Didanosine Treatment Research Articles

Subclinical myocardial disfunction detected by left ventricle myocardial work impairment in patients with long standing human inmmunodeficiency virus infection

Abstract Heart failure is a known complication in patients living with human inmmunodeficiency virus (HVI) infection. Detection of subclinical disfunction is nowadays possible by echocardiographic strain techniques. Myocardial work is a novel technique based on global longitudinal strain (GLS) that measures global work efficiency of left ventricle (GWE) and would allow early detection of subclinical myocardial damage. Methods We performed a cross sectional echocardiographic study of patients with long standing HIV infection, and no previous cardiopathy, assessing GLS of left ventricle (LV), left atrium (LA) and free wall of right ventricle (RV-FW GLS). We identified patients with subclinical disfunction expressed by an impaired GWE , and studied its determinants by lineal regression. Results 110 patients, 78.2% male, median age 53.3 (51.2-55.4) were included. Time from diagnosis was 20.5 (18.6-22.3) years. Myocardial work strain analysis showed an impaired GWE: 91.9% (90.9-92.9);p<0.001) and a GW index of 1840.8 mmHg%(1758.7-1922.9):p<0.001. The rest of deformation parameters laid into normal range: LV GLS was -19.5% (-19.0- -20.0) GLS dispersion 55.1 (50.1-60.1), LA GLS (reservoir) 32.8% (31.2-34.5), and RV free wall GLS -22.3% (-21.4 - -23.2). By univariate analysis, determinants of impaired GWE were age, Score2 risk, time from HIV diagnosis, QRS Interval duration, long QTc Interval, LV ejection fraction (LVEF),diastolic disfunction by doppler tissue imaging, CD4 count nadir, initial and maximun viral load, and exposure to didanosine treatment. After adjustment by cardiovascular risk and diastolic function (Ea velocity by tissue Doppler) , GWE impaired depended on duration of infection (Beta 0.3;95%CI:0.04-0.56;p=0.023), initial viral load (Beta -1.1;95%CI:-2.1- -0.02;p=0.046) and exposure to stavudine (Beta -6.3;95%IC: -11.5- -1.1;p=0.019). Conclusions Subclinical myocardial disfunction is prevalent in long standing HIV infection. Global work efficiency is a very sensitive parameter for detection, even in patients with normal GLS values, and it was related to duration of infection, initial viral load, and exposure to stavudine in our patients.Determinants of Global Work Efficiency

Depletion of Mitochondrial DNA in Differentiated Retinal Pigment Epithelial Cells

We investigated the effects of treating differentiated retinal pigment epithelial (RPE) cells with didanosine (ddI), which is associated with retinopathy in individuals with HIV/AIDS. We hypothesized that such treatment would cause depletion of mitochondrial DNA and provide insight into the consequences of degradation of RPE mitochondrial function in aging and disease. Treatment of differentiated ARPE-19 or human primary RPE cells with 200 µM ddI for 6–24 days was not cytotoxic but caused up to 60% depletion of mitochondrial DNA, and a similar reduction in mitochondrial membrane potential and NDUFA9 protein abundance. Mitochondrial DNA-depleted RPE cells demonstrated enhanced aerobic glycolysis by extracellular flux analysis, increased AMP kinase activation, reduced mTOR activity, and increased resistance to cell death in response to treatment with the oxidant, sodium iodate. We conclude that ddI-mediated mitochondrial DNA depletion promotes a glycolytic shift in differentiated RPE cells and enhances resistance to oxidative damage. Our use of ddI treatment to induce progressive depletion of mitochondrial DNA in differentiated human RPE cells should be widely applicable for other studies aimed at understanding RPE mitochondrial dysfunction in aging and disease.

