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.
Resistant mutations were selected in half of the infants exposed to sd-NVP, but fewer were detected over time and, unlike the case in their mothers, Y181C dominated initially and persists. Transient resistance mutations may have a negative impact on highly active antiretroviral therapy in infants and children.
The emergence of HIV drug resistance is a major obstacle to effective antiretroviral (ARV) treatments. This study examined the drug resistance profiles among South African patients virologically failing ARV therapies between 2000 and 2003, prior to the introduction of a national treatment program. Samples were obtained from 65 HIV-1 subtype C-infected patients (39 children and 26 adults) who had received at least two nucleoside reverse transcriptase inhibitors (NRTIs) and either a nonnucleoside reverse transcriptase inhibitor (NNRTI) or protease inhibitor (PI). Resistance assays were performed using the HIV-1 ViroSeq Genotyping System and mutations were defined according to the Stanford Sequence Resistance Database. Ninety-one percent of patients harbored resistance mutations; the most frequent NRTI mutations were M184V/I (37%), D67N (32%), T215Y/F (25%), K70R (21%), M41L (20%), K219Q/E (14%), and K65R (14%), reflecting the frequent use of lamuvidine and zidovudine. K103N (25%), V106M (20%), and G190A (17%) were found among patients failing nevirapine- or efavirenz-containing regimens. Of the patients who received PIs, the most common mutations were V82A/T (12%), M46I (11%), and L90M (8%). Mutations were similar among adults and children. These data indicate that HIV-1 drug resistance develops in South African subtype C-infected patients failing ARV therapy with mutations comparable to those found among patients infected with subtype B viruses.
Understanding how pathogens acquire resistance to drugs is important for the design of treatment strategies, particularly for rapidly evolving viruses such as HIV-1. Drug treatment can exert strong selective pressures and sites within targeted genes that confer resistance frequently evolve far more rapidly than the neutral rate. Rapid evolution at sites that confer resistance to drugs can be used to help elucidate the mechanisms of evolution of drug resistance and to discover or corroborate novel resistance mutations. We have implemented standard maximum likelihood methods that are used to detect diversifying selection and adapted them for use with serially sampled reverse transcriptase (RT) coding sequences isolated from a group of 300 HIV-1 subtype C-infected women before and after single-dose nevirapine (sdNVP) to prevent mother-to-child transmission. We have also extended the standard models of codon evolution for application to the detection of directional selection. Through simulation, we show that the directional selection model can provide a substantial improvement in sensitivity over models of diversifying selection. Five of the sites within the RT gene that are known to harbor mutations that confer resistance to nevirapine (NVP) strongly supported the directional selection model. There was no evidence that other mutations that are known to confer NVP resistance were selected in this cohort. The directional selection model, applied to serially sampled sequences, also had more power than the diversifying selection model to detect selection resulting from factors other than drug resistance. Because inference of selection from serial samples is unlikely to be adversely affected by recombination, the methods we describe may have general applicability to the analysis of positive selection affecting recombining coding sequences when serially sampled data are available.
As a possible factor responsible for reduced fever responses in the newborn, we measured plasma cytokine concentrations and cytokine production by neonatal monocytes after lipopolysaccharide or IL (interleukin)-1 alpha stimulation in vitro and compared these data with those obtained from adult plasma and monocytes. Whole blood was collected from afebrile adults (n = 12) and the umbilical cord of normal term infants (n = 12). Plasma and peripheral blood monocytes were prepared by conventional techniques. Significantly lower concentrations of IL-1 alpha, IL-1 beta (P < 0.05, t-test) and IL-6 (P < 0.01, t-test) were found in the plasma of newborn babies compared with that of adults. There was no significant difference in plasma tumour necrosis factor (TNF) concentrations between the adults and newborn babies. Monocytes from newborn babies had the capacity to produce IL-1 alpha and IL-1 beta as readily as adult cells after stimulation with lipopolysaccharide or IL-1 alpha, and produced significantly lower concentrations of TNF and IL-6 than those produced by stimulated adult monocytes (P < 0.01, ANOVA). Our results suggest that the reduced production of IL-6 by monocytes of the newborn during infection could be partly responsible for attenuated fever responses observed in the neonate.
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