Antiviral Drug-Induced Nephrotoxicity

Pharmacologically-induced metabolic acidosis: a review

Metabolic acidosis may occasionally develop in the course of treatment with drugs used in everyday clinical practice, as well as with the exposure to certain chemicals. Drug-induced metabolic acidosis, although usually mild, may well be life-threatening, as in cases of lactic acidosis complicating antiretroviral therapy or treatment with biguanides. Therefore, a detailed medical history, with special attention to the recent use of culprit medications, is essential in patients with acid-base derangements. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on the acid-base status. In this review, we evaluate relevant literature with regard to metabolic acidosis associated with specific drug treatment, and discuss the clinical setting and underlying pathophysiological mechanisms. These mechanisms involve renal inability to excrete the dietary H+ load (including types I and IV renal tubular acidoses), metabolic acidosis owing to increased H+ load (including lactic acidosis, ketoacidosis, ingestion of various substances, administration of hyperalimentation solutions and massive rhabdomyolysis) and metabolic acidosis due to HCO3- loss (including gastrointestinal loss and type II renal tubular acidosis). Determinations of arterial blood gases, the serum anion gap and, in some circumstances, the serum osmolar gap are helpful in delineating the pathogenesis of the acid-base disorder. In all cases of drug-related metabolic acidosis, discontinuation of the culprit medications and avoidance of readministration is advised.

[Diagnosis, treatment and prevention of renal diseases in HIV infected patients. Recommendations of the Spanish AIDS Study Group/National AIDS Plan]

The incidence of opportunistic infections and tumours in HIV-infected patients has sharply declined in the HAART era. At the same time there has been a growing increase of other diseases not directly linked to immunodeficiency. Renal diseases are an increasing cause of morbidity and mortality among HIV-infected patients. In the general population, chronic renal failure has considerable multiorgan repercussions that have particular implications in patients with HIV infection. The detection of occult or subclinical chronic kidney disease is crucial since effective measures for delaying progression exist. Furthermore, the deterioration in glomerular filtration should prompt clinicians to adjust doses of some antiretroviral agents and other drugs used for treating associated comorbidities. Suppression of viral replication, strict control of blood pressure, dyslipidemia and diabetes mellitus, and avoidance of nephrotoxic drugs in certain patients are fundamental components of programs aimed to prevent renal damage and delaying progression of chronic kidney disease in patients with HIV. Renal transplantation and dialysis have also special implications in HIV-infected patients. In this article, we summarise the updated clinical practice guidelines for the evaluation, management and prevention of renal diseases in HIV-infected patients from a panel of experts in HIV and nephrologists on behalf of the Spanish AIDS Study Group (GESIDA) and the National AIDS Plan.

Aging with HIV: clinical considerations for an emerging population

OVERVIEW

Since the advent of highly active antiretroviral therapy, HIV infection has become a chronic, albeit life-threatening, condition that can be managed; therefore, more and more people are growing older with HIV. Although little research has been conducted on how HIV infection and the aging process interact to affect patient care and well-being, the bodies of literature pertaining to gerontology and HIV and AIDS offer some guidance. It can be helpful for the nurse to have a brief overview of some common concerns--in particular, the potential for drug interactions or toxicities, cognitive declines, and emotional problems--that nurses and other health care professionals are likely to face when providing care to older adults with HIV.

Efficacy and safety of tenofovir disoproxil fumarate in patients with chronic hepatitis B

Chronic hepatitis B (CHB) is prevalent worldwide. It may cause cirrhosis and hepatocellular carcinoma. Treatment for this condition may need to be lifelong, thus the drugs used must be both efficacious and safe. Clinical trials of tenofovir have demonstrated a good safety profile for this drug and it has potent antiviral properties. However, to better characterize the safety of this drug, the postmarketing surveillance must be taken into account. Clinicians need to be vigilant, as infrequent adverse events may be revealed during this phase. The current review presents a detailed exposé of preclinical and clinical data on tenofovir to increase awareness of possible adverse events and drug-drug interactions, based on the large experience of this drug in human immunodeficiency virus (HIV) treatment (and to date in patients with CHB). Several recommendations that may help the clinician to prevent the development of adverse events associated with tenofovir disoproxil fumarate (TDF) treatment are outlined, along with a suggested surveillance protocol for the timely and proper identification of possible renal and bone toxicity.

Impact of tenofovir on renal function in HIV-infected, antiretroviral-naive patients

OBJECTIVE

To better characterize the long-term effects of tenofovir on renal function in a large managed care organization.

METHODS

We performed a retrospective cohort analysis in Kaiser Permanente for years 2002 to 2005 comparing renal function among antiretroviral naïve patients initiating a tenofovir-containing regimen (964 patients) or tenofovir-sparing regimens (683 patients). We evaluated glomerular filtration rate (GFR, [Modification of Diet in Renal Disease equation]), serum creatinine, and the development of renal proximal tubular dysfunction. We report multivariable hazard ratios (HR, Cox modeling) and linear outcomes (repeated measures) with predictors retained if P < 0.10 (backward selection). Potential predictor variables included in multivariate models were age, sex, Black race, baseline laboratories (including CD4 count), history of diabetes mellitus, hypertension, malignancy, hepatitis, and concurrent medications.

RESULTS

Overall, tenofovir-exposed patients had a larger relative decline in GFR through 104 weeks (-7.6 mL/min/1.73 m(2) relative to tenofovir-sparing, P < 0.001); the degree of the difference varied by baseline GFR, with the greatest effect seen in those patients with GFR greater than 80 mL/min/1.73 m(2). Tenofovir-exposed patients had greater development of proximal tubular dysfunction over time (at 52 wk: HR(adjusted) = 1.95 [P = 0.01] and at 104 wk: HR(adjusted) = 5.23 [P = 0.0004]) and had greater risk of medication discontinuation (HR(adjusted) = 1.21, P = 0.02), especially as renal function worsened. Viral control and CD4 count changes were similar between the two groups.

