Neuromuscular function in HIV infection: analysis of a placebo-controlled combination antiretroviral trial. AIDS Clinical Group 175/801 Study Team

Update of HIV-Associated Sensory Neuropathies

PURPOSE OF REVIEW

HIV-sensory neuropathy (HIV-SN) remains a common complication of HIV infection and may be associated with significant morbidity due to neuropathic pain. The overall purpose of this review is to discuss trends in the changing epidemiology in HIV-SN, new data regarding the pathophysiology of the condition, and discuss approaches to management.

RECENT FINDINGS

While HIV-SN has been historically considered the most common neurological complication of HIV infection, improved accessibility to effective combination antiretroviral therapy (cART), use of less neurotoxic antiretroviral medication regimens, and trends towards earlier introduction of treatment have impacted the condition: overall incident HIV-SN is likely decreased compared to prior rates and patients afflicted by HIV-SN may more frequently have asymptomatic or subclinical disease. Traditional predictors of HIV-SN have also changed, as traditional indices of severe immune deficiency such as low CD4 count and high viral load no longer predict HIV-SN. Emerging evidence supports the contention that both peripheral and central mechanisms underlying the generation as well as persistence of neuropathic pain in HIV-SN exist. It is important to recognize that even mild neuropathic pain in this clinical population is associated with meaningful impairment in quality of life and function, which emphasizes the clinical importance of recognizing and treating the condition. The general approach to management of neuropathic pain in HIV-SN is the introduction of symptomatic analgesic therapy. There exist, however, few evidence-based analgesic options for HIV-SN based on available clinical data. Symptomatic treatment trials are increasingly recognized to have been potentially confounded by more robust placebo response than that observed in other neuropathic pain conditions. In the authors' experience, use of analgesic therapies with proven efficacy in other neuropathic pain conditions is appropriate, bearing in consideration potential pharmacokinetic interactions with the cART regimen. Combination analgesic regimens may also achieve meaningful analgesic responses, particularly when drugs with differing mechanisms of action are utilized. It is paramount that the patient is appropriately counseled regarding expectations and the anticipated benefit of analgesic therapy, as pain relief is often incomplete but clinically meaningful improvement in pain and function can be achieved.

Aging with HIV in the ART era

In the current era of therapy for human immunodeficiency virus (HIV), life expectancy for persons living with HIV (PLWH) approaches that of the general population. This newly prolonged survival among PLWH is associated with an increased prevalence of comorbidities due to the inflammation, immune activation and immune senescence associated with HIV infection. Higher prevalence of tobacco and alcohol use, co-infection with viral hepatitis and traditional cardiovascular risk factors such as hypertension and hyperlipidemia contribute as well. In this review, we hope to describe the current comorbidities occurring among PLWH and bring increased awareness for conditions that may otherwise not be considered given the younger age at time of presentation.

Toxic myopathies

Muscle tissue is highly sensitive to many substances. Early recognition of toxic myopathies is important, because they potentially are reversible on removal of the offending drug or toxin, with greater likelihood of complete resolution the sooner this is achieved. Clinical features range from mild muscle pain and cramps to severe weakness with rhabdomyolysis, renal failure, and even death. The pathogenic bases can be multifactorial. This article reviews some of the common toxic myopathies and their clinical presentation, histopathologic features, and possible underlying cellular mechanisms.

Screening for HIV-associated peripheral neuropathy in resource-limited settings

INTRODUCTION

Peripheral neuropathy is the most common neurological complication of human immunodeficiency virus (HIV) infection but is widely under-diagnosed in resource-limited settings. We investigated the utility of screening tools administered by nonphysician healthcare workers (HCW) and quantitative sensory testing (QST) administered by trained individuals for identification of moderate/severe neuropathy.

METHODS

We enrolled 240 HIV-infected outpatients using 2-stage cluster randomized sampling. HCWs administered the several screening tools. Trained study staff performed QST. Tools were validated against a clinical diagnosis of neuropathy.

RESULTS

Participants were 65% women, mean age 36.4 years, median CD4 324 cells/μL. A total of 65% were taking antiretrovirals, and 18% had moderate/severe neuropathy. The screening tests were 76% sensitive in diagnosing moderate/severe neuropathy with negative predictive values of 84-92%. QST was less sensitive but more specific.

