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Maternal plasma HIV-1 RNA and the success of zidovudine (ZDV) in the prevention of mother-child transmission.
Sperling RS; Shapiro DE; Coombs R; Todd J; McSherry G; Connor EM;
November 30, 1996
3rd Conf Retro and Opportun Infect. 1996 Jan 28-Feb 1;:161. Unique

Background/Methods: Interim analysis of ACTG 076 showed that a maternal/newborn ZDV regimen reduces mother-infant (MI) transmission [NEJM 1994; 331: 1173-80]. We have (1) updated the efficacy analysis and (2) assayed (Chiron bDNA) stored samples from entry and delivery to determine if maternal plasma HIV-1 RNA predicted ZDV success. Results: As of 10/19/95, 419 MI pairs (210 ZDV-exposed, 209 placebo (PLB)) had at least one infant culture result; estimated transmission rates(Kaplan-Meier at 78 weeks) were 7.8% (95%CI 4.2-11.4%) on ZDV and 24.9%(95%CI 19-30.9%) on PLB, which confirms the interim efficacy results. Maternal RNA levels were balanced between groups at study entry, but were higher overall for transmitters (T) than for non-transmitters (NT) at both entry and delivery (entry: ZDV: median RNA 2620 copies/ml (cp) T vs. 2770 NT; PLB: 5120 T vs. 1850 NT). Transmission occurred in both groups at even the lowest RNA levels (entry: ZDV: range less than 500-57950 cp T vs. less than 500-121900 cp NT; PLB. less than 500-57410 cp T vs. less than 500-60010 cp NT). RNA was reduced from entry to delivery on ZDV compared to PLB (median log drop -0.05 PLB vs. -0.22 ZDV). Transmission risk increased as RNA increased (more so PLB than ZDV), but the treatment effect persisted at all RNA levels (entry RNA less than 1000 cp: 3.9% risk ZDV vs. 12.5% PLB;1000-4999 cp: 9.1% ZDV vs. 19.6% PLB, greater than 5000 cp: 7.5% ZDV vs. 35.4% PLB). Association of antepartum and intrapartum factors with transmission risk is being assessed. Conclusions: (1) RNA was associated with transmission risk. (2) In both groups, transmission occurred across the entire range of RNA levels. (3) Reduction in RNA level may only explain part of the treatment effect.

*Disease Transmission, Vertical Female HIV Infections/*PREVENTION & CONTROL/TRANSMISSION HIV-1/GENETICS/*ISOLATION & PURIF Human Infant Placebos Pregnancy Pregnancy Complications, Infectious RNA, Viral/*BLOOD Zidovudine/*THERAPEUTIC USE ABSTRACT