Active immunization with sensitized and non-sensitized bacteria

Abstract

In a previous communication 1 we reported that the serum of rabbits which had been injected with sensitized vaccine or living cultures of Streptococcus viridans, did not contain agglutinins, complement fixing antibodies or protective antibodies. Later similar results were obtained with sensitized vaccines of pneumococci, with the exception that the serum of animals inoculated with sensitized living pneumococci showed a rapid production of these antibodies. We then attempted to determine whether there was evidence of active immunity even though no antibodies could be demonstrated in the serum. It has been found impossible to immunize mice with green streptococci. Rats may be immunized with green streptococci, but the virulence of these organisms is so low that it is impossible to compare the results of immunity with the different forms of vaccines. For comparative study pneumococci are more satisfactory because of the high virulence of these organisms. Throughout the work type I pneumococcus has been used.

Four types of vaccine have been studied, (A) plain stock vaccine, killed at 56°; (B) sensitized stock vaccine, killed at 56°; (C) freshly prepared sensitized vaccine, killed at 56°; and (D) an alcohol precipitate of sensitized vaccine similar to that used by Gay in the preparation of typhoid vaccine.

Immunization was carried out by intraperitoneal injection of increasing quantities at three or four day intervals. Immunity has been studied in mice, guinea pigs and rats.

Mice immunized with three injections and tested from seven to eleven days after the last immunizing dose, showed immunity from all types of vaccines. The mice immunized with vaccine D were uniformly less immune than those with the other vaccines. There were only slight differences in the animals immunized with plain and sensitized vaccine, and in different experiments the results varied so that neither vaccine can be said to be better.