POLIOMYELITIS IN CANADIAN ESKIMOS LABORATORY STUDIES. IV. ANTIGENIC TYPING OF VIRUS STRAINS IN MONKEYS AND IN TISSUE CULTURES

Abstract

Three strains of poliomyelitis virus isolated from Eskimos infected in the outbreak of poliomyelitis occurring at Chesterfield Inlet, N.W.T., in February 1949 have been typed. This typing has been carried out in monkeys and in tissue cultures. Typing was carried out by preparing in rhesus monkeys antiserum to the Eskimo strains and testing these for capacity to neutralize a fixed dose of the Brunhilde (Type 1) and Leon (Type 3) strains on thalamic inoculation of monkeys, and of the Lansing (Type 2) strain on cerebral injection of mice. Antisera prepared against Strains E3-56 and E3-227 completely neutralized Brunhilde virus, as shown on thalamic inoculation of virus-serum mixtures in groups of five monkeys. In contrast, these sera did not neutralize Leon virus. Tests carried out in mice showed that antisera to these Eskimo strains failed to neutralize Lansing virus. It was concluded therefore that Eskimo Strains E3-56 and E3-227 belong to Type 1. The same two sera were tested for their capacity to inhibit the cytopathogenic effect induced in roller-tube cultures of monkey testis by representative strains of the three types (Brunhilde, Y-SK, and Saukett). The two Eskimo sera inhibited the cytopathogenic effect induced by the Brunhilde strain but not the changes induced by the Y-SK and Saukett strains, confirming that the corresponding Eskimo viruses belonged to Type 1. Eskimo Strains E3-79 and E3-227 have also been typed in tissue cultures by a direct method; in this method antisera to the three prototype viruses were tested for capacity to inhibit the cytopathogenic effect induced by the Eskimo strains. Results of this test were in agreement, the Eskimo strains belonging to Type 1. Two strains of virus isolated from the Chesterfield Inlet outbreak have previously been typed by U.S. investigators, by techniques involving the use of monkeys. A total of five strains isolated from this epidemic have therefore been typed, and all have been found to belong to Type 1. This study illustrates that the typing of poliomyelitis strains can be carried out more rapidly and more economically in tissue culture than in monkeys.