HIV-1 and HIV-Associated Nephropathy 25 Years Later

Prevalence and Risk Factors for Renal Insufficiency among Adults Living with HIV in Tanzania: Results from a Cross-Sectional Study in 2020-2021

With improved survival, adults living with HIV (ALHIV) are increasingly likely to experience age-related and HIV-related comorbidities, including renal insufficiency. Other risk factors for renal insufficiency (high blood pressure (BP), obesity, diabetes, and dyslipidemia) are also growing more common among ALHIV. To determine the prevalence of renal insufficiency (defined as an eGFR < 60 mL/min/1.73 m2) and factors associated with reduced eGFR, we conducted a cross-sectional study at six HIV clinics in Dar-es-Salaam, Tanzania. We applied multivariable (MV) ordinal logistic regression models to identify factors associated with reduced eGFR and examined the interaction of age with BP levels. Among the 450 ALHIV on ART analyzed [26% males; median age 43 (IQR: 18-72) years; 89% on tenofovir-containing ART; 88% HIV viral load ≤50 copies/mL], 34 (7.5%) had renal insufficiency. Prevalence was higher among males (12%) vs. females (6%), p = 0.03; ALHIV ≥50 (21%) vs. <50 years (2.5%), p < 0.001; those with high [≥130/80 mmHg (15%)] vs. normal [<120/80 mmHg (4%)] BP, p < 0.01 and those with dyslipidemia (10%) vs. those without (4.5%), p < 0.03. After adjusting for covariates, age (in years) was the only covariate with a statistically significant association with reduced eGFR (OR = 1.09 (1.07-1.12), p < 0.001). No significant interaction between age and BP was found. Interventions to increase routine screening for renal insufficiency, especially among older ALHIV, and improve BP control are critical to reducing kidney disease-related morbidity and mortality.

ANCA-associated vasculitis in a HIV-infected patient:a case-based review

BACKGROUND

The occurrence of autoantibodies in human immunodeficiency virus (HIV)-infected patients has been previously reported, with a prevalence ranging from 20 to 83%. There are also a few reports of clinically relevant autoantibody profiles in HIV-positive patients that lead to true systemic autoimmune disease; these possible life-threatening diseases have to be considered and treated accordingly.

CASE PRESENTATION

Here, we present the case of a 29-year-old female patient with a history of well-controlled HIV infection in the last 6 years who was admitted to our department for the evaluation of acute kidney injury and nephrotic syndrome with active urinary sediment. A diagnosis of systemic antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) with renal and pulmonary involvement was established. The patient was treated with cyclophosphamide, rituximab and tapering glucocorticoids,and the diffuse alveolar hemorrhage resolved, but the evolution of kidney function was unfavorable, which led to the need to initiate hemodialysis. We highlight the importance of establishing the correct diagnosis, treating the disease accordingly and the possible clinical issues that can appear in a patient with HIV infection during immunosuppressant treatment as induction treatment. Additionally, we performed a thorough literature review of ANCA positivity in HIV-infected patients to properly understand the current evidence.

CONCLUSIONS

Although it is not clear whether HIV infection and AAV are causally or coincidentally related, the possibility of this systemic autoimmune phenomenon should be acknowledged by physicians to establish the correct diagnosis and treat the disease accordingly by maintaining a balance between the risks and benefits of immunosuppression in this category of patients, with treatment decisions being made by the members of a multidisciplinary team in centers with experience in AAV.

APOL1 Renal Risk Variants and Kidney Function in HIV-1–Infected People From Sub-Saharan Africa

Introduction

APOL1 G1 and G2 alleles have been associated with kidney-related outcomes in people living with HIV (PLHIV) of Black African origin. No APOL1-related kidney risk data have yet been reported in PLHIV in West Africa, where high APOL1 allele frequencies have been observed.

Methods

We collected clinical data from PLHIV followed in Burkina Faso (N = 413) and in the ANRS-12169/2LADY trial (Cameroon, Senegal, Burkina Faso, N = 369). APOL1 G1 and G2 risk variants were genotyped using TaqMan assays, and APOL1 high-risk (HR) genotype was defined by the carriage of 2 risk alleles.

