Human mesangial cells are resistant to productive infection by multiple strains of human immunodeficiency virus types 1 and 2

NEF-Induced HIV-Associated Nephropathy Through HCK/LYN Tyrosine Kinases

HIV-1-associated nephropathy (HIVAN) is a severe complication of HIV-1 infection. To gain insight into the pathogenesis of kidney disease in the setting of HIV, a transgenic (Tg) mouse model [CD4C/HIV-negative regulator factor (Nef)] was used in which HIV-1 nef expression is under control of regulatory sequences (CD4C) of the human CD4 gene, thus allowing expression in target cells of the virus. These Tg mice develop a collapsing focal segmental glomerulosclerosis associated with microcystic dilatation, similar to human HIVAN. To identify kidney cells permissive to the CD4C promoter, CD4C reporter Tg lines were used. They showed preferential expression in glomeruli, mainly in mesangial cells. Breeding CD4C/HIV Tg mice on 10 different mouse backgrounds showed that HIVAN was modulated by host genetic factors. Studies of gene-deficient Tg mice revealed that the presence of B and T cells and that of several genes was dispensable for the development of HIVAN: those involved in apoptosis (Trp53, Tnfsf10, Tnf, Tnfrsf1b, and Bax), in immune cell recruitment (Ccl3, Ccl2, Ccr2, Ccr5, and Cx3cr1), in nitric oxide (NO) formation (Nos3 and Nos2), or in cell signaling (Fyn, Lck, and Hck/Fgr). However, deletion of Src partially and that of Hck/Lyn largely abrogated its development. These data suggest that Nef expression in mesangial cells through hematopoietic cell kinase (Hck)/Lck/Yes novel tyrosine kinase (Lyn) represents important cellular and molecular events for the development of HIVAN in these Tg mice.

HIV-associated nephropathies: epidemiology, pathology, mechanisms and treatment

HIV is a highly adaptive, rapidly evolving virus, which is associated with renal diseases including collapsing glomerulopathy-the classic histomorphological form of HIV-associated nephropathy. Other nephropathies related to viral factors include HIV-immune-complex kidney disease and thrombotic microangiopathy. The distribution of HIV-associated kidney diseases has changed over time and continues to vary across geographic regions worldwide. The reasons for this diversity are complex and include a critical role of APOL1 variants and possibly other genetic factors, disparities in access to effective antiviral therapies, and likely other factors that we do not yet fully understand. The mechanisms responsible for HIVAN, including HIV infection of podocytes and tubular epithelial cells, the molecules responsible for HIV entry, and diverse mechanisms of cell injury, have been the focus of much study. Although combined antiretroviral therapy is effective at preventing and reversing HIVAN, focal segmental glomerulosclerosis, arterionephrosclerosis and diabetic nephropathy are increasingly common in individuals who have received such therapy for many years. These diseases are associated with metabolic syndrome, obesity and premature ageing. Future directions for HIV-related kidney disease will involve regular screening for drug nephrotoxicity and incipient renal disease, as well as further research into the mechanisms by which chronic inflammation can lead to glomerular disease.

Controversies in the pathogenesis of HIV-associated renal diseases

The two most common HIV-associated renal diseases, HIV-associated nephropathy and HIV immune-complex kidney disease, share the common pathologic finding of hyperplasia within the glomerulus. Podocyte injury is central to the pathogenesis of these diseases; however, the source of the proliferating glomerular epithelial cell remains a topic of debate. Parenchymal injury has been linked to direct infection of renal epithelial cells by HIV-1, although the mechanism of viral entry into this non-lymphoid compartment is unclear. Although transgenic rodent models have provided insight into viral proteins responsible for inducing renal disease, such models have substantial limitations. Rodent HIV-1 models, for instance, cannot replicate all features of immune activation, a process that could have an important role in the pathogenesis of the HIV-associated renal diseases.