CONCLUSIONS

Tenofovir is associated with greater effect on decline in renal function and a higher risk of proximal tubular dysfunction in antiretroviral naïve patients initiating antiretroviral therapy.

Mechanisms of drug-induced nephrotoxicity

Drug-induced nephrotoxicity is a common complication of several medications and diagnostic agents. It is seen in both inpatient and outpatient settings with variable presentations ranging from mild, reversible injury to advanced kidney disease. Manifestations of drug-induced nephrotoxicity include acid-base abnormalities, electrolyte imbalances, urine sediment abnormalities, proteinuria, pyuria, hematuria, and, most commonly, a decline in the glomerular filtration rate. The mechanisms of drug-induced nephrotoxicity may differ between various drugs or drug classes, and they are generally categorized based on the histological component of the kidney that is affected. Aminoglycoside antibiotics, radiocontrast media, conventional nonselective nonsteroidal anti-inflammatory drugs, and selective cyclooxygenase-2 inhibitors, amphotericin B, and angiotensin-converting enzyme inhibitors have been frequently implicated. This chapter reviews the clinical presentation and basic mechanisms of drug-induced nephrotoxicity.

Prophylactic antivirals may be helpful in prevention of varicella-zoster virus reactivation in myeloma, but are they safe?

PURPOSE

Retrospective analysis of two recent multiple myeloma (MM) clinical trials suggested that the use of bortezomib may be associated with an increased incidence of herpes zoster infections. Therefore, prophylactic use of antivirals has been advocated by some authors. This article explores the potential risks and pitfalls linked to routine acyclovir prophylaxis in bortezomib-treated MM.

SUMMARY

use of antivirals can be associated with important nephro- and neurotoxicity. The nephrotoxicity induced by MM itself and its supportive therapies, superimposed to aging and inherent immunosuppression in myeloma, makes the development of renal impairment even more likely. On the other hand, sensory neuropathy is known to occur both during myeloma progression and in the setting of bortezomib therapy. Furthermore, preexisting nephropathy in MM patients can contribute to the occurrence of serious neurologic toxicity with acyclovir.

CONCLUSIONS

long-term acyclovir prophylaxis in MM patients treated with bortezomib may cause severe renal and neurological toxicity. Prevention of these complications can be achieved through either withholding of the antivirals or a very close monitoring of both neurologic status and renal function in this patient population. This highlights the importance of both clinician's and pharmacist's involvement in optimization of myeloma patient care.

Pharmacogenetics of tenofovir treatment

Tenofovir disoproxil fumarate (TDF) is a nucleotide analog used as part of HIV therapy. Its favorable profile in terms of high efficacy, low toxicity and once-daily dosing makes TDF one of the most attractive antiretroviral agents, and therefore, it is widely used. However, cases of kidney tubular dysfunction have been reported and concern exists regarding the long term use of TDF. Owing to the high interindividual variability in the presentation of kidney function abnormalities, research has recently focused on host genetic factors predisposing to TDF-associated renal dysfunction. Transporter proteins involved in the renal elimination of TDF, such as organic anion transporter 1 or multidrug resistant protein 2 or 4, seem to be involved importantly and several genetic polymorphisms in these proteins have been associated with an increased risk of kidney tubulopathy in patients treated with TDF. In this review, all relevant pharmacogenetic factors that may play a role in the risk of renal toxicity associated with the use of tenofovir are summarized.

Antiretroviral tissue kinetics: in vivo imaging using positron emission tomography

Our current knowledge on the antiviral efficacy, dosing, and toxicity of available highly active antiretroviral therapy regimens is mostly derived from plasma or blood kinetics of anti-human immunodeficiency virus (anti-HIV) drugs. However, the blood comprises only 2% of the total target cells in the body. Tissue drug levels may differ substantially from corresponding plasma levels, and drug distribution processes may be characterized by high intertissue variability, leading to suboptimal target site concentrations and the potential risk for therapeutic failures. Positron emission tomography has greatly expanded the scope of the pharmacokinetic measurements that can be performed noninvasively in animal models or humans. We have prepared [18F]FPMPA, a fluorine-18-radiolabeled analogue of tenofovir, to study antiretroviral tissue kinetics in vivo noninvasively and tested the imaging probe in rats. The biodistribution of the fluorine-18 analogue closely follows that of nonfluorinated tenofovir. Compared to that in the blood, the levels of penetration of the antiretroviral drug were found to be significantly reduced in the spleen and submandibular lymph nodes (approximately 2-fold), in the mesenteric lymph nodes and the testes (approximately 4-fold), and in the brain compartment (approximately 25-fold). Intersubject variability of the trough drug concentration (measured at 120 min) in certain tissues, like the colon (coefficient of variation, >100%), is not reflected by the intersubject variability in the blood compartment (coefficient of variation, 24%). Positron emission tomography imaging of the fluorine-18 analogue revealed the accumulation of the antiretroviral drug in the cortex of the kidneys, a potential correlate of tenofovir-induced nephrotoxicity observed in HIV-1-infected treated patients. Thus, [18F]FPMPA is a promising radiotracer for evaluation of tenofovir biodistribution under carefully controlled drug administration protocols.

Renal function with use of a tenofovir-containing initial antiretroviral regimen

OBJECTIVES

To determine whether tenofovir disoproxil fumarate (TDF) is associated with renal dysfunction when used as part of an initial antiretroviral regimen and to assess the effect of ritonavir-boosted protease inhibitor (PI/r) coadministration on renal function in TDF-treated patients.

DESIGN

Analysis from a prospective observational cohort.

METHODS

: We compared all antiretroviral-naive patients with an estimated glomerular filtration rate (eGFR) of more than 50 ml/min per 1.73 m (modification of diet in renal disease equation) who initiated either TDF (n = 201) or any alternative nucleoside reverse transcriptase inhibitor (NRTI) (n = 231) after 1 January 2002.

