Selection and Persistence of Viral Resistance in HIV-Infected Children After Exposure to Single-Dose Nevirapine

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.

Nevirapine resistance in women and infants after first versus repeated use of single-dose nevirapine for prevention of HIV-1 vertical transmission

Single-dose (SD) nevirapine (NVP) significantly reduces mother-to-child transmission of human immunodeficiency virus (HIV). We analyzed NVP resistance after receipt of SD NVP in 57 previously SD NVP-naive women, in 34 SD NVP-experienced women, and in 17 HIV-infected infants. The proportion of women infected with variants with resistance mutations, the types of mutations detected, and the frequency and level of K103N were similar in the two groups of women at 6 weeks and 6 months post partum. NVP resistance was detected in a similar proportion of infants born to SD NVP-naive versus SD NVP-experienced women. Repeated use of SD NVP to prevent HIV transmission does not appear to influence NVP resistance.

Early virological suppression with three-class antiretroviral therapy in HIV-infected African infants

OBJECTIVES

Infants infected with HIV-1 perinatally despite single-dose nevirapine progress rapidly. Data on treatment outcome in sub-Saharan African infants exposed to single-dose nevirapine are urgently required. This feasibility study addresses efficacy of infant antiretroviral therapy in this setting.

METHODS

HIV-infected infants in Durban, South Africa, received randomized immediate or deferred (when CD4 cell count reached <20%) four-drug antiretroviral therapy (zidovudine/lamivudine/nelfinavir/nevirapine). Genotyping for non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance was undertaken pre-antiretroviral therapy. Monthly follow-up to 1-year post-antiretroviral therapy included viral load, CD4 cell count and verbal/measured adherence monitoring.

RESULTS

All 63 infants were exposed to single-dose nevirapine. Twenty-one out of 51 (39%) infants with baseline genotyping results had NNRTI resistance (most frequently Y181C; 20%). Forty-three infants were randomized to immediate antiretroviral therapy (ART): three withdrew pre-antiretroviral therapy; 36 out of 40 completed 1-year of ART. Twenty infants received deferred ART: 17 reached CD4 cell counts less than 20% (median d99) and 13 out of 17 started antiretroviral therapy in year 1. Verbal and measured adherence was 99% and 95%, respectively. One-year post-ART, 49 out of 49 (100%) infants had a viral load less than 400 copies/ml; 46 out of 49 (94%) had viral load less than 50 copies/ml. Ten infants (20%) required second-line ART due to virological failure or tuberculosis treatment, therefore 39 out of 49 (80%) achieved viral load less than 400 copies/ml by intention-to-treat. Time to viral load less than 50 copies/ml correlated with maternal CD4 cell count (r = -0.42; P = 0.005) and infant pre-ART viral load (r = 0.64; P < 0.001). NNRTI mutations had no significant effect on virological suppression. Infants starting immediate compared with deferred ART had fewer illness episodes (P = 0.003), but no significant difference in virological suppression.

CONCLUSION

Excellent adherence and virological suppression are achievable in infants, despite high-frequency NNRTI mutations and rapid disease progression. Infants remain relatively neglected in roll-out programmes and ART provision must be expanded.

Study of the genotypic resistant pattern in HIV-infected women and children from rural west Cameroon

The distribution of antiretroviral (ARV) therapy resistance mutations among HIV-1 strains was evaluated in 39 postpartum women, one pregnant woman, and 12 HIV-positive babies (seven newborns and five children) living in rural west Cameroon. Thirty-five women and all newborns received a single dose of nevirapine (NVP) to prevent mother-to-child transmission of HIV-1; two women were ARV treated and three were ARV naive. Of the 52 viral strains examined, three were subtype B, 45 were classified into eight HIV-1 non-B subtypes, and four remained unclassifiable. Sequence analysis for genotypic drug resistance in the reverse transcriptase (RT) gene showed the presence of mutations associated with nonnucleoside RT inhibitor resistance in 20% of the samples from NVP-treated women and in 57% of those from treated newborns. Mutations associated with nucleoside RT inhibitors (M184V in one case and V118I in four cases) were found in five samples, despite being derived from ARV-naive patients. As expected, a greater frequency of mutations was found in the protease gene region. Of the sequences analyzed, 79% harbored five to seven specific mutations. The secondary mutations showed the typical protease inhibitor resistance-associated pattern for non-subtype B viruses, M36I being the predominant mutation (92.5% in women, 100% in babies). Other mutations frequently detected were K20I, L63P, H69K, and I13V. These findings confirm that resistance mutations can be detected in ARV-naive patients infected with non-B subtypes and emphasize an urgent need for studies assessing the impact of these mutations on the efficacy of subsequent ARV therapy and on the appearance of drug-resistant strains.

