Development and significance of zidovudine resistance in children infected with human immunodeficiency virus

Quantification of cells with specific phenotypes I: determination of CD4+ cell count per microliter in reconstituted lyophilized human PBMC prelabeled with anti-CD4 FITC antibody

A surface-labeled lyophilized lymphocyte (sLL) preparation has been developed using human peripheral blood mononuclear cells prelabeled with a fluorescein isothiocyanate conjugated anti-CD4 monoclonal antibody. The sLL preparation is intended to be used as a reference material for CD4+ cell counting including the development of higher order reference measurement procedures and has been evaluated in the pilot study CCQM-P102. This study was conducted across 16 laboratories from eight countries to assess the ability of participants to quantify the CD4+ cell count of this reference material and to document cross-laboratory variability plus associated measurement uncertainties. Twelve different flow cytometer platforms were evaluated using a standard protocol that included calibration beads used to obtain quantitative measurements of CD4+ T cell counts. There was good overall cross-platform and counting method agreement with a grand mean of the laboratory calculated means of (301.7 ± 4.9) μL(-1) CD4+ cells. Excluding outliers, greater than 90% of participant data agreed within ±15%. A major contribution to variation of sLL CD4+ cell counts was tube to tube variation of the calibration beads, amounting to an uncertainty of 3.6%. Variation due to preparative steps equated to an uncertainty of 2.6%. There was no reduction in variability when data files were centrally reanalyzed. Remaining variation was attributed to instrument specific differences. CD4+ cell counts obtained in CCQM-P102 are in excellent agreement and show the robustness of both the measurements and the data analysis and hence the suitability of sLL as a reference material for interlaboratory comparisons and external quality assessment.

Correlation of neurodevelopmental features and MRI findings in infantile Krabbe's disease

OBJECTIVE

The purpose of our study was to compare MRI findings with neurobehavioral development in infants with Krabbe's disease.

MATERIALS AND METHODS

Nine infants with Krabbe's disease underwent a total of 19 MR studies during the first year of life as well as tests of mental development, gross motor skills, and fine motor skills (score range: 0-100) within 1 month of imaging. MR scans were scored using the Loes severity scale based on signal abnormality and atrophy, ranging from 0 (best) to 32. We performed three comparisons (Student's t test): each test versus total brain Loes score, fine motor and gross motor tests versus Loes score for the pyramidal tract, and fine motor and gross motor tests versus Loes score for the internal capsule.

RESULTS

Mean test results were 65+/-31 for mental development, 48+/-39 for gross motor score, 57+/-35 for fine motor score, and mean total brain score was 7.79+/-6.20. Correlations for total Loes score were -0.78 (p=0.003) for mental development, -0.74 (p=0.003) for gross motor function, and -0.80 (p<0.001) for fine motor function. Correlations for pyramidal system Loes scores were -0.73 (p=0.003) for fine motor function and -0.58 (p=0.028) for gross motor function. Correlation between Loes scores for internal capsule and fine motor function was -0.38 (p>0.05) and between Loes scores for internal capsule and gross motor function was -0.35 (p>0.05).

CONCLUSION

The very good correlation between testing results and Loes scores for the entire brain and moderately good correlation between test results and scores for specific brain regions indicate the Loes scoring system likely provides a reasonable means for assessing prognosis and therapeutic response for infants with Krabbe's disease.

Transplantation of umbilical-cord blood in babies with infantile Krabbe's disease

BACKGROUND

Infantile Krabbe's disease produces progressive neurologic deterioration and death in early childhood. We hypothesized that transplantation of umbilical-cord blood from unrelated donors before the development of symptoms would favorably alter the natural history of the disease among newborns in whom the disease was diagnosed because of a family history. We compared the outcomes among these newborns with the outcomes among infants who underwent transplantation after the development of symptoms and with the outcomes in an untreated cohort of affected children.

METHODS

Eleven asymptomatic newborns (age range, 12 to 44 days) and 14 symptomatic infants (age range, 142 to 352 days) with infantile Krabbe's disease underwent transplantation of umbilical-cord blood from unrelated donors after myeloablative chemotherapy. Engraftment, survival, and neurodevelopmental function were evaluated longitudinally for four months to six years.

RESULTS

The rates of donor-cell engraftment and survival were 100 percent and 100 percent, respectively, among the asymptomatic newborns (median follow-up, 3.0 years) and 100 percent and 43 percent, respectively, among the symptomatic infants (median follow-up, 3.4 years). Surviving patients showed durable engraftment of donor-derived hematopoietic cells with restoration of normal blood galactocerebrosidase levels. Infants who underwent transplantation before the development of symptoms showed progressive central myelination and continued gains in developmental skills, and most had age-appropriate cognitive function and receptive language skills, but a few had mild-to-moderate delays in expressive language and mild-to-severe delays in gross motor function. Children who underwent transplantation after the onset of symptoms had minimal neurologic improvement.

CONCLUSIONS

Transplantation of umbilical-cord blood from unrelated donors in newborns with infantile Krabbe's disease favorably altered the natural history of the disease. Transplantation in babies after symptoms had developed did not result in substantive neurologic improvement.

HIV-1 chemotherapy and drug resistance

BACKGROUND

Therapy with inhibitors of human immunodeficiency virus type 1 (HIV-1) replication has had only transient clinical benefit to date. It has been speculated that drug-resistant virus mutants may contribute to therapeutic failure.

OBJECTIVE

To extrapolate from the biology of drug-resistant HIV-1 to improve antiretroviral chemotherapeutic strategies.

STUDY DESIGN

The literature was reviewed in regard to clinical and virologic correlates of HIV-1 drug resistance, methodology for detection of resistant virus, and chemotherapeutic strategies for prolonging suppression of virus replication.

