Parvovirus B19 infection and kidney injury: report of 4 cases and analysis of immunization and viremia in an adult cohort of 100 patients undergoing a kidney biopsy

Lupus Nephritis With Collapsing Glomerulopathy: A Rare Association

Lupus nephritis (LN) is one of the most severe organ manifestations of systemic lupus erythematosus (SLE). Crescentic lupus nephritis rarely presents as rapidly progressive renal failure (RPRF) and needs prompt initiation of treatment. Collapsing glomerulopathy (CG) itself is associated with poor renal survival. Collapsing glomerulopathy's association with lupus nephritis is rarely reported in the literature. It may indicate a severe form of lupus podocytopathy.

Type I interferon-related kidney disorders

Type I interferon (IFN-I) mediates tissue damage in a wide range of kidney disorders, directly affecting the biology and function of several renal cell types including podocytes, mesangial, endothelial and parietal epithelial cells (PECs).Enhanced IFN-I signalling is observed in the context of viral infections, autoimmunity (e.g., systemic lupus erythematosus, SLE), and the type 1 interferonopathies (T1Is), rare monogenic disorders characterised by constitutive activation of the IFN-I pathway. All of these IFN I-related disorders can cause renal dysfunction, and share pathogenic and histopathological features. Collapsing glomerulopathy, a histopathological lesion characterised by podocyte loss, collapse of the vascular tuft and PEC proliferation, is commonly associated with viral infections, has been described in T1Is such as Aicardi-Goutières syndrome and STING-associated vasculopathy with onset in infancy (SAVI), and can also be induced by recombinant IFN-therapy. In all of these conditions, podocytes and PECs seem to be the primary target of IFN I-mediated damage. Additionally, immune-mediated glomerular injury is common to viral infections, SLE, and T1Is such as COPA syndrome and DNASE1L3 deficiency, diseases in which IFN-I apparently promotes immune-mediated kidney injury. Finally, kidney pathology primarily characterised by vascular lesions (e.g., thrombotic microangiopathy, vasculitis) is a hallmark of the T1I ADA2 deficiency as well as of SLE, viral infections and IFN-therapy.Defining the nosology, pathogenic mechanisms and histopathological patterns of IFN I-related kidney disorders has diagnostic and therapeutic implications, especially considering the likely near-term availability of novel drugs targeting the IFN-I pathway.

Proliferative glomerulonephritis with monoclonal immunoglobulin deposits associated with parvovirus B19

Proliferative glomerulonephritis with monoclonal immunoglobulin deposits (PGNMID) is included in the group of dysproteinaemias causing renal disease. Only a minority of cases are associated with a haematological malignancy. Two cases have been linked to acute parvovirus B19 infections. We report a 36-year-old African-American woman who presented with renal dysfunction, proteinuria, haematuria and a kidney biopsy reported as PGNMID with IgG3-kappa deposits. Her evaluation for a haematological malignancy was unrevealing. Her parvovirus IgM and IgG levels were positive. The patient was initially treated with an ACE inhibitor and spontaneously remitted with minimal proteinuria after 1 month. Repeat parvovirus B19 serologies 6 months later showed persistent IgG and DNA by PCR positivity but IgM negativity. Given the clinical scenario, we believe that her PGNMID was induced by acute parvovirus B19 infection, which appeared to resolve once her acute infection abated. In this report, we describe our latest understanding of PGNMID.

Viral Infections and Systemic Lupus Erythematosus: New Players in an Old Story

A causal link between viral infections and autoimmunity has been studied for a long time and the role of some viruses in the induction or exacerbation of systemic lupus erythematosus (SLE) in genetically predisposed patients has been proved. The strength of the association between different viral agents and SLE is variable. Epstein-Barr virus (EBV), parvovirus B19 (B19V), and human endogenous retroviruses (HERVs) are involved in SLE pathogenesis, whereas other viruses such as Cytomegalovirus (CMV) probably play a less prominent role. However, the mechanisms of viral-host interactions and the impact of viruses on disease course have yet to be elucidated. In addition to classical mechanisms of viral-triggered autoimmunity, such as molecular mimicry and epitope spreading, there has been a growing appreciation of the role of direct activation of innate response by viral nucleic acids and epigenetic modulation of interferon-related immune response. The latter is especially important for HERVs, which may represent the molecular link between environmental triggers and critical immune genes. Virus-specific proteins modulating interaction with the host immune system have been characterized especially for Epstein-Barr virus and explain immune evasion, persistent infection and self-reactive B-cell "immortalization". Knowledge has also been expanding on key viral proteins of B19-V and CMV and their possible association with specific phenotypes such as antiphospholipid syndrome. This progress may pave the way to new therapeutic perspectives, including the use of known or new antiviral drugs, postviral immune response modulation and innate immunity inhibition. We herein describe the state-of-the-art knowledge on the role of viral infections in SLE, with a focus on their mechanisms of action and potential therapeutic targets.

PD-1 and PD-L1 Expression on Circulating Lymphocytes as a Marker of Epstein-Barr Virus Reactivation-Associated Proliferative Glomerulonephritis

Alterations to the programmed cell death protein-1 (PD-1) pathway were previously shown to be involved in a poorer prognosis for patients with proliferative glomerulonephritis (PGN). Here, we investigated the association between several infectious agents and the expression of PD-1 and its ligand (PD-L1) on T and B lymphocytes in patients with PGN and nonproliferative glomerulonephritis (NPGN). A cohort of 45 newly-diagnosed patients (23 with PGN and 22 with NPGN) and 20 healthy volunteers was enrolled. The percentage of peripheral blood mononuclear cells expressing PD-1 and PD-L1 antigens was determined by flow cytometry. We found PD-1 and PD-L1 expression on T and B lymphocytes was higher in PGN patients than in NPGN patients and controls. We also found that reactivation of the Epstein-Barr virus (EBV) correlated with the expression of PD-1/PD-L1 antigens in patients with PGN. Further receiver operating characteristic analysis indicated that PD-1 expression could distinguish EBV-positive PGN patients from those with NPGN or healthy controls. The use of PD-1 expression as a non-invasive marker of PGN should be further investigated.