The Journal of Infectious Diseases May 1 2005;191:1397-1400

David W. Haas

Departments of Medicine, Microbiology, and Immunology, and Center for Human Genetics Research, Vanderbilt University School of Medicine, Nashville, Tennessee

(See the article by Tarr et al., below.) LIPID DISORDERS PATIENT GENETICS. Authors find: "….Variant alleles of APOE and APOC3 contribute to an unfavorable lipid profile in patients with HIV. Interactions between genotypes and ART can lead to severe hyperlipidemia. Genetic analysis may identify patients at high risk for severe ritonavir-associated hypertriglyceridemia…."

AIDS offers perhaps the greatest threat to humans by any infectious disease in history. In response to this challenge, at least 19 distinct antiretroviral agents that target HIV reverse transcriptase, protease, or viral entry have been approved for clinical use. Such a broad armamentarium is critical, given the nature of antiretroviral therapy, which requires the lifelong administration of multiple drugs. Use of these medications greatly reduces AIDS-related mortality [1], but their efficacy is often compromised by their toxicity, viral resistance, and incomplete adherence to treatment, as well as by comorbidities, such as viral hepatitis, diabetes, and cardiovascular disease.

The field of pharmacogenomics strives to understand relationships between human genetic variation and responses to treatment [2—6]. The relevance of pharmacogenomics to HIV therapeutics spans basic science, patient care, and public health disciplines. Laboratory-based investigators use genomic techniques to study viral pathogenesis in the hope of identifying new cellular targets for therapeutic intervention. Standard HIV clinical practice may soon include human genetic testing to help individualize antiretroviral therapy. From a public health perspective, as antiretroviral medications become increasingly available to racially and ethnically diverse populations worldwide, understanding the genetic structures of each population may allow us to anticipate the impact of adverse responses, even in groups that were not represented in drug registration trials.

The potential for human genetic research to identify novel therapeutic targets is highlighted by previous studies of CCR5. This cellular chemokine receptor is required for infectivity of many HIV strains [7—9]. Soon after its role in HIV replication was elucidated, individuals were identified who were highly resistant to HIV infection and lacked functional CCR5 as the result of a 32-bp deletion in the CCR5 gene but were otherwise healthy [10—12]. This experiment of nature suggested that CCR5 inhibitors could be particularly attractive antiretroviral agents, and several CCR5 inhibitors are now being studied in clinical trials. As other cellular factors that restrict HIV replication, such as apolipoprotein B mRNA-editing enzyme, catalytic polypeptide—like 3G (APOBEC3G) [13] and tripartite motif 5α (TRIM5α) [14], are discovered, the identification of naturally occurring variants in these and associated genes that influence the progression of HIV disease may suggest additional new targets for drug development.

Progress in pharmacogenomics requires that accomplished genomic investigators have access to DNA specimens from large, well-characterized patient populations. DNA banks that are associated with clinical trials and cohorts must therefore be established. The Adult AIDS Clinical Trials Group (AACTG), funded by the National Institutes of Health, has created an important repository. Since 1986, the AACTG has enrolled >36,000 individuals into diverse prospective trials that have well-defined entry criteria and on-study evaluations. To establish a usable DNA bank, a group of clinical researchers, genetic investigators, ethicists, statisticians, data managers, regulatory specialists, and community representatives worked in collaboration to develop AACTG Protocol A5128, which allows the use of stored DNA for studies that were not planned when informed consent was provided for other AACTG trials [15].

Since 2001, 〜7500 different participants in these clinical trials–19% female, 51% white, 28% black, and 18% Hispanic–have contributed specimens to the AACTG Human DNA Repository under A5128, and accrual is ongoing. Because its specimens have an average yield of 〜400 μg of extracted DNA, this repository can support an almost unlimited number of projects. One challenge for the identification of genetic associations in cohort studies is to define control groups that share all relevant factors except phenotype [16]. Because most AACTG studies are randomized, approximately equal numbers of subjects with a given genotype are likely to be assigned to different treatments. The AACTG encourages proposals to utilize this resource for studies relevant to HIV infection and its complications, and a well-established procedure for the consideration of such proposals is in place.

