Defining the time of fetal or perinatal acquisition of human immunodeficiency virus type 1 infection on the basis of age at first positive culture. Women and Infants Transmission Study (WITS)

Minimizing the Risk of Perinatal Human Immunodeficiency Virus Transmission

Importance

There are approximately 284,500 adolescent and adult women living with human immunodeficiency virus (HIV) in the United States. It is estimated that approximately 8500 of these women give birth annually. While the rate of perinatal transmission in the United States has decreased by more than 90% since the early 1990s, potentially preventable HIV transmission events still occur and cause significant morbidity and mortality.

Objective

The aim of this review was to summarize the current data regarding perinatal HIV transmission timing and risk factors, current management recommendations, and implications of timing of transmission on patient management.

Evidence Acquisition

Literature review.

Results

This review reiterates that the risk of perinatal HIV transmission can be reduced to very low levels by following current recommendations for screening for HIV in all pregnant women and properly treating HIV-infected mothers, as well as using evidence-based labor management practices.

Conclusions and Relevance

Familiarity with the pathogenesis of HIV transmission is important for obstetric care providers to appropriately manage HIV-infected women in pregnancy, intrapartum, and the postpartum period.

The pharmacological treatment of acute HIV infections in neonates

INTRODUCTION

Recent goals of antiretroviral treatment of neonates have expanded from reducing morbidity and mortality to also aiming to facilitate HIV remission. Areas covered: In this review, we present and discuss the rationale and evidence-bases for each of these distinct goals. Next we discuss the challenges of how to identify HIV-infected neonates. Finally, we discuss the specific antiretroviral drugs that are preferred for this group, making distinctions between the use of these agents in prevention and treatment. Expert commentary: The clinical and scientific challenges of pharmacological treatment of acute HIV infection in neonates are complicated by externalities beyond biology. At the same time, these challenges are energized by the unique biological opportunities afforded by investigating this population, including a unique immune profile, ability to study both mother and neonate as well as transmitted and acquired virus, and time period spanning both the period soon after infection as well as the period of viral reservoir establishment and related damage. Given the unique scientific opportunities afforded by study of pharmacologic treatment of acute HIV infection in neonates, we hypothesize that over the next five years breakthroughs may occur that may lead to new interventions effective at achieving HIV remission.

Low concentrations of HIV-1 DNA at birth delays diagnosis, complicating identification of infants for antiretroviral therapy to potentially prevent the establishment of viral reservoirs

Among infants exposed to human immunodeficiency virus type 1 (HIV-1), detection of viral infection at birth was increased by 39% (95% confidence interval, 19%-47%) by increasing DNA input from dried blood spots into polymerase chain reaction. Infants with low concentrations of HIV-1 at birth may be the best target population to evaluate whether immediate antiretroviral therapy can prevent long-term infection.

Pregnant women's access to PMTCT and ART services in South Africa and implications for universal antiretroviral treatment

OBJECTIVES

We describe pregnant womens' access to PMTCT and HAART services and associated birth outcomes in South Africa.

METHODS

Women recuperating in postnatal wards of a referral hospital participated in an evaluation during February-May 2010 during which their maternity records were examined to describe their access to VCT, CD4 Counts, dual ART or HAART during pregnancy.

RESULTS

Of the 1609 women who participated in this evaluation, 39% (95%CI36.7-41.5%) tested HIV-positive during their pregnancy. Of the HIV-positive women 2.9% did not have a CD4 count done and an additional 31.3% did not receive their CD4 results. The majority (96.8%) of the HIV-positive women commenced dual ART at their first antenatal visit independent of their CD4 result. During February-May 2010, 48.0% of the women who had a CD4 result were eligible for HAART (CD4<200 cells/mm(3)) and 29.1% of these initiated HAART during pregnancy. Under the current South African PMTCT guidelines 71.1% (95%CI66.4-75.4%) of HIV positive pregnant women could be eligible for HAART (CD4<350 cells/mm(3)). There were significantly more preterm births among HIV-positive women (p = 0.01) and women who received HAART were no more at risk of preterm deliveries (AOR 0.73;95%CI0.39-1.36;p = 0.2) as compared to women who received dual ART. Nine (2.4%; 95%CI1.1-4.5%) HIV exposed infants were confirmed HIV infected at birth. The in-utero transmission rate was highest among women who required HAART but did not initiate treatment (8.5%) compared to 2.7% and 0.4% among women who received HAART and women who were not eligible for HAART and received PMTCT prophylaxis respectively.

CONCLUSION

In this urban South African community the antenatal HIV prevalence remains high (39%) and timeous access to CD4 results during pregnancy is limited. Under the current South African guidelines, and assuming that access to CD4 results has improved, more than 70% of HIV-positive pregnant women in this community would be requiring HAART.

Human immunodeficiency virus type 1 mother-to-child transmission and prevention: successes and controversies

The World Health Organization (WHO) and United Nations Programme on HIV/AIDS (UNAIDS) estimated that an additional 370 000 new human immunodeficiency virus type 1 (HIV-1) infections occurred in children in 2009, mainly through mother-to-child transmission (MTCT). Intrapartum transmission contributes to approximately 20-25% of infections, in utero transmission to 5-10% and postnatal transmission to an additional 10-15% of cases. MTCT accounts for only a few hundred infected newborns in those countries in which services are established for voluntary counselling and testing of pregnant women, and a supply of antiretroviral drugs is available throughout pregnancy with recommendations for elective Caesarean section and avoidance of breastfeeding. The single-dose nevirapine regimen has provided the momentum to initiate MTCT programmes in many resource-limited countries; however, regimens using a combination of antiretroviral drugs are needed also to effectively reduce transmission via breastfeeding.