CONCLUSIONS

Screening tests administered by HCW have excellent negative predictive values and are promising tools for scale-up in resource-limited settings. QST shows promise for research use.

Toxicity associated with stavudine dose reduction from 40 to 30 mg in first-line antiretroviral therapy

Background

To compare the incidence and timing of toxicity associated with the use of a reduced dose of stavudine from 40 to 30 mg in first-line antiretroviral therapy (ART) for HIV treatment and to investigate associated risk factors.

Methods

Multicohort study including 23 HIV programs in resource-limited countries. Adults enrolled between January 2005 and December 2009. Four-year rates of all-cause and stavudine-specific toxicity were estimated. Multilevel mixed-effect Poisson and accelerated failure models were used to investigate factors associated with toxicity and timing of diagnosis.

Findings

A total of 48,785 patients contributed 62,505 person-years of follow-up. Rate of all-cause toxicity was 7.80 (95%CI 7.59–8.03) per 100 person-years, but varied greatly across sites (range 0.41–21.76). Patients treated with stavudine 40 mg had higher rates of toxicity (adjusted rate ratio [aRR] 1.18, 95%CI 1.06–1.30 during the first year of ART; and 1.51, 95%CI 1.32–1.71 during the second year). Women, older age, initial advanced clinical stage, and low CD4 count were associated with increased toxicity rate ratios. Timing of lipodystrophy and peripheral neuropathy diagnosis were 12% and 13% shorter, respectively, in patients treated with stavudine 40 mg than in those receiving 30 mg stavudine dose (P = 0.03 and 0.07, respectively).

Insterpretation

Higher rates of drug-related toxicity were reported in patients receiving stavudine 40 mg compared with 30 mg, and the time to toxicity diagnosis was shorter in patients treated with the higher dose. Higher rates of toxicity were observed during the first two years of ART.

An obese body mass increases the adverse effects of HIV/AIDS on balance and gait

BACKGROUND

Balance and gait problems have been detected among patients with HIV/AIDS. The extent to which these problems are exacerbated by either frailty or obesity has not been examined. Objective The purpose of this study was to compare participants who differed in body mass and the presence or absence of HIV/AIDS.

DESIGN

This was a cross-sectional study.

METHODS

Quantitative measurements were obtained from 86 participants who were HIV-type 1 (HIV-1) seronegative and 121 participants who were seropositive divided into subgroups based on their body mass index (BMI <21, 21-29, or >29 kg/m(2)).

RESULTS

Participants who were seropositive were impaired relative to seronegative controls on several indices, including the limit of stability, sway amplitude and sway strategy, gait initiation time, and gait speed during a fast pace condition. Participants who were obese also exhibited impairments, which were evident during assessments of the limit of stability, nonpreferred leg stance time, sway strategy, normal and fast gait speed, fast gait initiation time, and 360-degree turn time. Importantly, the analysis revealed that participants with both attributes were more impaired than those with either or neither attribute: patients who were obese and seropositive were more impaired in fast gait initiation time and cadence, nonpreferred leg stance time, 360-degree turn time, and sway strategy scores. Limitations The validity of BMI as a measure of body mass can be challenged. In addition, the validity of chair rise time and 360-degree turn time as estimates of lower-extremity strength (force-generating capacity) can be argued.

CONCLUSIONS

The present findings have an obvious and unfortunate implication: as more patients who are HIV-1 seropositive join the seronegative community in becoming obese, the effects of obesity and their disease may summate and their risk for balance and gait problems may increase.

The Risk of Developing Peripheral Neuropathy Induced by Nucleoside Reverse Transcriptase Inhibitors Decreases over Time: Evidence from the Delta Trial

Background

Peripheral neuropathy (PN) in HIV-infected individuals is thought be due to a toxic effect on mitochondria induced by some nucleoside reverse transcriptase inhibitors (NRTI).

Methods

A time-to-event analysis was performed using data from the Delta trial to study the incidence of PN in HIV-infected individuals receiving zidovudine (AZT) alone or in combination with didanosine (ddI) or zalcitabine (ddC). In an on-treatment analysis, changes in the incidence of PN by duration of treatment were directly estimated using a flexible parametric survival model.

