Breast-milk shedding of drug-resistant HIV-1 subtype C in women exposed to single-dose nevirapine

Maternal HIV drug resistance is associated with vertical transmission and is prevalent in infected infants

BACKGROUND

We aimed to assess if maternal HIV drug resistance is associated with an increased risk of HIV vertical transmission and to describe the dynamics of drug resistance in HIV-infected infants.

METHODS

A case-control study of PROMISE study participants. "Cases" were mother-infant pairs with HIV vertical transmission during pregnancy or breastfeeding and "controls" were mother-infant pairs without transmission matched 1:3 by delivery date and clinical site. Genotypic HIV drug resistance analyses were performed on mothers' and their infants' plasma at or near the time of infant HIV diagnosis. Longitudinal analysis of genotypic resistance was assessed in available specimens from infants, from diagnosis and beyond, including ART initiation and last study visits.

RESULTS

Our analyses included 85 cases and 255 matched controls. Maternal HIV drug resistance, adjusted for plasma HIV RNA load at infant HIV diagnosis, enrollment CD4 count, and antepartum regimens, was not associated with in utero/peripartum HIV transmission. In contrast, both maternal plasma HIV RNA load and HIV drug resistance were independent risk factors associated with vertical transmission during breastfeeding. Furthermore, HIV drug resistance was selected across infected infants during infancy.

CONCLUSIONS

Maternal HIV drug resistance and maternal viral load were independent risk factors for vertical transmission during breastfeeding, suggesting that nevirapine alone may be insufficient infant prophylaxis against drug-resistant variants in maternal breast milk. These findings support efforts to achieve suppression of HIV replication during pregnancy and suggest that breastfeeding infants may benefit from prophylaxis with a greater barrier to drug resistance than nevirapine alone.

Transmission of nevirapine-resistant HIV type 1 via breast milk to infants after single-dose nevirapine in Beira, Mozambique

Acquisition of nevirapine (NVP)-resistant human immunodeficiency virus type 1 (HIV-1) by breast-feeding infants after receipt of single-dose NVP to prevent mother-to-child transmission is not well defined. A prospective observational study of 307 infants evaluated the rate of breast milk transmission of NVP-resistant HIV and the concentrations of mutants over time. NVP resistance was detected in 9 of 24 infants (37.5%; 95% confidence interval, 18.8%-59.4%) infected via breast milk. Eight had a pure mutant HIV population at the time infection was first detected, and majority mutant populations persisted in all 6 infants with follow-up specimens. Infection of breast-feeding infants with NVP-resistant HIV resulted in mutants persisting as the dominant virus, which may indefinitely compromise treatment with NVP-based antiretroviral regimens.

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

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

Kinetics of nevirapine and its impact on HIV-1 RNA levels in maternal plasma and breast milk over time after perinatal single-dose nevirapine

OBJECTIVE

To determine kinetics after single-dose nevirapine and the impact on HIV RNA [viral load (VL)] in maternal plasma and breast milk (BM).

METHODS

Cohort of 120 HIV-1-infected pregnant Ugandan women received perinatal single-dose nevirapine alone and followed up with their infants through 24 weeks postdelivery. We assessed the relationship of nevirapine concentration (tandem mass spectroscopy) and HIV-1 VL (Roche AMPLICOR HIV-1 Kit, version 1.5) in maternal plasma and BM over time.

RESULTS

At week 1 postpartum, NVP (≥10 ng/mL) was detected in all 53 plasma and 47 of 51 (92.2%) BM samples with median (interquartile ranges) of, respectively, 171 (78-214) ng/mL and 112 (64-158) ng/mL, P = 0.075, which decreased subsequently with traces persisting through week 4 in plasma. Plasma and BM VL dropped by week 1 and were highly correlated at delivery (R = 0.71, P < 0.001) and week 1 (R = 0.69, P < 0.001) but not thereafter. At week 1, VL correlated inversely with NVP concentration in plasma (R = 0.39, P = 0.004) and BM (R = 0.48, P = 0.013). There was a VL rebound in both compartments, which peaked at week 4 to levels greater than those at week 1 [significantly in plasma (P < 0.001) but not in BM] and remained stable thereafter. Median VL was consistently greater (11- to 50-fold) in plasma than BM at all time points (all P < 0.001).

CONCLUSIONS

After single-dose nevirapine, NVP concentration was comparably high through week 1, accompanied by suppression of plasma and BM VL. A longer "tail" (>1 week) of potent postnatal antiretroviral drugs is warranted to minimize the observed VL rebound and potential for NVP resistance as a result of persistent NVP traces.

Genetic diversity of simian immunodeficiency virus encoding HIV-1 reverse transcriptase persists in macaques despite antiretroviral therapy

The impact of antiretroviral therapy (ART) on the genetics of simian immunodeficiency virus (SIV) or human immunodeficiency virus (HIV) populations has been incompletely characterized. We analyzed SIV genetic variation before, during, and after ART in a macaque model. Six pigtail macaques were infected with an SIV/HIV chimeric virus, RT-SHIV(mne), in which SIV reverse transcriptase (RT) was replaced by HIV-1 RT. Three animals received a short course of efavirenz (EFV) monotherapy before combination ART was started. All macaques received 20 weeks of tenofovir, emtricitabine, and EFV. Plasma virus populations were analyzed by single-genome sequencing. Population diversity was measured by average pairwise difference, and changes in viral genetics were assessed by phylogenetic and panmixia analyses. After 20 weeks of ART, viral diversity was not different from pretherapy viral diversity despite more than 10,000-fold declines in viremia, indicating that, within this range, there is no relationship between diversity and plasma viremia. In two animals with consistent SIV RNA suppression to <15 copies/ml during ART, there was no evidence of viral evolution. In contrast, in the four macaques with viremias >15 copies/ml during therapy, there was divergence between pre- and during-ART virus populations. Drug resistance mutations emerged in two of these four animals, resulting in virologic failure in the animal with the highest level of pretherapy viremia. Taken together, these findings indicate that viral diversity does not decrease with suppressive ART, that ongoing replication occurs with viremias >15 copies/ml, and that in this macaque model of ART drug resistance likely emerges as a result of incomplete suppression and preexisting drug resistance mutations.