Results

In West Africa (Burkina Faso and Senegal), the G1 and G2 allele frequencies were 13.3% and 10.7%, respectively. In Cameroon (Central Africa), G1 and G2 frequencies were 8.7% and 8.9%, respectively. APOL1 HR prevalence was 4.9% in West Africa and 3.4% in Cameroon. We found no direct association between APOL1 HR and estimated glomerular filtration rate (eGFR) change over time. Nevertheless, among the 2LADY cohort participants, those with both APOL1 HR and high baseline viral load had a faster eGFR progression (β = −3.9[−7.7 to −0.1] ml/min per 1.73 m² per year, P < 0.05) than those with low-risk (LR) genotype and low viral load.

Conclusion

Overall, the APOL1 risk allele frequencies in PLHIV were higher in the West African countries than in Cameroon, but much lower than previously reported in some Nigeria ethnic groups, which strongly advocates for further investigation in the African continent. This study suggested that the virological status could modulate the APOL1 impact on kidney function, hence reinforcing the need for early therapeutic interventions.

Profiling Biomarkers in HIV Glomerular Disease – Potential for the Non-Invasive Diagnosis of HIVAN?

Background

There is a wide spectrum of kidney pathology in human immunodeficiency virus (HIV) infection, affecting all structures of the kidney. The histology of HIV chronic kidney disease (CKD) is diverse, ranging from HIV-associated nephropathy (HIVAN) to focal glomerulosclerosis (FSGS), HIV-immune complex disease (HIV-ICD), other glomerulopathies and tubulo-interstitial nephritis. Definitive diagnosis is by kidney biopsy, an invasive procedure. However, serum and urinary biomarkers may be useful in predicting the histological diagnosis of HIVAN.

Purpose

We wished to determine the utility of serum and urinary biomarkers in predicting the histological diagnosis of HIVAN.

Patients and Methods

We measured neutrophil gelatinase-associated lipocalin (NGAL), cystatin C, transforming growth factor (TGF)-β isoforms and bone morphogenetic protein (BMP)-7 in the serum and urine in patients with different histological forms of HIV glomerular disease.

Results

In HIVAN, we demonstrated increased levels of serum cystatin C and increased levels of serum and urinary NGAL. Urinary TGF-β1 and TGF-β2 levels were elevated in HIV-positive patients with CKD but were not significantly different in the different HIV histologies, while urinary BMP-7 levels were elevated in minimal change disease.

Conclusion

This study confirmed the presence of increased serum and urinary biomarkers of tubular injury in patients with HIVAN, and increased urinary biomarkers of fibrosis in HIV CKD, and may indicate their value as a non-invasive diagnostic tool for the diagnosis of HIVAN.

Pharmacotherapeutic options for kidney disease in HIV positive patients

INTRODUCTION

Since the developmentof combined antiretroviral therapy (cART), HIV-associated mortality and the incidence of HIV-associated end-stage kidney disease (ESKD) has decreased. However, in the United States, an increase in non-HIV-associated kidney diseases within the HIV-positive population is expected.

AREAS COVERED

In this review, the authors highlight the risk factors for kidney disease within an HIV-positive population and provide the current recommendations for risk stratification and for the monitoring of its progression to chronic kidney disease (CKD), as well as, treatment. The article is based on literature searches using PubMed, Medline and SCOPUS.

EXPERT OPINION

The authors recommend clinicians (1) be aware of early cART initiation to prevent and treat HIV-associated kidney diseases, (2) be aware of cART side effects and discriminate those that may become more nephrotoxic than others and require dose-adjustment in the setting of eGFR ≤ 30ml/min/1.73m², (3) follow KDIGO guidelines regarding screening and monitoring for CKD with a multidisciplinary team of health professionals, (4) manage other co-infections and comorbidities, (5) consider changing cART if drug induced toxicity is established with apparent eGFR decline of ≥ 10ml/min/1.73m² or rising creatinine (≥0.5mg/dl) during drug-drug interactions, and (6) strongly consider kidney transplant in appropriately selected individuals with end stage kidney failure.

Association of HIV Suppression With Kidney Disease Progression Among HIV-Positive African Americans With Biopsy-Proven Classic FSGS

BACKGROUND

In the era of combined antiretroviral therapy, classic focal segmental glomerulosclerosis (FSGS) is the most common histopathological finding in African American HIV-positive patients with kidney disease. We sought to determine whether HIV suppression is associated with lower risk of progression to end-stage renal disease (ESRD) among HIV-positive African Americans with biopsy-confirmed classic FSGS.

