Delayed generation of antibodies mediating human immunodeficiency virus type 1-specific antibody-dependent cellular cytotoxicity in vertically infected infants. WITS Study Group. Women and Infants Transmission Study

Human immunodeficiency virus type 1 (HIV-1)-specific antibody-dependent cellular cytotoxicity (ADCC) antibody titers were serially measured from birth to 24 months in the plasma of 14 intrapartum-infected and 10 uninfected infants born to HIV-1-infected women. The mean ADCC antibody titers measured at birth in infected and uninfected infants were similar (10(-3.9) and 10(-4.0), respectively), suggesting that ADCC antibodies did not protect infants from the intrapartum transmission of HIV-1. In infected infants, ADCC titers at birth did not predict subsequent clinical disease course. The active production of HIV-1-specific ADCC antibodies was detected in most infected infants only after 12 months of age, well after the loss of passively acquired maternal ADCC antibody. The delayed production of ADCC antibodies in infancy may account, in part, for the less efficient control of viral replication and more rapid disease progression following vertical infection compared with that in adults.

Human immunodeficiency virus type 1-specific cytotoxic T lymphocytes (CTL), virus load, and CD4 T cell loss: evidence supporting a protective role for CTL in vivo

The relationships between primary human immunodeficiency virus type 1 (HIV-1) Gag-specific cytotoxic T lymphocyte (CTL) frequency, virus load, and CD4 T cell loss were evaluated in a group of 46 HIV-1-infected persons with hemophilia. Freshly isolated peripheral blood mononuclear cells in limiting dilution assays were used to measure HIV-1 Gag-specific CTL frequencies. Concurrent measurements of virus load and lymphocyte surface markers were obtained. No correlation between Gag-specific CTL frequency and concurrent CD4 cell count was observed. A significant inverse relationship was observed between HIV-1 Gag-specific CTL frequency and provirus load as measured by polymerase chain reaction. Subjects with higher CTL frequencies were found to have more stable CD4 cell counts over time. These results provide additional evidence to support the concept that the predominant role of this virus-specific cellular immune response is to limit viral replication and CD4 cell loss in HIV-1 infection.

Immune complex-dissociated p24 antigen in congenital or perinatal HIV infection: role in the diagnosis and assessment of risk of infection in infants

Immune complex-dissociated (ICD) HIV-1 p24 antigen assay is a rapid technique for assessing the presence of HIV gag or core protein in plasma or serum. In this study, ICD p24 antigen detection in HIV-1 infected mothers and their infants enrolled in the Women and Infants Transmission Study (WITS) was evaluated primarily as a diagnostic assay for HIV-1 detection in young infants and for its association with perinatal transmission. Plasma from 47 infected infants and 160 uninfected infants was examined, along with plasma from 197 of their mothers who had a delivery or close-to-delivery specimen. ICD p24 antigen was detected in plasma of 27.3% of infected infants at birth and in 70% to 81% at 1 to 6 months. The diagnostic specificity at birth was 90% and 98% to 100.0% at 1 to 6 months. The ICD p24 antigen concentration correlated with concurrent quantitative HIV culture results. The risk of transmission from mother to infant was higher if the mother had detectable ICD p24 antigen at or near the time of delivery (p = 0.002), but its presence did not accurately predict transmission (positive predictive value of 36%, negative predictive values of 85%). The relative ease of performing the ICD p24 antigen assay and the low cost compared with that of HIV culture or DNA PCR makes this test a useful adjunct for the diagnosis of perinatal HIV infection and for enhancing understanding of its pathogenesis, particularly where cost and availability limit access to more sensitive assays.

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.