Comparison of LigAmp and an ASPCR assay for detection and quantification of K103N-containing HIV variants

We compared the ability of the LigAmp assay and an ASPCR assay to detect and quantify K103N-containing HIV variants in samples from 63 women who received single-dose nevirapine in a clinical trial. Samples were first analyzed with the ViroSeq HIV Genotyping system, and ViroSeq PCR products were used as templates for the LigAmp and ASPCR assays. A cutoff of 0.5% K103N for detection of K103N was used for both assays. Results for the percentage K103N were similar for the two assays (R(2) = 0.92). Forty-six samples (73.0%) were positive for K103N by both assays and 13 samples (20.6%) were negative by both assays. Four samples (6.3%) were positive by ASPCR only. No samples were positive by LigAmp only. Eight discordant samples were analyzed in more detail. Sequence polymorphisms near oligonucleotide binding sites provided a possible explanation for the discordance in four of eight samples. The percentage K103N was also determined by analyzing 40 HIV clones from each of these eight samples, using a combined amplification/sequencing method (AmpliSeq). The percentage K103N determined by clonal analysis was consistent with the LigAmp result for five of eight samples, and was consistent with the ASPCR result for three of eight samples. Among 320 clones analyzed, we identified eight different codons at position 103 (mean = 3.8 codons/sample), which encoded six different amino acids, illustrating the extensive genetic diversity in HIV. Further studies are needed to compare performance of assays for detection and quantification of HIV drug resistance mutations in clinical samples.

Prophylactic antiretroviral regimens for prevention of mother-to-child transmission of HIV in resource-limited settings

PURPOSE OF REVIEW

With the large international mobilization against HIV/AIDS, more HIV-infected people in resource-limited settings have access to antiretroviral therapy, including pregnant women. The relevance of simplified prophylactic antiretroviral regimens for the prevention of mother-to-child transmission of HIV may become questionable due to their lower efficacy and their higher risk of inducing viral resistance than fully suppressive antiretroviral therapy.

RECENT FINDINGS

Field implementation of current recommendations, impact of prophylactic regimens on subsequent antiretroviral therapy response and possible new indications of antiretroviral therapy in pregnant women will be reviewed in this paper.

SUMMARY

Prophylactic antiretroviral prevention of mother-to-child transmission regimens reached only 10% of the HIV-infected pregnant women in 2006, who were usually offered single-dose nevirapine only. The operational links between antenatal care and antiretroviral therapy programmes can now be documented and demonstrate good results in terms of safety and efficacy. The negative impact of single-dose nevirapine exposure on subsequent first-line antiretroviral therapy appears worse for mothers with advanced HIV disease at the time of delivery and short interval before antiretroviral therapy initiation. Strengthening the links between antenatal care and antiretroviral therapy programmes is critical for antiretroviral therapy-eligible HIV-infected pregnant women in terms of prevention of mother-to-child transmission and subsequent antiretroviral therapy response. The breastfeeding period could be a new indication for antiretroviral therapy in this population.

