THE NEUTRALIZATION TEST IN POLIOMYELITIS : COMPARATIVE RESULTS WITH FOUR STRAINS OF THE VIRUS.

In experiments devised to compare the neutralizing action of normal adult human sera on different strains of poliomyelitis virus, and to fill in certain gaps in our series of neutralization tests with different strains of virus on different types of cases in different age groups, we have made the following observations. 1. The difference between two human and two passage strains of the virus when tested by this method amounted to about 25 per cent, and there was less power in normal adult sera to neutralize human than passage strains of virus. 2. The differences between the two human strains amounted to 15 per cent, and between the two passage strains to 8 per cent, the last figure falling within the limits of the experimental error of the method. The extent to which these findings affect certain concepts with regard to the epidemiology of poliomyelitis based on passage strain neutralization experiments cannot be determined from the data presented in this paper, except that they more or less confirm the view previously derived from passage strain experiments, that 70 to 95 per cent of normal urban adults possess in their blood, substance which neutralizes poliomyelitis virus in a given amount. However, certain other indications appear when the present results are supplemented by those we have previously obtained (25). Primarily, we have found no relation between the clinical acquisition of poliomyelitis and the presence of substance in the serum which neutralizes a passage strain of poliomyelitis virus. With a passage strain the results seem rather to bear a closer relationship to age than to illness. With a human strain we have obtained results in which there is some evidence, shown only in the juvenile group, that acquisition of the clinical disease is accompanied by the appearance of antiviral properties in the blood.