METHODS

HIV-positive African Americans who underwent kidney biopsies at a single tertiary hospital between January 1996 and June 2011 were confirmed as having classic FSGS by the presence of segmental glomerulosclerosis without features of HIV-associated nephropathy. Multivariable Cox proportional hazards models were used to examine the independent association of viral suppression (HIV-RNA < 400 copies per milliliter at biopsy) with time to progression to ESRD.

RESULTS

Of the 55 HIV-positive African Americans with classic FSGS, 26 had suppressed viral loads at the time of biopsy. Compared to viremic patients, those who were virally suppressed had a significantly higher mean CD4 cell count (452 vs. 260 cell/mm, respectively; P = 0.02) and median estimated glomerular filtration rate (53.5 vs 35.5 mL/min/1.73 m, respectively; P = 0.002). Adjusting for sex and baseline CD4 cell count, estimated glomerular filtration rate, and proteinuria, those with HIV-RNA levels <400 copies per milliliter at baseline had a 75% lower risk of progressing to ESRD (hazard ratio = 0.25; 95% CI: 0.07 to 0.88) during a median follow-up time of 2.70 years (interquartile range: 0.80-5.15 years).

CONCLUSIONS

HIV suppression is associated with significantly lower risk of progression to ESRD among HIV-infected African Americans with classic FSGS, supporting the potential role of combined antiretroviral therapy for this histopathology in addition to HIV-associated nephropathy among HIV-positive individuals.

HIV in the dialysis population: Current issues and future directions

Antiretroviral therapy has significantly reduced mortality due to HIV infection, but the aging HIV-positive patient population now faces a growing burden of comorbidity. This review describes the changing epidemiology of chronic kidney disease and end-stage renal disease in this population, and highlights recent advances in antiretroviral therapy and kidney transplantation that directly impact the care of patients with HIV infection and end-stage renal disease.

Infectious Diseases and the Kidney in Children

The kidney is involved in a wide range of bacterial, viral, fungal, and parasitic diseases. In most systemic infections, renal involvement is a minor component of the illness, but in some, renal failure may be the presenting feature and the major problem in management. Although individual infectious processes may have a predilection to involve the renal vasculature, glomeruli, interstitium, or collecting systems, a purely anatomic approach to the classification of infectious diseases affecting the kidney is rarely helpful because most infections may involve several different aspects of renal function. In this chapter, a microbiological classification of the organisms affecting the kidney is adopted. Although they are important causes of renal dysfunction in infectious diseases, urinary tract infections and hemolytic uremic syndrome (HUS) are not discussed in detail because they are considered separately in chapters XX and XX, respectively.

Ambulatory blood pressure profiles in a subset of HIV-positive patients pre and post antiretroviral therapy

OBJECTIVES

Human immunodeficiency virus (HIV) and antiretroviral therapy (ART) are associated with renal disease and increased cardiovascular risk. The relationship between HIV and ambulatory blood pressure (ABP) non-dipping status, a risk factor for cardiovascular events and target-organ damage, has never been assessed in South Africa. Study objectives were to establish the prevalence of chronic kidney disease, and assess the ABP profile in asymptomatic HIV-positive clinic out-patients.

METHODS

This was a prospective cohort study. Office blood pressure (BP), urinary microalbumin-creatinine ratio, urine dipsticks, serum creatinine and estimated glomerular filtration rate (eGFR) were measured at baseline and six months after ART initiation. A subset of HIV-positive subjects and an HIV-negative control group underwent 24-hour ABP monitoring.

RESULTS

No patient had an eGFR < 60 ml/min, three patients (4.7%) had microalbuminuria and one had macroalbuminuria. Mean office systolic BP was 111 ± 14 mmHg at baseline and increased by 5 mmHg to 116 ± 14 mmHg (p = 0.05) at six months. This increase was not confirmed by ABP monitoring. In the HIV-positive and -negative patients, the prevalences of non-dipping were 80 and 52.9%, respectively (p = 0.05, odds ratio = 3.56, 95% CI: 0.96-13.13). No relationship between dipping status and ART usage was found.

CONCLUSION

The prevalence of chronic kidney disease (CKD) was lower than anticipated. HIV infection was associated with an ambulatory non-dipping status, which suggests an underlying dysregulation of the cardiovascular system. In the short term, ART does not seem to improve loss of circadian rhythm.