Addition of 7 days of zidovudine plus lamivudine to peripartum single-dose nevirapine effectively reduces nevirapine resistance postpartum in HIV-infected mothers in Malawi

BACKGROUND

We assessed whether 7 days of zidovudine + lamivudine postpartum with single-dose nevirapine at labor decreases nevirapine resistance in HIV-infected women in Malawi.

METHODS

HIV-infected pregnant women receiving intrapartum single-dose nevirapine and 7 days of zidovudine + lamivudine (n = 132) and women receiving intrapartum single-dose nevirapine alone (n = 66) were followed from an antenatal visit through 6 weeks postpartum. Plasma specimens at 2 and 6 weeks postpartum were tested for genotypic resistance to nevirapine by population sequencing and sensitive real-time polymerase chain reaction. Poisson regression was used to determine predictors of postpartum nevirapine resistance.

RESULTS

Median HIV RNA was similar at entry (4.27 log vs. 4.35 log, P = 0.87), differed at 2 weeks postpartum (2.67 log vs. 3.58 log, P < 0.0001) but not at 6 weeks postpartum (4.49 log vs. 4.40 log, P = 0.79), between single-dose nevirapine/zidovudine + lamivudine and single-dose nevirapine groups, respectively. Nevirapine resistance, measured by population sequencing and sensitive real-time polymerase chain reaction, was significantly less common in those receiving single-dose nevirapine/zidovudine + lamivudine compared with single-dose nevirapine, respectively, at 2 weeks [10% (4 of 40) vs. 74% (31 of 42), P < 0.0001] and 6 weeks postpartum [10% (11 of 115) vs. 64% (41 of 64), P < 0.0001; adjusted relative risk = 0.18, 95% confidence interval (0.10 to 0.34)].

CONCLUSIONS

The significant decrease in nevirapine resistance conferred by 1 week of zidovudine + lamivudine should help policymakers optimize peripartum HIV prophylaxis recommendations.

Genetic analyses of HIV-1 env sequences demonstrate limited compartmentalization in breast milk and suggest viral replication within the breast that increases with mastitis

The concentration of human immunodeficiency virus type 1 (HIV-1) is generally lower in breast milk than in blood. Mastitis, or inflammation of the breast, is associated with increased levels of milk HIV-1 and risk of mother-to-child transmission through breastfeeding. We hypothesized that mastitis facilitates the passage of HIV-1 from blood into milk or stimulates virus production within the breast. HIV-1 env sequences were generated from single amplicons obtained from breast milk and blood samples in a cross-sectional study. Viral compartmentalization was evaluated using several statistical methods, including the Slatkin and Maddison (SM) test. Mastitis was defined as an elevated milk sodium (Na(+)) concentration. The association between milk Na(+) and the pairwise genetic distance between milk and blood viral sequences was modeled using linear regression. HIV-1 was compartmentalized within milk by SM testing in 6/17 (35%) specimens obtained from 9 women, but all phylogenetic clades included viral sequences from milk and blood samples. Monotypic sequences were more prevalent in milk samples than in blood samples (22% versus 13%; P = 0.012), which accounted for half of the compartmentalization observed. Mastitis was not associated with compartmentalization by SM testing (P = 0.621), but Na(+) was correlated with greater genetic distance between milk and blood HIV-1 populations (P = 0.041). In conclusion, local production of HIV-1 within the breast is suggested by compartmentalization of virus and a higher prevalence of monotypic viruses in milk specimens. However, phylogenetic trees demonstrate extensive mixing of viruses between milk and blood specimens. HIV-1 replication in breast milk appears to increase with inflammation, contributing to higher milk viral loads during mastitis.

Nevirapine resistance by timing of HIV type 1 infection in infants treated with single-dose nevirapine

BACKGROUND

In women, single-dose nevirapine for prophylaxis against mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) selects for nevirapine-resistant HIV-1, which subsequently decays rapidly. We hypothesized that the selection, acquisition, and decay of nevirapine-resistant HIV-1 differs in infants, varying by the timing of HIV-1 infection.

METHODS

We conducted a prospective, observational study of 740 Mozambican infants receiving single-dose nevirapine prophylaxis and determined the timing of infection and concentrations of nevirapine-resistant HIV-1 over time.

RESULTS

Infants with established in utero infection had a high rate (87.0%) of selection of nevirapine-resistant HIV-1 mutants, which rapidly decayed to undetectable levels. The few without nevirapine resistance received zidovudine with single-dose nevirapine and/or their mothers took alternative antiretroviral drugs. Infants with acute in utero infection had a lower rate of nevirapine-resistant HIV-1 (33.3%; P = .006, compared with established in utero infection), but mutants persisted over time. Infants with peripartum infection also had a lower rate of nevirapine-resistant HIV-1 (38.1%; P = .001, compared with established in utero infection) but often acquired 100% mutant virus that persisted over time (P = .017, compared with established in utero infection).

CONCLUSIONS

The detection and persistence of nevirapine-resistant HIV-1 in infants after single-dose nevirapine therapy vary by the timing of infection and the antiretroviral regimen. In infants with persistent high-level nevirapine-resistant HIV-1, nevirapine-based antiretroviral therapy is unlikely to ever be efficacious because of concentrations in long-lived viral reservoirs. However, the absence or decay of nevirapine-resistant HIV-1 in many infants suggests that nevirapine antiretroviral therapy may be effective if testing can identify these individuals.

Emergence and persistence of nevirapine resistance in breast milk after single-dose nevirapine administration

OBJECTIVE

Single-dose nevirapine (NVP) (sdNVP) can reduce the risk of HIV vertical transmission. We assessed risk factors for NVP resistance in plasma and breast milk from sdNVP-exposed Ugandan women.

METHODS

Samples were analyzed using the Roche AMPLICOR HIV-1 Monitor Test Kit, version 1.5, and the ViroSeq HIV-1 Genotyping System. NVP concentrations were determined by liquid chromatography with tandem mass spectroscopy.