Prevention of mother-to-child transmission of HIV-1: the role of cesarean delivery

The risk of mother-to-child transmission (MTCT) of HIV can be reduced through cesarean delivery prior to the onset of labor and prior to rupture of the membranes (elective cesarean delivery [ECD]). As a result of this evidence, the American College of Obstetricians and Gynecologists and the Department of Health and Human Services Panel on Treatment of HIV-Infected Pregnant Women and Prevention of Perinatal Transmission developed guidelines recommending ECD for HIV-infected women with plasma viral loads of more than 1000 copies/mL. Since the release of the recommendations, an increase in ECD has been seen among HIV-infected women in the United States. This article discusses the evidence on efficacy of ECD, current recommendations in the United States, and risks and morbidity related to ECD. Although the benefit of ECD in preventing MTCT of HIV is substantial, some questions remain. Specifically, the benefit of ECD for women with very low viral loads or for women using combination antiretroviral regimens is unclear, as is the timeframe after onset of labor or rupture of membranes within which ECD will still confer preventive benefits.

Mother-to-child transmission of HIV: pathogenesis, mechanisms and pathways

More than 400,000 children were infected with (HIV-1) worldwide in 2008, or more than 1000 children per day. Mother-to-child transmission (MTCT) of HIV-1 is the most important mode of HIV acquisition in infants and children. MTCT of HIV-1 can occur in utero, intrapartum, and postnatally through breastfeeding. Great progress has been made in preventing such transmission, through the use of antiretroviral prophylactic regimens to the mother during gestation and labor and delivery and to either mother or infant during breast feeding. The timing and mechanisms of transmission, however, are multifactorial and remain incompletely understood. This article summarizes what is known about the pathogenetic mechanisms and routes of MTCT of HIV-1, and includes virologic, immunologic, genetic, and mucosal aspects of transmission.

Analysis of time to a silent event whose occurrence is monitored with error, with application to mother-to-child HIV transmission

Inferences about the distribution of time to HIV infection in infants are complicated because infection is a silent event and imperfect diagnostic tests are used to detect its occurrence, leading to false-positive and false-negative results. Nonparametric likelihood approaches are computationally hampered by a large number of parameters and a possibly nonconcave likelihood function. To overcome these difficulties, we develop one-sample and regression methods based on profile likelihood and Markov chain Monte Carlo techniques. The methods also provide a useful diagnostic for assessing the infection status of individual subjects, and are illustrated using results from a recent clinical trial for the prevention of mother-to-child HIV transmission.

Paucity of CD4+ CCR5+ T cells may prevent transmission of simian immunodeficiency virus in natural nonhuman primate hosts by breast-feeding

Simian immunodeficiency virus (SIV) persistence in wild populations of African nonhuman primates (NHPs) may occur through horizontal and vertical transmission. However, the mechanism(s) and timing of the latter type of transmission have not been investigated to date. Here we present the first study of SIV transmissibility by breast-feeding in an African NHP host. Six mandrill dames were infected with plasma containing 300 50% tissue culture infective doses of SIVmnd-1 on the day after delivery. All female mandrills became infected, as demonstrated by both plasma viral loads (VLs) and anti-SIVmnd-1 seroconversion. Neither fever nor lymphadenopathy was observed. At the peak of SIVmnd-1 viral replication (days 7 to 10 postinoculation), plasma VLs were high (8 x 10(6) to 8 x 10(8) RNA copies/ml) and paralleled the high VLs in milk (4.7 x 10(4) to 5.6 x 10(5) RNA/ml). However, at the end of the breast-feeding period, after 6 months of follow-up, no sign of infection was observed for the offspring. Later on, during a 4-year follow-up examination, two of the offspring showed virological evidence of SIVmnd-1 infection. Both animals seroconverted at least 6 months after the interruption of lactation. In conclusion, despite extensive viral replication in mandrill mothers and high levels of free virus in milk, no SIVmnd-1 transmission was detectable at the time of breast-feeding or during the following months. Since we observed a markedly lower expression of CCR5 on the CD4(+) T cells of young mandrills and African green monkeys than on those of adults, we propose that low levels of this viral coreceptor on CD4(+) T cells may be involved in the lack of breast-feeding transmission in natural hosts of SIVs.

Fetal cord blood mononuclear cells that are collected at term from HIV-1 infected women harbor transcriptionally active integrated proviral DNA

OBJECTIVE

The purpose of this study was to determine levels of intrauterine infection and transcriptional activity in cord blood mononuclear cells that were collected at term from fetuses who were born to women who were infected with human immunodeficiency virus (HIV) and who received highly active antiretroviral therapy (HAART).

STUDY DESIGN

RNA and DNA were isolated from maternal placental tissues and fetal cord blood specimens that were obtained at term from pregnant women who were infected with HIV and who received HAART. Levels of integrated HIV provirus and messenger RNA transcripts were determined by real-time polymerase chain reaction.

RESULTS

Detectable levels of transcriptionally active integrated provirus were present in approximately 27% of cord blood samples (n = 22) that were collected from fetuses who born to HIV-positive mothers who received HAART. Levels of HIV-p24 antigen in cultures that were detected in randomly selected cord blood samples confirmed the presence of inducible infectious virus.

CONCLUSION

These findings suggest that some fetuses from HIV-infected mothers who receive HAART and who may be HIV-negative infants after delivery can harbor circulating leukocytes that are infected productively by intrauterine transmission of HIV.

Maternal HIV-1 DNA load and mother-to-child transmission

While many factors contribute to mother-to-child transmission (MTCT) of HIV-1, maternal plasma HIV-1 RNA viral load (RNA-VL) has been consistently found as the main risk factor, including when antiretroviral prophylaxis was used to prevent MTCT. However the predictive value of RNA-VL is poor. A recent study of HIV-1-positive pregnant women who did not receive antiretroviral prophylaxis reported an association between HIV-1 DNA viral load (DNA-VL) and MTCT that was stronger than the association between RNA-VL and MTCT. We sought to determine if HIV-1 DNA-VL was independently associated with MTCT of HIV in a population of women who received zidovudine prophylaxis during pregnancy and whose infants received zidovudine after birth. Patients were 33 non-breastfeeding transmitting (TR) and 33 nontransmitting mothers (NTR) from Perinatal HIV Prevention Trial (PHPT-1), a multicenter clinical trial conducted in Thailand comparing zidovudine prophylaxis durations to prevent MTCT. TR and NTR mothers were matched according to baseline RNA-VL. Maternal peripheral blood mononuclear cell (PBMC)-associated HIV-1 DNA was extracted from whole blood, and DNA-VL was established by quantitative real-time polymerase chain reaction. We found that TR had a significantly higher cell-associated HIV-1 DNA viral load than did NTR. Median TR DNA-VL was 2.54 log(10) copies per microgram PBMC DNA, while it was 2.28 log(10) copies per microgram PBMC DNA in NTR (Wilcoxon p = 0.02). In summary, HIV-1 DNA viral load was associated with MTCT in a population of women who received antiretroviral prophylaxis during pregnancy, independently from RNA viral load.

