Effects of zidovudine use during pregnancy on resistance and vertical transmission of human immunodeficiency virus type 1

Resistance to reverse transcriptase inhibitors used in the treatment and prevention of HIV-1 infection

Inhibitors that target the retroviral enzyme reverse transcriptase (RT) have played an indispensable role in the treatment and prevention of HIV-1 infection. They can be grouped into two distinct therapeutic groups, namely the nucleoside and nucleotide RT inhibitors (NRTIs), and the non-nucleoside RT inhibitors (NNRTIs). NRTIs form the backbones of most first- and second-line antiretroviral therapy (ART) regimens formulated for the treatment of HIV-1 infection. They are also used to prevent mother-to-child transmission, and as pre-exposure prophylaxis in individuals at risk of HIV-1 infection. The NNRTIs nevirapine (NVP), efavirenz and rilpivirine also used to form part of first-line ART regimens, although this is no longer recommended, while etravirine can be used in salvage ART regimens. A single-dose of NVP administered to both mother and child has routinely been used in resource-limited settings to reduce the rate of HIV-1 transmission. Unfortunately, the development of HIV-1 resistance to RT inhibitors can compromise the efficacy of these antiviral drugs in both the treatment and prevention arenas. Here, we provide an up-to-date review on drug-resistance mutations in HIV-1 RT, and discuss their cross-resistance profiles, molecular mechanisms and clinical significance.

HIV drug resistance and mother-to-child transmission of HIV

This article covers HIV drug resistance among pregnant women and the implications of transmission of resistant HIV to the infant. Resistance to antiretroviral drugs may be acquired or can emerge while HIV-infected pregnant women are on antiretroviral therapy, either before or during pregnancy. Resistance to antiretroviral drugs among HIV-infected infants may be acquired from the mother in utero or during the intrapartum period. Resistance may also emerge from exposure to antiretroviral drugs given to the infant for prophylaxis against HIV transmission. In settings where breastfeeding is practiced, ongoing transmission of HIV from breastfeeding may lead to transmission of resistant HIV from the mother. If the mother is taking antiretroviral drugs while breastfeeding, resistance to antiretroviral drugs may emerge in an HIV-infected infant from ingestion of antiretroviral drugs via breast milk. The magnitude and implications of antiretroviral resistance among HIV-infected pregnant women and HIV-infected infants are summarized.

THE VERTICAL TRANSMISSION OF HUMAN IMMUNODEFICIENCY VIRUS TYPE 1: Molecular and Biological Properties of the Virus

The vertical (mother-to-infant) transmission of human immunodeficiency virus type 1 (HIV-1 ) occurs at an estimated rate of more than 30% and is the major cause of AIDS in children. Numerous maternal parameters, including advanced dinical stages, low CD4+ lymphocte counts, high viral load, immune response, and disease progression have been implicated in an increased risk of vertical transmission. While the use of antiretroviral therapy (ART) during pregnancy has been shown to reduce the risk of vertical transmission, selective transmission of ART-resistant mutants has also been documented. Elucidation of the molecular mechanisms of vertical transmission might provide relevant information for the development of effective strategies for prevention and treatment. By using HIV-1 infected mother-infant pairs as a transmitter-recipient model, the minor genotypes of HIV-1 with macrophage-tropic and non-syncytium-inducing phenotypes (R5 viruses) in infected mothers were found to be transmitted to their infants and were initially maintained in the infants with the same properties. In addition, the transmission of major and multiple genotypes has been suggested. Furthermore, HIV-1 sequences found in non-transmitting mothers (mothers who failed to transmit HIV-1 to their infants in the absence of ART) were less heterogeneous than those from transmitting mothers, suggesting that viral heterogeneity may play an important role in vertical transmission. In the analysis of other regions of the HIV-1 genome, we have shown a high conservation of intact and functional gag p17, vif, vpr, vpu, tat, and nef open reading frames following mother-to-infant transmission. Moreover the accessory genes, vif and vpr, were less functionally conserved in the isolates of non-transmitting mothers than transmitting mothers and their infants. We, therefore, should target the properties of transmitted viruses to develop new and more effective strategies for the prevention and treatment of HIV-1 infection.

Awareness and attitudes about HIV among pregnant women in Aksu, northwest China

The Xinjiang Uyghur Autonomous Region has a firmly established HIV epidemic among its intravenous drug user (IDU) population. Local sex workers were also found to be positive in 1998. A descriptive, cross-sectional survey of knowledge about HIV/AIDS and attitudes among consecutively selected pregnant women was conducted November 2005 in Aksu Prefecture, north-western China, with a population on 2 million with about 25 000 pregnancies per year. A total of 291 pregnant women participated. We found a limited knowledge on mother-to child transmission with several misconceptions. The AIDS campaigns have been successful in making all the women aware of HIV as a sexually transmitted disease. However, the common belief that social contact causes transmission gives a high risk that patients are stigmatized. Obviously, it is important to design HIV information strategies that target pregnant women in north-western China.

Time Trends for HIV-1 Antiretroviral Resistance Among Antiretroviral-Experienced and Naive Pregnant Women in New York City During 1991 to Early 2001

Time trends in the prevalence of drug resistance to antiretroviral therapy (ART) in pregnant women have not been studied. Treatment and prophylactic efficacy could be compromised by drug-resistant HIV strains. We conducted a repeated cross-sectional study of antiretroviral resistance mutations to nucleoside reverse transcriptase inhibitors (NRTIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs) and of major mutations to protease inhibitors (PIs) in virus isolates from 300 HIV-infected pregnant women in New York City from 1991 to early 2001. The overall prevalence of mutations for NRTIs from 1991 to early 2001 was higher for ART-experienced (25.6% [95% confidence interval (CI): 19.1% to 32.1%]) than ART-naive (8.6% [95% CI: 3.7% to 13.4%]) mothers (P < 0.002). For NNRTIs, the overall prevalence of mutations was somewhat higher among ART-experienced (5.8% [95% CI: 2.3% to 9.3%]) versus ART-naive (1.6% [95% CI: 0% to 3.7%]) women (P = 0.06), and increased over time for ART-naive women (0%-7.4%; P = 0.03) and ART-experienced women (0%-19.4%; P = 0.0002). The prevalence of PI-associated mutations was also higher overall among ART-experienced mothers (5.8% [95% CI: 2.3% to 9.3%] vs. 1.6% [95% CI: 0% to 3.7%]; P = 0.06), with increases over time seen for ART-naive women (0%-7.4%; P = 0.03) and ART-experienced women (0%-16.1%; P = 0.0008). The increasing prevalence of drug resistance in pregnant women, including those who are drug-naive, underscores the necessity for resistance testing to guide treatment to achieve suppression of the mother's virus.

