Active Immunity to Endemic Typhus Fever as Produced by Formolized Infected Tissue

Abstract

Formolized tissue (Tunica vaginalis) prepared according to Zinsser's method 1 and administered intraperitoneally in 4 weekly doses of 1 cc. each to non-infected guinea pigs brought about in test animals an immunity to at least 200 times enough virus to cause a scrotal reaction in 4 days. One cc. of a 1-10 saline emulsion of tissue taken at the height of reaction contained at least 200 times enough virus to cause a typical typhus reaction in the male guinea pig after 4 days.

Animals similarly tested one week after 1, 2, or 3 1 cc. doses of “vaccine” all reacted positively to the test dose. Furthermore, protection was not found to be complete in animals that had received 1 or three 1 cc. doses of “vaccine” plus 4 weeks'rest when these animals were given the test dose. Only animals receiving 3 doses of vaccine followed by 4 weeks'rest were found to have any resistance at all to the test dose, and while these animals developed no definite scrotal reactions, all of them had temperature courses typical for endemic typhus fever in the guinea pig.

To determine the duration of their resistance, 6 animals previously immunized were tested at various intervals by inoculating them intraperitoneally with 1 cc. Two of these test animals were immune to the above dose 2 months after completion of the four 1 cc. dose “vaccination”, and 2 others were immune to the test dose 3 months after the same “vaccination”. When tested at 4 months one of the remaining 2 animals developed a slight scrotal swelling 4 days after receiving the test dose. This swelling persisted for 3 days and was accompanied by daily temperatures of 103.2°F. to 105.0°F.