nephropathies, but the exact interplay between virus and resulting clinical condition is not clear. Clinicians have to have a high index of suspicion and a knowledge of the extrahepatic manifestations of HCV in order to not only treat the manifestation but also in initiated timely therapies for the underlying HCV.

Telaprevir in a patient with chronic hepatitis C and cryoglobulinemic glomerulonephritis

Mixed cryoglobulinemia (MC), the most common extrahepatic manifestation of HCV, may lead to renal involvement ranging from mild urinary abnormalities to nephritic syndrome, eventually evolving to renal failure requiring renal replacement therapy. HCV eradication with pegylated interferon (PEG-IFN) and ribavirin (RBV) is the only curative treatment for MC-related membranoproliferative glomerulonephritis. The addition of directly acting antivirals (DAAs) to PEG-IFN and RBV has significantly improved sustained virological response rates in HCV genotype 1 patients. Safety and efficacy of this regimen in patients with membranoproliferative glomerulonephritis has not been proved yet. Here, we report the case of a woman with HCV-1-related cryoglobulinemic membranoproliferative glomerulonephritis presenting with severe nephritic syndrome and rapidly progressive renal failure, who received successful treatment with the DAA telaprevir in conjunction with PEG-IFN and RBV. Triple therapy was safe and effective, leading to HCV eradication and complete resolution of acute renal failure.

Hepatitis C virus and kidney disease

Hepatitis C virus (HCV) is the most frequently observed viral infection in patients with kidney disease. HCV can cause glomerular disease, which can lead to end-stage renal disease that requires dialysis and/or kidney transplantation. It is recommended to test HCV patients once a year for proteinuria, microscopic hematuria and estimated glomerular filtration rate. Membranoproliferative glomerulonephritis is the most common glomerular disease induced by HCV. Over the past few decades, the prevalence of HCV infection has decreased among dialysis and kidney transplant patients. However, survival is significantly lower in HCV-positive than in HCV-negative dialysis patients whereas survival is significantly better in HCV-positive kidney transplant patients compared with HCV-positive dialysis patients. Thus, dialysis patients without a sustained virological response after anti-HCV therapy should be proposed for kidney transplantation. Recurrence or de novo occurrence of glomerular disease is responsible for the lower kidney allograft survival in HCV-positive compared with HCV-negative kidney transplant patients. Dialysis and kidney transplantation do not appear to negatively affect progression of liver fibrosis in the majority of patients. The available data also suggest that occult HCV infection does not exist in dialysis and kidney transplant patients.

Hepatitis C infection and chronic renal diseases

Hepatitis C virus (HCV) infection and chronic renal diseases can be linked in two different ways. Some forms of renal disease are precipitated by HCV infection, while patients with end-stage renal disease are at increased risk for acquiring HCV infection. Patients with chronic HCV infection and renal disease have a poor prognosis. Most studies on treatment of HCV and renal diseases have been uncontrolled trials with small number of subjects. So, there is a lack of evidence-based recommendations and guidelines on the management of this condition. In this review, we will attempt to provide the most recent insights on HCV infection both as a extrahepatic manifestations and as a complication of end-stage renal patients.

Remission of HCV-associated Glomerulonephritis with Pegylated IFN and Ribavirin Therapy after Liver Transplantation: Case Report and Literature Review

Background

Hepatitis C virus infection is associated with a variety of extrahepatic disorders such as membrano-proliferative glomerulonephritis, which is generally due to cryoglobulinemia.

Setting

We describe the case of one liver transplant recipient who received antiviral therapy (subcutaneous administration of peg-IFN-alpha-2a 180 mcg weekly and oral ribavirin 200 mg thrice a day) for HCV-related membrano-proliferative glomerulonephritis. He presented normal kidney function, non-nephrotic proteinuria (2 g/24 h) and mild hematuria.

Results

Urinary abnormalities disappeared within a few weeks after the initiation of antiviral therapy; however, combination antiviral therapy was not able to obtain viral clearance. After 11 months, IFN-therapy was interrupted and the patient continued low-dose ribavirin monotherapy (200 mg once per day) for one additional year- remission of proteinuria (<0.3 g/24 h) and hematuria persisted with intact kidney function. Although other mechanisms cannot be excluded, we suggest that ribavirin therapy was critically implicated in the remission of urinary abnormalities in our patient. The existing literature on the association between HCV-associated glomerulonephritis and therapy with ribavirin is reviewed.