Activity of human immunodeficiency virus type 1 promoter/TAR regions and tat1 genes derived from individuals with different rates of disease progression

Different rates of disease progression may be associated with different human immunodeficiency virus type 1 (HIV-1) promoter and/or transactivator activities. We therefore analyzed the sequences and activities of the first exon of Tat, tat1, and the promoter/trans-acting responsive (TAR) regions amplified directly from peripheral blood mononuclear cells obtained from five long-term nonprogressors and eight progressing HIV-1-infected individuals. The majority of tat1 alleles and promoter/TAR regions from all patients were intact and showed comparable activities in transient reporter assays. A substantial number of point mutations and some length variations were observed in the promoter/TAR region. In a single nonprogressor, the Sp1 binding site 3 was consistently altered and the transcriptional activity in the presence of Tat was diminished. Some LTR clones from a rapid progressor contained a fourth Sp1 binding site, which was associated with an elevated basal promoter activity. These data suggest that defects in the promoter/TAR region or tat1 are rare and that different promoter/transactivator activities are not commonly associated with different progression rates.

Detection and differentiation of Epstein-Barr virus strains by in situ polymerase chain reaction

An in situ polymerase chain reaction (IS-PCR) technique was used to detect and differentiate strains of episomal Epstein-Barr virus (EBV) in infected cells. IS-PCR was performed on cell monolayers in eight-chamber glass slides using EBV type-specific primer pairs conserved within the EBV-encoded nuclear antigen (EBNA) 3C region. The amplicons in the cells were detected by in situ hybridization using EBV type-1 and type-2 specific 5'-biotinylated oligonucleotide probes and avidin-conjugated alkaline phosphatase as secondary reagent. This method was successfully used to identify EBV strains not only in Burkitt's lymphoma cell lines but also in B cells obtained from a patient with infectious mononucleosis. The technique described on this report is a reliable method to detect latently infected EBV-positive cells and can potentially be used to identify and type EBV strains present in clinical specimens.

Combination treatment with zidovudine, didanosine, and nevirapine in infants with human immunodeficiency virus type 1 infection

BACKGROUND

In infants and children with maternally acquired human immunodeficiency virus type 1 (HIV-1) infection, treatment with a single antiretroviral agent has limited efficacy. We evaluated the safety and efficacy of a three-drug regimen in a small group of maternally infected infants.

METHODS

Zidovudine, didanosine, and nevirapine were administered in combination orally to eight infants 2 to 16 months of age. The efficacy of antiretroviral treatment was evaluated by serial measurements of plasma HIV-1 RNA, quantitative plasma cultures, and quantitative cultures of peripheral-blood mononuclear cells.

RESULTS

The three-drug regimen was well tolerated, without clinically important adverse events. Within four weeks, there were reductions in plasma levels of HIV-1 RNA of at least 96 percent (1.5 log) in seven of the eight study patients. Over the 6-month study period, replication of HIV-1 was controlled in two infants who began therapy at 2 1/2 months of age. Plasma RNA levels were reduced by 0.5 to 1.5 log in five of the other six infants.

CONCLUSIONS

Although further observations are needed, it appears that in infants with maternally acquired HIV-1 infection, combined treatment with zidovudine, didanosine, and nevirapine is well tolerated and has sustained efficacy against HIV-1.

Early HIV-1 envelope-specific cytotoxic T lymphocyte responses in vertically infected infants

High frequencies of cytotoxic T lymphocyte precursors (CTLp) recognizing HIV-1 laboratory strain gene products have been detected in adults within weeks of primary infection. In contrast, HIV-1-specific CTLp are uncommonly detected in infants younger than 6 mo. To address the hypothesis that the use of target cells expressing laboratory strain env gene products might limit the detection of HIV-1 env-specific CTLp in early infancy, recombinant vaccinia vectors (vv) expressing HIV-1 env genes from early isolates of four vertically infected infants were generated. The frequencies of CTLp recognizing target cells infected with vv-expressing env gene products from early isolates and HIV-1 IIIB were serially measured using limiting dilution followed by in vitro stimulation with mAb to CD3. In one infant, the detection of early isolate env-specific CTLp preceded the detection of IIIB-specific CTLp. CTLp recognizing HIV-1 IIIB and infant isolate env were detected by 6 mo of age in two infants. In a fourth infant, HIV-1 IIIB env and early isolate env-specific CTLp were simultaneously detected at 12 mo of age. These results provide evidence that young infants can generate HIV-1-specific CTL responses and provide support for the concept of neonatal vaccination to prevent HIV-1 transmission. However, the early predominance of type-specific CTL detected in some young infants suggests that the use of vaccines based on laboratory strains of HIV-1 may not protect against vertical infection.