Modeling Maternal-Infant HIV Transmission in the Presence of Breastfeeding with an Imperfect Test

An important public health question is to determine the probabilities of perinatal HIV transmission and when it occurs, whether antepartum, intrapartum, or postpartum through breastfeeding. However, this is a difficult problem because the presence of HIV infection in an infant can only be ascertained through viral assays in the postpartum period. We propose a model that simultaneously estimates the risks of antepartum, intrapartum, and postpartum transmissions together with the sensitivity of the screening tests for HIV infection. The model allows estimating of infectivity through breast milk during postpartum periods. The methods are illustrated on a South African randomized clinical trial of extended AZT versus a short course of nevirapine in infants whose mothers had no access to antenatal antiretroviral therapy.

Care and management of the infant of the HIV-1-infected mother

Mother-to-child transmission of the human immunodeficiency virus continues to be a major global health problem. The pediatric HIV-1 epidemic is fueled by HIV-1 infection in women of childbearing age with vertical transmission in utero or at the time of birth. In resource-rich countries, the birth of an infected child is a sentinel health event signaling a chain of missed opportunities and barriers to prevention. Because the fate and ultimate HIV-infection status of the baby is inextricably linked to the infection status of the mother and her general state of well-being, we provide in this review: 1) background and state-of-the-art management guidelines for optimum maternal care; 2) strategies to minimize the risk of vertical transmission of HIV; and 3) recommendations for managing infants born to HIV-infected women. These are discussed under four case scenarios that obstetric and pediatric providers frequently encounter in their practices.

Problems in Diagnosis of HIV Infection in Babies

Serological diagnosis of human immunodeficiency virus (HIV) infection in babies born to HIV infected mothers is difficult because of presence of maternal anti-HIV antibody up to 18 months. Conventional enzyme-linked immunosorbent assay (ELISA) and western blot may be positive in un-infected cases. Various other modalities which have been adopted include detection of HIV specific IgA, IgM, IgE, detection of p24 antigen, viral culture and detection of HIV nucleic acid by polymerase chain reaction (PCR). Viral culture or PCR positivity within first 48 hours of life indicates intrauterine infection. An early diagnosis of HIV infection in babies born to HIV infected mothers is essential as definite antiretroviral therapy (ART) can be instituted and unnecessary toxicity of drug therapy avoided if found negative. Though viral culture and DNA-PCR has sensitivity of >95% after one month of age, some cases can not be diagnosed during this period. Other tests like viral RNA detection by reverse transcription polymerase chain reaction (RT-PCR) and combination of tests will be required.

HIV prevalence, sociodemographic, and behavioral correlates and recruitment methods among injection drug users in St. Petersburg, Russia

OBJECTIVE

In St. Petersburg, Russia, we sought to describe the characteristics of active high-risk injection drug users (IDUs) to evaluate the associations between behavioral and demographic characteristics and HIV-1 infection and to describe 3 discrete recruitment methods.

METHODS

Active high-risk IDUs were recruited in 3 ways: through street outreach, at facilities serving IDUs, and by network-based chain referral. Recruits were screened, counseled, and tested for HIV-1. Sociodemographic and behavioral data were collected. HIV-1 prevalence was analyzed as a function of sociodemographic and behavioral variables.

RESULTS

During the 10-month recruitment period, data from 900 participants were collected: median age was 24 years, and in the previous month, 96% used heroin and 75% shared needles with others. The baseline HIV prevalence was 30% (95% confidence interval [CI]: 27 to 33). Recruitment through social networks was the most productive strategy. HIV-positive individuals were younger, but none of the other sociodemographic or behavioral characteristics differed significantly by HIV status.

CONCLUSIONS

The estimated HIV prevalence of 30% places St. Petersburg among the worst IDU-concentrated epidemics in Europe. Recruitment through network-based chain referral is a useful method for recruiting active IDUs. Sociodemographic and behavioral links to prevalent HIV infection remain to be elucidated.

Risk factors for in utero and intrapartum transmission of HIV

OBJECTIVE

To identify predictors of in utero and intrapartum HIV-1 transmission in infants born in the Women and Infants Transmission Study between 1990 and 2000.

METHODS

In utero HIV-1 infection was defined as an infant with the first positive HIV-1 peripheral blood mononuclear cell culture and/or DNA polymerase chain reaction assay at 7 days of age or younger; intrapartum infection was defined as having a negative HIV-1 culture and/or DNA polymerase chain reaction assay at 7 days of age or younger and the first positive assay after 7 days of age.

RESULTS

Of 1709 first-born singleton children with defined HIV-1 infection status, 166 (9.7%) were found to be HIV-1 infected; transmission decreased from 18.1% in 1990-1992 to 1.6% in 1999-2000. Presumed in utero infection was observed in 34% of infected children, and presumed intrapartum infection, in 66%. Among infected children, the proportion with in utero infection increased over time from 27% in 1990-1992 to 80% (4 of 5) in 1999-2000 (P = 0.072). Maternal antenatal viral load and antiretroviral therapy were associated with risk of both in utero and intrapartum transmission. Controlling for maternal antenatal viral load and antiretroviral therapy, low birth weight was significantly associated with in utero transmission, while age, antenatal CD4 cell percentage, year, birth weight, and duration of membrane rupture were associated with intrapartum transmission.

CONCLUSION

Although there have been significant declines in perinatal HIV-1 infection over time, there has been an increase in the proportion of infections transmitted in utero.

Influence of Mother and Infant Zidovudine Treatment Duration on the Age at Which HIV Infection Can be Detected by Polymerase Chain Reaction in Infants

Objective

To investigate the influence of zidovudine (ZDV) prophylaxis duration in mothers and infants on the age at which infection becomes detectable by DNA polymerase chain reaction (PCR) in non-breastfed infants.

