Palivizumab-resistant human respiratory syncytial virus infection in infancy.

Palivizumab-resistant respiratory syncytial virus was isolated from an infant treated with palivizumab. A stable mutation at codon 276 led to a nearly complete resistance to palivizumab. Additional studies revealed a second mutation at codon 272. Further passage of the virus led to a complete loss of binding of palivizumab.