Frequency of protease and reverse transcriptase drug resistance mutations in naïve HIV-infected patients

BACKGROUND

Infections with drug-resistant HIV viruses in naïve subjects may cause antiretroviral (ARV) treatment failure. The prevalence of ARV resistance mutations in HIV-1 transcripts of infected naïve patients from northeast Mexico was determined in this study.

METHODS

RNA was extracted from plasma samples of 42 naïve individuals who were diagnosed between February 2001 and September 2003 as HIV-1 infected. Both protease (Pr) and reverse transcriptase (RT) were sequenced in 30 patients. In six samples only the RT segment was sequenced and in three samples only the protease segment was analyzed.

RESULTS

One of 36 isolates (2.8%) had the M184V resistance mutation to nucleoside retrotranscriptase inhibitors. In the Pr segment, only minor mutations were detected in 27/33 isolates (81.8%).

CONCLUSIONS

In this first study, prevalence of major mutations associated with ARV resistance in naïve patients in northeast Mexico is low compared to other countries, perhaps due to a low level of exposure of this population to ARV drugs.

Characterization of HIV-1 envelope gp41 genetic diversity and functional domains following perinatal transmission

Background

HIV-1 envelope gp41 is a transmembrane protein that promotes fusion of the virus with the plasma membrane of the host cells required for virus entry. In addition, gp41 is an important target for the immune response and development of antiviral and vaccine strategies, especially when targeting the highly variable envelope gp120 has not met with resounding success. Mutations in gp41 may affect HIV-1 entry, replication, pathogenesis, and transmission. We, therefore, characterized the molecular properties of gp41, including genetic diversity, functional motifs, and evolutionary dynamics from five mother-infant pairs following perinatal transmission.

Results

The gp41 open reading frame (ORF) was maintained with a frequency of 84.17% in five mother-infant pairs' sequences following perinatal transmission. There was a low degree of viral heterogeneity and estimates of genetic diversity in gp41 sequences. Both mother and infant gp41 sequences were under positive selection pressure, as determined by ratios of non-synonymous to synonymous substitutions. Phylogenetic analysis of 157 mother-infant gp41 sequences revealed distinct clusters for each mother-infant pair, suggesting that the epidemiologically linked mother-infant pairs were evolutionarily closer to each other as compared with epidemiologically unlinked sequences. The functional domains of gp41, including fusion peptide, heptad repeats, glycosylation sites and lentiviral lytic peptides were mostly conserved in gp41 sequences analyzed in this study. The CTL recognition epitopes and motifs recognized by fusion inhibitors were also conserved in the five mother-infant pairs.

Conclusion

The maintenance of an intact envelope gp41 ORF with conserved functional domains and a low degree of genetic variability as well as positive selection pressure for adaptive evolution following perinatal transmission is consistent with an indispensable role of envelope gp41 in HIV-1 replication and pathogenesis.

Risk behaviors of youth living with HIV: pre- and post-HAART

OBJECTIVE

To examine the transmission behavior among youth living with HIV (YLH), pre- and post-HAART.

METHODS

Two cohorts were recruited: (1) 349 YLH during 1994 to 1996 and (2) 175 YLH during 1999 to 2000, after the wide availability of HAART. Differences in sexual and substance-use risk acts and quality of life were examined.

RESULTS

Post-HAART YLH were more likely to engage in unprotected sex and substance use, to be more emotionally distressed, and to have lower quality of life than were pre-HAART YLH.

CONCLUSIONS

Targeted interventions for YLH that address reductions in transmission acts and aim to improve quality of life are still needed.

Study of Antiretroviral Drug???Resistant HIV-1 Genotypes in Northern Thailand: Role of Mutagenically Separated Polymerase Chain Reaction as a Tool for Monitoring Zidovudine-Resistant HIV-1 in Resource-Limited Settings

As the number of HIV-1-infected individuals receiving antiretroviral drugs has been rapidly increasing in developing countries, there is an urgent need for drug resistance genotype information of non-B subtype HIV-1 and for the establishment of a practical system of monitoring drug-resistant viruses. This study first sequenced the reverse transcriptase region of HIV-1 in 112 infected individuals who had been treated with zidovudine (AZT)/didanosine or AZT/zalcitabine as dual therapy at a government hospital in northern Thailand and then compared the above sequence method with mutagenically separated polymerase chain reaction (MS-PCR) for detecting M41L and K70R mutations. Concordant rates of detecting M41L and K70R mutations by the 2 methods were 96.9% (93/96) and 92.7% (89/96), respectively. The M41L and K70R MS-PCR could detect 86.4% of AZT-resistant strains with any resistance mutation, which was determined by the sequencing method. Then 292 drug-naive individuals were screened for the presence of drug-resistant HIV-1 by the MS-PCR assay and it was found that 2 individuals (0.7%) carried viruses with either the M41L or K70R mutation. It is feasible to test a large number of samples with MS-PCR, which is sensitive, cheap, and easy to perform and does not require sophisticated equipment. The M41L and K70R MS-PCR is potentially a useful tool to monitor the spread of AZT-resistant HIV-1 in resource-limited countries.

