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Intrapartum single-dose-nevirapine along with third trimester maternal and infant zidovudine are essential components of programs to prevent mother-to-child HIV transmission in resource-limited settings. The persistence of nevirapine in the plasma for three weeks postpartum risks selection of resistance mutations to non-nucleoside reverse transcriptase inhibitors (NNRTI). We hypothesized that a one-month zidovudine-plus-didanosine course initiated at the same time as single-dose nevirapine would prevent the selection of nevirapine resistance mutations.
PHPT-4 HIV-infected pregnant women with CD4 counts above 250 cells/mm3 received antepartum zidovudine from the third trimester until delivery, single-dose nevirapine during labor and one-month zidovudine-plus-didanosine postpartum. These women were matched on baseline viral load (VL), CD4 count and duration of antepartum zidovudine to women who received single-dose nevirapine in the PHPT-2 trial (controls). Consensus sequencing and the more sensitive oligonucleotide ligation assay (OLA) were performed on samples drawn at 7–10, 37–45 and 120 days postpartum (if VL>500 copies/mL) to detect K103N/Y181C/G190A mutations.
The 222 PHPT-4 subjects did not differ from their matched controls in baseline characteristics except for age. Combined groups median CD4 count was 421 cells/mm3 [IQR: 322–549], VL 3.45 log10 copies/mL [2.79–4.00] and ZDV prophylaxis 10.4 weeks [9.1–11.4]. Using consensus sequencing, major NNRTI resistance mutations were detected postpartum in 0% of PHPT-4 subjects versus 10.4% of PHPT-2 controls. OLA detected resistance in 1.8% of PHPT-4 subjects versus 18.9% controls. Major NNRTI resistance mutations were detected by either method in 1.8% of PHPT-4 subjects versus 20.7% in controls (p<10−10).
One-month postpartum zidovudine-plus-didanosine prevented the selection of vast majority NNRTI resistance mutations.
Single-dose nevirapine given to HIV-infected women at onset of labor and newborns, in addition to antenatal zidovudine from the third trimester of pregnancy reduces perinatal HIV transmission to approximately two percent in formula-fed infants , a rate similar to that achieved using Highly Active Antiretroviral Therapy (HAART) [2–4]. This strategy is recommended for the prevention of mother-to-child transmission of HIV (PMTCT) by the World Health Organization (WHO) for women who do not require immediate treatment for their own health in resource-constrained settings . Where antepartum zidovudine is not feasible or when HIV infection is diagnosed late during labor, single-dose nevirapine remains essential to diminish intrapartum transmission.
Unfortunately, HIV resistance mutations to non-nucleoside reverse transcriptase inhibitors (NNRTIs) can be selected within weeks after single-dose nevirapine administration [6–10] and have been associated with a decrease in the virologic efficacy of subsequent NNRTI-based HAART regimens when women initiate therapy for their own health [8, 11, 12]. Although factors associated with selection of these mutations are not fully understood, it is postulated to occur as long as nevirapine persists in the plasma  in the presence of viral replication. We hypothesized that a one-month post-partum course of zidovudine-plus-didanosine following exposure to single-dose nevirapine would prevent the selection of resistance mutations by suppressing viral replication. This combination was chosen for its relative simplicity, likely good tolerance, low cost, high genetic barrier to resistance, and lack of interference with hepatitis B virus replication (infection in about 10% of the Thai population ). Such a regimen, if proven effective, could be applied widely in a public health context.