RESULTS

HIV genotypes (plasma and breast milk) were obtained for 30 women 4 weeks after sdNVP (HIV subtypes: 15A, 1C, 12D, two recombinant). NVP resistance was detected in 12 (40%) of 30 breast milk samples. There was a nonsignificant trend between detection of NVP resistance in breast milk and plasma (P = 0.06). There was no association of HIV resistance in breast milk with median maternal pre-NVP viral load or CD4 cell count, median breast milk viral load at 4 weeks, breast milk sodium more than 10 mmol/l, HIV subtype, or concentration of NVP in breast milk or plasma.

CONCLUSION

NVP resistance was frequently detected in breast milk 4 weeks after sdNVP exposure. In this study, we were unable to identify specific factors associated with breast milk NVP resistance.

Pharmacokinetics and disposition of rilpivirine (TMC278) nanosuspension as a long-acting injectable antiretroviral formulation

The next-generation human immunodeficiency virus type 1 (HIV-1) nonnucleoside reverse transcriptase inhibitor rilpivirine (TMC278) was administered in rats and dogs as single intramuscular (IM) or subcutaneous (SC) injections, formulated as a 200-nm nanosuspension. The plasma pharmacokinetics, injection site concentrations, disposition to lymphoid tissues, and tolerability were evaluated in support of its potential use as a once-monthly antiretroviral agent in humans. Rilpivirine plasma concentration-time profiles showed sustained and dose-proportional release over 2 months in rats and over 6 months in dogs. The absolute bioavailability approached 100%, indicating a complete release from the depot, in spite of rilpivirine concentrations still being high at the injection site(s) 3 months after administration in dogs. For both species, IM administration was associated with higher initial peak plasma concentrations and a more rapid washout than SC administration, which resulted in a stable plasma-concentration profile over at least 6 weeks in dogs. The rilpivirine concentrations in the lymph nodes draining the IM injection site exceeded the plasma concentrations by over 100-fold 1 month after administration, while the concentrations in the lymphoid tissues decreased to 3- to 6-fold the plasma concentrations beyond 3 months. These observations suggest uptake of nanoparticles by macrophages, which generates secondary depots in these lymph nodes. Both SC and IM injections were generally well tolerated and safe, with observations of a transient inflammatory response at the injection site. The findings support clinical investigations of rilpivirine nanosuspension as a long-acting formulation to improve adherence during antiretroviral therapy and for preexposure prophylaxis.

Postpartum antiretroviral drug resistance in HIV-1-infected women receiving pregnancy-limited antiretroviral therapy

BACKGROUND

Pregnancy-limited antiretroviral therapy (PLAT) drastically reduces HIV-1 transmission to the newborn, but may select for antiretroviral drug resistance mutations in mothers.

METHODS

We evaluated antiretroviral-naive, HIV-1-infected pregnant women who received PLAT between 1998 and 2005, and had 2-month or 6-month postpartum plasma samples available with HIV-1 RNA levels more than 500 copies/ml. Postpartum drug resistance mutation rates were assessed blindly using population sequencing and allele-specific PCR (ASPCR) of the M184V, K103N and D30N mutations. Factors associated with selection of drug resistance mutations were investigated.

RESULTS

One hundred and forty-six women were included. All women received zidovudine and lamivudine during pregnancy; 76% also received nelfinavir and 8.2% nevirapine. Resistance data were available from 114 women (78%). Postpartum rates of single-class, dual-class, and triple-class resistance were, respectively, 43, 6.1 and 0% (63.2, 10.5 and 1.7% by ASPCR). In women receiving dual or triple PLAT, respectively, postpartum M184V/I rates were 65% (95% by ASPCR) and 28.7% (51.6% by ASPCR), respectively (P < 0.01). Postpartum nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance rates among women receiving nevirapine were 25% for K103N (37.5% by ASPCR) and 12.5% for Y188C. Protease inhibitor resistance rates in women receiving nelfinavir were 1.1% for D30N (1.1% by ASPCR) and 1.1% for L90M. Dual versus triple PLAT and prolonged zidovudine exposure were associated with selection of M184V. Nevirapine use and length of zidovudine and lamivudine exposure were associated with selection of K103N.

CONCLUSION

PLAT is associated with frequent selection of resistance to drugs with low-genetic barrier. Triple-drug PLAT decreases the odds for M184V selection. Routine postpartum genotypic resistance testing may be useful to guide future treatment decisions in mothers.

Response to nonnucleoside reverse transcriptase inhibitor-based therapy in HIV-infected children with perinatal exposure to single-dose nevirapine

We set out to investigate whether there are clinically significant consequences when children with perinatal exposure to single-dose nevirapine are initiated on a nonnucleoside reverse transcriptase inhibitor (NNRTI) containing a highly active antiretroviral therapy (HAART) regimen. We carried out a chart and database review of 104 HIV-infected children, who had initiated HAART with an NNRTI at JCRC and were less than or equal to 5 years of age, 35 (33.7%) of whom had prior exposure to perinatal single-dose nevirapine. We studied the viral load and CD4 percentage at baseline, at week 24, and at week 48 after the start of HAART in children exposed and not exposed to perinatal single-dose nevirapine, as well as the results of genotypic resistance testing done for the children who had failed to achieve virologic suppression on HAART. At weeks 24 and 48 after initiating HAART, children not exposed to single-dose nevirapine were 3.28 times [OR = 3.28, 95% CI: (1.37 to 9.20), p = 0.0167] and 3.47 times [OR = 3.47, 95% CI: (1.28 to 9.37), p = 0.0091] more likely to achieve virologic suppression compared to children exposed to single-dose nevirapine, respectively. However, the CD4 cell response at weeks 24 and 48 was not worse in the children exposed to single-dose nevirapine. In 10 children with perinatal exposure to single-dose nevirapine, NNRTI resistance mutations, mostly K103N, Y181C, and G109A, were identified. HIV-infected children with perinatal exposure to single-dose nevirapine are less likely to achieve short-term virologic suppression when started on an NNRTI-containing regimen, when compared to those who were not exposed to it, probably because the exposure predisposes them to developing NNRTI resistance mutations.