Non-cirrhotic Portal Hypertension Associated with Didanosine and Streptococcus agalactiae Infection: A Case Report

Non-Cirrhotic Portal Hypertension (NCPH) is a rare but potentially fatal liver disorder described in patients treated with anti-retroviral therapy for Human Immunodeficiency Virus (HIV). In particular, the most important predisposing factor to its development has been identified as prolonged exposure to Didanosine (ddI). The clinical entity of NCPH is characterized by an increase in portal pressure due to pre- or intra-hepatic causes, in absence of liver cirrhosis. However, the exact pathogenesis remains poorly understood, and due to its rarity, the diagnosis is often delayed. We herein report a case in which ddI administration, with concomitant spontaneous bacterial peritonitis by Streptococcus agalactiae, has induced NCPH in a HIV male patient. NPCH should be suspected when HIV patient with an history of ddI treatment presents liver decompensation.

Short Communication: In Vitro Accumulation of Drug Resistance Mutations in Chimeric Infectious Clones Containing Subtype B or C Reverse Transcriptase and Selected with Tenofovir or Didanosine.

Highly active antiretroviral therapy (HAART) contributed to the improvement in the life expectancy of HIV-infected patients. However, the emergence of drug-resistant mutations (DRM) is a major viral factor impacting therapeutic failure. Differences in DRM can occur among HIV-1 subtypes. We evaluate the kinetics of the selection of resistance mutations in vitro analyzing two chimeric clones that contain the reverse transcriptases of subtypes B or C (RTB' and RTC') in cells treated with increasing concentrations of tenofovir disoproxil fumarate (TDF) and didanosine (ddI). The mutation K65R is selected more quickly in RTC' than in RTB' viruses with TDF and ddI, and additional mutations (positions 45, 62, and 68) were selected after K65R fixation. Other primary mutations (M184V and Q151M) were selected with ddI treatment in conjunction with K65R only in RTC' viruses. Both patterns, M184V+K65R and Q151M+K65R, have a significant impact on NRTI resistance. Our data suggest that selection of TDF and ddI DRMs can occur earlier in subtype C HIV in patients when compared to subtype B.

Flexible Marginal Structural Models for Estimating the Cumulative Effect of a Time-Dependent Treatment on the Hazard: Reassessing the Cardiovascular Risks of Didanosine Treatment in the Swiss HIV Cohort Study

The association between antiretroviral treatment and cardiovascular disease (CVD) risk in HIV-positive persons has been the subject of much debate since the Data collection on Adverse events of Anti-HIV Drugs (D:A:D) study reported that recent use of two antiretroviral drugs, abacavir (ABC) and didanosine (DDI), was associated with increased risk. We focus on the potential impact of DDI use, as this drug has not been as studied intensively as ABC. We propose a flexible marginal structural Cox model with weighted cumulative exposure modeling (Cox WCE MSM) to address two key challenges encountered when using observational longitudinal data to assess the adverse effects of medication: (1) the need to model the cumulative effect of a time-dependent treatment and (2) the need to control for time-dependent confounders that also act as mediators of the effect of past treatment. Simulations confirm that the Cox WCE MSM yields accurate estimates of the causal treatment effect given complex exposure effects and time-dependent confounding. We then use the new flexible Cox WCE MSM to assess the association between DDI use and CVD risk in the Swiss HIV Cohort Study. In contrast to the nonsignificant results obtained with conventional parametric Cox MSMs, our new Cox WCE MSM identifies a significant short-term risk increase due to DDI use in the previous year. Supplementary materials for this article are available online.

HIV‐associated idiopathic non‐cirrhotic portal hypertension is an underdiagnosed disorder: results of a large cohort study