The relationship between maternal-infant antibody levels and vertical transmission of HIV-1 infection

This study assesses the predictive value of the ratio of HIV-1 antibodies in the newborn at birth to that in the mother for perinatally transmitted infection confirmed subsequently by age 18 months. The ratio of HIV-1 (EIA) antibody levels in the baby at birth to that in the seropositive mother after the first trimester (sequenstration index SI) was available in 114 of a perinatal cohort of 137 infants. We related this ratio to the HIV infection status of the children by 18 months, HIV-1 DNA PCR and HIV-specific IgA antibody detection at birth, between 3 and 6 months, and morbidity and mortality. Thirty-five of the 137 (26 per cent) children were diagnosed as infected by 18 months. The mean (SD) HIV SI was 1.57 (0.88) in 29 infected and 0.83 (0.42) in 85 uninfected infants (P < 0.0001). Sensitivity and specificity of a threshold SI of 1.27 (mean +/- 2 SD of uninfected group) for the prediction of perinatal HIV-1 infection were 41 and 98 per cent, respectively. The reason for the higher SI in the infected babies is the combination of lower antibody titres in the transmitting mothers with raised levels in the infected babies. A similar analysis of antibody ratios showed no statistical differences for measles and tetanus (P > 0.1) between HIV infected and uninfected groups. There was a tendency to increased morbidity (Pearson's correlation coefficient r = 0.31) and more severe disease in those with higher HIV-1 SI. Three of 17 (18 per cent) peripheral blood samples from infected children at birth were PCR positive; all had SI's above the threshold. Overall sensitivity and specificity of PCR were 85 per cent each. Eleven of the 29 infected children were HIV-1 specific IgA positive at birth; six (64 per cent) of these had an SI > 1.27. This simple SI of HIV-1 EIA antibodies at birth is comparable to elaborate techniques in its power to predict perinatally acquired infection. It may be a cheap, reliable and rapid screening test for vertically transmitted HIV-1 infection.

HIV-1 specific immunoglobulin A antibodies as an effective marker of perinatal infection in developing countries

HIV-1 specific IgA antibody testing using commercially available reagents was evaluated at birth to 15 months in a group of infants born to HIV-seropositive South African women. Following IgG depletion of serum samples, 33/35 (94 per cent) of the infected infants and 3/99 (3 per cent) of the uninfected infants showed positive IgA reactivity. Sensitivity at birth was 24 per cent and improved with age; 82 per cent at 3 months, 87 per cent at 6 months and 94 per cent at 12 months. The overall positive and negative predictive values were 92 and 98 per cent, respectively. An evaluation of IgA and PCR in a subsample of infants indicated a better sensitivity of PCR within 3 months of birth, but IgA detection offered a higher overall sensitivity (87 v. 83 per cent) and specificity (91 v. 85 per cent). No significant difference in IgA level was observed between transmitting mothers and non-transmitting mothers. A moderate correlation existed between IgA level in the infant and the cumulative morbidity score, however a stronger association was observed between high IgA levels in the infected infant and rapid disease progression. The viral specific IgA assay is a simple, reliable and cost-effective diagnostic and prognostic test for perinatal HIV infection in developing countries.

