Hemochromatosis (HFE) gene mutations and peripheral neuropathy during antiretroviral therapy

Mechanisms underlying HIV-associated cognitive impairment and emerging therapies for its management

People living with HIV are affected by the chronic consequences of neurocognitive impairment (NCI) despite antiretroviral therapies that suppress viral replication, improve health and extend life. Furthermore, viral suppression does not eliminate the virus, and remaining infected cells may continue to produce viral proteins that trigger neurodegeneration. Comorbidities such as diabetes mellitus are likely to contribute substantially to CNS injury in people living with HIV, and some components of antiretroviral therapy exert undesirable side effects on the nervous system. No treatment for HIV-associated NCI has been approved by the European Medicines Agency or the US Food and Drug Administration. Historically, roadblocks to developing effective treatments have included a limited understanding of the pathophysiology of HIV-associated NCI and heterogeneity in its clinical manifestations. This heterogeneity might reflect multiple underlying causes that differ among individuals, rather than a single unifying neuropathogenesis. Despite these complexities, accelerating discoveries in HIV neuropathogenesis are yielding potentially druggable targets, including excessive immune activation, metabolic alterations culminating in mitochondrial dysfunction, dysregulation of metal ion homeostasis and lysosomal function, and microbiome alterations. In addition to drug treatments, we also highlight the importance of non-pharmacological interventions. By revisiting mechanisms implicated in NCI and potential interventions addressing these mechanisms, we hope to supply reasons for optimism in people living with HIV affected by NCI and their care providers.

Association of cytokine gene polymorphisms with peripheral neuropathy susceptibility in people living with HIV in Greece

Relatively little research has been done in recent years to understand what leads to the unceasingly high rates of HIV sensory neuropathy despite successful antiretroviral treatment. In vivo and in vitro studies demonstrate neuronal damage induced by HIV and increasingly identified ART neurotoxicity involving mitochondrial dysfunction and innate immune system activation in peripheral nerves, ultimately all pathways resulting in enhanced pro-inflammatory cytokine secretion. Furthermore, many infectious/autoimmune/malignant diseases are influenced by the production-profile of pro-inflammatory and anti-inflammatory cytokines, due to inter-individual allelic polymorphism within cytokine gene regulatory regions. Associations of cytokine gene polymorphisms are investigated with the aim of identifying potential genetic markers for susceptibility to HIV peripheral neuropathy including ART-dependent toxic neuropathy. One hundred seventy-one people living with HIV in Northern Greece, divided into two sub-groups according to the presence/absence of peripheral neuropathy, were studied over a 5-year period. Diagnosis was based on the Brief Peripheral Neuropathy Screening. Cytokine genotyping was performed by sequence-specific primer-polymerase chain reaction. Present study findings identify age as an important risk factor (p < 0.01) and support the idea that cytokine gene polymorphisms are at least involved in HIV peripheral-neuropathy pathogenesis. Specifically, carriers of IL1a-889/rs1800587 TT genotype and IL4-1098/rs2243250 GG genotype disclosed greater relative risk for developing HIV peripheral neuropathy (OR: 2.9 and 7.7 respectively), while conversely, carriers of IL2+166/rs2069763 TT genotype yielded lower probability (OR: 3.1), all however, with marginal statistical significance. The latter, if confirmed in a larger Greek population cohort, may offer in the future novel genetic markers to identify susceptibility, while it remains significant that further ethnicity-oriented studies continue to be conducted in a similar pursuit.

Drosophila model of anti-retroviral therapy induced peripheral neuropathy and nociceptive hypersensitivity

The success of antiretroviral therapy (ART) has improved the survival of HIV-infected patients significantly. However, significant numbers of patients on ART whose HIV disease is well controlled show peripheral sensory neuropathy (PSN), suggesting that ART may cause PSN. Although the nucleoside reverse transcriptase inhibitors (NRTIs), one of the vital components of ART, are thought to contribute to PSN, the mechanisms underlying the PSN induced by NRTIs are unclear. In this study, we developed a Drosophila model of NRTI-induced PSN that recapitulates the salient features observed in patients undergoing ART: PSN and nociceptive hypersensitivity. Furthermore, our data demonstrate that pathways known to suppress PSN induced by chemotherapeutic drugs are ineffective in suppressing the PSN or nociception induced by NRTIs. Instead, we found that increased dynamics of a peripheral sensory neuron may possibly underlie NRTI-induced PSN and nociception. Our model provides a solid platform in which to investigate further mechanisms of ART-induced PSN and nociceptive hypersensitivity.

This article has an associated First Person interview with the first author of the paper.

Summary: Nucleoside reverse transcriptase inhibitors (NRTIs) that are important components of anti-retroviral therapies also cause peripheral sensory neuropathies (PSN). This article investigates ways in which NRTIs may cause PSN and outlines ways to better understand the mechanisms underlying it.

Higher iron stores and the HFE 187C>G variant delay onset of peripheral neuropathy during combination antiretroviral therapy

OBJECTIVE

People with HIV (PWH) continue to experience sensory neuropathy and neuropathic pain in the combination antiretroviral therapy (cART) era for unclear reasons. This study evaluated the role of iron in a previously reported association of iron-loading hemochromatosis (HFE) gene variants with reduced risk of neuropathy in PWH who received more neurotoxic cART, since an iron-related mechanism also might be relevant to neuropathic symptoms in PWH living in low-resource settings today.

DESIGN

This time-to-event analysis addressed the impact of systemic iron levels on the rapidity of neuropathy onset in PWH who initiated cART.

METHODS

Soluble transferrin receptor (sTFR), the sTFR-ferritin index of iron stores, and high-sensitivity C-reactive protein (hsCRP) levels were determined in stored baseline sera from participants of known HFE genotype from AIDS Clinical Trials Group (ACTG) Study 384, a multicenter randomized clinical trial that evaluated cART strategies. Associations with incident neuropathy were evaluated in proportional-hazards, time-to-event regression models, adjusting for potential confounders.

RESULTS

Of 151 eligible participants with stored serum who were included in the original genetic study, 43 had cART-associated neuropathy; 108 had sufficient serum for analysis, including 30 neuropathy cases. Carriers of HFE variants had higher systemic iron (lower sTFR and sTFR-ferritin index) and lower hsCRP levels than non-carriers (all p<0.05). Higher sTFR or iron stores, the HFE 187C>G variant, and lower baseline hsCRP were associated with significantly delayed neuropathy in self-reported whites (n = 28; all p-values<0.05), independent of age, CD4+ T-cell count, plasma HIV RNA, and cART regimen.

CONCLUSIONS

Higher iron stores, the HFE 187C>G variant, and lower hsCRP predicted delayed onset of neuropathy among self-reported white individuals initating cART. These findings require confirmation but may have implications for cART in HIV+ populations in areas with high endemic iron deficiency, especially those PWH in whom older, more neurotoxic antiretroviral drugs are occasionally still used.