PHPT-4 was a multicenter, open-label trial to assess the incidence of NNRTI-resistance mutations in women who received a one-month postpartum zidovudine-plus-didanosine course in addition to antepartum zidovudine from 28 weeks plus single dose nevirapine at onset of labor (ClinicalTrials.gov: NCT00142337), compared to matched, historical controls from PHPT-2  who received the same antepartum regimen (zidovudine and single dose nevirapine) but no postpartum antiretroviral course (ClinicalTrials.gov: NCT00398684). In both trials, infants received zidovudine and were not breastfed. A placebo-controlled study design was not considered for ethical reasons. Indeed, in 2004 when the trial was planned, we had already reported that exposure to single-dose nevirapine decreased the efficacy of subsequent nevirapine-containing HAART regimens . Furthermore, preliminary results of a clinical trial in Africa showed that a 4 or 7 days postpartum course of zidovudine-plus-lamivudine could diminish, but not eliminate, the selection of nevirapine resistance mutations . The availability of stored samples collected during the PHPT-2 clinical trial conducted at the same sites provided satisfactory controls.
Pregnant women participating in the Thai Ministry of Public Health’s PMTCT program at 37 hospitals in Thailand between January 2005 and September 2005 were offered enrollment in the PHPT-4 study. Inclusion criteria were: age over 18 years, provision of written consent and the following laboratory values within 21 days of enrollment: hemoglobin >8.0 g/dL; absolute neutrophils >750 cells/mm3; alanine aminotransferase <5 times the upper limit of normal; creatinine <1.5 mg/dL. Exclusion criteria were: CD4 count <250 cells/mm3 or medical need for HAART, and maternal or fetal condition or concomitant treatment contraindicating zidovudine or nevirapine.
PHPT-4 study subjects included in the analysis had received single-dose nevirapine and attended at least the seven-day postpartum visit. They were individually matched on viral load, CD4 count at baseline, and duration of antepartum zidovudine to women enrolled between January 2001 and February 2003 in the PHPT-2 trial  and followed for up to 120 days postpartum.
PHPT-4 subjects and PHPT-2 controls received 300 mg zidovudine bid starting at 28 weeks’ gestation or as soon as possible thereafter and 300 mg every three hours plus 200 mg single-dose nevirapine during labor. Their infants received one week postnatal 2 mg/kg zidovudine qid plus 6 mg single-dose nevirapine at 48–72 hours of life. Premature infants received reduced zidovudine dosing and if less than 2,500g, 2 mg/kg of nevirapine.
As opposed to PHPT-2 controls, PHPT-4 subjects received one dose of didanosine enteric-coated capsule 400 mg during labor. Zidovudine 300 mg bid and didanosine 400 mg once daily (250 mg once daily if less than 60 Kg) were continued for one month postpartum. Following a report of Grade-4 postpartum anemia in July 2005, the postpartum zidovudine dose was reduced to 200 mg bid, based on a study  showing this dosage provided adequate zidovudine levels in Thai women who are generally small. None of the PHPT-2 control women received a postpartum antiretroviral treatment.
Eligibility and entry criteria, antepartum evaluations in PHPT-4 and PHPT-2 were identical. After delivery, PHPT-2 women had a physical exam and virological evaluations at the 7–10, 37–40, and 120-day visits. PHPT-4 women had more extensive postpartum evaluations with standard hematology and chemistry. Adherence was assessed at each visit by pill count. At the end of the study, women were referred to an internist for HIV care.
Plasma HIV RNA was measured following the Cobas Amplicor HIV-1 Monitor RNA version 1.5 standard and, if below standard threshold, the ultra-sensitive protocol (Roche Molecular Systems Inc., Branchburg, USA). Resistance mutations to NRTIs and NNRTIs were assayed on all available postpartum samples with a viral load >500 copies/mL, and, if mutations were detected, baseline samples were also assayed. Population sequencing was performed using the HIV-1 ViroSeq Genotyping System, version 2.6 (Celera Diagnostics, Alameda, USA) and interpretation based on the spring 2008 International AIDS Society USA Drug mutation tables (http://www.iasusa.org/resistance_mutations).
