Abstract
Although many attempts have been made to discover a method of immunizing animals against Typhus exanthematicus, only a few-isolated partially successful results have been reported.
Immunization has been accomplished with live virus mixed with immune serum 1 as well as with repeated injections of minute doses of live virus. 2 Immunization with heated tissues from infected animals has yielded negative results. Positive or partially positive results have, however, been reported with carbolized and formolized suspensions of Rickettsia. Breinl 3 has partially immunized guinea pigs with carbolized suspensions of infected lice stomachs containing large numbers of Rickettsia, while Zinsser and Castaneda 4 have recently reported successful results with formolized suspensions of Rickettsia from tunica material from guinea pigs infected with Mexican Typhus.
Our experiments were conducted with the European virus and we were concerned with the possibility of producing immunity with dead or attenuated virus in tissue suspensions. Suspensions of brain material from infected guinea pigs treated in a variety of ways with antiseptics, metallic sols and colloidal adsorbents yielded negative results. Positive immunization has, however, been obtained by 2 different procedures. These results, interesting in themselves, are significant also because of the theoretical problem involved.
We confirmed the work of Breinl 3 and succeeded in immunizing guinea pigs with formolized Rickettsia suspensions obtained from infected lice. The degree of immunity seems to depend on the quantity of suspension injected. No animals showed temperature above 39°C.
In other experiments brain suspensions were used. In connection with the colloidal adsorption experiments it was found that distilled water inactivated typhus virus after a relatively brief exposure.
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