Peripheral neuropathy in patients with human immunodeficiency viral infection at a tertiary hospital in Ghana

Peripheral neuropathy (PN) is the most frequent neurological complication in people living with HIV/AIDS. Neurological damage was identified to not only be caused by the viral infection itself but also through neurotoxic antiretroviral therapy (ART). PN is associated with a variety of risk factors; however, detailed knowledge is scarce for sub-Saharan African populations, bearing among the highest HIV/AIDS infection burden.In a cross-sectional study, we assessed the prevalence of PN in 525 adult outpatients suffering from HIV/AIDS and admitted to the largest tertiary hospital in Ghana. Through a detailed questionnaire and clinical examination including neurologic assessment and laboratory blood sample testing, this study investigated associations of PN with demographic and health determinants and identified risk factors associated with sensory neuropathy.The prevalence of PN in the Ghanaian cohort was 17.7% and increased odd ratios (OR) when patients were taller (> 1.57 m; OR = 3.84; 95% CI 1.38-10.66) or reached the age > 34 years (p = 0.124). Respondents with longer education duration had significantly less PN (≥ 9 years of education; OR = 0.49; 95% CI 0.26-0.92). The study also identified significant association of PN to both waist and hip girth and neutrophil counts. Curiously, higher adjusted odd ratios (aOR) of PN of patients under ART treatment were observed when CD4 lymphocytes were elevated (aOR = 0.81; 95% CI 0.36-1.83 and aOR = 2.17; 95% CI 0.93-5.05, for 300 and 600 counts, respectively). For patients on ART, an increase of 10 CD4 cell count units increased their chance of developing PN by 1% (aOR = 1.01; 95% CI 1.00 to 1.03).Despite current drug application regulations, prevalence of PN is still unacceptably high in sub-Saharan African populations. Reduction in chronic morbidity through a health system with routine monitoring, early diagnosis and prompt intervention, and effective case management can improve people living with HIV/AIDS' quality of life.

HIV in the cART era and the mitochondrial: immune interface in the CNS

HIV-associated neurocognitive disorders (HAND) persist in the era of effective combined antiretroviral therapy (cART). A large body of literature suggests that mitochondrial dysfunction is a prospective etiology of HAND in the cART era. While viral load is often suppressed and the immune system remains intact in HIV+ patients on cART, evidence suggests that the central nervous system (CNS) acts as a reservoir for virus and low-level expression of viral proteins, which interact with mitochondria. In particular, the HIV proteins glycoprotein 120, transactivator of transcription, viral protein R, and negative factor have each been linked to mitochondrial dysfunction in the brain. Moreover, cART drugs have also been shown to have detrimental effects on mitochondrial function. Here, we review the evidence generated from human studies, animal models, and in vitro models that support a role for HIV proteins and/or cART drugs in altered production of adenosine triphosphate, mitochondrial dynamics, mitophagy, calcium signaling and apoptosis, oxidative stress, mitochondrial biogenesis, and immunometabolism in the CNS. When insightful, evidence of HIV or cART-induced mitochondrial dysfunction in the peripheral nervous system or other cell types is discussed. Lastly, therapeutic approaches to targeting mitochondrial dysfunction have been summarized with the aim of guiding new investigations and providing hope that mitochondrial-based drugs may provide relief for those suffering with HAND.

Hemochromatosis (HFE) Gene Variants Are Associated with Increased Mitochondrial DNA Levels During HIV-1 Infection and Antiretroviral Therapy

Some HIV-associated complications involve mitochondrial dysfunction and may be less common in individuals with iron-loading HFE (hemochromatosis gene) variants. We evaluated HFE 845A and 187G alleles in relation to mitochondrial DNA (mtDNA) levels in peripheral blood mononuclear cells from 85 individuals with HIV infection on uninterrupted antiretroviral therapy (ART) for 15 or more consecutive weeks. Carriers of HFE gene variants (N = 24) had significantly higher mtDNA levels than noncarriers (N = 61), after adjusting for age, race, sex, and type of ART [adjusted β-coefficient 297, p-value < .001 for at least one HFE variant], but mtDNA declined among all individuals on study during 48 weeks on ART. Increased cellular mtDNA content may represent a compensatory response to mitochondrial stress that is influenced by iron-loading HFE variants.

Precision medicine for HIV: where are we?

To date, antiretroviral therapy is highly effective in HIV-affected patients, but the individualization of such a life-long therapy may be advised. This review briefly summarizes the main factors involved in the potential personalization of antiretroviral treatment. Relevant articles in English were identified by PubMed and recent congresses’ abstracts. Foremost influences concerning pharmacodynamics, therapeutic drug monitoring, pharmacogenetics, comorbidities, immune recovery and viral characteristics affecting the healthcare of HIV-positive patients are listed here. Furthermore, pharmacoeconomic aspects are mentioned. Applying pharmacokinetic and pharmacogenetic knowledge may be informative and guide the better choice of treatment in order to achieve long-term efficacy and avoid adverse events. Randomized investigations of the clinical relevance of tailored antiretroviral regimens are needed in order to obtain a better management of HIV/AIDS-affected patients.

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.

Genetics of HIV-associated sensory neuropathy and related pain in Africans

Despite the use of safer antiretroviral medications, the rate of HIV-associated sensory neuropathy (HIV-SN), the most common neurological complication of HIV, remains high. This condition is often painful and has a negative effect on quality of life. Up to 90% of those with HIV-SN experience pain for which there is no effective analgesic treatment. Genetic factors are implicated, but there is a lack of a comprehensive body of research for African populations. This knowledge gap is even more pertinent as Africans are most affected by HIV. However, recent studies performed in Southern African populations have identified genes displaying potential as genetic markers for HIV-SN and HIV-SN-associated pain in Africans. Here, we review the published studies to describe current knowledge of genetic risk factors for this disease in Africa.

Pharmacogenomics of antimicrobial agents

Antimicrobial efficacy and toxicity varies between individuals owing to multiple factors. Genetic variants that affect drug-metabolizing enzymes may influence antimicrobial pharmacokinetics and pharmacodynamics, thereby determining efficacy and/or toxicity. In addition, many severe immune-mediated reactions have been associated with HLA class I and class II genes. In the last two decades, understanding of pharmacogenomic factors that influence antimicrobial efficacy and toxicity has rapidly evolved, leading to translational success such as the routine use of HLA-B*57:01 screening to prevent abacavir hypersensitivity reactions. This article examines recent advances in the field of antimicrobial pharmacogenomics that potentially affect treatment efficacy and toxicity, and challenges that exist between pharmacogenomic discovery and translation into clinical use.

Pharmacogenetics as a tool to tailor antiretroviral therapy: A review

Highly active antiretroviral therapy (HAART) has substantially changed human immunodeficiency virus (HIV) infection from an inexorably fatal condition into a chronic disease with a longer life expectancy. This means that HIV patients should receive antiretroviral drugs lifelong, and the problems concerning with a chronic treatment (tolerability, side effects, adherence to treatment) have now become dominant. In this context, strategies for the treatment personalization have taken a central role in optimizing the therapeutic response and prevention of adverse drug reactions. In this setting, the study of pharmacogenetics features could be a very useful tool in clinical practice; moreover, nowadays the study of genetic profiles allows optimizations in the therapeutic management of People Living With HIV (PLWH) through the use of test introduced into clinical practice and approved by international guidelines for the adverse effects prevention such as the genetic test HLA-B*5701 to detect hypersensitivity to Abacavir. For other tests further studies are needed: CYP2B6 516 G > T testing may be able to identify patients at higher risk of Central Nervous System side effects following standard dosing of Efavirenz, UGT1A1*28 testing before initiation of antiretroviral therapy containing Atazanavir may aid in identifying individuals at risk of hyperbilirubinaemia. Pharmacogenetics represents a ​​research area with great growth potential which may be useful to guide the rational use of antiretrovirals.

