On the Property of Certain Normal Animal Sera to Neutralize the Virus of Poliomyelitis. 20

Abstract

It has been known for a long time that the sera of children and monkeys, who have suffered from poliomyelitis, are capable of neutralizing the specific virus, although the frequency of this occurrence appears by no means to be as regular as was formerly believed 1 More recently a high percentage of normal adults, giving no history of a previous attack or of contact with the disease, have also been found to possess virucidal substances in their blood. 2 A number of authors, by indirect inference, have deduced from epidemiological criteria, that this capacity is acquired through exposure to subclinical infections. 3 In contrast to this viewpoint, we 4 have recently presented direct experimental evidence which strongly suggests that resistance to poliomyelitis as expressed by the fall of morbidity and the rising level of serological activity with increasing age, is predominantly a function of normal physiological maturation and to a large extent seems to develop independently of previous contact with the specific antigen. In further support of such a conception—or rather in opposition to the general validity of the exposure theory—the following observations are reported which bear on the presence of virucidal substances in the normal sera of certain susceptible and nonsusceptible animals.

Rhesus monkey. There is general agreement in the literature that the serum of immature monkeys is uniformly devoid of neutralizing power. We can confirm this point from a summary of 16 tests on a corresponding number of individual samples of serum obtained from normal rhesus monkeys ranging in probable age between 1 1/2 and 3 years. In no case did we observe any neutralization effect with any of the described sera when amounts of 0.6 to 0.8 cc. of serum were tested against 0.6 cc. or 0.4 cc. respectively of a 10% virus suspension (contact 1 1/2 hours at 37°C, overnight icebox).