Results

A total of 3,195 patients (total follow-up 4,593 person-years) were included in the analysis. AZT+ddC was associated with a higher incidence of PN (6.2 cases/100 person-years) compared with AZT monotherapy (3.0 cases/100 person-years) and AZT+ddI (2.2 cases/100 person-years). The risk of PN peaked around day 90 following randomization (at 8.9 events/100 person-years in the AZT+ddC arm). PN was also associated with age at entry (hazard ratio (HR)=2.35 for those aged 35–44 years compared with <30) and current CD4+ T-cell count (HR=2.27 for CD4+ T-cell counts <150 cell/mm3 compared with >350).

Conclusion

Our findings challenge the common supposition that PN arises from cumulative exposure to NRTIs. We found that patients who developed PN tended to do so shortly after exposure to antiretroviral therapy. Therefore, our results support the hypothesis of a susceptibility in a subgroup of patients. These results will be of direct interest to those working in resource-limited countries where potentially neurotoxic dideoxynucleosides are still widely used.

[Mitochondrial cytopathies associated with HIV infection]

The tremendous progress achieved during the last few years with the use of highly active antiretroviral therapy in suppressing HIV replication together with improvements in immunity have been tempered by a growing number of new adverse effects. Mitochondrial toxicity is one aspect of these long-term toxicities of antiretroviral drugs, with the role of nucleoside analogs particularly underlined. Some cases of impaired mitochondrial function have been clearly identified, such as pancreatitis due to didanosine, neuropathy due to zalcitabine, myopathy due to zidovudine, and lactic acidosis due to stavudine. These mitochondrial toxicities can affect several organs, presenting different patterns of symptoms: from asymptomatic to states with few symptoms despite huge metabolic abnormalities whose prognosis is immediately life-threatening. Beyond the inhibition of DNA polymerase gamma using nucleoside analogs, responsible for decreasing mitochondrial DNA in certain targeted organs, it appears that several physiopathologic mechanisms interact to explain this observed toxicity, HIV itself plays a role, and the underlying genetic pool needs to be better identified. Such cases mean that, it is imperative to avoid cumulated toxicities caused by associated treatments. With serious cases, or persistent symptoms despite discontinuing the nucleoside analogs responsible for such toxicity, one must propose vitamins, mitochondrial co-factors, or anti-oxidants. However, the future lies in the use of potent, less toxic nucleoside analogs, and in developing compounds belonging to other classes of antiretrovirals.

Toxic Myopathies

Muscle tissue is highly sensitive to drugs and toxins because ot its high metabolic activity and potential sites for disruption of energy-producing pathways. Early recognition of toxic myopathies is important, as they potentially are reversible on removal of the offending toxin, with greater likelihood of complete resolution the sooner this is achieved. Clinical features range from mild muscle pain and cramps to severe weakness with rhabdomyolysis, renal failure, and even death. The pathogenic bases can be multifactorial. This article reviews drugs responsible for common types of toxic myopathy and their clinical and histopathologic features and illustrates possible underlying cellular mechanisms.

Modification of the incidence of drug-associated symmetrical peripheral neuropathy by host and disease factors in the HIV outpatient study cohort

BACKGROUND

We sought to identify factors associated with the clinical diagnosis of symmetrical peripheral neuropathy (SPN) during the era of highly active antiretroviral therapy (HAART) in a retrospective, longitudinal cohort analysis.

METHODS

Patients infected with human immunodeficiency virus type 1 were evaluated for clinical signs of SPN and its association with immunologic, virologic, clinical, and drug treatment factors by means of univariate and multivariate logistic regression analyses.

RESULTS

Of 2515 patients, 329 (13.1%) received a diagnosis of SPN. In the logistic regression analysis, statistically significant non-drug-based risk factors for SPN were age >40 years (adjusted odds ratio [aOR], 1.17), diabetes mellitus (aOR, 1.79), white race (aOR, 1.33), nadir CD4(+) T lymphocyte count <50 cells/mm(3) (aOR, 1.64), CD4(+) T lymphocyte count 50-199 cells/mm(3) (aOR, 1.40), and viral load >10,000 copies/mL at first measurement (aOR, 1.44). Although initial use of didanosine, stavudine (40 mg b.i.d.), nevirapine, or 4 protease inhibitors was associated with SPN (ORs for all 4 treatments, >1.41), the strength of association decreased with continued use of all medications studied.

