Studies on the Development of Natural Immunity to Poliomyelitis in Louisiana

Maternal, umbilical cord, and serially-collected infant blood samples, were available incidental to the “Louisiana Study” of natural infection with polioviruses. By means of the simultaneous titration of series of these specimens, the passive transfer of circulating maternal antibody to the infant and the decline in the infant of the maternally-derived antibody were investigated by the neutralization test. Sixty-six maternal cord blood pairs permitted observation on 188 typespecific comparisons, and showed that the titer of humoral antibody varies, in general, very little within each pair, but that there is a greater tendency for type 3 transfer to be inefficient as compared with types 1 and 2. However, specific transfer inefficiency of any antibody type may be associated with individual women. Since the antibody comparison possessed by children at birth is a function of maternal titer and since the passively acquired antibody gradually disappears, the percentage of seropositive infants in a population gradually diminishes with postpartum age. In this highly endemic area, over 50% of infants were seronegative, at a serum dilution of 1:10, against any one antibody type, by 3 months of age. The implications of this finding to early vaccination were discussed. The half-life for passive polioantibody was calculated by a study of the mean titer of antibody at successive monthly intervals of infants born of mothers with various antibody levels. The decline was found to be exponential in nature and not to vary appreciably or consistently with maternal titer. The half-life of the passive antibody was found to be approximately 25 days.