Iron versus cholesterol--perspectives on the iron and heart disease debate

Focusing only on the limited question of whether stored iron is a valid heart disease risk factor inappropriately narrows the scope of the debate on the "iron hypothesis." Framing the debate in this way ignores the broad explanatory power of the hypothesis that iron depletion protects against ischemic heart disease. The iron hypothesis provides a conceptual tool for study of the mechanisms by which age and gender influence the development of ischemic heart disease. The assumption that age and gender exert unalterable effects has diverted attention from these strong risk factors, and has led to intense preoccupation with weaker risk factors such as cholesterol. The notion that cholesterol is of central importance has become a rigid and institutionalized point of view. Increased mortality from some cholesterol-lowering drugs is but one of the potential dangers of continued promotion of the flawed idea that heart disease is a function of the cholesterol concentration. The more serious risk is that alternative approaches to the problem of ischemic heart disease will be suppressed. Consideration of the relationship between the iron and cholesterol hypotheses provides important perspectives on the current debate on the role of iron in the development of ischemic heart disease.

Maternal viral load, zidovudine treatment, and the risk of transmission of human immunodeficiency virus type 1 from mother to infant. Pediatric AIDS Clinical Trials Group Protocol 076 Study Group

BACKGROUND AND METHODS

A placebo-controlled trial has shown that treatment with zidovudine reduces the rate at which human immunodeficiency virus type 1 (HIV-1) is transmitted from mother to infant. We present data from that trial showing the number of infected infants at 18 months of age and the relation between the maternal viral load, the risk of HIV-1 transmission, and the efficacy of zidovudine treatment. Viral cultures were obtained, and HIV-1 RNA was measured by two assays in samples of maternal blood obtained at study entry and at delivery.

RESULTS

In 402 mother-infant pairs, the rate of transmission of HIV-1 was 7.6 percent (95 percent confidence interval, 4.3 to 12.3 percent) with zidovudine treatment and 22.6 percent (95 percent confidence interval, 17.0 to 29.0 percent) with placebo (P<0.001). In the placebo group, a large viral burden at entry or delivery or a positive culture was associated with an increased risk of transmission (the transmission rate was greater than 40 percent in the highest quartile of the RNA level). In both groups, transmission occurred at a wide range of maternal plasma HIV-1 RNA levels. Zidovudine reduced plasma RNA levels somewhat (median reduction, 0.24 log). Zidovudine was effective regardless of the HIV-1 RNA level or the CD4+ count at entry. In the zidovudine group, however, after we adjusted for the base-line HIV-1 RNA level and CD4+ count, the reduction in viral RNA from base line to delivery was not significantly associated with the risk of transmission of HIV-1.

CONCLUSIONS

A high maternal plasma concentration of virus is a risk factor for the transmission of HIV-1 from an untreated mother to her infant. The reduction in such transmission after zidovudine treatment is only partly explained by the reduction in plasma levels of viral RNA. To prevent HIV-1 transmission, initiating maternal treatment with zidovudine is recommended regardless of the plasma level of HIV-1 RNA or the CD4+ count.

In vitro characterization of HIV type 1 biological clones from asymptomatic and symptomatic pediatric patients

To investigate the mechanisms of HIV-1 cytopathogenicity, functional biological HIV-1 clones were isolated from two infected children with high viral loads in vivo. Clone HC4 was isolated from a symptomatic child and clone GC6 8-4 was isolated from an asymptomatic child. These clones were characterized for their ability to induce syncytia, and to replicate and induce single-cell death in peripheral blood-derived normal CD4 T cell cultures containing anti-CD4 antibody. Despite similar viral loads as determined by p24 antigen production or viral RNA expression, GC6 8-4 was noncytopathogenic and HC4 was cytopathogenic. Since we had demonstrated that mitochondrial dysfunction correlated with HIV-1-induced cell death, we determined whether the cytopathogenic HC4 clone decreased mitochondrial viability using a mitochondrial-specific dye, rhodamine-123. Following infection, mitochondrial viability decreased in cells infected with HC4 by day 4 and continued to decline through day 7 when compared to uninfected cells. By day 7 postinfection, greater than 80% of the cells in culture were dead. Similar analyses on CD4 T cells infected with the noncytopathogenic GC6 8-4 demonstrated that mitochondria remained functionally viable and > 90% of the cells excluded trypan blue. These studies describe a cell culture system to study single-cell death in the absence of syncytia and secondary infection. Results with two patient-derived HIV-1 biological clones suggest that loss of mitochondrial viability may play a role in HIV-1-induced cytopathogenicity.

