Clinicopathological study on hepatitis C virus-associated glomerulonephritis without hepatitis C virus in the blood

The Human Virome and Its Crosslink with Glomerulonephritis and IgA Nephropathy

The prokaryotic, viral, fungal, and parasitic microbiome exists in a highly intricate connection with the human host. In addition to eukaryotic viruses, due to the existence of various host bacteria, phages are widely spread throughout the human body. However, it is now evident that some viral community states, as opposed to others, are indicative of health and might be linked to undesirable outcomes for the human host. Members of the virome may collaborate with the human host to retain mutualistic functions in preserving human health. Evolutionary theories contend that a particular microbe's ubiquitous existence may signify a successful partnership with the host. In this Review, we present a survey of the field's work on the human virome and highlight the role of viruses in health and disease and the relationship of the virobiota with immune system control. Moreover, we will analyze virus involvement in glomerulonephritis and in IgA nephropathy, theorizing the molecular mechanisms that may be responsible for the crosslink with these renal diseases.

A case of rapid amelioration of hepatitis C virus-associated cryoglobulinemic membranoproliferative glomerulonephritis treated by interferon-free directly acting antivirals for HCV in the absence of immunosuppressant

Mixed cryoglobulinemic syndrome, which is a systemic vasculitis characterized by the immune complex deposition in small- and medium-sized arteries and most often due to chronic hepatitis C virus (HCV) infection, sometimes clinically manifests as refractory glomerulonephritis or nephritic syndrome. Patients with mixed cryoglobulinemic nephropathy who have a rapidly progressive glomerulonephritis should receive immunosuppressive therapy. After disease stabilization, patients should receive concurrent therapy for the underlying HCV infection. The standard therapy of a chronic HCV infection is IFN monotherapy or IFN combined with ribavirin; however, after the introduction of direct-acting antivirals (DAAs), the standard therapy for patients with HCV genotype 1 has dramatically changed. We report a case of HCV-associated cryoglobulinemic membranoproliferative glomerulonephritis (MPGN) successfully treated by daclatasvir and asunaprevir, which are IFN-free DAAs for HCV, in combination with angiotensin II receptor blocker without immunosuppressive therapy. The patient developed severe nephrotic syndrome with progressive kidney dysfunction. Blood examination revealed a high copy number of HCV-RNA (6.4 log IU/mL, type 1), cryoglobulinemia, paraproteinemia of IgM-κ, and hypocomplementemia. Histological analysis showed MPGN type 1. These findings were compatible with those observed in HCV-associated cryoglobulinemic MPGN. This case offers original evidence for the application of newer generation of IFN-free DAAs in the treatment of HCV-associated cryoglobulinemic nephropathy.

Detection of viral antigens in renal tissue of glomerulonephritis patients without serological evidence of hepatitis B virus and hepatitis C virus infection

OBJECTIVES

Glomerulonephritis is an important extrahepatic manifestation of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. HBV and HCV infection may be occult, and they are often overlooked by both patients and doctors. The aim of this study was to assess the importance of HBV and HCV infection in glomerulonephritis patients with undetectable HBV surface antigen (HBsAg) and HCV antibody in serum.

METHODS

The HBsAg, the HBV core antigen (HBcAg), and the HCV antigen were detected using immunohistochemistry in frozen renal tissues of 500 glomerulonephritis patients without serological evidence of HBV and HCV infection. Electron microscopy was used to trace the virus particles, and clinicopathological features were also reviewed.

RESULTS

HBsAg or HBcAg was positive in nine out of 500 cases (9/500, 1.8%). Three cases were HBsAg-positive and another six cases were HBcAg-positive. The HCV antigen was found in eight cases (8/500, 1.6%). There was one case of HBV and HCV co-infection (1/500, 0.2%). Under electron microscopy, virus particles were found in the base membrane and cytoplasm of endotheliocytes in the glomerulus. The most common clinical manifestation was nephrotic syndrome (9/18), followed by nephritic syndrome (7/18). Membranous nephropathy was the most common pathological diagnosis (5/18), followed by mesangioproliferative glomerulonephritis (4/18) and IgA nephropathy (4/18).

CONCLUSIONS

Occult HBV and HCV infection might be implicated in HBV- or HCV-associated glomerulonephritis. More attention should be focused on the underlying cause.

Rheumatoid factor, complement, and mixed cryoglobulinemia

Low serum level of complement component 4 (C4) that occurs in mixed cryoglobulinemia (MC) may be due to in vivo or ex vivo activation of complement by the classical pathway. Potential activators include monoclonal IgM rheumatoid factor (RF), IgG antibodies, and the complexing of the two in the cold, perhaps modulated by the rheology and stoichiometry of cryocomplexes in specific microcirculations. There is also the potential for activation of complement by the alternative and lectin pathways, particularly in the setting of chronic infection and immune stimulation caused by hepatitis C virus (HCV). Engagement of C1q and interaction with specific cell surface receptors serve to localize immune complexes (ICs) to the sites of pathology, notably the cutaneous and glomerular microcirculations. Defective or saturated clearance of ICs by CR1and/or Fc receptors may explain persistence in the circulation. The phlogistic potential of cryoprecipitable ICs depends upon the cleavage of complement components to generate fragments with anaphylatoxin or leukocyte mobilizing activity, and the assembly of the membrane attack complex (C5b-9) on cell surfaces. A research agenda would include further characterization of the effector arm of complement activation in MC, and elucidation of activation mechanisms due to virus and viral antigens in HCV infection.