Purpose of the studyIdiopathic non‐cirrhotic portal hypertension (INCPH) has been reported increasingly in patients with chronic HIV infection. However, several aspects of this disorder remain to be elucidated. The aim of our study was to evaluate the prevalence and risk factors of HIV associated INCPH.MethodsAll adult HIV patients attending the outpatient clinic between February and September 2011 underwent sonographical spleen size determination and assessment of portosystemic collaterals. Patients with splenomegaly underwent an extensive ultrasound examination. Gastroscopy was performed when additional signs of portal hypertension or collaterals were observed. All children with HIV infection underwent extensive ultrasound examination. INCPH was diagnosed according to the general definition. Differences between INCPH cases (group 1) and HIV patients treated with didanosine (ddI) without portal hypertension (group 2) were assessed at HIV diagnosis, start of ddI and INCPH diagnosis.Summary of resultsFour out of 1010 screened adult HIV patients were diagnosed with INCPH (prevalence of 4‰). Hundred of the 1010 screened patients were treated with ddI. All INCPH patients were treated with ddI, representing an INCPH prevalence of 4% in patients exposed to ddI. In The Netherlands, 7000 patients were treated with ddI and only 17 are diagnosed with INCPH, suggesting underdiagnosis in 260 patients. No differences in clinical characteristics predictive for the development of INCPH could be demonstrated between group 1 and group 2 at HIV infection or start of ddI treatment. INCPH patients were treated longer with ddI [86 vs. 51 months, p<0.01] and concomitant treatment with ddI and stavudine [21 vs. 4 months, p<0.01]. Corrected for age and duration of follow‐up of HIV, active protein c [0.64 vs. 1.13, p<0.01] and active protein s [0.67 vs. 1.01, p<0.01] levels were lower in the INCPH group. None of the 38 children with HIV infection were diagnosed with INCPH. None of these children were ever treated with ddI.ConclusionsIn our study HIV‐associated INCPH only occurred in patients exposed to ddI. Awareness for this disorder is warranted considering the suggested underdiagnosis based on these study results. Risk factors are long term treatment with ddI and concomitant treatment with stavudine and screening for signs of portal hypertension in this subgroup may be recommended. A possible pathophysiological role for thrombophilia remains to be elucidated. image

Prevalence and Risk Factors for Abnormal Liver Stiffness in HIV-infected Patients without Viral Hepatitis Coinfection: Role of Didanosine

Unexpected cases of severe liver disease in HIV-infected patients have been reported and an association with didanosine (ddI) has been suggested. Transient elastography (TE) might detect patients harbouring such a condition. Our objective was to search for the presence of abnormal liver stiffness (LS) in a cohort of HIV-infected patients without HBV or HCV coinfection and to assess the related factors. A cross-sectional prospective study was conducted. LS was assessed by TE in 258 HIV-infected patients without HBV or HCV coinfection and with no evidence of acute hepatotoxicity or other origins of liver disease. LS values > or =7.2 kPa were considered abnormal. Multivariate analyses were performed to identify factors associated with abnormal LS. Abnormal LS was observed in 29 (11.2%) patients. A total of 18 (16.4%) patients previously treated with ddI and 11 (7.4%) of those who never received ddI had LS values > or =7.2 kPa (P=0.02). The prevalence of abnormal LS was higher in patients previously treated with abacavir than in those who had never received abacavir (15 [21.7%] versus 14 [7.4%]; P=0.001). After multivariate analyses, age (adjusted odds ratio [AOR] 1.05, 95% confidence interval [CI] 1.002-1.1; P=0.004) alcohol intake >50 g/day (AOR 7.2, 95% CI 2.6-19.7; P<0.0001), CD4(+) T-cell count <200 cells/ml (AOR 3.4, 95% CI 1.06-11.007; P=0.03), time on ddI treatment (AOR 1.31, 95% CI 1.12-1.52; P=0.001) and previous abacavir exposure (AOR 3.01, 95% CI 1.18-7.67; P=0.02) were independently associated with abnormal LS. The prevalence of abnormal LS in HIV-infected patients without HBV or HCV coinfection is substantial. Long-term exposure to ddI is a major cause of liver damage in these patients.

