The effects of zidovudine in the subset of infants infected with human immunodeficiency virus type-1 (Pediatric AIDS Clinical Trials Group Protocol 076)

Identification of causal intervention effects under contagion

Defining and identifying causal intervention effects for transmissible infectious disease outcomes is challenging because a treatment - such as a vaccine - given to one individual may affect the infection outcomes of others. Epidemiologists have proposed causal estimands to quantify effects of interventions under contagion using a two-person partnership model. These simple conceptual models have helped researchers develop causal estimands relevant to clinical evaluation of vaccine effects. However, many of these partnership models are formulated under structural assumptions that preclude realistic infectious disease transmission dynamics, limiting their conceptual usefulness in defining and identifying causal treatment effects in empirical intervention trials. In this paper, we propose causal intervention effects in two-person partnerships under arbitrary infectious disease transmission dynamics, and give nonparametric identification results showing how effects can be estimated in empirical trials using time-to-infection or binary outcome data. The key insight is that contagion is a causal phenomenon that induces conditional independencies on infection outcomes that can be exploited for the identification of clinically meaningful causal estimands. These new estimands are compared to existing quantities, and results are illustrated using a realistic simulation of an HIV vaccine trial.

World Health Organization generic protocol to assess drug-resistant HIV among children <18 months of age and newly diagnosed with HIV in resource-limited countries

Increased use of nonnucleoside reverse transcriptase inhibitors (NNRTIs) in pregnant and breastfeeding women will result in fewer children infected with human immunodeficiency virus (HIV). However, among children infected despite prevention of mother-to-child transmission (PMTCT), a substantial proportion will acquire NNRTI-resistant HIV, potentially compromising response to NNRTI-based antiretroviral therapy (ART). In countries scaling up PMTCT and pediatric ART programs, it is crucial to assess the proportion of young children with drug-resistant HIV to improve health outcomes and support national and global decision making on optimal selection of pediatric first-line ART. This article summarizes a new World Health Organization surveillance protocol to assess resistance using remnant dried blood spot specimens from a representative sample of children aged <18 months being tested for early infant diagnosis.

Initiation of antiretroviral treatment in women after delivery can induce multiclass drug resistance in breastfeeding HIV-infected infants

BACKGROUND

The World Health Organization currently recommends initiation of highly active antiretroviral therapy (HAART) for human immunodeficiency virus (HIV)-infected lactating women with CD4+ cell counts <350 cells/μL or stage 3 or 4 disease. We analyzed antiretroviral drug resistance in HIV-infected infants in the Post Exposure Prophylaxis of Infants trial whose mothers initiated HAART postpartum (with a regimen of nevirapine [NVP], stavudine, and lamivudine). Infants in the trial received single-dose NVP and a week of zidovudine (ZDV) at birth; some infants also received extended daily NVP prophylaxis, with or without extended ZDV prophylaxis.

METHODS

We analyzed drug resistance in plasma samples collected from all HIV-infected infants whose mothers started HAART in the first postpartum year. Resistance testing was performed using the first plasma sample collected within 6 months after maternal HAART initiation. Categorical variables were compared by exact or trend tests; continuous variables were compared using rank-sum tests.

RESULTS

Multiclass resistance (MCR) was detected in HIV from 11 (29.7%) of 37 infants. Infants were more likely to develop MCR infection if their mothers initiated HAART earlier in the postpartum period (by 14 weeks vs after 14 weeks and up to 6 months vs after 6 months, P = .0009), or if the mother was exclusively breastfeeding at the time of HAART initiation (exclusive breastfeeding vs mixed feeding vs no breastfeeding, P = .003).

CONCLUSIONS

Postpartum maternal HAART initiation was associated with acquisition of MCR in HIV-infected breastfeeding infants. The risk was higher among infants whose mothers initiated HAART closer to the time of delivery or were still exclusively breastfeeding when they first reported HAART use.

Disease Progression Among HIV-Infected Children Who Receive Perinatal Zidovudine Prophylaxis

BACKGROUND

Studies of perinatal HIV infection have reported mixed results regarding the prognosis of HIV-infected infants exposed to perinatal zidovudine prophylaxis (PZP).