Comparison of HIV type 1 sequences from plasma, cell-free breast milk, and cell-associated breast milk viral populations in treated and untreated women in Mozambique

We analyzed the sequences of the HIV viral populations obtained from plasma, cell-free breast milk, and breast milk cells of HAART-treated (23) and untreated (30) HIV-infected women to obtain information about the origin of the breast milk virus. Sequence analyses of viruses were performed using the TruGene HIV-1 assay. Direct sequences of the reverse transcriptase (RT) and protease (PR) genes were analyzed using the Phylip 3.68 suite of sequence analysis program and pairwise evolutionary distances were calculated with the Kimura two parameter model for estimation of distances. We found that the genetic distances between the plasma and the cell-free breast milk viruses and between the cell-free and cell-associated breast milk viruses for RT were higher in HAART-receiving women than in untreated women, suggesting viral evolution under selective drug pressure in breast milk. Our data support the hypothesis of the presence of an actively replicating viral population in the breast milk compartment, distinct from that present in plasma.

Antiviral strategies

Viruses are obligatory intracellular parasites, whose replication depends on pathways and functions of the host cell. Consequently, it is difficult to define virus-specific functions as suitable targets for anti-infective therapy. However, significant progress has been made in the past 50 years towards the development of effective and specific antivirals. In particular, human immunodeficiency virus, hepatitis C virus, and hepatitis B virus, which cause chronic infections affecting millions of individuals world-wide, are a major focus of antiviral research. Initially, antivirals were mainly directed against virus-specific enzymes; more recently, drugs inhibiting the steps of virus entry or release have been developed. Rational approaches towards drug development, based on information about structure and function of viral proteins and molecular mechanisms of virus-host interactions, have become increasingly successful. Novel strategies currently explored in basic research or preclinical studies include approaches targeting host factors important for virus replication, the exploitation of the innate immune response system as well as the use of gene silencing strategies aimed at interfering with viral gene expression. Today, a number of effective virostatics targeting various viral replication steps are approved for treatment of important viral diseases. However, the use of these drugs is limited by the rapid development of antiviral resistance, which represents a central problem of current antiviral therapy.

Nevirapine resistance and breast-milk HIV transmission: effects of single and extended-dose nevirapine prophylaxis in subtype C HIV-infected infants

BACKGROUND

Daily nevirapine (NVP) prophylaxis to HIV-exposed infants significantly reduces breast-milk HIV transmission. We assessed NVP-resistance in Indian infants enrolled in the "six-week extended-dose nevirapine" (SWEN) trial who received single-dose NVP (SD-NVP) or SWEN for prevention of breast-milk HIV transmission but who also acquired subtype C HIV infection during the first year of life.

METHODS/FINDINGS

Standard population sequencing and cloning for viral subpopulations present at > or =5% frequency were used to determine HIV genotypes from 94% of the 79 infected Indian infants studied. Timing of infection was defined based on when an infant's blood sample first tested positive for HIV DNA. SWEN-exposed infants diagnosed with HIV by six weeks of age had a significantly higher prevalence of NVP-resistance than those who received SD-NVP, by both standard population sequencing (92% of 12 vs. 38% of 29; p = 0.002) and low frequency clonal analysis (92% of 12 vs. 59% of 29; p = 0.06). Likelihood of infection with NVP-resistant HIV through breast-milk among infants infected after age six weeks was substantial, but prevalence of NVP-resistance did not differ among SWEN or SD-NVP exposed infants by standard population sequencing (15% of 13 vs. 15% of 20; p = 1.00) and clonal analysis (31% of 13 vs. 40% of 20; p = 0.72). Types of NVP-resistance mutations and patterns of persistence at one year of age were similar between the two groups. NVP-resistance mutations did differ by timing of HIV infection; the Y181C variant was predominant among infants diagnosed in the first six weeks of life, compared to Y188C/H during late breast-milk transmission.

CONCLUSIONS/SIGNIFICANCE

Use of SWEN to prevent breast-milk HIV transmission carries a high likelihood of resistance if infection occurs in the first six weeks of life. Moreover, there was a continued risk of transmission of NVP-resistant HIV through breastfeeding during the first year of life, but did not differ between SD-NVP and SWEN groups. As with SD-NVP, the value of preventing HIV infection in a large number of infants should be considered alongside the high risk of resistance associated with extended NVP prophylaxis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00061321.

Drug resistance differences among HIV types and subtypes: a growing problem

Although HIV-1 subtype B accounts for only 10% of worldwide HIV infections, almost all knowledge regarding antiretroviral (ARV) drug development and viral resistance is based on this subtype. More recently, an increasing body of evidence suggests that distinct HIV genetic variants possess different biological properties, including susceptibility and response to ARVs. In this review, we will summarize recent in vitro and in vivo studies reporting such differences. In general terms, infections with most HIV variants respond well to ARVs, but minor differences in susceptibility, in the emergence and selection of subtype-specific drug resistance mutations and in the acquisition of similar mutations over the period of ARV exposure have been reported. Such differences impact on drugresistance interpretation algorithms, which are mostly based on inference from sequence information. Despite the differences observed, clinical response to ARV therapy among subjects infected with distinct HIV variants is effective, and the dissemination of ARV access in developing countries where non-B subtypes prevail should not be delayed.

Persistence of nevirapine in breast milk and plasma of mothers and their children after single-dose administration

OBJECTIVES

Nevirapine is widely used in the developing world for the prevention of mother-to-child transmission (PMTCT) of HIV. A single mutation in the HIV genome is sufficient to lead to significant nevirapine resistance. Persistence of low-level drug concentrations in body compartments can foster resistance formation. In this study, concentration-time courses of nevirapine after single-dose administration were analysed over an extended post-partum period.

PATIENTS AND METHODS

Breast milk and plasma samples of 62 HIV-positive Ugandan mother-child pairs who had received single-dose nevirapine were collected at delivery and 1, 2 and 6 weeks post-partum. Nevirapine concentrations were quantified by LC/tandem-mass-spectrometry using a quantification limit of 15 ng/mL, and a population pharmacokinetic (PK) analysis was performed.

RESULTS

Concentration-time profiles in breast milk, maternal plasma and child plasma showed similar shapes. At week 1, median nevirapine concentrations were 164 ng/mL in maternal plasma, 114 ng/mL in breast milk and 183 ng/mL in child plasma. The population PK model predicted nevirapine concentrations>10 ng/mL (IC50 for nevirapine) for 13 days in breast milk, 14 days in maternal plasma and 18 days in child plasma in 80% of the samples.

