Determinants of virological outcome and adverse events in African children treated with paediatric nevirapine fixed-dose-combination tablets.

BACKGROUND: Nevirapine is the only nonnucleoside reverse transcriptase inhibitor currently available as a paediatric fixed-dose-combination tablet and is widely used in African children. Nonetheless, the number of investigations into pharmacokinetic determinants of virological suppression in African children is limited, and the predictive power of the current therapeutic range was never evaluated in this population, thereby limiting treatment optimization. METHODS: We analysed data from 322 African children (aged 0.3-13 years) treated with nevirapine, lamivudine, and either abacavir, stavudine, or zidovudine, and followed up to 144 weeks. Nevirapine trough concentration (Cmin) and other factors were tested for associations with viral load more than 100 copies/ml and transaminase increases more than grade 1 using proportional hazard and logistic models in 219 initially antiretroviral treatment (ART)-naive children. RESULTS: Pre-ART viral load, adherence, and nevirapine Cmin were associated with viral load nonsuppression [hazard ratio = 2.08 (95% confidence interval (CI): 1.50-2.90, P < 0.001) for 10-fold higher pre-ART viral load, hazard ratio = 0.78 (95% CI: 0.68-0.90, P < 0.001) for 10% improvement in adherence, and hazard ratio = 0.94 (95% CI: 0.90-0.99, P = 0.014) for a 1 mg/l increase in nevirapine Cmin]. There were additional effects of pre-ART CD4 cell percentage and clinical site. The risk of virological nonsuppression decreased with increasing nevirapine Cmin, and there was no clear Cmin threshold predictive of virological nonsuppression. Transient transaminase elevations more than grade 1 were associated with high Cmin (>12.4 mg/l), hazard ratio = 5.18 (95% CI 1.95-13.80, P < 0.001). CONCLUSION: Treatment initiation at lower pre-ART viral load and higher pre-ART CD4 cell percentage, increased adherence, and maintaining average Cmin higher than current target could improve virological suppression of African children treated with nevirapine without increasing toxicity.

Effect of diurnal variation, CYP2B6 genotype and age on the pharmacokinetics of nevirapine in African children.

OBJECTIVES: To characterize the effects of CYP2B6 polymorphisms, diurnal variation and demographic factors on nevirapine pharmacokinetics in African children. METHODS: Non-linear mixed-effects modelling conducted in NONMEM 7.3 described nevirapine plasma concentration-time data from 414 children aged 0.3-15 years. RESULTS: Nevirapine pharmacokinetics was best described using a one-compartment disposition model with elimination through a well-stirred liver model accounting for a first-pass effect and transit-compartment absorption. Intrinsic clearance was affected by diurnal variation (characterized using a cosine function with peak amplitude 29% at 12 noon) and CYP2B6 metabolizer status [extensive metabolizer (EM) 516GG|983TT, reference; intermediate metabolizer (IM) 516GT|983TT or 516GG|983TC, 17% lower; slow metabolizer (SM) 516TT|983TT or 516GT|983TC, 50% lower; ultra-slow metabolizer (USM) 516GG|983CC, 68% lower]. Age was found to affect pre-hepatic bioavailability: 31.7% lower at birth and increasing exponentially. Median (90% CI) evening Cmin values in the different metabolizer groups were 5.01 (3.01-7.47), 6.55 (3.65-13.32), 11.59 (5.44-22.71) and 12.32 (12.32-27.25) mg/L, respectively. Evening Cmin values were <3 mg/L in 43% of EM weighing <6 kg and 26% of IM weighing <6 kg, while 73% of SM and 88% of USM in all weight-bands had evening Cmin values >8 mg/L. Cmin was not markedly affected by administration time, but was altered by unequal splitting of the daily dose. CONCLUSIONS: Diurnal variation does not greatly affect nevirapine exposure. However, when daily doses cannot be split equally, the larger dose should be given in the morning. To achieve homogeneous exposures, nevirapine doses for SM and USM should be reduced by 50%, and children weighing <6 kg with EM or IM metabolizer status should receive the same dose as children weighing 6-10 kg.