Taking a hard look at the pathogenesis of childhood HIV-associated nephropathy

Childhood human immunodeficiency virus-associated nephropathy (HIVAN) is defined by the presence of proteinuria associated with mesangial hyperplasia and/or global-focal segmental glomerulosclerosis, in combination with the microcystic transformation of renal tubules. This review discusses the pathogenesis of childhood HIVAN and explores how the current pathological paradigm for HIVAN in adults can be applied to children. The Human Immunodeficiency Virus-1 (HIV-1) induces renal epithelial injury in African American children with a genetic susceptibility to develop HIVAN. The mechanism is not well understood, since renal epithelial cells harvested from children with HIVAN do not appear to be productively infected. Children with HIVAN show a renal up-regulation of heparan sulphate proteoglycans and a recruitment of circulating heparin-binding growth factors, chemokines, and mononuclear cells. Macrophages appear to establish a renal HIV-reservoir and transfer viral particles to renal epithelial cells. All of these changes seem to trigger an aberrant and persistent renal epithelial proliferative response. The paradigm that viral products produced by infected renal epithelial cells per se induce the proliferation of these cells is not supported by data available in children with HIVAN. More research is needed to elucidate how HIV-1 induces renal epithelial injury and proliferation in HIV-infected children.

Pathogenesis of nonimmune glomerulopathies

Nonimmune glomerulopathies are an area of significant research. This review discusses the development of focal segmental glomerulosclerosis, with particular attention to the role of the podocyte in the initiation of glomerulosclerosis and the contribution to glomerulosclerosis from capillary hypertension and soluble factors such as transforming growth factor beta, platelet-derived growth factor, vascular endothelial growth factor, and angiotensin. The effects of these factors on endothelial and mesangial cells are also discussed. In addition, we review our current understanding of the slit diaphragm (a specialized cell junction found in the kidney), slit diaphragm-associated proteins (including nephrin, podocin, alpha-actinin-4, CD2-associated protein, and transient receptor potential channel 6), and the role of these proteins in glomerular disease. We also discuss the most recent research on the pathogenesis of collapsing glomerulosclerosis, human immunodeficiency virus associated nephropathy, Denys-Drash, diabetic nephropathy, Alport syndrome, and other diseases related to the interaction between the podocyte and the glomerular basement membrane.

Angiotensin II type 1 receptor blockade inhibits the development and progression of HIV-associated nephropathy in a mouse model

HIV-associated nephropathy (HIVAN) is characterized by a collapsed glomerular capillary tuft with hyperplasia and hypertrophy of podocytes. Recently generated were conditional transgenic mice (podocin/Vpr) that express one of the HIV-1 accessory genes, vpr, selectively in podocytes using podocin promoter and Tet-on system. These transgenic mice developed renal injury similar to HIVAN when treated with doxycycline for 8 to 12 wk. This study demonstrated that nephron reduction by heminephrectomy markedly enhanced phenotypic changes of podocytes and led to severe FSGS within 4 wk. Nephrotic-range proteinuria was observed already at 2 wk, together with dedifferentiation and dysregulation of podocytes, indicated by decreased expression of nephrin, synaptopodin, and Wilms' tumor 1 protein and increased expression of Ki-67. The acceleration of phenotypic changes of podocytes, proteinuria, and subsequent glomerulosclerosis by heminephrectomy was almost completely inhibited by angiotensin II type 1 receptor (AT1R) blocker olmesartan. In contrast, the renoprotective effect of the calcium channel antagonist azelnidipine was minimal, although it lowered systemic BP to the same level as olmesartan, demonstrating that the inhibitory effect of AT1R blocker was independent of systemic BP. Olmesartan also reduced proteinuria and prevented glomerulosclerosis even by the delayed treatment, which was initiated after the podocyte injury appeared. These data suggest that nephron reduction exaggerates podocyte injury and subsequent glomerulosclerosis, possibly through glomerular hypertension, in the mouse model of HIVAN. AT1R blockade could be beneficial in the treatment of HIVAN by ameliorating podocyte injury by avoiding the vicious cycle of nephron reduction and glomerular hypertension.

A 20-year history of childhood HIV-associated nephropathy

In 1984, physicians in New York and Miami reported HIV-infected adult patients with heavy proteinuria and rapid progression to end-stage renal disease. These patients showed large edematous kidneys with a combination of focal segmental glomerulosclerosis (FSGS) and tubulointerstitial lesions. This renal syndrome, named HIV-associated nephropathy (HIVAN), was found predominantly in African Americans. Subsequent studies confirmed the presence of HIVAN in children, who frequently develop nephrotic syndrome in association with FSGS and/or mesangial hyperplasia with microcystic tubular dilatation. Since then, substantial progress has been made in our understanding of the etiology and pathogenesis of HIVAN. This article reviews 20 years of research into the pathogenesis of HIVAN and discusses how these concepts could be applied to the treatment of children with HIVAN. HIV-1 infection plays a direct role in the pathogenesis of childhood HIVAN, at least partially by affecting the growth and differentiation of glomerular and tubular epithelial cells and enhancing the renal recruitment of infiltrating mononuclear cells and cytokines. An up-regulation of renal heparan sulfate proteoglycans seems to play a relevant role in this process, by increasing the recruitment of heparin-binding growth factors (i.e., FGF-2), chemokines, HIV-infected cells, and viral proteins (i.e., gp120, Tat). These changes enhance the infectivity of HIV-1 in the kidney and induce injury and proliferation of intrinsic renal cells. Highly active anti-retroviral therapy (HAART) appears to be the most promising treatment to prevent the progression of childhood HIVAN. Hopefully, in the near future, better education, prevention, and treatment programs will lead to the eradication of this fatal childhood disease.

