Reduction of respiratory syncytial virus (RSV) in tracheal aspirates in intubated infants by use of humanized monoclonal antibody to RSV F protein

Thirty-five children <2 years of age mechanically ventilated for respiratory syncytial Virus (RSV) infection were randomized to receive an intravenous infusion of 15 mg/kg MEDI-493 or placebo. RSV concentration was measured in tracheal secretions by plaque assay before and at 24-h intervals after treatment. The reduction in tracheal RSV concentration from day 0 to day 1 (-1.7 ± 0.28 vs. -0.6 ± 0.21 log₁₀ pfu/mL; P = .004) and from day 0 to day 2 (-2.5 ± 0.26 vs. -1.0 ± 0.41 log₁₀ pfu/mL; P = .012) was significantly greater in the MEDI-493 group than in the placebo group. RSV concentration in nasal aspirates did not differ significantly between the groups. No significant differences were observed in the tracheal aspirate white blood cell count, or myeloperoxidase or eosinophilic cationic protein concentration, or in measures of disease severity between the groups. Thus, treatment with 15 mg/kg MEDI-493 intravenously was well-tolerated and significantly reduced RSV concentration in tracheal aspirates of children with respiratory failure due to RSV.