Alarmin S100A9 restricts retroviral infection by limiting reverse transcription in human dendritic cells.

Dendritic cells (DC) subsets, like Langerhans cells (LC), are immune cells involved in pathogen sensing. They express specific antimicrobial cellular factors that are able to restrict infection and limit further pathogen transmission. Here, we identify the alarmin S100A9 as a novel intracellular antiretroviral factor expressed in human monocyte-derived and skin-derived LC. The intracellular expression of S100A9 is decreased upon LC maturation and inversely correlates with enhanced susceptibility to HIV-1 infection of LC. Furthermore, silencing of S100A9 in primary human LC relieves HIV-1 restriction while ectopic expression of S100A9 in various cell lines promotes intrinsic resistance to both HIV-1 and MLV infection by acting on reverse transcription. Mechanistically, the intracellular expression of S100A9 alters viral capsid uncoating and reverse transcription. S100A9 also shows potent inhibitory effect against HIV-1 and MMLV reverse transcriptase (RTase) activity in vitro in a divalent cation-dependent manner. Our findings uncover an unexpected intracellular function of the human alarmin S100A9 in regulating antiretroviral immunity in Langerhans cells.

Optimised prevention of postnatal HIV transmission in Zambia and Burkina Faso (PROMISE-EPI): a phase 3, open-label, randomised controlled trial.

BACKGROUND: Transmission through breastfeeding accounts for more than half of the unacceptably high number of new paediatric HIV infections worldwide. We hypothesised that, in addition to maternal antiretroviral therapy (ART), extended postnatal prophylaxis with lamivudine, guided by point-of-care assays for maternal viral load, could reduce postnatal transmission. METHODS: We did a phase 3, open-label, randomised controlled trial at four health-care facilities in Zambia and four health-care facilities in Burkina Faso. Mothers with HIV and their breastfed infants without HIV attending the second visit of the Expanded Programme of Immunisation (EPI-2; infant age 6-8 weeks) were randomly assigned 1:1 to intervention or control groups. In the intervention group, maternal viral load was measured using Xpert HIV viral load assay at EPI-2 and at 6 months, with results provided immediately. Infants whose mothers had a viral load of 1000 copies per mL or higher were started on lamivudine syrup twice per day for 12 months or 1 month after breastfeeding discontinuation. The control group followed national guidelines for prevention of postnatal transmission of HIV. The primary outcome assessed by modified intention to treat was infant HIV infection at age 12 months, with HIV DNA point-of-care testing at 6 months and at 12 months. This trial is registered with ClinicalTrials.gov (NCT03870438). FINDINGS: Between Dec 12, 2019 and Sept 30, 2021, 34 054 mothers were screened for HIV. Among them, 1506 mothers with HIV and their infants without HIV, including 1342 mother and infant pairs from Zambia and 164 from Burkina Faso, were eligible and randomly assigned 1:1 to the intervention (n=753) or control group (n=753). At baseline, the median age of the mothers was 30·6 years (IQR 26·0-34·7), 1480 (98·4%) of 1504 were receiving ART, and 169 (11·5%) of 1466 had a viral load ≥1000 copies/mL. There was one case of HIV transmission in the intervention group and six in the control group, resulting in a transmission incidence of 0·19 per 100 person-years (95% CI 0·005-1·04) in the intervention group and 1·16 per 100 person-years (0·43-2·53) in the control group, which did not reach statistical significance (p=0·066). HIV-free survival and serious adverse events were similar in both groups. INTERPRETATION: Our intervention, initiated at EPI-2 and based on extended single-drug postnatal prophylaxis guided by point-of-care maternal viral load could be an important strategy for paediatric HIV elimination. FUNDING: The EDCTP2 programme with the support of the UK Department of Health & Social Care.

Utility of self-report antiretroviral adherence for predicting HIV viral load among persons who inject drugs in Hai Phong Vietnam: assessing differences by methamphetamine use.