Methods

Blood samples were collected sequentially from birth to 6 months in a Thailand perinatal HIV prevention trial in which 98 transmissions occurred. The proportions of infections detectable at birth and the Turnbull distributions of age at which infection became detectable after birth were compared according to actual ZDV treatment duration (mothers: no more than 7.5 weeks versus more; infants: 3 days versus at least 4 weeks), provided an adherence greater than 75%.

Results

Detectable infection at birth was less frequent in children whose mothers received a long treatment as compared to a short treatment (27 vs 50%, P=0.04). When mothers received a long treatment, infant ZDV treatment duration did not influence the distribution of age at which infection became detectable after birth (median 24 days). However, when mothers received a short treatment, this distribution was shifted to the right when infants received a long treatment (median 43 days, P<0.0001), and to the left when infants received a short treatment (median 11 days, P<0.0001).

Conclusions

When mothers receive a short treatment, the proportion of infections detectable at birth is higher and the time at which infection becomes detectable after birth depends on the infant treatment duration. In the study conditions, a PCR result after 2 months could be used to define infection status.

Prevention of perinatal HIV transmission: current status and future developments in anti-retroviral therapy

Significant progress has been made in the battle against transmission of HIV-1 from mother to infant. Antiretroviral regimens covering the later part of gestation, labour and the first few weeks of neonatal life have shown great efficacy in reducing such transmission. With the advent of combination antiretroviral therapies, transmission rates lower than 2% have been achieved in clinical studies. Elective caesarean delivery has been shown to enhance the benefit of antiretroviral regimens; however, the risks associated with this approach in many resource-poor settings in developing countries limit its role worldwide. Abbreviated antiretroviral regimens covering labour and the first few days of neonatal life have shown considerable promise in the developing world, resulting in 50% reduction in transmission. Several questions and challenges remain, however. Amongst them, choice of the optimal antiretroviral agent(s), evaluation of purely post-exposure neonatal prophylaxis, availability of antiretroviral agents in developing countries, long-term safety of antiretroviral therapy during pregnancy and early neonatal life, and the problem of breastfeeding transmission in the developing world are some issues that need urgent attention.

Short-course therapy with zidovudine plus lamivudine for prevention of mother-to-child transmission of human immunodeficiency virus type 1 in Thailand

To evaluate the efficacy and safety of short-course therapy with zidovudine plus lamivudine for reduction of perinatal transmission of human immunodeficiency virus type 1 (HIV-1), a single-arm, open-label, prospective, nonrandomized study was conducted. One hundred six treatment-naive pregnant women received zidovudine (300 mg) plus lamivudine (150 mg) twice daily from week 34 of gestation until the onset of labor. During labor, zidovudine and lamivudine were given every 3 h. Neonates received zidovudine syrup for 4 weeks and were bottle fed. The median maternal virus load and CD4+ cell count at weeks 32-34 of gestation were 4.33 log10 copies/mL and 274 cells/mm3, respectively. At delivery, the mothers' mean decrease in virus load was 1.55 log10 copies/mL and the mean increase in CD4+ cell count was 93 cells/mm3, compared with enrollment levels. Three neonates were HIV-1 infected, for a transmission rate of 2.83% (95% confidence interval, 1%-8%). There were no serious adverse events in the mothers. Adverse events noted in neonates were anemia (in 6 neonates), elevated transaminase levels (in 1), and thrombocytopenia (in 3). Short-course therapy with zidovudine plus lamivudine appeared to be safe and effective for prevention of perinatal transmission of HIV-1.

Vertical transmission of human immunodeficiency virus

Sensitive detection methods, such as DNA PCR and RNA PCR suggest that vertical transmission of human immunodeficiency virus (HIV) occurs at three major time periods; in utero, around the time of birth, and postpartum as a result of breastfeeding (Fig. 1). Detection of proviral DNA in infant's blood at birth suggests that transmission occurred prior to delivery. A working definition for time of infection is that HIV detection by DNA PCR in the first 48 h of life indicates in utero transmission, while peripartum transmission is considered if DNA PCR is negative the first 48 h, but then it is positive 7 or more days later [1]. Generally, in the breastfeeding population, breast milk transmission is thought to occur if virus is not detected by PCR at 3-5 months of life but is detected thereafter within the breastfeeding period [2]. Using these definitions and guidelines, studies has suggested that in developed countries the majority, or two thirds of vertical transmission occur peripartum, and one-third in utero [3-6]. The low rate of breastfeeding transmission is due to the practice of advising known HIV-positive mothers not to feed breast milk. However, since the implementation of antiretroviral treatment in prophylaxis of HIV-positive mothers, some studies have suggested that in utero infection accounts for a larger percentage of vertical transmissions [7]. In developing countries, although the majority of infections occurs also peripartum, a significant percentage, 10-17%, is thought to be due to breastfeeding [2, 8, 9].

Options for prevention of HIV transmission from mother to child, with a focus on developing countries

Use of antiretroviral drugs among HIV-infected pregnant women in many developed countries has significantly reduced rates of mother-to-child HIV transmission, demonstrating that this route of transmission is amenable to intervention. Prevention of transmission in developing countries has proved to be more difficult, although recent advances in short-course antiretroviral drug interventions have made it an immediate possibility, rather than a distant hope as it was seen to be in the recent past. Non-antiretroviral drug interventions, including washing of the birth canal with antiseptic solution and micronutrient supplementation, have not been found to be effective at interrupting mother-to-child HIV transmission, but may have other benefits for maternal and child health. An important issue for developing countries is prevention of postnatal HIV transmission through breast feeding. In most developing countries, formula feeding is not a reasonable option, given the higher rates of mortality from diarrheal and respiratory disease associated with avoidance of all breast feeding. A promising new line of research has recently been broached with the findings from a study in South Africa, which demonstrated that exclusive breast feeding is associated with a significant reduction in postnatal transmission of HIV.