In this issue of the Journal of Infectious Diseases, Tarr et al. describe an association between variant alleles of APOE and APOC3 and protease inhibitor—associated hyperlipidemia in participants in the Swiss HIV Cohort Study [17]. Their study expands the number of putative associations between human genetic variants and responses to antiretroviral therapy.

To date, the most impressive such association regards hypersensitivity to abacavir. Although the drug is generally well tolerated, 5%—9% of whites who receive abacavir experience hypersensitivity reactions that can be life threatening. Two research groups independently reported an association between major histocompatibility complex alleles and hypersensitivity to abacavir [18, 19]. In patients exposed to abacavir in Perth, Australia, the presence of HLA-B*5701, HLA-DR7, and HLA-DQ3 had a positive predictive value of 100% and a negative predictive value of 97% for hypersensitivity [18]. An association between hypersensitivity to abacavir and HLA-B*5701 and HLA-DR7 was confirmed in patients in North America [19]. More-recent analyses have extended this association to include a polymorphism in Hsp70-Hom, a member of the heat shock protein family of chaperonins [20]. In western Australia, the routine screening of patients' genetic makeup before they are prescribed abacavir has markedly reduced the incidence of hypersensitivity reactions. Such screening is rarely performed in the United States.

The nonnucleoside reverse-transcriptase inhibitor efavirenz is one of the most widely prescribed antiretroviral medications [21, 22], but many recipients of efavirenz experience central nervous system side effects during the initial weeks of therapy [22—24]. Efavirenz is metabolized primarily by hepatic cytochrome P450 (CYP) 2B6 [25], and a large amount of interindividual variability in the amount of CYP2B6 in the liver has been reported [26—29], as have functional differences between genetic variants [28, 30—32]. Specimens from the AACTG Human DNA Repository and associated data from clinical trials were used to show that a CYP2B6 exon 4 polymorphism that occurs more frequently in blacks than in whites is associated with 〜3-fold higher plasma concentrations of efavirenz (P < .0001) and with increased central nervous system side effects (P = .036) [33]. Differences in the frequency of this polymorphism in different populations may explain the lower clearance of efavirenz noted in blacks [34—36]. Additional studies are needed to assess the implications for long-term responses to efavirenz, as well as to nevirapine, which is also metabolized by CYP2B6 [37, 38].

Peripheral fat wasting and central fat deposition often complicate antiretroviral therapy. Independent risk factors for antiretroviral-associated lipoatrophy include white race and prolonged exposure to nucleoside analogues, particularly stavudine [39]. Tumor necrosis factor (TNF)—α has been implicated in the pathogenesis of lipodystrophy [40, 41], and TNF-α expression varies according to race and ethnicity [42]. At least 2 research groups have reported relationships between antiretroviral-associated lipodystrophy and a TNF-α promoter polymorphism that may affect gene expression. In 96 white patients in England, a TNF-α position -238 polymorphism was present only in subjects with lipodystrophy (P = .01) [43]. Similarly, in 191 white patients in Australia, all of whom had lipoatrophy, this polymorphism was associated with a more-rapid onset of fat wasting (P = .014) [44]. Although these findings support a role for TNF-α in the pathogenesis of lipoatrophy, this variant allele may simply be a marker for other genes with which it is linked, such as members of the major histocompatibility complex [42].

Bilirubin is the primary product of heme metabolism. Its efficient elimination requires conjugation with glucuronic acid in a reaction catalyzed by hepatic UDP-glucuronosyltransferase (UGT) 1A1. Approximately 5%—10% of individuals have decreased bilirubin-conjugating activity that is caused by a TA insertion into the UGT1A1 promoter (Gilbert syndrome) [45, 46]. The HIV protease inhibitors indinavir and atazanavir commonly cause unconjugated hyperbilirubinemia by competing with bilirubin for binding to UGT1A1. Although the condition is usually asymptomatic, some patients discontinue treatment with these drugs because of jaundice. In a study of 15 HIV-positive men receiving indinavir, mean increases in serum bilirubin levels were significantly greater in patients with at least 1 Gilbert polymorphism (P = .012) [47]. Similarly, of 138 healthy volunteers who participated in phase 1 studies of atazanavir, those homozygous for the Gilbert genotype had significantly higher median total bilirubin levels than did heterozygous or wild-type subjects (P = .0001) [48]. Fortunately, not all patients with Gilbert syndrome who receive atazanavir or indinavir experience marked elevations in bilirubin levels.