RESULTS

HIV-1 isolates resistant to different nucleoside reverse transcriptase (RT) inhibitors, nonnucleoside RT inhibitors, and protease inhibitors have been implicated to different extents with virologic or clinical failure of therapeutic effectiveness. The in vivo antiviral effect of certain nonnucleoside RT inhibitors as monotherapy is lost coincident with emergence of a dominant population of resistant virus. Disease progression is more rapid among patients at advanced stages of HIV-1 disease with highly zidovudine (AZT)-resistant virus (50% inhibitory concentration 1.0 muM AZT) and is not attributable to effects of other baseline predictors of progression studied to date. However, there is no definitive evidence that high level AZT resistance causes the loss of therapeutic benefit of AZT. Several of the research methods used for detection of drug-resistant mutants could be developed for future use as screening assays in clinical virology laboratories.

CONCLUSIONS

Strategies for individualizing therapy based on switching, or adding, drugs at first detection of drug-resistant HIV-1 aim to minimize replication of viruses that are drug-resistant, as well as those that remain susceptible to the drug. If clinical investigation reveals that such approaches extend duration of antiretroviral therapeutic benefit, HIV-1 drug-resistance assessment may be increasingly requested from clinical virology laboratories. Monitoring antiviral suppression by quantifying plasma HIV-1 RNA appears more practical at present, however. Different combination regimens are also being studied to see if some regimens delay emergence of resistant virus longer than others. In the future, sequential empiric changes to new combination regimens every few months may also bear investigation to attempt to "pre-empt" HIV-1 resistance development.

Viral resistance patterns selected by antiretroviral drugs and their potential to guide treatment choice

Massive viral turnover and reverse transcriptase's high error rate create the potential for drug-resistant viral variants to appear rapidly under the selective pressure of antiretroviral therapy. Loss of antiviral effect in treatment-adherent persons is most commonly coincident with the appearance of viral mutants with reduced drug sensitivity. Thus, detection of viral resistance may represent an early marker of therapy failure. Similarly, control of viral replication in the plasma compartment, as defined by plasma viral load below the levels of assay quantification, is associated with a sustained therapeutic response and delayed development of viral resistance. Information on patterns of resistance to and cross-resistance between antiretroviral agents is increasingly well characterised and represents an important consideration when deciding how to combine and/or sequence antiretrovirals to achieve optimal antiviral effects. Given the limited number of antiretrovirals presently available or in advanced development, it is important not to limit future therapeutic options by using therapies early in the treatment sequence which may select for cross-resistant viral variants and hence potentially reduce the magnitude of therapeutic response when treatment is changed to another member of that drug class. However, no studies using resistance to guide clinical decision making have been reported to date and available sequencing studies have focused largely on switching or adding therapies to patients experienced with zidovudine monotherapy. Thus, no resistance driven treatment algorithm is currently available.

Growth patterns reflect response to antiretroviral therapy in HIV-positive infants: potential utility in resource-poor settings

Laboratory monitoring of HIV-infected children is the current standard of care in the United States to guide the appropriate use of antiretroviral therapy (ART). Although ART is becoming a reality in some developing countries, laboratory monitoring of ART is costly, necessitating creative approaches to monitoring. As an initial step to guide monitoring of HIV progression in low resource settings, we assessed the utility of the physical examination to predict clinical progression of HIV. We conducted a retrospective cohort study of HIV-infected children using data from Pediatric AIDS Clinical Trials Group Protocol 300. We developed a clinical predictive model, and compared the utility of the clinical model to the change in HIV RNA viral load as diagnostic tests of ART failure. The clinical model incorporated treatment regimen, age, and height velocity: a three-level clinical predictive model provided likelihood ratios of 0.3, 3.9, and 14. For decline in RNA the likelihood ratios were 0.2 (> 1 log decline), 1.4, and 3.5 (> log increase). We developed a simple clinical predictive model that was able to predict clinical progression of HIV after initiation of new ART. The clinical model performed similarly to using changes in HIV RNA viral load. These data should be validated internationally and prospectively, because the test subjects were from a resource rich environment and growth patterns in undernourished children may be impacted differently by HIV and its treatment. The model was most pertinent to children 36 months of age or younger, and was conducted in children receiving monotherapy and dual therapy.

Efficacy of highly active antiretroviral therapy in HIV-1 infected children

Although the reduction in HIV-1-related deaths with highly active antiretroviral therapy (HAART) is similar in adults and children, the extent of the changes in two important surrogate markers HIV-1 RNA levels and CD4+ T cell counts, differs widely. In most paediatric studies virological response rates to HAART are inferior to those in adults. This review provides an overview of the paediatric clinical studies using HAART and seeks to improve the understanding of factors that may contribute to success or failure of HAART in children. An overview of all current articles on paediatric clinical trials using HAART is provided. 23 papers were available. HIV-1 RNA loads and CD4+ T cell counts were used as primary outcome measures. Virological response rates were highly variable, both among the different antiretroviral drugs but also among different studies using the same medication. Four studies in which dosages of the administrated protease inhibitor (PI) were adjusted after pharmacokinetic evaluation had superior virological response rates compared with those in which fixed dosages were used. Immunological response rates were more uniform than virological responses. In almost all studies increases of CD4+ T cell counts are reported independent of the extent of the virological response. Side-effects of HAART were generally mild, transient, and of gastrointestinal origin. Significant percentages of patients with serum lipid abnormalities were reported in three paediatric studies. However, signs of clinical lipodystrophy were not observed. The inferior virological response rates, which have been reported in HIV-1 infected children treated with HAART form a reflection of the challenges that are encountered in the treatment of these children. Difficulties with adherence and with the pharmacokinetics of PIs in children require an intensive, child-adjusted approach. A practical approach to therapy in institutions without tertiary care facilities may be induction therapy with a lopinavir containing regimen (lacking a need for therapeutic drug monitoring), to reduce high viral load levels followed by an easily tolerated maintenance regimen, for example containing abacavir or nevirapine.

Treatment with highly active antiretroviral therapy in human immunodeficiency virus type 1-infected children is associated with a sustained effect on growth

INTRODUCTION

Growth failure is a common feature of children with human immunodeficiency virus type 1 (HIV-1) infection. Children who are treated with mono or dual nucleoside analogue reverse transcriptase inhibitor (NRTI) therapy show a temporary increase in weight gain and linear growth rate. In adults, protease-inhibitor-containing antiretroviral therapy is associated with a sustained weight gain and increased body mass index (BMI). Experience with protease inhibitors and growth in children is still limited. The data mainly deal with short-term effects on growth.