ViroSeq amplified products were tested using the Oligonucleotide Ligation Assay (OLA), a sensitive assay which can detect specific resistance mutations present in more than 5% of the viral population [18, 19]. The K103N, G190A, and Y181C NNRTI resistance mutations were tested using oligonucleotides designed for the CRF01_AE subtype prevalent in Thailand. Plasma samples with a viral load <500 copies/mL were considered negative for NNRTI mutations. Samples with non-amplifiable HIV polymerase gene or indeterminate OLA results were classified as missing.
We calculated that 219 evaluable subjects (244 enrolled subjects taking into account 10% non evaluable), would provide adequate power (0.05 one-sided type I error, 0.8 power) to detect a decreased incidence of resistance mutations from 20% in matched PHPT-2 controls to 10% in PHPT-4 women receiving post-partum zidovudine-didanosine.
Baseline maternal and other study characteristics including the incidence of NNRTI resistance mutations detected at all follow-up time points by both methods were compared between groups using Kruskal-Wallis, chi-square, and Fisher’s tests. A logistic regression analysis was used in PHPT-2 controls to test the association between postpartum NNRTI resistance mutations and baseline viral loads and CD4 cell count (categorized in terciles). Analyses were conducted using Stata Statistical Package (StataCorp LP, Texas, USA). P-values were two-sided without adjustment for multiple testing.
The Thai Ministry of Public Health and Chiang Mai University Faculty of Medical Associated Sciences Ethics Committees approved the protocol including amendments.
Of 302 HIV-positive eligible women, 257 were enrolled, 234 followed through delivery, 229 received single-dose nevirapine, and 222 attended the seven-day postpartum visit. These 222 women were matched with PHPT-2 control women (Figure 1: Subject disposition chart).
The baseline and delivery characteristics of the 222 PHPT-4 subjects and their PHPT-2 controls were similar, except for age (Table 1 provides baseline and delivery characteristics separately in the two groups). Combined groups median CD4 count was 421 cells/mm3 [IQR: 322–549], VL 3.45 log10 copies/mL [2.79–4.00] and antepartum ZDV duration was 10.4 weeks [9.1–11.4], hemoglobin levels at enrollment and delivery were 11.1 g/dL [10.4–11.9] and 11.6 g/dL [10.8–12.5], respectively. PHPT-4 subjects and PHPT-2 controls received intrapartum nevirapine. Two PHPT-4 and eight PHPT-2 women received two doses due to false or prolonged labor. In PHPT-4, seven women received antepartum zidovudine and single dose nevirapine in a previous pregnancy, and one woman received antepartum zidovudine only. In PHPT-2, seven women previously received antepartum zidovudine.
In PHPT-4, 117 (53%) women received the initial postpartum zidovudine dosing (300 mg bid). One woman took no postpartum zidovudine-plus-didanosine, and one for less than 2 weeks. One woman with prolonged labor initiated zidovudine-plus-didanosine after her first nevirapine dose; another who had false labor received zidovudine-plus-didanosine after her second nevirapine dose (five days after the first). Twenty-two women (10%) missed more than one dose per week of either drug.
The proportions of subjects with HIV RNA viral load below 500 copies/mL at 7–10 days, 37–45 days and 120 days postpartum were: 85%, 54% and 24% in PHPT-4, and 78%, 39%, and 45% in PHPT-2, respectively (Table 2). In PHPT-4 subjects, median viral load was lowest at 7–10 days, and returned to baseline levels at 4-month postpartum.
No new major NNRTI resistance mutations---i.e. mutations which alone confer high-level resistance to any NNRTI --- were detected using consensus sequencing at anytime postpartum in PHPT-4 subjects. In contrast, one or more major NNRTI resistance mutations were detected in 23 PHPT-2 controls (10.4%).
Ninety one percent of sequenced viruses were of the CRF01_AE subtype. The incidence of mutations detected at each postpartum period is given in Table 3 and Figure 2, and individual subjects’ results shown in Table 4.