Proteinuria in paediatric patients with human immunodeficiency virus infection

In human immunodeficiency virus (HIV)-infected people kidney disease is as an important cause of morbidity and mortality. Clinical features of kidney damage in HIV-infected patients range from asymptomatic microalbuminuria to nephrotic syndrome. The lack of specific clinical features despite the presence of heavy proteinuria may mask the renal involvement. Indeed, it is important in HIV patients to monitor renal function to early discover a possible kidney injury. After the introduction of antiretroviral therapy, mortality and morbidity associated to HIV-infection have shown a substantial reduction, although a variety of side effects for long-term use of highly active antiretroviral therapy, including renal toxicity, has emerged. Among more than 20 currently available antiretroviral agents, many of them can occasionally cause reversible or irreversible nephrotoxicity. At now, three antiretroviral agents, i.e., indinavir, atazanavir and tenofovir disoproxil fumarate have a well established association with direct nephrotoxicity. This review focuses on major causes of proteinuria and other pathological findings related to kidney disease in HIV-infected children and adolescents.

Prevalence of proteinuria and elevated serum cystatin C among HIV-Infected Adolescents in the Reaching for Excellence in Adolescent Care and Health (REACH) study

OBJECTIVE

In the United States, kidney dysfunction is prevalent in almost 30% of HIV-infected patients and is an independent predictor of mortality. Proteinuria and elevated serum cystatin C (eCysC) are used as markers of kidney disease in the general population; however, the prevalence of these markers in HIV-infected adolescents is largely unknown.

METHODS

This study includes 304 HIV-infected adolescents from the Reaching for Excellence in Adolescent Care and Health (REACH) cohort, an observational study of adolescents recruited from 13 US cities. Clinical and demographic characteristics of participants were evaluated as correlates of proteinuria, a urine protein to creatinine ratio of ≥200 mg/g. Select univariate predictors were assessed to determine the association with urinary protein excretion and serum cystatin C in multivariable linear regression models and proteinuria and eCysC (eCysC ≥ 75th percentile) in multivariable logistic regression models.

RESULTS

Overall, 19.1% of the participants had proteinuria, whereas 23.7% had an eCysC. Low CD4 T-lymphocyte counts (<200 cells/mm) were significantly associated with a greater urine protein to creatinine ratio in linear models and with proteinuria in logistic regression models. CD4 T-lymphocyte counts <500 cells/mm were significantly associated with a greater serum cystatin C concentration in linear models and with eCysC in logistic regression models.

CONCLUSIONS

Proteinuria among HIV-infected adolescents in the REACH cohort was approximately 2-fold greater than healthy US adolescents. Both proteinuria and eCysC are associated with CD4 T-lymphocyte counts. Further studies investigating early markers of kidney disease and the association with immune status and inflammation in HIV-infected adolescents are needed.

Down-regulation of NF-κB transcriptional activity in HIV-associated kidney disease by BRD4 inhibition

NF-κB-mediated inflammation is the major pathology in chronic kidney diseases, including HIV-associated nephropathy (HIVAN) that ultimately progresses to end stage renal disease. HIV infection in the kidney induces NF-κB activation, leading to the production of proinflammatory chemokines, cytokines, and adhesion molecules. In this study, we explored selective inhibition of NF-κB transcriptional activity by small molecule blocking NF-κB binding to the transcriptional cofactor BRD4, which is required for the assembly of the productive transcriptional complex comprising positive transcription elongation factor b and RNA polymerase II. We showed that our BET (Bromodomain and Extra-Terminal domain)-specific bromodomain inhibitor MS417, designed to block BRD4 binding to the acetylated NF-κB, effectively attenuates NF-κB transcriptional activation of proinflammatory genes in kidney cells treated with TNFα or infected by HIV. MS417 ameliorates inflammation and kidney injury in HIV-1 transgenic mice, an animal model for HIVAN. Our study suggests that BET bromodomain inhibition, targeting at the proinflammatory activity of NF-κB, represents a new therapeutic approach for treating NF-κB-mediated inflammation and kidney injury in HIVAN.

Renal disease in an urban HIV population in the era prior and following the introduction of highly active antiretroviral therapy

Renal disease related to human immunodeficiency virus (HIV) has been a past and present burden on the HIV positive community, both in the United States and worldwide. Previously, focus has been on the impact of HIV-associated nephropathy (HIVAN) on the black population. This paper presents a large renal biopsy series of 108 HIV patients from an urban setting with early renal dysfunction. The purpose of the paper is to highlight clinical characteristics and epidemiological changes in HIV-related renal disease between 2 distinct time periods: pre- and postintroduction of highly active antiretroviral therapy. Our data show a persistence of HIVAN in the black HIV US population and, in addition, an increase in other renal diseases in that population. These findings are discussed in regard to current and future HIV renal disease management.