CONCLUSIONS

Nevirapine concentrations were present for 2-3 weeks in the three compartments. The concentrations are probably sufficiently high to protect most breastfed children from HIV transmission during the first 2 weeks. The long presence of slowly decreasing levels of nevirapine is likely to induce resistance formation. Post-natal addition of antiretrovirals for 1 week only, as recommended in the current PMTCT guidelines, will not suffice to avoid nevirapine resistance formation.

Analysis of nevirapine (NVP) resistance in Ugandan infants who were HIV infected despite receiving single-Dose (SD) NVP versus SD NVP plus daily NVP up to 6 weeks of age to prevent HIV vertical transmission

BACKGROUND

Single-dose nevirapine (SD NVP) at birth plus NVP prophylaxis for the infant up to 6 weeks of age is superior to SD NVP alone for prevention of vertical transmission of human immunodeficiency virus (HIV) through breastfeeding. We analyzed NVP resistance in HIV-infected Ugandan infants who received either SD NVP or extended NVP prophylaxis.

METHODS

We tested plasma HIV by using a genotyping assay (ViroSeq; Celera Diagnostics), a phenotypic resistance assay (PhenoSense; Monogram Biosciences), and sensitive point mutation assay (LigAmp, for K103N, Y181C, and G190A).

RESULTS

When infants were 6 weeks old, ViroSeq detected NVP resistance in a higher proportion of infants in the extended NVP arm than in the SD NVP arm (21 of 25 [84%] vs. 12 of 24 [50%]; P = .01). Similar results were obtained with LigAmp and PhenoSense. In both study arms, infants who were HIV infected at birth frequently had NVP resistance detected. In contrast, infants in the extended NVP arm who were HIV infected after birth were more likely to have resistance detected at 6 weeks, compared with infants in the SD NVP arm. The use of extended NVP prophylaxis was also associated with detection of NVP resistance by ViroSeq at 6 months (7 of 7 [100%] infants in the extended NVP arm had resistance detected, compared with 1 of 6 [16.7%] infants in the SD NVP arm; P = .005).

CONCLUSIONS

The use of extended NVP prophylaxis was associated with increased selection for and persistence of NVP resistance in HIV-infected Ugandan infants.

The Status of HIV-1 Resistance to Antiretroviral drugs in Sub-Saharan Africa

Access to highly active antiretroviral therapy (HAART) for persons infected with HIV in sub-Saharan Africa has greatly improved over the past few years. However, data on long-term clinical outcomes of Africans receiving HAART, patterns of HIV resistance to antiretroviral drugs and implications of HIV type-1 (HIV-1) subtype diversity in Africa for resistance, are limited. In resource-limited settings, concerns have been raised that deficiencies in health systems could create the conditions for accelerated development of resistance. Coordinated surveillance systems are being established to assess the emergence of resistance and the factors associated with resistance development, and to create the possibility for adjusting treatment guidelines as necessary. The purpose of this report is to review the literature on HIV-1 resistance to antiretroviral drugs in sub-Saharan Africa, in relation to the drug regimens used in Africa, HIV-1 subtype diversity and overall prevalence of resistance. The report focuses on resistance associated with treatment, prevention of mother-to-child transmission and transmitted resistance. It also outlines priorities for public health action and research.

Suppression of viremia and evolution of human immunodeficiency virus type 1 drug resistance in a macaque model for antiretroviral therapy

Antiretroviral therapy (ART) in human immunodeficiency virus type 1 (HIV-1)-infected patients does not clear the infection and can select for drug resistance over time. Not only is drug-resistant HIV-1 a concern for infected individuals on continual therapy, but it is an emerging problem in resource-limited settings where, in efforts to stem mother-to-child-transmission of HIV-1, transient nonnucleoside reverse transcriptase inhibitor (NNRTI) therapy given during labor can select for NNRTI resistance in both mother and child. Questions of HIV-1 persistence and drug resistance are highly amenable to exploration within animals models, where therapy manipulation is less constrained. We examined a pigtail macaque infection model responsive to anti-HIV-1 therapy to study the development of resistance. Pigtail macaques were infected with a pathogenic simian immunodeficiency virus encoding HIV-1 reverse transcriptase (RT-SHIV) to examine the impact of prior exposure to a NNRTI on subsequent ART comprised of a NNRTI and two nucleoside RT inhibitors. K103N resistance-conferring mutations in RT rapidly accumulated in 2/3 infected animals after NNRTI monotherapy and contributed to virologic failure during ART in 1/3 animals. By contrast, ART effectively suppressed RT-SHIV in 5/6 animals. These data indicate that suboptimal therapy facilitates HIV-1 drug resistance and suggest that this model can be used to investigate persisting viral reservoirs.

International recommendations on antiretroviral drugs for treatment of HIV-infected women and prevention of mother-to-child HIV transmission in resource-limited settings: 2006 update

The World Health Organization recommends that countries adopt more effective antiretroviral regimens to increase the effectiveness of the prevention of mother-to-child human immunodeficiency virus (HIV) transmission programs. The 2006 guidelines recommend a tiered approach for the delivery of antiretroviral to pregnant women who are infected with HIV and include triple-drug antiretroviral treatment for those women who are eligible. Those women who are not eligible for antiretroviral treatment should receive a combination prophylaxis antiretroviral regimen, preferably zidovudine from 28 weeks of gestation; zidovudine, lamivudine, and a single dose of nevirapine during delivery; and zidovudine and lamivudine for 7 days after delivery to reduce the development of nevirapine resistance. Newborn infants should receive a single dose of nevirapine and 1-4 weeks of zidovudine, depending on the duration of the regimen received by the mother. Although steps are being taken to provide more effective regimens, the use of single-dose nevirapine alone should still be used in situations in which more effective regimens are not yet feasible or available. HIV transmission through breastfeeding remains a problem, and several interventions are under evaluation that include maternal and/or infant antiretroviral prophylaxis during breastfeeding.

Use of single-dose nevirapine for the prevention of mother-to-child transmission of HIV-1: does development of resistance matter?