Can antiretroviral therapy be tailored to each human immunodeficiency virus-infected individual? Role of pharmacogenomics

Pharmacogenetics refers to the effect of single nucleotide polymorphisms (SNPs) within human genes on drug therapy outcome. Its study might help clinicians to increase the efficacy of antiretroviral drugs by improving their pharmacokinetics and pharmacodynamics and by decreasing their side effects. HLAB*5701 genotyping to avoid the abacavir-associated hypersensitivity reaction (HSR) is a cost-effective diagnostic tool, with a 100% of negative predictive value, and, therefore, it has been included in the guidelines for treatment of human immunodeficiency virus (HIV) infection. HALDRB*0101 associates with nevirapine-induced HSR. CYP2B6 SNPs modify efavirenz plasma levels and their genotyping help decreasing its central nervous system, hepatic and HSR toxicities. Cytokines SNPs might influence the development of drug-associated lipodystrophy. APOA5, APOB, APOC3 and APOE SNPs modify lipids plasma levels and might influence the coronary artery disease risk of HIV-infected individuals receiving antiretroviral therapy. UGT1A1*28 and ABCB1 (MDR1) 3435C > T SNPs modify atazanavir plasma levels and enhance hyperbilirubinemia. Much more effort needs to be still devoted to complete large prospective studies with multiple SNPs genotyping in order to reveal more clues about the role played by host genetics in antiretroviral drug efficacy and toxicity.

Host genetic factors predisposing to HIV-associated neurocognitive disorder

The success of combination antiretroviral therapy (cART) in transforming the lives of HIV-infected individuals with access to these drugs is tempered by the increasing threat of HIV-associated neurocognitive disorders (HAND) to their overall health and quality of life. Intensive investigations over the past two decades have underscored the role of host immune responses, inflammation, and monocyte-derived macrophages in HAND, but the precise pathogenic mechanisms underlying HAND remain only partially delineated. Complicating research efforts and therapeutic drug development are the sheer complexity of HAND phenotypes, diagnostic imprecision, and the growing intersection of chronic immune activation with aging-related comorbidities. Yet, genetic studies still offer a powerful means of advancing individualized care for HIV-infected individuals at risk. There is an urgent need for 1) longitudinal studies using consistent phenotypic definitions of HAND in HIV-infected subpopulations at very high risk of being adversely impacted, such as children, 2) tissue studies that correlate neuropathological changes in multiple brain regions with genomic markers in affected individuals and with changes at the RNA, epigenomic, and/or protein levels, and 3) genetic association studies using more sensitive subphenotypes of HAND. The NIH Brain Initiative and Human Connectome Project, coupled with rapidly evolving systems biology and machine learning approaches for analyzing high-throughput genetic, transcriptomic and epigenetic data, hold promise for identifying actionable biological processes and gene networks that underlie HAND. This review summarizes the current state of understanding of host genetic factors predisposing to HAND in light of past challenges and suggests some priorities for future research to advance the understanding and clinical management of HAND in the cART era.

Genetic variation in iron metabolism is associated with neuropathic pain and pain severity in HIV-infected patients on antiretroviral therapy

HIV sensory neuropathy and distal neuropathic pain (DNP) are common, disabling complications associated with combination antiretroviral therapy (cART). We previously associated iron-regulatory genetic polymorphisms with a reduced risk of HIV sensory neuropathy during more neurotoxic types of cART. We here evaluated the impact of polymorphisms in 19 iron-regulatory genes on DNP in 560 HIV-infected subjects from a prospective, observational study, who underwent neurological examinations to ascertain peripheral neuropathy and structured interviews to ascertain DNP. Genotype-DNP associations were explored by logistic regression and permutation-based analytical methods. Among 559 evaluable subjects, 331 (59%) developed HIV-SN, and 168 (30%) reported DNP. Fifteen polymorphisms in 8 genes (p<0.05) and 5 variants in 4 genes (p<0.01) were nominally associated with DNP: polymorphisms in TF, TFRC, BMP6, ACO1, SLC11A2, and FXN conferred reduced risk (adjusted odds ratios [ORs] ranging from 0.2 to 0.7, all p<0.05); other variants in TF, CP, ACO1, BMP6, and B2M conferred increased risk (ORs ranging from 1.3 to 3.1, all p<0.05). Risks associated with some variants were statistically significant either in black or white subgroups but were consistent in direction. ACO1 rs2026739 remained significantly associated with DNP in whites (permutation p<0.0001) after correction for multiple tests. Several of the same iron-regulatory-gene polymorphisms, including ACO1 rs2026739, were also associated with severity of DNP (all p<0.05). Common polymorphisms in iron-management genes are associated with DNP and with DNP severity in HIV-infected persons receiving cART. Consistent risk estimates across population subgroups and persistence of the ACO1 rs2026739 association after adjustment for multiple testing suggest that genetic variation in iron-regulation and transport modulates susceptibility to DNP.

Patient reported outcome instruments used in clinical trials of HIV-infected adults on NNRTI-based therapy: a 10-year review

BACKGROUND

Patient-reported outcomes (PROs) may provide valuable information to clinicians and patients when choosing initial antiretroviral therapy.

OBJECTIVE

To identify and classify PRO instruments used to measure treatment effects in clinical trials evaluating NNRTIs.

METHODS

We conducted a structured literature review using PubMed to identify NNRTI trials published from March 2003 to February 2013. Studies identified--based on disease, instrument, PRO, and NNRTI medication terms were reviewed--to identify PRO instruments. Domains measured within each instrument were recorded to understand key areas of interest in NNRTIs.

RESULTS

Of 189 articles reviewed, 27 validated instruments were administered in 26 unique trials, with a mean of 1.9 instruments (median: 1; range: 1-7) per trial. The Medical Outcomes Study HIV Health Survey (MOS-HIV) was the most commonly used instrument (n = 8 trials). Seventeen trials (65%) included at least one multidimensional health-related quality of life (HRQL) instrument (HIV-targeted, n = 11; general, n = 8). Other validated instruments measured sleep (n = 5), depression (n = 5), anxiety (n = 4), psychiatric symptoms (n = 2), beliefs about HIV medications (n = 2), HIV symptoms (n = 1), and stress (n = 1).

CONCLUSIONS

Although review of recent NNRTI trials suggests a lack of consensus on the optimal PRO instruments, a typical battery is comprised of a multidimensional HRQL measure coupled with one or more symptom measures. Further work is needed to clarify advantages and disadvantages of using specific PRO instruments to measure relevant constructs and to identify the most useful batteries of instruments for NNRTI trials.

Association of thymidylate synthase polymorphisms with acute pancreatitis and/or peripheral neuropathy in HIV-infected patients on stavudine-based therapy

Background

Low expression thymidylate synthase (TS) polymorphism has been associated with increased stavudine triphosphate intracellular (d4T-TP) levels and the lipodystrophy syndrome. The use of d4T has been associated with acute pancreatitis and peripheral neuropathy. However, no relationship has ever been proved between TS polymorphisms and pancreatitis and/or peripheral neuropathy.