Identification of the nephropathy-susceptibility locus HIVAN4

HIVAN1, HIVAN2, and HIVAN3 are nephropathy-susceptibility loci previously identified in the HIV-1 transgenic mouse, a model of collapsing glomerulopathy. The HIVAN1 and HIVAN2 loci modulate expression of Nphs2, which encodes podocin and several other podocyte-expressed genes. To identify additional loci predisposing to nephropathy, we performed a genome-wide scan in 165 backcross mice generated between the nephropathy-sensitive HIV-1-transgenic FVB/NJ (TgFVB) strain and the resistant Balb/cJ (BALB) strain. We identified a major susceptibility locus (HIVAN4) on chromosome 6 G3-F3, with BALB alleles conferring a twofold reduction in severity (peak LOD score = 4.0). Similar to HIVAN1 and HIVAN2, HIVAN4 modulated expression of Nphs2, indicating a common pathway underlying these loci. We independently confirmed the HIVAN4 locus in a sister TgFVB colony that experienced a dramatic loss of nephropathy subsequent to a breeding bottleneck. In this low-penetrance line, 3% of the genome was admixed with BALB alleles, suggesting a remote contamination event. The admixture localized to discrete segments on chromosome 2 and at the HIVAN4 locus. HIVAN4 candidate genes include killer lectin-like receptor genes as well as A2m and Ptpro, whose gene products are enriched in the glomerulus and interact with HIV-1 proteins. In summary, these data identify HIVAN4 as a major quantitative trait locus for nephropathy and a transregulator of Nphs2. Furthermore, similar selective breeding strategies may help identify further susceptibility loci.

Collapsing glomerulopathy in an HIV-positive patient in a low-incidence belt

Human immunodeficiency virus (HIV) involves glomerular, tubulointerstitial, and vascular compartments of the kidney. The most common glomerular lesion is HIV-associated focal segmental glomerulosclerosis (FSGS) and related mesangiopathies collectively termed HIV-associated nephropathy (HIVAN). A variety of immune-complex mediated glomerular diseases such as membranoproliferative glomerulonephritis (MPGN), IgA nephropathy, and lupus-like glomerulonephritis also occur. HIVAN is restricted to patients presenting with proteinuria and progressive reduction of renal function and with distinctive but not pathognomonic pathology (FSGS often coexisting with glomerular collapse and tubular microcystic dilatations). The worldwide incidence of collapsing glomerulopathy (CG) in HIV-positive patients is high in Americans. But in India and other Asian countries, other forms of kidney diseases are more commonly seen. We report the first case of CG in the state of Jammu and Kashmir which also happens to be a very low incidence belt for HIV.

Urinary NGAL is a useful clinical biomarker of HIV-associated nephropathy

BACKGROUND

Urinary neutrophil gelatinase-associated lipocalin (uNGAL) is expressed by kidney tubules that are acutely damaged, but few studies have investigated the association of neutrophil gelatinase-associated lipocalin (NGAL) with different forms of chronic kidney disease (CKD). HIV-associated nephropathy (HIVAN) is a progressive form of CKD characterized by collapsing focal segmental glomerulosclerosis and microcytic tubular dilatation that typically leads to end-stage renal disease (ESRD).

METHODS

Previously, we reported that microcystic tubular dilatations specifically expressed NGAL RNA, implying that the detection of uNGAL protein could mark advanced HIVAN. To test this idea, we performed a comparative study of diverse proteinuric glomerulopathies in 25 patients who were HIV positive.

RESULTS

Eighteen patients had HIVAN and seven had other glomerulopathies (four membranoproliferative glomerulonephritis, one membranous glomerulonephritis, one amyloid and one malarial GN). HIVAN and non-HIVAN patients did not differ with respect to age, ethnicity, serum creatinine, estimated GFR, proteinuria or the prevalence of hypocomplementemia (6 versus 29%, P = 0.18), but HIVAN patients were less likely to have HCV infections. HIVAN patients expressed 4-fold higher levels of uNGAL than the patients with other glomerulopathies [387 ± 338 versus 94 ± 101 μg/g urine creatinine (uCr), P = 0.02]. A cutpoint of 121.5 μg uNGAL/g uCr demonstrated 94% sensitivity and 71% specificity for the diagnosis of HIVAN, with an area under the receiver operator characteristic curve of 0.88.