Understanding HIV-1 drug resistance

Infection with drug-resistant HIV-1 may result from the acquisition of mutant strains or from their selection within the individual; either can compromise the efficacy of antiretroviral therapy (ART). Drug-resistance testing is recommended to assist in the choice of ART. Herein, factors that contribute to the selection of drug-resistant virus and details important to the interpretation of the genotypic and phenotypic susceptibility test results are reviewed.

Zidovudine Resistance Phenotype and Risk of Perinatal HIV-1 Transmission in Zidovudine Monotherapy???Treated Mothers With Moderately Advanced Disease

The association of phenotypic zidovudine resistance with perinatal transmission was evaluated in 74 zidovudine-treated mothers enrolled in the Women and Infants Transmission Study through September 1994. Women in the sample had moderately advanced disease, with a median CD4+ cell count of 271/microL and a median plasma HIV-1 RNA level of 39,811 copies/mL. Factors independently associated with zidovudine resistance at delivery (50% inhibitory concentration [IC50], >/=0.1 microM) in multiple logistic regression included prepregnancy zidovudine use, high log plasma HIV-1 RNA level, and low CD4+ cell count. Of 74 mothers, 16 (22%) transmitted HIV-1 to their infants. After adjustment for duration of membrane rupture and CD8+ cell count, zidovudine resistance (IC50 range, 0.01-2.2 microM) was associated with an increased odds of transmission (ORadj, 1.25 per 0.1 microM; 95% confidence interval, 1.01-1.54), suggesting a decreased effect of prenatal zidovudine on preventing transmission in mothers infected with zidovudine-resistant virus. However, when the analysis was limited only to those mothers infected with virus containing zidovudine resistance mutations, no association between phenotypic resistance and transmission remained, indicating that phenotype may not provide significant additional information in predicting transmission where resistance genotype is known.

Reduction in perinatal transmission and mortality from human immunodeficiency virus after intervention with zidovudine in Barbados

OBJECTIVES

To evaluate the impact of zidovudine (ZDV) intervention on vertical transmission and HIV-related mortality in two groups of pregnant mothers and their respective infants.

METHODS

A modified long course Paediatric AIDS Clinical Trial Group 076 protocol was used. None of the infants was breast-fed. Maternal CD4 T lymphocyte counts and viral loads were not monitored. Infants were followed for clinical progress, and serial serologic testing was performed to the age of 24 months, or until two successive HIV (enzyme-linked immunosorbent assay) tests were negative. In a historically case-controlled prospective study, the transmission rate in ZDV-untreated mother-infant pairs in which infants were born during 1991 through 1995 was compared with the transmission rate in ZDV-treated mother-infant pairs in which infants were born between 1996 and 2000.

RESULTS

In the 151 HIV-seropositive pregnant women and their 153 infants studied (2 pairs of twins), 93 mother-infant pairs were treated, and 59 were untreated (control group). Vertical transmission occurred in 5.5% [95% confidence interval (95% CI) 1.9 to 12.5] of the treated group of infants and in 27.1% (95% CI 16.7 to 40.5) of the untreated group. There was a 79.7% (95% CI 59.8 to 92.1%) relative reduction risk of transmission, which was statistically significant (z =3.18, two tailed P= 0.0001). Three infant deaths (3.7%) were recorded in the untreated group, and 1(1%) death was recorded in the treated group. In ZDV-untreated infants, deaths occurred at age <1 year, resulting from respiratory complications. One ZDV-treated infant died at 4 years of age with Pneumocystis carinii pneumonia.

CONCLUSIONS

Our study demonstrated a statistically significant reduction in the vertical transmission of HIV after intervention with ZDV therapy.

Assisted reproductive technology for men and women infected with human immunodeficiency virus type 1

In 2001, the World Health Organization reported 4.3 million new human immunodeficiency virus (HIV) infections in adults globally, 41% of which were in women. During the year 2000, 27% of newly diagnosed HIV infections in the United States occurred in women. In developed countries, the perception of HIV infection has changed from an acute, lethal infection to a chronic illness; the introduction of highly active antiretroviral therapy has decreased morbidity and mortality, and new drug therapies have dramatically decreased perinatal transmission. In view of these advances, some HIV-infected individuals are considering reproduction. Following the lead of organizations in other developed countries, the American College of Obstetricians and Gynecologists has recently endorsed the use of reproductive technology in HIV-infected patients. Which patients should be offered assisted reproduction and what the optimal methods are of decreasing heterosexual and perinatal HIV transmission must be determined.

Antiretroviral prophylaxis of perinatal HIV-1 transmission and the potential impact of antiretroviral resistance

Since 1994, trials of zidovudine, zidovudine and lamivudine, and nevirapine have demonstrated that these antiretroviral drugs can substantially reduce the risk of perinatal HIV-1 transmission. With reductions in drug price, identification of simple, effective antiretroviral regimens to prevent perinatal HIV-1 transmission, and an increasing international commitment to support health care infrastructure, antiretrovirals for both perinatal HIV-1 prevention and HIV-1 treatment will likely become more widely available to HIV-1-infected persons in resource-limited countries. In the United States, widespread antiretroviral usage has been associated with increased antiretroviral drug resistance. This raises concern that drug resistance may reduce the effectiveness of perinatal antiretroviral prophylaxis as well as therapeutic intervention strategies. The purpose of this article is to review what is known about resistance and risk of perinatal HIV transmission, assess the interaction between antiretroviral resistance and the prevention of perinatal HIV-1 transmission, and discuss implications for current global prevention and treatment strategies.

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.

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.

