HIV-1 infection initiates an inflammatory cascade in human renal tubular epithelial cells

Cardiac and Renal Comorbidities in Aging People Living With HIV

Contemporary World Health Organization data indicates that ≈39 million people are living with the human immunodeficiency virus. Of these, 24 million have been reported to have successfully accessed combination antiretroviral therapy. In 1996, the World Health Organization endorsed the widespread use of combination antiretroviral therapy, transforming human immunodeficiency virus infection from being a life-threatening disease to a chronic illness characterized by multiple comorbidities. The increased access to combination antiretroviral therapy has translated to people living with human immunodeficiency virus (PLWH) no longer having a reduced life expectancy. Although aging as a biological process increases exposure to oxidative stress and subsequent systemic inflammation, this effect is likely enhanced in PLWH as they age. This narrative review engages the intricate interplay between human immunodeficiency virus associated chronic inflammation, combination antiretroviral therapy, and cardiac and renal comorbidities development in aging PLWH. We examine the evolving demographic profile of PLWH, emphasizing the increasing prevalence of aging individuals within this population. A central focus of the review discusses the pathophysiological mechanisms that underpin the heightened susceptibility of PLWH to renal and cardiac diseases as they age.

Association of HIV and viral suppression status with hospital acute kidney injury in the era of antiretroviral therapy

In the modern era, it is unknown if people that are virally suppressed with HIV (PWH) are at increased risk for acute kidney injury (AKI) compared to people without HIV and no studies have compared the risk of AKI by viral suppression status. Here, we determined the associations of HIV status and AKI among PWH with and without viral suppression compared to people without HIV. An observational cohort study of PWH and people without HIV hospitalized in a large New York City health system between 2010-2019 was conducted. Multivariable Cox proportional hazards models were used to determine associations between HIV status and risk of AKI, severe AKI and development of chronic kidney disease (CKD). Among 173,884 hospitalized patients, 4,718 had HIV; 2,532 (53.7%) were virally suppressed and 2,186 (46.3%) were not suppressed. Compared to people without HIV, PWH with and without viral suppression were at increased risk of AKI (adjusted hazard ratio 1.27, 95% confidence interval 1.15, 1.40 and 1.73, 1.58, 1.90, respectively) and AKI requiring kidney replacement therapy (1.89, 1.27, 2.84 and 1.87, 1.23, 2.84, respectively). Incremental, graded associations were observed between HIV status and Stage 2 or 3 AKI, and among AKI survivors, and incident CKD. The elevated risk of AKI across ages of PWH was similar in magnitude to older people without HIV. Thus, regardless of virologic control, HIV is an independent risk factor for AKI among hospitalized patients. Future studies should determine the mechanisms by which HIV increases susceptibility to AKI and identify strategies to prevent AKI in PWH.

NEF-Induced HIV-Associated Nephropathy Through HCK/LYN

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, we used a transgenic (Tg) mouse model (CD4C/HIV-Nef) 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. Proliferation of tubular and glomerular Tg cells is enhanced. To identify kidney cells permissive to the CD4C promoter, CD4C/green fluorescent protein reporter Tg mice 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 (p53, TRAIL, tumor necrosis factor-α, tumor necrosis factor receptor 2, and Bax), in immune cell recruitment (macrophage inflammatory protein-1α, monocyte chemoattractant protein-1, CCR-2, CCR-5, and CX3CR-1), in nitric oxide (NO) formation (endothelial NO synthase and inducible NO synthase), or in cell signaling (Fyn, Lck, and Hck/Fgr). However, deletion of Src partially and that of Hck/Lyn largely abrogated its development. Our data suggest that Nef expression in mesangial cells through Hck/Lyn represents important cellular and molecular events for the development of HIVAN in these Tg mice.

Renal impairment associated with tenofovir disoproxil fumarate for antiretroviral therapy and HIV pre-exposure prophylaxis: An observational cohort study

BACKGROUND

Tenofovir disoproxil fumarate (TDF) is associated with adverse renal outcomes when prescribed for HIV infection. There are few data concerning real-world renal outcomes amongst patients prescribed TDF for pre-exposure prophylaxis (PrEP).

METHODS AND FINDINGS

Data were extracted from 52 sexual health clinics across Australia from 2009-2019. All patients prescribed TDF-containing antiretroviral therapy and PrEP were included. Rates of renal impairment (a fall in eGFR to <60 ml/min/1·73m2) were calculated for people living with HIV (PLWHIV) prescribed TDF and HIV negative PrEP-users. Risk factors were assessed using Cox-proportional hazards models. Sensitivity analysis of risk using 1:1 propensity-score matching to adjust for potential imbalance in HIV and PrEP cohorts was conducted. 5,973 patients on PrEP and 1,973 PLWHIV were included. There were 39 (0.7%) instances of renal impairment in the PrEP group and 81 (4.1%) in the PLWHIV cohort (hazard ratio [HR]:0.35 95% confidence interval [CI]: 0.22-0.56). Rates of renal impairment were 4.01/1000 person-years (95%CI:2.93-5.48) in the PrEP cohort and 16.18/1000 person-years (95%CI:13.01-20.11) in the PLWHIV cohort (p<0.001). Predictors of renal impairment were: older age (40-49 years (HR:5.09 95%CI: 2.12-12.17) and 50-82 years (HR:13.69 95%CI: 5.92-31.67) (compared with 30-39 years) and baseline eGFR<90ml/min (HR:61.19 95%CI: 19.27-194.30). After adjusting for age and baseline eGFR the rate of renal impairment remained lower in the PrEP cohort (aHR:0.62 95%CI: 0.40-0.94, p = 0.023). In propensity-matched analysis using 1,622 patients per cohort the risk of renal impairment remained higher in the PLWHIV cohort (log-rank p = 0.001).

CONCLUSION

Patients prescribed TDF-based PrEP had lower rates of renal impairment than patients prescribed TDF for HIV infection. In propensity analysis, after matching for some risk factors, rates of renal impairment remained higher amongst patients with HIV.

Hantavirus Induced Kidney Disease

Hantavirus induced hemorrhagic fever with renal syndrome (HFRS) is an emerging viral zoonosis affecting up to 200,000 humans annually worldwide. This review article is focused on recent advances in the mechanism, epidemiology, diagnosis, and treatment of hantavirus induced HFRS. The importance of interactions between viral and host factors in the design of therapeutic strategies is discussed. Hantavirus induced HFRS is characterized by thrombocytopenia and proteinuria of varying severities. The mechanism of kidney injury appears immunopathological with characteristic deterioration of endothelial cell function and compromised barrier functions of the vasculature. Although multidisciplinary research efforts have provided insights about the loss of cellular contact in the endothelium leading to increased permeability, the details of the molecular mechanisms remain poorly understood. The epidemiology of hantavirus induced renal failure is associated with viral species and the geographical location of the natural host of the virus. The development of vaccine and antiviral therapeutics is necessary to avoid potentially severe outbreaks of this zoonotic illness in the future. The recent groundbreaking approach to the SARS-CoV-2 mRNA vaccine has revolutionized the general field of vaccinology and has provided new directions for the use of this promising platform for widespread vaccine development, including the development of hantavirus mRNA vaccine. The combinational therapies specifically targeted to inhibit hantavirus replication and vascular permeability in infected patients will likely improve the disease outcome.