Characterization of HIV type 1 reverse transcriptase mutations in infants infected by mothers who received peripartum nevirapine prophylaxis in Jos, Nigeria

This study was carried out to characterize HIV-1 reverse transcriptase (RT) mutations in vertically infected infants in Jos, Nigeria. DNA was extracted from peripheral blood mononuclear cells of 102 infants, aged 0 to 6 months, born to HIV-1-infected mothers who had received peripartum single-dose nevirapine prophylaxis. PCR-based diagnosis revealed that 14 infants (13.7%) were infected with HIV-1. Phylogenetic analyses of RT revealed wide viral diversity, with CRF02_AG, subtype G, subsubtype A3, CRF06_cpx, and a subtype D recombinant present in the population. Four of 13 (31%) infants had NNRTI resistance mutations--V179I (2 infants), Y181C, and V179E. Intriguingly, subtype G sequences did not have NNRTI mutations but rather carried a Q207N mutation, which may undergo negative selection under drug pressure. Our data suggest wide diversity for vertically transmitted HIV-1 viruses in Nigeria and highlight the potential significance of transmitting rare mutations in subtype G.

Journey to the Motherland: Assessing Capacity for the Prevention of HIV Mother-to-Child Transmission in South Africa

Strategies to prevent mother-to-child transmission of HIV have successfully affected pediatric HIV infections in many developed countries, but not as dramatically in developing countries. This article presents the findings and perspectives of a team of public health nurses who visited and assessed capacity of selected antenatal clinics across South Africa to successfully implement and evaluate HIV prevention of maternal-to-child transmission programs conducted for a private nongovernmental organization. Through development and implementation of a needs-assessment tool, the clinics were systematically assessed by observation and interviews. Consistently, three additional areas of concern, other than HIV, were reported by the people interviewed. These concerns were hunger, poverty, and the need for home-based care.

Single-dose tenofovir and emtricitabine for reduction of viral resistance to non-nucleoside reverse transcriptase inhibitor drugs in women given intrapartum nevirapine for perinatal HIV prevention: an open-label randomised trial

BACKGROUND

Intrapartum and neonatal single-dose nevirapine are essential components of perinatal HIV prevention in resource-constrained settings, but can induce resistance to other non-nucleoside reverse transcriptase inhibitor drugs. We aimed to investigate whether this complication would be reduced with a single peripartum intervention of tenofovir and emtricitabine.

METHODS

We randomly assigned 400 HIV-infected pregnant women who sought care at two public-sector primary health facilities in Lusaka, Zambia. One was excluded, 200 were assigned to receive a single oral dose of 300 mg tenofovir disoproxil fumarate with 200 mg emtricitabine under direct observation, and 199 to receive no study drug. Short-course zidovudine and intrapartum nevirapine were offered to all HIV-infected women, according to the local standard of care. Women who met national criteria for antiretroviral therapy were referred for care and not enrolled. Our primary study outcome was resistance to non-nucleoside reverse transcriptase inhibitors at 6 weeks after delivery. We used standard population sequencing to determine HIV genotypes. Analysis was per protocol. This study is registered with ClinicalTrials.gov, number NCT00204308.

FINDINGS

Of the 200 women who were randomly assigned to the intervention, 14 were lost to follow-up or withdrew from the study, two did not take study drug according to protocol, and one specimen was lost; 23 of 199 controls were lost to follow-up or withdrew from the study, and three specimens were lost. Women given the intervention were 53% less likely than controls to have a mutation that conferred resistance to non-nucleoside reverse transcriptase inhibitors at 6 weeks after delivery (20/173 [12%] vs 41/166 [25%]; risk ratio [RR] 0.47, 95% CI 0.29-0.76). We noted postpartum anaemia, the most common serious adverse event in mothers, in four women in each group. 20 of 198 (10%) infants in the intervention group and 23 of 199 (12%) controls had a serious adverse event, mostly due to septicaemia (n=22) or pneumonia (n=8); these events did not differ between groups, and none were judged to be caused by the study intervention.

INTERPRETATION

A single dose of tenofovir and emtricitabine at delivery reduced resistance to non-nucleoside reverse transcriptase inhibitors at 6 weeks after delivery by half; therefore this treatment should be considered as an adjuvant to intrapartum nevirapine.