HIV-associated nephropathy: Epidemiology, pathogenesis, and treatment

Initially described in 1984, human immunodeficiency virus-associated nephropathy (HIVAN) has now become a common disease within the HIV-seropositive population. It is a focal segmental glomerulosclerosis causing rapid deterioration of renal function. It is the most common cause of chronic renal disease in HIV patients and occurs almost exclusively in blacks. Through murine and human studies, it is now clear that HIVAN is caused by a direct effect of infection of renal cells by HIV-1 and that the virus actively replicates within renal cells. How the virus causes disease within cells is not yet understood, but there is evidence for factors within infected cells causing both proliferation and apoptosis. Steroids, angiotensin converting enzyme (ACE) inhibitors, and highly active antiretroviral therapy (HAART) have been used for the treatment of HIVAN, with HAART, in particular, showing a dramatic improvement in both the pathologic changes and clinical course of HIVAN.

HIV-associated nephropathy in African Americans

Human immunodeficiency virus-1 (HIV-1) infection is associated with several glomerular syndromes, the most prevalent of which is HIV-associated focal segmental glomerulosclerosis (FSGS). At present, HIV-associated FSGS may account for up to 30% of patients in the United States entering end-stage renal disease (ESRD) as a consequence of FSGS. The mechanisms responsible for HIV-associated FSGS are not well defined, but evidence has been presented in favor of direct infection of renal parenchymal cells and toxicity of HIV-1 accessory proteins. HIV-associated FSGS has a striking predilection for patients of African descent. This likely has a genetic basis, although the gene or genes responsible have not yet been identified. One approach is to examine candidate genes for polymorphisms that are associated with disease. Another approach uses a genome-wide scan, relying upon linkage disequilibrium between DNA markers and the disease gene, to identify the causal gene or genes. African Americans are an admixed population, with genetic contributions from African, European, and Native American populations. In admixed populations, linkage disequilibrium between disease genes and marker genes can be exploited to identify disease genes, using an approach termed mapping by admixture linkage disequilibrium (MALD).

Renal Dysfunction in HIV-1-infected Patients

Improved therapy directed against opportunistic infection and HIV-1 itself has resulted in greatly enhanced patient survival in the past decade among patients infected with HIV-1. Since patients are living longer, HIV-1 infection is associated with a rising burden of kidney disease. Approximately 14% of black patients and 6% of white patients dying with HIV-1 infection in 1999 in the United States had renal disease. Overall, 10% of patients dying with HIV-1 infection had renal failure. The most common glomerular diseases are focal segmental glomerulosclerosis and immune complex glomerulonephritis. Appropriate therapy for focal segmental glomerulosclerosis includes effective antiretroviral therapy and angiotensin antagonist medication. Drug toxicity is also common, often manifesting as electrolyte abnormalities, acute renal failure, interstitial nephritis, or nephrolithiasis. In particular, indinavir is associated with crystalluria, nephrolithiasis, interstitial nephritis, and lower urinary tract inflammation. Appropriate screening for renal disease and appropriate intervention will likely reduce the morbidity and mortality associated with progressive renal disease.

HIV-associated nephropathy: case study and review of the literature

Human immunodeficiency virus type 1 (HIV-1)-seropositive patients are at risk for the development of a variety of acute and chronic renal diseases. The most common cause of chronic renal failure in HIV-1-seropositive patients is HIV-associated nephropathy (HIVAN). HIVAN occurs almost exclusively in black patients and the majority of published cases are of patients who present with acquired immunodeficiency syndrome (AIDS). This disease is currently the third leading cause of end-stage renal disease in blacks aged 20-64. Because HIV-1-seropositive patients may develop a wide variety of acute and chronic renal diseases, definitive diagnosis requires renal biopsy. Emerging data suggest a direct role of HIV-1 infection of kidney cells in the pathogenesis of HIVAN. There have been no well-controlled clinical trials in the treatment of HIVAN. The therapeutic agents with the most promise are angiotensin-converting enzyme inhibitors and antiretroviral medications. Long-term renal prognosis may be changing in the setting of improved aggressive antiretroviral therapy. Patient survival is determined primarily by the stage of HIV-1 infection. In this article, we present the case history of a patient who developed HIVAN. We then review the current literature concerning the epidemiology, differential diagnosis, etiology, and treatment of HIVAN.