Similarities and Differences between COVID-19-Associated Nephropathy and HIV-Associated Nephropathy

Kidney disease is a major complication of viral infection, which can cause both acute and chronic kidney diseases via different mechanisms such as immune-mediated injury, kidney cell injury from a direct viral infection, systemic effects, and antiviral drug-induced nephrotoxicity. HIV-associated nephropathy (HIVAN), characterized by collapsing focal segmental glomerulosclerosis (cFSGS), has been described 2 decades ago as a major complication of acquired-immunodeficiency syndrome. The pathogenesis of HIVAN has been well studied, including viral entry, host response, and genetic factors. The incidence of this disease has been dramatically dropped with current antiretroviral therapy. In the recent severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic, acute kidney injury was also found to be a major complication in patients with (coronavirus disease) COVID-19. These patients also developed glomerular disease such as cFSGS in African Americans with apolipoprotein L1 risk alleles, similar to HIVAN. Whether SARS-CoV-2 can infect kidney cells locally remains controversial, but both local infection and systemic effects are likely involved in the pathogenesis of this disease. In this review, we present a comparison of the clinical presentations, pathological findings, disease mechanisms, and potential treatments between HIVAN and COVID-19. Leveraging the knowledge in HIVAN and experimental approaches used to study HIVAN will facilitate the exploration in the pathogenesis of COVID-19-associated kidney disease and improve our management of COVID-19 patients.

Inhibition of apoptosis signal-regulating kinase 1 mitigates the pathogenesis of human immunodeficiency virus-associated nephropathy

BACKGROUND

Chronic kidney disease (CKD) is a common cause of morbidity and mortality in human immunodeficiency virus (HIV)-positive individuals. Among the HIV-related kidney diseases, HIV-associated nephropathy (HIVAN) is a rapidly progressive renal disease characterized by collapsing focal glomerulosclerosis (GS), microcystic tubular dilation, interstitial inflammation and fibrosis. Although the incidence of end-stage renal disease due to HIVAN has dramatically decreased with the widespread use of antiretroviral therapy, the prevalence of CKD continues to increase in HIV-positive individuals. Recent studies have highlighted the role of apoptosis signal-regulating kinase 1 (ASK1) in driving kidney disease progression through the activation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase and selective ASK-1 inhibitor GS-444217 was recently shown to reduce kidney injury and disease progression in various experimental models. Therefore we examined the efficacy of ASK1 antagonism by GS-444217 in the attenuation of HIVAN in Tg26 mice.

METHODS

GS-444217-supplemented rodent chow was administered in Tg26 mice at 4 weeks of age when mild GS and proteinuria were already established. After 6 weeks of treatment, the kidney function assessment and histological analyses were performed and compared between age- and gender-matched control Tg26 and GS-444217-treated Tg26 mice.

RESULTS

GS-444217 attenuated the development of GS, podocyte loss, tubular injury, interstitial inflammation and renal fibrosis in Tg26 mice. These improvements were accompanied by a marked reduction in albuminuria and improved renal function. Taken together, GS-4442217 attenuated the full spectrum of HIVAN pathology in Tg26 mice.

CONCLUSIONS

ASK1 signaling cascade is central to the development of HIVAN in Tg26 mice. Our results suggest that the select inhibition of ASK1 could be a potential adjunctive therapy for the treatment of HIVAN.

The HIV protease inhibitor darunavir prevents kidney injury via HIV-independent mechanisms

HIV-associated nephropathy (HIVAN) is a rapidly progressive kidney disease that is caused by HIV infection of renal epithelial cells with subsequent expression of viral genes, including vpr. Antiretroviral therapy ameliorates HIVAN without eradicating HIV from the kidneys and the mechanism by which it protects kidneys is poorly understood. Since HIV protease inhibitors have "off target" cellular effects, we studied whether darunavir, the most commonly prescribed protease inhibitor, protects kidneys from HIV-induced injury via mechanisms independent of HIV protease and viral replication. Renal epithelial cells were transduced with lentiviruses encoding HIV (lacking protease and reverse transcriptase), Vpr, or vector control. Darunavir attenuated HIV and Vpr-induced activation of Stat3, Src, Erk, and cytokines, which are critical for HIVAN pathogenesis. We then studied HIV-transgenic mice, which develop HIVAN in the absence of HIV protease or reverse transcriptase. Mice were treated with darunavir, zidovudine, darunavir + zidovudine, or control. Darunavir and darunavir + zidovudine reduced albuminuria and histologic kidney injury and normalized expression of dysregulated proteins. RNA-seq analyses demonstrated that darunavir suppressed HIV-induced upregulation of immune response genes in human kidney cells. These data demonstrate that darunavir protects against HIV-induced renal injury via mechanisms that are independent of inhibition of HIV protease.

The effects of add-on corticosteroids on renal outcomes in patients with biopsy proven HIV associated nephropathy: a single centre study from South Africa

BACKGROUND

The aim of this study was to assess, the efficacy and safety of add-on corticosteroids to antiretroviral therapy [ART] in patients with biopsy proven HIV associated nephropathy.

METHODS

All included patients had histological evidence of either collapsing or non-collapsing focal segmental glomerulosclerosis (FSGS) or podocyte and/or parietal cell hypertrophy or hyperplasia. All patients had evidence of tubulointerstitial inflammation with microcysts. Patients were randomized to ART with the addition of 1 mg/kg of corticosteroids [ART+C] or remained in the group [ART Alone] and followed for 2 years. A repeat biopsy was performed at 6 months.

RESULTS

Twenty-one patients were randomized to [ART+C] and 17 to [ART Alone]. The baseline estimated glomerular filtration rate (eGFR) was significantly lower in the [ART+C] vs. [ART Alone] group [35mls/min/1.73m² vs. 47 mls/min/1.73m², p = 0.015]. The [ART+C] cohort had a statistically significant improvement in median (eGFR) from baseline to last follow up compared with [ART Alone] i.e. [Δ = 25mls/min (IQR: 15;51) vs 9 mls/min (IQR: 0-24), p = 0.008]. There were no statistically significant differences between the groups when proteinuria and histology were analyzed. There were 8 deaths during the trial period, 7 from [ART+C] (Log rank p = 0.071).

CONCLUSIONS

In the [ART+C] cohort there was a significant improvement in eGFR over 2-years with increased mortality. Routine corticosteroid use cannot currently be recommended. Further investigation to define which subgroup of this cohort would safely benefit from the positive effects is required.

TRIAL REGISTRATION

ISRCTN study ID ( 56112439 ] was retrospectively registered on the 5 September 2018.

Acute kidney injury in HIV-infected patients: a critical review

Acute kidney injury (AKI) is characterized by a rapid decline of renal function associated with worse outcomes. The purpose of the authors is to perform a critical review of the incidence, risk factors, pathogenesis and outcome of AKI in HIV-infected patients. Human immunodeficiency virus (HIV)-infected patients have an increased risk of developing AKI, to which contribute both HIV-dependent and HIV-independent factors as well as the nephrotoxicity of drugs used. The increased risk of AKI in HIV-infected patients and its negative impact on prognosis highlights the need for identification of patients at risk, creation of prevention strategies and management. HIV-infected patients have an increased risk of developing AKI, to which both HIV-dependent and HIV-independent factors contribute, as well as the nephrotoxicity of drugs used. The increased risk of AKI in HIV-infected patients and its negative impact on prognosis highlight the need for identification of patients at risk, creation of prevention strategies and management.