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

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

Performance of the applied biosystems ViroSeq human immunodeficiency virus type 1 (HIV-1) genotyping system for sequence-based analysis of HIV-1 in pediatric plasma samples

The ViroSeq HIV-1 Genotyping System is a commercially available, integrated sequence-based system for analysis of human immunodeficiency virus type 1 (HIV-1) drug resistance. We evaluated the performance of this system by analyzing HIV-1 in pediatric plasma samples. Plasma samples from children 4 months to 17 years of age were obtained from a clinical trial protocol (PACTG 377). Children in PACTG 377 were randomized to four treatment arms, including different combinations of antiretroviral drugs. HIV-1 genotyping was performed using samples collected prior to antiretroviral therapy (baseline) and at the time of virologic failure. Performance of the genotyping system was compared in three university laboratories. A total of 196 samples were analyzed, including 135 baseline and 61 failure samples. Plasma volumes ranged from 0.05 to 0.5 ml, and viral loads ranged from 1,084 to 3,484,991 copies/ml. PCR products suitable for sequencing were obtained for 192 of the 196 samples. Complete sequences for protease and reverse transcriptase were obtained for all of these 192 samples. For 180 samples, data were obtained from both DNA strands for the entire region analyzed. There was no evidence of sample cross-contamination based on phylogenetic analysis of HIV-1 sequences. Performance of the genotyping system was similar in three laboratories. This genotyping system performs well for analysis of HIV-1 in pediatric plasma samples, including those with low volume and low viral load. The availability of this system should facilitate studies of HIV-1 drug resistance.

Primary genotypic and phenotypic HIV-1 drug resistance in recent seroconverters in Madrid

OBJECTIVE

Transmission of drug-resistant HIV-1 strains is increasing with widespread use of antiretroviral drugs in developed countries. This study examined the prevalence of resistant viruses in recent seroconverters in Madrid, Spain.

DESIGN

HIV isolates from 30 consecutive participants with positive or indeterminate HIV antibody test results and a negative test result at a mean of 6.6 months earlier were examined for HIV drug resistance. All study subjects admitted to having very recently engaged in high-risk practices. All were therapeutically naive and were recruited between 1997 and 1999 in a referring health care facility for sexually transmitted diseases.

METHODS

Population-based sequencing of the viral reverse transcriptase (RT) and protease (PR) regions derived from plasma viral RNA was performed. Phenotypic resistance was assessed by a recombinant virus assay.

RESULTS

Overall prevalence of genotypes associated with reduced susceptibility was 26.7% (8 of 30 participants). Resistance mutations were seen against nucleoside analogues in 7 (23.3%), nonnucleoside reverse transcriptase inhibitors in 1 (3.3%), and protease inhibitors in 2 (6.7%). Zidovudine-resistance mutations M41L and/or T215Y were the commonest, found in 20% (6 of 30 participants). Resistance mutations to at least two antiretroviral families (multidrug-resistance) were detected in 2 (6.7%) study subjects. A median infectious dose (IC50) increase of fourfold for any drug was found in 7 patients, and in 2 was > tenfold for zidovudine (genotype M41L + T215Y) and lamivudine (genotype M184V), respectively.

CONCLUSIONS

Drug-resistant HIV variants were present in over one quarter of individuals recently diagnosed as infected in Madrid, Spain. Therefore, resistance testing at baseline should be considered for the optimal design of first-line antiretroviral combinations.

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.

Clinical monitoring of HIV-1 infection in the ERA of antiretroviral resistance testing

Viral replication of HIV-1 in the human body is a dynamic process. Incomplete suppression of replication during antiretroviral therapy ultimately selects for resistance that imparts an adaptive advantage to HIV-1. Therefore, the goal of antiretroviral therapy is complete suppression of viral replication. Viral suppression to below the lowest possible limits of detection has been associated with an optimal clinical response and delay of drug resistance. An ultrasensitive viral load assay with a very low threshold of detection remains our best laboratory tool to monitor the response to therapy. Patients may fail HAART for many reasons. Only when other potential causes of treatment failure are excluded should antiretroviral resistance testing be considered. Genotypic and phenotypic assays for assessing resistance are now available, and recent retrospective and prospective data support their use in clinical management as an adjunct to helping to choose among different antiretroviral drugs. Despite the growing enthusiasm for these tests, improvements in sensitivity, turnaround time, and quality control are still needed. A practitioner's decision about when to initiate or change therapy in an HIV-infected patient should depend primarily on viral load results, and not on antiretroviral resistance test results. Moreover, resistance testing is no substitute for a thorough clinical and drug history. As we approach the third decade of the HIV epidemic, we will learn how to use antiretroviral resistance tests in conjunction with (not in lieu of) proven clinical and laboratory tools.

The role of antiretrovirals and drug resistance in vertical transmission of HIV-1 infection

Large-cohort studies in North America, Europe, and Thailand have shown that zidovudine/azidothymidine (AZT) monotherapy, given at the late stages of pregnancy, is of proven benefit in reducing mother-to-infant HIV transmission by 51% to 68%. AZT monotherapy will not be of long-term benefit for mothers because no single drug can counteract viral infection; benefits to babies will be short-lived if HIV-1 is acquired through breastfeeding after birth. Unfortunately, ongoing mutation of HIV under conditions of drug pressure allows for the evolution and selection of AZT-resistant viruses. Emergence of AZT-resistant variants in pregnant mothers (7-29%) and their infected offspring (5-21%) has been described in several studies. Drug resistance arises more frequently in those mothers who received AZT therapy before pregnancy. Recent advances in combination chemotherapy may provide alternative strategies in prevention of vertical transmission and drug resistance. Genotypic screening of the HIV-1 isolated from pregnant mothers may provide rational modifications in antiretroviral (ARV) strategies to circumvent vertical HIV transmission. This may be of advantage for resource-rich nations but not for underdeveloped nations with limited access to ARVs. Public health programs are vital to have an impact on the tragic pandemic of pediatric AIDS.

Cost effectiveness of human immunodeficiency virus postexposure prophylaxis for healthcare workers

OBJECTIVE

The United States Public Health Service (USPHS) published recommendations for human immunodeficiency virus (HIV) postexposure prophylaxis (PEP) of healthcare workers in May 1998. The aim of this study was to analyse the cost effectiveness of the USPHS PEP guidelines.

DESIGN AND SETTING

This was a modelling study in the setting of the US healthcare system in 1989. The analysis was performed from the societal perspective; however, only HIV healthcare costs were considered and health-related losses of productivity were not included.