RESULTS

Patients taking both TDF and NRTIs experienced an initial decline in eGFR during the first 180 days of therapy, but eGFR stabilized between 180 and 720 days. There was no difference between TDF and NRTI use in 25 or 50% decline in eGFR at 1 or 2 years or in change in eGFR at 6, 12, or 24 months. Those taking TDF and a PI/r had a greater median decline in eGFR than those taking TDF and a non-NRTI at 6 months (P = 0.01), with trends at 12 (P = 0.08) and 24 months (P = 0.08). There was no difference in median GFR decline between those on an NRTI and PI/r vs. an NRTI and non-NRTI.

CONCLUSION

Our data are consistent with results of clinical trials, which have shown no evidence of renal toxicity when TDF is used as part of an initial regimen. Our results support the use of TDF as a component of the initial antiretroviral regimen, and suggest that the eGFR should be monitored more closely when TDF is used with a PI/r.

Response to adefovir or entecavir in renal allograft recipients with hepatitic flare due to lamivudine-resistant hepatitis B

We studied the effects of adefovir or entecavir in six kidney transplant recipients (mean age 45.7 +/- 7.8 yr) who developed hepatitic flare due to lamivudine-resistant hepatitis B virus (HBV) infection, with 18 months of follow-up. All patients had elevated alanine aminotransferase (ALT) levels and HBV DNA >10(5) copies/mL (median 2.15 x 10(8) copies/mL) at baseline. Serum creatinine and creatinine clearance levels were 137.8 +/- 59.7 mumol/L and 62.6 +/- 18.7 mL/min, respectively. Four patients were treated with adefovir and two with entecavir. Median HBV DNA decreased to 1.99 x 10(5) copies/mL (p = 0.028) after six months, 1.5 x 10(4) copies/mL (p = 0.043) after 12 months, and 7.35 x 10(4) copies/mL (p = 0.068) after 18 months of treatment. There was a corresponding improvement in ALT (34.5 +/- 19.1 U/L after 18 months, p = 0.029 compared with baseline). The rate of HBV DNA suppression was variable, and three patients took over six months for the viral load to decrease to <10(5) copies/mL. After 18 months, HBV DNA was <10(5) copies/mL in four patients and <10(2) copies/mL in one patient. Treatment was well-tolerated and renal function remained stable. We conclude that both adefovir and entecavir are effective in the treatment of lamivudine-resistant HBV in renal allograft recipients, and the reduction of HBV DNA to <10(5) copies/mL could be slow.

Treatment of HBV-related cirrhosis

The goal of antiviral therapy in HBV cirrhotic patients is to prevent progression of the disease to decompensated cirrhosis, end-stage liver disease, hepatocellular carcinoma and death. This goal can be achieved if HBV replication can be suppressed, leading to biochemical remission, histological improvement and prevention of complications. If finite treatment with pegylated interferon is not contraindicated in compensated cirrhosis, long-term treatment with nucleoside/nucleotide analogues is recommended in patients with HBV-related cirrhosis, especially in decompensated cirrhosis. Patients with cirrhosis require careful monitoring to detect resistance and prevent flares, and also to screen for hepatocellular carcinoma, portal hypertension and liver failure.

Therapeutic paint of cidofovir/sucralfate gel combination topically administered by spraying for treatment of orf virus infections

The aim of the research was to study a new cidofovir/sucralfate drug product to be used as a spray for treating the mucosal and/or skin lesions. The product, i.e., a water suspension of sucralfate (15% w/w) and cidofovir (1% w/w), combines the potent antiviral activity of the acyclic nucleoside phosphonate cidofovir ((S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine) and the wound healing properties of sucralfate gel (sucrose octasulphate basic aluminum salt). The product was characterized in vitro with respect to compatibility between drug and carrier, spray particle size, spray deposition, drying kinetics, and drug content and release. An interaction between the two active substances was found. The interaction between sucralfate and cidofovir was counteracted by introducing sodium dihydrogen phosphate (16% w/w) in the preparation. The spray formulation containing cidofovir/sucralfate gel painted the skin and dried quickly to a scab, remaining firmly adhered to the lesions. The therapeutic paint was tested in vivo on lambs infected with orf virus by treating the animals with different cidofovir/sucralfate formulations (0.5% or 1% cidofovir + sucralfate 15% + NaH(2)PO(4) 16% w/w) and with sucralfate gel suspension alone as control. The treatment with formulations containing cidofovir and phosphate salt for four consecutive days resulted in a rapid resolution of the lesions, with scabs containing significantly lower amounts of viable virus when compared with untreated lesions and lesions treated with sucralfate suspension alone.

Multiphoton imaging reveals differences in mitochondrial function between nephron segments

Mitochondrial dysfunction may play a role in the pathogenesis of several renal diseases. Although functional roles and metabolic demands differ among tubule segments, relatively little is known about the properties of mitochondria in different parts of the nephron. Clinically, the proximal tubule seems particularly vulnerable to mitochondrial toxicity. In this study, we used multiphoton imaging of live rat kidney slices to investigate differences in mitochondrial function along the nephron. The mitochondrial membrane potential was markedly higher in distal than proximal tubules. Inhibition of respiration rapidly collapsed the membrane potential in proximal tubules, but potential was better maintained in distal tubules. Inhibition of the F1F(o)-ATPase abolished this difference, suggesting that maintenance of potential via ATPase activity is more effective in distal than proximal tubules. Immunostaining revealed that the ratio of the expression of ATPase to IF1, an endogenous inhibitor of the mitochondrial ATPase, was lower in proximal tubules than in distal tubules. Production of reactive oxygen species was higher in proximal than distal cells, but inhibition of NADPH oxidase eliminated this difference. Glutathione levels were higher in proximal tubules. Overall, mitochondria in the proximal tubules were in a more oxidized state than those in the distal tubules. In summary, there are axial differences in mitochondrial function along the nephron, which may contribute to the pattern and pathophysiology of some forms of renal injury.

