Abstract
Zinsser and Castaneda 1 were able to produce an effective antityphus serum by prolonged immunization of a horse with formalinized suspensions of Mexican typhus Rickettsiae. With it they could protect guinea pigs not only against infections of Mexican typhus, but also completely against that of the European type. 2 In our study of typhus fever in North China, we have had an opportunity to examine whether or not this serum would have any definite protective action against the local strain. A brief preliminary report on this study follows:
The typhus strain used was obtained from a patient with typhus fever in Peiping. Gajdos and Chang have used it for the preparation of vaccine by the Weigl's louse intestine method in the last few years. 3 The immune horse serum was prepared in the Massachusetts State Serum Laboratory under the supervision of Zinsser and Castaneda. Male guinea pigs weighing between 300 and 400 gm. were used as experimental animals. One-fifteenth of a saline suspension of the brain of an infected guinea pig was injected intraperitoneally into a number of guinea pigs, and 24, 72, and 120 hours later, 1 cc. of immune or normal horse serum was injected subcutaneously. A control animal which received no serum was included. The body temperature was taken twice daily. The record of only one experiment is presented in the accompanying charts. The result of the other experiment was essentially the same.
The practical usefulness of the important finding of Zinsser and Castaneda is such that it needs no special comment. They offered a simple and possibly a successful method to treat and control this serious epidemic disease. Before applying this method to clinical trial here in China, we have endeavored to study its effectiveness in experimental infections. So far, the results obtained seem to indicate that with the dose employed, a significant protection has been obtained by means of this immune horse serum.
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