Conclusions

Antiviral therapy may be effective in patients with HCV-induced glomerulonephritis. Further evidence is needed to evaluate efficacy and safety of ribavirin monotherapy for HCV-related glomerulonephritis.

Hepatitis E virus and the kidney in solid-organ transplant patients

BACKGROUND

Hepatitis E virus (HEV) infection is an emerging disease in industrialized countries. Few data regarding genotype 3 HEV extrahepatic manifestations exist.

METHODS

We assessed kidney function and histology in solid-organ transplant patients during HEV infection. In all, 51 cases of genotype 3 HEV infections were diagnosed (34 kidney, 14 liver, and 3 kidney-pancreas transplant patients). Of these, 43.2% were cleared of the virus spontaneously within 6 months of infection, whereas 56.8% evolved to chronic hepatitis. Twelve of these patients completed a 3-month antiviral therapy and were followed up for 6 months posttreatment. Kidney function (estimated glomerular filtration rate [eGFR] obtained by the Modification of Diet in Renal Disease equation) and proteinuria were assessed before infection, during HEV infection and during follow-up. Kidney biopsies were obtained from patients with high proteinuria and decreased eGFR levels.

RESULTS

During HEV infection, there was a significant decrease in eGFR in both kidney- and liver-transplant patients. Glomerular diseases were observed in kidney biopsies obtained during the acute and chronic phases. This included membranoproliferative glomerulonephritis and relapses in IgA nephropathy. The majority of patients had cryoglobulinemia that became negative after HEV clearance. Kidney function improved and proteinuria decreased after HEV clearance.

CONCLUSION

HEV-associated glomerulonephritis seems to be an HEV-related extrahepatic manifestation. Further studies are required to confirm these observations.

Central nervous system vasculitis and polyneuropathy as first manifestations of hepatitis C

Sensory or motor peripheral neuropathy may be observed in a significant proportion of hepatitis C virus (HCV)-infected patients. However, central nervous system (CNS) involvement is uncommon, especially in cryoglobulin-negative subjects. We describe a case of peripheral neuropathy combined with an ischemic CNS event as primary manifestations of chronic HCV infection without cryoglobulinemia. Significant improvement was observed after antiviral therapy. We discuss the spectrum of neurological manifestations of HCV infection and review the literature.

Hepatitis C virus and kidney: a strong association with different clinical aspects

The most frequent kidney disease associated with chronic hepatitis C virus (HCV) infection is membranoproliferative glomerulonephritis in patients with type II mixed cryoglobulinaemia. The principal clinical manifestations of glomerular disease in HCV-infected patients are the presence of proteinuria and haematuria with or without impaired kidney function. Pharmaceutical regimens vary because the main pathogenesis of renal dysfunction often mediated by cryoglobulins has not been fully elucidated. HCV infection remains common in patients on renal replacement therapy and has an adverse impact on their survival. Safe and effective pharmaceutical regimens have not been yet established and nosocomial spread within dialysis units continues to occur. Monotherapy with interferon for HCV infection is probably more effective in dialysis than in non-uraemic patients, while experience with ribavirin is limited because of its adverse haemolytic effect. Based on shortage of cadaver kidneys and the fact that HCV renal transplant recipients have better survival than stay on maintenance haemodialysis or at list for transplantation, health organization proposed the use of cadaver kidneys from anti-HCV-positive donors, bringing up concerns and conflicting views. This present review describes the main renal manifestations of HCV infection, the epidemiological and clinical characteristics of chronic kidney disease population and comments on the limitations and shortcomings of current therapeutical regiments.

Chronic viral hepatitis and chronic kidney disease

Chronic kidney disease (CKD) has become a major public health problem worldwide over the past few decades because of the increasing prevalence of hypertension, diabetes mellitus, and elderly individuals in most countries. Chronic viral hepatitis (due to hepatitis B virus (HBV) and hepatitis C virus (HCV)) also poses significant morbidity and mortality globally. Both these viruses can cause CKD and these infections can occur as a consequence of CKD management. CKD patients acquiring HBV or HCV infection have higher morbidity and mortality rates, and the management of these infections among CKD patients with antiviral agents is associated with high rates of adverse effects. The optimal management of CKD associated with HBV and HCV is not well defined because of insufficient data from clinical trials. This review discusses the pathogenesis, clinical characteristics and management issues related to chronic viral hepatitis and CKD.