Glomerulosclerosis and viral gene expression in HIV-transgenic mice: role of nef

BACKGROUND

Human immunodeficiency virus (HIV)-associated nephropathy is characterized by focal segmental glomerulosclerosis and microcystic tubular dilation. We have previously described a mouse transgenic for a Deltagag-pol HIV-1 genome, which develops glomerulosclerosis, cutaneous papillomas, and cataracts.

METHODS

We developed mice transgenic for a Deltagag-pol-nef HIV genome in order to investigate the role of the nef gene in these phenotypes.

RESULTS

One transgenic line, X5, expressed HIV mRNA in kidney and consistently manifested focal segmental glomerulosclerosis and tubular dilation by six weeks of age. Northern analysis indicated that renal transgene expression was higher in the Deltagag-pol-nef mice compared with the Deltagag-pol mice. In situ hybridization and immunostaining demonstrated HIV RNA and protein expression within the glomerular epithelial cells and tubular epithelial cells. These cell types showed histologic evidence of toxicity, including vacuolation and detachment from basement membrane, and exhibited increased rates of apoptosis. These data suggest that the renal disease seen in the Deltagag-pol-nef transgenic mouse may be caused by the expression of HIV genes within renal epithelial cells, that this expression may induce cellular toxicity, including apoptosis, and that nef is not required for the induction of renal disease. We have previously described mice bearing the nef gene, which do not manifest renal disease. In further experiments, Deltagag-pol-nef mice were bred with nef mice; these dual-transgenic mice developed renal disease that generally resembled that seen in Deltagag-pol-nef mice, but with somewhat more severe glomerulosclerosis and less severe tubulointerstitial injury.

RESULTS

The results of these transgenic studies suggest that the role of nef is complex and may act both to reduce transgene expression and to potentiate glomerular injury induced by other HIV-1 gene products.

Infection of mesangial cells with HIV and SIV: identification of GPR1 as a coreceptor

BACKGROUND

Mesangial cells are an important component of the glomerulus. Dysfunction of mesangial cells is thought to be involved in the development of human immunodeficiency virus type 1 (HIV-1)-associated nephropathy (HIVAN). HIVAN is a structural renal failure frequently observed in patients with acquired immune deficiency syndrome. However, the susceptibility of mesangial cells to HIV-1 is disputable. More than ten G protein-coupled receptors, including chemokine receptors, have been shown to act as HIV-1 coreceptors that determine the susceptibilities of cells to HIV-1 strains with specific cell tropisms.

METHODS

We examined the susceptibility of mesangial cells to various HIV-1, HIV type 2 (HIV-2) and simian immunodeficiency virus (SIV) strains. Expression of CD4 and HIV/SIV coreceptors was examined by Western blotting and polymerase chain reaction.

RESULTS

Mesangial cells were found to be susceptible to HIV-1 variant and mutants that infect brain-derived cells, but highly resistant to T-tropic (X4), M-tropic (R5) or dual-tropic (X4R5) HIV-1 strains. In addition, mesangial cells were also susceptible to HIV-2 and SIV strains that infect the brain-derived cells. Among HIV/SIV coreceptors we tested, the expression of GPR1 mRNA was detected in mesangial cells. Expression of CD4 mRNA and protein was also detected in them. Mesangial cells and GPR1-transduced CD4-positive cells showed similar susceptibilities to the HIV-1 variant and mutants and HIV-2 and SIV strains.

CONCLUSIONS

CD4 and GPR1 mRNAs were detected in mesangial cells. Mesangial cells were susceptible to HIV/SIV strains that use GPR1 as a coreceptor. Our findings suggest that an orphan G protein-coupled receptor, GPR1, is a coreceptor expressed in mesangial cells. It remains to be investigated whether the interaction of mesangial cells with specific HIV-1 strains through GPR1 plays a role in the development of HIVAN.

