Agglutination of Encephalitis Virus-Coated-Bacterial Cells by Virus Antisera

Abstract

Details of the technic involved in satisfactorily coating bacterial cells with serum antigen and the use of such cells in an agglutination test have been given in a previous report. 1 A particular advantage of the procedure is that very minute amounts of serum antibody specific for the adsorbed antigen can be detected, even though the amount of antibody is too small to be revealed by the conventional precipitation test. The use of this very sensitive type of an antigen-antibody reaction, for the detection of 'antibodies'in the blood of man and of animals against the virus of St. Louis type of encephalitis, is the basis of the present report.

The microörganisms (Serratia marcesens) were prepared for use in the agglutination reaction by incubating them with virus as contained in a saline emulsion of infected mouse brain. That virus was adsorbed by the bacteria in significant quantity was indicated by the observation that such cells, after repeated washing with saline, would subsequently reproduce the disease in mice upon intranasal implantation.∗ Suspensions of virus-coated bacteria were employed as antigens in making agglutination tests with the sera of (a) human beings convalescent from encephalitis, (b) normal individuals, and (c) of rabbits immunized against encephalitis virus.

With the sera of convalescent patients† agglutination reactions occurred in dilutions ranging from 1:16 to 1:128. The specific nature of the agglutination reaction was indicated by the observation that after adsorption of these sera with virus-coated bacterial cells they failed to elicit the agglutination reaction when tested against additional preparations of virus-coated cells. On the other hand, sera adsorbed with bacterial cells coated with normal mouse brain were capable of agglutinating virus-coated cells to the original titer. In addition, similar adsorption of these sera with the brain substance of normal mice did not remove the capacity of the sera to react with cells coated with mouse brain-virus.