The HIV protease inhibitors are substrates for P-glycoprotein, the multidrug efflux pump encoded by MDR1 [49—54], and a frequent MDR1 exon 26 polymorphism has been associated with altered P-glycoprotein expression [55]. P-glycoprotein in the intestine, liver, and kidney is predicted to decrease oral bioavailability of these drugs and enhance their elimination. P-glycoprotein is also present in CD4 T cells [56], and its expression in the brain limits entry of protease inhibitors [51]. Importantly, a provocative report noted an association between the MDR1 exon 26 polymorphism, increases in CD4 T cells in response to antiretroviral therapy, and plasma concentrations of efavirenz and nelfinavir [57]. Subsequent studies, however, have not confirmed these findings [33, 58, 59]. Genetic associations suggested by initial studies are often not confirmed by subsequent analyses [60], and the relevance of MDR1 polymorphisms for HIV therapeutics remains uncertain.

As pharmacogenomics moves from bench to bedside, most genotype-phenotype relationships will reflect the combined influences of multiple genes and polymorphisms. The growing number of identified genetic associations will increase the impetus to make human genetic testing a routine part of HIV clinical care. Prospective clinical trials will ultimately be needed to determine whether the use of human genetic testing to guide the administration of antiretroviral therapy results in an improved response to treatment. Because genetic variants are stable throughout one's lifetime, genetic testing performed on a single occasion could potentially inform every subsequent treatment decision for a patient, and this makes such an approach to HIV clinical care even more attractive.

Philip E. Tarr,1 Patrick Taffé,3 Gabriela Bleiber,2 Hansjakob Furrer,5 Margalida Rotger,2 Raquel Martinez,2 Bernard Hirschel,8 Manuel Battegay,9 Rainer Weber,6 Pietro Vernazza,7 Enos Bernasconi,10 Roger Darioli,4 Martin Rickenbach,3 Bruno Ledergerber,6 Amalio Telenti,1,2 and the Swiss HIV Cohort Studya

1Infectious Diseases Service, University Hospital, 2Institute of Microbiology, University of Lausanne, 3Swiss HIV Cohort Study Data Center, and 4Lipidology, University Medical Policlinic, Lausanne, and 5Infectious Diseases, University Hospital, Bern, 6Infectious Diseases, University Hospital, Zurich, 7Infectious Diseases, Kantonsspital, St. Gallen, 8Infectious Diseases, University Hospital, Geneva, 9Infectious Diseases, University Hospital, Basel, and 10Ospedale Civico, Lugano, Switzerland

Background. Single-nucleotide polymorphisms in genes involved in lipoprotein and adipocyte metabolism may explain why dyslipidemia and lipoatrophy occur in some but not all antiretroviral therapy (ART)—treated individuals.

Methods. We evaluated the contribution of APOC3 -482C→T, -455T→C, and 3238C→G;e 2 ande 4 alleles of APOE; and TNF -238G→A to dyslipidemia and lipoatrophy by longitudinally modeling >2600 lipid determinations and 2328 lipoatrophy assessments in 329 ART-treated patients during a median follow-up period of 3.4 years.

Results. In human immunodeficiency virus (HIV)—infected individuals, the effects of variant alleles of APOE on plasma cholesterol and triglyceride levels and of APOC3 on plasma triglyceride levels were comparable to those reported in the general population. However, when treated with ritonavir, individuals with unfavorable genotypes of APOC3 or APOE were at risk of extreme hypertriglyceridemia. They had median plasma triglyceride levels of 7.33 mmol/L, compared with 3.08 mmol/L in the absence of ART. The net effect of the APOE*APOC3*ritonavir interaction was an increase in plasma triglyceride levels of 2.23 mmol/L. No association between TNF -238G→A and lipoatrophy was observed.