HIV-1 induces renal epithelial dedifferentiation in a transgenic model of HIV-associated nephropathy

BACKGROUND

Human immunodeficiency virus-associated nephropathy (HIVAN) is the most common cause of renal failure in HIV-1-seropositive patients. Recent studies using an HIV-1 transgenic mouse model have demonstrated that expression of HIV-1 in the kidney is required for the development of HIVAN. What has remained unclear, however, is the renal cell type responsible for pathogenesis and the essential pathological process.

METHODS

To address these issues, we used a transgenic murine model of HIVAN. We identified the cell types in kidney in which HIV transgene expression occurs using in situ hybridization. We evaluated evidence of proliferation by immunocytochemical analysis using an antibody to Ki-67 and cell type-specific markers, including WT-1, synaptopodin, Na+,K+-ATPase, adducin, and desmin. TUNEL assay was used to evaluate apoptosis.

RESULTS

We found that glomerular and tubular epithelial cells express the HIV-1 transgene early in the disease process when renal architecture is well preserved. Transgene expression is lost, however, in tubular epithelial cells when they lose their differentiated cuboidal phenotype. In glomerular epithelial cells, dedifferentiation occurs with reduced expression of WT-1 and synaptopodin, in association with activation of desmin expression. Tubular microcysts also form with mislocalization of Na+,K+-ATPase expression to the lateral and apical cellular membranes.

CONCLUSIONS

These studies support the hypothesis that the glomerular and renal epithelial cells are the primary targets of HIV-1 pathogenesis in the kidney. The essential pathologic process is dysregulation of the epithelial cell cycle with increased proliferation, apoptosis, cellular dedifferentiation, and altered cellular polarity.

Chemokine receptor CCR5 and CXCR4 expression in HIV-associated kidney disease

The chemokine receptors CCR5 and CXCR4 have been identified as essential coreceptors for entry of HIV-1 strains into susceptible cells. Direct infection of renal parenchymal cells has been implicated in the pathogenesis of HIV-associated renal disease, although data are conflicting. The localization of CCR5 and CXCR4 in kidneys with HIV-associated renal disease is unknown. Formalin-fixed, paraffin-embedded renal biopsies from patients with HIV-associated nephropathy (HIVAN) (n = 13), HIV-associated immune complex glomerulonephritis (n = 3), HIV-associated thrombotic microangiopathy (n = 1), and HIV-negative patients with collapsing glomerulopathy (n = 8) were analyzed in this study. Cellular sites of expression of CCR5 and CXCR4 were identified by immunohistochemistry and by in situ hybridization. The presence of HIV-1 was detected by immunohistochemistry and by in situ hybridization. Expression of both chemokine receptors CCR5 and CXCR4 was undetectable in intrinsic glomerular, tubular, and renovascular cells in all analyzed cases. In the presence of tubulointerstitial inflammation, CCR5 and CXCR4 expression was localized to infiltrating mononuclear leukocytes. HIV-1 protein was undetectable by immunohistochemistry in all cases of HIV-associated renal disease. HIV-1 RNA was identified in one case of HIVAN but was restricted to infiltrating leukocytes. HIV-1 RNA was not detected in intrinsic renal cells in all analyzed cases. Identifying the cellular expression of HIV-coreceptors CCR5 and CXCR4 may help to clarify which tissues are permissive for direct HIV infection. These data do not support a role of productive HIV-1 infection of renal parenchymal cells in the pathogenesis of HIV-associated renal disease.

