Day-by-Day Response of Vaccinated Chimpanzees to Poliomyelitic Infection

Abstract

The rise and decline of poliovirus relative to the levels of specific neutralizing antibody in the blood of 7 vaccinated and 7 unvaccinated (control) chimpanzees was studied. The former received commercial trivalent poliomyelitis vaccine. The animals were all challenged at the same time by the feeding of type I poliovirus (Brunhilde strain). Tonsillar swabs and blood serum were collected every day for the next 10 days and somewhat less frequently for the following 2 weeks. Three stool specimens per week were obtained during a 4-week period following challenge and tested for poliovirus as weekly pools. These were carried out in mono-layers of monkey kidney cells while tests for virus in the throat or neutralizing antibody in serum employed the cell growth inhibition test. Two-fold dilutions with 2 tubes/dilution were used for all tests and dozens of the virus isolations were shown to be Type I poliovirus with appropriate antisera. Serum antibody levels at challenge ranged from 1:4 to 1:1,000 in the vaccinated animals (median 1:8), while controls showed no demonstrable antibody. All of the controls acquired alimentary infections as well as all of the vaccinated animals except the 2 with the highest antibody levels at challenge (1:64; 1:1,000 - P = .004). Average titers of virus in the throats and stools of the controls were significantly higher and were maintained for longer periods in the controls than in the vaccinated group. Serum antibody titers rose more rapidly and reached higher levels in the latter. Nevertheless the curves representing the decline of virus titer crossed those of rising antibody at approximately the same point in both groups (1:50 - 1:100), thus indicating some sort of constant relationship between the propagation of virus and its control by antibody.