Molecular Mechanisms of Injury in HIV-Associated Nephropathy

HIV-associated nephropathy (HIVAN) is an important cause of secondary focal glomerulosclerosis that occurs primarily in persons of African ancestry with advanced HIV disease. Although HIVAN is characterized by severe proteinuria and rapid progression to end stage renal disease without treatment, the phenotype is markedly attenuated by treatment with antiretroviral medications. HIV infection of glomerular and tubular epithelial cells and subsequent viral gene expression is a key contributor to HIVAN pathogenesis and the kidney can serve as reservoir for HIV strains that differ those in blood. HIV gene expression in renal epithelial cells leads to dysregulation of cellular pathways including cell cycle, inflammation, cell death, and cytoskeletal homeostasis. Polymorphisms in the APOL1 gene explain the marked predilection of HIVAN to occur in persons of African descent and HIVAN. Since HIVAN has the strongest association with APOL1 genotype of any of the APOL1-associated nephropathies, studies to determine the mechanisms by which HIV and APOL1 risk variants together promote kidney injury hold great promise to improve our understanding of the pathogenesis of APOL1-mediated kidney diseases.

Update on current management of chronic kidney disease in patients with HIV infection

The prevalence of HIV-associated chronic kidney disease (CKD) varies geographically and depends on the definition of CKD used, ranging from 4.7% to 38% globally. The incidence, however, has decreased with the use of effective combined antiretroviral therapy (cART). A wide variety of histological patterns are seen in HIV-associated kidney diseases that include glomerular and tubulointerstitial pathology. In resource-rich settings, there has been a plateau in the incidence of end-stage renal disease secondary to HIV-associated nephropathy (HIVAN). However, the prevalence of end-stage renal disease in HIV-positive individuals has risen, mainly due to increased longevity on cART. There is a disparity in the occurrence of HIVAN among HIV-positive individuals such that there is an 18- to 50-fold increased risk of developing kidney disease among HIV-positive individuals of African descent aged between 20 and 64 years and who have a poorer prognosis compared with their European descent counterparts, suggesting that genetic factors play a vital role. Other risk factors include male sex, low CD4 counts, and high viral load. Improvement in renal function has been observed after initiation of cART in patients with HIV-associated CKD. Treatment with an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker is recommended, when clinically indicated in patients with confirmed or suspected HIVAN or clinically significant albuminuria. Other standard management approaches for patients with CKD are recommended. These include addressing other cardiovascular risk factors (appropriate use of statins and aspirin, weight loss, cessation of smoking), avoidance of nephrotoxins, and management of serum bicarbonate and uric acid, anemia, calcium, and phosphate abnormalities. Early diagnosis of kidney disease by screening of HIV-positive individuals for the presence of kidney disease is critical for the optimal management of these patients. Screening for the presence of kidney disease upon detection of HIV infection and annually thereafter in high-risk populations is recommended.

HIV infection-induced transcriptional program in renal tubular epithelial cells activates a CXCR2-driven CD4+ T-cell chemotactic response

OBJECTIVE

Viral replication and interstitial inflammation play important roles in the pathogenesis of HIV-associated nephropathy. Cell-cell interactions between renal tubule epithelial cells (RTECs) and HIV-infected T cells can trigger efficient virus internalization and viral gene expression by RTEC. To understand how HIV replication initiates HIV-associated nephropathy, we studied the cellular response of RTECs to HIV, examining the transcriptional profiles of primary RTECs exposed to cell-free HIV or HIV-infected T cells.

METHODS

HIV-induced gene expression in hRTECs was examined in vitro by Illumina RNA deep sequencing and revealed an innate response to HIV, which was subclassified by gene ontology biological process terms. Chemokine responses were examined by CD4 T-cell chemotaxis assays.

RESULTS

As compared with cell-free virus infection, exposure to HIV-infected T cells elicited a stronger upregulation of inflammatory and immune response genes. A major category of upregulated genes are chemokine/cytokine families involved in inflammation and immune response, including inflammatory cytokines CCL20, IL6 and IL8-related chemokines: IL8, CXCL1, CXCL2, CXCL3, CXCL5 and CXCL6. Supernatants from virus-exposed RTECs contained strong chemoattractant activity on primary CD4 T cells, which was potently blocked by a CXCR2 antagonist that antagonizes IL8-related chemokines. We observed a preferential migration of CXCR2-expressing, central memory CD4 T cells in response to HIV infection of RTECs.

CONCLUSION

Interactions between primary RTECs and HIV-infected T cells result in potent induction of inflammatory response genes and release of cytokines/chemokines from RTECs that can attract additional T cells. Activation of these genes reflects an innate response to HIV by nonimmune cells.

Reversibility of Glomerular Renal Function Decline in HIV-Uninfected Men and Women Discontinuing Emtricitabine-Tenofovir Disoproxil Fumarate Pre-Exposure Prophylaxis

BACKGROUND

Tenofovir disoproxil fumarate (TDF) pre-exposure prophylaxis (PrEP) use is associated with a small but statistically significant decline in estimated glomerular filtration rate (eGFR). We investigated the reversibility of eGFR decline among HIV-uninfected adults discontinuing PrEP.

METHODS

Data were from the Partners PrEP Study, a randomized trial of daily oral TDF and emtricitabine (FTC)-TDF PrEP among African HIV-uninfected men and women with baseline creatinine clearance ≥60 mL/min. Serum creatinine was measured quarterly while on-study medication and at month 1 and 2 after discontinuation. eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration Equation.

RESULTS

A total of 3924 individuals had a poststudy drug serum creatinine measurement after the scheduled drug discontinuation (1271 for TDF, 1308 for FTC-TDF, and 1345 for placebo); 65% were men, median age was 35 (range 18-64) years. Median time on study drug was 33 (interquartile range 25-36) months overall, and 36 months (interquartile range 30-36) for TDF and FTC-TDF. Mean eGFR at the last on-treatment visit was 129 mL·min·1.73 m for TDF and 128 mL·min·1.73 m for FTC-TDF versus 131 mL·min·1.73 m for placebo (2-3 mL·min·1.73 m mean decline for PrEP versus placebo, P ≤ 0.01), and this difference reversed by 4 weeks after drug discontinuation (mean eGFR at the first postdrug visit: 130 mL·min 1.73 m in all groups). More than 96% of participants had a confirmed >75% eGFR rebound to baseline level by 8 weeks after drug discontinuation, with similar proportions across treatment groups.

CONCLUSIONS

In this large, placebo-controlled study of TDF-based PrEP, the small reduction in mean eGFR associated with PrEP reversed within weeks after discontinuation.