Successful treatment of HCV-related cryoglobulinemic glomerulonephritis with double-filtration plasmapheresis and interferon combination therapy

A 67-year-old, hepatitis C virus (HCV)-positive woman was admitted to our hospital because of proteinuria and leg edema. Laboratory examination showed decreased serum albumin and complement activity and positive cryoglobulin. The HCV RNA genotype was 1b with high viral load. Kidney biopsy showed membranoproliferative glomerulonephritis (MPGN) with capillary deposition of C3, IgM, and IgG, indicating HCV-associated glomerulonephritis. In addition to interferon (IFN) therapy, double-filtration plasmapheresis (DFPP) was performed to reduce HCV RNA blood levels in the early stage of IFN therapy. This treatment greatly reduced the viral load and induced clinical remission of MPGN, suggesting that DFPP plus IFN combination therapy may represent a potentially effective modality for refractory-type HCV-associated glomerulonephritis.

[Diagnosis, treatment and prevention of renal diseases in HIV infected patients. Recommendations of the Spanish AIDS Study Group/National AIDS Plan]

The incidence of opportunistic infections and tumours in HIV-infected patients has sharply declined in the HAART era. At the same time there has been a growing increase of other diseases not directly linked to immunodeficiency. Renal diseases are an increasing cause of morbidity and mortality among HIV-infected patients. In the general population, chronic renal failure has considerable multiorgan repercussions that have particular implications in patients with HIV infection. The detection of occult or subclinical chronic kidney disease is crucial since effective measures for delaying progression exist. Furthermore, the deterioration in glomerular filtration should prompt clinicians to adjust doses of some antiretroviral agents and other drugs used for treating associated comorbidities. Suppression of viral replication, strict control of blood pressure, dyslipidemia and diabetes mellitus, and avoidance of nephrotoxic drugs in certain patients are fundamental components of programs aimed to prevent renal damage and delaying progression of chronic kidney disease in patients with HIV. Renal transplantation and dialysis have also special implications in HIV-infected patients. In this article, we summarise the updated clinical practice guidelines for the evaluation, management and prevention of renal diseases in HIV-infected patients from a panel of experts in HIV and nephrologists on behalf of the Spanish AIDS Study Group (GESIDA) and the National AIDS Plan.

Novel B cell therapeutic targets in transplantation and immune-mediated glomerular diseases

B cells and antibodies play an important role in the alloresponse to renal grafts as well as in immune-mediated glomerular diseases. In transplantation, greater recognition and improved diagnosis of antibody-mediated rejection have been a catalyst to the introduction of newer drugs and regimens that target B cells, plasma cells, and donor-specific antibodies to improve the outcome associated with antibody-mediated rejection. In immune-mediated renal disease, novel and more selective B cell therapies are gradually modifying the traditional therapeutic approach that consists of steroids and other immunosuppressants. A new era of selective and more effective immunosuppression agents that target the humoral response is finally emerging in transplantation and renal diseases.

Systemic abnormalities in liver disease

Systemic abnormalities often occur in patients with liver disease. In particular, cardiopulmonary or renal diseases accompanied by advanced liver disease can be serious and may determine the quality of life and prognosis of patients. Therefore, both hepatologists and non-hepatologists should pay attention to such abnormalities in the management of patients with liver diseases.

Renal biopsy in a patient with haemophilia A and cryoglobulinaemic membranoproliferative glomerulonephritis associated with hepatitis C virus infection

A renal biopsy was performed in a 47-year-old man with haemophilia A. Thirty minutes after administration of an intravenous bolus of 4000 units of recombinant factor VIII, which increased the activity to 74–91%, a needle renal biopsy was successfully performed, followed by administration of 3000 units of factor VIII in the evening, and then the subsequent morning and evening. The patient was diagnosed with hepatitis C virus-associated membranoproliferative glomerulonephritis. Treatment with interferon, ribavirin, prednisolone and cyclosporine A improved the nephrotic syndrome. This is the first report of a successful renal biopsy in a patient with haemophilia A after factor VIII injection.

