METHODS: We retrospectively reviewed all data for perinatal

1. HIGH LEVEL OF RESISTANCE NVP EFV DLV FTC DDI D4T AZT 3TC TPV SQV NFV LPV IDV FPV ATV ABC 0% 10% 20% 30% 40% 50% 60% ABC ATV FPV IDV LPV NFV SQV TPV 3TC AZT D4T DDI FTC DLV EFV NVP 5% 5% 8% 10% 5% 38% 5% 3% 55% 25% 20% 8% 55% 43% 30% 48% HIV-1 Drug Resistance Mutations in a Cohort of Perinatal Infected Children/adolescentsG.P.Del Bianco,MD, G.A.Contreras,MD, A.S.Kalaskar,MD, N.Perez,DO, J.R.Murphy,PhD, and G.P.Heresi,MD.The University of Texas Health Science Center at Houston WEPE0041 INTRODUCTION: HIV-1drug resistance mutations greatly impact therapeutic choices both in children and adults. However, data on the frequency of mutations in pediatrics/adolescent population are limited. RESULTS: Forty children met the inclusion criteria. Median age at genotype 8.09 years (IQR; 6.25-11.07 years). Thirty (75%) children were Black and 10 (25%) Hispanic; 23 female (57.5%) and 17 (42.5%) male. Seventeen (40%) were diagnosed as AIDS. Viral load median 74,655, range 1,460-538,000 copies per milliliter ; median CD4% 26.1, range 0.6-58.7. The distribution of NRTI, NNRTI, and PI mutations are presented in figures 1, 2, and 3, respectively. At least a third of the patients had high levels of resistance to FTC, 3TC, NVP, DLV, and NFV (fig.4). Low to intermediate resistance was found to more recently developed drugs (fig.5). A higher frequency of NRTI and PI mutations was consistent with historical exposure to these classes of drugs (fig.6). CONCLUSION:All patients were antiretroviral drug experienced and the specific antiretroviral therapies applied were functions of both the patient's characteristics and the drugs available at the time of the therapeutic decision. In spite of these multiple confounders, genotypic analyses identified antiretroviral regimens for which established resistance was not present. OBJECTIVES:To identify the most common mutations associated with virological failure inpatients attending a pediatric/adolescent clinic. METHODS: We retrospectively reviewed all data for perinatal HIV-1 infected individuals on ARVT who were antiretroviral experienced, and who had undergone genotype testing after virologic failure from 1999 to 2007 at UT Houston. The collected data included: genotypic resistance mutations; viral load and CD4+ count at time of virologic failure (defined as >1000 copies/ml after ARVT of > 6 months); demographics (birth date, gender, and race); and date of HIV and AIDS diagnoses. Antiretroviral therapy history was documented as lifetime number of drugs by drug class (NRTI-NNRTI-PI). ARVT received at birth was excluded. The Stanford University HIV Drug Resistance Database was used to characterize patterns of ARV resistance (low-level resistance, intermediate level resistance and high level resistance). Fig.3 Fig.1 Fig.2 Fig.6 Fig.4 Fig.5

2. LIFETIME NUMBER OF ARVT 100% 80% 60% 40% 20% HIGH LEVEL OF RESISTANCE 0% Never Never Never PI <3 # PI >3 # PI <3 # NNRTI >3 # NNRTI <3 # NRTI >3 # NRTI NNRTI NRTI NVP 13% 57% 30% 50% 45% 5% 0% 0% 100% EFV DLV FTC DDI D4T AZT 3TC TPV SQV NFV LPV IDV FPV ATV ABC 0% 10% 20% 30% 40% 50% 60% ABC ATV FPV IDV LPV NFV SQV TPV 3TC AZT D4T DDI FTC DLV EFV NVP 5% 5% 8% 10% 5% 38% 5% 3% 55% 25% 20% 8% 55% 43% 30% 48%