Plasma Efavirenz Exposure, Sex, and Age Predict Virological Response in HIV-Infected African Children.

BACKGROUND: Owing to insufficient evidence in children, target plasma concentrations of efavirenz are based on studies in adults. Our analysis aimed to evaluate the pediatric therapeutic thresholds and characterize the determinants of virological suppression in African children. METHODS: We analyzed data from 128 African children (aged 1.7-13.5 years) treated with efavirenz, lamivudine, and one among abacavir, stavudine, or zidovudine, and followed up to 36 months. Individual pharmacokinetic (PK) measures [plasma concentration 12 hours after dose (C12h), plasma concentration 24 hours after dose (C24h), and area under the curve (AUC0-24)] were estimated using population PK modeling. Cox multiple failure regression and multivariable fractional polynomials were used to investigate the risks of unsuppressed viral load associated with efavirenz exposure and other factors among 106 initially treatment-naive children, and likelihood profiling was used to identify the most predictive PK thresholds. RESULTS: The risk of viral load >100 copies per milliliter decreased by 42% for every 2-fold increase in efavirenz mid-dose concentration [95% confidence interval (CI): 23% to 57%; P < 0.001]. The most predictive PK thresholds for increased risk of unsuppressed viral load were C12h 1.12 mg/L [hazard ratio (HR): 6.14; 95% CI: 2.64 to 14.27], C24h 0.65 mg/L (HR: 6.57; 95% CI: 2.86 to 15.10), and AUC0-24 28 mg·h/L (HR: 5.77; 95% CI: 2.28 to 14.58). Children older than 8 years had a more than 10-fold increased risk of virological nonsuppression (P = 0.005); among children younger than 8 years, boys had a 5.31 times higher risk than girls (P = 0.007). Central nervous system adverse events were infrequently reported. CONCLUSIONS: Our analysis suggests that the minimum target C24h and AUC0-24 could be lowered in children. Our findings should be confirmed in a prospective pediatric trial.

The impact of genetic polymorphisms on the pharmacokinetics of efavirenz in African children.

AIMS: Using a model-based approach, the efavirenz steady-state pharmacokinetics in African children is characterized, quantifying demographic and genotypic effects on the drug's disposition. Simulations are also conducted allowing prediction of optimized doses of efavirenz in this population. METHODS: We modelled the steady-state population pharmacokinetics of efavirenz in Ugandan and Zambian children using nonlinear mixed-effects modelling. Individual mid-dose efavirenz concentrations were derived and simulations explored genotype-based dose optimization strategies. RESULTS: A two-compartment model with absorption through transit compartments well described 2086 concentration-time points in 169 children. The combined effect of single nucleotide polymorphisms (SNPs) 516G>T and 983T>C explained 44.5% and 14.7% of the variability in efavirenz clearance and bioavailability, respectively. The detected frequencies of composite CYP2B6 genotype were 0.33 for 516GG|983TT, 0.35 for 516GT|983TT, 0.06 for 516GG|983TC, 0.18 for 516TT|983TT, 0.07 516GT|983TC and 0.01 for 516GG|983CC. The corresponding estimated clearance rates were 6.94, 4.90, 3.93, 1.92, 1.36, and 0.74 l h(-1) for a 15.4 kg child and median (95% CI) observed mid-dose concentrations 1.55 (0.51-2.94), 2.20 (0.97-4.40), 2.03 (1.19-4.53), 7.55 (2.40-14.74), 7.79 (3.66-24.59) and 18.22 (11.84-22.76) mg l(-1) , respectively. Simulations showed that wild-type individuals had exposures at the bottom of therapeutic range, while slower metabolizers were overexposed. CONCLUSIONS: Dosage guidelines for African children should take into consideration the combined effect of SNPs CYP2B6 516G>T and 983T>C.

Predicting patterns of long-term CD4 reconstitution in HIV-infected children starting antiretroviral therapy in sub-Saharan Africa: a cohort-based modelling study.