Treatment of pediatric HIV infection

HIV-infected children require a peculiar management when compared to infected adults. Antiretroviral therapy has been quite well adapted to children, but new studies are needed to answer many unsolved questions, such as when to start therapy in asymptomatic infected children. Recently, several guidelines have been updated. In this review, we compare these recommendations together with the latest studies concerning the treatment of HIV in children. A triple-drug combination therapy based either on nonnucleoside reverse transcriptase inhibitors or protease inhibitors is the recommended initial therapy. After treatment failure, a second-line therapy should be based on switching between these two regimens. Antiretroviral therapy should be managed by an expert in pediatric and adolescent HIV infection. The importance of children's adherence to therapy is a crucial point, particularly in adolescents.

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.

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.

Sensitive oligonucleotide ligation assay for low-level detection of nevirapine resistance mutations in human immunodeficiency virus type 1 quasispecies

This study has adapted the oligonucleotide ligation assay (OLA) to probe for low-level nevirapine (NVP) resistance mutations K103N and Y181C in the human immunodeficiency virus type 1 (HIV-1) population of infected mother-infant pairs from Uganda. When NVP is used to prevent perinatal transmission, NVP-resistant HIV-1 clones may be rapidly selected due to a low barrier for mutation and a relatively high level of fitness (compared to that of other drug-resistant HIV-1 clones). Monitoring for even a low frequency of NVP resistance mutations may help predict the success of subsequent treatment or warrant the use of another regimen to prevent transmission in a subsequent pregnancy. The standard OLA was optimized by using nonstandard bases in oligonucleotides to allow promiscuous base pairing and accommodate significant HIV-1 heterogeneity. Radiolabeled as opposed to fluorescently tagged oligonucleotides increased the sensitivity, whereas alteration of the template, oligonucleotides, salt, and thermostable DNA ligase concentrations increased the specificity for the detection of minority codons. This modified OLA is now capable of detecting mutants with the K103N or the Y181C mutation present in an HIV-1 population at a frequency of approximately 0.4% and is at least 10- to 30-fold more sensitive than the original protocol. A cohort of 19 Ugandan mothers who received NVP treatment perinatally were sampled 6 weeks postdelivery. Ten of 19 HIV-1 DNA samples extracted from peripheral blood mononuclear cells had a detectable K103N (0.5 to 44%) or Y181C (0.8 to 92.5%) mutation, but only one plasma HIV-1 RNA sample had a viral population with the Y181C mutation. These findings suggest that OLA is a robust, sensitive, and specific method for the detection of low-frequency drug resistance mutations in an intrapatient HIV-1 population.

Biological mechanisms of vertical human immunodeficiency virus (HIV-1) transmission

In the absence of interventions, 30-45% of exposed infants acquire human immunodeficiency virus type 1 (HIV-1) through mother-to-child transmission. It remains unclear why some infants become infected while others do not, despite significant exposure to HIV-1 in utero, during delivery and while breastfeeding. Here we discuss the correlates of vertical transmission with an emphasis on factors that increase maternal HIV-1 levels, either systemically or locally in genital secretions and breast milk. Immune responses may influence maternal viral load, and data suggest that maternal neutralising antibodies reduce infection rates. In addition, infants may be capable of mounting HIV-specific cellular immune responses. We propose that both humoral and cellular responses are necessary to reduce infection because cell-free as well as cell-associated virus appears to play a role in vertical transmission. These distinct forms of the virus may be targeted most effectively by different components of the immune system. We also discuss the use of antiretrovirals to reduce transmission, focusing on the mechanisms of action of regimens currently used in developing country settings. We conclude that prevention relies not only on reducing maternal HIV-1 levels within blood, genital tract and breast milk, but also on pre- and/or post-exposure prophylaxis to the infant. However, HIV-1 has the capacity to mutate under drug pressure and rapidly acquires mutations conferring antiretroviral resistance. This review concludes with data on persistence of low-level resistance after delivery as well as recent guidelines for maternal and infant regimens designed to limit resistance.