CONCLUSION

Since HAART was introduced, the incidence of SPN has decreased. Host factors and signs of increased disease severity were associated with an increased risk of developing SPN during the initial period of exposure to drug therapy. Immunity improved and the risk of SPN decreased with continued use of HAART. Delaying the initiation of therapy may select those individuals who will be more likely to develop SPN, and earlier initiation of HAART may decrease the risk of developing this common problem, as well as increase the therapeutic effects and decrease the toxic effects of the drugs.

Complications Associated with Nrti Therapy: Update on Clinical Features and Possible Pathogenic Mechanisms

The availability of durable, effective antiretroviral therapy for HIV-infected patients has fundamentally altered the prognosis of this disease and has also increased awareness that long-term drug toxicities have the potential to cause significant morbidity and even mortality in this patient population. The long-term use of nucleoside analogue reverse transcriptase inhibitor (NRTI) drugs has been associated with a number of clinically relevant toxicities including hyperlactataemia and lactic acidosis, neuropathy, pancreatitis and, more recently, a syndrome of pathological loss of subcutaneous fat tissue (lipoatrophy). Importantly, the toxicity profile of each NRTI drug within this class is unique in terms of the overall risk of long-term complications, as well as the tissue specificity of its toxic effects. In this review, the clinical manifestations, risk factors and pathological basis for NRTI-associated toxicity syndromes are explored, with an emphasis on clinical assessment and management.

HIV-associated neuromuscular weakness syndrome

OBJECTIVE

To investigate progressive, severe neuromuscular weakness associated with lactic acidosis in some HIV-infected patients after exposure to nucleoside reverse transcriptase inhibitors (NRTI).

METHODS

HIV-associated neuromuscular weakness syndrome (HANWS) was retrospectively identified and classified based on the level of diagnostic certainty: possible (progressive weakness owing to neuromuscular disease), probable (progressive neuromuscular weakness with documented exclusion of confounding causes), or definite (progressive weakness and electrophysiological or pathological evidence of neuromuscular pathology).

RESULTS

Of 69 patients identified with HANWS, 27 had definite HANWS, 19 probable, and 23 possible. In 44 patients with documented follow-up, 16 required intubation and nine died. There was a marginal association between death and hyperlactatemia (P = 0.061). At onset of neurological symptoms, 68 were receiving antiretroviral therapy, including stavudine for 61 (89.7%). Serum lactate level was elevated (> 2.2 mmol/l) in 30/37 (81%), with a trend towards an association between hyperlactatemia and stavudine usage (P = 0.087). In 25, neurological symptoms occurred after antiretroviral therapy discontinuation (median, 14 days). Electrophysiological studies (n = 24) indicated sensorimotor neuropathy in 20 patients and myopathy in three. Nerve biopsy (n = 9) revealed axonal degeneration and inflammation in three, mixed axonal and demyelinating lesions in three, and primary axonal neuropathy in three. Of 15 muscle biopsies, three revealed inflammation and four mitochondrial abnormalities.

CONCLUSIONS

A severe neuromuscular weakness syndrome may occur in HIV-infected individuals. The association with hyperlactatemia and NRTI exposure supports mitochondrial toxicity as a pathogenesis. In some, the onset of neurological symptoms lagged significantly after discontinuation of antiretroviral therapy, suggesting that different etiological mechanisms may underlie these cases.

Risk modifiers for peripheral sensory neuropathy in HIV infection/AIDS

The objective of this study is to examine the risk factors associated with the development of sensory neuropathy in human immunodeficiency virus (HIV)-infected patients in 292 HIV+ patients recruited through a community-based sentinel survey. We determined the clinical and treatment factors associated with the presence of peripheral sensory neuropathy in HIV+ subjects at baseline examination, and at 1-year follow-up. Baseline examination was assessed with a logistic regression analysis controlling for age, education level, history of drug/alcohol use, and anti-retroviral treatment. The risk of developing new peripheral neuropathy at follow-up was determined using a Cox proportional hazard model analysis. At study entry, neuropathy (n=64) was associated with acquired immunodeficiency syndrome (AIDS), nucleoside analogue reverse transcriptase inhibitors (NRTI) (i.e. ddC), and history of alcohol abuse. After 1-year follow-up, the development of neuropathy was predicted by AIDS, age (older subjects), and NRTI use. These findings indicated that AIDS, age, alcohol abuse/dependence, and anti-retroviral medication use are important predictors of motor/sensory peripheral neuropathy in the HIV infection. The peripheral neurotoxic effect of anti-retroviral medication should be taken into account in the design of long-term therapies.