METHODS

A decision tree incorporating a Markov model was created for 4 PEP strategies: the current USPHS recommendations, triple drug therapy, zidovudine monotherapy or no prophylaxis. A probabilistic sensitivity analysis using a Monte Carlo simulation was performed. Confidence intervals (CIs) around cost-effectiveness estimates were estimated by a bootstrapping method.

RESULTS

The costs (in 1997 US dollars) per quality-adjusted life-year (QALY) save by each strategy were as follows: monotherapy $US688 (95% CI: $US624 to $US750); USPHS recommendations $US5211 (95% CI: $US5126 to $US5293); and triple drug therapy $US8827 (95% CI: $US8715 to $US8940). The marginal cost per year of life saved was: USPHS recommendations $US81 987 (95% CI: $US80 437 to $US83 689); triple drug therapy $US970 451 (95% CI: $US924 786 to $US 1 014 429). Sensitivity testing showed that estimates of the probability of seroconversion for each category of exposure were most influential, but did not change the order of strategies in the baseline analysis. With the prolonged HIV stage durations and increased costs associated with recent innovations in HIV therapy, the marginal cost effectiveness of the USPHS PEP strategy was decreased to $US62 497/QALY saved. All 3 intervention strategies were cost effective compared with no postexposure prophylaxis.

CONCLUSIONS

Current USPHS PEP recommendations are marginally cost effective compared with monotherapy, but the additional efficacy of triple drug therapy for all risk categories is rewarded by only a small reduction in HIV infections at great expense. For the foreseeable future, assuming innovations in therapy that employ expensive drug combinations earlier in the HIV disease course to extend life expectancy and the increasing prevalence of HIV drug resistance, our model supports the use of the USPHS PEP guidelines.

Management of HIV infection during pregnancy

Optimal management of HIV infection in pregnancy requires maternal use of potent antiretroviral therapy to prevent disease progression in the mother and vertical transmission to the newborn. Combination antiretroviral therapy substantially reduces the risk of perinatal HIV transmission and appears to be more effective than zidovudine monotherapy. The administration of single dose nevirapine to mother intrapartum and infant postpartum effectively reduces vertical HIV transmission and is less costly and cumbersome than zidovudine regimens. Elective cesarean section reduces vertical transmission of HIV but its benefit is less clear when antiretroviral therapy decreases maternal plasma HIV viral load to low levels at delivery. If possible, HIV-infected mothers should avoid breastfeeding. The present review discusses the importance of early identification of maternal HIV infection, strict adherence to combination antiretroviral regimens to prevent drug resistance, developing a better understanding of antiretroviral pharmacokinetics in pregnancy and short/long term safety of anti-HIV drugs.

Liquid chromatographic determination of urinary 6beta-hydroxycortisol to assess cytochrome p-450 3A activity in HIV positive pregnant women

Assessing the activity of CYP3A4 is important for predicting the pharmacokinetic behavior of protease inhibitors in HIV positive patients, especially in pregnant women. The endogenous hormonal ratio of 6beta-hydroxycortisol (beta-OHF) to cortisol (F) in the urine is an index for metabolic enzyme activity of cytochrome p-450 (CYP) 3A4. Because the ratio is a unique way to assess the enzyme activity without using any exogenous probes for this isozyme, it is practical for use in pregnant women. In this paper, we describe a method using high performance liquid chromatography (HPLC) for 6beta-OHF in urine from pregnant women to estimate the ratio of 6beta-OHF/F. Urinary 6beta-OHF was measured by using C18-cartridge solid phase extraction and isocratic HPLC. Aliquots (1 ml) of urine samples spiked with internal standard, 6beta-hydroxyprednisolone (6beta-OHPSL), were alkalinized with NaOH, then applied to C18-cartridges, which were washed with water and hexane and eluted with ethyl acetate. After the effluents were dried and reconstituted in 10% acetonitrile, the samples were analyzed by HPLC using an isocratic mobile phase (acetic acid/acetonitrile/50 mM potassium dihydrogenphosphate: 0.2/9/90.8; v/v) and ultraviolet detection at 245 nm. The recoveries of 6beta-OHF from C18 cartridges were 93.2 and 93.9% when the authentic 6beta-OHF was added to the urine sample at the concentration of 50 and 300 ng/ml, respectively. Intra- and inter-day variations estimated at concentrations of 113-674 ng/ml were 2.9-5.6 and 4.9-8.1%, respectively. The method was applied to morning urine samples collected from HIV-positive pregnant women managed with protease inhibitor containing anti-retroviral regimens.

A randomized study of antiretroviral management based on plasma genotypic antiretroviral resistance testing in patients failing therapy. CPCRA 046 Study Team for the Terry Beirn Community Programs for Clinical Research on AIDS

OBJECTIVE

To determine the short-term effects of using genotypic antiretroviral resistance testing (GART) with expert advice in the management of patients failing on a protease inhibitor and two nucleoside reverse transcriptase inhibitors.

DESIGN

Prospective randomized controlled trial.

SETTING

Multicenter community-based clinical trials network.

PATIENTS

One-hundred and fifty-three HIV-infected adults with a threefold or greater rise in plasma HIV-1 RNA on at least 16 weeks of combination antiretroviral therapy.

INTERVENTIONS

Randomization was either to a GART group, where genotype interpretation and suggested regimens were provided to clinicians, or to a no-GART group, where treatment choices were made without such input.

MAIN OUTCOMES MEASURES

Plasma HIV-1 RNA levels and CD4 cell counts were measured at 4, 8, and 12 weeks following randomization. The primary endpoint was change in HIV-1 RNA levels from baseline to the average of the 4 and 8 week levels.

RESULTS

The average baseline CD4 cell count was 230 x 10(6) cells/l and the median HIV-1 RNA was 28,085 copies/ml. At entry, 82 patients were failing on regimens containing indinavir, 51 on nelfinavir, 11 on ritonavir, and nine on saquinavir. HIV-1 RNA, averaged at 4 and 8 weeks, decreased by 1.19 log10 for the 78 GART patients and -0.61 log10 for the 75 no-GART patients (treatment difference: -0.53 log, 95% confidence interval, -0.77 to -0.29; P = 0.00001). Overall, the best virologic responses occurred in patients who received three or more drugs to which their HIV-1 appeared to be susceptible.