Thrombotic microangiopathy in the HIV-2-infected macaque

Thrombotic microangiopathy (TMA) has been increasingly reported in human immunodeficiency virus (HIV)-infected humans over the past decade. The pathogenesis is unknown. We prospectively analyzed the renal pathology and function of 27 pigtailed macaques (Macaca nemestrina), infected intravenously with a virulent HIV-2 strain, HIV-2(287), in addition to that of four uninfected control macaques. Necropsies were performed between 12 hours and 28 days after infection. HIV-2 antigen was detectable in peripheral blood mononuclear cell (PBMC) cocultures in all animals after 10 days of HIV-2 infection; a rapid decline in CD4(+) PBMC (<350/microliter) was seen in five of six animals 21 days and 28 days after infection. No macaque developed features of clinical AIDS. Typical lesions of human HIV-associated nephropathy were undetectable. Six of the 27 HIV-2-infected macaques demonstrated both histological TMA lesions (thrombi in glomerular capillary loops and small arteries, mesangiolysis) and ultrastructural lesions (mesangiolysis, subendothelial lucency, platelet thrombi in glomerular capillary lumina). Extrarenal thrombi were detected in the gastrointestinal and adrenal microvasculature of macaques that had developed renal TMA. None of the control animals demonstrated features of renal TMA at necropsy. In a retrospective analysis of kidneys obtained from 39 additional macaques infected with HIV-2(287), seven cases demonstrated TMA. In situ hybridization showed no detectable HIV-2 RNA in kidney sections of 65/66 HIV-2-infected macaques, including all 13 TMA cases. Expression of the chemokine receptor CXCR4, the putative coreceptor for HIV-2(287), was absent in intrinsic renal cells in all HIV-2-infected macaques. The HIV-2-infected macaque may be a useful model of human HIV-associated TMA. Our data do not support a role of direct HIV-2 infection of intrinsic renal cells as an underlying mechanism.

HIV-1 kills renal tubular epithelial cells in vitro by triggering an apoptotic pathway involving caspase activation and Fas upregulation

HIV-infected patients suffer several renal syndromes, which can progress rapidly from renal insufficiency to end-stage renal disease. Histologically, HIV-induced nephropathy is characterized by prominent tubulopathy with apoptosis of tubular cells. Clinical and experimental evidence suggests that renal injury may be directly related to virus infection. Although HIV-1 is a polytropic and not solely lymphotropic pathogen, the susceptibility of renal cells to HIV-1 remains to be determined. This paper demonstrates in vitro the permissiveness of proximal tubular epithelial cells (PTEC) to HIV-1 and describes the effects of PTEC infection to explain the pathogenesis of tubular damage in vivo. The results indicate that PTEC express HIV-specific receptor and coreceptors and sustain virus replication. We observed that HIV-1 infection causes the death of tubular cells by triggering an apoptotic pathway involving caspase activation. Fas upregulation but not Fas ligand expression was found in the infected PTEC. However, after HIV-1 infection, tubular cells became susceptible to apoptosis induced through Fas stimulation. Caspase inhibition prevented the death of the infected PTEC in spite of persistent viral replication. These findings may explain the prominent histopathology of HIV-associated nephropathy and demonstrate that the apoptosis of nonlymphoid cells can be directly induced by HIV-1.

Chemokine receptor (CCR5) expression in human kidneys and in the HIV infected macaque

BACKGROUND

The chemokine receptor, CCR5, has been identified as an essential co-receptor with CD4, which permits entry of human immunodeficiency virus (HIV) into mammalian cells. This receptor may also mediate leukocyte and parenchymal responses to injury by virtue of its binding to locally released chemokines such as RANTES, MIP-1 alpha and MIP-1 beta during inflammation. The localization of CCR5 in human or primate kidney is unknown. In this study we sought to identify sites of CCR5 synthesis through localization of mRNA coding for this peptide.

METHODS

CCR5 cDNA cloned into an expression vector was transcribed into a 1.1 Kb antisense riboprobe that was utilized for in situ hybridization (ISH) and Northern blotting studies.

RESULTS

Northern analysis demonstrated positive hybridization for CCR5 mRNA in total RNA isolated from allograft nephrectomy tissue with features of severe transplant rejection as well as in kidney tissue with focal interstitial nephritis. No comparable hybridization signal was achieved with human kidney tissue uninvolved by disease. CCR5 mRNA was not identified in intrinsic renal cell types by ISH in normal human (N = 6), normal macaque kidney (N = 5), in kidneys from macaques with established infection by HIV-2 (N = 9), kidneys from macaques infected with HIV-1 (N = 4), nor in kidneys from SIV-infected macaques (N = 5). CCR5 was identified by ISH in human kidneys with features of interstitial nephritis (N = 3) and in rejected human allograft kidneys (N = 14). The expression of CCR5 was restricted to infiltrating mononuclear leukocytes at sites of chronic tubulointerstitial injury and at sites of vascular and interestitial rejection, respectively.

CONCLUSIONS

Understanding the localization of CCR5 as well as other chemokine receptors may help us understand how specificity in leukocyte trafficking is achieved in renal inflammatory processes such as allograft rejection and interstitial nephritis. They provide additional evidence that chemokines may be critical mediators of leukocyte trafficking in renal allograft rejection. These findings may account in part for the difficulty in demonstrating HIV infection of renal cells in human HIV infection, since these cells appear to lack constitutive expression of an essential co-receptor needed for viral entry.