METHODS

We have followed a population-based cohort of children with perinatal HIV infection to evaluate whether early HIV disease progression was more common among those who received PZP and whether subsequent antiretroviral therapy (ART) was less effective in preventing early disease progression.

RESULTS

We identified 73 children with perinatal HIV infection born between 1994 and 2001 with at least 3 years of follow-up and with information concerning PZP administration. Children who received PZP started subsequent ART at an earlier age than those who did not receive PZP (median age at starting treatment: 2 months for PZP vs. 6 months for no PZP; P = 0.0002). PZP was associated with decreased early HIV progression: 21% (7 of 33) of children who received PZP progressed to a category C diagnosis by 3 years compared with 45% (18 of 40) of children who did not receive PZP (P = 0.047). Children who did not receive PZP progressed to a category C diagnosis at a younger age than children who received PZP (median: 4 vs. 11 months; P = 0.061). ART was as effective in preventing early HIV progression in children who received PZP as in children who did not receive PZP.

CONCLUSIONS

In our population-based cohort of perinatally HIV-infected children, those who received PZP started ART at a significantly earlier age than those who did not receive PZP and also demonstrated decreased HIV disease progression by the age of 3 years.

Pharmacokinetics of didanosine and drug resistance mutations in infants exposed to zidovudine during gestation or postnatally and treated with didanosine or zidovudine in the first three months of life

BACKGROUND

There are limited numbers of drugs that are available in formulations that are appropriate for neonates and few studies assessing resistance among infants born to human immunodeficiency virus (HIV)-infected women.

METHODS

Pharmacokinetics and tolerance of didanosine (ddI) were determined for infants < or =120 days of age. Infants received at least 24 hours of zidovudine (ZDV) treatment, followed by a single ddI dose and pharmacokinetic sampling. The target area under the concentration-time curve (AUC) was between 2.5 and 5.0 microM . hour. Toxicity and drug resistance mutations were assessed at baseline and follow-up times.

RESULTS

The initial ddI pharmacokinetic dosing of 50 mg/m for infants >28 days of age achieved a median AUC0-infinity of 2.8 microM . hour. For infants < or =28 days of age, the target AUC was achieved after dose escalation from 25 mg/m (median AUC0-infinity, 1.4 microM . hour) to 50 mg/m (median AUC0-infinity, 5.40 microM . hour). At baseline, 25% of infected infants had drug resistance mutations (9 of 44 to ZDV and 2 of 44 to ddI). Resistance mutations were present for 29% of infants (5 of 17 infants) with in utero ZDV exposure and 25% (8 of 32 infants) with prior ZDV treatment. The most common ZDV mutation noted at baseline was the T215Y/F (n = 7) mutation; 2 of these infants also had the M41L mutation, which is associated with high level ZDV resistance. No prior exposure was noted for the 2 infants with ddI resistance, which indicates possible perinatal transmission of ddI-resistant virus to these infants.

CONCLUSIONS

A dose of 50 mg/m is the appropriate ddI dose for infants <120 days of age and is a safe treatment for newborns when used in combination with ZDV. Genotypic resistance occurs frequently among infected infants exposed to ZDV during gestation or postnatally, which suggests that resistance testing should be considered for infants with newly diagnosed HIV infection.

Pediatric HIV infection and treatment

Knowledge regarding the basic mechanisms of pediatric HIV infection and its prevention and treatment has expanded greatly in the last decade. Significant questions remain and have been largely refocused to the complexities of a chronic disease process. Management invariably requires specialists who must keep abreast of a rapidly evolving information base.

Perinatal Transmission of HIV: Recognition and Treatment Interventions

Great strides have been made in the fight against vertical transmission of HIV-1. Improved understanding of mechanisms and timing of transmission of HIV-1 from mother to child have led to the development of effective intervention strategies that have reduced transmission rates to unprecedented low levels, below 2% in developed countries. New reports using shortened, more affordable courses of antiretrovirals prenatally or at the time of delivery have also shown a significant reduction in transmission, over 50% in studies conducted in the developing world. These advances, combined with ongoing studies using simplified effective treatment regimens, have made possible the potential to significantly reduce perinatal transmission worldwide. Future challenges include reduction of breast feeding transmission and the development of an effective HIV-1 vaccine to produce long-lasting protection.