Lipoatrophy of the Footpad in HIV-Treated Patients Is Associated With Increased PAI-1

To describe lipoatrophy of the plantar pedis fat pads in human immunodeficiency virus (HIV) patients with or without long-term antiretroviral therapy (ART); to compare the characteristics of ART patients with and without plantar pedis lipoatrophy; and to examine the effects of HIV and metabolic/cardiovascular risk parameters and treatment history on plantar pedis lipoatrophy. Participants included 134 patients who started protease inhibitors in antiretroviral therapy (ART) in 1996 and 49 treatment-naive patients, recruited in 2004. Participants were examined and graded for lipoatrophy of five body compartments including the plantar fat pads. Baseline HIV- and ART-related factors were documented together with follow-up metabolic/ cardiovascular risk parameters. Plantar pedis lipoatrophy occurred more often among ART patients (60%) than among treatment-naive patients (12%; p < .001). ART patients with plantar lipoatrophy were older, had higher plasminogen activator inhibitor 1 (PAI-1) values, a higher prevalence of lipoatrophy in other body compartments, and longer stavudine and didanosine treatment history as compared to patients without plantar lipoatrophy. Multiple logistic regression modeling revealed that among the metabolic/cardiovascular parameters, increased PAI-1 was strongly and positively associated with plantar lipoatrophy. Among the treatment history parameters, didanosine was the strongest independent predictor for plantar lipoatrophy. Increased PAI-1 was not associated to lipoatrophy in any other location. Plantar lipoatrophy is common among patients on long-term ART and, though often overlooked, may cause significant discomfort. The association to PAI-1, a well-known marker of increased cardiovascular risk, is intriguing and places further focus on the need for an active approach to evaluating and lowering cardiovascular risk factors in long-term HIV treatment.

CXCR3 activation by lentivirus infection suppresses neuronal autophagy: neuroprotective effects of antiretroviral therapy

Previous studies have implicated CXCL12 in the neuropathogenesis of HIV infection. Proteolysis of CXCL12 generates a neurotoxic molecule, CXCL12(5-67), which engages and activates CXCR3, in addition to exhibiting increased expression in the brains of patients with HIV-associated dementia (HAD). Herein, we investigated CXCR3-mediated neuronal injury, particularly, its contribution to autophagy suppression and the concomitant effects of antiretroviral therapy using human brain samples and models of HIV neuropathogenesis. Neurons in the brains of HAD patients and feline immunodeficiency virus (FIV)-infected animals, as well as cultured human neurons, expressed CXCR3, which was modulated in a ligand-specific manner. Exposure of human neurons to CXCL12(5-67) caused a reduction in the autophagy-associated molecule LC3 (P<0.05) and neuronal survival (P<0.05), which recapitulated findings in FIV- and HIV-infected brains (P<0.05). Oral didanosine (ddI) treatment of FIV-infected animals reduced neurobehavioral abnormalities in conjunction with diminished plasma viral load (P<0.05). F4/80 transcript abundance and CXCL12(5-67) immunoreactivity were reduced with restored neuronal LC3 expression in the brains of FIV-infected animals after ddI treatment (P<0.05). ddI treatment also prevented microglial activation and depletion of synaptic proteins in the cortex of FIV-infected animals (P<0.05). These findings indicate that the beneficial effects of ddI might be a consequence of a reduced systemic viral burden and concurrent leukocyte activation, leading to diminished neuroinflammation with preservation of neuronal autophagy by regulating CXCR3 activation.

Effect of Hydroxyurea and Dideoxyinosine on Intracellular 3′-Deoxyadenosine-5′-triphosphate Concentrations in HIV-Infected Patients

