Development of antibody-dependent cell-mediated cytotoxicity in the respiratory tract after natural infection with respiratory syncytial virus

Antibody-dependent cell-mediated cytotoxicity (ADCC) was measured in nasopharyngeal secretions collected from 42 infants and young children at various intervals after primary or secondary infection with respiratory syncytial virus. ADCC was determined by specific immune release of ⁵¹Cr from respiratory syncytial virus-infected HEp-2 cell culture monolayers, with lymphocytes from adult volunteers as effector cells. Specific ADCC responses in nasopharyngeal secretions after primary infection were observed as early as 3 days after the onset of clinical symptoms, and peak activity was observed 14 to 29 days after the onset of illness. ADCC responses after reinfection were significantly greater in both the acute and convalescent phases (P < 0.05) than were ADCC responses after primary infection. ADCC in secretions was mediated primarily by the immunoglobulin G isotype of respiratory syncytial virus antibody.