Serological Studies on Subjects Vaccinated Against Typhus Fever

Abstract

Since the introduction of louse vaccine by Weigl 1 for active immunization against epidemic typhus, the effectiveness of the vaccine in protecting experimental animals and human beings has been demonstrated. This has been summarized by Biraud and Deutschman. 2 In the last few years, doctors, nurses, and attendants in the Peiping Union Medical College who are likely to be exposed to typhus fever were inoculated with a louse vaccine.∗ This vaccine, comprising a total amount of material from 100 infected lice, was administered in 3 doses. They were given subcutaneously at weekly intervals. It was thought that it might be of interest to study the serological response of individuals after vaccination, especially in view of the scanty information of such kind in the literature. For this purpose, specimens of blood were taken by venapuncture from the vaccinated subjects at different intervals of time after the last injection. The sera so obtained were then used for agglutination against typhus Rickettsiæ and Proteus X₁₉. The agglutination test against the latter was done by the macroscopic technic of Dreyer, in which a formalinized suspension of bacteria was used as antigen. The rick-ettsiæ agglutination test was performed by the macroscopic technic of Zinsser and Castaneda. 3 The suspension was made up of 1 cc of typhus vaccine which contains material from 50 lice and 9 cc of 1:10,000 merthiolated saline. The coarse particles of the suspension were allowed to settle in the ice chest for at least 24 hours before use. The agglutination tubes were incubated in water-bath or incubator at 37°C overnight, after which readings were taken by means of a low magnifying lens (X2). The result was considered to be positive when definite clumping of the organisms was seen. Positive and negative sera were always included each time for antigen control. Serum diluted with saline was similarly incubated to serve as serum control.

The results of the comparative study of Weil-Felix reaction and typhus rickettsial agglutination are summarized in Table I.