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792 SECRETORY IMMUNOLOGIC RESPONSE TO RESPIRATORY SYNCYTIAL VIRUS INFECTION IN INFANTS: ANTIBODY ON AND OFF EPITHELIAL CELLS

We studied the secretory immunologic response to respiratory syncytial virus (RSV) infection in 22 infants hospitalized for bronchiolitis or pneumonia. Nasopharyngeal secretions were obtained by suction every other day during hospitalization and (in most) once in convalescence. Shed epithelial cells were spotted on slides and acetone-fixed. These were then examined by double-labelling immunofluorescence techniques for RSV and IgG, IgA or IgM antibody. Cell-free secretions were titrated by indirect fluorescence for anti-RSV IgG, IgA and IgM.In 19 of 22 infants IgA was seen coating RSV-infected nasal epithelial cells in the first available secretion (day 1 to 3 of hospitalization), and in all 22 by the 4th day. Cell-free anti-RSV IgA was never evident in the first specimen and appeared, on the average, on the 6th hospital day. In contrast, cell-associated IgG was seen in only 12 infants, often as late as the 4th day. Cell-free anti-RSV IgG appeared in all infants, on the average by the 4th day. RSV antigen was universally present through the 5th hospital day, and in 1/2 of infants for 8 days.Both IgA and IgG antibody appear in secretions of RSV infected infants much earlier than previously suspected, and their possible roles both in cure and in mucosal immune complex disease must be seriously considered.