The role of non-nucleoside reverse transcriptase inhibitors in children with HIV-1 infection

Over 1.4 million of the worlds' children are infected with HIV-1, mostly acquired in the perinatal period. Antiviral therapeutic options for children with HIV-1 infection have lagged behind those for infected adults. However, we now know that prevention of perinatal HIV-1 transmission to children is possible and that combination therapy for the management of infected children is efficacious. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are developing a more prominent role in combination therapy regimens, particularly as alternatives to protease inhibitors. They also have a role in preventing perinatal transmission, where it has been shown that only 2 doses of the NNRTI nevirapine can significantly reduce mother-to-child transmission of HIV-1. This has major therapeutic implications, particularly in areas where combination therapy is not readily available. Palatable paediatric formulations of NNRTIs are available or are being developed. Whilst pharmacokinetic data regarding the use of antiretrovirals in children remain scarce, published clinical trials have demonstrated the efficacy of NNRTIs when used as part of combination regimens in the management of HIV-1 infected children. The toxicity profile of NNRTIs is relatively favourable; however, severe skin rash, hepatotoxicity and central nervous system adverse effects with various NNRTIs can lead to treatment cessation. The development of class resistance with single step mutations in the reverse transcriptase gene remains a major therapeutic problem with this class of antiretrovirals. Novel NNRTIs under development are of interest either because of improved pharmacodynamics, reduced toxicity profiles or because of action against NNRTI-mutation containing resistant virus. There are no data available yet on the use of these drugs in the paediatric population.

Human immunodeficiency virus (HIV)-specific cellular immune responses in newborns exposed to HIV in utero

Significant immunological changes are associated with intrauterine human immunodeficiency virus (HIV) encounter among uninfected infants of HIV-infected mothers. Peripheral blood cells of more than one-third of these exposed-uninfected infants proliferate and produce IL-2 after stimulation with HIV, and HIV-specific CD4+ T helper cell responses can be quantified in nearly all when sensitive intracellular cytokine assays are used. HIV-specific CD8+ cytotoxic T lymphocyte responses can be elicited in some, although less frequently. It is difficult to demonstrate that these responses are components of protective immunity and not simply epiphenomena of exposure. However, HIV-specific responses are associated with lack of infection, even with prolonged reexposure through breast-feeding. Elevations in nonspecific markers of immune activation provide further corroboration, as do similar findings in adults, consistent across all known routes of HIV transmission. Many questions remain, but much can be learned from this special population that may be informative for development of effective immunity in response to HIV vaccines.

Estimation of the timing of perinatal transmission of HIV

Knowledge of the timing of perinatal transmission of HIV would be valuable for the determination and evaluation of preventive treatments and would shed light on the mechanism of transmission. Estimation of the distribution of the time of perinatal transmission is difficult, however, because tests of infection status can only be undertaken after birth. DNA and RNA polymerase chain reaction (PCR) assays and HIV culture have been the most commonly used diagnostic tests for perinatal HIV infection. Such tests have high sensitivity and specificity, except when they are given shortly after infection. In this paper we use the time-dependent sensitivity of these diagnostic tests to make nonparametric and semiparametric inferences about the distribution of the time of perinatal HIV transmission as well as the cumulative probability of perinatal transmission. The methods are illustrated with data from a clinical trial conducted by the AIDS Clinical Trials group.

Epidemiologic and clinical features of HIV-infected and HIV-uninfected Ugandan children younger than 18 months

METHODS

Groups of HIV-infected and HIV-uninfected infants younger than 18 months (mainly younger than 6 months) were compared to identify clinical features that could differentiate the two groups. The HIV-infected group also was compared with HIV-infected children older than 18 months. Recruitment was as follows for the group younger than 18 months: 708 children admitted with sepsis and clinical features suggestive of HIV infection were screened for HIV1 and HIV2 by HIV enzyme-linked immunosorbent assay (ELISA), and polymerase chain reaction (PCR) was undertaken on all ELISA-seropositive blood samples (270). HIV infection was confirmed in 136 (19.2%), 438 (61.9%) were HIV-seronegative, 27 (3.8%) were HIV seroreverters, 36 (5.1%) were HIV-seropositive but PCR negative (uninfected), and 71 (10.0%) were indeterminate. One hundred thirty-six HIV-infected children were compared with 501 uninfected children. Confirmed HIV-infected children older than 18 months attending the pediatric HIV clinic were compared with the 136 HIV-infected children younger than 18 months.

RESULTS

Under 18 months, the median age of HIV-infected children (n = 136) was 4.0 months (range, 3 d -18 mo ) and the median age of the uninfected children (n = 501) was 1.0 month (range, 3 d -18 mo ). HIV-infected children were more likely to have had injections, chloroquine, and nystatin, and to have attended a health center or hospital (p <.001). In the HIV-infected group, the Z score for weight-for-age was -1.75, length-for-age -0.78, and weight-for-length 1.86, significantly lower scores than those of the uninfected group, which were -0.60, -0.23, and 3.05, respectively (p <.05). The mean head circumference was below the third percentile in 40% of HIV-infected compared with 22% of uninfected children (p <.001). Overall, 56 (8%) children had marasmus, 6 (0.8%) kwashiorkor, and 3 (0.4%) marasmic kwashiorkor. Sixteen percent of the HIV-infected and 7% of uninfected children had marasmus (p <.05). The 1989 revised World Health Organization clinical criteria for diagnosis of AIDS had sensitivity, specificity, and positive predictive values of 28%, 98%, and 93%, respectively. Older than 18 months (n = 109), the median age was 24 months (range, 18-60 mo ). The following were significantly more common in HIV-infected children older than 18 months than in those younger than 18 months: bacille Calmette-Guérin vaccination scar, parotid enlargement, nonspecific generalized dermatitis, and chronic diarrhea ( p <.001). Oral candidiasis was more common in the group younger than 18 months (p <.001). In infants examined in the hospital for infective conditions, oropharyngeal candidiasis, ear discharge, dermatologic disorders, generalized lymphadenopathy, lobar consolidation, hepatosplenomegaly, and failure to thrive, especially marasmus, were important indicators of HIV infection.

T-helper cell responses to HIV envelope peptides in cord blood: protection against intrapartum and breast-feeding transmission

BACKGROUND

Acquired HIV-specific cell-mediated immune responses have been observed in exposed-uninfected individuals, and it has been inferred, but not demonstrated, that these responses constitute a part of natural protective immunity to HIV. This inference was tested prospectively in the natural exposure setting of maternal-infant HIV transmission in a predominantly breast-fed population.