Nevirapine resistance has been detected in a considerable proportion of women after single-dose nevirapine (SD-NVP) for the prevention of mother-to-child human immunodeficiency virus-1 transmission. As a result, concern has been raised about the effectiveness of subsequent nevirapine-based treatment. Studies in Thailand, Botswana, and South Africa have assessed virologic treatment response after SD-NVP. These studies did not find any significant difference in virologic response for women who began treatment >6 months after SD-NVP exposure. Two studies found worse response rates in women when treatment was initiated within 6 months of SD-NVP exposure. Furthermore, 2 studies found no difference in human immunodeficiency virus transmission rates from mother to child after the receipt of SD-NVP in repeat pregnancies. These data support the use of SD-NVP as 1 option for the prevention of mother-to-child human immunodeficiency virus-1 transmission in resource-limited settings, particularly in settings where more complex regimens are not yet available. Further research in the optimization of perinatal prevention regimens is needed.

Preserving breastfeeding practice through the HIV pandemic

Breastfeeding, particularly for the first 6 months of life, is unquestionably the ideal way to feed most infants. However, the human immunodeficiency virus (HIV) pandemic has caused debate and confusion about the best way for HIV-positive mothers to feed their children. This review provides recent key findings and opinions around making breastfeeding safer for HIV-positive women, and argues for preservation of breastfeeding, as opposed to complete avoidance of breastfeeding for all HIV-positive women.

Drug resistance in plasma and breast milk after single-dose nevirapine in subtype C HIV type 1: population and clonal sequence analysis

Single-dose nevirapine (SD NVP) reduces intrapartum HIV-1 transmission, but nonnucleoside reverse transcription (NNRTI) resistance mutations can emerge. Population sequencing among 32 subtype C HIV-1-infected, SD NVP-exposed Zimbawean women demonstrated NNRTI resistance in 25/32 (78%) women: 23/30 (77%) at 2 weeks, 11/31 (35%) at 8 weeks, and 5/27 (19%) at 24 weeks. A total of 447 unique TA clones (median = 28 per time point), from four women with resistance at 8 weeks but wild-type virus by population sequence at 24 weeks, identified NNRTI mutations in a median of 76% (range: 55-96%) of individual clones at 2 weeks, 48% (range: 33-80%) at 8 weeks, and 5% (range: 0-15%) by 24 weeks. NNRTI mutations in breast milk clones at 2 and weeks from one woman varied significantly from plasma. Population sequencing underestimates the diversity of NNRTI resistance mutations within minority populations following SD NVP in subtype C HIV-1 viral RNA in plasma and breast milk.

Persistence of nevirapine in breast milk after discontinuation of treatment

The objective of this study was to serially quantitate the concentration of nevirapine in breast milk after discontinuation of treatment. Samples were collected from both breasts of a human immunodeficiency virus-infected patient for 3 weeks. Nevirapine was quantifiable for up to 17 days after discontinuation of therapy; total nevirapine concentrations remained above the 90% inhibitory concentration for 6 days, and no differences were observed between breasts.

Prevalence of resistance to nevirapine in mothers and children after single-dose exposure to prevent vertical transmission of HIV-1: a meta-analysis

BACKGROUND

Single-dose nevirapine (NVP) is the main option for the prevention of mother-to-child transmission (PMTCT) of HIV-1 in countries with limited resources. However, the use of single-dose NVP results in HIV-1 viral resistance which could compromise the success of subsequent treatment of mother and child with antiretroviral combinations that include non-nucleosidic-reverse-transcriptase inhibitors. This systematic review and meta-analysis of summarized data aimed to estimate the proportion of mothers and children with NVP resistance mutations detected in plasma samples 4-8 weeks postpartum after single-dose NVP use for PMTCT.

METHODS

Systematic search of electronic databases (MEDLINE, PASCAL) and conference proceedings (1997 to February 2006). Inclusion of all studies, without design, place or language restrictions, meeting the following criteria: use of single-dose NVP; viral genotyping performed with standard sequence analyses, between 4 and 8 weeks postpartum, in plasma samples; available public report; report of mothers' median baseline plasma HIV-1 RNA levels. Data extraction by two independent reviewers using a standardized form created for this purpose. Logistic random effect models to obtain pooled estimates. Univariable and multivariable meta-regression to explore sources of heterogeneity.

RESULTS

The pooled estimate of NVP resistance prevalence was 35.7% [95% confidence interval (CI) 23.0-50.6] in women in 10 study arms using single-dose NVP +/- other antepartum antiretrovirals and 4.5% (CI 2.1-9.4) in three study arms providing also postpartum antiretrovirals (adjusted odds ratio 0.08; CI 0.04-0.16). The corresponding estimates in children were 52.6% (CI 37.7-67.0) in seven study arms using single-dose NVP only and 16.5% (CI 8.9-28.3) in eight study arms combining single-dose NVP with other antiretrovirals.

CONCLUSIONS

Single-dose NVP is widely used for PMTCT in resource-poor settings, but the burden of viral resistance is high in both women and children. It is substantially lower in studies providing additional postpartum antiretrovirals. The clinical implications of these findings should be further investigated.

Transmitted Resistance: An Overview and Its Potential Relevance to the Management of HIV-Infected Persons in Resource-Limited Settings

Transmitted resistance has become an important clinical problem in developed countries with long histories of antiretroviral use. In resource-limited settings, it is a foreseeable, if not insidiously emerging, issue. Any transmission route or currently approved antiretroviral drug may be involved. The clinical relevance of polymorphisms that commonly occur at sites known to be associated with resistance, and peculiarities of the non-B subtypes, are incompletely understood. Adverse clinical consequences that have been demonstrated with transmitted resistance include an increased risk of failing initial therapy and further development of resistance. Although treatment outcomes can be optimized by baseline resistance testing and virologic monitoring, these are impractical in most resource-limited settings at this time. The scale and impact of transmitted resistance can probably be reduced by comprehensive prevention and management strategies. Equally germane are epidemiological and clinical studies to extend understanding of the dynamics, clinical implications, and management of transmitted resistance.