HIV and chronic kidney disease

Chronic kidney disease (CKD) is a frequent complication of HIV infection, occurring in 3.5 - 48.5%, and occurs as a complication of HIV infection, other co-morbid disease and infections and as a consequence of therapy of HIV infection and its complications. The classic involvement of the kidney by HIV infection is HIV-associated nephropathy (HIVAN), occurring typically in young adults of African ancestry with advanced HIV disease in association with APOL1 high-risk variants. HIV-immune complex disease is the second most common diagnosis obtained from biopsies of patients with HIV-CKD. CKD is mediated by factors related to the virus, host genetic predisposition and environmental factors. The host response to HIV infection may influence disease phenotype through activation of cytokine pathways. With the introduction of antiretroviral therapy (ART), there has been a decline in the incidence of HIVAN, with an increasing prevalence of focal segmental glomerulosclerosis. Several studies have demonstrated the overall improvement in kidney function when initiating ART for HIV CKD. Progression to end stage kidney disease has been reported to be more likely when high grade proteinuria, severely reduced eGFR, hepatitis B and/C co-infection, diabetes mellitus, extensive glomerulosclerosis, and chronic interstitial fibrosis are present. Improved renal survival is associated with use of renin angiotensin system blockers and viral suppression. Many antiretroviral medications are partially or completely eliminated by the kidney and require dose adjustment in CKD. Certain drug classes, such as the protease inhibitors and the non-nucleoside reverse transcriptase inhibitors, are metabolized by the liver and do not require dose adjustment. HIV-infected patients requiring either hemo- or peritoneal dialysis, who are stable on ART, are achieving survival rates comparable to those of dialysis patients without HIV infection. Kidney transplantation has been performed successfully in HIV-infected patients; graft and patient survival appears to be similar to that of HIV-uninfected recipients. Early detection of kidney disease by implementation of screening on diagnosis of HIV infection and annual screening thereafter will have an impact on the burden of disease, together with access to ART to those who require it. Programs for prevention of HIV infection are essential to prevent this lethal 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.

Kidney Dysfunction and Markers of Inflammation in the Multicenter AIDS Cohort Study

BACKGROUND

Human immunodeficiency virus (HIV)-infected individuals are at higher risk for chronic kidney disease than HIV-uninfected individuals. We investigated whether the inflammation present in treated HIV infection contributes to kidney dysfunction among HIV-infected men receiving highly active antiretroviral therapy.

METHODS

The glomerular filtration rate (GFR) was directly measured (using iohexol) along with 12 markers of inflammation in Multicenter AIDS Cohort Study participants. Exploratory factor analysis was used to identify inflammatory processes related to kidney dysfunction. The estimated levels of these inflammatory processes were used in adjusted logistic regression analyses evaluating cross-sectional associations with kidney function outcomes.

RESULTS

There were 434 HIV-infected men receiving highly active antiretroviral therapy and 200 HIV-uninfected men. HIV-infected men were younger (median age, 51 vs 53 years) and had higher urine protein-creatinine ratios (median, 98 vs 66 mg/g) but comparable GFRs (median, 109 vs 106 mL/min|1.73 m(2)). We found an inflammatory process dominated by markers: soluble tumor necrosis factor receptor 2, soluble interleukin 2 receptor α, soluble gp130, soluble CD27, and soluble CD14. An increase of 1 standard deviation in that inflammatory process was associated with significantly greater odds of GFR ≤90 mL/min/1.73 m(2) (odds ratio, 2.0) and urine protein >200 mg/g (odds ratio, 2.3).

CONCLUSIONS

Higher circulating levels of immune activation markers among treated HIV-infected men may partially explain their higher burden of kidney dysfunction compared with uninfected men.

Renal epithelial cells produce and spread HIV-1 via T-cell contact

OBJECTIVES

Increasing evidence supports the role of the kidney as a reservoir for HIV-1. In-vitro co-cultivation of HIV-infected T cells with renal tubule epithelial (RTE) cells results in virus transfer to the latter, whereas cell-free virus infection is inefficient. We further characterized the fate of HIV-1 after it is internalized in renal epithelial cells.

METHODS

Primary or immortalized CD4 cells were infected with a green fluorescent protein (GFP)-expressing replication competent HIV-1. HIV-1 transfer from T cells to RTE cells was carried out in a co-culture system and evaluated by fluorescence-activated cell sorting analysis. HIV-1 integration in renal cells was evaluated by Alu-PCR and the production of infectious particles was assessed by p24-ELISA and TZM-bl assay. HIV-infected renal cells were used as donor cells in a co-culture system to evaluate their ability to transfer the virus back to T cells.

RESULTS

Renal cells become productively infected by HIV-1 and multiple copies of HIV-1 can be transferred from infected T cells to renal cells. Two separate cell populations were identified among infected renal cells based on reporter gene GFP expression level (low vs. high), only the high showing sensitivity to azidothymidine and ritonavir. Co-cultivation of HIV-1-infected renal cells with noninfected T cells resulted in HIV-1 transmission to T cells, supporting bidirectional exchange of virus between T cells and kidney-derived cells. Persistent expression and generation of infectious virus in renal cells required HIV integration.

CONCLUSION

These results support the kidney as a potential reservoir where virus is exchanged between interstitial T cells and RTE cells.

Baseline Renal Function among Antiretroviral Therapy-Naive, HIV-Infected Patients in Southeast Nigeria

Background:

Renal insufficiency has been shown to be a significant, independent risk factor for mortality among HIV-infected patients. Unfortunately, little is known about the prevalence and nature of renal impairment in African populations initiating antiretroviral treatment. This study aims to find the prevalence of abnormal renal function among antiretroviral therapy (ART)-naive, HIV-infected patients in the South Eastern geopolitical zone of Nigeria.

Method:

This is a cross-sectional hospital-based study, involving 300 ART-naive HIV-positive patients, seen over a 1-year period, aged from 18 years and older, presenting to the clinic for the first time.

Results:

A total of 300 patients were included in the study, 104 (34.7%) males and 196 (65.3%) females. The prevalence of significant renal disease was 24.3% (73 of 300), while 38.3% (115 of 300) had mild renal impairment. Using logistic regression, age, CD4 count, urea, creatinine, and hemoglobin were significantly associated with renal impairment.

Conclusion:

The authors observed a high prevalence of significant renal impairment among HIV-infected patients at the time of ART initiation.

Advances in the pathogenesis of HIV-associated kidney diseases

Despite improved outcomes among persons living with HIV who are treated with antiretroviral therapy, they remain at increased risk for acute and chronic kidney diseases. Moreover, since HIV can infect renal epithelial cells, the kidney might serve as a viral reservoir that would need to be eradicated when attempting to achieve full virologic cure. In recent years, much progress has been made in elucidating the mechanism by which HIV infects renal epithelial cells and the viral and host factors that promote development of kidney disease. Polymorphisms in APOL1 confer markedly increased risk of HIV-associated nephropathy; however, the mechanism by which ApoL1 variants may promote kidney disease remains unclear. HIV-positive persons are at increased risk of acute kidney injury, which may be a result of a high burden of subclinical kidney disease and/or viral factors and frequent exposure to nephrotoxins. Despite the beneficial effect of antiretroviral therapy in preventing and treating HIVAN, and possibly other forms of kidney disease in persons living with HIV, some of these medications, including tenofovir, indinavir, and atazanavir can induce acute and/or chronic kidney injury via mitochondrial toxicity or intratubular crystallization. Further research is needed to better understand factors that contribute to acute and chronic kidney injury in HIV-positive patients and to develop more effective strategies to prevent and treat kidney disease in this vulnerable population.

Baseline Renal Function among Antiretroviral Therapy-Naive, HIV-Infected Patients in South East Nigeria

Background:Renal insufficiency has been shown to be a significant, independent risk factor for mortality among HIV-infected patients. Unfortunately, little is known about the prevalence and nature of renal impairment in African populations initiating antiretroviral treatment. This study aims to find the prevalence of abnormal renal function among antiretroviral therapy (ART)-naive, HIV-infected patients in the South Eastern geopolitical zone of Nigeria.Method:This is a cross-sectional hospital-based study, involving 300 ART-naive HIV-positive patients, seen over a 1-year period, aged from 18 years and older, presenting to the clinic for the first time.Results:A total of 300 patients were included in the study, 104 (34.7%) males and 196 (65.3%) females. The prevalence of significant renal disease was 24.3% (73 of 300), while 38.3% (115 of 300) had mild renal impairment. Using logistic regression, age, CD4 count, urea, creatinine, and hemoglobin were significantly associated with renal impairment.Conclusion:The authors observed a high prevalence of significant renal impairment among HIV-infected patients at the time of ART initiation.