AIDS and AIDS-treatment neuropathies

AIDS and AIDS-treatment neuropathies are common in individuals infected with HIV. As patients live longer due to improved antiretroviral therapies, the impact of painful neuropathy on patients' lives may increase. Several antiretroviral medications are known to cause toxic neuropathy in patients with AIDS, but this may be outweighed by the beneficial effects of viral suppression. Current theories on the pathogenesis of AIDS neuropathies include mitochondrial toxicity secondary to gamma-DNA polymerase inhibition and subsequent abnormal mitochondrial DNA synthesis. Treatment of AIDS neuropathies is directed toward relief of symptoms; however, new evidence suggests that aggressive antiretroviral therapy may also be effective.

Aging and neuro-AIDS conditions and the changing spectrum of HIV-1-associated morbidity and mortality

Older individuals (>50 years of age) now comprise over 11% of patients with AIDS in the United States. This percentage is expected to continue to grow, due both to the improved longevity of patients prescribed highly active antiretroviral therapy (HAART) and to new infections among older individuals. This review focuses on the neuropsychiatric and neurological conditions that are most likely to be affected by advancing age-HIV-1-associated cognitive-motor disorder, peripheral neuropathy, progressive multifocal leukoencephalopathy, primary CNS lymphoma, and risk for cerebrovascular accident. Age associations with incidence of these disorders and with treatment foci are specified. Implications for future changes in management are discussed.

Mitochondrial Toxicity Associated with Nucleoside Reverse Transcriptase Inhibitor Therapy

Nucleoside reverse transcriptase inhibitors result in a wide range of toxic side effects. These include lactic acidosis syndrome, myopathy, cardiomyopathy, pancreatitis, peripheral neuropathy, and possibly lipodystrophy. Despite the seemingly diverse nature of these side effects, all of these toxicities may be mediated by a common pathophysiologic mechanism, namely, mitochondrial toxicity resulting from nucleoside reverse transcriptase inhibitor-induced inhibition of DNA polymerase g. This article reviews the relevant mitochondrial biology and mechanism underlying nucleoside reverse transcriptase inhibitor-induced mitochondrial toxicity. Clinical manifestations of this toxicity are reviewed followed by a discussion of clinical management.

AIDS and AIDS-treatment neuropathies

AIDS and AIDS-treatment neuropathies are common in individuals infected with HIV. As patients live longer due to improved antiretroviral therapies, the impact of painful neuropathy on patients' lives may increase. Several antiretroviral medications are known to cause toxic neuropathy in AIDS patients; but this may be outweighed by the beneficial effects of viral suppression. Current theories on the pathogenesis of AIDS neuropathies include mitochondrial toxicity secondary to gamma-DNA polymerase inhibition and subsequent abnormal mitochondrial DNA synthesis. Treatment of AIDS neuropathies is directed toward relief of symptoms, however, new evidence suggests that aggressive antiretroviral therapy may also be effective.

Mitochondrial toxicity and HIV therapy

Nucleoside reverse transcriptase inhibitors (NRTIs) remain the cornerstone of highly active antiretroviral therapy (HAART) combination regimens. However, it has been known for some time that these agents have the potential to cause varied side effects, many of which are thought to be due to their effects on mitochondria. Mitochondria, the key energy generating organelles in the cell, are unique in having their own DNA, a double stranded circular genome of about 16 000 bases. There is a separate enzyme present inside the cell that replicates mitochondrial DNA, polymerase gamma. NRTIs can affect the function of this enzyme and this may lead to depletion of mitochondrial DNA or qualitative changes. The study of inherited mitochondrial diseases has led to further understanding of the consequences of mutations or depletion in mitochondrial DNA. Key among these is the realisation that there may be substantial heteroplasmy among mitochondria within a given cell, and among cells in a particular tissue. The unpredictable nature of mitochondrial segregation during cellular replication makes it difficult to predict the likelihood of dysfunction in a given tissue. In addition, there is a threshold effect for the expression of mitochondrial dysfunction, both at the mitochondrial and cellular level. Various clinical and in vitro studies have suggested that NRTIs are associated with mitochondrial dysfunction in different tissues, although the weight of evidence is limited in many cases. The heterogeneity in the tissues affected by the different drugs raises interesting questions, and possible explanations include differential distribution or activation of these agents. This article reviews the major recognised toxicities associated with NRTI therapy and evidence for mitochondrial dysfunction in these complications. Data were identified through searching of online databases including Medline and Current Contents for relevant articles, along with abstracts and posters from recent conferences in the HIV and mitochondrial fields.