BACKGROUND: Long-term immune reconstitution on antiretroviral therapy (ART) has important implications for HIV-infected children, who increasingly survive into adulthood. Children's response to ART differs from adults', and better descriptive and predictive models of reconstitution are needed to guide policy and direct research. We present statistical models characterising, qualitatively and quantitatively, patterns of long-term CD4 recovery. METHODS AND FINDINGS: CD4 counts every 12 wk over a median (interquartile range) of 4.0 (3.7, 4.4) y in 1,206 HIV-infected children, aged 0.4-17.6 y, starting ART in the Antiretroviral Research for Watoto trial (ISRCTN 24791884) were analysed in an exploratory analysis supplementary to the trial's pre-specified outcomes. Most (n = 914; 76%) children's CD4 counts rose quickly on ART to a constant age-corrected level. Using nonlinear mixed-effects models, higher long-term CD4 counts were predicted for children starting ART younger, and with higher CD4 counts (p<0.001). These results suggest that current World Health Organization-recommended CD4 thresholds for starting ART in children ≥5 y will result in lower CD4 counts in older children when they become adults, such that vertically infected children who remain ART-naïve beyond 10 y of age are unlikely ever to normalise CD4 count, regardless of CD4 count at ART initiation. CD4 profiles with four qualitatively distinct reconstitution patterns were seen in the remaining 292 (24%) children. Study limitations included incomplete viral load data, and that the uncertainty in allocating children to distinct reconstitution groups was not modelled. CONCLUSIONS: Although younger ART-naïve children are at high risk of disease progression, they have good potential for achieving high CD4 counts on ART in later life provided ART is initiated following current World Health Organization (WHO), Paediatric European Network for Treatment of AIDS, or US Centers for Disease Control and Prevention guidelines. In contrast, to maximise CD4 reconstitution in treatment-naïve children >10 y, ART should ideally be considered even if there is a low risk of immediate disease progression. Further exploration of the immunological mechanisms for these CD4 recovery profiles should help guide management of paediatric HIV infection and optimise children's immunological development. Please see later in the article for the Editors' Summary.

Mortality in the year following antiretroviral therapy initiation in HIV-infected adults and children in Uganda and Zimbabwe.

BACKGROUND: Adult mortality in the first 3 months on antiretroviral therapy (ART) is higher in low-income than in high-income countries, with more similar mortality after 6 months. However, the specific patterns of changing risk and causes of death have rarely been investigated in adults, nor compared with children in low-income countries. METHODS: We used flexible parametric hazard models to investigate how mortality risks varied over the first year on ART in human immunodeficiency virus-infected adults (aged 18-73 years) and children (aged 4 months to 15 years) in 2 trials in Zimbabwe and Uganda. RESULTS: One hundred seventy-nine of 3316 (5.4%) adults and 39 of 1199 (3.3%) children died; half of adult/pediatric deaths occurred in the first 3 months. Mortality variation over year 1 was similar; at all CD4 counts/CD4%, mortality risk was greatest between days 30 and 50, declined rapidly to day 180, then declined more slowly. One-year mortality after initiating ART with 0-49, 50-99 or ≥ 100 CD4 cells/µL was 9.4%, 4.5%, and 2.9%, respectively, in adults, and 10.1%, 4.4%, and 1.3%, respectively, in children aged 4-15 years. Mortality in children aged 4 months to 3 years initiating ART in equivalent CD4% strata was also similar (0%-4%: 9.1%; 5%-9%: 4.5%; ≥ 10%: 2.8%). Only 10 of 179 (6%) adult deaths and 1 of 39 (3%) child deaths were probably medication-related. The most common cause of death was septicemia/meningitis in adults (20%, median 76 days) and children (36%, median 79 days); pneumonia also commonly caused child deaths (28%, median 41 days). CONCLUSIONS: Children ≥ 4 years and adults with low CD4 values have remarkably similar, and high, mortality risks in the first 3 months after ART initiation in low-income countries, similar to cohorts of untreated individuals. Bacterial infections are a major cause of death in both adults and children; targeted interventions could have important benefits.

Differences in factors associated with initial growth, CD4, and viral load responses to ART in HIV-infected children in Kampala, Uganda, and the United Kingdom/Ireland.