CONCLUSION

In summary, while HIVAN disease is currently diagnosed only by kidney biopsy, uNGAL can distinguish HIVAN from other proteinuric glomerulopathies in the HIV-infected patient, likely because of its specific expression from characteristic microcysts.

Treatment of HIV-associated nephropathies

In patients with HIV, the use of highly active antiretroviral therapy has improved life expectancy. At the same time, this increase in life expectancy has been associated with a higher frequency of chronic kidney disease due to factors other than HIV infection. Besides HIV-associated nephropathy, a number of different types of immune complex and non-immune complex-mediated processes have been identified on kidney biopsies, including vascular disease (nephrosclerosis), diabetes, and drug-related renal injury. In this setting, renal biopsy needs to be considered in order to obtain the correct diagnosis in individual patients with HIV and kidney impairment. Many issues regarding the optimal treatment of the different pathological processes affecting the kidneys of these patients have remained unresolved. Further research is needed in order to optimize treatment and renal outcomes in patients with HIV and kidney disease.

Role of the retinoic acid receptor-α in HIV-associated nephropathy

All-trans retinoic acid protects against the development of HIV-associated nephropathy (HIVAN) in HIV-1 transgenic mice (Tg26). In vitro, all-trans retinoic acid inhibits HIV-induced podocyte proliferation and restores podocyte differentiation markers by activating its receptor-α (RARα). Here, we report that Am580, a water-soluble RARα-specific agonist, attenuated proteinuria, glomerosclerosis, and podocyte proliferation, and restored podocyte differentiation markers in kidneys of Tg26 mice. Furthermore, RARα-/- Tg26 mice developed more severe kidney and podocyte injury than did RARα+/- Tg26 mice. Am580 failed to ameliorate kidney injury in RARα-/- Tg26 mice, confirming our hypothesis that Am580 acts through RARα. Although the expression of RARα-target genes was suppressed in the kidneys of Tg26 mice and of patients with HIVAN, the expression of RARα in the kidney was not different between patients with HIVAN and minimal change disease. However, the tissue levels of retinoic acid were reduced in the kidney cortex and isolated glomeruli of Tg26 mice. Consistent with this, the expression of two key enzymes in the retinoic acid synthetic pathway, retinol dehydrogenase type 1 and 9, and the overall enzymatic activity for retinoic acid synthesis were significantly reduced in the glomeruli of Tg26 mice. Thus, a defect in the endogenous synthesis of retinoic acid contributes to loss of the protection by retinoic acid in HIVAN. Hence, RARα agonists may be potential agents for the treatment of HIVAN.

Activation of Notch signaling pathway in HIV-associated nephropathy

OBJECTIVE

HIV-associated nephropathy (HIVAN) is characterized by the development of glomerulosclerosis and is associated with glomerular epithelial cell proliferation. It has recently been shown that activation of the Notch signaling pathway in podocytes results in glomerulosclerosis and podocyte proliferation. To determine whether Notch signaling is involved in renal disorder associated with HIVAN, we evaluated the expression of Notch receptors in HIVAN.

DESIGN

We evaluated the expression of the Notch signaling pathway using an HIV-transgenic (HIV-Tg) rat model of HIVAN, and biopsy samples from HIVAN and normal controls.

METHODS

Paraffin sections and kidney lysates were used for immunohistochemistry, immunofluorescence and western blot analysis.

RESULTS

A collapsing variant of glomerulosclerosis and focal segmental sclerosis was observed in HIV-Tg rats. Glomeruli of HIV-Tg rats demonstrated activation of Notch1 and Notch4, as determined by the presence of the intracellular domains. In addition, we observed increased expression of the Notch target protein, hairy enhancer of split homolog-1 in glomeruli of these animals. The expression of the Groucho homolog transducin-like enhancer protein 4, a Notch effector protein, and the homeodomain protein cut homeobox 1 were also significantly increased in glomeruli of HIV-Tg rats, and this was associated with decreased expression of the cyclin kinase inhibitor p27. Intriguingly, renal biopsy samples from HIVAN patients also showed upregulation of cleaved Notch1 and Notch4 in the glomeruli compared with the expression in normal kidneys.

CONCLUSION

Our results demonstrate activation of Notch signaling pathway in HIVAN, thereby underscoring its role in disease pathogenesis.