Methods

We performed a case-control study to assess the relationship of TS and methylene-tetrahydrofolate reductase (MTHFR) gene polymorphisms with acute pancreatitis and/or peripheral neuropathy in patients exposed to d4T. Student’s t test, Pearson’s correlations, one-way ANOVA with Bonferroni correction and stepwise logistic regression analyses were done.

Results

Forty-three cases and 129 controls were studied. Eight patients (18.6%) had acute pancreatitis, and 35 (81.4%) had peripheral neuropathy. Prior AIDS was more frequent in cases than in controls (OR = 2.36; 95%CI 1.10–5.07, P = 0.0247). L7ow expression TS and MTHFR genotype associated with increased activity were more frequent in patients with acute pancreatitis and/or peripheral neuropathy than in controls (72.1% vs. 46.5%, OR = 2.97; 95%CI: 1.33–6.90, P = 0.0062, and 79.1% vs. 56.6%, OR = 2.90, 95%CI: 1.23–7.41, P = 0.0142, respectively). Independent positive or negative predictors for the development of d4T-associated pancreatitis and/or peripheral neuropathy were: combined TS and MTHFR genotypes (reference: A+A; P = 0.002; OR_A+B = 0.34 [95%CI: 0.08 to 1.44], OR_B+A = 3.38 [95%CI: 1.33 to 8.57], OR_B+B = 1.13 [95%CI: 0.34 to 3.71]), nadir CD4 cell count >200 cells/mm³ (OR = 0.38; 95%CI: 0.17–0.86, P = 0.021), and HALS (OR = 0.39 95%CI: 0.18–0.85, P = 0.018).

Conclusions

Low expression TS plus a MTHFR genotype associated with increased activity is associated with the development of peripheral neuropathy in d4T-exposed patients.

HIV peripheral neuropathy

Peripheral neuropathies are the most common neurological manifestations occurring in HIV-infected individuals. Distal symmetrical sensory neuropathy is the most common form encountered today and is one of the few that are specific to HIV infection or its treatment. The wide variety of other neuropathies is akin to the neuropathies seen in the general population and should be managed accordingly. In the pre-ART era, neuropathies were categorized according to the CD4 count and HIV viral load. In the early stages of HIV infection when CD4 count is high, the inflammatory demyelinating neuropathies predominate and in the late stages with the decline of CD4 count opportunistic infection-related neuropathies prevail. That scenario has changed with the present almost universal use of ART (antiretroviral therapy). Hence, HIV-associated peripheral neuropathies are better classified according to their clinical presentations: distal symmetrical polyneuropathy, acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), mononeuropathies, mononeuropathies multiplex and cranial neuropathies, autonomic neuropathy, lumbosacral polyradiculomyelopathy, and amyotrophic lateral sclerosis (ALS)-like motor neuropathy. Treated with ART, HIV-infected individuals are living longer and are at a higher risk of metabolic and age-related complications; moreover they are also prone to the potentially neurotoxic effects of ART. There are no epidemiological data regarding the incidence and prevalence of the peripheral neuropathies. In the pre-ART era, most data were from case reports, series of patients, and pooled autopsy data. At that time the histopathological evidence of neuropathies in autopsy series was almost 100%. In large prospective cohorts presently being evaluated, it has been found that 57% of HIV-infected individuals have distal symmetrical sensory neuropathy and 38% have neuropathic pain. It is now clear that distal symmetrical sensory neuropathy is caused predominantly by the ART's neurotoxic effect but may also be caused by the HIV itself. With a sizeable morbidity, the neuropathic pain caused by distal symmetrical sensory neuropathy is very difficult to manage; it is often necessary to change the ART regimen before deciding upon the putative role of HIV infection itself. If the change does not improve the pain, there are few options available; the most common drugs used for neuropathic pain are usually not effective. One is left with cannabis, which cannot be recommended as routine therapy, recombinant human nerve growth factor, which is unavailable, and topical capsaicin with its side-effects. Much has been done to and learned from HIV infection in humans; HIV-infected individuals, treated with ART, are now dying mostly from cardiovascular disease and non-AIDS-related cancers. It hence behooves us to find new approaches to mitigate the residual neurological morbidity that still impacts the quality of life of that population.

Neuromuscular manifestations of HIV/AIDS

The human immunodeficiency virus (HIV) epidemic, now entering its fourth decade, affects approximately 33 million people living in both developed and resource-limited countries. Neurological complications of the peripheral nervous system are common in HIV-infected patients, and neuromuscular pathology is associated with significant morbidity. Peripheral neuropathy is the most common neuromuscular manifestation observed in HIV/AIDS, and in the antiretroviral era, its prevalence has increased. The purpose of this review was to describe the clinical spectrum of neuromuscular disorders in the setting of HIV infection and to provide an approach to diagnosis and management.

Painful HIV-associated sensory neuropathy

SUMMARY Painful HIV-associated sensory neuropathy (HIV-SN) is an early recognized neurological complication of HIV. The introduction of effective HIV treatments saw increased rates of HIV-SN, with some antiretrovirals (notably stavudine) being neurotoxic. Although neurotoxic antiretrovirals are being phased out, the available data suggest that incident HIV-SN will remain common, impairing quality of life, mobility and ability to work. Despite its major clinical importance, the pathogenesis and determinants of pain in HIV-SN are poorly understood, and effective prevention and analgesic strategies are lacking. Here, we review what is known about the rates and risk factors for painful HIV-SN, the laboratory models informing our understanding of neuropathic pain in HIV, and the future clinical and laboratory work needed to fully understand this debilitating condition and provide effective management strategies for those affected.

Mitochondrial DNA variation and HIV-associated sensory neuropathy in CHARTER

HIV-associated sensory neuropathy remains an important complication of combination antiretroviral therapy and HIV infection. Mitochondrial DNA haplogroups and single nucleotide polymorphisms (SNPs) have previously been associated with symptomatic neuropathy in clinical trial participants. We examined associations between mitochondrial DNA variation and HIV-associated sensory neuropathy in CNS HIV Antiretroviral Therapy Effects Research (CHARTER). CHARTER is a USA-based longitudinal observational study of HIV-infected adults who underwent a structured interview and standardized examination. HIV-associated sensory neuropathy was determined by trained examiners as ≥1 sign (diminished vibratory and sharp-dull discrimination or ankle reflexes) bilaterally. Mitochondrial DNA sequencing was performed and haplogroups were assigned by published algorithms. Multivariable logistic regression of associations between mitochondrial DNA SNPs, haplogroups, and HIV-associated sensory neuropathy were performed. In analyses of associations of each mitochondrial DNA SNP with HIV-associated sensory neuropathy, the two most significant SNPs were at positions A12810G [odds ratio (95 % confidence interval) = 0.27 (0.11-0.65); p = 0.004] and T489C [odds ratio (95 % confidence interval) = 0.41 (0.21-0.80); p = 0.009]. These synonymous changes are known to define African haplogroup L1c and European haplogroup J, respectively. Both haplogroups were associated with decreased prevalence of HIV-associated sensory neuropathy compared with all other haplogroups [odds ratio (95 % confidence interval) = 0.29 (0.12-0.71); p = 0.007 and odds ratio (95 % confidence interval) = 0.42 (0.18-1.0); p = 0.05, respectively]. In conclusion, in this cohort of mostly combination antiretroviral therapy-treated subjects, two common mitochondrial DNA SNPs and their corresponding haplogroups were associated with a markedly decreased prevalence of HIV-associated sensory neuropathy.

