Respiratory syncytial virus-specific antibody responses in immunoglobulin A and E isotypes to the F and G proteins and to intact virus after natural infection.

We studied the antibody response to the fusion (F) and attachment (G) proteins of respiratory syncytial virus and to purified intact virus in the respiratory secretions of 29 infants and children. The goal of the study was to determine whether the immune response to either of the glycoproteins occurred predominantly in the immunoglobulin A (IgA) as opposed to the IgE isotype, which would indicate that one protein subunit would be a better candidate as a potential vaccine. Antibody responses were determined by using an enzyme-linked immunosorbent assay with purified F and G proteins and sucrose gradient-purified intact virus as targets. Infants and children were capable of developing an antibody response in both the IgA and IgE isotypes to each target antigen. The magnitude of the antibody response to the F protein was essentially similar to that to the intact virus, while responses to the G protein were diminished in infants. A slightly more favorable ratio of IgA to IgE responses was observed against the F protein in comparison to the G protein. While neither protein subunit had the ideal characteristics of inducing an IgA response in the absence of an IgE response, the F protein seems to be a better candidate for use as a vaccine, on the basis of better IgA/IgE ratios.