Using OLA, the K103N, G190A or Y181C mutations were detected postpartum in four (1.8%) PHPT-4 subjects versus 42 (18.9%) controls. Among PHPT-4 women with resistance mutations, one had received single dose nevirapine during a previous pregnancy. Two sequencing results were not confirmed by OLA on the same sample (Table 4). Baseline samples were tested in 93% of subjects with postpartum mutations and no mutations were detected. Combining the results of both assays, new postpartum resistance mutations were found in 1.8% of the PHPT-4 subjects versus 20.7% of PHPT-2 controls (p<10−10 ), a 91% reduction in the selection of NNRTI resistance mutations.
In an analysis restricted to PHPT-2 control women, after adjusting for baseline CD4 cell count, only high baseline viral load was associated with postpartum NNRTI resistance mutations detected by either method (p <0.001).
Five PHPT-4 subjects and eight PHPT-2 controls had minor NNRTI mutations in postpartum samples (V179D, K101E, V106I, or V90I). These mutations were also detected in 8 of the 10 baseline samples that could be amplified.
One PHPT-4 subject and two PHPT-2 controls already had NRTI resistance mutations detected at baseline (two T69N, one M41L). After a median antepartum zidovudine duration of 10.4 weeks in both groups and an additional 4 weeks postpartum zidovudine-plus-didanosine in PHPT-4, new NRTI resistance mutations were detected by consensus sequencing in five PHPT-4 subjects (2.3%; four K70R and one D67N+K70R) and two PHPT-2 controls (0.9%; one D67N, one K70R) (Table 4).
The proportion of subjects who experienced a serious adverse event between delivery and four months postpartum was similar in PHPT-4 subjects and controls, at 4.5% and 3.1%, respectively. In PHPT-4 women, one postpartum hemorrhage with grade-4 anemia (hemoglobin 6.3g/dL), one stillbirth, four infections, one grade-4 lipase elevation (10 × Upper Limit of Normal (ULN)), one grade-4 anemia (hemoglobin 6.5g/dL), and one gastritis were reported. In PHPT-2 women, three postpartum hemorrhage, three infections, and one alanine transferase grade-4 elevation (21 × ULN) were reported. Ten days after delivery, mild rash was reported in 2.7% PHPT-4 subjects and 2.3% controls. Also, grade-1 or grade-2 elevated alanine aminotransferase were reported in 4.4% of PHPT-4 women and 3.6% of controls.
In PHPT-4 subjects, median hemoglobin was 11.7 g/dL [10.9–12.5] at one month postpartum (11.6 g/dL (10.9–12.5) on the initial 300 mg bid zidovudine dosing, and 11.9 g/dL (10.9–12.5) on 200 mg (p = 0.20). Two PHPT-4 women experienced a grade-4 and two a grade-3 anemia. Anemia was not reported in control women, but because hemoglobin levels were not prospectively measured, sub-clinical anemia may have occurred.
Although HIV transmission was not an outcome of this study, it was measured. Among 176 PHPT-4 infants with DNA-PCR data, four were infected (2.3%, 0.5% to 6.0%), and none in the PHPT-2 group (0%-1.6%). None of the women previously exposed to antepartum zidovudine and single dose nevirapine transmitted HIV to her infants.
Following single-dose nevirapine during labor, one month of zidovudine-plus-didanosine postpartum in women with no indication for therapy for their own health, virtually eliminated the selection of HIV NNRTI resistance mutations. Only low concentrations of virus quasispecies with resistance mutations, expected to decay rapidly could be detected by OLA; they were no longer detectable at four months. During the 4-month postpartum follow-up, combining the results of both assays, major resistance mutations to NNRTIs were detected in 1.8% of the mothers who received postpartum zidovudine-didanosine versus 20.7% of the control women (p<10−10), a 91% reduction in the selection of NNRTI resistance mutations. The one-month postpartum regimen appeared safe, well tolerated, and easy to adhere to.