ABSTRACTIn resource-limited settings, alternatives to HIV viral load testing may be necessary to monitor the health of people living with HIV. We assessed the utility of self-report antiretroviral therapy (ART) to screen for HIV viral load among persons who inject drugs in Hai Phong Vietnam, and consider differences by recent methamphetamine use. From 2016 to 2018 we recruited PWID through cross sectional surveys and collected self-report ART adherence and HIV viral load to estimate sensitivity, specificity, positive and negative predictive values (PPV, NPV) and likelihood ratios (LR+, LR-) for self-reported ART adherence as a screening test for HIV viral load. We used three HIV viral load thresholds: < 1000, 500 and 250 copies/mL; laboratory-confirmed HIV viral load was the gold standard. Among 792 PWID recruited, PPV remained above 90% regardless of recent methamphetamine use with slightly higher PPV among those not reporting recent methamphetamine use. The results remained consistent across all three HIV viral load thresholds. Our findings suggest that when HIV viral load testing is not possible, self-reported ART adherence may inform decisions about how to prioritize HIV viral load testing among PWID. The high PPV values suggest self-reported high ART adherence indicates likely HIV viral suppression, irrespective of methamphetamine use.

Gender Differences in HIV, HCV risk and Prevention Needs Among People who Inject drug in Vietnam.

We examined gender differences among people who inject drug (PWID) in Hai Phong, Vietnam in term of blood-borne infections, risk behaviors, and access to care. Using respondent-driven-sampling surveys, we recruited 3146 PWID from 2016 to 2018. Inclusion criteria included a positive urine test for heroin and recent injection marks. There were 155 female PWID (4,9%), including 82 at RDS-2016, 32 at RDS-2017 and 38 at RDS-2018. The age mean was 36.3 ± 7.2 years. The majority of female PWID had less than high school education (90.9%) and were unemployed (51.3%). There was no difference in the proportion of HIV and HCV positive by gender. However, women had several significant differences in risk behaviors than men in multivariable logistic regression. Being a woman was independently associated with being unemployed, being a sex worker, having unstable housing, having uses drugs for less than 5 years, more use of methamphetamine, having a partner who ever injected drugs, and less access to methadone treatment. Interventions targeting female PWID are needed, possibly through community organizations and peer educators.

Eliminating postnatal HIV transmission in high incidence areas: need for complementary biomedical interventions.

The rate of mother-to-child transmission (MTCT) of HIV from breastfeeding is increasing relative to other causes of MTCT. Early effective preconception and antenatal antiretroviral therapy (ART) reduces intrauterine and intrapartum MTCT, whereas maternal post-partum HIV acquisition, untreated maternal HIV, and suboptimal postnatal maternal ART adherence increase the risk of MTCT through breastfeeding. Although the absolute number of cases of MTCT acquired through breastfeeding is decreasing, the rate of decrease is less than the decrease in intrauterine and intrapartum MTCT. Unless current strategies are universally applied, they might not be sufficient to eliminate MTCT due to breastfeeding. Urgent action is needed to evaluate and implement additional preventive biomedical strategies in high HIV prevalence and incidence settings to eliminate MTCT from breastfeeding. Preventive strategies include: pre-exposure prophylaxis in breastfeeding women who have an increased risk of acquiring HIV; postnatal reinforcement strategies, such as maternal retesting for HIV, maternal care reinforcement, and prophylaxis in infants exposed to HIV via breastmilk; and active (vaccine) or passive immunoprophylaxis with long-acting broadly neutralising antibodies.

Prevention of mother-to-child transmission of HIV at the second immunization visit: a cross-sectional study, Burkina Faso.

Objective: To evaluate the performance of the cascade of activities for prevention of mother-to-child transmission (PMTCT) of human immunodeficiency virus (HIV) at the second immunization visit in Burkina Faso. Methods: In a cross-sectional study, we recruited mothers attending the second immunization visit for their infant in 20 health centres of Bobo-Dioulasso city, Burkina Faso over 12 months (2019-2020). We administered a short questionnaire to 14 176 mothers and performed HIV serological tests on mothers who had not been tested in the last 3 months. All mothers were asked about their attendance for antenatal care and HIV rapid testing. HIV-infected mothers were also asked about the timing of their HIV diagnosis, antiretroviral therapy, pre-exposure prophylaxis initiation at birth and infant diagnosis of HIV. Findings: Of 14 136 respondents, 13 738 (97.2%) had at least one HIV serological test in their lifetime. Of 13 078 mothers who were never tested or were HIV-negative, 12 454 (95.2%) were tested during or after their last pregnancy. Among HIV-infected mothers already aware of their status, 110/111 (99.1%) women were on antiretroviral therapy. Among HIV-exposed infants, 84/101 (83.2%) babies received 6 weeks of antiretroviral prophylaxis at birth and 58/110 (52.7%) had a blood sample collected for early infant diagnosis. Only two mothers received their child's test results at the time of the second immunization visit. Four mothers were newly diagnosed as HIV-positive during the study. Conclusion: Collecting data at the second immunization visit, a visit rarely missed by mothers, could be useful for identifying gaps in the PMTCT cascade in settings where mothers are difficult to reach, such as in low-income countries with intermediate or low HIV prevalence.