HIV-associated sensory neuropathy: risk factors and genetics

HIV-associated sensory neuropathy (HIV-SN) remains a common neurological complication of HIV infection despite the introduction of effective antiretroviral therapies. Exposure to neurotoxic antiretroviral drugs and increasing age have consistently been identified as risk factors for HIV-SN, while comorbid conditions with underlying predisposition to cause peripheral neuropathy (eg, diabetes mellitus, malnutrition, isoniazid exposure), ethnicity, and increasing height also have been implicated. Genetic association studies have identified genes affecting mitochondrial function and genes involved in the inflammatory response that modify the risk for HIV-SN among patients exposed to neurotoxic antiretrovirals. However, there is a lack of data on clinical, demographic, and genetic risk factors for HIV-SN in the modern era, with the rate of HIV-SN remaining unacceptably high despite the introduction of safer medications. Thus, more work is required to identify the principal factors that increase an individual's risk for HIV-SN so that effective preventative or therapeutic strategies can be implemented.

Pharmacogenetics of the lipodystrophy syndrome associated with HIV infection and combination antiretroviral therapy

INTRODUCTION

Antiretroviral drugs have been associated with several toxicities that limit their success. Of the chronic toxicities, the lipodystrophy syndrome is of special concern due to the metabolic alterations that can accompany it. Why some patients treated with a particular antiretroviral regimen develop lipodystrophy, while others do not, is a medical mystery, but it has been suggested that individuals may (or may not) have a genetically conditioned predisposition. Pharmacogenetics is the science that studies how the genetic composition of individuals can give rise to interindividual variations in response to drugs and drug toxicity.

AREAS COVERED

This article reviews the published investigations on the association between host genetic determinants in treated HIV-infected patients and the presence of lipodystrophy. Studies were identified through a PubMed database search. Case-control and longitudinal studies into pharmacogenetic association were selected. Areas covered include the data on the genetic variants of mitochondrial parameters, cytokines, adipokines, proteins involved in adipocyte biology and proteins involved in stavudine metabolism.

EXPERT OPINION

Most studies provide inconsistent data due to partial genetic evaluation, different assessment of lipodystrophy and low number of patients evaluated. The pharmacogenetics of lipodystrophy in HIV-infected patients treated with antiretroviral drugs still belongs in the research laboratory.

Influence of Age and Neurotoxic HAART Use on Frequency of HIV Sensory Neuropathy

Background. Sensory neuropathy (SN) is one of the most common AIDS-associated neurologic disorders especially in the era of highly active antiretroviral therapy (HAART). The aim of this study was to determine the prevalence of SN among highly-active-antiretroviral-therapy- (HAART-) experienced and HAART-naïve HIV-positive individuals and to investigate the relationship to demographic, clinical, and laboratory factors. Methods. 323 patients with HIV infection (142 on HAART and 181 HAART naïve) were enrolled in a cross-sectional neuropathy screening program. Data was collected using structured questionnaires which contained the brief peripheral neuropathy screening tool of AIDS Clinical Trial Group protocol. Neuropathy was defined by the presence of at least 1 clinical sign in a distal, symmetrical pattern. Patients were classified as symptomatic if they described aching, stabbing, or burning pain, paresthesia, or numbness in a similar distribution. Demographic, clinical, and laboratory details were documented as risk factors. Result. The prevalence of sensory neuropathy was 39.0% (126/323), (of which 29/126 (23%)) were symptomatic. Amongst those on HAART, 60/142 (42.3%) had SN compared to 66/181 (36.5%) HAART-naïve individuals (P = 0.29). On multivariate analyses, the independent associations with SN were increasing age (P = 0.03) and current exposure to stavudine (P = 0.00). Gender (P = 0.99) height (P = 0.07) use of HAART (P = 0.50), duration of HAART treatment (P = 0.10), and lower CD4 count (P = 0.12) were not associated with an increased SN risk. Conclusion. HIV SN remains common despite improved immunologic function associated with HAART and decreased neurotoxic HAART use. In this cross-sectional analysis, age and stavudine-based therapies were the independent risk factors.

Individualization of antiretroviral therapy

Antiretroviral therapy (ART) has evolved considerably over the last three decades. From the early days of monotherapy with high toxicities and pill burdens, through to larger pill burdens and more potent combination therapies, and finally, from 2005 and beyond where we now have the choice of low pill burdens and once-daily therapies. More convenient and less toxic regimens are also becoming available, even in resource-poor settings. An understanding of the individual variation in response to ART, both efficacy and toxicity, has evolved over this time. The strong association of the major histocompatibility class I allele HLA-B*5701 and abacavir hypersensitivity, and its translation and use in routine HIV clinical practice as a predictive marker with 100% negative predictive value, has been a success story and a notable example of the challenges and triumphs in bringing pharmacogenetics to the clinic. In real clinical practice, however, it is going to be the exception rather than the rule that individual biomarkers will definitively guide patient therapy. The need for individualized approaches to ART has been further increased by the importance of non-AIDS comorbidities in HIV clinical practice. In the future, the ideal utilization of the individualized approach to ART will likely consist of a combined approach using a combination of knowledge of drug, virus, and host (pharmacogenetic and pharmacoecologic [factors in the individual’s environment that may be dynamic over time]) information to guide the truly personalized prescription. This review will focus on our knowledge of the pharmacogenetics of the efficacy and toxicity of currently available antiretroviral agents and the current and potential utility of such information and approaches in present and future HIV clinical care.

Mitochondrial genomics and CD4 T-cell count recovery after antiretroviral therapy initiation in AIDS clinical trials group study 384

BACKGROUND

Mitochondrial DNA (mtDNA) variation has been associated with time to progression to AIDS and adverse effects from antiretroviral therapy (ART). In this study, full mitochondrial DNA (mtDNA) sequence data from US-based adult participants in the AIDS Clinical Trials Group study 384 was used to assess associations between mtDNA variants and CD4 T-cell recovery with ART.

METHODS

Full mtDNA sequence was determined using chip-based array sequencing. Sequence and CD4 cell count data was available at baseline and after ART initiation for 423 subjects with HIV RNA levels <400 copies per milliliter plasma. The primary outcome was change in CD4 count of ≥100 cells per cubic millimeter from baseline. Analyses were adjusted for baseline age, CD4 cell count, HIV RNA, and naive:memory CD4 cell ratio.

RESULTS

Race-stratified analysis of mtDNA variants with a minor allele frequency >1% revealed multiple mtDNA variants marginally associated (P < 0.05 before Bonferroni correction) with CD4 cell recovery. The most significant single nucleotide polymorphism associations were those tagging the African L2 haplogroup, which was associated with a decreased likelihood of ≥100 cells per cubic millimeter CD4 count increase at week 48 in non-Hispanic blacks (adjusted odds ratio = 0.17; 95% confidence interval = 0.06 to 0.53; P = 0.002).

CONCLUSIONS

An African mtDNA haplogroup was associated with CD4 cell recovery after ART in this clinical trial population. These initial findings warrant replication and further investigation to confirm the role of mtDNA variation in CD4 cell recovery during ART.