Gardiquimod: a Toll-like receptor-7 agonist that inhibits HIV type 1 infection of human macrophages and activated T cells

Immune response modifiers are being studied as therapeutic agents for viral infections and cancer. These molecules include agonists for the Toll-like receptors (TLR), a family of innate immune receptors. TLR7 and 8, located in cellular endosomes, bind single-stranded RNA characteristic of viral genomes, and trigger intracellular signaling pathways that induce inflammatory cytokines and antiviral innate immune factors. We studied the anti-HIV-1 effects of gardiquimod, a specific TLR7 agonist when used at concentrations below 10 μM, in macrophages and activated peripheral blood mononuclear cells (PBMCs). Gardiquimod, added prior to or within 2 days after infection with X4, R5, or dual-tropic (R5/X4) strains of HIV-1, significantly reduced infection in these cells. Cocultures of activated PBMCs added to gardiquimod-treated and HIV-1-exposed macrophages demonstrated minimal HIV-1 replication for up to 10 days, suggesting that gardiquimod inhibited activated PBMCs viral amplification from HIV-1-exposed macrophages. Gardiquimod treatment of both activated PBMCs and macrophages induced interferon-alpha (IFN-α) transcription within hours of addition, and sustained IFN-α protein secretion for several days. Treatment of cells with a peptide inhibitor to the MyD88 adaptor protein blocked the induction of IFN-α by gardiquimod, and partially reversed the anti-HIV effects in activated PBMCs. Blocking the IFN-α receptor with a neutralizing antibody also reduced the anti-HIV effect of gardiquimod. Gardiquimod inhibited HIV-1 reverse transcriptase, an early step in the life cycle of HIV-1. These findings suggest that gardiquimod, functioning as both an immune system modifier and a reverse transcriptase inhibitor, could be developed as a novel therapeutic agent to block systemic and mucosal transmission of HIV-1.

Deletion of podocyte STAT3 mitigates the entire spectrum of HIV-1-associated nephropathy

OBJECTIVE

HIV-1 gene expression in kidney epithelial cells is thought to be responsible for the pathogenesis of HIV-1-associated nephropathy (HIVAN). Signal transducer and activator of transcription (STAT) 3 signaling is activated in podocytes of patients with HIVAN and drives the dedifferentiation and proliferation of podocytes in culture. We confirm here that deletion of podocyte STAT3 is sufficient to mitigate the glomerular as well as tubulointerstitial findings of HIVAN.

METHODS

To demonstrate the functional role of podocyte STAT3 in the pathogenesis of HIVAN we compared the development of HIVAN in Tg26 HIV-transgenic mice with and without deletion of STAT3 in the podocyte.

RESULTS

Tg26 mice with podocyte-specific STAT3 deletion developed significantly less weight loss, albuminuria, and renal function impairment compared to Tg26 mice without STAT3 deletion. Tg26 mice with podocyte STAT3 deletion also had significantly less glomerular collapse, sclerosis, epithelial cell hyperplasia, podocyte dedifferentiation, and proinflammatory STAT3 target gene expression; and tubulointerstitial changes of HIVAN, including tubular atrophy, degeneration, apoptosis, and lymphocyte infiltration, were also significantly reduced compared to Tg26 mice without STAT3 deletion.

CONCLUSION

Development of glomerular as well as tubulointerstitial injuries in the Tg26 HIVAN model is dependent on podocyte STAT3 expression. Inhibition of STAT3 could be a potential adjunctive therapy for the treatment of HIVAN.

Renoprotective effect of combined inhibition of angiotensin-converting enzyme and histone deacetylase

The Connectivity Map database contains microarray signatures of gene expression derived from approximately 6000 experiments that examined the effects of approximately 1300 single drugs on several human cancer cell lines. We used these data to prioritize pairs of drugs expected to reverse the changes in gene expression observed in the kidneys of a mouse model of HIV-associated nephropathy (Tg26 mice). We predicted that the combination of an angiotensin-converting enzyme (ACE) inhibitor and a histone deacetylase inhibitor would maximally reverse the disease-associated expression of genes in the kidneys of these mice. Testing the combination of these inhibitors in Tg26 mice revealed an additive renoprotective effect, as suggested by reduction of proteinuria, improvement of renal function, and attenuation of kidney injury. Furthermore, we observed the predicted treatment-associated changes in the expression of selected genes and pathway components. In summary, these data suggest that the combination of an ACE inhibitor and a histone deacetylase inhibitor could have therapeutic potential for various kidney diseases. In addition, this study provides proof-of-concept that drug-induced expression signatures have potential use in predicting the effects of combination drug therapy.

Low-level HIV viremia is associated with microbial translocation and inflammation

BACKGROUND

Decrease in HIV viral load (VL) is accompanied by decrease in microbial translocation (MT) and chronic inflammation, but the behavior of these markers in patients with HIV-VL <20 copies per milliliter is unknown. The aim of this study was to determine whether strict control of HIV-VL is associated with MT and chronic inflammation.

METHODS

Observational cross-sectional study.

INCLUSION CRITERIA

HIV patients receiving antiretroviral therapy and HIV-VL <200 copies per milliliter for more than 6 months.

EXCLUSION CRITERIA

chronic liver disease, active infection, or antibiotic consumption. Recruitment: patients who consecutively visited the outpatient clinic in November 2011. Primary endpoint: molecular MT as determined by detection in plasma of 16S ribosomal DNA. Secondary variables: lipopolysaccharide, soluble CD14, tumor necrosis factor α, and interleukin 6. Primary explanatory variable: HIV-VL (COBAS AmpliPrep/COBAS TaqMan HIV-1 test, version 2.0) with a detection limit of 20 copies per milliliter.

RESULTS

Fifty-two patients were included: 65% men, median age 45 years, HIV acquired predominantly through sex (75%), 40% Centers for Disease Control and Prevention stage C, and median CD4 lymphocyte count 552 cells per cubic millimeter (range, 126-1640 cells/mm). Molecular MT was observed in 46% and 18% of patients with low-level (20-200 copies/mL) and negative (<20 copies/mL) HIV-VL, respectively (P < 0.05). Plasma levels of inflammatory markers (tumor necrosis factor α and interleukin 6) were higher in patients with molecular MT (P < 0.01) and were not influenced for HIV-VL.

CONCLUSIONS

Patients with HIV infection receiving treatment and negative HIV-VL (<20 copies/mL) present less frequently MT than patients with low-level HIV viremias (20-200 copies/mL). MT is associated with higher levels of inflammation markers, independent of HIV-VL.

A parallel genome-wide mRNA and microRNA profiling of the frontal cortex of HIV patients with and without HIV-associated dementia shows the role of axon guidance and downstream pathways in HIV-mediated neurodegeneration

BACKGROUND

HIV-associated dementia (HAD) is the most common dementia type in young adults less than 40 years of age. Although the neurotoxins, oxidative/metabolic stress and impaired activity of neurotrophic factors are believed to be underlying reasons for the development of HAD, the genomic basis, which ultimately defines the virus-host interaction and leads to neurologic manifestation of HIV disease is lacking. Therefore, identifying HIV fingerprints on the host gene machinery and its regulation by microRNA holds a great promise and potential for improving our understanding of HAD pathogenesis, its diagnosis and therapy.