PHPT-4 subjects and controls matched on CD4 count, antepartum zidovudine duration and plasma viral load did not differ for any baseline characteristics other than age. Surprisingly the 4-month postpartum viral loads were lower in PHPT-2 controls than in PHPT-4 subjects and lower than at baseline. Indeed, in PHPT-2 controls, postpartum viral loads were measured on samples stored frozen for several years, while baseline samples were tested on a real time basis. Therefore, the prevalence of NNRTI resistance mutations in the control group may have been underestimated, and the difference between the two groups may be greater than that reported here. The fact that in PHPT-4, 85% of women had undetectable viral load at 7–10 days and 54% at 37–45 days post partum, reflects the antiretroviral activity of zidovudine-plus-didanosine combined with nevirapine which remains at clinically significant levels for up to 20 days after single dose administration .
A meta-analysis estimated the incidence of post-exposure nevirapine resistance mutations detected by consensus sequencing at 35.7%, with a lower incidence in women who received antepartum antiretrovirals . As expected, the incidence of resistance mutations in PHPT-2 controls was lower, because women with CD4 below 250 cells/mm3 and likely higher viral loads, were not eligible. Differences across studies may also be partly explained by the virus subtypes prevalent in each population. In Africa, subtype-C viruses and, to a lesser extent, subtype-D have more often than subtype-A, been associated with the selection of resistance mutations after single-dose nevirapine [21, 22]. Although no direct comparison can be made with subtypes prevalent in Thailand, the incidence of resistance with subtype-C appears to be higher than with subtypes E/B. For example, in Zambia where subtype-C predominates, the prevalence of NNRTI resistance mutations at 6-week postpartum in a similar population (women not eligible for HAART who received antepartum ZDV) was 25% using population sequencing (44% with OLA) , compared with 6.4% (13.2% with OLA) in PHPT-2 participants.
In an attempt to limit the selection of nevirapine resistance mutations, several post-exposure antiretroviral regimens have been evaluated. In a South-African randomized trial  the incidence of resistance mutations detectable by population sequencing at 2 and 6 weeks postpartum was reduced from 57% to 13% or 9% with a 4- or 7-day postpartum course of zidovudine-plus-lamivudine, respectively. In Cote d’Ivoire, zidovudine-plus-lamivudine from 32 weeks gestation to 3 days postpartum reduced the incidence of resistance mutations detected at 4 weeks from 33% in historical controls to 1% . However, lamivudine resistance mutations, associated with subsequent failure of lamivudine containing regimens, were reported in 8% of women . In Zambia, women not eligible for HAART who received short course zidovudine plus intrapartum nevirapine, received either single-dose tenofovir-plus-emtricitabine (Truvada®) during labor or no intervention . At 6 weeks postpartum, Truvada® reduced NNRTI resistance mutations detected by population sequencing from 25% to 12%, and by OLA from 45% to 20%. Finally, in the TEmAA ANRS12109 study , no resistance mutations were detected by population sequencing at 4 weeks postpartum in 37 women with over 200 CD4 cells/mm3 who received antepartum zidovudine, intrapartum single-dose nevirapine together with double-dose Truvada®, continued for one week once daily. The duration of antiretroviral regimen in this study was longer than regimens evaluated elsewhere but appeared much more efficacious in preventing resistance mutations.
Genotypes perceived to have “minor” contributions to resistance to second generation of NNRTI, etravirine, were detected in several consecutive postpartum samples as well as before nevirapine exposure. These mutations are known polymorphisms in subtype CRF01_AE.
The one month zidovudine-plus-didanosine regimen evaluated in this study appeared safe. It bears minimal risk of selecting NRTI resistance mutations and can be offered to women with HBV co-infection as these drugs do not interfere with HBV replication. HBV infection affects about 10% of the south-east Asia population, and hepatitis B virus flare with a risk of clinical acute hepatitis have been reported following discontinuation of treatments containing lamivudine, emtricitabine or tenofovir [28–30].