Hepatitis C seropositivity is not a risk factor for sensory neuropathy among patients with HIV

BACKGROUND

Sensory neuropathy (SN) is common in patients with HIV. Hepatitis C (HCV) coinfection is often cited as an HIV-SN risk factor, but data to support this are lacking. This collaboration aimed to examine the association between HCV serostatus and SN risk among ambulatory HIV-positive patients.

METHODS

Patients with HIV were assessed in cross-sectional studies in Baltimore, Jakarta, Johannesburg, Kuala Lumpur, Melbourne, and Sydney for SN (defined by both supportive symptoms and signs). HCV seropositivity was assessed as an SN risk using a chi(2) test, followed by logistic regression modeling to correct for treatment exposures and demographics.

RESULTS

A total of 837 patients of African, Asian, and Caucasian descent were studied. HCV seroprevalence varied by site (Baltimore n = 104, 61% HCV+; Jakarta 96, 51%; Johannesburg 300, 1%; Kuala Lumpur 97, 10%; Melbourne 206, 16%; Sydney 34, 18%). HCV seropositivity was not associated with increased SN risk at any site, but was associated with reduced SN risk in Melbourne (p = 0.003). On multivariate analyses, the independent associations with SN were increasing age, height, and stavudine exposure. HCV seropositivity was not independently associated with an increased SN risk at any site, but associated independently with reduced SN risk in Baltimore (p = 0.04) and Melbourne (p = 0.06).

CONCLUSIONS

Hepatitis C (HCV) seropositivity was not associated with increased sensory neuropathy risk among HIV-positive patients at any site. While we were unable to assess HCV RNA or liver damage, the data suggest that HCV coinfection is not a major contributor to HIV-SN. HCV = hepatitis C; SN = sensory neuropathy.

Continued high prevalence and adverse clinical impact of human immunodeficiency virus-associated sensory neuropathy in the era of combination antiretroviral therapy: the CHARTER Study

OBJECTIVE

To provide updated estimates of the prevalence and clinical impact of human immunodeficiency virus-associated sensory neuropathy (HIV-SN) and neuropathic pain due to HIV-SN in the combination antiretroviral therapy (CART) era.

DESIGN

Prospective, cross-sectional analysis. Clinical correlates for HIV-SN and neuropathic pain, including age, exposure to CART, CD4 levels, plasma viral load, hepatitis C virus infection, and alcohol use disorders, were evaluated in univariate and multivariate models.

SETTING

Six US academic medical centers.

PATIENTS

One thousand five hundred thirty-nine HIV-infected individuals enrolled in the CNS (Central Nervous System) HIV Anti-Retroviral Therapy Effects Research study.

MAIN OUTCOME MEASURES

The presence of HIV-SN, defined by 1 or more clinical signs (diminished vibration or sharp sensation in the legs and feet; reduced ankle reflexes) in a distal, symmetrical pattern. Neuropathic pain was defined as aching, stabbing, or burning in a similar distribution. The effect on quality of life was assessed with the Medical Outcomes Study HIV Health Survey.

RESULTS

We found HIV-SN in 881 participants. Of these, 38.0% reported neuropathic pain. Neuropathic pain was significantly associated with disability in daily activities, unemployment, and reduced quality of life. Risk factors for HIV-SN after adjustment were advancing age (odds ratio, 2.1 [95% confidence interval, 1.8-2.5] per 10 years), lower CD4 nadir (1.2 [1.1-1.2] per 100-cell decrease), current CART use (1.6 [1.3-2.8]), and past "D-drug" use (specific dideoxynucleoside analogue antiretrovirals) (2.0 [1.3-2.6]). Risk factors for neuropathic pain were past D-drug use and higher CD4 nadir.

CONCLUSIONS

Neuropathic pain and HIV-SN remain prevalent, causing substantial disability and reduced quality of life even with successful CART. The clinical correlates of HIV-SN have changed with the evolution of treatment. These findings argue for redoubled efforts to determine HIV-SN pathogenesis and the development of symptomatic and neuroregenerative therapies.

Mechanisms of antiretroviral therapy-induced mitochondrial dysfunction

PURPOSE OF REVIEW

To discuss novel developments related to the mechanisms of antiretroviral therapy-related mitochondrial toxicity, describe some apparent paradoxes in the current understanding of this field, and present questions that should be addressed by future research.

RECENT FINDINGS

The early polymerase gamma hypothesis states that nucleoside reverse transcriptase inhibitors can inhibit mitochondrial DNA replication and cause mitochondrial toxicity through mtDNA depletion. This mechanism is supported by a large body of evidence. Clinical manifestations of mitochondrial dysfunction are not always associated with mtDNA depletion. Increased mtDNA levels after nucleoside reverse transcriptase inhibitor exposure, as well as seemingly severe mtDNA depletion in individuals who show no clinical toxicity, have been reported. These and other observations suggest that additional mechanisms are involved in antiretroviral therapy toxicity, a notion supported by recent studies. Individuals given the same antiretroviral regimen can differ vastly with respect to the development of mitochondrial toxicity symptoms, reflecting interindividual variability. Some factors that may modulate this variability will be discussed.

SUMMARY

Mitochondrial toxicity induced by nucleoside reverse transcriptase inhibitors and their metabolic intermediates is probably mediated through many direct and indirect mechanisms. Depending on the mechanisms at play, the long-term health consequences of this toxicity may vary.

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.

Pharmacogenetics of antiretrovirals

The introduction of highly active antiretroviral therapy (HAART) as standard of care has changed the natural history of HIV infection into a manageable chronic disease requiring long-term antiretroviral (ARV) treatment. However, response to HAART is often limited by the occurrence of toxicity or by the emergence of drug resistance. Antiretroviral treatment is characterized by differing rates of adverse events and responses. Genetic variations between human beings account for a relevant proportion of this variability. A relevant number of associations between human genetic variants and predisposition to adverse events have been described and for some antiretroviral drugs a clear and casual genotype-phenotype correlation has already been established. The strong association between abacavir hypersensitivity reaction and HLA-B*5701 has been demonstrated in both observational and blinded randomized clinical trials in racially diverse populations and represents the best example of the clinical utility of pharmacogenetic screening in HIV medicine. Genotyping for HLA-B*5701 before prescribing an abacavir containing regimen has been introduced into routine clinical practice as the standard of care for all patients. Other well-established associations include CYP2B6 alleles and efavirenz central nervous system side effects, UGT1A1 alleles and atazanavir-associated hyperbilirubinemia and HLA class II allele HLA-DRB*0101 and nevirapine-associated hypersensitivity. Despite genetic associations having been described for peripheral neuropathy, lipodystrophy, hyperlipidaemia, pancreatitis and renal proximal tubulopathy, numerous barriers exist to the successful introduction of widespread genetic testing to the clinic. Future prospects point in the direction of individualization of antiretroviral therapy through insights from host genetics. The present paper is aimed to provide a comprehensive review of the published literature and to summarize the state of research in this area. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010.