OBJECTIVE

To evaluate the effect of highly active antiretroviral therapy (HAART) on growth in children with HIV-1 infection.

DESIGN AND METHODS

We analyzed selected growth parameters, clinical data, and laboratory results as part of a prospective, open, uncontrolled, multicenter study to evaluate the clinical, immunologic, and virologic response to HAART consisting of indinavir, zidovudine, and lamivudine in children with HIV-1 infection. Height and weight were measured at 0, 12, 24, 36, 48, 60, 72, 84, and 96 weeks after initiation of HAART. Information about the children's growth before enrollment in the study was retrieved from the hospital medical records and/or the school doctor or health center. BMI was calculated. z Scores were used to express the standard deviation (SD) in SD units from the Dutch reference curves for age and gender. Viral loads and CD4+ T-cell counts were examined prospectively and related to these growth parameters. z Scores were also calculated for CD4+ T-cell counts to correct for age-related differences. A z score of 0 represents the P50, which is exactly the age/sex-appropriate median. A height z score of -1 indicates that a child's height is 1 SD below the age- and gender-specific median height for the normal population. Virologic responders were defined as those who either reached an undetectable viral load (<500 copies/mL) or had a >1.5 log reduction in viral load compared with baseline at week 12 after the initiation of HAART, which was maintained during the follow-up period. RESULTS.

PATIENTS

Twenty-four patients were included (age: 0.4-16.3 years at baseline), with a median HIV-1 RNA load of 105 925 copies/mL (5.03 log), a median CD4+ T-cell count of 0.586 x 10(9)/L (median z score: -2.28 SD), a median height z score of -1.22, a median weight z score of -0.74, and a median baseline BMI z score of -0.32. Eleven patients were naive to antiretroviral therapy, and 13 patients had received previous treatment with NRTI monotherapy. Twenty children used indinavir and 4 children used nelfinavir as part of HAART. VIROLOGIC AND IMMUNOLOGIC RESPONSES TO HAART: Seventeen children were virologic responders, and 7 children were virologic nonresponders. In patients naive to NRTIs, median baseline viral loads were significantly higher than in pretreated patients. However, at weeks 48 and 96, there was no significant difference between the viral loads of both groups. At baseline, there was no significant difference in CD4+a T-cell z scores between virologic responders and nonresponders or between naive and pretreated patients. During 96 weeks of HAART, the increase of CD4+ T-cell z score was significantly higher in responders than in nonresponders. The increase in CD4+ T-cell z score was not significantly different for naive and pretreated patients. HEIGHT, WEIGHT, AND BMI z SCORE CHANGES: We found that there was a trend toward a significantly increased z score change during 96 weeks of HAART compared with the z score change before HAART initiation for height and weight, but not for BMI. GROWTH AND VIROLOGIC RESPONSE TO HAART: When the data were analyzed separately for virologic responders and nonresponders, virologic responders showed significant increases in height and weight. The height and weight of virologic nonresponders did not change significantly. The BMI did not change significantly in responders or in nonresponders. GROWTH AND IMMUNOLOGIC RESPONSE TO HAART: The increase of weight and BMI z scores from baseline correlated positively with the CD4+ T-cell z score increase from baseline. It did not correlate with absolute CD4+ T-cell count increase. Height z score increase did not correlate with CD4+ T-cell z score or with absolute CD4+ T-cell counts. GROWTH AND PREVIOUS NRTI TREATMENT: The height z score decrease from week -48 to baseline was significantly larger in naive than in pretreated patients. The weight and BMI z score change from week -48 to baseline was not significantly different for pretreated and naive patients. From baseline to week 96, the height and weight z score change increased significantly in naive patients but not in pretreated patients compared with the change from week -48 to baseline. The BMI z score did not change significantly over 96 weeks of HAART for naive or pretreated patients. GROWTH AND CLINICAL STAGE OF INFECTION: The clinical stage of infection according to the Centers for Disease Control and Prevention classification correlated negatively with the BMI z score and the weight z score at baseline but not with the height z score. Thus, children with the most severe clinical disease had the lowest BMI and weight z scores at baseline. The BMI z score increased more in children with more advanced clinical infection at baseline, who had lower BMI at baseline. The clinical stage of infection did not correlate with the change in weight z score from baseline to week 96.

CONCLUSIONS

HAART has a positive influence effect on the growth of HIV-1-infected children. This effect is sustained for at least 96 weeks. Height and weight are favorably influenced in children in whom HAART leads to a reduction of the viral load of at least 1.5 log or to <500 copies/mL and to an increase in the CD4+ T-cell z score. In contrast to the increase of the BMI in adults on HAART, BMI did not increase in all children effectively treated with HAART. BMI increased more in children with an advanced stage of infection and a poor nutritional status at baseline. Data from pretreated and naive patients were difficult to interpret, because the baseline characteristics of these 2 groups differed too much.

Prevalence of the T215Y mutation in human immunodeficiency virus type 1-infected pregnant women in a New York cohort, 1995--1999

From 1997 through 1999, the prevalence of the zidovudine resistance mutation T215Y was 9.7% among pregnant women, and the human immunodeficiency virus type 1 (HIV-1) load in those with resistant virus was higher than that measured in women with wild-type HIV-1. All mutations were noted in women with zidovudine experience, which suggests that monotherapy may not be adequate prophylaxis for vertical transmission of HIV-1 infection in the current era.

Vertical transmission of HIV: parameters which might affect infection of placental trophoblasts by HIV-1: a review. Biomed Group on the Study of in Utero Transmission of HIV 1

PROBLEM

To understand the mechanisms preventing and/or facilitating maternofetal transmission of human immunodeficiency virus (HIV)-1 across the placenta during pregnancy.

METHODS OF STUDY

Current experimental data were reviewed.