Age and Sex Structured Model for Assessing the Demographic Impact of Mother-to-Child Transmission of HIV/AIDS

Age and sex structured HIV/AIDS model with explicit incubation period is proposed as a system of delay differential equations. The model consists of two age groups that are children (0-14 years) and adults (15-49 years). Thus, the model considers both mother-to-child transmission (MTCT) and heterosexual transmission of HIV in a community. MTCT can occur prenatally, at labour and delivery or postnatally through breastfeeding. In the model, we consider the children age group as a one-sex formulation and divide the adult age group into a two-sex structure consisting of females and males. The important mathematical features of the model are analysed. The disease-free and endemic equilibria are found and their stabilities investigated. We use the Lyapunov functional approach to show the local stability of the endemic equilibrium. Qualitative analysis of the model including positivity and boundedness of solutions, and persistence are also presented. The basic reproductive number ([Symbol: see text](0)) for the model shows that the adult population is responsible for the spread HIV/AIDS epidemic, thus up-to-date developed HIV/AIDS models to assess intervention strategies have focused much on heterosexual transmission by the adult population and the children population has received little attention. We numerically analyse the HIV/AIDS model to assess the community benefits of using antiretroviral drugs in reducing MTCT and the effects of breastfeeding in settings with high HIV/AIDS prevalence ratio using demographic and epidemiological parameters for Zimbabwe.

Response to antiretroviral therapy after a single, peripartum dose of nevirapine

BACKGROUND

A single dose of nevirapine during labor reduces perinatal transmission of human immunodeficiency virus type 1 (HIV-1) but often leads to viral nevirapine resistance mutations in mothers and infants.

METHODS

We studied the response to nevirapine-based antiretroviral treatment among women and infants who had previously been randomly assigned to a single, peripartum dose of nevirapine or placebo in a trial in Botswana involving the prevention of the transmission of HIV-1 from mother to child. All women were treated with antenatal zidovudine. The primary end point for mothers and infants was virologic failure by the 6-month visit after initiation of antiretroviral treatment, estimated within groups by the Kaplan-Meier method.

RESULTS

Of 218 women who started antiretroviral treatment, 112 had received a single dose of nevirapine and 106 had received placebo. By the 6-month visit after the initiation of antiretroviral treatment, 5.0% of the women who had received placebo had virologic failure, as compared with 18.4% of those who had received a single dose of nevirapine (P=0.002). Among 60 women starting antiretroviral treatment within 6 months after receiving placebo or a single dose of nevirapine, no women in the placebo group and 41.7% in the nevirapine group had virologic failure (P<0.001). In contrast, virologic failure rates did not differ significantly between the placebo group and the nevirapine group among 158 women starting antiretroviral treatment 6 months or more post partum (7.8% and 12.0%, respectively; P=0.39). Thirty infants also began antiretroviral treatment (15 in the placebo group and 15 in the nevirapine group). Virologic failure by the 6-month visit occurred in significantly more infants who had received a single dose of nevirapine than in infants who had received placebo (P<0.001). Maternal and infant findings did not change qualitatively by 12 and 24 months after the initiation of antiretroviral treatment.

CONCLUSIONS

Women who received a single dose of nevirapine to prevent perinatal transmission of HIV-1 had higher rates of virologic failure with subsequent nevirapine-based antiretroviral therapy than did women without previous exposure to nevirapine. However, this applied only when nevirapine-based antiretroviral therapy was initiated within 6 months after receipt of a single, peripartum dose of nevirapine. (ClinicalTrials.gov number, NCT00197587 [ClinicalTrials.gov].).

A Randomized, Double‐Blind, Placebo‐Controlled Trial of Combined Nevirapine and Zidovudine Compared with Nevirapine Alone in the Prevention of Perinatal Transmission of HIV in Zimbabwe

BACKGROUND

A single dose of nevirapine (sdNVP) administered to both mother and infant can decrease mother-to-child transmission of human immunodeficiency virus (HIV) by 47%, compared with ultra-short course zidovudine therapy (usZDV). There is limited data about the benefit of usZDV added to sdNVP to prevent mother-to-child transmission.

METHODS

We performed a double-blind, randomized, placebo-controlled trial to determine whether usZDV combined with sdNVP improved neonatal outcome, compared with sdNVP alone. Mothers were randomized to 1 of 2 treatment groups. Mothers in the usZDV/sdNVP group received a loading dose of zidovudine (600 mg administered orally) and continued to receive 300-mg doses of zidovudine orally every 3 h while in labor, and their infants received zidovudine at a dosage of 2 mg per kg of body weight 4 times per day orally for 72 h. Mothers and infants in the sdNVP group received zidovudine placebo dosed in the same manner. All mothers also received nevirapine at a dosage of 200 mg orally while in labor, and all infants received nevirapine 2 mg per kg of body weight orally within 72 h of delivery.

RESULTS

The study was stopped on the basis of futility, because interim data showed that, at present trends, superiority would not be demonstrated. Results at 6 weeks of age were available for 609 infants. The primary end point of HIV RNA positivity or death occurred in 21.8% of infants in the usZDV/sdNVP arm and 23.6% of the infants in the sdNVP arm.

CONCLUSION

usZDV, when added to a standard 2-dose regimen of sdNVP, did not demonstrate a clinically important decrease in the combined end point of mother-to-child transmission or infant death. High rates of adverse maternal and infant outcome in both study arms suggest that improved approaches are necessary.

Impact of HIV-1 pol diversity on drug resistance and its clinical implications

PURPOSE OF REVIEW

HIV knowledge is based on subtype B, common in resource-rich settings, whereas globally non-B subtypes predominate. Inter-subtype pol diversity encompasses multiple genotypic differences among HIV variants, the consequence of which is unknown. This review summarizes publications from the past year relevant to the impact of HIV diversity on drug resistance evolution and its potential clinical implications.

RECENT FINDINGS

The benefit of antiretroviral therapy in non-B infected patients is ongoing, though subtype heterogeneity in rates of disease progression is observed. Pol inter-subtype diversity is high, and known subtype B drug resistance mutations occur in non-B subtypes. New mutations and subtype-specific mutation rates are identified, however, unexplained drug susceptibilities are seen, and additional insight is offered on structural pathogenic mechanisms of resistance in non-B subtypes. These differences may affect genotypic interpretation and our ability to apply drug resistance to patient care.

SUMMARY

Current evidence suggests good treatment response and comparable drug resistance evolution in HIV-1 B and non-B infected patients, with increasingly emerging differences. Impact of inter-subtype diversity on drug susceptibility and on evolution of drug resistance should continue to be a major research focus to increase our understanding and ability to improve global patient care.