Conclusions. Variant alleles of APOE and APOC3 contribute to an unfavorable lipid profile in patients with HIV. Interactions between genotypes and ART can lead to severe hyperlipidemia. Genetic analysis may identify patients at high risk for severe ritonavir-associated hypertriglyceridemia.

Adverse metabolic effects of potent antiretroviral therapy (ART) have become a major concern. Hyperlipidemia increases the risk of cardiovascular disease [1]. Lipoatrophy may stigmatize the patient and is associated with insulin resistance and hyperlipidemia [2, 3]. Both hyperlipidemia and lipoatrophy have been linked to advancing age, male sex, a CD4 T cell count <200 cells/μL, and the type of ART used [2,4]. The use of ritonavir (RTV) and RTV-boosted protease inhibitors (PIs) are the most significant predictors of hypercholesterolemia and hypertriglyceridemia [4], whereas use of stavudine (d4T), didanosine (ddI), and, in some studies, PIs are associated with lipoatrophy [2]. However, these complications do not occur in all patients, despite similar exposure to ART and comparable demographic, immunologic, and virologic characteristics. The reasons for this discrepancy may be related to host genetic factors.

Single-nucleotide polymorphisms (SNPs) in APOE (specifically the APOEe 4 ande 2 alleles) are linked to hyperlipidemia and cardiovascular events [5] in the general population. SNPs of APOC3 at positions -455 and -482 in the promoter region and at position 3238 in the 3′ untranslated region (the SstI allele) are associated with hypertriglyceridemia [6, 7]. A SNP at position -238 in the promoter region of TNF (previous designation, TNF-α) has been linked to the more-rapid onset of lipoatrophy in ART-treated patients [8], and the rare allele was found to be present more frequently in patients with HIV who have lipoatrophy than in those who do not have the condition [9]. The APOE genotype may be functionally associated with hyperlipidemia, as the role of APOE in the transport and clearance of lipoprotein remnants from the bloodstream would suggest [5]. Through the inhibition of the activity of lipoprotein lipase, APOC3 modulates lipolysis and hepatic clearance of plasma triglycerides (TGs) [6, 7]. TNF expression in adipose tissue has been implicated in lipoatrophy because of its modulation of lipolysis and adipocyte differentiation [10]. Most reports on the metabolic complications associated with APOE and APOC3 polymorphisms have been based on studies of the general population. In HIV-infected individuals, the interpretation of the data has been limited by the small number of patients studied [11, 12], contradictory findings regarding a link between APOE genotype and hyperlipidemia [12—14], and a focus on PI-treated men [13—15]. The present study used a longitudinal approach to model the influence of APOE and APOC3 polymorphisms on ART-associated hyperlipidemia, as well as the influence of the TNF -238 polymorphism on lipoatrophy, in the context of frequent changes of therapy and other contributing factors.

We report on the identification of a significant genotype-ART interaction that may lead to severe hyperlipidemia in HIV-infected patients treated with ART. Known genetic variants in APOC3 and APOE contributed significantly to elevations in plasma TG levels to a degree comparable to factors such as age or the use of RTV-containing ART. However, the effect of unfavorable APOC3 alleles was observed only in patients who received ART. Variant alleles of APOC3 and APOE had no significant effect on plasma HDL cholesterol levels, whereas the effect of variant alleles of APOE on plasma NHC levels was additive to that of single-PI ART. Our results extend the findings reported by Fauvel et al. [13], who documented an association between variant alleles of APOC3 and hypertriglyceridemia in 60 men treated with PIs.

The most relevant finding of our study is the identification of a complex genotype-ART interaction that may lead to extreme hypertriglyceridemia when individuals with an unfavorable composite APOC3-APOE genotype are exposed to RTV. Such a phenotypic expression of a latent genetic predisposition to hyperlipidemia has been reported by Rodondi et al. [18]. In this pharmacogenetic study, these authors identified an elevated risk of future hyperlipidemia in APOE &epsiv;2 and &epsiv;4 carriers who developed hypertriglyceridemia during retinoic acid treatment for acne. Conversely, patients who did not have elevations in their plasma TG levels during retinoic acid therapy seemed to be protected against future hyperlipidemia.