RESULTS

A parallel profiling of mRNA and miRNA of the frontal cortex autopsies from HIV positive patients with and without dementia was performed using Illumina Human-6 BeadChip and Affymetrix version 1.0 miRNA array, respectively. The gene ontology and pathway analysis of the two data sets showed high concordance between miRNA and mRNAs, revealing significant interference with the host axon guidance and its downstream signalling pathways in HAD brains. Moreover, the differentially expressed (DE) miRNAs identified in this study, in particular miR-137, 153 and 218, based on which most correlations were built cumulatively targeted neurodegeneration related pathways, implying their future potential in diagnosis, prognosis and possible therapies for HIV-mediated and possibly other neurodegenerative diseases. Furthermore, this relationship between DE miRNAs and DE mRNAs was also reflected in correlation analysis using Bayesian networks by splitting-averaging strategy (SA-BNs), which revealed 195 statistically significant correlated miRNA-mRNA pairs according to Pearson's correlation test (P<0.05).

CONCLUSIONS

Our study provides the first evidence on unambiguous support for intrinsic functional relationship between mRNA and miRNA in the context of HIV-mediated neurodegeneration, which shows that neurologic manifestation in HIV patients possibly occurs through the interference with the host axon guidance and its downstream signalling pathways. These data provide an excellent avenue for the development of new generation of diagnostic/prognostic biomarkers and therapeutic intervention strategies for HIV-associated neurodegeneration.

Soluble mediators of inflammation in HIV and their implications for therapeutics and vaccine development

From early in the HIV epidemic it was appreciated that many inflammatory markers such as neopterin and TNF-α were elevated in patients with AIDS. With the advent of modern technology able to measure a broad array of cytokines, we now know that from the earliest points of infection HIV induces a cytokine storm. This review will focus on how cytokines are disturbed in HIV infection and will explore potential therapeutic uses of cytokines. These factors can be used directly as therapy during HIV infection, either to suppress viral replication or prevent deleterious immune effects of infection, such as CD4+ T cell depletion. Cytokines also show great promise as adjuvants in the development of HIV vaccines, which would be critical for the eventual control of the epidemic.

Caveolin-1 suppresses human immunodeficiency virus-1 replication by inhibiting acetylation of NF-κB

Caveolin-1 is an integral membrane protein primarily responsible for the formation of membrane structures known as caveolae. Caveolae are specialized lipid rafts involved in protein trafficking, cholesterol homeostasis, and a number of signaling functions. It has been demonstrated that caveolin-1 suppresses HIV-1 protein expression. We found that co-transfecting cells with HIV-1 and caveolin-1 constructs, results in a marked decrease in the level of HIV-1 transcription relative to cells transfected with HIV-1 DNA alone. Correspondingly, reduction of endogenous caveolin-1 expression by siRNA-mediated silencing resulted in an enhancement of HIV-1 replication. Further, we observed a loss of caveolin-mediated suppression of HIV-1 transcription in promoter studies with reporters containing mutations in the NF-κB binding site. Our analysis of the posttranslational modification status of the p65 subunit of NF-κB demonstrates hypoacetylation of p65 in the presence of caveolin-1. Since hypoacetylated p65 has been shown to inhibit transcription, we conclude that caveolin-1 inhibits HIV-1 transcription through a NF-κB-dependent mechanism.

Chronic kidney disease associated with perinatal HIV infection in children and adolescents

BACKGROUND

This study describes the incidence, clinical and demographic characteristics, and spectrum of chronic kidney disease (CKD) in youths with perinatal HIV-1 infection.

METHODS

Retrospective analysis between May 1993 and December 2006 of subjects with renal disease followed in the Pediatric AIDS Clinical Trials Group 219/219C multicenter study examining the long-term consequences of perinatal HIV infection. Diagnosis confirmation was made utilizing a questionnaire mailed to research sites. Participants with CKD of other etiology than HIV were excluded. Outcome measures were biopsy-diagnosed CKD and, in the absence of biopsy, HIV-associated nephropathy (HIVAN) using established clinical criteria.

RESULTS

Questionnaires on 191 out of 2,102 participants identified 27 cases of CKD: 14 biopsy-diagnosed and 6 clinical cases of HIVAN, and 7 biopsy-diagnosed cases of immune complex-mediated kidney disease (lupus-like nephritis, 3; IgA nephropathy, 2; membranous nephropathy, 2). Incidence rates for CKD associated with HIV in pre-highly active antiretroviral therapy (HAART) (1993-1997) and HAART (1998-2002, 2003-2006) eras were 0.43, 2.84, and 2.79 events per 1,000 person years respectively. In multivariate analysis, black race and viral load ≥100,000 copies/mL (rate ratios 3.28 and 5.05, p ≤ 0.02) were associated with CKD.

CONCLUSIONS

A variety of immune complex-mediated glomerulonephritides and HIVAN occurs in this population. Black race and uncontrolled viral replication are risk factors for CKD associated with HIV.

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.

Kruppel-like factor 15 (KLF15) is a key regulator of podocyte differentiation

Podocyte injury resulting from a loss of differentiation is the hallmark of many glomerular diseases. We previously showed that retinoic acid (RA) induces podocyte differentiation via stimulation of the cAMP pathway. However, many podocyte maturity markers lack binding sites for RA-response element or cAMP-response element (CREB) in their promoter regions. We hypothesized that transcription factors induced by RA and downstream of CREB mediate podocyte differentiation. We performed microarray gene expression studies in human podocytes treated with and without RA to identify differentially regulated genes. In comparison with known CREB target genes, we identified Krüppel-like factor 15 (KLF15), a kidney-enriched nuclear transcription factor, that has been previously shown to mediate cell differentiation. We confirmed that RA increased KLF15 expression in both murine and human podocytes. Overexpression of KLF15 stimulated expression of differentiation markers in both wild-type and HIV-1-infected podocytes. Also, KLF15 binding to the promoter regions of nephrin and podocin was increased in RA-treated podocytes. Although KLF15(-/-) mice at base line had minimal phenotype, lipopolysaccharide- or adriamycin-treated KLF15(-/-) mice had a significant increase in proteinuria and podocyte foot process effacement with a reduction in the expression of podocyte differentiation markers as compared with the wild-type treated mice. Finally, KLF15 expression was reduced in glomeruli isolated from HIV transgenic mice as well as in kidney biopsies from patients with HIV-associated nephropathy and idiopathic focal segmental glomerulosclerosis. These results indicate a critical role of KLF15 in mediating podocyte differentiation and in protecting podocytes against injury.