Hepatitis C infection and chronic renal diseases

More than 170 million people worldwide are chronically infected with the hepatitis C virus (HCV), which is responsible for over 1 million deaths resulting from cirrhosis and liver cancers. Extrahepatic manifestations are also relevant and include mixed cryoglobulinemia, lymphoproliferative disorders, and kidney disease. HCV infection is both a cause and a complication of chronic kidney disease, occurring largely in the context of mixed cryoglobulinemia. This infection also represents a major medical and epidemiologic challenge in patients with end-stage renal disease on renal replacement therapy with dialysis or transplantation. In these settings the presence of HCV correlates with higher rates of patient mortality than in HCV-negative subjects on dialysis or undergoing kidney transplant. The major concern is the lack of safe and effective drugs to treat HCV-infected patients with chronic kidney disease. Unfortunately, there are no large-scale clinical trials in this population, especially those receiving renal replacement therapy, so that strong evidence for treatment recommendations is scant. This review article provides the readers with the most recent insights on HCV infection both as cause and complication of chronic kidney disease, discusses pitfalls and limitations of current therapies, and reports on preliminary experience with novel therapeutic agents, as well as directions for future research.

Extrahepatic hepatitis C virus after transplantation: diabetes and renal dysfunction

1. Insulin resistance is associated with hepatitis C virus infection and plays a role in the progression of hepatitis C virus-related liver disease and fibrosis. 2. Treating insulin resistance and achieving glycemic control will be important for improving post-liver transplant morbidity and mortality: control of the hepatitis C virus will help to accomplish this. 3. The main renal complication of hepatitis C virus is membranoproliferative glomerulonephritis, and this occurs most commonly in the setting of mixed cryoglobulinemia.

Cryoglobulinemia and renal disease

PURPOSE OF REVIEW

Cryoglobulinemia occurs in a variety of clinical settings including lymphoproliferative disorders, infection and autoimmune disease. The worldwide pandemic of hepatitis C virus infection has resulted in a significant increase in its extrahepatic complications including cryoglobulinemia and renal disease. Here we review the types of cryoglobulins, mechanisms of cryoglobulin formation, links between hepatitis C virus and renal disease, and current approaches to therapy.

RECENT FINDINGS

The prevalence of cryoglobulinemia in hepatitis C virus-infected individuals is surprisingly large and may be found in more than 50% of some infected subpopulations. Most of these patients will not have overt renal disease, but there is a population of unknown size of patients with subclinical glomerular disease that has the potential to become clinically significant. In cases of hepatitis C virus-associated cryoglobulinemia, treatment remains focused on eradication of viremia, but interventions directed at B lymphocytes are increasingly utilized. The mechanisms of cryoglobulin formation and renal injury remain largely obscure, but recent evidence implicates the innate immune system in the initiation of disease.

SUMMARY

The most common renal injury associated with hepatitis C virus infection, in patients both with and without evidence of cryoglobulinemia, is membranoproliferative glomerulonephritis. There has been increasing focus on defining the mechanisms that link these processes and the evolution of renal injury in all clinical settings of cryoglobulinemia.

Renin-angiotensin system blockade is renoprotective in immune complex-mediated glomerulonephritis

Blockade of the renin-angiotensin system is renoprotective in a variety of chronic nephropathies, but the direct effect of such treatment in active, immune complex-mediated glomerulonephritis is unknown. This study investigated the short- and long-term effects of an angiotensin-converting enzyme inhibitor (enalapril) and an angiotensin II type 1 receptor blocker (losartan) in thymic stromal lymphopoietin transgenic (TSLPtg) mice, which develop mixed cryoglobulinemia and severe cryoglobulinemia-associated membranoproliferative glomerulonephritis. Enalapril and losartan each reduced hypertension, proteinuria, glomerular extracellular matrix deposition, and mesangial cell activation in TSLPtg mice. These renoprotective effects were not observed with hydralazine treatment, despite a similar antihypertensive effect. Treatment with enalapril or losartan also decreased renal plasminogen activator inhibitor-1 in TSLPtg mice, assessed by immunohistochemistry and quantitative real-time reverse transcriptase-PCR. None of the treatments affected immune complex deposition or macrophage infiltration. Overall, enalapril- and losartan-treated TSLPtg mice survived significantly longer than untreated TSLPtg mice. These studies demonstrate that angiotensin blockade may provide renoprotective benefits, independent of its BP-lowering effect, in the treatment of active immune complex-mediated glomerulonephritis.