18-Month mortality and perinatal exposure to zidovudine in West Africa

OBJECTIVES

To study mortality in African children born to HIV-1-infected mothers exposed peripartum to zidovudine.

METHODS

A randomized placebo-controlled trial in Abidjan and Bobo-Dioulasso. Pregnant women received either 300 mg zidovudine twice daily from 36-38 weeks' gestation, 600 mg during labour, and 300 mg twice daily for 7 days post-partum or a matching placebo. Determinants of mortality were studied up to 18 months, overall and among the infected children: treatment, centre, timing of infection, mother and child HIV disease.

RESULTS

There were 75 infant deaths among 407 live births. The risk of death at 18 months was 176/1000 in the zidovudine arm and 221 for placebo. Relative hazard (RH, zidovudine versus placebo) was 0.47 [95% confidence interval (CI) 0.2-1.0] up to 230 days of life. Maternal CD4 lymphocyte count < 200/mm3 (RH 2.92; CI 1.4-6.1) and child HIV-1 infection (RH 12.6; CI 6.6-24.3) increased mortality of all children born to HIV-1-infected mothers. There were 101 children infected (40 in the zidovudine group), and 51 died. Their 18 month probability of death was 590/1000 in the zidovudine group and 510 in the placebo group. Among infected children, maternal zidovudine reduced the risk of death on or before day 230 (RH 0.18; CI 0.1-0.5). Maternal CD4 lymphocyte count < 200/mm3 (RH 3.25; CI 1.3-8.4), maternal death (RH 9.65; CI 1.7-56.0), diagnosis of paediatric infection on or before day 12 (RH 18.1; CI 4.8-69.0) and between days 13 and 45 (RH 7.63; CI 2.0-29.5), clinical paediatric AIDS (RH 5.37; CI 2.3-12.7) were risk factors for death in HIV-1-infected children.

CONCLUSION

Mother-to-child transmission reduction by zidovudine is safe and beneficial to African children. The mortality of HIV-1-infected children is high. Peripartum maternal zidovudine exerts a protective effect for at least 8 months.

Safety of late in utero exposure to zidovudine in infants born to human immunodeficiency virus-infected mothers: Bangkok. Bangkok Collaborative Perinatal HIV Transmission Study Group

BACKGROUND

Short-course zidovudine (ZDV) given in the late antenatal period can reduce mother-infant human immunodeficiency virus (HIV) transmission by one half. Because this intervention is being implemented in developing countries, evidence of its safety is needed.

METHODS

In a randomized, double-blinded, placebo-controlled trial in Bangkok, HIV-infected pregnant women received either ZDV (300 mg twice daily from 36 weeks' gestation until labor, then every 3 hours until delivery) or an identical placebo regimen. Infants were evaluated at birth and at 1, 2, 4, 6, 9, 12, 15, and 18 months of age. Growth, clinical events, and hematologic and immunologic measurements were compared between treatment groups.

RESULTS

Of the 395 children born (196 in ZDV group and 199 in placebo group), 330 were uninfected, 55 were infected, and 10 had indeterminate infection status. Overall, 319 children (81%) completed 18 months of follow-up, and 14 (4%) died before 18 months of age. Among uninfected children, the mean hematocrit was lower in the ZDV group at birth (49.1% vs 51.5%) but not at later ages; mean weight, height, head circumference, and CD4(+) and CD8(+) T lymphocyte counts were similar in both groups at all ages. Five uninfected children in the ZDV group but only one in the placebo group had a febrile convulsion. No other signs suggestive of mitochondrial dysfunction and no tumors were observed. Among infected children, an estimated 62% in the ZDV group and 77% in the placebo group survived free of Centers for Disease Control and Prevention class C disease during the 18-month follow-up.

CONCLUSIONS

No significant adverse events were associated with short-course ZDV during 18 months of follow-up in this population.

