Fecal IgA Antibody Responses after Oral Poliovirus Vaccination in Infants and Elder Children

We investigated fecal IgA antibody responses after oral polyvalent poliovirus vaccination. Infants were given vaccines twice with an interval of 6 weeks. Specific IgA antibodies in the feces were determined by enzyme-linked immunosorbent assay, and viruses were isolated in tissue cultures. We found that, after the first vaccination, antibody responses seemed to be elicited only against the serotypes of isolated viruses. After the second vaccination, however, antibodies were detected to all three serotypes with higher titers, suggesting that the first vaccination induced the immunologic memory. The IgA antibodies had virus-neutralizing activity, and existed in the feces as both intact 11S and fragmented 4S molecules. Next, children were given the third vaccination 3 or 9 years later. Fecal IgA antibody responses were found to be poorer in elder children, while they responded with high serum neutralization titers. The secretory IgA memory seemed to last much shorter the serum IgG memory.