BACKGROUND: Few studies have directly compared response to antiretroviral therapy (ART) between children living in well-resourced and resource-limited settings. In resource-limited settings non-HIV contributors could reduce the beneficial effects of ART. We compare predictors of short-term immunological, virological, and growth response to ART in HIV-infected children in the United Kingdom/Ireland and Kampala. METHODS: We analyzed prospective cohort data from 54 UK/Irish hospitals (the Collaborative HIV Paediatric Study) and Mulago Hospital, Kampala, Uganda. Six- and 12-month responses are described among children initiating combination ART (> or = 3 drugs, > or = 2 classes). Six months post-ART, predictors of viral load (VL) suppression <400 copies/mL, CD4% increases > 10%, and height- and weight-for-age z-score increases > or = +0.5 were investigated using logistic regression. RESULTS: In all, 582 UK/Irish children (76% black African) were younger than 876 Kampala children at ART initiation (median 5.0 vs 7.6 years), with higher CD4% (14%, 8%), lower VL (172,491 and 346,809 copies/mL), and less stunting (-0.8, -2.8) and wasting (-0.6, -2.8). Post-ART, median 12-month changes in the United Kingdom/Ireland and Kampala in CD4% (+12%, +13%) and weight (+0.4, +0.5) were similar, but growth was less in Kampala (+0.20, +0.06, P < 0.001). Younger children in both cohorts had better immunological, weight, and growth responses (all P < 0.001). However, lower pre-ART CD4% predicted better immunological response in the United Kingdom/Ireland but poorer response in Kampala (heterogeneity P = 0.004). Although 70% children in both cohorts had suppressed < 400 copies/mL at 6 months, adolescents starting ART in the United Kingdom/Ireland had somewhat poorer VL responses than those in Kampala (P = 0.15). CONCLUSIONS: Overall immunological and virologic ART responses were similar in children in both cohorts. Poorer CD4 recovery in more immunosuppressed Kampala children and blunted growth responses likely reflect higher background malnutrition and infection rates in Uganda, suggesting the need for earlier HIV diagnosis, nutritional support, cotrimoxazole prophylaxis, and ART.

Action for child survival: elimination of Haemophilus influenzae type b meningitis in Uganda.

OBJECTIVE: To guide immunization policy, we determined the public health benefit of introducing Haemophilus influenzae type b (Hib) vaccine in Uganda and estimated the vaccine effectiveness. METHODS: Surveillance data for acute bacterial meningitis among children aged 0-59 months were reviewed from three hospital sentinel sites, for July 2001 to June 2007, to determine the incidence of Hib meningitis, the effectiveness of Hib vaccine with a case-control design, and the number of vaccine-preventable cases and deaths of Hib disease in Uganda. FINDINGS: Of the 13 978 children from 17 districts with suspected bacterial meningitis, 269 had confirmed Hib meningitis, declining from 69 patients in the prevaccine year (2001-2002) to three in 2006-2007. Hib meningitis incidence dropped from 88 cases per 100,000 children aged < 5 years in the year before vaccine introduction to 13 within 4 years, and to near zero in the fifth year. Vaccine effectiveness for 2 or more doses was 93% (95% confidence interval, CI: 69-99) against confirmed Hib meningitis and 53% (95% CI: 11-68) against purulent meningitis of unknown cause. In Uganda, Hib vaccine prevents an estimated 28 000 cases of pneumonia and meningitis, 5000 deaths and 1000 severe meningitis sequelae each year. CONCLUSION: Infant immunization with Hib vaccine has virtually eliminated Hib meningitis in Uganda within 5 years. Ensuring long-term benefits of Hib vaccine urgently requires sustainable vaccine financing, high-quality ongoing surveillance, and a health sector able to deliver a robust immunization programme.

Adherence to antiretroviral therapy in children attending Mulago Hospital, Kampala.