Alkoxyalkyl prodrugs of acyclic nucleoside phosphonates enhance oral antiviral activity and reduce toxicity: current state of the art

Although the acyclic nucleoside phosphonates cidofovir, adefovir and tenofovir are approved for treating human cytomegalovirus, hepatitis B and HIV infections, respectively, their utility is limited by low oral bioavailability, renal toxicity and poor cell penetration. Research over the past decade has shown that these undesirable features can be eliminated by esterifying the compounds with an alkoxyalkyl group, in effect disguising them as lysophospholipids. In this modified form, the drugs are readily taken up in the gastrointestinal tract and have a prolonged circulation time in plasma. The active metabolite also has a long half life within cells, permitting infrequent dosing. Because these modified drugs are not recognized by the transport mechanisms that cause the accumulation of acyclic nucleoside phosphonates in renal tubular cells, they lack nephrotoxicity. Alkoxyalkyl esterification also markedly increases the in vitro antiviral activity of acyclic nucleoside phosphonates by improving their delivery into cells. For example, an alkoxyalkyl ester of cyclic-cidofovir, a less soluble compound, retains anti-CMV activity for 3 months following a single intravitreal injection. Two of these novel compounds, hexadecyloxypropyl-cidofovir (CMX001) and hexadecyloxypropyl-tenofovir (CMX157) are now in clinical development. This article focuses on the hexadecyloxypropyl and octadecyloxyethyl esters of cidofovir and (S)-HPMPA, describing their synthesis and the evaluation of their in vitro and in vivo activity against a range of orthopoxviruses, herpesviruses, adenoviruses and other double-stranded DNA viruses. The extension to other nucleoside phosphonate antivirals is highlighted, demonstrating that this novel approach can markedly improve the medicinal properties of these drugs.

Side effects of long-term oral antiviral therapy for hepatitis B

The aim of this review is to summarize the safety profile of the five approved oral nucleoside analogs used to treat chronic hepatitis B virus (HBV) infection, focusing on both the class adverse effects and those that have been reported with individual agents, as well as their safety in pregnancy. All nucleoside analogs have a "Black Box" warning because of their potential for inhibition of human DNA polymerase gamma involved in mitochondrial DNA replication. A reduction in intracellular mitochondrial DNA levels can lead to varying clinical manifestations of mitochondrial toxicity (i.e., neuropathy, myopathy, lactic acidosis), but these side effects are rarely reported with the oral antiviral agents active against HBV. Adefovir and tenofovir are associated with a dose-dependent but usually reversible proximal renal tubular toxicity. For these reasons, patients receiving these agents should be monitored for renal toxicity and the dose modified for renal insufficiency. Prolonged use of tenofovir has also been reported to lead to reduced bone mineral density in patients with human immunodeficiency virus infection, but prospective studies in patients with HBV infection are lacking. Telbivudine treatment is associated with moderate serum creatine phosphokinase elevations in up to 12% of patients. There have been few prospective studies on the safety of nucleoside analogs during pregnancy. According to the Antiretroviral Pregnancy Registry, the incidence of birth defects associated with lamivudine and tenofovir use during pregnancy is not increased. Studies on the safety of long-term therapy with the nucleoside analogs, alone and in combination, are needed as are further studies of children, the elderly, pregnant women, and patients with renal insufficiency.

[Kidney diseases in HIV-infected patients]

HIV infection has become a global disease, both in geographic terms, since it has spread worldwide, and at the individual level since it affects every organ of the human body. Antiretroviral treatments, in countries where they are easily available, have modified HIV infection into a systemic chronic disease, the life expectancy of which is yet to be determined precisely. Treatments have dramatically changed the pattern of the disease and clinicians now have to face a number of new challenges. Kidneys, like all the other organs, can be involved in a great number of diseases in HIV-infected patients. We have voluntarily chosen to present "kidney diseases in HIV-infected patients" in their wider meaning, with a discussion of renal diseases that are directly caused by the virus, nephropathies due to frequent viral co-infections in HIV-infected patients such as HCV and HBV, nephropathies induced by anti-HIV, HBV and HCV therapies. Physicians in charge of HIV-infected patients should be aware of the key role they have to play in the screening for kidney abnormalities. This participates not only in improving patients' kidney prognosis but also their long-term general outcome. Renal screening strategies must refer to simple routine laboratory tests. Enclosed at the end of this article are a few suggestions for the renal management of situations that frequently occur in HIV infected patients (kidney dysfunction screening, serum creatinine increase and discovery of a proteinuria).

Progressive renal tubular dysfunction associated with long-term use of tenofovir DF

It became evident that tenofovir DF (TDF) causes a modest and gradual decline in GFR, however, the impact of long-term use of TDF on tubular function has not been fully evaluated. In 40 patients treated with TDF and 23 patients treated with other NRTIs, urine beta(2)-microglobulin (U-BMG), percentage tubular reabsorption of phosphate (%TRP), alkaline phosphatase (ALP), serum creatinine, and calculated GFR were prospectively measured for 96 weeks. In patients receiving TDF, median U-BMG rose from 188 microg/liter at baseline to 555 microg/liter at week 96 (p = 0.02), median %TRP declined from 94% at baseline to 90% at week 96 (p = 0.002), median ALP ratio compared with baseline persistently increased from 1 to 1.278 at week 96 (p = 0.001), and serum creatinine showed significant but minimal change from 0.64 mg/dl to 0.74 mg/dl at week 96 (p = 0.02). The GFR level declined minimally but significantly in TDF-receiving patients (-17 ml/min/1.73 m(2)), whereas it did not change in other NRTI-receiving patients [+ 3 ml/min/1.73 m(2); mixed models analysis of variance (MMANOVA) p = 0.03 for overall change from baseline to week 96]. U-BMG, %TRP, ALP, or serum creatinine did not change significantly in other NRTI-receiving patients during the observation period. In five patients with marked changes in U-BMG (>10,000 microg/liter) and %TRP (<80%), both U-BMG and %TRP immediately recovered in all patients after discontinuing TDF, whereas GFR levels did not fully recover for 6 months in three patients. Prolonged treatment with TDF caused progressive renal tubular dysfunction as well as a modest decline in GFR. If U-BMG levels >10,000 microg/liter and %TRP values <80% are observed, discontinuing TDF may be beneficial.