RESULTS AND CONCLUSIONS

The data about the production of cytokines by placental cells and explants, taken together with information indicating selective passage of certain HIV-1 variants across the placental trophoblast, suggest an intricate regulatory network operating at the fetomaternal interface. The data show a differential differentiation of early and late trophoblasts, as far as HIV entry routes are concerned. We believe this explains the relative predominance of the early infection window, as far as in utero infection is concerned. Whether such a differentiation state can be transiently induced on term placental trophoblasts by several differentiation agents, including cytokines, is being investigated. Whatever the results may be, it is obvious that infection of placental cells is an excellent model of passage infection by HIV of/through a mucosal barrier.

Analysis of HIV-1 reverse transcriptase gene mutations in infected children treated with zidovudine

Prolonged treatment with antiretroviral agents directed against reverse transcription (RT) in patients with HIV-1 infection results in the emergence of virus variants with reduced sensitivity containing mutations in the HIV-1 RT gene. Development of zidovudine (ZDV)-related mutations was studied in a cohort of 24 vertically infected pediatric patients receiving ZDV therapy. Monthly clinical and immunologic evaluation was accompanied by direct sequencing of the HIV-1 RT gene every 4 months. A correlation was observed between the emergence of mutations and the duration of therapy. Mutation at codon 41 was found only in the presence of mutation at codon 215. The presence of the mutations Met41-->Leu and Thr215-->Tyr/Phe did not appear to be related to disease progression. These findings suggest that the mere presence of mutations in the HIV-1 RT gene alone during ZDV monotherapy is not a reliable prognostic marker in the absence of other clinical and virologic information.

Pediatric AIDS prognosis using somatic growth velocity

OBJECTIVE

To describe the natural history of somatic growth in HIV infection by constructing age-specific growth velocity norms and to assess specific prognostic information available using these norms.

DESIGN

Observations on 1338 HIV-infected children aged 3 months to 15 years who participated in one of four US clinical trials of pediatric anti-HIV therapies were pooled; baseline growth velocity data were obtained using the first 6 months of observation for each child.

METHODS

Distributions of physical growth velocities in HIV-infected children in the Pediatric AIDS Clinical Trials Group were computed. Statistical smoothing of growth histories was employed to derive velocity estimates, and quantile regression analysis of growth velocities was performed to allow comparisons of growth rates in age- and gender-heterogeneous cohorts in the context of HIV infection. The quantile regressions provide corrected z-scores for growth velocity that appropriately compare HIV-infected children with one another for the purpose of distinguishing more from less favorable prognoses.

RESULTS

Consistent deficits in growth velocity amongst HIV-infected children were revealed when compared with the Fels Institute velocity standards. Approximately 33% of height (and 20% of weight) age- and sex-corrected velocity measurements obtained in the first 6 months of clinical trial participation lay beneath the corresponding third percentiles of the Fels reference distributions, which are commonly regarded as critical indicators of growth failure. Proportional hazards regression tests indicated that both weight and height velocity contributed significant information on the risk of death among children with AIDS after adjusting for antiretroviral therapy received, CD4 cell counts, and age at trial enrollment. Comparing subjects who differ in initial weight velocity by one age- and sex-corrected SD, the relative hazard of death was 0.63 (95% confidence interval, 0.55-0.72; P < or = 0.0001) in favor of the child with greater weight velocity, controlling for antiretroviral therapy received, age and CD4 cell count at baseline. The analogous hazard ratio for height velocity was 0.68 (95% confidence interval, 0.57-0.79; P < or = 0.0001).

CONCLUSIONS

Suitably normalized growth velocities are informative and inexpensive criteria for pediatric AIDS prognosis; the growth velocity distributions presented will be useful for comparing growth effects of new therapeutic strategies to those of single and combination antiretrovirals employed for maintenance of pediatric HIV infection in the mid-1990s.

Pilot study of zidovudine-lamivudine combination therapy in vertically HIV-infected antiretroviral-naive children

OBJECTIVE

To examine tolerance and efficacy of a zidovudine plus lamivudine combination in HIV-infected children without previous exposure to antiretroviral drugs.

METHODS

Thirteen vertically infected children (aged 4 months to 10 years) were treated with zidovudine (approximately 100 mg/m2 three times daily) and lamivudine (4 mg/kg twice daily). CD4 T-cell count, plasma HIV RNA concentration, complete blood count and blood chemistry profile were monitored before treatment and at months 1, 3 and 6.

RESULTS

In general, treatment was well tolerated. One child developed slight neutropenia in the presence of antineutrophil antibodies. CD4 cell count increased from 851+/-621 x 10(6)/l at baseline to 1073+/-945 x 10(6)/l at month 3 (P < 0.05) and to 1133+/-728 x 10(6)/l at month 6 (P = 0.01). CD4+ cell count increased in 10 patients after 3 months and in 11 patients treated for 6 months. One child showed a continuous decrease of CD4 cells despite treatment. Before treatment the plasma HIV RNA concentration was elevated in nine children (> 4.0 log10 copies/ml) and decreased in all of them: by month 1, the mean reduction was -1.16 log10 copies/ml; by month 3, -1.38 log10 copies/ml; and by month 6, -1.53 log10 copies/ml compared with baseline. However, one child showed steadily increasing viral load from 2.7 log10 copies/ml to a maximum of 4.52 log10 copies/ml, surprisingly in association with increasing numbers of CD4 cells. This child was switched to a new combination regimen after 6 months of treatment. Plasma HIV RNA levels below limit of detection were reached in six patients: after 1 month of treatment in one patient, after 3 months in five patients, and after 6 months in six patients. There was a mean reduction of viral load from 4.56 log10+/-4.63 log10 copies/ml (n = 13) to 3.8 log10+/-3.9 log10 copies/ml (P < 0.05; n = 9) after 1 month, to 3.67 log10+/-3.88 log10 copies/ml (P < 0.01; n = 13) after 3 months, and to 3.64 log10+/-3.95 log10 copies/ml after 6 months of treatment (P < 0.001; n = 13).

CONCLUSIONS

This pilot study demonstrates the feasibility of zidovudine-lamivudine combination in children not previously exposed to antiretroviral drugs. This promising combination should therefore be evaluated in larger trials.