This one month regimen of zidovudine-plus-didanosine maintained viral replication at low levels for the duration which nevirapine may be present at significant levels (Table 2) . This confirms that inhibiting viral replication during nevirapine exposure is an effective approach to prevent the selection of resistance mutations. Preliminary results from another study indicate that a more potent postpartum regimen (boosted lopinavir, zidovudine and didanosine) for a shorter period of time may have a similar efficacy .
The HIV transmission rate in PHPT-4 subjects was 2.2% compared to 0% among PHPT-2 controls. The absence of perinatal transmissions in the PHPT-2 control group may have been due to chance, since the overall transmission rate of transmission in the PHPT-2 group of women with CD4 count above 250 cells/mm3 from which control women was randomly selected, was 1.4% (95% CI, 0.6%–2.9%)(data not shown).
Highly active antiretroviral therapy is increasingly used during pregnancy for the prevention of mother to child transmission of HIV regardless of the woman’s immune status. However, for the many women who are diagnosed late in pregnancy or at delivery, intrapartum nevirapine will continue to be an essential component of the prevention of perinatal HIV. Therefore, interventions to eliminate post-exposure selection of nevirapine resistance are critical to safeguard a highly efficacious intervention for the prevention of mother to child transmission, while preserving the mother’s future therapeutic options.
Clinical trial sites: Program for HIV Prevention and Treatment (Thailand) Site Principal Investigators (numbers of women enrolled in each hospital are given in parentheses): Hat Yai (20): T. Jarupanich, K. Veerapradist; Samutsakhon (18): T. Sukhumanant, S. Phumratpratin; Chiangrai Prachanukroh (17): R. Hansudewechakul, J. Achalapong, S. Yanpaisan; Samutprakarn (17): P. Sabsanong, M. Hongsawinitkul; Chonburi ( 16 ): N. Chotivanich, C. Tantiyawarong; Health Promotion Region 6 Khon Kaen (14): N. Winiyakul, W. Sinchai; Rayong (12): S. Lorenz (Weerawatgoompa), C. Pinyovityakul; Chacheongsao (12): A. Kanjanasing, V. Pengvanich; Khon Kaen (12): J. Ratanakosol, V. Jarupoonphol; Phayao Provincial (10): J. Hemvuttiphan, G. Halue, S. Attawibool; Bhumibol Adulyadej (10): K. Kengsakul, Y. Vonglertvidhya; Buddhachinaraj (10): W. Wannapira, W. Boonyawatana; Health Promotion Region 10 Chiang Mai (9): V. Sittipiyasakul; Somdej Pranangchao Sirikit (9): W. Pornkitprasarn, D. Pratoompetch; Lampang (9): P. Liampongsabuddhi, P. Prathipvanich, C. Sirinirundr; Prapokklao (7): P. Yuthavisuthi, D. Sinthuvanich; Pranangklao (5): S. Pipatnakulchai, P. Ekchariyawat; Nong Khai (5): N. P. Ruttana-Aroongorn, T. Wichatrong; Nakhonpathom (5): V. Chalermpolprapa, P. Hirunchote; Mahasarakam (5): P. Sitsirat, W. Supanchaimat; Ratchaburi (5): T. Chonladarat, P. Bunjongjit; Health Promotion Region 1 Bangkok (4): S. Sirinontakan, C. Kommongkol; Phaholpolphayuhasena (4): Y. Srivarasat, T. Buddhaboriwan; Nakornping (3): V. Gomuthbutra, K Khunsukmengrai; Lamphun (2): W. Matanasarawut, C. Kulkolakan; Mae Sai (2): S. Kunkongkapan; Srinagarind (2): C. Sakondhavat, P. Kosalaraksa, S. Kraitrakul; Kranuan Crown Prince (2): R. Thongdej, A. Rattanaparinya; Roi-et (2): W. Atthakorn, W. Worngsatthanaphong; Chiang Kham (1): C. Putiyanun, T. Hanwong; Phan (1): S. Jungpichanvanich, T. Changchit.
