HIV-1 mother-to-child transmission and drug resistance among Brazilian pregnant women with high access to diagnosis and prophylactic measures

Background: A high-coverage public health prenatal program (70,000 women/year) from central western Brazil/Goias State has represented a unique opportunity for the early diagnosis of HIV-1 and implementation of strategies to prevent mother-to-child transmission (MTCT). Objectives: To investigate MTCT among a prospective cohort of HIV-1 infected mothers/exposed infants. Study design: 142 mothers/their 149 infants (2008-2010) were investigated regarding maternal viral load, CD4(+) cell counts, HIV-1 pol sequences; infants' HIV-1 RNA tests (30/120days), sequential anti-HIV-1/2 serology. HIV-1 subtypes were assigned by REGA. Transmitted drug resistance was identified by the Calibrated Population Resistance tool, secondary resistance by Stanford HIV-1 Drug Resistance/International AIDS Society databases. Results: Mothers (median age = 24 years; 25/142 adolescents) were diagnosed during prenatal care (2008-2010) or previously (1994-2007). Recent cases were younger, mostly asymptomatic. Undetectable viremia and MTCT prophylaxis predominated in formerly diagnosed mothers. Recent cases had higher subtype C prevalence. One naive patient had transmitted resistance; ten antiretroviral-experienced patients had secondary resistance: 6 from MTCT prophylaxis, 4 under HAART. Late disclosure of diagnosis, vaginal delivery, breastfeeding, lack of oral zidovudine were observed in the three MTCT cases (3/149; 2.01%). Two of three infected infants harbored subtype C; infected infants/mothers did not have drug resistance mutations. Two of the transmitting-mothers had viremia <1000 copies/ml. Among exposed-uninfected infants the median time to seroreversion was 12 months. Conclusions: In this study delayed disclosure of diagnosis, partial/no preventive measures, drug resistance among asymptomatic women under prophylaxis and MTCT in low viremic mothers raise concerns. The expansion of subtype C infection corroborates surveillance of HIV-1 diversity in this region. (C) 2012 Elsevier B. V. All rights reserved.