Levels of Homotypic Neutralizing Antibody in Human Poliomyelitis T H R E E Years after Infection* by Johan

I t has been demonstrated that patients with poliomyelitis, as a rule, have neutralizing antibody for the infecting strain of virus early after onset of first symptoms before the appearance of paralysis, and that this antibody increases in titer during convalescence (1, 2). For a better understanding of human immunity to poliomyelitis and of the part immune individuals may play in the dissemination of the virus in nature, it is necessary to know for how long and at what level homotypic neutralizing antibodies persist. The quantitative estimation of antibody was regarded as important because it is conceivable that the response to reinfection may be determined not so much by mere presence or absence of antibody as by the amount of antibody that is present. The purpose of the present investigation was to determine whether the homotypie neutralizing antibody, after reaching peak levels several months after the onset of clinically recognized poliomyelitis, persisted for many years, rapidly diminished in concentration, or even completely disappeared. A number of patients from whose alimentary tract poliomyelitis virus was recovered during the acute phase of their illness and whose sera had been tested for neutralizing antibody against the recovered strain up to 3 months after onset (1) were available for study 3 years later. Since the strains of virus as well as the 3 month convalescent sera had been preserved, it was possible in simultaneous quantitative tests on the sera obtained 3 months and 3 years after onset, to determine what had happened to the antibody against the infecting strain of virus. All the strains of poliomyelitis virus recovered from these patients were classified immunologically and found to be Type 1, the type most frequently encountered in epidemics of the disease (3). As a check on the extent to which these patients may have been exposed to poliomyelitis virus during the 3 year interval, their sera were also tested for neutralizing antibodies against Type 2 (Lansing) poliomyelitis virus.