Vertical human immunodeficiency virus type 1--HIV-1--transmission--a review

Several factors appear to affect vertical HIV-1 transmission, dependent mainly on characteristics of the mother (extent of immunodeficiency, co-infections, risk behaviour, nutritional status, immune response, genetical make-up), but also of the virus (phenotype, tropism) and, possibly, of the child (genetical make-up). This complex situation is compounded by the fact that the virus may have the whole gestation period, apart from variable periods between membrane rupture and birth and the breast-feeding period, to pass from the mother to the infant. It seems probable that an extensive interplay of all factors occurs, and that some factors may be more important during specific periods and other factors in other periods. Factors predominant in protection against in utero transmission may be less important for peri-natal transmission, and probably quite different from those that predominantly affect transmission by mothers milk. For instance, cytotoxic T lymphocytes will probably be unable to exert any effect during breast-feeding, while neutralizing antibodies will be unable to protect transmission by HIV transmitted through infected cells. Furthermore, some responses may be capable of controlling transmission of determined virus types, while being inadequate for controlling others. As occurrence of mixed infections and recombination of HIV-1 types is a known fact, it does not appear possible to prevent vertical HIV-1 transmission by reinforcing just one of the factors, and probably a general strategy including all known factors must be used. Recent reports have brought information on vertical HIV-1 transmission in a variety of research fields, which will have to be considered in conjunction as background for specific studies.

Simple, sensitive, and specific detection of human immunodeficiency virus type 1 subtype B DNA in dried blood samples for diagnosis in infants in the field

The detection of virus is used to diagnose human immunodeficiency virus type 1 (HIV-1) infection in infants due to the persistence of maternal antibodies for a year or more. An HIV-1 DNA PCR assay with simple specimen collection and processing was developed and evaluated. Whole blood was collected on filter paper that lysed cells and bound the DNA, eliminating specimen centrifugation and extraction procedures. The DNA remained bound to the filter paper during PCR amplification. Assays of copy number standards showed reproducible detection of 5 to 10 copies of HIV-1 in 5 microl of whole blood. The sensitivity of the assay did not decrease after storage of the standards on filter paper for 3 months at room temperature or after incubation at 37 or 45 degrees C for 20 h. The primers used for nested PCR of the HIV-1 pol gene amplified templates from a reference panel of multiple HIV-1 subtypes but did not amplify a subtype A or a subtype C virus from children living in Seattle. The assay had a sensitivity of 98.4% and a specificity of 98.3% for testing of 122 specimens from 35 HIV-1-infected and 16 uninfected children and 43 seronegative adults living in Washington. The assay had a sensitivity of 99% and a specificity of 100% for testing of 102 HIV-1-positive (as determined by enzyme immunoassay) Peruvian women and 6 seropositive and 34 seronegative infants. This assay, with adsorption of whole blood to filter paper and no specimen processing, provides a practical, economical, sensitive, and specific method for the diagnosis of HIV-1 subtype B infection in infants.

An effective and safe protocol involving zidovudine and caesarean section to reduce vertical transmission of HIV-1 infection

OBJECTIVE

To investigate zidovudine prophylaxis with caesarean section to reduce mother-to-infant HIV transmission.

INTERVENTIONS

Elective caesarean section before labour, usually at 36-38 weeks of gestation, plus a short oral course of zidovudine, normally starting at week 32, intravenous zidovudine before caesarean section and for 10 days for the neonate (the reduced Berlin regimen).

RESULTS

Of 179 mother-infant pairs 104 received no antiretroviral prophylaxis or therapy (control group), 48 received the reduced Berlin prophylaxis regimen, 18 received combination therapy and nine received only part of the prophylaxis regimen. Of the antiretroviral group, 68 were delivered by elective caesarean section. The HIV transmission rate was zero in the antiretroviral group [95% confidence interval (CI) 0-4.7] and 12.6% (6.4-19.0) in the control group. The reduction in vertical transmission was 90% for the Berlin regimen, with an 80 and 70% reduction in risk associated with antiretroviral treatment and caesarean section, respectively. Maternal CD4 cell count but not viral load had some confounding effect on the reduction in risk attributed to caesarean section and the prophylactic regimen. Neonatal haematological abnormalities associated with antiretroviral intervention lasted for up to 7 weeks. Weight and length, although significantly lower at birth, were normal by 6-8 weeks.

CONCLUSION

A much reduced three-arm regimen of zidovudine prophylaxis in combination with caesarean section before labour is highly effective in reducing the risk of vertical HIV transmission and is safe for the infant.