Acute kidney injury in patients with human immunodeficiency virus infection

PURPOSE OF REVIEW

To present an overview of the epidemiology and etiology of acute kidney injury (AKI) in patients infected with human immunodeficiency virus (HIV).

RECENT FINDINGS

HIV-infected patients are at an increased risk of developing AKI. Potential risk factors for the development of AKI in this patient population include increased HIV viral loads, reduced CD4 cell counts, hepatitis C virus coinfection, a history of diabetes, black race, male gender, and baseline chronic kidney and hepatic disease. Observational studies have found an increased morbidity and mortality in HIV-infected patients who develop AKI. There are diverse etiologies of AKI in HIV-infected patients, with increasing reports of highly active antiretroviral therapy-related nephropathy secondary to tenofovir nephrotoxicity. There have also been recent case reports of HIV-infected patients who develop a unique form of acute interstitial nephritis secondary to diffuse infiltrative lymphocytosis syndrome.

SUMMARY

There are a variety of etiologies of AKI in HIV-infected patients. Prompt diagnosis and treatment of AKI is critical to help prevent morbidity and mortality in this patient population.

Adenovirus DNA polymerase is recognized by human CD8+ T cells

Donor lymphocytes have potential as a treatment for adenovirus (Ad) disease in haematopoietic stem cell transplant (SCT) recipients, but better understanding of Ad-specific T-cell responses is required. Most healthy adults exhibit memory T-cell responses to hexon, a capsid protein synthesized late after infection. However, since the Ad E3-19k downregulates major histocompatibility complex (MHC) class I molecules, cytotoxic T cells (CTLs) targeted to early viral proteins may be more effective in eliminating Ad-infected cells in vivo. Here we show that Ad-specific CTLs recognize the early region 2 proteins DNA polymerase (Pol) and DNA-binding protein (DBP). Firstly, memory Ad-specific CD8(+) T cells were amplified from healthy donors by in vitro stimulation with Ad-infected dendritic cells and found to exhibit MHC-restricted cytotoxicity to targets expressing Pol and DBP. Secondly, gamma interferon responses to HLA A2-binding motif peptides from Pol and DBP were directly detected in peripheral blood mononuclear cells (PBMCs) from a recently infected normal donor. Peptide-specific CTLs generated to Pol and DBP epitopes were confirmed to exhibit HLA A2-restricted killing of targets expressing Pol or DBP. Lastly, Pol-epitope-specific T cells were detected at similar or higher frequencies than hexon and DBP in three of three SCT recipients recovering from invasive Ad disease. Pol epitopes were well conserved among different Ad serotypes. Therefore, Pol is a promising target for immunotherapy of Ad disease.

Emerging therapy-related kidney disease

CONTEXT

Many new therapies have emerged within the last 5 to 10 years to treat a variety of conditions. Several of these have direct or indirect renal toxicities that may go undiagnosed without careful attention of the pathologist to a patient's clinical history, particularly the addition of new medications or treatments.

OBJECTIVE

To discuss patterns of renal injury resulting from medications or therapeutic regimens that have been introduced within the last 10 years. Recognition of these patterns may allow the pathologist to alert the attending clinician to a possible drug-induced renal injury and prevent further deterioration of renal function and possible chronic kidney disease.

DATA SOURCES

A review of recent literature and unpublished observations of case-derived material.

CONCLUSIONS

A number of newer therapies have emerged as agents of renal toxicity, producing a variety of pathologic changes in the kidney. The outcome can be acute or chronic glomerular, tubular, interstitial, and/or vascular injury. Some drugs will result in irreversible changes and end-stage renal disease, whereas many of the alterations can be reversed with removal of the offending agent, avoiding potential long-term kidney injury.

The epidemiology of drug-induced disorders: the kidney

The epidemiology of drug-induced renal disorders is a complex topic. Drug-associated nephrotoxicity accounts for 18 - 27% of all acute kidney injury cases in US hospitals. Medications can affect all aspects of the kidney, and drugs that are associated with renal dysfunction are used commonly in clinical practice. The article reviews six major mechanisms of drug-induced renal dysfunction as well as lists the major medications involved. NSAIDs, aminoglycosides, amphotericin B and calcineurin inhibitors are just some examples of drugs that contribute to renal dysfunction. The medical community must be aware of patient risk factors for nephrotoxicity, as well as the drug's inherent nephrotoxic potential, when prescribing and administering medications.

Coadministration of cidofovir and smallpox vaccine reduced vaccination side effects but interfered with vaccine-elicited immune responses and immunity to monkeypox

While the smallpox vaccine, Dryvax or Dryvax-derived ACAM2000, holds potential for public immunization against the spread of smallpox by bioterror, there is serious concern about Dryvax-mediated side effects. Here, we report that a single-dose vaccination regimen comprised of Dryvax and an antiviral agent, cidofovir, could reduce vaccinia viral loads after vaccination and significantly control Dryvax vaccination side effects. However, coadministration of cidofovir and Dryvax also reduced vaccine-elicited immune responses of antibody and T effector cells despite the fact that the reduced priming could be boosted as a recall response after monkeypox virus challenge. Evaluations of four different aspects of vaccine efficacy showed that coadministration of cidofovir and Dryvax compromised the Dryvax-induced immunity against monkeypox, although the covaccinated monkeys exhibited measurable protection against monkeypox compared to that of naïve controls. Thus, the single-dose coadministration of cidofovir and Dryvax effectively controlled vaccination side effects but significantly compromised vaccine-elicited immune responses and vaccine-induced immunity to monkeypox.