HIV-1 reverse transcriptase codon 215 mutation in plasma RNA: immunologic and virologic responses to zidovudine. The AIDS Clinical Trials Group Study 175 Virology Team

Treatment of HIV infection with zidovudine (ZDV) may select for changes in the genetic sequence of the viral reverse transcriptase (RT) that imparts drug resistance. The presence of a 2-bp mutation at codon 215 of RT (from threonine to phenylalanine or tyrosine) was assessed in plasma viral RNA in 85 subjects treated with ZDV in the AIDS Clinical Trials Group (ACTG) 175 virology substudy. Median CD4 cell numbers, HIV plasma RNA levels, and infectious titers of virus were significantly different over 56 weeks of treatment among 58 subjects with the wild-type threonine at codon 215 virus at study entry compared with the 27 subjects with mutations to phenylalanine or tyrosine (MUT) virus. Thirty percent (13 of 44 subjects) with wild-type virus at study entry developed a new codon 215 mutation. Genotypic resistance at codon 215 in plasma HIV RNA is associated with the subsequent immunologic and virologic failure of ZDV monotherapy in subjects with 200 to 500 CD4 cells/mm3.

Long terminal repeat and nef gene variants of human immunodeficiency virus type 1 in perinatally infected long-term survivors and rapid progressors

HIV-1 sequences from perinatally infected children were analyzed in the long terminal repeat (LTR) region and nef in order to investigate associations of viral variation and disease progression. Four long-term survivors who reached 10 years of age or older, and four rapid progressors who survived less than 2 years, participated in this study. LTR sequences of multiple independent viral variants from each individual were compared. No sequence pattern within the LTR consistently distinguished long-term survivors from rapid progressors or vice versa. Deletions and insertions within transcription factor binding sites of the LTR and nef ranging from 8 to 341 bp were found in viral variants from the eldest long-term survivor (LTS047). These deletions and duplications may be associated with the survival of LTS047 via an unknown mechanism. Among all children in this study, the sites in the untranslated region (NF-kappaB, SP1, and TATA box) were more conserved than the sites in the nef/LTR overlap region (NFAT, purine-rich region, USF, TCF1alpha), reflecting the importance of the sites in the untranslated region for viral replication. A mutation in the E box motif within the USF site among the sequences from a long-term survivor (LTS113) is predicted to disrupt protein binding and may be associated with slow disease progression. Mutations of the SP1-III site in a rapid progressor (RP056) indicate that this site is not necessary for rapid disease progression.

CCR5del32 in perinatal HIV-1 infection

CCR5, a chemokine receptor, serves as a coreceptor for macrophage-tropic HIV-1 (1-3). A 32-bp deletion within the gene encoding CCR5, CCR5del32, has been shown to prevent HIV-1 infection of T cells in the absence of a wild-type allele. This alteration is present in low frequency in Caucasian populations (4-6). To investigate the effect of CCR5del32 in perinatal HIV-1 transmission and disease progression, two cohorts of perinatally exposed infected and uninfected children were analyzed for the presence of the allele. Polymerase chain reaction (PCR) was used to identify CCR5del32 in prevalent and prospective cases among 144 African American children from New York City and 73 Caucasian children from Barcelona, Spain. HIV-1 transmission; clinical manifestations of disease, including encephalopathy, opportunistic infections, and death before 2 years of age; survival; Centers for Disease Control and Prevention (CDC) classification; and degree of immunosuppression were compared in children with and without CCR5del32. The allele frequency in HIV-1-infected African Americans (0.016) was lower than in Catalan children (0.041). No evidence for a dominant protective effect of CCR5del32 for HIV-1 transmission or disease progression was found in these cohorts.

Viral phenotype, antiretroviral resistance and clinical evolution in human immunodeficiency virus-infected children

BACKGROUND

The syncytium-inducing (SI) viral phenotype and the emergence of viral strains resistant to zidovudine have been described in persons infected with HIV, and in some cases they have been associated with poor prognosis.

METHODS

HIV isolates obtained from 37 HIV-infected children were analyzed to determine whether the SI viral phenotype and the mutation on the 215 position of the reverse transcriptase (M215) could be used as markers of disease progression. We performed peripheral blood coculture mononuclear cells, and we analyzed the induction of syncytia using the MT-2 cell line. The emergence of mutations on the 215 position was determined by PCR.

RESULTS

We found a statistically significant association (P < 0.05) between SI viral phenotype and (1) recurrent serious bacterial infections, (2) absolute CD4+ cell counts <2 SD, (3) progression to AIDS and (4) death. Sixty percent of the children treated with zidovudine developed 215 mutant viral strains without statistically significant association with clinical or immunologic findings. The SI viral phenotype was statistically associated with the presence of the 215 mutation (P < 0.05).

CONCLUSIONS

SI viral phenotype is a marker associated with a poor clinical and immunologic progression of the disease and it may facilitate the emergence of mutant strains in children treated with zidovudine.

Zidovudine, didanosine, or both as the initial treatment for symptomatic HIV-infected children. AIDS Clinical Trials Group (ACTG) Study 152 Team

BACKGROUND

Zidovudine has been the drug of choice for the initial treatment of symptomatic children infected with the human immunodeficiency virus (HIV). This trial was designed to assess the efficacy and safety of treatment with zidovudine alone as compared with either didanosine alone or combination therapy with zidovudine plus didanosine.

METHODS

In this multicenter, double-blind study, symptomatic HIV-infected children 3 months through 18 years of age were stratified according to age (<30 months or > or =30 months) and randomly assigned to receive zidovudine, didanosine, or zidovudine plus didanosine. The primary end point was length of time to death or to progression of HIV disease.

RESULTS

Of the 831 children who could be evaluated, 92 percent had never received antiretroviral therapy and 90 percent had acquired HIV perinatally. An interim analysis (median follow-up, 23 months) showed a significantly higher risk of HIV-disease progression or death in patients receiving zidovudine alone than in those receiving combination therapy (relative risk, 0.61; 95 percent confidence interval, 0.42 to 0.88; P=0.007). The study arm with zidovudine alone was stopped and unblinded; the other two treatment arms were continued. At the end of the study, didanosine alone had an efficacy similar to that of zidovudine plus didanosine (median follow-up, 32 months) (relative risk of disease progression or death, 0.98; 95 percent confidence interval, 0.70 to 1.37; P=0.91). A significantly lower risk of anemia or neutropenia was seen in patients receiving didanosine alone (P=0.036).