Hydroxyurea (HU) significantly enhances the antiretroviral effects of the adenosine analog reverse transcriptase inhibitor dideoxyinosine (ddI). This is believed to be due to a reduction in intracellular de-oxyadenosine triphosphate (dATP) concentrations resulting from HU-mediated inhibition of ribonucleotide reductase (RnR). The effect of combined HU-ddI treatment on intracellular dATP pools in vivo has not been examined. We measured intracellular dATP concentrations in peripheral blood mononuclear cells (PBMCs) from 69 HIV-infected patients receiving 1000 or 1500 mg HU daily for 14 days, 200 mg ddI twice daily for 14 days, or a combination of the two drugs. Median intracellular dATP concentrations decreased from base-line to day 14 by 46% in the ddI + 1000 mg HU arm and by 62% in the ddI + 1500 mg HU arm. When compared to the HU monotherapy arms, these changes proved statistically significant (p = 0.018; stratified Wilcoxon rank-sum test). These findings support reduced intracellular dATP as the mechanism of ddI-HU synergistic activity, and indicate that changes in intracellular nucleotides contribute to HU activity and toxicity in patients. Since a significant reduction in dATP was measurable only when ddI was combined with HU, the antiretroviral activity of ddI may be more complex than previously assumed.

Improved Interpretation of Genotypic Changes in the HIV‐1 Reverse Transcriptase Coding Region That Determine the Virological Response to Didanosine

Consensus on the interpretation of mutations in the human immunodeficiency virus (HIV)-1 reverse transcriptase (RT) gene that predict the response to didanosine treatment is needed. Baseline HIV-1 RT genotypes and 12-week virological outcomes for patients undergoing didanosine-containing salvage regimens were extracted from prospective studies. Existing didanosine genotypic-resistance interpretation rules were validated in the entire-patient data set. Mutations were given weighted positive or negative scores according to their coefficient of correlation with virological response in a derivation set. The score resulting from the algebraic sum of the mutations was then validated in an independent data set. A total of 485 patients were analyzed. The didanosine-resistance scores derived from the Jaguar and Gesca studies predicted virological outcome. The best correlation with response was found with the derived score (M41L x 2) + E44D/A/G + T69D/S/N/A + (L210W x 2) + T215Y or revertants + L228H/R - D123E/N/G/S, by use of which viruses were categorized as being susceptible (score < or =0), as having intermediate resistance (1-3), and as being resistant (> or =4) to didanosine. In the validation set, the adjusted mean difference in 12-week virological response was +0.34 log(10) copies/mL (95% confidence interval, +0.11 to +0.57; P=.004) per higher resistance category. Correlation with virological response constantly outperformed that obtained with the previous interpretation. The improved genotypic-resistance interpretation score can be applied to better guide the use of didanosine in treatment-experienced individuals.

Presence of M184I/V in minor HIV‐1 populations of patients with lamivudine and/or didanosine treatment failure

The aim of the study was to investigate the presence of M184I/V in minor HIV-1 populations of patients who failed lamivudine (3TC) and/or didanosine (ddI) treatment. Fourteen 3TC-experienced patients who, after switching therapy to a ddI regimen, had a new failure without M184I/V in the major viral population were included in the study. Ninety plasma samples were analysed by direct sequencing and selective real-time polymerase chain reaction (SPCR), which detects GTG/GTA and ATA mutants down to 1 and 0.2% of the population, respectively. In five samples, SPCR detected resistant virus when direct sequencing detected wild-type M184. In patients with mixed viral populations at sequencing, the median proportion of mutants detected by SPCR was 30%. SPCRGTG reactivity dominated, while SPCRATA reactivity only was uncommon. M184I/V disappeared in patients in whom 3TC was stopped but ddI continued. Ten patients with ddI failure had no M184I/V. Minor HIV-1 strains may harbour M184I/V in patients failing ddI therapy, despite direct sequencing showing wild-type virus. Although M184I/V may reduce the genetic barrier of ddI for mutations such as K65R and L74V, the lack of re-emergence of M184I/V in the minor quasispecies of most patients who failed ddI suggests that M184I/V was not a preferred route to ddI resistance in our patient population.