Low dosage cidofovir without probenecid as treatment for BK virus hamorrhagic cystitis after hemopoietic stem cell transplant

We describe a single-center pediatric experience with 1 mg/kg/wk cidofovir without probenecid in 7 children with BK virus-associated hemorrhagic cystitis. Clinical improvement was observed in all cases, without adverse events, although significant reduction of urinary viral load was observed 2 weeks after the end of cidofovir in 5 out of 6 patients who completed the treatment.

Nephrotoxicity as a cause of acute kidney injury in children

Many different drugs and agents may cause nephrotoxic acute kidney injury (AKI) in children. Predisposing factors such as age, pharmacogenetics, underlying disease, the dosage of the toxin, and concomitant medication determine and influence the severity of nephrotoxic insult. In childhood AKI, incidence, prevalence, and etiology are not well defined. Pediatric retrospective studies have reported incidences of AKI in pediatric intensive care units (PICU) of between 8% and 30%. It is widely recognized that neonates have higher rates of AKI, especially following cardiac surgery, severe asphyxia, or premature birth. The only two prospective studies in children found incidence rates of 4.5% and 2.5% of AKI in children admitted to PICU, respectively. Nephrotoxic drugs account for about 16% of all AKIs most commonly associated with AKI in older children and adolescents. Nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, amphotericin B, antiviral agents, angiotensin-converting enzyme (ACE) inhibitors, calcineurin inhibitors, radiocontrast media, and cytostatics are the most important drugs to indicate AKI as significant risk factor in children. Direct pathophysiological mechanisms of nephrotoxicity include constriction of intrarenal vessels, acute tubular necrosis, acute interstitial nephritis, and-more infrequently-tubular obstruction. Furthermore, AKI may also be caused indirectly by rhabdomyolysis. Frequent therapeutic measures consist of avoiding dehydration and concomitant nephrotoxic medication, especially in children with preexisting impaired renal function.

Novel nucleotide human immunodeficiency virus reverse transcriptase inhibitor GS-9148 with a low nephrotoxic potential: characterization of renal transport and accumulation

Accumulation of antiviral nucleotides in renal proximal tubules is controlled by their basolateral uptake via the human renal organic anion transporters type 1 (hOAT1) and 3 (hOAT3) and apical efflux via the multidrug resistance protein 4 (MRP4). GS-9148 is a novel ribose-modified nucleotide human immunodeficiency virus (HIV) reverse transcriptase inhibitor, and its oral prodrug GS-9131 is currently being evaluated in the clinic as an anti-HIV agent. To assess the potential of GS-9148 for nephrotoxicity, its mechanism of renal transport, cytotoxicity, and renal accumulation were explored in vitro and in vivo. In comparison with the acyclic nucleotides cidofovir, adefovir, and tenofovir, GS-9148 showed 60- to 100-fold lower efficiency of transport (V(max)/K(m)) by hOAT1 and was 20- to 300-fold less cytotoxic in cells overexpressing hOAT1, indicating its lower hOAT1-mediated intracellular accumulation and reduced intrinsic cytotoxicity. GS-9148 was also relatively inefficiently transported by hOAT3. Similar to acyclic nucleotides, GS-9148 was a substrate for MRP4 as evidenced by its reduced intracellular retention in cells overexpressing the efflux pump. Consistent with these molecular observations, GS-9148 was inefficiently taken up by fresh human renal cortex tissue in vitro and showed a limited accumulation in kidneys in vivo following oral administration of [(14)C]GS-9131 to dogs. Compared to acyclic nucleotide analogs, GS-9148 was also found to have lower net active tubular secretion in dogs. Collectively, these results suggest that GS-9148 exhibits a low potential for renal accumulation and nephrotoxicity.

Determinants of aciclovir-induced nephrotoxicity in children

BACKGROUND

Aciclovir is the drug of choice for severe systemic herpes virus infections. Nephrotoxicity is one of the clinically significant adverse effects of this drug, but studies examining nephrotoxicity in children are scarce.

OBJECTIVE

To identify risk factors for aciclovir-associated nephrotoxicity in the pediatric population.

PATIENTS AND METHODS

A retrospective review was conducted on all children (mean age 81 months; n = 126 [74 boys]) who were treated with aciclovir in a tertiary center between July 2005 and January 2006 and who met our inclusion criteria. Glomerular filtration rate (GFR) was calculated on the first day of treatment and at the peak measured creatinine level while on therapy, using Schwartz's method.

RESULTS

Aciclovir therapy was associated with a significant increase in serum creatinine levels and a parallel decrease in GFR (n = 93; both p <or= 0.0001). Children with immunosuppression who received a variety of other nephrotoxic drugs exhibited more severe nephrotoxicity than those not receiving nephrotoxic drugs. In multiple regression analysis, the use of nephrotoxic drugs (p = 0.02) and impaired GFR at baseline (p = 0.04) were predictive for nephrotoxicity.

CONCLUSIONS

Within the recommended age-dependent dosage schedule of aciclovir there was no effect of dose per kg, age, or sex on nephrotoxicity. The predictors of aciclovir nephrotoxicity were the concomitant use of nephrotoxic drugs and impaired GFR at baseline.

Fanconi syndrome and lactic acidosis associated with stavudine and lamivudine therapy

We report a case of the nucleoside reverse transcriptase inhibitors, stavudine and lamivudine inducing Fanconi syndrome in a patient. The presence of simultaneous lactic acidosis suggests mitochondrial toxicity within the proximal renal tubular cells as the likely pathogenesis. We recommend that both the above nucleosides be added to the list of antiretroviral drugs that can induce Fanconi syndrome and that patients on stavudine and lamivudine be monitored carefully for early signs of Fanconi syndrome.

