THE FORMATION AND PROPERTIES OF POLIOVIRUS- NEUTRALIZING ANTIBODY* IV. NOP.~AL A~TIBODY A~-D EARLY l~,r~rU~ A~rrI~oDY OF RABBIT ORIGrN: A COMPARISON OF BIOLOGICAL AND PHYSICOCHEMICAL PROPERTIES B~ SVEN-ERIC SVEHAG,~ D.V.M

A previous communication (1) in this series reported that transient, very rapid macroglobulin antibody responses could be induced in rabbits by small doses of poliovirus (PV) antigen. 19S antibody appeared 8 to 16 hours following immunization in such responses. It was also observed that almost all normal rabbit sera (NRS) contained low background neutralizing activity to several viral antigens, among them PV (2). In the present study the physicochemical nature, cross-reactivity, and avidity of the serum factor responsible for this background neutralization of PV and its relationship to the rapid 19S antibody response, were explored. Normal antibody has been reported to differ from immune antibody in specificity (3) and thermostability (3-6). While in those studies normal antibody was compared with immune antibody collected at a fairly late stage in the course of immunization, in the present study, normal antibody was compared with the earliest detectable induced antibody. Under these circumstances it was found that the physicochemical properties, cross-reactivity, and avidity of normal and early immune antibody to PV were similar, if not identical. The thermodynamic data for the neutralization of PV by normal antibody were the same as those of serological reactions employing immune antibody.