We did not identify a genetic predisposition to lipoatrophy in patients in our data set who had the TNF -238G→A polymorphism. This is in contrast to the findings of 2 other studies [8, 9]. Nolan et al. [8] used a time-to-event model to evaluate the occurrence of lipoatrophy in 191 white men. The frequency of the rare allele (f = 0.065) was higher than that in the present study (f = 0.035). After 2 years of follow-up, the effect of the TNF polymorphism was modest in the study by Nolan et al., but the effect became more pronounced over time. It is possible that we might identify a significant effect of TNF -238G→A with an extended follow-up period. The greater diagnostic accuracy in the study by Nolan et al. [8] (by the use of radiological assessments of body composition) may further explain the differences between the results of the studies. Although there was an association between lipoatrophy and variant alleles of APOC3, the biological mechanism is unclear, and this association needs to be confirmed in other patient populations before it can be considered a true finding.

Longitudinal modeling represents a powerful approach to quantitating the individual contribution of genetic factors and effects of ART in the context of complex traits. We exploited prospectively collected data consisting of >2600 lipid determinations in 329 individuals, during a study period of >3 years. This allowed us to evaluate the influence of the polymorphisms in APOC3 and APOE as well as multiple intervening factors of relevance to plasma lipid levels (age, sex, ethnicity, smoking status, mode of HIV transmission, ART group, CD4 T cell count, HIV viremia, BMI, fasting state, treatment with lipid-lowering agents, and diabetes mellitus status). The study patients served as their own controls, through multiple changes in ART and periods when ART was not used. This approach was selected in response to the well-recognized dilemmas in genetic association studies, which regard, particularly, the issues of statistical power, phenotype definition, and the use of appropriate statistical tools. We also attempted a conventional matched control analysis using a single time point, which proved underpowered for identification of the genetic effects. Potential bias arising from overrepresentation of subjects with high plasma lipid levels seems unlikely, because we found that the frequency of determinations was comparable in subjects with low and high plasma lipid levels.

The relatively high frequency of variant alleles of APOE and APOC3 might suggest a potential role for genetic testing before initiation of ART. This merits formal evaluation in a randomized trial. For example, 27.7% of patients in this study were carriers of variant alleles of APOE, 17.9% were carriers of all 3 variant alleles of APOC3, and 5.8% were carriers of both. The genotyping of treatment-naive patients might be an efficient method to determine the advisability of the administration of RTV-containing ART. Given the risk of hypertriglyceridemia, it might be prudent to select an alternative ART regimen for patients who have unfavorable genotypes.

Patients. Study participants were followed in the Swiss HIV Cohort Study (SHCS) (http://www.shcs.ch) and were treated for HIV infection at 1 of 7 Swiss medical centers. The genetics project of the SHCS was approved by the ethics committees of all participating centers. Patients were included if they had given written, informed consent for genetic testing.

Lipid determinations included the routine assessments of plasma total cholesterol, high-density lipoprotein (HDL) cholesterol, and TG levels. The level of non-HDL cholesterol (NHC) was calculated by subtracting the level of HDL cholesterol from the level of total cholesterol. Patients who had a Centers for Disease Control and Prevention stage C AIDS-defining event in the preceding 3 months or a CD4 T cell count <100 cells/μL were excluded, to limit confounding by HIV-associated wasting and opportunistic illness. Lipoatrophy was defined by the patient-reported presence of fat loss at &ges;1 body site (face, neck, arms, legs, or buttocks) that was confirmed by the physician on physical examination. No lipoatrophy assessments were made by use of computed tomography scanning or dual-energy x-ray absorptiometry. The fasting state (with fasting defined as >8 h without caloric intake) was recorded each time that a blood sample was taken.

Patients. The clinical characteristics of the study patients (n = 329) are summarized in table 2. We compared their characteristics with those of the entire population of patients enrolled in the SHCS who had >1 follow-up visit during 1999—2003 (n = 6724). Compared with this population of the SHCS, the study patients were more likely to have suppressed HIV viremia, the duration of their follow-up period was longer, and there were fewer deaths and dropouts. These characteristics define the selection bias of patients in the SHCS Genetic Cohort, who were chosen for the quality of their clinical documentation and their ability to sign the consent form for genetic analysis.