Pharmacogenetics of nucleoside reverse-transcriptase inhibitor-associated peripheral neuropathy

Peripheral neuropathy is an important complication of antiretroviral therapy. Nucleoside reverse-transcriptase inhibitor (NRTI)-associated mitochondrial dysfunction, inflammation and nutritional factors are implicated in its pathogenesis. Pharmacogenetic and genomic studies investigating NRTI neurotoxicity have only recently become possible via the linkage of HIV clinical studies to large DNA repositories. Preliminary case-control studies using these resources suggest that host mitochondrial DNA haplogroup polymorphisms in the hemochromatosis gene and proinflammatory cytokine genes may influence the risk of peripheral neuropathy during antiretroviral therapy. These putative risk factors await confirmation in other HIV-infected populations but they have strong biological plausibility. Work to identify underlying mechanisms for these associations is ongoing. Large-scale studies incorporating clearly defined and validated methods of neuropathy assessment and the use of novel laboratory models of NRTI-associated neuropathy to clarify its pathophysiology are now needed. Such investigations may facilitate the development of more effective strategies to predict, prevent and ameliorate this debilitating treatment toxicity in diverse clinical settings.

Assessment of mitochondrial toxicity by analysis of mitochondrial protein expression in mononuclear cells

BACKGROUND

Real-time PCR has quantified decreased mitochondrial DNA levels in association with nucleoside reverse transcriptase inhibitor (NRTI) therapy of HIV-infected populations. However, real-time PCR is best suited to distinguish log differences in an analyte. In an effort to monitor individuals in more detail, we developed a flow cytometric assay to gauge mitochondrial function.

METHODS

Flow cytometric quantification of a mitochondrial DNA-encoded mitochondrial protein (cytochrome c oxidase subunit I (COX-I)) and a nuclear DNA-encoded mitochondrial protein [ATP synthase subunit D (Sub-D)] was optimized and validated.

RESULTS

Intra-assay and interassay variability was low using peripheral blood mononuclear cells (PBMCs) (CV of 6.15% for COX-I and 7.11% Sub-D, and 9.38% and 9.83% for COX-I and Sub-D, respectively). Mitochondrial protein depletion was evident with in vitro treatment of cells with ethidium bromide (EtBr) and zalcitabine (ddC). Mitochondrial protein expression in 40 healthy adults clustered tightly. Depletion of mitochondrial protein, however, was neither detected in cryopreserved PBMC from NRTI-treated children (n = 9) nor in adults with a history of symptoms consistent with mitochondrial toxicity or ongoing treatment with didanosine (ddI) or stavudine (d4T) (n = 51).

CONCLUSIONS

A validated flow cytometric assay allows simultaneous detection of mitochondrial DNA and nuclear DNA encoded proteins at the single cell level, offering a method to monitor for mitochondrial function. Prospective studies are required to evaluate whether mitochondrial protein loss is observed in at-risk patients prior to the onset of symptoms from mitochondrial dysfunction.

Personalizing antiretroviral therapy: is it a reality?

The concept of personalizing antiretroviral therapy is not novel, since the complexity of the HIV patient and their therapy has always demanded consideration of the patient's 'pharmacoecology', taking into account factors such as adherence, drug-drug and food-drug interactions, underlying disease and host states, such as organ dysfunction and pregnancy. Recent advances in science have taken this one step further with the technology now available to use both a candidate and whole-genome approach to explore the genetics of host-virus interactions, as well as the pharmacogenetics of the toxicity and efficacy of antiretroviral therapy. The genetics of host-virus interactions have improved our understanding of the pathogenesis of HIV which will aid in the research and development of an HIV vaccine. Most published HIV pharmacogenetic studies have utilized a candidate gene approach. Although these types of studies have provided insight into the pathogenesis and pharmacogenetics of drug disposition, drug interactions, drug efficacy and toxicity and host-virus interactions, very few will lend themselves to a widespread clinical application. The application of HLA-B*5701 screening to prevent abacavir hypersensitivity acts as an important example of the successful widespread implementation of a pharmacogenetic test into the clinic and defines the key steps necessary for the clinical application of pharmacogenetic tests in general.

[Toxicogenetics of antiretroviral treatment (II): neurotoxicity, hepatotoxicity, lactic acidosis, kidney damage, and other adverse effects of antiretroviral drugs]

Several pharmacogenetics studies have analyzed the influence of specific genetic polymorphisms on the toxicity of antiretroviral treatment. The present review describes some of the adverse effects of antiretroviral drugs in which a genetic predisposition may be involved: efavirenz-induced neurological toxicity, generally associated with the 516G>T polymorphism of liver enzyme cytochrome P450 2B6 (CYP2B6); hypersensitivity reactions to nevirapine, associated with specific alleles of major histocompatibility complex, mainly the HLA-DRB1*0101 allele, which, in combination with a high CD4 lymphocyte count, has been associated with systemic reactions and hepatitis in Caucasians, and the HLA-Cw8 allele, which is associated with hypersensitivity reactions in persons from the Italian island of Sardinia and from Japan; nevirapine-induced hepatotoxicity associated with the C>T polymorphism in position 3435T of the ABCB1 (MDR-1) gene codifying for glycoprotein P (lower risk); hyperbilirubinemia in patients exposed to atazanavir or indinavir carrying the UGT1A1*28 polymorphism; peripheral neuropathy with nucleoside analogues associated with haplogroup T of the mitochondrial genome (higher risk) and with the HFE C282Y genotype of the hemochromatosis gene (lower risk); the mutation in codon 964 (R964C) of the POLG gene that codifies the mitochondrial polymerase DNA gamma described in a Thai patient with lactic acidosis; the ABCC2 gene haplotypes associated with tenofovir-induced proximal tubulopathy, and the risk of pancreatitis in persons with mutations in the CFTR and SPINK-1 genes.

Hemochromatosis gene polymorphisms, mitochondrial haplogroups, and peripheral lipoatrophy during antiretroviral therapy

BACKGROUND

Antiretroviral therapy (ART)-associated lipoatrophy involves mitochondrial dysfunction. Iron metabolism impacts mitochondrial function and oxidative stress. Mitochondrial haplogroups and hemochromatosis gene (HFE) polymorphisms have been associated with ART-induced neuropathy. We assessed relationships between these variants and lipoatrophy.

METHODS

The AIDS Clinical Trials Group 384 study randomized ART-naive individuals to receive didanosine-stavudine or zidovudine-lamivudine, combined with efavirenz and/or nelfinavir. Substudy A5005s evaluated fat distribution by dual-energy X-ray absorptiometry (DEXA). We characterized HFE polymorphisms 845G>A and 187C>G and European mitochondrial haplogroups in A5005s participants who consented to genetic analyses.

RESULTS

Among 96 participants (58% were white, and 10% were female) with baseline and 48 or 64 week DEXA data, the median limb fat change was -8.8% (interquartile range, -28.7% to +15.6%). HFE 187C/G heterozygotes (n = 23) had less limb fat loss than 187C/C homozygotes (n = 71) (+6.1% vs. -12.5%; P = .02) and were less likely to develop lipoatrophy after adjustment for age, sex, race, and ART randomization (odds ratio, 0.31; 95% confidence interval, 0.10-0.95; P = .04). Among non-Hispanic white participants, median limb fat change was +26.1% among 5 participants with mitochondrial haplogroup J, compared with -9.7% among 49 participants with other mitochondrial haplogroups (P = .07).