Peripheral neuropathy during stavudine-didanosine antiretroviral therapy

Peripheral neuropathy (PN) is among the most frequent side effects described with nucleoside reverse transcriptase inhibitors (NRTIs). We investigated the incidence, evolution and predictive factors of PN during stavudine (d4T)-didanosine (ddI) combination therapy in 65 HIV infected patients, previously treated with zidovudine and/or zalcitabine (ddC) for at least 3 months. A subset of 16 patients was referred for systematic electromyographic examination at weeks 0 and 24: six among the 16 exhibited nerve conduction abnormalities at day 0, probably related to previous ddC treatment in four of those and to HIV infection in the other two, with worsening of abnormalities in one patient at week 24. In total, seven of the 59 assessable patients (11.8%) exhibited grade 2-3 neuropathy, with a median time of occurrence of 17 weeks. Distal, symmetrical paraesthesias of the extremities were the first symptoms in all the patients; none had motor symptoms. In all the patients, PN resolved rapidly after stopping d4T. There were no statistically different parameters between the seven cases and the other 52 patients according to CD4 T cells, HIV RNA, Centers for Disease Control and Prevention (CDC) stage C or d4T daily dose. In our study, the d4T-ddI combination did not seem to increase the incidence of PN; risk factors for PN could not be identified, probably in part because of the low number of patients with PN.

Virologic and CD4 cell response to zidovudine or zidovudine and lamivudine following didanosine treatment of human immunodeficiency virus infection

To optimize nucleoside reverse transcriptase inhibitor (nRTI) antiretroviral therapy, 137 subjects who had been treated with didanosine monotherapy for more than 3 years in the AIDS Clinical Trials Group (ACTG) 175 study were randomized to zidovudine and didanosine (dual therapy) or zidovudine, didanosine, and lamivudine (triple therapy). Evaluation of early (8 week) change in HIV plasma RNA demonstrated that addition of lamivudine and zidovudine provided significantly greater virologic suppression compared to the addition of zidovudine alone (mean decrease of 1.27 vs. 0.74 log(10) copies/ml, n = 108, p = 0.007). Both dual and triple therapy provided significant long-term decreases (from study entry to mean at Weeks 40 and 48) in HIV plasma RNA: 0.62 and 0.86 log(10) copies/ml, respectively (n = 110). However, the difference between treatments was not significant (p = 0.16). At 48 weeks, 26% of subjects starting study treatment had <500 copies/ml of plasma HIV RNA. The CD4 count response was greater at 4 weeks for triple versus dual therapy: a mean increase of 51 vs. 12 CD4 cells/ml(3) (n = 126, p = 0.039). The difference at Weeks 40 and 48 was not significant (a 22 cell increase vs. a 1 cell decrease, n = 129, p = 0.41). Zidovudine and didanosine treatment, with or without lamivudine, was well tolerated and only 2 of 137 (1.5%) of study participants developed an AIDS-defining event over 48 weeks.

Neuropathy in HIV infection

Peripheral nerve complications in patients infected with HIV usually result from the virus itself, or are due to some of the antiretroviral drugs (zalcitabine, didanosine or stavudine). It may be difficult to distinguish between these two aetiologies on clinical or neurophysiological criteria. Since they are a significant cause of morbidity, a number of studies have looked at agents used for symptomatic control. More recently, there has been a focus on treatments that improve nerve function, including recombinant human nerve growth factor and the reduction of HIV viral load with antiretroviral drugs.