Sites monitoring: P. Sukrakanchana, S. Chalermpantmetagul, C. Kanabkaew, R. Peongjakta, J. Chaiwan, Y. S. Thammajitsagul, R. Wongchai, N. Kruenual, N. Krapunpongsakul, W. Pongchaisit, T. Thimakam, S. Sittilers,, R. Wongsrisai, J. Wallapachai, J Thonglo, C. Chanrin, S. Jinasa, J Khanmali, P. Chart, K. Kaewsom, J. Wallapachai, J. Khanmali, C. Chanrin; Laboratory: P. Tungyai, J. Kamkorn, W. Boonprasit, P. Tankaew, P. Pongpunyayuen, P. Mongkolwat, S. Kaewmoon, S. Yawichai, L Laomanit, N. Wangsaeng, S. Surajinda, T. Lerksuthirat, W. Danpaiboon, W. Palee, S. Kunkeaw, Y. Taworn, S. Rincome, D. Sean-eye; PHPT Data center: L. Decker, S. Tanasri, R. Jitharidkul, N. Fournet,: A. Maleesatharn,, S. Chailert, R. Seubmongkolchai, A. Wongja, K. Yoddee, M. Nuchniyom, K. Chaokasem, P. Chailert, K. Suebmongkolchai, S. Tansenee, A. Seubmongkolchai, C. Chimplee, K. Saopang, L. Karbkam, P. Chusut, P. Onnoy, S. Aumtong, S. Suekrasae, T. Chattaviriya, B. Thongpunchang, T. Chitkawin; Administrative support: N. Chaiboonruang, P. Pirom, Y. Thita, T. Sriwised, T. Intaboonmar; S. Phromsongsil, S. Jaisook, J. Krasaesuk; Tracking & Supplies: K. Than-in-at, M. Inta; Drug distribution center: D. Chinwong, Chalermpong Sanjoom,
We thank all the mothers and staff from the participating sites. We are indebted to Ingrid Beck, MS, for transferring the OLA technique to the PHPT laboratory in Chiang Mai and ensuring quality assurance of reagents and assays. We thank Stephen Hart for ensuring the quality assurance of the sequence data at the Frontier Science Foundation.
We are also grateful for the advice and assistance from the Thai Ministry of Public Health: Office of the Permanent Secretary, Department of Health, Department of Communicable Diseases Control, and Provincial Hospitals Division and especially, M. Teeratantikanont, P. Amornwichet, V. Chokevivat, T. Siraprapasiri, S. Thanprasertsuk, N. Voramongkol, S. Pattarakulwanich, N. Aungkasuwapala, and from Chiang Mai University: W. Sirirungsi, P. Leechanachai, A. Haesungcharern, and all members of the hospital teams, and the women and children who participated in this study.
The Global Fund to fight AIDS, Tuberculosis and Malaria Thailand Grant Round 1 sub recipient PR-A-N-008. National Institutes of Health (5 R01 HD 33326, PHPT-2), USA; Agence Nationale de Recherches sur le Sida (ANRS 12-32, PHPT-2); Ministry of Public Health, Thailand; Institut de Recherche pour le Developpement, France; Institut National d’Etudes Demographiques, France; Department of Technical and Economic Cooperation, Thailand; Boehringer Ingelheim and GlaxoSmithKline (zidovudine and nevirapine or placebo in PHPT-2). Adaptation of the oligonucleotide ligation assays for this study was supported by NIH awards R01 AI058723 (LMF) and UO1 AI068632 (LMF for a Virology Specialty Laboratory of IMPAACT). The following reagent was obtained through the AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: OLA Kit, NNRTIs (Cat #7644) from Drs. Ingrid Beck and Lisa Frenkel.
Potential conflict of interest: All authors declare no conflict of interest.
Presented in part: 16th Conference on Retroviruses and Opportunistic Infections, Montreal, Canada, February 2009 (late breaker abstract 95bLB).