CONCLUSION

In patients failing triple drug therapy, GART with expert advice was superior to no-GART as measured by short-term viral load responses.

Prophylactic and therapeutic benefits of short-term 9-[2-(R)-(phosphonomethoxy)propyl]adenine (PMPA) administration to newborn macaques following oral inoculation with simian immunodeficiency virus with reduced susceptibility to PMPA

Simian immunodeficiency virus (SIV) infection of newborn macaques is a useful animal model of human pediatric AIDS to study pathogenesis and to develop intervention strategies aimed at preventing infection or delaying disease progression. In previous studies, we demonstrated that 9-¿2-(R)-(phosphonomethoxy)propylădenine (PMPA; tenofovir) was highly effective in protecting newborn macaques against infection with virulent wild-type (i.e., drug-susceptible) SIVmac251. In the present study, we determined how reduced drug susceptibility of the virus inoculum affects the chemoprophylactic success. SIVmac055 is a virulent isolate that has a fivefold-reduced in vitro susceptibility to PMPA, associated with a K65R mutation and additional amino acid changes (N69T, R82K, A158S, S211N) in reverse transcriptase (RT). Eight newborn macaques were inoculated orally with SIVmac055. The three untreated control animals became SIVmac055 infected; these animals had persistently high viremia and developed fatal immunodeficiency within 3 months. Five animals were treated once daily with PMPA (at 30 mg/kg of body weight) for 4 weeks, starting 24 h prior to oral SIVmac055 inoculation. Two of the five PMPA-treated animals had no evidence of infection. The other three PMPA-treated infant macaques became infected but had a delayed viremia, enhanced antiviral antibody responses, and a slower disease course (AIDS in 5 to 15 months). No reversion to wild-type susceptibility or loss of the K65R mutation was detected in virus isolates from any of the PMPA-treated or untreated SIVmac055-infected animals. Several additional amino acid changes developed in RT, but they were not exclusively associated with PMPA therapy. The results of this study suggest that prophylactic administration of PMPA to human newborns and to adults following exposure to human immunodeficiency virus will still be beneficial even in the presence of viral variants with reduced susceptibility to PMPA.

Prevalence of Transmitted Nucleoside Analogue-Resistant HIV-1 Strains and Pre-Existing Mutations in Pol Reverse Transcriptase and Protease Region: Outcome after Treatment in Recently Infected Individuals

We retrospectively studied 38 Italian recently HIV-1-infected subjects who seroconverted from 1994 to 1997 to investigate: (i) the prevalence of nucleoside reverse transcriptase inhibitors (NRTI)-related mutations at primary infection; (ii) the proportion of naturally occurring mutations in reverse transcriptase (RT) and protease regions of patients naive for non-nucleoside RT inhibitors (NNRTIs) and protease inhibitors (PIs); (iii) the drug-susceptibility to NRTIs and PIs in subjects with NRTI-and/or PI-related mutations; and (iv) the outcome of seroconverters treated with various NRTIs or NRTI/PI regimens. Baseline HIV-1 plasma viraemia and absolute CD4 count at baseline could not be used to distinguish patients with NRTI- and/or PI-related pre-existing mutations from those with wild-type virus ( P=0.693 and P=0.542, respectively). The frequency of zidovudine-related mutations was 21% in the study period. The response to treatment was not significantly different in subjects with or without genotypic zidovudine-related mutations at primary infection ( P=0.744 for HIV-1 RNA and P=0.102 for CD4 cells). Some natural variation (2.6%) was present within regions 98–108 and 179–190 of RT involved in NNRTI resistance. The high natural polymorphism in the protease region present in our patients was similar to that reported by others. In our study some PI-associated substitutions, thought to be compensatory in protease enzymatic function, could confer intermediate to high PI-resistance. As discrepancies between genotypic and phenotypic results may exist in recent seroconverters, our data suggest that the role of transmitted NRTI- and PI-resistant variants remain to be fully elucidated in vivo.

Transmission and Prevalence of HIV Resistance among Treatment-Naive Subjects

Recent reports demonstrate the transmission of drug-resistant HIV-1 variants to newly infected individuals, although estimates of the prevalence of drug resistance among populations from different geographic regions are highly varied. The interpretation and comparison of available study results are confounded by the lack of consensus regarding the nomenclature and reporting of antiviral resistance. This report re-evaluates previously presented and published data using uniform criteria for genotypic and phenotypic drug resistance. Treatment-inexperienced and recently or chronically infected populations are reviewed. The prevalence of transmitted drug resistance ranges from 1% to 11% among recently infected persons using these criteria. Programmes to monitor and characterize drug resistance among newly infected persons and their source partners are essential to evaluate the selection processes that influence the transmission of certain genetic variants of HIV. Temporal trends in the prevalence of transmitted drug resistance among diverse populations are necessary to evaluate the potential need for selective and generalized drug resistance screening programmes among newly infected, treatment-naive patients.

Rapid development of genotypic resistance to lamivudine when combined with zidovudine in pregnancy

The prevention of mother to child transmission of HIV-1 by zidovudine monotherapy is well known, but increasingly combination anti-retroviral therapy is prescribed during pregnancy. In this prospective study, 19 pregnant women with human immunodeficiency virus-1 (HIV-1) infection who elected to take anti-retroviral therapy during the second and third trimesters were treated with zidovudine or zidovudine plus lamivudine. Fourteen women treated with zidovudine monotherapy had a mean 0.3 log(10) reduction in viral load and a mean 52 x 10(6)/L (17%) increase in CD4+ lymphocytes at delivery compared with pre-treatment samples. Genotypic mutations associated with decreased susceptibility to zidovudine were detected in 2 of 10 women at delivery. Five women with more advanced HIV-1 infection were treated with zidovudine plus lamivudine and a mean 1.5 log(10) reduction in viral load together with a mean 30 x 10(6)/L (33%) increase in CD4+ lymphocytes was observed in this group. However, four of five women in the dual therapy arm had the M184V mutation in the reverse transcriptase gene associated with decreased susceptibility to lamivudine at delivery. We conclude that zidovudine plus lamivudine reduced HIV-1 plasma viraemia to low levels in pregnant women with advanced HIV-1 disease but the rapid development of genotypic resistance to lamivudine indicates that additional therapy is required both for the long-term benefit of the mothers and to prevent the development of resistant virus that may be transmitted to the infant.