Rosiglitazone reverses tenofovir-induced nephrotoxicity

Tenofovir disoproxil fumarate (TDF) is a first-line drug used in patients with highly active retroviral disease; however, it can cause renal failure associated with many tubular anomalies that may be due to down regulation of a variety of ion transporters. Because rosiglitazone, a peroxisome proliferator-activated receptor-gamma agonist induces the expression of many of these same transporters, we tested if the nephrotoxicity can be ameliorated by its use. High doses of TDF caused severe renal failure in rats accompanied by a reduction in endothelial nitric-oxide synthase and intense renal vasoconstriction; all of which were significantly improved by rosiglitazone treatment. Low-dose TDF did not alter glomerular filtration rate but produced significant phosphaturia, proximal tubular acidosis, polyuria and a reduced urinary concentrating ability. These alterations were caused by specific downregulation of the sodium-phosphorus cotransporter, sodium/hydrogen exchanger 3 and aquaporin 2. A Fanconi's-like syndrome was ruled out as there was no proteinuria or glycosuria. Rosiglitazone reversed TDF-induced tubular nephrotoxicity, normalized urinary biochemical parameters and membrane transporter protein expression. These studies suggest that rosiglitazone treatment might be useful in patients presenting with TFV-induced nephrotoxicity especially in those with hypophosphatemia or reduced glomerular filtration rate.

[Antiretroviral drug toxicity in human immunodeficiency virus infected children]

Paediatric Human Immunodeficiency Virus infection (HIV) nowadays is a chronic disease with an excellent long term prognosis, but lifelong combined antiretroviral treatment is required. However, an improved quality of life in this population is limited by adverse drug effects. The highest risk of treatment toxicity is developing a complete metabolic syndrome including: Hyperlipemia, lipodystrophy, insulin resistance, lactic acidosis, osteopenia, hypertension, and specific system and organ toxicity, such as the kidney, liver, CNS or bone marrow. The risk of cardiovascular disease adult life and also definitive bone mass damage are the most significant metabolic costs that have to paid for increased survival. Most of these toxicities were able to be adequately treated but, pharmacological interferences, patient intolerance and the high number of drugs are the problems that limit the adherence to treatment, which is essential for a good therapeutical efficacy. In this article, we present four HIV paediatric patients who presented with almost the whole range of metabolic toxicities, and a practical overview of therapeutical management.

Clinical and genetic determinants of intracellular tenofovir diphosphate concentrations in HIV-infected patients

BACKGROUND

Nucleos(t)ide reverse transcriptase inhibitors (NRTIs), such as tenofovir, require intracellular phosphorylation for pharmacologic activity. Drug transporters may contribute to the intracellular disposition of NRTIs.

OBJECTIVE

We characterized intracellular tenofovir diphosphate (TFV-DP) concentrations in HIV-infected patients (n = 30), and investigated associations between TFV-DP concentrations and polymorphisms in the drug transporter genes SLC22A6, ABCC2, and ABCC4.

METHODS

Subjects were genotyped for 6 single-nucleotide polymorphisms: 2 in SLC22A6 (encodes influx transporter, human organic anion transporter 1), 728G>A and 453G>A; 2 in ABCC2 (encodes efflux transporter, multidrug resistance protein [MRP] 2), -24C>T and 1249G>A; and 2 in ABCC4 (encodes efflux transporter, MRP4), 3463A>G and 4131T>G.

RESULTS

The mean TFV-DP was 76.1 fmol/10(6) cells (range: 16.3 to 212 fmol/10(6) cells). Tenofovir apparent oral and renal clearances were significantly predictive of intracellular TFV-DP concentrations. For every 1-L/h decrease in tenofovir renal clearance, there was, on average, an 8% increase in TFV-DP (P = 0.002). We identified a novel relation between ABCC4 3463A>G genotype and TFV-DP. ABCC4 3463G variants had TFV-DP concentrations 35% higher (29 fmol/10(6) cells) than wild type (P = 0.04).

CONCLUSION

This study provides direction for future investigations to elucidate the contribution of clinical characteristics and drug transporter genotype to TFV-DP safety and efficacy.

An overview of drug-induced acute kidney injury

The complex nature of critical illness often necessitates the use of multiple therapeutic agents, many of which may individually or in combination have the potential to cause renal injury. The use of nephrotoxic drugs has been implicated as a causative factor in up to 25% of all cases of severe acute renal failure in critically ill patients. Acute tubular necrosis is the most common form of renal injury from nephrotoxin exposure, although other types of renal failure may be seen. Given that this is a preventable cause of a potentially devastating complication, a comprehensive strategy should be used to avoid nephrotoxicity in critically ill patients including: accurate estimation of pre-existing renal function using serum creatinine-based glomerular filtration rates, avoidance of nephrotoxins if possible, ongoing monitoring of renal function, and immediate discontinuation of suspected nephrotoxins in the event of renal dysfunction.

Outcome of management strategies for BK virus replication in pediatric renal transplant recipients

Management of BKV infection is not well defined. Eighteen pediatric renal transplant patients with BKV-PCR (+) were divided into three groups; Group 1: Viruria only (6), Group 2: Viremia with stable GFR (4), Group 3: Viremia with >25% decline in GFR and BKVAN on biopsy (8). With initial BKV-PCR(+), Group 1 received no treatment; Group 2 had MMF reduced 30%; Group 3: 6/8 had CNI discontinuation, 2/8 had reduced MMF and cidofovir. BKV, GFR and histology were compared pre- and post-treatment. In Group 1 viruria decreased in all patients; GFR remained stable. Group 2 showed reduced viremia with no GFR change. Group 3 showed reduced viremia in 8/8 patients. Patients with >50% decline in GFR from baseline (6/8) showed worse histology: 2/6 lost grafts despite no BKV on follow-up biopsy. Our results show that with viruria alone no treatment is necessary; with viremia and stable GFR, reduced immunosuppression decreases viremia and maintains GFR. With viremia and reduced GFR, immunosuppression reduction with or without cidofovir decreases viremia and stabilizes GFR in most patients. Greater than 50% reduction in GFR at BKVAN diagnosis correlates with risk for graft loss. Serial monitoring of BKV viremia with early intervention may prevent BKVAN graft loss in children.

