Abstract
Although most of the attempts to apply the complement fixation test in the field of filterable viruses have either been negative or inconclusive, within recent years a few favorable reports have lent more encouragement. The work of Craigie 1 and his coworkers has been of especial value in suggesting a new method of attack. Based on their reports, work was undertaken to extend the test for the differentiation of strains of equine encephalomyelitic virus, representing the so-called eastern and western American types and that of Moscow No. 2. All 3 of the strains may be differentiated serologically by the neutralization test. 2 The virus of lymphocytic choriomeningitis isolated by Dr. C. Armstrong of the National Institute of Health, was also included in the work.
With some slight modifications the antigens were prepared according to the method of Craigie and Tulloch 1 for vaccinia. The equine viruses were carried in the guinea pig and that of the “l.c.m.'virus in the mouse. The brains were removed aseptically from the respective infected animals, were frozen in an ice-salt mixture and dried in a desiccator evacuated by the Cenco-Hyvac pump. The dried material was weighed and ground with ether in the desired proportions. The mixture was shaken, stored on ice for several hours. Then the ether was removed; the residue was ground with 0.85% saline, left for 6–12 hours on ice, frozen several times in an ice-salt mixture and thawed at 37°C. Finally the material was centrifugated and the supernatant fluid removed, which was then ready for use after a preliminary titration for anticomplementary, hemolytic and antigenic properties.
After a careful titration of the complement with the antigen, the test was set up with 0.1 cc. of serum from guinea pigs hyperimmunized to each strain, 0.2 cc. of antigen and 0.2 cc. of complement containing 2 full hemolytic units were then added and the mixture left for 16 hours at refrigerator temperature.
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