The allelic frequencies were as follows: APOC3 -455T→C, 0.410; APOC3 -482C→T, 0.303; APOC3 3238C→G, 0.092; APOE 2060T→C, 0.093; APOE 2198C→T, 0.055; and TNF 238G→A, 0.035. These were comparable to the published allelic frequencies in ethnically similar populations [28]. The distribution of the genotypes was as follows: APOEe 3/e 3, 238 patients (72.3%); APOE genotypes other thane 3/e 3, 91 patients (27.7%;e 2/e 2, 2/e 3, ore 2/e 4, 35 patients [10.6%];e 3/e 4 ore 4/e 4, 56 patients [17.0%]); common alleles of APOC3, 120 patients (36.5%); 1 or 2 variant alleles of APOC3, 150 patients (45.6%); and all 3 variant alleles of APOC3, 59 patients (17.9%).

During the follow-up period, a total of 2608 determinations of plasma cholesterol (both HDL and NHC) levels (mean, 7.4 determinations of plasma cholesterol levels/patient) and 2741 determinations of plasma TG levels (mean, 7.8 determinations of plasma TG levels/patient) were recorded (range, 3—18 total lipid determinations/patient). The mean number of determinations of plasma TG levels during the follow-up period was comparable in subjects with low and high median plasma TG levels (patients with low median plasma TG levels, 7.97 determinations/patient; patients with high median plasma TG levels, 8.25 determinations/patient); the median number of determinations was identical (7 determinations/patient). Thus, potential bias due to overrepresentation of subjects with high plasma TG levels is unlikely. The median plasma lipid levels during the follow-up period are shown in table 2. Results were unchanged when plasma lipid levels in patients who had an AIDS-defining event in the preceding 3 months or a CD4 T cell count <100 cells/μL were included.

Effects of ART regimen on plasma lipid levels. There were a total of 9169 determinations of the type of ART regimen in use during the study period. No ART was in use at 1078 (11.8%) time points. PI-sparing ART, single-PI ART, and RTV-containing ART were in use at 2965 (32.3%), 3242 (35.4%), and 1884 (20.5%) time points, respectively. The influence of ART regimen on plasma lipid levels is summarized in table 3. The population-averaged plasma HDL cholesterol level was higher in patients treated with PI-sparing ART (P = .006). The plasma NHC level was lower in patients treated with PI-sparing ART (P = .019) and higher in patients treated with single-PI ART (P = .01) or RTV-containing ART (P < .001). Plasma TG levels were significantly higher only in patients treated with RTV-containing ART (P < .001). Because RTV can be used at different dosages, we compared plasma TG levels in patients treated with RTV alone (600 mg of RTV twice daily) or in combination with lopinavir (100 mg of RTV twice daily) or saquinavir (400 mg of RTV twice daily). The median plasma TG levels during the follow-up period in these 3 groups of patients were comparable (3.19 vs. 3.00 vs. 2.89 mmol/L, respectively; P = .63). Thus, patients treated with RTV were analyzed as a single group. As was reported elsewhere [29], there was a trend toward higher mean plasma TG levels in patients treated with PI-sparing ART that contained efavirenz (0.47 mmol/L [95% confidence interval {CI}, -0.08 to 1.02 mmol/L] increase in plasma TG levels; P = .09).

Effects of variant alleles on plasma TG levels. APOE genotypes other than the common When patients were exposed to RTV, extreme hypertriglyceridemia (defined as at least 2 determinations at which plasma TG levels were above the 95th percentile of the study population [&ges;7.0 mmol/L]) was recorded in 4 (15.4%) of 26 patients who had common alleles of APOE and APOC3, in 3 (20.0%) of 15 patients who had all 3 variant alleles of APOC3 and common alleles of APOE, in 1 (11.1%) of 9 patients who had APOE non-&epsiv;3/&epsiv;3 genotypes and common alleles of APOC3, but in 6 (60.0%) of 10 patients who had the unfavorable composite genotype (P = .026). The TNF -238G→A polymorphism had no effect on plasma TG levels (P = .973).