CONCLUSIONS

HFE 187C>G and, possibly, mitochondrial haplogroup J gave relative protection against lipoatrophy during ART in A5005s. These associations should be replicated in other studies.

Advances in pharmacogenomics of antiretrovirals: an update

Recent developments in the pharmacogenomics of antiretroviral drugs provide new prospects for predicting the efficacy of treatment and potential adverse effects. HIV/AIDS is a serious but treatable infectious disease, yet current treatment is limited by high rates of adverse drug reactions and development of resistance due to suboptimal drug concentrations in a significant proportion of patients. Antiretroviral therapy is especially suitable for pharmacogenomic investigation as both drug exposure and treatment response can be quantified and certain adverse effects can be assessed with validated measures. Additionally, there is increasing knowledge of the pharmacokinetics and dynamics of antiretroviral drugs, and some candidate genes implicated in the metabolism, transport and adverse effects have been identified. However, recent studies of the association of particular genes and their genetic variants with HIV management and adverse drug reactions have not provided unifying conclusions. This article reviews the most recently published work and summarizes the state of research in this area. Future directions for research and the application of this technology to the clinical practice of individualizing treatment for HIV management are discussed.

Pharmacogenetics and the potential for the individualization of antiretroviral therapy

PURPOSE OF REVIEW

Genetic associations highlighting differences in the response to HIV infection and treatment have significantly furthered our understanding of the pathogenesis, pharmacokinetics and pharmacodynamics of antiretroviral drug action and toxicities and HIV disease itself. This review focuses on the current knowledge of associations between polymorphisms and treatment outcomes in HIV with particular emphasis on clinically relevant relationships likely to lead to the individualization of antiretroviral therapy.

RECENT FINDINGS

Our understanding of the immunogenetic basis of drug toxicity has been furthered by human leucocyte antigen associations with hypersensitivities for the antiretroviral drugs abacavir and nevirapine. For abacavir in particular, the use of HLA-B*5701 as a screening test appears to be generalizable across racially diverse populations and has been supported by both observational, and blinded randomized controlled trials.

SUMMARY

Differences in HIV acquisition and progression as well as antiretroviral efficacy and toxicity will continue to provide the basis for research to define the genetic basis of such diversity. Despite the plethora of research in this area, numerous barriers exist to the successful operationalization of genetic testing to the clinic. HLA-B*5701 screening to prevent abacavir hypersensitivity is currently the most relevant to clinical practice and highlights that the promise of cost-effective testing can be facilitated by robust laboratory methodology and quality assurance programs that can be applied to diverse treatment settings.

Cytokine genotype suggests a role for inflammation in nucleoside analog-associated sensory neuropathy (NRTI-SN) and predicts an individual's NRTI-SN risk

Nucleoside analog-associated sensory neuropathy (NRTI-SN) attributed to stavudine, didanosine, or zalcitabine (the dNRTIs) and distal sensory polyneuropathy (DSP) attributed to HIV are clinically indistinguishable. As inflammatory cytokines are involved in DSP, we addressed a role for inflammation in NRTI-SN by determining the alleles of immune-related genes carried by patients with and without NRTI-SN. Demographic details associated with risk of various neuropathies were included in the analysis. Alleles of 14 polymorphisms in 10 genes were determined in Australian HIV patients with definite NRTI-SN (symptom onset <6 months after first dNRTI exposure, n = 16), NRTI-SN-resistant patients (no neuropathy despite >6 months on dNRTIs, n = 20), patients with late onset NRTI-SN (neuropathy onset after >6 months of dNRTIs, n = 19), and HIV-negative controls. Carriage of TNFA-1031*2 was highest in NRTI-SN patients, suggesting potentiation of NRTI-SN. Carriage of IL12B (3' UTR)*2 was higher in NRTI-SN-resistant patients than controls or NRTI-SN patients, suggesting a protective role. BAT1 (intron 10)*2 was more common in NRTI-SN than resistant patients, but neither group differed from controls. This marks the conserved HLA-A1, B8, DR3 haplotype. Of the demographic details considered, increasing height was associated with NRTI-SN risk. A model including cytokine genotype and height predicted NRTI-SN status (p < 0.0001, R(2) = 0.54). Late onset NRTI-SN patients clustered genetically with NRTI-SN-resistant patients, so these patients may be genetically "protected." In addition to patient height, cytokine genotype influenced NRTI-SN risk following dNRTI exposure, suggesting inflammation contributes to NRTI-SN.

Neurotoxicity caused by didanosine on cultured dorsal root ganglion neurons

The purpose of the present study was to investigate whether didanosine (ddI) directly causes morphological and ultrastructural abnormalities of dorsal root ganglion (DRG) neurons in vitro. Dissociated DRG cells and organotypic DRG explants from embryonic 15-day-old Wistar rats were cultured for 3 days and then exposed to ddI (1 microg/ml, 5 microg/ml, 10 microg/ml, and 20 microg/ml) for another 3 days and 6 days, respectively. Neurons cultured continuously in medium served as normal controls. The diameter of the neuronal cell body and neurite length were measured in dissociated DRG cell cultures. Neuronal ultrastructural changes were observed in both culture models. ddI induced dose-dependent decreases in neurite number, length of the longest neurite in each neuron, and total neurite length per neuron in dissociated DRG cell cultures with 3 days treatment. There were no morphological changes seen in organotypic DRG cultures even with longer exposure time (6 days). But ddI induced ultrastructural changes in both culture models. Ultrastructural abnormalities included loss of cristae in mitochondria, clustering of microtubules and neurofilaments, accumulation of glycogen-like granules, and emergence of large dense particles between neurites or microtubules. Lysosome-like large particles emerged inconstantly in neurites. ddI induced a neurite retraction or neurite loss in a dose-dependent manner in dissociated DRG neurons, suggesting that ddI may partially contribute to developing peripheral neuropathy. Cytoskeletal rearrangement and ultrastructural abnormalities caused by ddI in both culture models may have a key role in neurite degeneration.

Pharmacogenetic Considerations in the Management of HIV Infection

Potent combination antiretroviral drug therapy has now been available to HIV-infected patients for more than a decade, resulting in a significant decline in disease-related morbidity and mortality. Nonetheless, a number of HIV-infected individuals fail to experience the full benefit of their antiretroviral medications; some lack a robust virologic response, while others experience treatment-limiting toxicities. A number of factors may contribute to variable drug response in patients with HIV infection. Virologic, immunologic, pharmacologic, and pharmacokinetic differences between HIV-infected patients have all been noted to contribute to interpatient variability in drug response. Recent data suggest that pharmacogenetic differences among HIV-infected individuals may also be an important variable that contributes to antiretroviral drug response. Pharmacogenetic studies of antiretroviral drug therapy have explored the influence of single nucleotide polymorphisms in genes responsible for key proteins involved in antiretroviral drug metabolism (cytochrome P50 enzymes) and drug transport (P-glycoprotein). In addition, the human leukocyte antigen genotype (HLA-B*57) has been found to predict abacavir-associated hypersensitivity reactions. Antiretroviral pharmacogenetics offers the possibility of optimizing virologic response and minimizing drug toxicity by individualizing anti-HIV pharmacotherapy. The authors review those genetic polymorphisms that have been shown, or are strongly suspected, to influence antiretroviral drug metabolism, transport, and toxicity.