CONCLUSIONS

In symptomatic HIV-infected children, treatment with either didanosine alone or zidovudine plus didanosine was more effective than treatment with zidovudine alone. The efficacy of didanosine alone was similar to that of the combination therapy and was associated with less hematologic toxicity.

L-2-oxothiazolidine-4-carboxylic acid inhibits human immunodeficiency virus type 1 replication in mononuclear phagocytes and lymphocytes

We investigated the effects of L-2-oxothiazolidine-4-carboxylic acid (OTC; Procysteine), a cysteine prodrug, on human immunodeficiency virus type 1 (HIV-1) expression in both adult peripheral and cord blood mononuclear phagocytes and lymphocytes. OTC suppressed HIV-1 expression in monocyte-derived macrophages (MDM) and lymphocytes in a dose-dependent fashion as determined by HIV-1 reverse transcriptase (RT) activity. This inhibitory effect of OTC occurred with three HIV-1 strains (two laboratory-adapted strains and one primary isolate). Addition of OTC to chronically HIV-1-infected MDM cultures also suppressed RT activity by 40 to 50% in comparison to untreated controls. The inhibitory effects of OTC on HIV-1 were not caused by toxicity to MDM or lymphocytes because there was no change in cell viability or cellular DNA synthesis, as evaluated by trypan blue dye exclusion and [3H]thymidine incorporation, at doses of OTC that inhibit virus replication. These observations indicate that OTC has the potential to limit HIV-1 replication in mononuclear phagocytes and lymphocytes and may be useful in the treatment of HIV-1 infection and AIDS.

A zidovudine-resistant simian immunodeficiency virus mutant with a Q151M mutation in reverse transcriptase causes AIDS in newborn macaques

The simian immunodeficiency virus (SIV)-newborn rhesus macaque model of AIDS can be used to study directly the virulence of viral mutants which are resistant to antiviral drugs. A viral mutant called SIVmac79A6.1, isolated from an SIV-infected macaque after prolonged zidovudine treatment, was found to have a double-base-pair change at codon 151 of reverse transcriptase, resulting in a glutamine to methionine substitution (Q151M). This mutation was associated with more than 100-fold increased resistance to zidovudine and low-level cross-resistance to other dideoxynucleoside analogs. To determine whether this Q151M mutation affects viral virulence, four newborn macaques were inoculated intravenously with a biological clone of this drug-resistant SIVmac79A6.1 mutant; two of these animals were also treated orally with zidovudine. All four animals showed persistent viremia, and two of the four animals developed fatal immunodeficiency at 3 and 8 months of age, respectively. The remaining two animals had CD4+ T-cell depletion and clinical symptoms of AIDS at 22 months. No phenotypic or genotypic reversion of virus to the wild type could be detected in any of the four animals. These results demonstrate that the Q151M mutation in SIV reverse transcriptase does not reduce viral virulence.

Clinical and laboratory characteristics of a large cohort of symptomatic, human immunodeficiency virus-infected infants and children. AIDS Clinical Trials Group Protocol 152 Study Team

BACKGROUND

A large cohort of antiretroviral therapy-naive, symptomatic, HIV-infected children were enrolled into a controlled therapeutic trial (AIDS Clinical Trials Group Protocol 152), providing an opportunity to describe their clinical and laboratory characteristics and determine age-related distinctions.

METHODS

Study entry evaluations for 838 of 839 enrolled children were analyzed. Weight, head circumference (if < 30 months of age), neuroradiologic imaging of the head, developmental or cognitive status and neurologic examination were assessed. Laboratory studies included hemoglobin, absolute neutrophil count, CD4 cell count, serum amylase, alanine aminotransaminase, p24 antigen and HIV blood culture. Data were categorized by age (3 to < 12 months, 12 to < 30 months, 30 months to 6 years and > or = 6 years).

RESULTS

Younger children had significantly higher rates of abnormalities before antiretroviral therapy, especially factors relating to growth and neurologic or cognitive function. Lower CD4+ cell counts and percentages as well as a positive serum p24 antigen correlated with lower weight-for-age Z scores and developmental indices.

CONCLUSIONS

These data provide a description of the clinical characteristics of HIV-infected US children at the time antiretroviral therapy is initiated for HIV-related symptoms. The high rate of abnormalities of growth, development and cognitive ability that were observed in children < 30 months of age demonstrates that treatment strategies should be developed for earlier intervention.

Pediatric human immunodeficiency virus infection

In the past decade, an increase in pediatric human immunodeficiency virus (HIV) infection has had a substantial impact on childhood morbidity and mortality worldwide. The vertical transmission of HIV from mother to infant accounts for the vast majority of these cases. Identification of HIV-infected pregnant women needs to be impoved so that appropriate therapy can be initiated for both mothers and infants. While recent data demonstrate a dramatic decrease in HIV transmission from a subset of women treated with zidovudine during pregnancy, further efforts at reducing transmission are desperately needed. This review focuses on vertically transmitted HIV infection in children, its epidemiology, diagnostic criteria, natural history, and clinical manifestations including infectious and noninfectious complications. An overview of the complex medical management of these children ensues, including the use of antiretroviral therapy. Opportunistic infection prophylaxis is reviewed, along with the important role of other supportive therapies.

Vertical human immunodeficiency virus-1 infection: involvement of the central nervous system and treatment

Involvement of the central nervous system (CNS) contributes substantially to morbidity and mortality of vertical infection with the human immunodeficiency virus (HIV)-1. The clinical spectrum ranges from minor developmental disabilities to severe and progressive encephalopathy. Progression of the disease varies considerably. Both direct viral and indirect host-related pathogenic mechanisms have been proposed. The diagnosis depends on neurological and neurodevelopmental assessments. So far, HIV-1-specific antiviral treatment has shown limited effects on neurological manifestations in symptomatic children. Thus, efforts are needed to improve prevention and treatment of CNS involvement. It is still unclear whether early use of antiretroviral agents is of benefit.