The most unfavorable composite genotype consisted of APOE genotypes other thane 3/e 3 plus all 3 variant alleles of APOC3. The predicted net effect of the APOE*APOC3 interaction was a mean 1.24 mmol/L (95% CI, 0.45—2.03 mmol/L) increase in plasma TG levels (P = .02). This unfavorable composite genotype was associated with elevations of plasma TG levels in patients in all ART groups; however, the most striking genotype-ART interaction was observed when patients who had the unfavorable composite genotype were treated with RTV-containing ART (figure 1). Here, the predicted net effect of the APOE*APOC3*RTV interaction was a mean 2.23 mmol/L (95% CI, 1.33—3.14 mmol/L) increase in plasma TG levels (P < .001). These estimates represent the contribution of the interactions in addition to the specific effects of the covariables listed in table 3. Thus, the mean plasma TG level in patients who had the unfavorable composite genotype was 3.08 mmol/L if no ART was used and increased to 7.33 mmol/L when RTV was used in the regimen (P < .001).

When patients were exposed to RTV, extreme hypertriglyceridemia (defined as at least 2 determinations at which plasma TG levels were above the 95th percentile of the study population [>7.0 mmol/L]) was recorded in 4 (15.4%) of 26 patients who had common alleles of APOE and APOC3, in 3 (20.0%) of 15 patients who had all 3 variant alleles of APOC3 and common alleles of APOE, in 1 (11.1%) of 9 patients who had APOE non-e 3/e 3 genotypes and common alleles of APOC3, but in 6 (60.0%) of 10 patients who had the unfavorable composite genotype (P = .026). The TNF -238G→A polymorphism had no effect on plasma TG levels (P = .973).

An additional, single-time-point, cross-sectional analysis of 75 patients who had plasma TG levels >2.3 mmol/L and 75 control subjects who had normal plasma TG levels and were matched to patients by age, BMI, sex, and ART group was underpowered for detection of the deleterious effects of variant alleles of APOC3 or APOE. For example, individuals who had APOE non-e 3/e 3 genotypes had an odds ratio of 1.41 (95% CI, 0.65—3.06) for the development of hypertriglyceridemia (P = .379).

Effects of variant alleles on plasma NHC and HDL cholesterol levels. Thee 3/e 4 ande 4/e 4 APOE genotypes were associated with elevated plasma NHC levels (P = .038). As expected, the APOE genotype had no influence on plasma HDL cholesterol levels. There was a trend toward lower plasma NHC levels in patients who had 1 or 2 variant alleles of APOC3 (P = .088) and in patients who had all 3 variant alleles (P = .052). No significant interaction between various genotypes and ART group were identified (table 4). No effect of the TNF -238G→A polymorphism on either plasma HDL cholesterol levels or plasma NHC levels was seen (P = .592 and P = .881, respectively).

Lipid-lowering agents were given more frequently to patients who had APOE genotypes other thane 3/e 3 (12.2% of determinations) and to patients who had variant alleles of APOC3 (10.8% of determinations) than to patients who had the APOE &epsiv;3/&epsiv;3 genotype (8.7% of determinations) (P = .007) or to patients who had the common alleles of APOC3 (7.6%) (P = .023); the models were adjusted for treatment with lipid-lowering agents.

Lipoatrophy. A total of 2328 assessments of lipoatrophy (mean, 7.1 assessments/patient; range, 3—9 assessments/patient) were made during the follow-up period in 325 patients. The prevalence of lipoatrophy was 25.2%. Baseline age (P = .004), BMI (P = .016), and waist circumference (P = .004) were associated with lipoatrophy (table 5). Lipoatrophy was associated with cumulative exposure to ddI/d4T, irrespective of the associated use of a PI (P < .001). Exposure to a PI in the absence of ddI and/or d4T was not associated with lipoatrophy (P = .153). The odds ratio for the development of lipoatrophy was higher in patients who had 3 variant alleles of APOC3 (P = .046) but was not higher in patients who had the TNF -238G→A polymorphism (P = .625).