Didanosine causes sensory neuropathy in an HIV/AIDS animal model: impaired mitochondrial and neurotrophic factor gene expression

Antiretroviral toxic neuropathy (ATN) has become a common peripheral neuropathy among HIV/AIDS patients, for which the underlying pathogenesis is uncertain. Indeed, no models exist for ATN that assess the interaction between retroviral infection and antiretroviral therapy. Herein, we developed ex vivo and in vivo models of ATN induced by didanosine (ddI) following infection by the lentivirus, feline immunodeficiency virus (FIV), permitting us to address the working hypothesis that ddI mediates ATN through mitochondrial injury in neurons. We investigated neuronal morphology, neurobehavioural testing, viral load, mitochondrial and neurotrophic factor gene expression after ddI treatment of FIV-infected and uninfected animals or dorsal root ganglia (DRG) cultures. ddI caused concentration-dependent neuronal injury in cultured feline DRGs (P < 0.05), together with reduced viral replication and diminished expression of mitochondrial cytochrome C oxidase subunit I gene (mtCOX I) and the neurotrophin, brain-derived neurotrophic factor (BDNF). Indeed, BDNF treatment reversed neuronal injury caused by FIV infection in the presence or absence of ddI exposure (P < 0.05). In vivo FIV infection revealed delays in withdrawal latency to a noxious stimulus, which were exacerbated by ddI treatment. Epidermal density of nerve endings was reduced after FIV infection (P < 0.05), especially with ddI treatment. Although viral replication in blood was suppressed in ddI-treated animals (P < 0.05), ddI had a limited effect on viral abundance in DRGs of the same animals. ddI decreased mtCOX I expression in DRG neurons of FIV-infected animals (P < 0.05). BDNF expression was downregulated by ddI in DRG Schwann cells following FIV infection. Thus, ddI treatment during FIV infection resulted in additive pathogenic effects contributing to the development of ATN, which was associated with mitochondrial injury on neurons and reduced BDNF production by Schwann cells in DRGs, highlighting the convergent pathogenic effects that antiretroviral drugs might have in patients with HIV infection.

Prevalence of Toxoplasma Encephalitis in AIDS Patients Treated with Didanosine Hospitalised in a French Infectious Service

In a previous work, we have showed in mice infected with an avirulent strain of Toxoplasma gondii and receiving a didanosine treatment, an important decrease of brain cysts. It is why, the purpose of this study was to investigate the effect of didanosine treatment on AIDS patients having developed Toxoplasma encephalitis. 60 patient reports were analyzed: 22 patients (group 1) did not received didanosine in their antiretroviral treatment and 38 (group 2) were treated with didanosine. The results showed that an antiretroviral therapy was prescribed for 93% of patients, 50% of them received only zidovudine and protease inhibitors were prescribed for 37%. The regimens given most frequently were those including zidovudine plus lamivudine or zidovudine plus indinavir. Among the group 1, 18% have had a relapse of Toxoplasma encephalitis. In the group 2, 37% of the patients suffered from one episode of TE while 16% have had two TE after the pause in their didanosine treatment, the maximum occurring between 4 and 24 months after the pause of didanosine. This study showed that didanosine seems to have an effect on cerebral cysts. Also, this work made a synthesis about the different treatment used in AIDS patients and the new molecules yet in development against T. gondii.

Gynaecomastia in HIV-Infected Men on Highly Active Antiretroviral Therapy: Association with Efavirenz and Didanosine Treatment