CONCLUSION

Since experience of treatment of HIV-1 infections in adults cannot easily be translated to children, paediatric clinical trials are needed to answer questions specific to the unique characteristics of children.

Reverse transcriptase mutations in HIV-1-infected children treated with zidovudine

Human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) mutations were detected in DNA from peripheral blood mononuclear cells from 11 of 12 HIV-1-infected children after 11-20 months of zidovudine monotherapy. The number of children with mutations detected at each codon were as follows: codon 41, 4; codon 67, 2; codon 70, 7; codon 215, 7; codon 219, 0. Codon 41 mutations were found only in the presence of a codon 215 mutation and in the absence of a codon 70 mutation. The codon 41/215 mutant combination was associated with decline in weight-for-age z score during therapy, weight < 10th percentile, CD4+ cell counts < 3rd percentile, and immune-complex dissociated HIV-1 p24 antigen (ICD p24 Ag) levels > 100 pg/ml. Patients developing the codon 70 mutation tended to have body weight > 30th percentile, CD4+ cell counts > 25th percentile, and ICD p24 Ag < 100 pg/ml. The codon 41 mutation was associated with clinical deterioration during a 6-month followup period.

Use of viral resistance patterns to antiretroviral drugs in optimising selection of drug combinations and sequences

High rates of viral replication throughout HIV infection, and the frequency of mutation occurring during each replication cycle due to the inaccuracy of reverse transcriptase, drive the potential for drug-resistant viral variants to appear under the selective pressure of antiretroviral therapy. Loss of antiviral effect with a variety of antiretroviral agents has been reported to coincide with the appearance of viral mutants with reduced drug sensitivity. Additionally, the presence of both phenotypic and genotypic zidovudine resistance is associated with an increased risk of clinical disease progression and death, independent of a change of therapy to didanosine. The patterns of resistance to and cross-resistance between antiretroviral agents are increasingly well characterised, and represent an important consideration when deciding how to combine and/or sequence antiretrovirals to achieve optimal antiviral effects. Given the limited number of antiretrovirals currently available or in advanced development, it is important not to potentially limit future therapeutic options by using, early in the treatment sequence, therapies which may select for cross-resistant viral variants and hence potentially reduce the additional therapeutic response when treatment is changed to another member of that drug class.

Does the number of seizures before treatment influence ease of control or remission of childhood epilepsy? Not if the number is 10 or less

Using a population-based regional cohort of 479 children with epilepsy, we studied the effect of the number of pretreatment afebrile seizures on seizure control and remission. The number of pretreatment seizures varied from 1 to 20. For the first 10 pretreatment seizures, there was no significant difference or trend in (1) the proportion of children who were seizure free long enough to attempt stopping medication (mean, 70%), (2) the number of breakthrough seizures before control was achieved, or (3) the proportion of children who were seizure free after stopping medication for the first time (mean, 70%). More patients with more than 10 pretreatment seizures had complex partial seizures (59%) than those with 10 or fewer seizures (16%) (p < 0.00001). We conclude that there does not appear to be any penalty for seizure control or early remission of epilepsy if medication is delayed for up to 10 pretreatment seizures.

Resistance to antivirals

The ability of viruses to develop resistance to antiviral agents is already a major concern with respect to HIV. This article reviews mechanisms and clinical correlates of antiviral resistance and alternative drugs for treatment of infections due to resistant strains of HIV, herpes simplex virus, cytomegalovirus, varicellazoster virus, and influenza A.

A rapid, direct test for zidovudine susceptibility in clinical isolates of human immunodeficiency virus type 1 (HIV-1) from infected children

BACKGROUND

Existing phenotypic tests of antiretroviral susceptibility in clinical isolates of human immunodeficiency virus (HIV) are expensive and slow, and require passage of virus in cell culture with the possible consequence of selecting variants.

OBJECTIVES

We sought to develop a rapid 14-day assay for zidovudine susceptibility of cell-associated HIV performed directly in patient blood samples.

STUDY DESIGN

Twenty-three tests were performed prospectively in 21 children, and the results were compared with those of the AIDS Clinical Trials Group/Department of Defense consensus drug susceptibility assay (DSA) as well as certain clinical parameters.

RESULTS

Five strains from ZDV-naive children were sensitive by the rapid test. Three were tested by DSA, and all were sensitive. Six strains from children who had received >/=24 months of ZDV were resistant by the rapid assay. Four of these strains were tested by the DSA, and all were shown resistant. The viral strains from children who received <24 months of therapy or who had switched from ZDV to other antiviral therapy exhibited variable sensitivity by both tests. Changes in CD4 cells in the subsequent 6 months, as well as weight gain during this time were both correlated to the results of the rapid test. The syncytium-inducing capacity of the virus strains was analyzed similarly.

CONCLUSIONS

The rapid intracellular virus susceptibility assay is a test of drug sensitivity performed on HIV growing in cells obtained directly from an infected patient. The test has a two-week turn-around time and, in this preliminary report, gives results which correlate with both time on zidovudine and also subsequent CD4 cell changes.

Specific, sensitive, and rapid assay for human immunodeficiency virus type 1 pol mutations associated with resistance to zidovudine and didanosine

The effectiveness of antiretroviral therapy may be limited by the development of human immunodeficiency virus type 1 (HIV-1) resistance. Monitoring for resistance will perhaps allow changes in therapy prior to deterioration in the patient's clinical or immunologic status. Our objective was to develop a rapid, specific, and sensitive genotypic assay for HIV-1 resistance to zidovudine (ZDV) and didanosine (ddI) which is simple to perform. In our assay the DNA of HIV-1 pol was amplified by PCR using two sets of nested oligonucleotide primers. Mutations of reverse transcriptase (RT) encoding amino acids (aa) 74 and 41, 70, and 215 which have been associated with HIV-1 resistance to ddI and ZDV, respectively, were detected with a ligase detection reaction (LDR) and indicated colorimetrically. The RT genotypes of 35 patient specimens (140 codons) blindly assessed for these mutations were in agreement by PCR-LDR and by dideoxynucleotide sequencing. To evaluate the limits of the assay, other specimens with mutations close to the ligation site were evaluated by PCR-LDR. The assay was sensitive and specific for all specimens except when mutations occurred within 2 bases on either side of the ligation site. In summary, this PCR-LDR assay specifically, sensitively, and rapidly detected pol mutations (RT aa 74, 41, 70, and 215) associated with HIV-1 resistance to ddI and ZDV.