METHODS

Cord blood from infants of HIV-seropositive women in Durban, South Africa, were tested for in vitro reactivity to a cocktail of HIV envelope peptides (Env) using a bioassay measuring interleukin-2 production in a murine cell line. Infants were followed with repeat HIV RNA tests up to 18 months of age to establish which ones acquired HIV-infection.

RESULTS

T-helper cell responses to Env were detected in 33 out of 86 (38%) cord blood samples from infants of HIV-seropositive women and in none of nine samples from seronegative women (P = 0.02). Among infants of HIV-seropositive mothers, three out of 33 with T-helper responses to Env were already infected before delivery (HIV RNA positive on the day of birth), two were lost to follow-up, and none of the others (out of 28) were found to be HIV infected on subsequent tests. In comparison, six out of 53 infants unresponsive to Env were infected before delivery, and eight out of 47 (17%) of the others were found to have acquired HIV infection intrapartum or post-partum through breast-feeding (P = 0.02).

CONCLUSIONS

T-helper cell responses to HIV envelope peptides were detected in more than one-third of newborns of HIV-infected women; no new infections were acquired by these infants at the time of delivery or post-natally through breast-feeding if these T-helper cell responses were detected in cord blood.

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.

A trial of shortened zidovudine regimens to prevent mother-to-child transmission of human immunodeficiency virus type 1. Perinatal HIV Prevention Trial (Thailand) Investigators

BACKGROUND

The optimal duration of zidovudine administration to prevent perinatal transmission of human immunodeficiency virus type 1 (HIV-1) should be determined to facilitate its use in areas where resources are limited.

METHODS

We conducted a randomized, double-blind equivalence trial of zidovudine starting in the mother at 28 weeks' gestation, with 6 weeks of treatment in the infant (the long-long regimen), which is similar to protocol 076; zidovudine starting at 35 weeks' gestation, with 3 days of treatment in the infant (the short-short regimen); a long-short regimen; and a short-long regimen. The mothers received zidovudine orally during labor. The infants were fed formula and were tested for HIV DNA at 1, 45, 120, and 180 days. After the first interim analysis, the short-short regimen was stopped.

RESULTS

A total of 1437 women were enrolled. At the first interim analysis, the rates of HIV transmission were 4.1 percent for the long-long regimen and 10.5 percent for the short-short regimen (P=0.004). For the entire study period, the transmission rates were 6.5 percent (95 percent confidence interval, 4.1 to 8.9 percent) for the long-long regimen, 4.7 percent (95 percent confidence interval, 2.4 to 7.0 percent) for the long-short regimen, and 8.6 percent (95 percent confidence interval, 5.6 to 11.6 percent) for the short-long regimen. The rate of in utero transmission was significantly higher with the two regimens with shorter maternal treatment (5.1 percent) than with the two with longer maternal treatment (1.6 percent).

CONCLUSIONS

The short-short zidovudine regimen is inferior to the long-long regimen and leads to a higher rate of perinatal HIV transmission. The long-short, short-long, and long-long regimens had equivalent efficacy. However, the higher rate of in utero transmission with the short-long regimen suggests that longer treatment of the infant cannot substitute for longer treatment of the mother.

Interventions to prevent vertical transmission of HIV-1: effect on viral detection rate in early infant samples

OBJECTIVE

To determine whether mode of delivery or the use of maternal or neonatal antiretroviral prophylaxis influence the age when HIV-1 can first be detected in infected infants, particularly the probability of detection at birth.

METHODS

In a collaboration between four multicentre studies, data on 422 HIV-1 infected infants who were assessed by HIV-1 DNA PCR or cell culture before 14 days of age were analysed. Weibull mixture models were used to estimate the cumulative proportion of infants with detectable levels of HIV-1 according to use of maternal/neonatal antiretroviral therapy (mainly zidovudine monotherapy) and mode of delivery.

RESULTS

HIV-1 was detected in 162 infants (38%) when they were first tested, at a median age of 2 days. At birth, it was estimated that 36% [95% confidence interval (CI), 31-41%] of infants have levels of virus that can be detected by DNA PCR or cell culture. This percentage was not associated with either mode of delivery (35% for vaginal delivery versus 40% for cesarean section delivery; P = 0.4) or the use of maternal or neonatal antiretroviral prophylaxis. Among infants with undetectable levels of HIV-1 at birth, the median time to viral detectability was estimated to be 14.8 days (95% CI, 12.9-16.8 days). This time was increased by 15% (95% CI, -11 to 48%; P = 0.3) among infants who were exposed to antiretroviral therapy postnatally compared with infants who were not exposed. No effect was observed for mode of delivery.

CONCLUSIONS

The outcome of an early virological test for HIV-1 is thought to be related directly to the timing of transmission and cesarean section delivery primarily reduces the risk of intrapartum transmission. The absence of an association between mode of delivery and viral detectability at birth was therefore unexpected. There was no evidence that foetal or neonatal exposure to prophylactic zidovudine delays substantially the diagnosis of infection, although this cannot be inferred for combination antiretroviral therapy.

Update on perinatal HIV transmission

Over the past decade, much progress has been made in understanding the risk factors and timing of perinatal HIV transmission. Even more impressive have been the successful clinical trials with antiretrovirals, such as ZDV, ZDV-3TC, and nevirapine, that demonstrated significant reductions in the risk for infant infection. Within the United States and Europe, these trial results have led to rapid implementation and dramatic decreases in new perinatal HIV cases since 1994. An immediate challenge is to rapidly translate the short-course antiretroviral trial results with ZDV and nevirapine into public health policy and practice in resource-poor settings, where almost 600,000 neonates continue to become infected by mother-infant HIV transmission each year. Physicians must also test strategies to further decrease the risk for infant HIV infection during the breast-feeding period.