Clinical and Biological Factors Associated With Early Epstein-Barr Virus Infection in Human Immunodeficiency Virus-Exposed Uninfected Infants in Eastern Uganda.

BACKGROUND: Immune control of Epstein-Barr virus (EBV) infection is impaired in individuals with HIV. We explored maternal factors associated with EBV acquisition in HIV-exposed uninfected (HEU) infants and the relationship between EBV infection and serious adverse events (SAEs) during the first year of life. METHODS: 201 HEU infants from Uganda enrolled in the ANRS 12174 trial were tested for antiviral capsid antigen (anti-VCA) antibodies at week 50. Date of infection was estimated by testing EBV DNA at weeks 1, 6, 14, 26, 38, and 50 postpartum on dried blood spots. RESULTS: Eighty-seven (43%) infants tested positive for anti-VCA IgG at week 50. Among the 59 infants positive for EBV DNA, 25% were infected within the first 26 weeks. Almost half (12%) were infected before week 14. Shedding of EBV in breast milk was associated with EBV DNA in maternal plasma (P = .009), HIV RNA detection (P = .039), and lower CD4 count (P = .001) and correlated with plasma EBV DNA levels (P = .002). EBV infant infection at week 50 was associated with shedding of EBV in breast milk (P = .009) and young maternal age (P = .029). Occurrence of a clinical SAE, including malaria and pneumonia, was associated with higher levels of EBV DNA in infants (P = .010). CONCLUSIONS: By assessing EBV infection in HEU infants we observed that infection during the first year is determined by HIV and EBV maternal factors and that EBV DNA levels were higher among infants with clinical SAEs. CLINICAL TRIALS REGISTRATION: NCT00640263.

Revisiting Koch's postulate to determine the plausibility of viral transmission by human milk.

As breastfeeding is of utmost importance for child development and survival, identifying whether breast milk is a route of transmission for human viruses is critical. Based on the principle of Koch's postulate, we propose an analytical framework to determine the plausibility of viral transmission by breast milk. This framework is based on five criteria: viral infection in children receiving breast milk from infected mothers; the presence of virus, viral antigen, or viral genome in the breast milk of infected mothers; the evidence for the virus in breast milk being infectious; the attempts to rule out other transmission modalities; and the reproduction of viral transmission by oral inoculation in an animal model. We searched for evidence in published reports to determine whether the 5 criteria are fulfilled for 16 human viruses that are suspected to be transmissible by breast milk. We considered breast milk transmission is proven if all 5 criteria are fulfilled, as probable if 4 of the 5 criteria are met, as possible if 3 of the 5 criteria are fulfilled, and as unlikely if less than 3 criteria are met. Only five viruses have proven transmission through breast milk: human T-cell lymphotropic virus 1, human immunodeficiency virus, human cytomegalovirus, dengue virus, and Zika virus. The other 11 viruses fulfilled some but not all criteria and were categorized accordingly. Our framework analysis is useful for guiding public health recommendations and for identifying knowledge gaps amenable to original experiments.

Lopinavir-Ritonavir Impairs Adrenal Function in Infants.

BACKGROUND: Perinatal treatment with lopinavir boosted by ritonavir (LPV/r) is associated with steroidogenic abnormalities. Long-term effects in infants have not been studied. METHODS: Adrenal-hormone profiles were compared at weeks 6 and 26 between human immunodeficiency virus (HIV)-1-exposed but uninfected infants randomly assigned at 7 days of life to prophylaxis with LPV/r or lamivudine (3TC) to prevent transmission during breastfeeding. LPV/r in vitro effect on steroidogenesis was assessed in H295R cells. RESULTS: At week 6, 159 frozen plasma samples from Burkina Faso and South Africa were assessed (LPV/r group: n = 92; 3TC group: n = 67) and at week 26, 95 samples from Burkina Faso (LPV/r group: n = 47; 3TC group: n = 48). At week 6, LPV/r-treated infants had a higher median dehydroepiandrosterone (DHEA) level than infants from the 3TC arm: 3.91 versus 1.48 ng/mL (P < .001). Higher DHEA levels (>5 ng/mL) at week 6 were associated with higher 17-OH-pregnenolone (7.78 vs 3.71 ng/mL, P = .0004) and lower testosterone (0.05 vs 1.34 ng/mL, P = .009) levels in LPV/r-exposed children. There was a significant correlation between the DHEA and LPV/r AUC levels (ρ = 0.40, P = .019) and Ctrough (ρ = 0.40, P = .017). At week 26, DHEA levels remained higher in the LPV/r arm: 0.45 versus 0.13 ng/mL (P = .002). Lopinavir, but not ritonavir, inhibited CYP17A1 and CYP21A2 activity in H295R cells. CONCLUSIONS: Lopinavir was associated with dose-dependent adrenal dysfunction in infants. The impact of long-term exposure and potential clinical consequences require evaluation. CLINICAL TRIALS REGISTRATION: NCT00640263.