High frequency of defective nef alleles in a long-term survivor with nonprogressive human immunodeficiency virus type 1 infection

A large number of nef alleles were obtained from peripheral blood mononuclear cells (PBMC) of four long-term nonprogressing survivors of human immunodeficiency virus type 1 (HIV-1) infection and from five individuals with progressive HIV-1 infection. These primary nef alleles were characterized by DNA sequence analysis and for their ability to downregulate CD4 surface expression. Intact nef open reading frames that directed the expression of Nef protein were recovered from all of the individuals. Most of the Nef proteins derived from three of four individuals with nonprogressive infection and from all five individuals with progressive infection were functional as judged by their ability to induce a decrease in surface CD4 expression. In contrast, one individual with nonprogressive HIV-1 infection yielded an unusually high frequency of disrupted nef open reading frames and Nef proteins defective for CD4 downregulation. Approximately 70% of the nef clones obtained from the PBMC of this individual at eight time points over a 12-year period were disrupted or defective for CD4 downregulation. While functional Nef proteins were demonstrated early in the course of infection (1983), functional nef alleles have surprisingly not come to predominate over time in PBMC DNA in this individual.

Pharmacokinetics, safety, and activity of nevirapine in human immunodeficiency virus type 1-infected children

Phase I trials were conducted in human immunodeficiency virus type 1 (HIV-1)-infected children to examine the pharmacokinetics, safety, and antiretroviral activity of nevirapine, a nonnucleoside HIV-1 reverse transcriptase inhibitor. Nevirapine was rapidly absorbed, but the time to peak plasma concentrations increased with higher doses. Clearance was more rapid in chronic dosing studies than predicted by single-dose studies and was more rapid in younger children than in adolescent children. Rash, which occurred in 1 of the 21 study participants, was the single toxicity regarded as nevirapine-related. At doses > or = 240 mg/m2/day, 5 of 10 children experienced durable suppression of plasma p24 antigen to < 50% of baseline values through 8 weeks of nevirapine monotherapy. Viruses resistant to nevirapine were isolated from all children during therapy, but their isolation did not always predict loss of antiviral activity. The evaluation of nevirapine in combination therapy trials is underway in children.

Comparison of virus burden in blood and sequential lymph node biopsy specimens from children infected with human immunodeficiency virus

BACKGROUND

Lymph nodes serve as reservoirs for the replication of human immunodeficiency virus (HIV) type 1. Comparison of serial measurements of virus burden in lymph nodes and peripheral blood after a change in antiretroviral therapy may provide insights into pathogenic mechanisms and permit a more accurate assessment of a therapeutic response.

STUDY DESIGN

Nevirapine was added to the drug regiment of eight children with HIV infection treated with the combination of zidovudine and didanosine who had increasing levels of serum p24 antigen. Lymph node biopsies were performed at entry and after 12 weeks of therapy.

RESULTS

Neither CD4 counts nor p24 antigen level correlated with the degree of viremia as measured by ribonucleic acid copy numbers in plasma. Correlations were found between HIV DNA copy number in peripheral blood mononuclear cells and HIV DNA copy number in lymph nodes (p = 0.02), as well as between peripheral blood CD4 counts and lymph node architecture. The HIV signals in the lymph nodes conformed to the anatomic organization of apical light zones in the germinal centers; however, in more advanced disease stages, organized germinal centers disappeared as evidence by a decline in the extent of the follicular dendritic network.

CONCLUSIONS

Lymph node biopsies in this small number of HIV-infected children revealed a progressive loss of an organized architecture, especially of the follicular dendritic network. This correlated with a progressive loss of CD4+ cells but not with other measures of disease stage, including viral load, as measured by ribonucleic acid copy numbers.