THE FORMATION AND PROPERTIES OF POLIOVIRUS-NEUTRALIZING ANTIBODY

Rapid formation of poliovirus-neutralizing antibody was observed in the rabbit. 19S type antibody was detectable 8 to 12 hours following a single intravenous virus injection and the induction period was of the order of 4 to 5 hours or less. The production of 7S antibody had a longer lag phase (1(1/2) to 2 days) and it was formed at slower rate. The observed rate of early 19S and 7S antibody formation as well as the peak titers of the two antibodies were antigen dose dependent. Normal rabbit sera showed low neutralizing activity to several viral antigens in a sensitive assay system. Following intravenous inoculation of poliovirus either transitory ( 1 month) or enduring ((3/4) to 1(1/2) year) antibody formation resulted depending upon the dose of antigen employed. In transitory responses, which could be induced by a single small antigen dose, only 19S antibody was demonstrable and there was an abrupt cessation of antibody synthesis on day 4 or 5. In enduring responses, both 19S and 7S antibody were formed and the minimum antigen dose required for initiation of such a response was equal to the dose needed for induction of 7S antibody formation. Thus, enduring antibody formation was an all-or-none phenomenon depending upon whether or not 7S antibody formation was induced. The antigen dose requirement for induction of 7S antibody was much higher (by 50-fold or more) than that for 19S antibody. This allowed a determination of antigen dose regions, within which predictably transitory (19S) or enduring (19S + 7S) antibody formation was obtained. These pronounced differences in antigen dose requirement for induction and kinetics of formation of 19S and 7S antibody suggest that the same cells do not participate in the formation of the two antibodies.