Genotoxic and functional consequences of transplacental zidovudine exposure in fetal monkey brain mitochondria

Mitochondrial toxicity was assessed in the brains of developing Erythrocebus patas monkey fetuses exposed in utero to the nucleoside analogue drug zidovudine (3'-azido-3'deoxythymidine or AZT). Pregnant E. patas monkeys were given 0 (n = 5), 10 (n = 3), and 40 (n = 3) mg of AZT/day, equivalent to 21 and 86% of the human daily dose, for the last half (about 10 weeks) of gestation. Mitochondria were isolated from fetal cerebrum and cerebellum at birth and mitochondrial morphology was examined in these tissues by transmission electron microscopy (TEM). Oxidative phosphorylation (OXPHOS) enzyme specific activities were measured spectrophotometrically. Mitochondrial DNA (mtDNA) integrity and quantity were determined by Southern blot and slot blot analysis. In the cerebral mitochondria, reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase (complex I) specific activity decreased by 25% in monkeys treated with 40 mg of AZT/day compared with unexposed monkeys (p > or = .05). At the same AZT dose in the cerebral mitochondria, succinate dehydrogenase (complex II) and cytochrome c reductase (complex IV)-specific activities showed dose-dependent increases (p > or = .05), compared with those in controls. In the cerebellum, no difference was seen in mitochondrial OXPHOS enzyme activities between unexposed and exposed fetuses. Furthermore, TEM demonstrated no difference in mitochondrial morphology in frontal cerebrum or cerebellum from unexposed and exposed fetuses, and all fetuses had similar amounts of mtDNA in both tissues. Cerebral mtDNA degradation was noted in the highest AZT dosage group, whereas mtDNA from cerebellum was uneffected. Thus, in fetal patas monkeys given a human equivalent daily dose of AZT during the last half of pregnancy, mitochondria in the fetal cerebrum appear to sustain moderate damage, while the fetal cerebellum mitochondria were not effected.

HIV-associated peripheral neuropathy: epidemiology, pathophysiology and treatment

Peripheral neuropathy is the most frequent neurological complication associated with human immunodeficiency virus type 1 (HIV) infection and advanced acquired immunodeficiency syndrome (AIDS). There are at least 6 patterns of HIV-associated peripheral neuropathy, although these diagnoses are often overlooked or misdiagnosed. Distal symmetrical polyneuropathy (DSP) is the most common form of peripheral neuropathy in HIV infection. DSP occurs mainly in patients with advanced immunosuppression and may also be secondary to the neurotoxicity of several antiretroviral agents. Treatment of painful DSP is primarily symptomatic, while pathogenesis-based therapies are under investigation. Reduction or discontinuation of neurotoxic agents should be considered if possible. Inflammatory demyelinating polyneuropathy (IDP) can present in an acute or chronic form. The acute form may occur at the time of primary HIV infection or seroconversion. Cerebrospinal fluid lymphocytic pleocytosis (10 to 50 cells/mm3) is helpful in the diagnosis of HIV-associated IDP. Treatment consists of immunomodulatory therapy. Progressive polyradiculopathy (PP) most commonly occurs in advanced immunosuppression and usually is caused by cytomegalovirus (CMV) infection. Rapidly progressive flaccid paraparesis, radiating pain and paresthesias, areflexia and sphincter dysfunction are the cardinal clinical features. Rapid diagnosis and treatment with anti-CMV therapy are necessary to prevent irreversible neurological deficits resulting from nerve root necrosis. Mononeuropathy multiplex (MM) that occurs in early HIV infection is characterised by self-limited sensory and motor deficits in the distribution of individual peripheral nerves. In advanced HIV infection, multiple nerves in two or more extremities or cranial nerves are affected. Treatment includes immunomodulation or anti-CMV therapy. Autonomic neuropathy may be caused by central or peripheral nervous system abnormalities. Treatment is supportive with correction of metabolic or toxic causes. Diffuse infiltrative lymphocytosis syndrome (DILS) presents as a Sjögren's-like disorder with CD8 T cell infiltration of multiple organs. Antiretroviral therapy and steroids may be effective treatments.

Neuromuscular Complications of HIV-1 Infection

Neuromuscular disorders are the most frequent neurologic complications that occur in patients with HIV infection. The distinction among the different forms of peripheral neuropathy (ie, distal symmetrical polyneuropathy, polyradiculopathy, mononeuritis multiplex) is crucial in determining their potential etiology and treatment. Distal symmetrical polyneuropathy is most common in HIV-infected patients with advanced immunosuppression and may also result from neurotoxicity of several antiretroviral agents. Myopathy may occur at any stage of HIV disease, and has also been described as a toxic side effect of zidovudine. This paper reviews current knowledge of pathogenesis, clinical manifestations, and treatment of HIV-associated neuromuscular disorders.