CKD in HIV-infected patients other than HIV-associated nephropathy

A spectrum of kidney diseases in HIV-infected patients has been reported both before and after the introduction of highly active antiretroviral therapy (HAART). Kidney syndromes affecting HIV-infected patients include CKD as well as proteinuria, nephrotic syndrome, and acute nephritic syndrome. Thrombotic microangiopathy should be considered in patients with kidney disease and typical clinical characteristics. As the HIV-infected population ages, there is increased concern regarding the incidence of vascular and metabolic disease, leading to an increased burden of CKD. Although HIV-associated nephropathy is still the major cause of nephrotic syndrome in HIV-infected patients, immune complex glomerulonephritis (ICGN) still comprises a substantial proportion of the disease burden, especially in people of European origin. Genetic investigations into the underpinnings of the various histologic expressions of HIV-associated kidney disease hold great promise. The single most important diagnostic test to differentiate various forms of kidney disease in HIV-infected patients is a kidney biopsy. The results of treating kidney disease in HIV-infected patients remain unclear, and properly designed randomized controlled trials of the treatment of ICGN with HAART and other approaches are desperately needed.

Reduction of Stat3 activity attenuates HIV-induced kidney injury

HIV-1 Nef induces podocyte proliferation and dedifferentiation by activating the Stat3 and MAPK1,2 pathways. Activation of Stat3 also occurs in human kidneys affected by HIV-associated nephropathy (HIVAN), but its contribution to the development of HIVAN is unknown. Here, we generated HIV-1 transgenic mice (Tg26) with either 75% Stat3 activity (Tg26-SA/+) or 25% Stat3 activity (Tg26-SA/-). The kidneys of Tg26-SA/+ mice, but not Tg26-SA/- mice, showed increased Stat3 phosphorylation. The Tg26-SA/+ phenotype was not different from Tg26 mice, but Tg26-SA/- mice developed significantly less proteinuria, glomerulosclerosis, and tubulointerstitial injury. Tg26-SA/+ mice exhibited reduced expression of podocyte differentiation markers and increased expression of VEGF and proliferation markers as compared to Tg26-SA/- mice. Primary podocytes isolated from Tg26-SA/+ mice showed increased Stat3 phosphorylation and reduced expression of podocyte differentiation markers. The tubulointerstitial compartment and isolated tubules of Tg26-SA/+ mice also had increased Stat3 phosphorylation and expression of Stat3 target genes. We confirmed that the expression of the HIV-1 transgene and reduction of Stat3 activity did not affect T and B cell development. In conclusion, Stat3 plays a critical role in the pathogenesis of HIVAN.

Urinary NGAL marks cystic disease in HIV-associated nephropathy

Nephrosis and a rapid decline in kidney function characterize HIV-associated nephropathy (HIVAN). Histologically, HIVAN is a collapsing focal segmental glomerulosclerosis with prominent tubular damage. We explored the expression of neutrophil gelatinase-associated lipocalin (NGAL), a marker of tubular injury, to determine whether this protein has the potential to aid in the noninvasive diagnosis of HIVAN. We found that expression of urinary NGAL was much higher in patients with biopsy-proven HIVAN than in HIV-positive and HIV-negative patients with other forms of chronic kidney disease. In the HIV-transgenic mouse model of HIVAN, NGAL mRNA was abundant in dilated, microcystic segments of the nephron. In contrast, urinary NGAL did not correlate with proteinuria in human or in mouse models. These data show that marked upregulation of NGAL accompanies HIVAN and support further study of uNGAL levels in large cohorts to aid in the noninvasive diagnosis of HIVAN and screen for HIVAN-related tubular damage.

Genetic susceptibility to HIV-associated nephropathy

HIV-1-associated nephropathy (HIVAN) is a common complication of HIV-1 infection, and its skewed incidence in certain ethnic groups suggests that there is a genetic basis to HIVAN susceptibility. In their study reported in this issue of the JCI, Papeta and colleagues used a combination of gene expression profiling and linkage analysis to identify three genomic loci that regulate a network of genes expressed by podocytes - cells that are crucial to the filtration of fluid and waste by the kidney (see the related article beginning on page 1178). Surprisingly, two of these loci confer disease susceptibility in a transgenic mouse model of HIVAN. This report confirms the central role of podocytes in the pathogenesis of HIVAN and demonstrates the power of this combination of genomic analysis techniques in elucidating the pathogenesis of glomerular disease.