BACKGROUND: Non-adherence reduces the effectiveness of antiretroviral therapy in children attending the paediatric HIV/AIDS clinic at Mulago Hospital, Kampala. AIM: To determine the levels of adherence to HAART and identify factors associated with non-adherence. METHODS: A cross-sectional study of 170 children aged 2-18 years. Adherence to HAART was defined as taking > or =95% of prescribed medication. It was determined using three measures: a 3-day self-report by the caregivers, clinic-based pill counts at enrolment and home-based unannounced pill counts 2-3 weeks later. RESULTS: The 3-day self-reported > or =95% adherence was 89.4% (n=170). Using clinic-based pill counts, 94.1% (n=170) had > or =95% adherence to treatment compared with only 72% (n=164) by unannounced pill counts. When the primary caregiver was the only one who knew the child's serostatus, he/she was three times more likely to be non-adherent (p=0.02, OR 3.34, 95% CI 1.14-9.82). Those who had been hospitalised twice or more before starting HAART were more likely to have > or =95% adherence (p=0.02, OR 0.44, 95% CI 0.20-0.92). CONCLUSION: The majority of children had good adherence levels when estimated by unannounced pill counts. Disclosing the child's HIV serostatus only to the primary caregiver and having been hospitalised only once or not at all were associated with poor adherence.

Cryptosporidiosis and microsporidiosis in ugandan children with persistent diarrhea with and without concurrent infection with the human immunodeficiency virus.

Cryptosporidium spp. and Enterocytozoon bieneusi are enteric pathogens that have emerged as significant causes of persistent diarrhea (PD) in immunologically compromised individuals particularly in association with HIV/AIDS. We conducted a cross-sectional study on the clinical epidemiology of E. bieneusi and Cryptosporidium in children with PD, with and without HIV/AIDS, attending Uganda's Mulago National Referral Hospital. Two hundred forty-three children aged < 60 months, admitted between November 2002 and May 2003 with PD (> 14 days), were analyzed for HIV status and CD4 lymphocyte counts, and stools were screened for the presence of E. bieneusi and Cryptosporidium by microscopy and positive samples genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Eighty (32.9%) of the children were excreting E. bieneusi, and 76 (31.3%) were excreting Cryptosporidium. Ninety-one of the 243 children had HIV, of who 70 (76.9%) had E. bieneusi, versus 10 (6.6%) of the 152 without (odds ratio = 47.33; 95% CI = 19.88 to 115.97), while 67 (73.6%) had Cryptosporidium, versus 9 (5.9%) without (odds ratio = 44.36; 95% CI = 18.39 to 110.40). Children with counts < 25% CD4 cells were more likely to have either E. bieneusi (odds ratio = 7.42; 95% CI = 3.77 to 14.69) or Cryptosporidium (odds ratio = 6.45; 95% CI = 3.28 to 12.76) than those with higher CD4 percentages. However, only HIV status was independently associated with either Cryptosporidium or E. bieneusi. Among the 243 children with PD, 67 (27.8%) were infected with both enteric pathogens, with HIV being the only independent predictor of coinfection. Finally, some 81% of HIV-infected children with PD excreted one or both organisms, compared with only 10% of children with PD testing negative for HIV. Seventy-four percent of isolates were C. hominis, the anthroponotic species, 17% were C. parvum, the zoonotic species, and 8% were a mixture of the two or others.

Serum zinc status of children with persistent diarrhoea admitted to the diarrhoea management unit of Mulago Hospital, Uganda.

INTRODUCTION: Despite great advances in the management of diarrhoeal diseases, persistent diarrhoea remains a major problem in developing countries due to its syndromic nature. Zinc depletion ranks high among the factors contributing to the detrimental effects of persistent diarrhoea on the human body. This however, has not been investigated in the Ugandan population. OBJECTIVE: To determine the serum zinc status of children with persistent diarrhoea. DESIGN: Cross-sectional descriptive study. METHODS: Children aged 6-36 months with persistent diarrhoea were enrolled from the diarrhoea management unit of Mulago hospital. Socio-demographic and morbidity data were collected, and laboratory investigations were carried out after recruitment. Healthy children of similar age and sex were recruited to determine reference levels of serum zinc for comparison. RESULTS: The mean serum zinc level in the children with persistent diarrhoea was 5.83 mol/l while that of children without diarrhoea was 8.99 mol/l with no age or sex difference. The serum zinc concentration of children with persistent diarrhoea was significantly lower than that of children without diarrhoea (p<0.001). The prevalence of zinc deficiency in children with persistent diarrhoea was 47.9%. Of the children with persistent diarrhoea, 64 (66.7%) were stunted, wasted or both. However no significant association was observed between nutritional status and serum zinc levels. Only hypoproteinaemia was significantly associated with serum zinc levels in these children (p=0.03). CONCLUSION: There is a high prevalence of zinc deficiency and malnutrition among Ugandan children with persistent diarrhoea.