MAIT cells, TCR γδ+ cells and ILCs cells in human breast milk and blood from HIV infected and uninfected women.

BACKGROUND: Human breast milk cells remain poorly characterized for the presence of unconventional T lymphocytes and innate lymphoid cells (ILCs). METHODS: Early breast milk was collected from eight HIV-uninfected and 11 HIV-infected women 3-12 days after delivery. Mucosal-associated invariant T cells (MAIT cells), TCR γδ cells, and innate lymphoid cells (ILCs) were analyzed in breast milk and paired blood samples. RESULTS: CD161+/TRAV1-2 + MAIT cells were detected in breast milk, accounting for a median (IQR) of 0.08% (0.06-0.16) and 0.17% (0.16-0.31) of CD45+ breast milk cells in HIV-uninfected and HIV-infected women, respectively. A selective compartmentalization of γδ T lymphocytes was observed in breast milk. Median (IQR) frequency of γδ T lymphocytes was 8.95% (8.64-12.14) among breast milk lymphocyte cells compared to 2.54% (1.81-4.10) in blood (P = 0.03) in HIV-uninfected women, and 7.26% (4.22-10.54) in breast milk versus 3.31% (2.54-3.80) in blood (P = 0.004) from HIV-infected women. The proportion of group 1 ILC (ILC1) among total ILCs was higher in breast milk compared to blood in HIV-uninfected women (P = 0.03) and HIV-infected women (P = 0.001). The frequency of ILC2 among total ILCs tends to be lower in breast milk compared to blood in HIV-uninfected women (P = 0.06) and HIV-infected women (P = 0.03). CONCLUSION: Unconventional T cells and ILCs that may be involved in both the protection against infection of the lactating mammary gland and maturation of infant's gut and microbiomes account for a detectable fraction of breast milk cells.

Hepatitis B and C virus seroprevalence, Burkina Faso: a cross-sectional study.

OBJECTIVE: To estimate population-wide hepatitis B and C seroprevalence using dried blood spot samples acquired for human immunodeficiency virus (HIV) surveillance as part of the 2010-2011 Demographic and Health Survey in Burkina Faso. METHODS: We used the database acquired during the multistage, clustered, population-based survey, in which 15 377 participants completed questionnaires and provided dried blood spot samples for HIV testing. We extracted sociodemographic and geographic data including age, sex, ethnicity, education, wealth, marital status and region for each participant. We performed hepatitis B and C assays on 14 886 HIV-negative samples between March to October 2015, and calculated weighted percentages of hepatitis seroprevalence for each variable. FINDINGS: We estimated seroprevalence as 9.1% (95% confidence interval, CI: 8.5-9.7) for the hepatitis B surface antigen and 3.6% (95% CI: 3.3-3.8) for hepatitis C virus antibodies, classifying Burkina Faso as highly endemic for hepatitis B and low-intermediate for hepatitis C. The seroprevalence of hepatitis was higher in men than in women, and varied significantly for both with age, education, ethnicity and region. Extremely high HCV-Ab seroprevalence (13.2%; 95% CI: 10.6-15.7) was identified in the Sud-Ouest region, in particular within the youngest age group (15-20 years), indicating an ongoing epidemic. CONCLUSION: Our population-representative hepatitis seroprevalence estimates in Burkina Faso advocate for the inclusion of hepatitis serological tests and risk factor questionnaire items in future surveys, the results of which are crucial for the development of appropriate health policies and infection control programmes.

Breastmilk cell trafficking induces microchimerism-mediated immune system maturation in the infant.