Susceptibility loci for murine HIV-associated nephropathy encode trans-regulators of podocyte gene expression

Multiple studies have linked podocyte gene variants to diverse sporadic nephropathies, including HIV-1-associated nephropathy (HIVAN). We previously used linkage analysis to identify a major HIVAN susceptibility locus in mouse, HIVAN1. We performed expression quantitative trait locus (eQTL) analysis of podocyte genes in HIV-1 transgenic mice to gain further insight into genetic susceptibility to HIVAN. In 2 independent crosses, we found that transcript levels of the podocyte gene nephrosis 2 homolog (Nphs2), were heritable and controlled by an ancestral cis-eQTL that conferred a 3-fold variation in expression and produced reactive changes in other podocyte genes. In addition, Nphs2 expression was controlled by 2 trans-eQTLs that localized to the nephropathy susceptibility intervals HIVAN1 and HIVAN2. Transregulation of podocyte genes was observed in the absence of HIV-1 or glomerulosclerosis, indicating that nephropathy susceptibility alleles induce latent perturbations in the podocyte expression network. Presence of the HIV-1 transgene interfered with transregulation, demonstrating effects of gene-environment interactions on disease. These data demonstrate that transcript levels of Nphs2 and related podocyte-expressed genes are networked and suggest that the genetic lesions introduced by HIVAN susceptibility alleles perturb this regulatory pathway and transcriptional responses to HIV-1, increasing susceptibility to nephropathy.

Thrombotic microangiopathy and other glomerular disorders in the HIV-infected patient

SUMMARY

Various forms of kidney disease have been related directly to human immunodeficiency virus (HIV) viral infection, including HIV-associated nephropathy (HIVAN), immune complex diseases, and thrombotic microangiopathy (TMA). HIVAN and HIV immune complex glomerulonephritides are the most common HIV-specific nephropathies. HIV-associated TMA, although far less common, remains an important consideration. The diagnosis of TMA in HIV, which has a poorly understood pathogenesis, can be suggested by thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure, but only definitively diagnosed by kidney biopsy. Not surprisingly, the incidence and prevalence of the HIV-specific entities have declined with the advent of highly active antiretroviral therapy. With this decline, however, other glomerular diseases are of increasing importance in this high-risk population. The differential diagnosis of glomerular disease in an HIV-positive patient is therefore broad. Glomerular diseases seen in this population include classic focal segmental glomerulosclerosis, IgA nephropathy, postinfectious glomerulonephritis, hepatitis B- and C-related glomerulonephritides, and membranous nephropathy. In addition, as the HIV-infected population ages, diabetic and hypertensive nephropathies are likely to become more prevalent. With overlapping presentations of these entities, definitive diagnosis often is difficult, necessitating kidney biopsy. As a consequence of establishing an accurate diagnosis, improved patient outcome can best be accomplished through disease-specific intervention.

Kidney disease in HIV-positive children

Before the era of highly active antiretroviral therapy, more than 40% of human immunodeficiency virus (HIV)-infected children experienced renal complications. In sub-Saharan Africa, approximately 2.1 million children are infected with HIV-1. In the absence of antiretroviral therapy, young African children frequently died of AIDS-related complications before renal diseases could be manifested or diagnosed. As antiretroviral therapy has become more available, and their survival has increased, our experience in treating kidney disease in HIV-infected children has improved. This article discusses relevant clinical and pathologic findings related to kidney disease in HIV-infected children.

Antiretroviral therapy improves renal function among HIV-infected Ugandans

Renal dysfunction is a severe complication of advanced HIV disease. We evaluated the impact of highly active antiretroviral therapy (HAART) on renal function among HIV-infected Ugandans in the Home-Based AIDS Care clinical trial. The patients presented with symptomatic HIV disease or CD4 cell count < or = 250 cells/mm(3) and creatinine clearances above 25 ml/min determined by the Cockcroft-Gault equation. Of the 508 patients at baseline, 8% had a serum creatinine over 133 micromol/l and about 20% had reduced renal function evidenced by a creatinine clearance between 25 and 50 ml/min. After 2 years of HAART, the median serum creatinine was significantly decreased by 16% while the median creatinine clearance significantly increased 21%. The median creatinine clearance of patients with renal dysfunction at baseline, increased by 53% during 2 years of treatment. In multivariable analysis, a baseline creatinine above 133 micromol/l, a weight gain of more than 5 kg over the 2 years, female gender and a WHO stage 4 classification were all associated with greater improvements in creatinine clearance on HAART. Our study shows that renal dysfunction was common with advanced HIV disease in Uganda but this improved following 2 years of HAART.