Cryptosporidium parvum in children with diarrhea in Mulago Hospital, Kampala, Uganda.

A cross-sectional case-control study (ratio = 3:1) was conducted over a 15-month period to determine the prevalence and consequences of cryptosporidiosis in hospitalized diarrheic children (0-5 years old) at Mulago Hospital in Kampala, Uganda. Cryptosporidium parvum was detected and genotyped among 2,446 children of whom 1,779 (72.7%) had diarrhea, and 667 (27.3%) were age- and sex-matched controls. Of the 1,779 children with diarrhea, 532 (29.9%) had persistent (> 14 days) diarrhea and 1,247 (70.1%) had acute diarrhea. Overall, 444 (25.0%) of the 1,779 children with diarrhea had C. parvum, compared with only 57 (8.5%) of the 667 children without diarrhea (chi2 = 80.2, P < or = 0.0001). Within this group of infected children, 72.8% were infected with genotype 1, 18.4% with genotype 2, and 4.1% with a mixture of both genotypes, and 4.1% isolates were either unclassified or C. meleagridis. The prevalence was highest during the rainy months of April to June. Of the 532 children with persistent diarrhea, 166 (31.2%) had C. parvum compared with 278 (22.3%) of the 1,247 children with acute diarrhea (chi2 = 15.8, P < or = 0.0001). There was a significant association between C. parvum and malnutrition including stunting, being underweight, and wasting. Unfavorable outcome (death or failure to resolve within 14 days) occurred in 139 (72.8%) of the 191 children with C. parvum, and in only 65.1% of the 545 without (odds ratio = 1.117, 95% confidence interval = 1.005-1.243, P = 0.05), Of the 191 children with C. parvum, 24 (12.6%) died, compared with 34 (6.2%) of the 545 without C. parvum (P = 0.005). Mortality rates were higher among children with severe dehydration and persistent diarrhea, and in stunted or underweight children infected with C. parvum. Among Ugandan children, cryptosporidiosis, which remains untreatable, is frequently associated with diarrhea and other serious and unfavorable consequences.

Enterocytozoon bieneusi among children with diarrhea attending Mulago Hospital in Uganda.

The prevalence of Enterocytozoon bieneusi in the general population is unknown. Using genetic tools, we investigated its prevalence and contribution to diarrhea and malnutrition in hospitalized children in Uganda. A cross-sectional, case-control study involving diarrheic children who were matched for age and sex (3:1) with control children. Measurements included anthropometry and clinical assessment. A total of 17.4% of 1,779 children with diarrhea were infected with E. bieneusi compared with 16.8% of 667 control children (CHI2 = 0.137, P = 0.712). Prevalence was highest during the rainy seasons. There was no significant relationship between infection with E. bieneusi and stunting, being underweight, wasting, or acute diarrhea. However, children who were E. bieneusi-positive by a polymerase chain reaction (PCR) had diarrhea for a longer period (15.15 versus 9.67 days; F = 12.02; P = 0.001) compared with children who were either uninfected or were E. bieneusi-positive by a nested PCR. We conclude that E. bieneusi is widespread among children 3-36 months of age in Uganda, and that in a cross-sectional study, there was no clear association of E. bieneusi with poor nutrition or diarrhea. Since E. bieneusi is closely linked with persistent diarrhea and wasting in adults who are positive for human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), the outcome of follow-up studies involving children who are HIV/AIDS-positive and severely malnourished children may be entirely different and warrants further study.