Initiating breastfeeding within the first hour of life confers an important benefit in terms of child mortality and severe morbidity. Intestinal permeability to ingested macromolecules and immunoglobulins is limited to the first days of human life. These exchanges cease in the very early post-partum period but may increase beyond the neonatal period in response to local inflammation or introduction of a weaning food. From animal- and limited human-based observations, compelling evidence points out to breastmilk cells also trafficking from mother to infant mucosal tissues and participating to the maternal microchimerism. The precise nature of breastmilk cells that are involved is presently not known but likely includes progenitor/stem cells-representing up to 6% of breastmilk cells-with possible contribution of mature immune cells. Stem cell microchimerism may induce tolerance to non-inherited maternal antigens (NIMAs), breastfeeding generating regulatory T cells (Treg ) that suppress antimaternal immunity. Therefore, in complement to pregnancy-induced microchimerism, breastfeeding-induced microchimerism may be pivotal in infant immune development, intestinal tissue repair/growth and protection against infectious diseases. As a continuum of the gestational period, the neonatal gut may be considered as a temporary, but important developmental extension of the role played by the placenta during intrauterine life; breastmilk playing the role of maternal blood by delivering maternal soluble factors (macromolecules, Ig, cytokines) and immunologically active milk cells. A better understanding of breastfeeding-induced maternal microchimerism would provide further evidence in support of public health messages that reinforce the importance of early initiation of breastfeeding.

Risk Behaviors for HIV and HCV Infection Among People Who Inject Drugs in Hai Phong, Viet Nam, 2014.

We examined the potential for HIV and hepatitis C (HCV) transmission across persons who inject drugs (PWID), men-who-have-sex-with-men (MSM) and female commercial sex workers (CSW) PWID and the potential for sexual transmission of HIV from PWID to the general population in Hai Phong, Viet Nam. Using respondent driven and convenience sampling we recruited 603 participants in 2014. All participants used heroin; 24% used non-injected methamphetamine. HIV prevalence was 25%; HCV prevalence was 67%. HIV infection was associated with HCV prevalence and both infections were associated with length of injecting career. Reported injecting risk behaviors were low; unsafe sexual behavior was high among MSM-PWID and CSW-PWID. There is strong possibility of sexual transmission to primary partners facilitated by methamphetamine use. We would suggest future HIV prevention programs utilize multiple interventions including "treatment as prevention" to potential sexual transmission of HIV among MSM and CSW-PWID and from PWID to the general population.

Integrated respondent-driven sampling and peer support for persons who inject drugs in Haiphong, Vietnam: a case study with implications for interventions.

Combined prevention for HIV among persons who inject drugs (PWID) has led to greatly reduced HIV transmission among PWID in many high-income settings, but these successes have not yet been replicated in resource-limited settings. Haiphong, Vietnam experienced a large HIV epidemic among PWID, with 68% prevalence in 2006. Haiphong has implemented needle/syringe programs, methadone maintenance treatment (MMT), and anti-retroviral treatment (ART), but there is an urgent need to identify high-risk PWID and link them to services. We examined integration of respondent-driven sampling (RDS) and strong peer support groups as a mechanism for identifying high-risk PWID and linking them to services. The peer support staff performed the key tasks that required building and maintaining trust with the participants, including recruiting the RDS seeds, greeting and registering participants at the research site, taking electronic copies of participant fingerprints (to prevent multiple participation in the study), and conducting urinalyses. A 6-month cohort study with 250 participants followed the RDS cross-sectional study. The peer support staff maintained contact with these participants, tracking them if they missed appointments, and providing assistance in accessing methadone and ART. The RDS recruitment was quite rapid, with 603 participants recruited in three weeks. HIV prevalence was 25%, Hepatitis C (HCV) prevalence 67%, and participants reported an average of 2.7 heroin injections per day. Retention in the cohort study was high, with 86% of participants re-interviewed at 6-month follow-up. Assistance in accessing services led to half of the participants in need of methadone enrolled in methadone clinics, and half of HIV-positive participants in need of ART enrolled in HIV clinics by the 6-month follow-up. This study suggests that integrating large-scale RDS and strong peer support may provide a method for rapidly linking high-risk PWID to combined prevention and care, and greatly reducing HIV transmission among PWID in resource-limited settings.

Evaluation of the prevention of mother-to-child transmission of HIV programs at the second immunization visit in Burkina Faso and Zambia.