The New Epidemiology of HIV-Related Kidney Disease

HIV-related kidney disease has been associated with significant morbidity and mortality in the HIV population. It is clear that the epidemiology of HIV-related kidney disease has changed dramatically since the first case reports in 1984. During these early years, the predominant etiology of kidney disease in HIV was recognized as HIV-associated nephropathy (HIVAN), an aggressive form of kidney disease with a high rate of progression to end-stage renal disease (ESRD). Subsequently, with the widespread use of combination antiretroviral therapy (cART), there was a dramatic decrease in the incidence of ESRD attributed to HIV/AIDS. Although the incidence of HIV-related ESRD has plateaued in the last 15 years, the prevalence has continued to increase because of improved survival. Available prevalence estimates do not include HIV-infected individuals with comorbid ESRD, although there is growing evidence that the epidemiology of kidney disease in the HIV-infected population has changed. This article reviews the impact of risk factors such as race, diabetes mellitus, hypertension, hepatitis C virus coinfection, and the chronic use of cART on the changing epidemiology of HIV-related kidney disease. Additionally in this review, we propose potential areas of translational research that will help to further characterize HIV-related kidney disease in the 21^st century.

The spectrum of renal histologies seen in HIV with outcomes, prognostic indicators and clinical correlations

BACKGROUND

Two hundred and twenty-one HIV-positive renal biopsies were analysed from Groote Schuur Hospital to determine outcomes and prognostic indicators based on histology and clinical features.

METHODS

The histology findings were compared with patient demographics, clinical and renal parameters, mortality, CD4 count and date of commencing combined anti-retroviral therapy (cART). Follow-up was between 1 and 3.5 years.

RESULTS

We found a spectrum of renal histologies in HIV-positive patients of which HIV-associated nephropathy (HIVAN) was the most common histology. cART reduced the mortality in those with any feature of HIVAN by 57% [adjusted hazard ratio (AHR) 0.43, 95% confidence interval (CI) 0.22-0.85]. Of those patients with HIVAN who died, 79% died of renal failure as registered on their death certificate. Proteinuria and microcysts were shown to be poor prognostic indicators (AHR 1.36: 1.09-1.70 and 2.04: 1.24-3.37). In patients with HIVAN alone followed for up to 2 years on cART, estimated glomerular filtration rate remained stable and there was a trend towards decreased proteinuria. cART improved survival in patients with isolated immune complex disease.

CONCLUSIONS

As mortality is improved in patients with any feature of HIVAN or isolated immune complex disease, cART should be initiated once any of these histological features are established. We believe the spectrum of disease that constitutes HIVAN needs to be more specifically defined. The ultimate outcome may be determined by the histological subtype.

Recent progress in HIV-associated nephropathy

The classic kidney disease of HIV infection, HIV-associated nephropathy (HIVAN), is an aggressive form of collapsing focal segmental glomerulosclerosis with accompanying tubular and interstitial lesions. HIVAN was first described among African-Americans and Haitian immigrants with advanced HIV disease, an early suggestion of a strong genetic association. This genetic susceptibility was recently linked to polymorphisms on chromosome 22 in individuals of African descent. The association with advanced HIV infection and evidence from HIV-transgenic mice suggested the possibility that HIV directly infects the kidney and that specific HIV gene expression induces host cellular pathways that are responsible for HIVAN pathogenesis. Although combination antiretroviral therapy has substantially reduced the impact of HIVAN in the United States, continued growth of the HIV epidemic in susceptible African populations may have important public health implications. This article reviews recent progress in the pathogenesis and treatment of HIVAN and describes the changing epidemiology of HIV-related kidney disease.

HIV-associated nephropathy: pathogenesis

PURPOSE OF REVIEW

HIV-associated nephropathy (HIVAN) is characterized histologically by a collapsing form of focal segmental glomerulosclerosis (FSGS), microcystic tubular dilation, interstitial inflammation and fibrosis. In this review, we provide a summary of the current state of knowledge about the mechanisms involved in the pathogenesis of HIVAN.

RECENT FINDINGS

Two variants in the ApoL1 gene have been identified as the susceptibility alleles that account for a majority of the increased risk of FSGS and nondiabetic end-stage renal disease in blacks. HIVAN1 and HIVAN2 are the other host susceptibility genes that have been identified in animal models for HIVAN. HIV infects renal tubular epithelial cells likely through direct cell-cell transmission. Both in-vivo and in-vitro evidence suggests that Nef and Vpr are the key viral genes mediating HIVAN. Nef induces podocyte dysfunction, whereas Vpr induces renal tubular epithelial cell apoptosis.

SUMMARY

HIVAN results from direct infection by HIV-1 and expression of viral genes, especially Nef and Vpr, in renal epithelial cells in a genetically susceptible host. The infected renal epithelium acts as a separate viral compartment from the blood and facilitates evolution of strains distant from blood. Dysregulation of several host cellular pathways, including those involved in cell cycle and apoptosis, ultimately results in the unique histopathological syndrome of HIVAN.

Renal HIV expression is unaffected by serum LPS levels in an HIV transgenic mouse model of LPS induced kidney injury

Acute kidney injury (AKI) is associated with increased rates of mortality. For unknown reasons, HIV infected individuals have a higher risk of AKI than uninfected persons. We tested our hypothesis that increased circulating LPS increases renal expression of HIV and that HIV transgenic (Tg26) mice have increased susceptibility to AKI. Tg26 mice harbor an HIV transgene encoding all HIV genes except gag and pol, and develop a phenotype analogous to HIVAN. Mice were used at 4-6 weeks of age before the onset of gross renal disease. Mice were injected i.p. with LPS or sterile saline. Renal function, tubular injury, cytokine expression, and HIV transcription were evaluated in Tg26 and wild type (WT) mice. LPS injection induced a median 60.1-fold increase in HIV expression in spleen but no change in kidney. There was no significant difference in renal function, cytokine expression, or tubular injury scores at baseline or 24 hours after LPS injection. HIV transcription was also analyzed in vitro using a human renal tubular epithelial cell (RTEC) line. HIV transcription increased minimally in human RTEC, by 1.47 fold, 48 hours after LPS exposure. We conclude that Tg26 mice do not increase HIV expression or have increased susceptibility to LPS induced AKI. The increased risk of AKI in HIV infected patients is not mediated via increased renal expression of HIV in the setting of sepsis. Moreover, renal regulation of HIV transcription is different to that in the spleen.

Virological synapses allow HIV-1 uptake and gene expression in renal tubular epithelial cells

In animal models of HIV-associated nephropathy, the expression of HIV regulatory genes in epithelial cells is sufficient to cause disease, but how the CD4-negative epithelial cells come to express HIV genes is unknown. Here, we co-cultured T cells infected with fluorescently tagged HIV with renal tubular epithelial cells and observed efficient virus transfer between these cells. The quantity of HIV transferred was much greater than that achieved by exposure to large amounts of cell-free virus and occurred without a requirement for CD4 or Env. The transfer required stable cell-cell adhesion, which could be blocked by sulfated polysaccharides or poly-anionic compounds. We found that the internalization of virus could lead to de novo synthesis of viral protein from incoming viral RNAs even in the presence of a reverse transcriptase inhibitor. These results illustrate an interaction between infected T cells and nonimmune cells, supporting the presence of virological synapses between HIV-harboring T cells and renal tubular epithelial cells, allowing viral uptake and gene expression in epithelial cells.

HIV and the Kidney

Direct effects of HIV-1 infection on the kidney combine with immune and genetic factors, comorbidities, coinfections, and medication toxicities to induce a spectrum of kidney disorders in HIV disease. The most dramatic of these, HIV-associated nephropathy (HIVAN), emerges almost exclusively in persons of African descent and is associated with rapid progression to end-stage renal disease in the absence of antiretroviral therapy (ART). ART modifies the natural history of HIVAN, but the renal benefits of ART may not be limited to HIVAN. ART is often under prescribed or incorrectly dosed in persons with kidney disease. Vigilant attention to renal function and an understanding of the complex associations involving the kidneys are necessary for optimal care of these patients.