Neurobehavioral effects of prenatal lamivudine (3TC) exposure in preweaning mice

The present study provides a characterization of the behavioral changes induced in preweaning mice by prenatal exposure to lamivudine (3TC), an antiviral drug recently entered in the clinical practice to treat HIV patients. Pregnant CD1 mice were given per os bidaily either 3TC at different doses (125, 250, or 500 mg/kg) or vehicle solution (saline 0.9%) from pregnancy day 10 to delivery. Data on reproductive performance, such as gestation length, litter size, and offspring viability, were collected. Offspring were then examined for a series of different somatic and behavioral end points, including sensorimotor development, ontogenetic pattern of ultrasonic vocalization, passive avoidance learning, and locomotor activity. In the absence of gross changes in somatic and sensorimotor development, a slight change in ultrasound emission was found on postnatal day (PND) 3, with 125 and 500 mg/kg 3TC-treated offspring emitting a lower number of ultrasounds. Learning and retention performances of a passive-avoidance task on PND 20-21 were unaffected by 3TC treatment, while decreased habituation in an automated locomotor activity test was evident in male offspring exposed to 250 and 500 mg/kg 3TC.

Effects of prenatal AZT on mouse neurobehavioral development and passive avoidance learning

Recent evidence has shown that perinatal administration of zidovudine (AZT) to HIV-infected mothers reduces the risk of maternal-infant transmission of the virus. Treatment of pregnant seropositive women with AZT is becoming a common medical practice, despite the paucity of information about the potential neurotoxic/behavioral-teratogenic effects of AZT on the developing organism. The aim of the present study is to evaluate in mice the short-, medium-, and long-term effects of prenatal exposure to AZT on neurobehavioral development. Pregnant mice were given 0.2, 0.4, and 2.0 mg/ml AZT in drinking water from day 10 of gestation to delivery. Offspring's viability was severely affected in the 2.0 mg/ml AZT group. Thus, behavioral analysis was carried out in offspring of 0.2 and 0.4 mg/ml AZT-treated females only. Some limited but significant alterations were found, such as stunted body weight, delayed appearance of the pole-grasping reflex, and a slight impairment in the acquisition phase of a passive avoidance response. Moreover, sexual differences in some items of the social behavior repertoire appeared to be affected by AZT treatment.

Maternal and umbilical cord serum zidovudine levels in human immunodeficiency virus infection

The aim of this study was to determine the maternal and umbilical cord serum ZDV levels at delivery in HIV-1 infected parturients treated with a short-course ZDV regimens in late pregnancy and labour. Serum ZDV and its metabolite were measured by high-performance liquid chromatography. Concentrations of ZDV and its metabolite in umbilical cord blood appeared similar to maternal concentrations. There was a significant positive correlation between serum ZDV and its metabolite in maternal and umbilical cord concentrations. At delivery, maintenance of optimal virustatic ZDV concentration with oral antenatal and oral intermittent intrapartum ZDV dosage regimen can be achieved in only 53% of cases. The regimens used in this study were useful but not as effective as the ACTG 076 regimen with an intravenous dose intrapartum plus the oral administration to the infants for 6 weeks.

Administration of 9-[2-(phosphonomethoxy)propyl]adenine (PMPA) for prevention of perinatal simian immunodeficiency virus infection in rhesus macaques

Simian immunodeficiency virus (SIV) infection of newborn macaques is a useful animal model to explore novel strategies to reduce perinatal human immunodeficiency virus (HIV) infection. The availability of two easily distinguishable virus isolates, SIVmac251 and the simian/human immunodeficiency virus chimera SHIV-SF33, allows tracing the source of infection following inoculation with both viruses by different routes. In the present study, we evaluated the efficacy of pre- and postinoculation treatment regimens with 9-[2-(phosphonomethoxy)propyl]adenine (PMPA) to protect newborn macaques against simultaneous oral SIVmac251 and intravenous SHIV-SF33 inoculation. Untreated newborns became persistently infected following virus inoculation. When three pregnant macaques were given a single subcutaneous dose of PMPA 2 hr before cesarean section, their newborns became SIV-infected following SIV and SHIV inoculation shortly after birth. In contrast, when four newborn macaques were inoculated simultaneously with SIV and SHIV, and started immediately on PMPA treatment for 2 weeks, only one animal became persistently SIV-infected; the remaining three PMPA-treated newborns, however, had some evidence of an initial transient virus infection but were seronegative and healthy at 8 months of age. Our data demonstrate that PMPA treatment can reduce perinatal SIV infection and suggest that similar strategies may also be effective against HIV.