Infection and glomerulonephritis

Glomerular injury, occurring either as primary glomerular disease or as part of a systemic disease process, is usually a result of immune-mediated mechanisms. The morphologic reaction pattern has a diverse spectrum of appearance, ranging from normal by light microscopy in minimal change disease to crescentic forms of glomerulonephritis, with conspicuous disruption of the normal glomerular morphology. The mechanisms of glomerular immune deposit formation include trapping of circulating antigen-antibody complexes and the in situ formation of immune complexes within the glomerulus. While the majority of postinfectious immune-complex-mediated glomerulonephritides are believed to result from the deposition of circulating antigen-antibody complexes, preformed outside of the kidney and secondarily deposited in the kidney, the notion of forming in situ antigen-antibody complexes to either planted antigens or to integral structural components of the glomerulus, through "cross-reacting" autoimmune reactions, is gaining popularity in a variety of forms of glomerulonephritides. Patients with HIV infection may develop a spectrum of renal pathology, the glomerular manifestations of which include both antigen-antibody complex and nonimmune-complex-mediated pathogenetic mechanisms. Similarly, patients with Streptococcal infections, Hepatitis B virus, or Hepatitis C virus infection may develop a spectrum of glomerulonephritides, which are predominantly immune-complex-mediated. Therapy for glomerular diseases due to HIV, hepatitis B, or C virus infections remains a challenge.

68-year-old woman with hepatitis C and abnormal kidney function

A 68-year-old woman with a history of hepatitis C (contracted from a blood transfusion in 1974) complicated by cirrhosis and portal hypertension came to the Mayo Clinic in Rochester, Minn, for evaluation for possible liver transplantation. Her symptomatic ascites had been treated initially with furosemide and spironolactone, but this treatment regimen was limited because of an increase in her creatinine level. During evaluation, hypertension (an average blood pressure of 180/90 mm Hg on 6-hour ambulatory monitoring) and abnormal renal function were noted. She was referred to our institution for further evaluation of her blood pressure and abnormal urinalysis results.

Cryoglobulinemia related to hepatitis C virus infection

A causal link among hepatitis C virus (HCV) infection and essential mixed cryoglobulinemia, cryoglobulinemic glomerulonephritis, and vasculitis is strongly supported. HCV triggers autoimmune response in predisposed individuals that manifests as organ-specific and non-organ-specific autoantibodies and as polyclonal/monoclonal rheumatoid factor, which has a central role in causing damaging cryoglobulin and immune complex tissue levels. Immunologic events are mainly induced by HCV infection persistence, with excessive immune stimulation. Humoral immune dysfunction leads to autoantibodies and rheumatoid factor production with cryoglobulinemia, glomerulonephritis, vasculitis, neuropathy, and probably thyroiditis, and arthritis in rare cases. Cellular immune dysfunction leads to lymphocytic infiltration, proliferation, and cytokine production. Pegylated (or not) interferon-alpha in combination with ribavirin appears to be the treatment of choice for patients with symptomatic essential mixed cryoglobulinemia with or without glomerulonephritis. Novel treatment with rituximab is promising.

Cryoglobulinaemic vasculitis: classification and clinical and therapeutic aspects

Cryoglobulinaemia may cause cutaneous vasculitis and glomerulonephritis, potentially leading to end stage renal failure. An important proportion of cryoglobulinaemias are secondary to hepatitis C virus infection. Emerging antiviral treatment options offer a chance for causal therapy of these cases of cryoglobulinaemia. This review summarises the classification and clinical and therapeutic aspects of cryoglobulinaemic vasculitis and glomerulonephritis.

The kidney transplant recipient with hepatitis C infection: pre- and posttransplantation treatment

Liver disease secondary to chronic hepatitis C virus (HCV) infection is an important cause of morbidity and mortality in dialysis patients and kidney transplant recipients. Evaluation of patients with chronic HCV infection is warranted to determine stage of disease and the need for HCV therapy. Although combination therapy with interferon (IFN) plus ribavirin is the standard of care for chronic HCV infection, IFN monotherapy is recommended in dialysis patients because ribavirin is contraindicated in the presence of renal failure. The goals of pretransplantation HCV therapy are to decrease the risk for progression of HCV-associated liver disease, stabilize renal function in patients with HCV-related glomerulopathy, and prevent development of HCV-associated renal disease after transplantation. Posttransplantation HCV therapy is generally not recommended because of concerns regarding risk for precipitating acute rejection; however, antiviral therapy may be indicated to treat HCV-related glomerulopathy or prevent progression of chronic hepatitis C in patients with more advanced stages of fibrosis. When treatment is required, restored renal function allows use of combination therapy with IFN and ribavirin. Limitations of current HCV therapy include lack of tolerability and suboptimal response rates. New antiviral agents that can be used in dialysis patients (e.g., ribavirin alternatives) and in the posttransplantation setting (e.g., IFN alternatives) are needed to improve outcomes in these populations.