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.

The pathogenesis of HIV-associated nephropathy

HIV-associated nephropathy (HIVAN) is one of the leading causes of ESRD in HIV-1-seropositive patients. Patients typically present with heavy proteinuria and chronic renal failure with pathologic findings of collapsing focal segmental glomerulosclerosis (FSGS). The disease is caused by direct infection of renal epithelial cells by HIV-1 in a genetically susceptible host. The genetic factors responsible for the susceptibility to HIVAN among blacks include a noncoding variant in the podocyte-expressed gene nonmuscle myosin, heavy chain 9 (MYH9) as well as other genes yet to be identified. Podocyte and tubular dysfunction results from the expression of viral genes, in particular nef and vpr, and the subsequent dysregulation of numerous host factors, including critical signaling pathways, inflammatory mediators, and others. The identification of these factors has the potential to provide novel therapeutic targets to prevent and treat this important disease.

Massive induction of innate immune response to Candida albicans in the kidney in a murine intravenous challenge model

In the experimental Candida albicans intravenous challenge model, the kidney is one of the main organs involved in disease. In progressive infection, fungal burdens are found to increase over time, with rapid increases occurring from 24 h postinfection. Renal transcriptional responses were analyzed at this time in the kidneys of mice infected by either a virulent or an attenuated C. albicans strain, allowing comparison of host responses in progressive and nonprogressive infection. The results of this study demonstrate that both infections share a common transcriptional response, consisting of functions associated with the acute-phase reaction. In addition, challenge with the virulent strain led to a massively increased expression of cytokine genes, other innate response genes and genes suggestive of initiation of the adaptive immune response. This immune response to C. albicans infection, which occurs only in progressive infection, may contribute to development of sepsis and, ultimately, host death.

The ubiquitin-like protein FAT10 mediates NF-kappaB activation

NF-kappaB is a central mediator of innate immunity and contributes to the pathogenesis of several renal diseases. FAT10 is a TNF-alpha-inducible ubiquitin-like protein with a putative role in immune response, but whether FAT10 participates in TNF-alpha-induced NF-kappaB activation is unknown. Here, using renal tubular epithelial cells (RTECs) derived from FAT10(-/-) and FAT10(+/+) mice, we observed that FAT10 deficiency abrogated TNF-alpha-induced NF-kappaB activation and reduced the induction of NF-kappaB-regulated genes. Despite normal IkBalpha degradation and polyubiquitination, FAT10 deficiency impaired TNF-alpha-induced IkBalpha degradation and nuclear translocation of p65 in RTECs, suggesting defective proteasomal degradation of polyubiquitinated IkBalpha. In addition, FAT10 deficiency reduced the expression of the proteasomal subunit low molecular mass polypeptide 2 (LMP2). Transduction of FAT10(-/-) RTECs with FAT10 restored LMP2 expression, TNF-alpha-induced IkBalpha degradation, p65 nuclear translocation, and NF-kappaB activation. Furthermore, LMP2 transfection restored IkBalpha degradation in FAT10(-/-) RTECs. In humans, common types of chronic kidney disease associated with tubulointerstitial upregulation of FAT10. These data suggest that FAT10 mediates NF-kappaB activation and may promote tubulointerstitial inflammation in chronic kidney diseases.

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.

Proteinuria, creatinine clearance, and immune activation in antiretroviral-naive HIV-infected subjects

Because both renal disease and immune activation predict progression to acquired immunodeficiency syndrome (AIDS), we evaluated the associations between proteinuria>or=1+, as determined by dipstick analysis (7 [7%] of 1012 subjects); creatinine clearance of <90 mL/min (195 [18%] of 1071 subjects); and percentages of peripheral activated CD8 cells (CD8+CD38+HLA-DR+ cells) in antiretroviral-naive, human immunodeficiency virus (HIV)-infected subjects who were enrolled in AIDS Clinical Trials Group studies 384 and A5095. Proteinuria, but not creatinine clearance, was associated with higher percentages of CD8+CD38+HLA-DR+ cells (55% vs. 50%; P=.01), with even more pronounced differences noted among men and among blacks and Hispanics. Proteinuria may be a surrogate measurement of greater immune activation in HIV-infected patients initiating antiretroviral therapy.

A urinary biomarker profile for children with HIV-associated renal diseases

Human immunodeficiency virus (HIV)-infected children are at risk of developing several types of renal diseases, including HIV-associated nephropathy (HIVAN), which is usually seen during late stages of infection in children with a high viral load. This disease is defined by the presence of proteinuria associated with mesangial hyperplasia and/or global-focal segmental glomerulosclerosis combined with microcystic transformation of the renal tubules. Because HIVAN can have an insidious clinical onset, renal biopsy is the only definitive way of establishing a diagnosis. Given the risk of performing this procedure in HIV-infected children with other AIDS-defining illness, we sought to identify informative biomarkers such as growth factors in the urine of 55 HIV-infected children that might be predictive of the extent and activity of the renal lesions characteristic of HIVAN. We found that the levels of epidermal growth factor were lower in the urine of children with renal disease, whereas levels of fibroblast growth factor-2 and metalloproteinase-2 were higher as compared with those levels in infected children without renal disease. Similar changes were observed in HIV-Tg26 mice correlating with the progression of renal disease in this model of HIVAN. Our findings suggest that this urinary growth factor profile may be useful in facilitating the diagnosis of HIV-infected children at risk of developing HIVAN when interpreted in the appropriate clinical setting.

Pathogenesis of HIV-associated nephropathy

Human immunodeficiency virus-associated nephropathy (HIVAN) is a leading cause of end-stage renal disease in the HIV-1-seropositive population. HIVAN, which is characterized by heavy proteinuria and a rapid decline in renal function, is caused by infection and subsequent expression of viral genes in renal epithelial cells, although the exact mechanism of viral entry into these cells is unknown. The infected renal epithelium is a distinct compartment that supports the evolution of viral strains that may diverge from those found in the patient's blood. Research using animal models and in vitro studies has shown that vpr and nef are the HIV-1 genes most responsible for inducing the characteristic clinical and histopathologic syndrome of HIVAN. Dysregulation of several host factors, including mediators of inflammation, apoptosis, proliferation, transcription, and cell-cell interactions, are also critical factors in determining whether infection of the renal epithelium will lead to HIVAN. Additional research is required to delineate the mechanisms of HIVAN pathogenesis further so that more effective interventions can be implemented to prevent and treat this disease.

Acute kidney injury in HIV-infected patients

Acute kidney injury is common in human immunodeficiency virus (HIV)-infected patients, and has been associated with increased morbidity and mortality. Before the introduction of effective antiretroviral therapy, acute kidney injury in HIV-positive patients was most commonly the result of volume depletion, septicemia, or nephrotoxic medications. Acute kidney injury remains a significant problem in the antiretroviral era, and still commonly is attributed to infection or nephrotoxic medications. Less common causes such as direct infectious insults, immune restoration inflammatory syndrome, rhabdomyolysis, and obstruction should be considered when the underlying process is not obvious. In addition to advanced HIV disease, several other patient characteristics have emerged as potential risk factors for acute kidney injury in the antiretroviral era, including older age, diabetes, pre-existing chronic kidney disease, and hepatitis co-infection or liver disease.