Differential tropism and chemokine receptor expression of human immunodeficiency virus type 1 in neonatal monocytes, monocyte-derived macrophages, and placental macrophages

Laboratory-adapted (LA) macrophage-tropic (M-tropic) human immunodeficiency virus type 1 (HIV-1) isolates (e.g., HIV-1(Ba-L)) and low-passage primary (PR) isolates differed markedly in tropism for syngeneic neonatal monocytes, monocyte-derived macrophages (MDMs), and placental macrophages (PMs). Newly adherent neonatal monocytes and cultured PMs were highly refractory to infection with PR HIV-1 isolates yet were permissive for LA M-tropic isolates. Day 4 MDMs were also permissive for LA M-tropic isolates and additionally, were permissive for over half the PR isolates tested. Qualitative differences in PR HIV-1 infection of monocytes/MDMs could not be correlated with CD4 levels alone, and in all three cell types the block to PR HIV-1 strain replication preceded reverse transcription. Neonatal monocyte susceptibility to PR HIV-1 strains correlated with increasing CCR-5 expression during maturation. CCR-5 could not be detected on newly adherent (day 1) neonatal monocytes, in contrast to adult monocytes (H. Naif et al., J. Virol. 72:830-836, 1998), but was readily detectable after 4 to 7 days of culture. However, moderate CCR-5 mRNA levels were present in day 1 neonatal monocytes and remained constant during monocyte maturation. CCR-5 was not detectable on the surface of PMs, yet the receptor was present within permeabilized cells. Notably, two brain-derived PR HIV-1 isolates from a single patient, differing in their V3 loops, were discordant in their abilities to infect neonatal monocytes/MDMs and PMs, yet both isolates could infect newly adherent adult monocytes. Together these data strongly suggest that LA HIV-1 isolates are able to infect neonatal monocytes at earlier stages of maturation and lower-level expression of CCR-5 than PR isolates. The differences between neonatal and adult monocytes in susceptibility to PR isolates may also be related to the level of CCR-5 expression.

Prevention of vertical HIV transmission: additive protective effect of elective Cesarean section and zidovudine prophylaxis. Swiss Neonatal HIV Study Group

OBJECTIVE

To study the effect of elective Cesarean section and zidovudine prophylaxis on vertical HIV transmission.

DESIGN

Prospective study.

SETTING

Obstetric and paediatric clinics in Switzerland.

PARTICIPANTS

Children of mothers with HIV infection identified before or at delivery.

INTERVENTIONS

Routine use of elective Cesarean section for HIV-infected parturients by some Swiss centres since 1985. National recommendation for zidovudine prophylaxis in mid-1994.

MAIN OUTCOME MEASURE

HIV infection status of children.

RESULTS

In a cohort of 494 children born at least 6 months before the analysis date, 67 out of 414 children with known infection status were found to be infected, giving an overall transmission rate of 16.2% [95% confidence interval (CI), 13.0-18.51. Elective Cesarean section with intact membranes and without previous labour was associated with a lower transmission rate of 6% [odds ratio (OR), 0.29; 95% CI, 0.12-0.70; P = 0.006 versus other delivery modes]. Transmission rate was intermediate after spontaneous delivery or non-elective Cesarean section (18%), and higher after obstetric interventions (27%; test for trend, P < 0.001). Since mid-1994, 78% of all women with registered pregnancies have received some form of zidovudine prophylaxis. Transmission rate was reduced from 17 to 7% after any zidovudine exposure (OR, 0.4; 95% CI, 0.11-1.41). Combined use of elective Cesarean section and zidovudine resulted in a 0% transmission rate (none out of 31), compared with 8% (seven out of 86) after elective Cesarean section without zidovudine, 17% (four out of 24) after zidovudine alone, and 20% (55 out of 271) after no intervention.

CONCLUSIONS

Elective Cesarean section and zidovudine prophylaxis appear to have an additive effect in the prevention of vertical HIV transmission.

Zidovudine

Zidovudine was the first agent approved for treatment of HIV disease, and since its widespread availability in 1987, the pharmacokinetic disposition and clinical effects of ZDV have been extensively evaluated. In addition to its utility as a component of a multidrug combination regimen for the treatment of adult and pediatric HIV-1 infection, it is the only agent approved by the FDA for the prevention of mother-to-child HIV-1 transmission. The effectiveness of ZDV for the prevention of mother-to-child HIV-1 transmission has been demonstrated in several studies. The optimal time during gestation to initiate ZDV therapy and the relative importance of the intrapartum and newborn components is the focus of both current interventional and observational studies. Until more information is available from these trials, the combined maternal/newborn ZDV regimen studied in ACTG 076 remains the recommended treatment regimen of choice in the United States.

Acceptability and impact of zidovudine for prevention of mother-to-child human immunodeficiency virus-1 transmission in France

We studied the propagation and the impact of zidovudine prevention on the human immunodeficiency virus-1 transmission rate from infected mothers to their infants in the French nationwide prospective cohort. Infection was diagnosed in the children on the basis of at least two positive human immunodeficiency virus-1 polymerase chain reaction tests, culture, or both. The transmission rate among treated women was compared with that among untreated women during the same period and with that among women enrolled in the cohort since 1986. The impact of zidovudine was analyzed according to the women's clinical and biologic characteristics, the mode of delivery, and use of zidovudine therapy before the pregnancy. Nearly 90% of women were treated as soon as the second half of 1994. In 1994 and 1995, 80% of mother-child pairs received at least one of the three phases of preventive treatment. Among the 663 mothers enrolled during these 2 years, only six refused the treatment. Zidovudine treatment was associated with a reduction in the transmission rate of nearly two-thirds, from 14% +/- 6% to 5% +/- 2% (p < 0.01). The degree of reduction was not influenced by the maternal CD4+ cell count or p24 antigenemia at delivery. Zidovudine treatment of the mother before the pregnancy considerably reduced the impact of preventive therapy; the transmission rate was significantly higher among pretreated mothers (20% versus 5%, p < 0.01) even after adjusting for maternal CD4+ cell count. Zidovudine prevention is now widely used in France and has had a major impact on the epidemiology of mother-child human immunodeficiency virus transmission. This justifies a policy of offering human immunodeficiency virus screening to all women before or shortly after the diagnosis of pregnancy.

Antiretroviral therapy during pregnancy. Beyond AZT (ZDV)

Although zidovudine (ZDV) monotherapy remains the standard for the prevention of mother-to-child transmission, it may now be inadequate therapy for treatment of the mother. The safety and efficacy of the newer therapeutic agents have yet to be established during pregnancy; however, the need to maintain maternal health mandates that clinicians understand the benefits and limitations of antiretroviral therapy beyond ZDV.