Gynaecomastia has been described in HIV-infected men undergoing highly active antiretroviral therapy (HAART). However, there are insufficient data on the relationship between gynaecomastia and any specific antiretroviral drug and hormone abnormality. To assess the frequency of gynaecomastia in HIV-infected men receiving HAART and its association with antiretroviral drugs and hormone abnormalities. We carried out a prospective study of 1304 HIV-infected men undergoing HAART. In addition, we included a case (with gynaecomastia)-control (without gynaecomastia) analysis in the second part of this study. Cases and controls were matched according to age, HIV infection CDC clinical category, HCV infection, the date of study and the physician responsible for the patient. Patients bearing known causes of gynaecomastia were excluded. We analysed epidemiological, clinical, haematological and immunological characteristics and the use and duration of the antiretroviral therapy. In 13 cases and 13 controls a sexual hormone profile was carried out. A total of 30 (2.3%) HIV-infected men presented with gynaecomastia of unexplained cause. In 22 (73%) of these individuals, gynaecomastia completely resolved after a median time of 9 months (range: 5-22 months). The percentage of individuals who were receiving efavirenz and didanosine at the time of the study was higher among patients with gynaecomastia [57% vs 17% (P=0.004) and 50% vs 13% (P=0.003), respectively]. Plasma total testosterone, free testosterone index and bioavailable testosterone levels were lower in patients with gynaecomastia, whereas plasma free testosterone levels were not significantly different in either population. Gynaecomastia is not uncommon in HIV-infected men undergoing HAART and it is usually transient. Efavirenz and didanosine treatment are associated with the emergence of gynaecomastia. An underlying hypoandrogenism seems to contribute to the emergence of this disorder in these patients.

Determination of ddATP Levels in Human Immunodeficiency Virus-Infected Patients Treated with Dideoxyinosine

Clinical failures of the highly active antiretroviral therapy could result from inefficient intracellular concentrations of antiviral drugs. The determination of drug contents in target cells of each patient would be useful in clinical investigations and trials. The purpose of this work was to quantify the intracellular concentration of ddATP, the active metabolite of dideoxyinosine (ddI), in peripheral blood mononuclear cells (PBMCs) of human immunodeficiency virus (HIV)-infected patients treated with ddI. We have raised antibodies against ddA-citrate, a stable isostere of ddATP selected on the basis of its structural and electronic analogies with ddATP. The anti-ddA-citrate antibodies recognized ddATP and ddA with nanomolar affinities and cross-reacted neither with any of the nucleotide reverse transcriptase inhibitors used in HIV therapy nor with their phosphorylated metabolites. The three phosphorylated metabolites of ddI (ddAMP, ddADP, and ddATP) were purified by anion exchange chromatography and the amount of each metabolite was determined by radioimmunoassay with or without prior phosphatase treatment. The intracellular levels of the three ddI metabolites were measured both in an in vitro model and in PBMCs of HIV-infected patients under ddI treatment. The possibility to measure intracellular levels of ddATP from small blood samples of HIV-infected patients treated with ddI could be exploited to develop individual therapeutic monitoring.

Hydroxyurea and didanosine long-term treatment prevents HIV breakthrough and normalizes immune parameters.

Hydroxyurea and didanosine treatment suppressed HIV replication for more than 2 years, in the absence of viral breakthrough, in chronically infected patients. The profile of viral load reduction was unusual for a two-drug combination, since a continuous gradual decrease in viremia persisted despite residual viral replication. The increase in CD4+ T cell counts was not robust. However, unlike those of patients treated by other therapies, CD4+ T lymphocytes were functionally competent against HIV, mediating a vigorous HIV-specific helper T cell response in half of these patients. In addition, the percentages of naive CD4+ and CD8+ T lymphocytes were not different from those in uninfected individuals. These results demonstrate that prolonged antiretroviral therapy with a simple, well-tolerated combination of two affordable drugs can lead to sustained control of HIV, normalization of immune parameters, and specific anti-HIV immune response.

Selective inhibition of syncytium-inducing and nonsyncytium-inducing HIV-1 variants in individuals receiving didanosine or zidovudine, respectively.