Renal cell cytokine production stimulates HIV-1 expression in chronically HIV-1-infected monocytes

Renal infiltration of human immunodeficiency virus type 1 (HIV-1)-infected monocytes might play an important role in the development of HIV-associated nephropathy (HIVAN). In the present study, we investigated the effects of cytokines produced by cultured human mesangial cells (HMC) and proximal tubular epithelial cells (PTEC) on HIV-1 expression in chronically HIV-1-infected promonocytes (U1 cells). Human mesangial cells constitutively secreted interleukin-6 (IL-6) but not tumor necrosis factor-alpha (TNF-alpha) into the culture medium, whereas PTEC constitutively secreted both IL-6 and TNF-alpha. Coculture of U1 cells with HMC or PTEC for 72 hours markedly stimulated HIV-1 expression, with the p24 antigen concentration in the coculture supernatants ranging from approximately 200 to 1850 pg/ml. The presence of anti-IL-6 antibody in the coculture medium nearly completely blocked HIV-1 expression in the HMC/U1 cell cocultures (P < 0.05). Anti-IL-6 antibody and anti-TNF-alpha antibody blocked HIV-1 expression in the PTEC/U1 cell cocultures by 40% and 53%, respectively (P < 0.05). Moreover, the combination of anti-IL-6 and anti-TNF-alpha antibodies additively reduced coculture HIV-1 expression by 87% (P < 0.05). We conclude that renal cell production of IL-6 and TNF-alpha might provide a potent stimulus for HIV-1 expression in HIV-1-infected monocytes that infiltrate the kidney, and that this may play an important role in the pathogenesis of HIVAN.

Distinct pathogenic effects of group B coxsackieviruses on human glomerular and tubular kidney cells

The six group B coxsackieviruses (CVBs) are highly prevalent human pathogens that cause viremia followed by involvement of different organs. Clinical and experimental evidence suggests that CVBs can induce kidney injury, but the susceptibility of human renal cells to these viruses is unknown. By using pure cultures of human glomerular and tubular cells, we demonstrated that all CVBs are capable of productively infecting renal cells of three different histotypes. Distinct pathogenic effects were observed. Proximal tubular epithelial cells and, to a lesser extent, glomerular podocytes were highly susceptible to CVBs; in both cases, infection led to cytolysis. In contrast, glomerular mesangial cells supported the replication of the six CVBs but failed to develop overt cytopathologic changes. Mesangial cells continued to produce infectious progeny for numerous serial subcultures (i.e., more than 50 days), especially with type 1, 3, 4, and 5 viruses. In the above cells, persistent infection induced the de novo synthesis of platelet-derived growth factor A/B and enhanced the release of transforming growth factor beta1/2. These two factors are important mediators of progression from glomerular inflammation to glomerulosclerosis. CVB replication appeared also to impair the phagocytic and contractile activity of mesangial cells. Loss of these properties--which are important in glomerular physiopathology--may contribute to the development of progressive nephropathy. The results show that CVBs induce distinct effects in different types of cultured renal cells and suggest that CVB infections may be associated with both acute and progressive renal injury.

Nephropathy in human immunodeficiency virus-1 transgenic mice is due to renal transgene expression

HIV-associated nephropathy (HIVAN) is a progressive glomerular and tubular disease that is increasingly common in AIDS patients and one of the leading causes of end stage renal disease in African Americans. A major unresolved issue in the pathogenesis of HIVAN is whether the kidney disease is due to renal cell infection or a "bystander" phenomenon mediated by systemically dysregulated cytokines. To address this issue, we have used two different experimental approaches and an HIV-1 transgenic mouse line that develops a progressive renal disease histologically similar to HIVAN in humans. In the murine model, kidney tissue expresses the transgene and in heterozygous adults, renal disease develops shortly thereafter. We demonstrate by terminal deoxynucleotide transferase-mediated dUTP-biotin nick-end labeling assay that similar to the disease in humans, apoptosis of renal tubular epithelial cells is a component of the molecular pathogenesis. To determine whether apoptosis is due to transgene expression or environmental factors, we treated fetal kidney explants (normal and transgenic) with UV light to induce transgene expression. Apoptosis occurred in transgenic but not normal littermates after stimulation of transgene expression. To confirm a direct effect of HIV expression on the production of HIVAN, we transplanted kidneys between normal and transgenic mice. HIVAN developed in transgenic kidneys transplanted into nontransgenic littermates. Normal kidneys remained disease free when transplanted into transgenic littermates. Thus, the renal disease in the murine model is intrinsic to the kidney. Using two different experimental approaches, we demonstrate a direct effect of transgene expression on the development of HIVAN in the mouse. These studies suggest that in humans, a direct effect of HIV-1 expression is likely the essential cause of HIVAN, rather than an indirect effect of cytokine dysregulation.