Technical report: perinatal human immunodeficiency virus testing and prevention of transmission. Committee on Pediatric Aids

In 1994, the US Public Health Service published guidelines for the use of zidovudine to decrease the risk of perinatal transmission of human immunodeficiency virus (HIV). In 1995, the American Academy of Pediatrics and the US Public Health Service recommended documented, routine HIV education and testing with consent for all pregnant women in the United States. Widespread incorporation of these guidelines into clinical practice has resulted in a dramatic decrease in the rate of perinatal HIV transmission and has contributed to more than a 75% decrease in reported cases of pediatric acquired immunodeficiency syndrome (AIDS) since 1992. Substantial advances have been made in the treatment and monitoring of HIV infection; combination antiretroviral regimens that maximally suppress virus replication are now available. These regimens are recommended for pregnant and nonpregnant individuals who require treatment. Risk factors associated with perinatal HIV transmission are now better understood, and recent results from trials to decrease the rate of mother-to-child HIV transmission have contributed new strategies with established efficacy. However, perinatal HIV transmission still occurs; the Centers for Disease Control and Prevention estimates that 300 to 400 infected infants are born annually. Full implementation of recommendations for universal, routine prenatal HIV testing and evaluation of missed prevention opportunities will be critical to further decrease the incidence of pediatric HIV infection in the United States. This technical report summarizes recent advances in the prevention of perinatal transmission of HIV relevant to screening of pregnant women and their infants.

Performance characteristics of the QUANTIPLEX HIV-1 RNA 3.0 assay for detection and quantitation of human immunodeficiency virus type 1 RNA in plasma

The QUANTIPLEX HIV-1 RNA assay, version 3.0 (a branched DNA, version 3.0, assay [bDNA 3.0 assay]), was evaluated by analyzing spiked and clinical plasma samples and was compared with the AMPLICOR HIV-1 MONITOR Ultrasensitive (ultrasensitive reverse transcription-PCR [US-RT-PCR]) method. A panel of spiked plasma samples that contained 0 to 750,000 copies of human immunodeficiency virus type 1 (HIV-1) RNA per ml was tested four times in each of four laboratories (1,344 assays). Negative results (<50 copies/ml) were obtained in 30 of 32 (94%) assays with seronegative samples, 66 of 128 (52%) assays with HIV-1 RNA at 50 copies/ml, and 5 of 128 (4%) assays with HIV-1 RNA at 100 copies/ml. The assay was linear from 100 to 500,000 copies/ml. The within-run standard deviation (SD) of the log(10) estimated HIV-1 RNA concentration was 0.08 at 1,000 to 500,000 copies/ml, increased below 1,000 copies/ml, and was 0.17 at 100 copies/ml. Between-run reproducibility at 100 to 500 copies/ml was <0.10 log(10) in most comparisons. Interlaboratory differences across runs were </=0.10 log(10) at all concentrations examined. A subset of the panel (25 to 500 copies/ml) was also analyzed by the US-RT-PCR assay. The within-run SD varied inversely with the log(10) HIV-1 RNA concentration but was higher than the SD for the bDNA 3.0 assay at all concentrations. Log-log regression analysis indicated that the two methods produced very similar estimates at 100 to 500 copies/ml. In parallel testing of clinical specimens with low HIV-1 RNA levels, 80 plasma samples with <50 copies/ml by the US-RT-PCR assay had <50 copies/ml when they were retested by the bDNA 3.0 assay. In contrast, 11 of 78 (14%) plasma samples with <50 copies/ml by the bDNA 3.0 assay had >/=50 copies/ml when they were retested by the US-RT-PCR assay (median, 86 copies/ml; range, 50 to 217 copies/ml). Estimation of bDNA 3.0 values of <50 copies/ml by extending the standard curve of the assay showed that these samples with discrepant results had higher HIV-1 RNA levels than the samples with concordant results (median, 34 versus 17 copies/ml; P = 0.0051 by the Wilcoxon two-sample test). The excellent reproducibility, broad linear range, and good sensitivity of the bDNA 3.0 assay make it a very attractive method for quantitation of HIV-1 RNA levels in plasma.