By studying changes in the clonal composition of HIV-1 populations during the first weeks of zidovudine (ZDV) treatment before the development of ZDV resistance-conferring mutations, we demonstrated previously a selective inhibition of nonsyncytium-inducing (NSI) HIV-1, even when present as coexisting population in individuals also harboring syncytium-inducing (SI) HIV-1. In this study, we observed the opposite in individuals receiving didanosine (ddI) treatment. In these individuals (n = 7) a median -0.98 log change (range -1.55-0.08) in infectious cellular SI load was observed, whereas the coexisting NSI load was only minimally affected (median -0.15 log, range -1.27-0.50; P = 0.03). The virus phenotype-dependent treatment responses were independent of the clonal composition of HIV-1 populations at baseline. Individuals treated with a combination of ZDV and ddI revealed an equal decline of both NSI and SI infectious cellular load (n = 4; NSI: median -1.55 log, range -2.19 to -1.45; SI: median -1.47 log, range -1.81 to -0.86; P = 0.56). To test the hypothesis that the previously reported optimal activation of ZDV and ddI in activated and resting T cells, respectively, in combination with the differential T cell tropism of NSI and SI HIV-1 is the basis for the observed virus phenotype specific efficacy of nucleoside analogs, we studied the effect of treatment with a protease inhibitor that does not require intracellular activation. Individuals receiving ritonavir (n = 4) indeed showed equal declines in NSI and SI infectious cellular load (NSI: median -2.37 log, range -2.59 to -2.16; SI: median -2.82 log, range -3.14 to -2.50; P = 0.25). Our data suggest HIV-1 phenotype as an additional parameter in the design of optimal treatment regimens.

2′,3′-Dideoxyinosine Inhibits the Humoral Immune Response in Female B6C3F1 Mice by Targeting the B Lymphocyte

2′,3′-Dideoxyinosine (ddI) is a purine nucleoside analog currently being used for the treatment of HIV-positive individuals and patients with AIDS. Preliminary immunotoxicity studies have shown that a consequence of ddI treatment in female B6C3F1 mice is the inhibition of the humoral immune response. This effect was dose dependent in a range of 100 to 1000 mg/kg with a no observed adverse effect level of less than 100 mg/kg for a 28-day treatment period. These studies were undertaken to investigate the immune cell target of ddI and to determine the mechanism of this toxicity. B6C3F1 mice were treated with 1000 mg/kg/day by oral gavage for 28 days. The B lymphocyte was identified as the cellular target of ddI through separation–reconstitution experiments of the adherent and nonadherent cell populations and of the T and B lymphocyte populations. These studies revealed a deficit in the ability of the nonadherent cells from ddI-treated mice to mount a normal antibody response to sRBC. A further separation of the nonadherent cells into T and B cells revealed a decreased ability of ddI-treated B cells to develop specific humoral immunity. Additional studies were undertaken to determine the mechanism by which ddI is affecting the B cell. Surface marker analysis of splenocytes revealed no difference in the cell populations between vehicle- and ddI-treated mice. B cell proliferation was also unaffected as shown by incubation with either a polyclonal stimulator, lipopolysaccharide, or anti-IgM plus IL-4. These results indicate that the primary cellular target of ddI is the B lymphocyte.

The effect on human immunodeficiency virus type 1 RNA levels in cerebrospinal fluid after initiation of zidovudine or didanosine.

Human immunodeficiency virus type 1 (HIV-1) RNA, neopterin, and beta2-microglobulin levels were analyzed in cerebrospinal fluid (CSF) and serum before and 3-13 months after initiation of antiretroviral monotherapy in 16 HIV-1-infected persons. Twenty-one treatment periods, 13 after initiation of zidovudine and 8 after initiation of didanosine, were studied. During zidovudine treatment, CSF HIV RNA levels decreased by a mean of 1.05 log10 (-91%, P < .01), and CSF neopterin and beta2-microglobulin levels by 57% and 33%, respectively (P < .01). No reduction was seen during didanosine treatment in CSF HIV RNA (+0.13 log10, not significant), CSF neopterin, or beta2-microglobulin levels. Changes in CSF HIV RNA levels correlated with changes in CSF neopterin and beta2-microglobulin (r(s) = .81 and .83, respectively, P < .001). The decrease in HIV RNA was significantly larger in CSF than in serum following zidovudine treatment (P < .01). These data demonstrate that zidovudine is a potent reducer of central nervous system virus load, which may be important for long-term neuroprotection.