Focal segmental glomerulosclerosis in primates infected with a simian immunodeficiency virus

Focal and segmental glomerulosclerosis (FSG) with endothelial tubuloreticular inclusions (TRIs) is the typical lesion of human HIV-associated glomerulopathy. Autopsy studies showed the presence of FSG in 3 of 15 macaques dying 15-120 weeks after experimental infection with a simian immunodeficiency virus (SIVMne). Ultrastructural studies generally revealed numerous endothelial TRIs (also present in normals), mesangial expansion, and evidence of mesangial cell injury. One additional animal had a small-vessel polyarteritis with a proliferative and focally crescentic glomerulonephritis; seven animals had mild, multifocal interstitial nephritis. All animals had documented viremia after infection; 14 of 15 developed antibodies to SIV postinoculation. Additional postmortem findings included severe enterocolitis, encephalitis, and opportunistic infections. In contrast, autopsy studies of macaques infected with a type D simian retrovirus (SAIDS-D/Washington, SRV-2) for similar periods of time (n = 40) showed no evidence of FSG. One SRV-infected animal had a mild proliferative glomerulonephritis. These studies indicate SIV-infected primates may provide a relevant model for study of human HIV-associated nephropathy. They also indicate the variable pathology that can be seen in primate infections of distinct retrovirus types, each of which produces a simian immunodeficiency state that resembles human AIDS.

Human immunodeficiency virus-associated glomerulosclerosis

The constellation of nephrotic proteinuria, FSGS, and rapid loss of renal function in a patient infected with HIV-1 has been sufficiently widespread and well documented to justify identification as a specific renal syndrome, HIV-associated nephropathy. The position paper of the National Kidney Foundation-National Institutes of Health task force estimated in 1990 that 10,000 to 15,000 persons will develop renal disease in association with AIDS [94]. Management of these patients is complex, and many will reach ESRD and require dialysis treatment, posing additional care problems. Greater understanding of the pathogenesis of the renal disease should lead to treatments which will forestall the development of HIVAN and possibly other forms of fibrotic renal disease. The ultimate eradication of AIDS will consign this renal syndrome to an interesting footnote in the history of nephrology. Since that time is still far in the future, nephrologists will continue to be faced with the need to diagnose and treat HIV-1-infected patients with renal involvement.

Viral DNA in microdissected renal biopsy tissue from HIV infected patients with nephrotic syndrome

Focal glomerulosclerosis (FGS) has been considered as HIV-associated nephropathy, a specific renal complication of infection. To determine whether renal disease in HIV infected patients has one highly prevalent pathologic expression, and whether renal parenchymal viral genomic incorporation affects pathologic outcome, we reviewed renal biopsies performed at our center. Twenty-eight HIV infected patients with nephrotic range proteinuria underwent renal biopsy for diagnosis of renal disease: 85.7% led homosexual or bisexual lifestyles; 10.7% admitted to intravenous drug use; and 85.7% were Black. Only 53.6% had FGS; 28.6% had glomerulonephritis. Two patients had diabetic renal disease; 93.3% of patients with FGS and 87.5% of patients with glomerulonephritis were Black. Paraffin slides of twenty-two of the patients' renal biopsies were evaluated by polymerase chain reaction (PCR) for the presence of HIV DNA, using primers and probes to the gag gene, detected by liquid hybridization and polyacrylamide gel electrophoresis. Twenty-one of the twenty-two evaluated tissue specimens showed the presence of HIV DNA. Microdissection studies of glomeruli, tubules, interstitial cells and infiltrating inflammatory cells showed the presence of HIV genome in all but interstitial cells. HIV infected patients without renal disease also had positive PCR evaluations of microdissected tissue, while non-infected patients were all negative. We conclude that although focal glomerulosclerosis is the most common renal pathologic lesion in patients with HIV infection and nephrotic range proteinuria, glomerulonephritis is a relatively frequent finding. HIV genome is present in renal tissue in HIV infected subjects with nephrotic range proteinuria, but is also found in HIV infected subjects without nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)