Diagnosis of HIV infection in children

Many advances have been made in the area of HIV diagnostics. Commercially available virologic assays are sensitive and specific for the early detection of HIV in perinatal infection. The timing of the transmission of HIV from mother to child (in utero, at the time of birth, or postnatally by breast-feeding) is a critical consideration in the appropriate diagnosis of infants. Several algorithms can be used to define early infection and the potential timing of acquisition of infection that combine different assays and timing of specimens. The use of virologic assays, including HIV DNA PCR and HIV RNA detection methods and culture, can define and rule out infection in infants less than 18 months of age. Serologic diagnostic methods, including HIV ELISA, immunofluorescence, and western blot assays, can be used to diagnose infants more than 18 months of age, when transplacental antibody has disappeared in uninfected HIV-exposed infants. The challenge of the early and accurate diagnosis of perinatally HIV-exposed infants is the use of new assays to detect different HIV subtype infections that are prevalent in developing countries. Rapid, simple, and inexpensive serologic and virologic assays are being developed for worldwide use.

Timing of human immunodeficiency virus type 1 (HIV-1) transmission from mother to child: bayesian estimation using a mixture

The timing of mother-to-child HIV transmission is not directly observable but influences the infected child's viral and immune status in the neonatal period. A hierarchical model was developed in a Bayesian framework to 'back-calculate' the timing of HIV-1 transmission from mother to child from the virological and immunological kinetics in the infected infant. Joint evolution of viral markers and immune response was modelled as a continuous time Markov process. The modelling of the period from infection to birth was based on a mixture of three distributions taking into account the various mother-to-child transmission pathways: In utero (early or late in gestation) and intrapartum (during the delivery process), integrating the fact that transmission is a continuum during the pregnancy. Gibbs sampling was used to estimate the marginal posterior distributions of the transition intensities between stages of HIV infection and those of the individual times from infection to birth. We applied our model to data on 135 perinatally HIV-1-infected children included in the French Prospective Study on Pediatric HIV infection. The model suggested that transmission occurred late in utero during the last month of pregnancy and that the day of delivery was a particularly critical time in HIV-1 transmission from mother to child. The paper ends with a discussion of model assumptions and a comparison with results obtained using a non-parametric method.

Selection of appropriate HIV-1 genomic regions for single-strand conformation polymorphism analysis of the diversity, modification, and transmission of HIV-1 quasispecies

Single-strand conformation polymorphism (SSCP) analysis is a useful tool for studying viral quasispecies. Four regions within the HIV-1 genome were studied by means of SSCP analysis with the aim of determining which regions were the most informative for the study of HIV-1 transmission or for detection of changes in HIV-1 quasispecies populations. Nested polymerase chain reaction (PCR) was used to amplify V1, V2, V3 of the env gene, and the p2 region in the gag gene. In total, 114 plasma specimens from 79 individuals were tested, including serial specimens from 10 mother-infant pairs that were provided by the Women and Infants Transmission Study (WITS). HIV-1 in specimens that were PCR-positive with primer pair SK38/SK39 showed different percentages of positive signals with primer pairs for the four regions: V1, 63%; V2, 83%; V3, 88%, and p2, 100%. HIV-1 sequences in the p2 target region displayed the greatest degree of polymorphism. Analysis of serial specimens showed that the V1 target region was the most variable of the four regions studied and was the most appropriate region for monitoring changes in quasispecies populations. Of the four regions studied, p2 was the most informative for the study of HIV transmission, as shown by analysis of samples from documented cases of mother to infant HIV-1 transmission.

Perinatal human immunodeficiency virus-1 transmission and intrauterine growth: a cohort study in Butare, Rwanda

OBJECTIVE

To study the association of perinatal human immunodeficiency virus (HIV)-1 transmission with birth outcomes, including birth weight, gestational age, ponderal index, head circumference, and weight/head ratio.

METHODS

Data from a prospective cohort study of 627 pregnant women and their infants in Butare, Rwanda, from October 1989 until April 1994 were analyzed. A total of 318 HIV-1-infected and 309 seronegative women were enrolled during pregnancy and gave birth to 590 live singletons. Multiple linear regression modeling was used to assess the association of mother-child HIV status with several birth outcome measures.

RESULTS

Unadjusted mean birth weight of HIV- infected infants was 235 g (95% confidence interval [CI] = 94 to 376 g) less than that of HIV-uninfected infants born to HIV-positive mothers (the reference group). After adjustment for gestational age, socioeconomic factors, maternal age, parity, hematocrit, and anthropomorphic measures, mean birth weight of HIV-infected infants was 154 g (95% CI = 38 to 271 g) lower than that of the reference group. When infants born to HIV-seronegative mothers were compared with the reference group, mean birth weights did not differ. Adjusted models resulted in estimates of mean head circumference 0.6 cm smaller (95% CI = 0.2 to 1.1 cm), ponderal index 0.14 lower (95% CI = 0.05 to 0.23), weight/head ratio 3.5 lower (95% CI = 0.5 to 6.4), and gestational age 0.5 weeks shorter (95% CI = 0.1 to 0.9 weeks) for HIV-infected infants than for the reference group.

CONCLUSIONS

After adjustment for potential confounding variables, this study showed statistically significant differences in birth weight, gestational age, ponderal index, and weight/head ratio when HIV-infected infants were compared with noninfected infants born to HIV-positive mothers. HIV-1, mother-to-child transmission, Africa, intrauterine growth, birth weight, gestational age, ponderal index.

Prevention of mother-to-child transmission of HIV-1 infection: alternative strategies and their cost-effectiveness

OBJECTIVE

To estimate the cost-effectiveness of alternative interventions to reduce the risk of mother-to-child transmission of HIV.

DESIGN

A model capturing the sequential nature of mother-to-child transmission in utero, at delivery and postnatally was used to determine how the effects of bottle-feeding, elective Cesarean section (CS) and zidovudine (ZDV) would combine to prevent mother-to-child HIV transmission. Parameter estimates were derived from the literature, UK health service costs applied, and incremental cost effectiveness ratios (ICER) estimated for alternative risk reduction strategies. Results can be transposed to other cost assumptions or currencies.