Human cord blood mononuclear cells are preferentially infected by non-syncytium-inducing, macrophage-tropic human immunodeficiency virus type 1 isolates

Identification of the factors which impact on the transmission of human immunodeficiency virus type 1 (HIV-1) from an infected mother to her infant is essential for the development of effective strategies to prevent perinatal HIV-1 infection. The current study was designed to determine if unstimulated human neonatal cord blood mononuclear cells (CBMC) differ from adult peripheral blood mononuclear cells (PBMC) in susceptibility to HIV-1 infection. Both cell populations were challenged with two laboratory and two clinical HIV-1 isolates with different phenotypic properties. Infection was evaluated by quantitation of p24 antigen production and p24 antigen expression by an enzyme immunoassay and immunofluorescence, respectively. T-cell markers were determined by flow cytometry. Unstimulated CBMC were preferentially infected by macrophage-tropic, non-syncytium-inducing (non-SI) laboratory and clinical isolates, whereas PBMC were more susceptible to T-lymphotropic, SI HIV-1 strains. The macrophage-tropic strain HIV-1Ba-L replicated to 100-fold higher titers in CBMC than a similar inoculum of the SI isolate HIV-1LAI. The opposite occurred in unstimulated PBMC, which replicated HIVLAI to eightfold higher titers than the macrophage-tropic isolate. These findings indicate that a selection of viral phenotype may occur with unstimulated CBMC displaying a predominant susceptibility to infection by macrophage-tropic, non-SI HIV-1 strains and that this selection may influence mother-infant transmission of HIV-1.

Identification of drug-related genotypic changes in HIV-1 from serum using the selective polymerase chain reaction

We attempted to detect drug-related HIV-1 pol gene mutations by selective polymerase chain reaction (PCR) using both proviral DNA and viral RNA isolated from patients (pts) with AIDS or ARC receiving antiretroviral therapy. Peripheral blood mononuclear cell (PBM)-associated proviral DNA and serum-derived viral RNA were obtained from eight patients before and after receiving an alternating regimen of AZT and ddC for 15-41 months or ddI monotherapy for 12-26 months. These specimens were examined for the presence of mutations at positions 70, 74, 215 and 219. We noted that selective PCR results can be ambiguous depending on the quantity of DNA template employed. We, therefore, used the minimal quantity of DNA templates that yielded evaluable PCR products in this study. For all the eight pairs of pre- and post-therapy proviral DNA samples, selective PCR results agreed with independently determined nucleotide sequences. Results of reverse transcription of serum-derived viral RNA followed by selective PCR differed in some cases from those using the proviral DNA. In particular, the use of serum viral RNA appeared to allow earlier detection of changes in drug-related mutations than the use of PBM-associated proviral DNA. We conclude that (i) selective PCR using the minimum and sufficient number of PBM-associated proviral DNA and serum viral RNA copies successfully detects the presence of known pol gene mutations; (ii) drug-related mutations may be distinguished earlier in virions in serum (or plasma) than in proviral DNA in PBM; and (iii) quantification of HIV-1 prior to selective PCR may be an important component in monitoring the therapy of HIV-1 infection.

Zidovudine. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine remains the mainstay in the treatment of patients infected with human immunodeficiency virus (HIV). The drug delays disease progression to acquired immunodeficiency syndrome (AIDS) and to AIDS-related complex (ARC), reduces opportunistic infections, and increases survival in patients with advanced HIV infection. There is evidence to suggest that zidovudine also delays disease progression in patients with mild symptomatic disease. Although one study has shown zidovudine to have no significant beneficial effects on survival or disease progression in patients with asymptomatic HIV infection, several other studies have shown zidovudine to delay disease progression in this patient group. Results from related ongoing studies are awaited with interest. Zidovudine reduces the incidence of AIDS dementia complex (ADC) and appears to prolong survival in these patients, and improves other neurological complications of HIV infection. The drug also appears to enhance the efficacy of interferon-alpha in patients with Kaposi's sarcoma. Although zidovudine is widely used as postexposure prophylaxis following accidental exposure to HIV, its efficacy in preventing seroconversion is unclear. Whether zidovudine prevents vertical transmission also remains to be determined. The overall efficacy of zidovudine in the treatment of children with HIV infection appears similar to that in adults despite more rapid disease progression in younger patients. Zidovudine-resistant isolates can emerge as early as after 2 months' therapy, and primary infection with zidovudine-resistant strains has been documented. Both zidovudine resistance and the syncytium-inducing HIV phenotype appear to be associated with poor clinical outcome. However, zidovudine resistance may revert on drug withdrawal or switching to an alternative therapy. Zidovudine-associated haematotoxicity may be dose-limiting. Nonhaematological adverse events associated with zidovudine therapy are generally mild and usually resolve spontaneously. Dosages of approximately 500 to 600 mg/day appear to be at least as effective as dosages of 1200 to 1500 mg/day and are better tolerated in patients with less advanced disease. However, optimal dosage are unclear. Despite beneficial effects, zidovudine monotherapy is not curative. There is evidence to suggest that the concomitant administration of zidovudine with didanosine or zalcitabine is effective in patients with HIV disease progression despite receiving zidovudine monotherapy, and there is some evidence that concomitant zidovudine plus didanosine therapy is more effective than alternating monotherapy. However, results from studies of combination therapy in asymptomatic patients, and from comparative combination therapy studies are awaited. Cotherapy with agents that augment haematopoiesis allows the continuation of therapeutic zidovudine dosages.(ABSTRACT TRUNCATED AT 400 WORDS)