OBJECTIVE: Our study aimed to assess the PMTCT indicators in Burkina Faso and Zambia using a patient-orientated innovative strategy based on the second visit in the Expanded Program on Immunization (EPI-2) visit at 6-8 weeks. DESIGN: This was a cross sectional study. METHODS: We assessed women attending EPI-2 at primary healthcare facilities in Burkina Faso and Zambia with their children about their exposure to PMTCT interventions. For women living with HIV (WLHIV), viral load was measured and their children were tested for HIV DNA using point of care devices. RESULTS: Overall, 25 093 were enrolled from Burkina Faso and 8961 women from Zambia. Almost, all women attended at least one antenatal care visit. Among those aware of their HIV-positive status, 95.8 and 99.2% were on antiretroviral therapy (ART) in Burkina Faso and Zambia, respectively. Among WLHIV on ART, 75 and 79.2% achieved a viral load suppression (viral load <1000 copies/ml) in Burkina Faso and Zambia, respectively. Infant postnatal prophylaxis was administered from birth until EPI-2 to 60.9 and 89.7% of HIV-exposed children in Burkina Faso and Zambia, respectively. In Burkina Faso, only 60 of 192 (31.3%) of HIV-exposed children were sampled at day 42 for early infant diagnosis (EID) and 3 (1.6%) received a result by EPI-2. In Zambia, these figures were 879 of 1465 (64.0%) and 9.9% (145/1465), respectively for HIV-exposed children sampled at birth. CONCLUSION: This evaluation strategy at EPI-2 visit could strengthen program monitoring and help identifying gaps to be addressed on the last mile towards elimination of MTCT of HIV.

Quantification of Female Chimeric Cells in the Tonsils of Male Children and Their Determinants.

The factors influencing mother-to-child cell trafficking and persistence over children's lives have yet to be established. The quantification of maternal microchimerism was previously reported through HLA-based approaches, which introduced bias regarding the tolerogenic environment. We aimed to identify cells of maternal origin irrespective of the HLA repertoire and to ascertain the determinants of microchimeric cells. This case-control study enrolled 40 male infants attending pediatric surgery from January 2022 to October 2022. Female cells were quantified in infants' tonsil tissue by using cytogenetic fluorescent in situ hybridization (FISH) coupled with optimized automated microscopy. Out of the 40 infants, half (47.4%) had been breastfed for more than one month, a quarter for less a month, and 10 children (26.3%) were never breastfed. XX cells were observed in male tonsils in two-thirds of participants at a median density of 5 cells per 100,000 cells. In univariate analyses, child age was negatively associated with a high female cell density. In exploratory multivariate analyses, previous breastfeeding is a likely determinant of the persistence of these cells in the host, as well as the rank among siblings. Part of the benefit of breastmilk for child health may therefore be driven by breastfeeding-related microchimerism.

Facilitators and barriers to infant post-natal HIV prophylaxis, a qualitative sub-study of the PROMISE-EPI trial in Lusaka, Zambia.

Background: Infant post-natal prophylaxis (PNP) is used to prevent HIV transmission through breastfeeding. The WHO edited recommendations but so far there is no consensus on the duration of prophylaxis and the type of drug used depends on national guidelines. In Zambia, the national recommendations include a three-drug prophylaxis, composed of a dispersible combined tablet of zidovudine (AZT) and lamivudine (3TC) and an oral suspension of nevirapine (NVP) for 12 weeks or until the mother's viral load is <1,000 cp/mL. The PROMISE-EPI study, modified the PNP regimen to lamivudine only, initiated at 6 weeks and continued until 12 months to all HIV exposed uninfected infants of virally unsuppressed mothers. Our aim in this analysis was to identify barriers and facilitators to this extended PNP, the keystone toward an effective prevention. Methods: Individual interviews and focus group discussion (FGD) were conducted with PROMISE-EPI participants who had received prophylaxis for their children from the national program up to 6 weeks and then lamivudine oral solution in PROMISE-EPI study. Health care providers and PROMISE-EPI staff were also interviewed. Sessions were recorded, transcribed verbatim and translated from local languages into English. An initial code-book was designed and then adapted on the basis of the emerging themes, to allow a descriptive thematic analysis. Results: More barriers to PNP adherence were identified with triple drug prophylaxis than with lamivudine. These barriers were related to the formulation and bitter taste of AZT/3TC tablets. The ready to use formulation and sweet taste of lamivudine syrup were appreciated by mothers. Extended PNP proposed in the PROMISE-EPI study was globally well accepted and strategies were found to increase adherence. Adherence to lamivudine appeared to be better than the mothers' adherence to their own antiretroviral therapy. Conclusion: Accompanying mothers living with HIV and giving them the choice of the PNP to prevent transmission via breastfeeding (type of PNP regimen and extended PNP in non-adherent mothers), may be one of the keys to reducing the burden of pediatric HIV acquisition in low and middle income countries.