RESULTS

In a woman who breast-feeds her baby, has a vaginal or emergency CS delivery and takes no ZDV, the estimated transmission risk is 31.6% (range, 23.7-38.1%), at a cost of 400 UK pound per woman; this falls to a risk of 3.7% (range, 1.7-6.9%) when bottle-feeding, ZDV therapy and elective CS are all implemented at a cost of 1968 UK pound per woman. From a public health perspective the ICER of ZDV and elective CS each depend on the acceptance rates of the other. In women counselled against breast-feeding, ZDV with 100% acceptance of elective CS has an ICER of 11 342 UK pound (95% confidence interval (CI), 7084-21 515 UK pound]. However, the ICER of CS ranges from 9248 UK pound (95% CI, 5072-46 913 pound sterling) at zero ZDV acceptance to 27 895 UK pound (95% CI, 10 018-154 462 pound sterling) at 100% ZDV acceptance.

CONCLUSIONS

Considering the estimated cost of caring for an infected child, ZDV appears to be cost-effective under any of the circumstances examined. However, elective CS may not be cost-effective in populations where the uptake of ZDV is high, and a more precise estimate of its efficacy is required.

Effectiveness of postinoculation (R)-9-(2-phosphonylmethoxypropyl) adenine treatment for prevention of persistent simian immunodeficiency virus SIVmne infection depends critically on timing of initiation and duration of treatment

(R)-9-(2-Phosphonylmethoxypropyl)adenine (PMPA), an acyclic nucleoside phosphonate analog, is one of a new class of potent antiretroviral agents. Previously, we showed that PMPA treatment for 28 days prevented establishment of persistent simian immunodeficiency virus (SIV) infection in macaques even when therapy was initiated 24 h after intravenous virus inoculation. In the present study, we tested regimens involving different intervals between intravenous inoculation with SIV and initiation of PMPA treatment, as well as different durations of treatment, for the ability to prevent establishment of persistent infection. Twenty-four cynomolgus macaques (Macaca fascicularis) were studied for 46 weeks after inoculation with SIV. All mock-treated control macaques showed evidence of productive infection within 2 weeks postinoculation (p.i.). All macaques that were treated with PMPA for 28 days beginning 24 h p.i. showed no evidence of viral replication following discontinuation of PMPA treatment. However, extending the time to initiation of treatment from 24 to 48 or 72 h p.i. or decreasing the duration of treatment reduced effectiveness in preventing establishment of persistent infection. Only half of the macaques treated for 10 days, and none of those treated for 3 days, were completely protected when treatment was initiated at 24 h. Despite the reduced efficacy of delayed and shortened treatment, all PMPA-treated macaques that were not protected showed delays in the onset of cell-associated and plasma viremia and antibody responses compared with mock controls. These results clearly show that both the time between virus exposure and initiation of PMPA treatment as well as the duration of treatment are crucial factors for prevention of acute SIV infection in the macaque model.

HIV in pregnancy

Pregnancy in individuals infected with HIV has become an important problem because of a fourfold rise of infection in women of childbearing age in the developed world. The incidence of vertical transmission varies in different continents and is highest in Africa. Transmission may occur in utero (antepartum), during delivery (intrapartum), or after birth (postpartum), occurring during the latter period, in many cases, through breastfeeding. Maternal viral burden around the time of delivery is the strongest determinant of the risk of disease transmission. While breastfeeding may account for up to one-third of cases of vertical transmission in Africa, the benefits of breastfeeding outweigh its risks, even in HIV infection, and breastfeeding is recommended in those areas. Treatment of the mother with antiretroviral agents significantly decreases the risk of vertical transmission.

Perinatal transmission of HIV and diagnosis of HIV infection in infants: a review

Paediatric HIV infection has become a major burden on families, communities and health services worldwide. The vast majority of children now acquire HIV as a result of mother to infant (vertical) transmission. Recent major advances have occurred following the greater understanding of the risk factors for perinatal transmission and the role of antiretroviral therapy in preventing transmission. Now that interruption of vertical transmission is possible, early identification of HIV-infected pregnant women is critical. As of June 1997, HIV infection has been diagnosed in 37 children under 15 yrs of age in the Republic of Ireland; 32 as a result of maternal to infant transmission. The exact timing of HIV transmission during pregnancy is unclear but it is estimated that 60-70 per cent of infants may be infected at the time of delivery with approximately 30 per cent infected earlier in gestation. Vertical transmission rates vary from 15-40 per cent in different global areas. Antenatal and perinatal zidovudine treatment can reduce this rate by 60-70 per cent. Risk factors for the vertical transmission of HIV-1 are multifactorial. These factors include maternal disease status, in particular maternal viral load, route of delivery, duration of membrane rupture, presence of obstetric complications and infant feeding practices. Definitive diagnosis of HIV infection in infancy has been difficult in the past. Direct viral detection methods now allow the reliable diagnosis of HIV infection in the first few months of life. The most effective intervention to reduce perinatal HIV infection will be the better identification of HIV positive pregnant women with the subsequent introduction of measures to interrupt vertical transmission of HIV.

Elevated CD8+DR+ lymphocytes in HIV-exposed infants with early positive HIV cultures: a possible early marker of intrauterine transmission. Women and Infants Transmission Study Group

The associations among timing of maternal-fetal human immunodeficiency virus (HIV) transmission, infant age at first positive HIV culture, and CD8+ lymphocyte activation were examined for 74 perinatally infected infants. Nineteen of the infected infants had positive HIV cultures at < or =7 days of life, and 55 had negative HIV cultures at < or =7 days but were positive later. Of the infants with early positive HIV-1 cultures, 15 of the 17 tested with DNA polymerase chain reaction methods had concordant results. The percentage of CD8+ and HLA-DR+ lymphocytes (CD8+DR+%) during the first week of life was significantly higher in infants with early compared with late positive cultures (median CD8+DR+% of 5.0% versus 2.0%, p = 0.0006). The CD8+DR+% was similar between uninfected infants and infants with late positive cultures during the first week of life (median 2%) but increased in infants with late positive cultures to 6% by 1 month. The CD4+% during the first 6 months of life was not different between infants with early or with late positive cultures, but infants with the highest CD8+DR+% at < or =7 days of life had significantly lower CD4+% at < or =7 days and at 1, 2, and 4 months of age. These data show that early CD8+ lymphocyte activation is associated with early positive HIV cultures and lower CD4+ percentages during early infancy and are consistent with the hypothesis that early positive cultures positivity may indicate in utero HIV infection.