End-stage renal disease and chronic kidney disease in a cohort of African-American HIV-infected and at-risk HIV-seronegative participants followed between 1988 and 2004

BACKGROUND

HIV-infected African-Americans are at increased risk of end-stage renal disease requiring renal replacement therapy (RRT).

OBJECTIVES

To compare the incidence of RRT in HIV-infected and HIV-seronegative African-Americans and describe temporal trends in RRT and chronic kidney disease (CKD) in HIV infection.

DESIGN

Cohort study in Baltimore including 4509 HIV-infected and 1746 HIV-seronegative African-Americans.

METHODS

Incident RRT was defined by matching participant identifiers with the US Renal Data System; CKD was defined as an estimated glomerular filtration rate < 60 ml/min per 1.73m for >/= 3 months. Standardized incidence ratios (SIR) and 95% confidence intervals (CI) were calculated by indirect adjustment. Risk factors for RRT were assessed by person-time methods and Poisson regression.

RESULTS

RRT was initiated in 24 HIV-seronegative subjects over 13 415 person-years of follow-up (SIR, 2.3; 95% CI, 1.5-3.4), in 51 HIV-infected participants without AIDS over 10 780 person-years (SIR, 6.9; 95% CI, 5.1-9.0), and in 125 participants with AIDS over 9833 person-years. SIR, 16.1; 95% CI, 13.4-19.2). In HIV-infected African-Americans, RRT incidences were 5.8 and 9.7/1000 person-years in the pre-HAART and HAART eras, respectively (adjusted rate ratio 1.2; 95% CI, 0.8-1.9). In supplementary analyses, CKD incidence declined significantly in the HAART era compared with pre-HAART, but the CKD period prevalence increased.

CONCLUSIONS

Nearly 1% of HIV-infected African-Americans initiated RRT annually, a rate that was similar in the HAART and pre-HAART eras. While new cases of CKD decreased, the prevalence of CKD increased in the HAART era, primarily because survival in those with HIV-associated CKD has improved.

IFN-alpha induces barrier destabilization and apoptosis in renal proximal tubular epithelium

Type I IFNs, like IFN-alpha, are major immune response regulators produced and released by activated macrophages, dendritic cells, and virus-infected cells. Due to their immunomodulatory functions and their ability to induce cell death in tumors and virus-infected cells, they are used therapeutically against cancers, viral infections, and autoimmune diseases. However, little is known about the adverse effects of type I IFNs on nondiseased tissue. This study examined the effects of IFN-alpha on cell death pathways in renal proximal tubular cells. IFN-alpha induced apoptosis in LLC-PK1 cells, characterized by the activation of caspase-3, -8, and -9, DNA fragmentation, and nuclear condensation. IFN-alpha also caused mitochondrial depolarization. Effector caspase activation was dependent on caspase-8 and -9. In addition to apoptosis, IFN-alpha exposure also decreased renal epithelial barrier function, which preceded apoptotic cell death. Caspase inhibition did not influence permeability regulation while significantly attenuating and delaying cell death. These results indicate that IFN-alpha causes programmed cell death in nondiseased renal epithelial cells. IFN-alpha-induced apoptosis is directed by an extrinsic death receptor signaling pathway, amplified by an intrinsic mitochondrial pathway. Caspase-dependent and -independent apoptotic mechanisms are involved. These findings reveal a novel aspect of IFN-alpha actions with implications for normal renal function in immune reactions and during IFN-alpha therapy.

Acute Interstitial Nephritis Associated with Coadministration of Vancomycin and Ceftriaxone: Case Series and Review of the Literature

We report what we believe to be the first two cases of acute interstitial nephritis associated with vancomycin and ceftriaxone therapy in adults. A 40-year-old man with a medical history of traumatic brain injury and tonic-clonic seizure disorder was admitted to the hospital with a seizure episode and temperature of 103 degrees F. He was administered ceftriaxone, vancomycin, and acyclovir for suspected bacterial and/or viral meningitis. On day 4, the patient was noted to have diffuse erythematous plaques on the neck, chest, arms, abdomen, and back, as well as an elevated serum creatinine level of 3.1 mg/dl (baseline 0.9 mg/dl) and an elevated eosinophil count (6%). Dermatology and renal consultations were obtained, and a diagnosis of suspected acute interstitial nephritis was made. After a 3-day course of antibiotic treatment (day 4 of hospitalization), all antibiotics were discontinued and topical triamcinolone 0.1% ointment and hydrocortisone 2.5% cream were begun for the rash. The patient was discharged 5 days later with improvement in the rash, serum creatinine level (1.0 mg/dl), and eosinophil count (0.9%). A 59-year-old woman with a medical history of diabetes mellitus was admitted to the hospital with a serum creatinine level of 3.7 mg/dl, eosinophil count of 8.4%, and fractional excretion of sodium of 2.94%. The patient had been receiving treatment with vancomycin and ceftriaxone for osteomyelitis for 28 days before this hospital admission. Her baseline serum creatinine level (before antibiotic therapy) was 1.0 mg/dl. Renal consultation was obtained, and a diagnosis of probable acute interstitial nephritis was made. Ceftriaxone and vancomycin were discontinued, and her serum creatinine level gradually decreased to 3.3 mg/dl and then further to 1.5 mg/dl over the next 3 months. Use of the Naranjo adverse drug reaction probability scale revealed that the adverse reaction was possible in the first case and probable in the second case. Health care professionals need to be cognizant that drug-induced acute interstitial nephritis can be associated with concomitant administration of ceftriaxone and vancomycin therapy. Early detection of this rare adverse reaction is paramount in order to prevent acute renal insufficiency.