HIV/AIDS epidemiology, pathogenesis, prevention, and treatment

The HIV-1 pandemic is a complex mix of diverse epidemics within and between countries and regions of the world, and is undoubtedly the defining public-health crisis of our time. Research has deepened our understanding of how the virus replicates, manipulates, and hides in an infected person. Although our understanding of pathogenesis and transmission dynamics has become more nuanced and prevention options have expanded, a cure or protective vaccine remains elusive. Antiretroviral treatment has transformed AIDS from an inevitably fatal condition to a chronic, manageable disease in some settings. This transformation has yet to be realised in those parts of the world that continue to bear a disproportionate burden of new HIV-1 infections and are most affected by increasing morbidity and mortality. This Seminar provides an update on epidemiology, pathogenesis, treatment, and prevention interventions pertinent to HIV-1.

Controversies in the use of nevirapine for prevention of mother-to-child transmission of HIV

The use of nevirapine to prevent mother-to-child transmission of HIV has been controversial. Claims of high rates of toxicity have not been confirmed in clinical trials or extensive programme experience of use of the regimen. Whilst single-dose nevirapine can reduce transmission rates to approximately 10-15%, this can be halved by the addition of single-dose nevirapine to short-course regimens of zidovudine. The selection of resistant virus is reported in 20-50% of mothers and 50% of infants following one dose of nevirapine, although the impact of this on future treatment options is not fully understood. An increased risk of severe hepatotoxicity has been reported with long-term nevirapine-containing triple-therapy treatment regimens in women with CD4+ counts > 250 cells/mm3.

(C2) Saliva, breast milk, and mucosal fluids in HIV transmission

The oral environment has received various amounts of attention in association with HIV infection and pathogenesis. Since HIV infection occurs through mucosal tissue, oral factors-including tissue, fluids, and compartments-are of interest in furthering our understanding of the diagnosis, infectivity, transmission, and pathogenesis of disease. This report reviews: (1) HIV testing and diagnoses with oral fluids; (2) post-natal acquisition of HIV in association with breast-feeding from HIV-positive mothers; and (3) oral sex and HIV transmission. In the first, we examine how oral fluids are used to detect HIV infection and review current consensus on the role of salivary molecules as markers for immunosuppression. Second, lactation-associated HIV acquisition is reviewed, with special consideration of emerging issues associated with the impact of anti-retroviral therapies. Last, we consider current data on the risk of HIV infection in association with oral sex. Investigation of these diverse topics has a common goal: understanding how HIV presents in the oral environment, with an aim to rapid and accessible HIV diagnosis, and improved prevention and treatment of infection.

Strategies to prevent mother-to-child transmission of HIV

PURPOSE OF REVIEW

This review describes recent advances in the prevention of mother-to-child transmission, focusing on the use of antiretroviral treatment strategies in pregnancy, and discusses the emergence of viral resistance following the use of nevirapine to prevent mother-to-child transmission.

RECENT FINDINGS

Mother-to-child transmission has been dramatically reduced in developed countries by the use of antiretroviral treatment and avoidance of breastfeeding. Highly active antiretroviral therapy use in pregnancy is recommended for women who require ongoing treatment, and, where available, is also very effective in reducing mother-to-child transmission in women with higher CD4 counts. The addition of a maternal and infant nevirapine dose to antenatal zidovudine can reduce transmission to below 5%, approximately half the transmission rate that can be achieved by single-dose nevirapine alone. The emergence of resistant virus following nevirapine use is a concern, occurring in up to 60% of mothers and 50% of infants following a single dose. Addition of zidovudine and lamivudine for 4-7 days postpartum can reduce the risk of resistance to 10%.

SUMMARY

There is broad consensus on an approach to preventing mother-to-child transmission, which provides antiretroviral treatment in pregnancy and beyond to those women who need it, and an effective prophylactic regimen for those who do not yet need treatment, These regimens include highly active antiretroviral therapy, where available, a zidovudine-plus-nevirapine regimen in other settings, or nevirapine alone where this is all that is possible. More work is needed on the impact of nevirapine resistance and on reducing breast-milk transmission.

Antiretroviral Therapy for Prevention of Mother-to-Child HIV Transmission

Administration of potent antiretroviral combination therapy in the second and third trimester of pregnancy and during delivery, and for 6 weeks postpartum to the infant, may reduce HIV transmission from the mother to the child to <2% in formula-fed infants. In resource-constrained settings where women have limited access to antenatal care, use of shorter and more practical regimens, including nucleoside reverse transcriptase inhibitors (NRTIs) and/or non-NRTIs (NNRTIs) commenced later in pregnancy, has demonstrated efficacies ranging from 18% to 70% in breast- and bottle-fed populations. Because shorter interventions include regimens such as single-dose nevirapine or zidovudine monotherapy, which do not provide maximal suppression of viral replication, emergence of resistant mutations in mother and infant occurs frequently, primarily after exposure to drugs with low genetic barriers (i.e. those requiring only one genotypic mutation to develop resistance), such as nevirapine. Different studies have reported nevirapine resistance rates ranging from 25% to 69% in mothers receiving single-dose nevirapine alone. Because NNRTI-based combinations of antiretroviral agents are recommended as first-line therapy in countries where single-dose nevirapine is the main option for preventing mother-to-child transmission of HIV, concerns have been raised as to whether single-dose nevirapine prophylaxis can compromise the efficacy of subsequent NNRTI-based antiretroviral therapy regimens. However, although some studies have shown that nevirapine exposure may impact on short-term virological outcome, the clinical relevance of nevirapine resistance remains unclear, especially in women who start treatment >6 months after delivery or in those who are not severely immunocompromised. Furthermore, studies have shown that adding short-course (up to 7 days) zidovudine or zidovudine/lamivudine prophylaxis after delivery may dramatically reduce the occurrence of nevirapine resistance in both mothers and infants. Until data are available that allow a better understanding of the relevance of antiretroviral drug resistance acquired as a result of mother-to-child HIV transmission prophylaxis, women and children who have previously received single- dose nevirapine as part of a mother-to-child transmission prevention strategy should be considered eligible for NNRTI-based regimens and should not be denied access to antiretroviral therapy.