220 BACTERIAL VACCINES 



PREPARATION OF SENSITIZED BACTERIAL VACCINES 



A highly immune serum is prepared by immunizing a series of rabbits 

 or a goat with the microorganism to be used in preparing the vaccine. 

 The first injections consist of heat-killed emulsions, administered 

 subcutaneously. After the first or second dose the period of heating is 

 gradually reduced, and the dose increased, until finally the injections 

 may be given intravenously and with living microorganisms. From time 

 to time a small amount of serum should be examined for immune 

 bodies : with the typhoid-cholera group, by testing for bacteriolysin and 

 agglutinins; with staphylococci and streptococci, by agglutination, 

 bacteriotropic, and complement-fixation tests; with pneumococci, gon- 

 ococci, and meningococci, by bacteriolytic, agglutination, and bacterio- 

 tropic tests. When a highly immune serum is secured, the animal is 

 bled, the serum isolated, heated to 56 C. for half an hour, and stored 

 in a strictly aseptic manner. 



To "sensitize" the bacteria, thick, even emulsions of young cultures 

 in normal salt solution are treated with one-half to an equal bulk of 

 inactivated immune serum, and the mixture gently agitated at room 

 temperature for from six to twelve hours. The emulsion is then thor- 

 oughly centrifuged, and the residue of bacteria washed three times with 

 sterile salt solution, after the manner in which the red corpuscles are 

 washed. After the final washing the bacteria are resuspended in salt 

 solution, shaken for a time to insure breaking up of agglutinated clumps, 

 counted, heated at 60 C. for an hour, cultured as a test for sterility, and 

 then diluted so that the emulsion will contain slightly larger doses than 

 a corresponding dose of ordinary vaccine prepared for administration. 



" Sensitization " probably consists in the union of bacteriolytic 

 amboceptor with its antigen, and when injected, serves, with the 

 patient's complement, to hasten solution or lysis of the bacteria (antigen), 

 thereby liberating quickly the chemical substances required for the 

 stimulation of antibodies. 



Metchnikoff and Besredka are using sensitized living bacteria, and 

 their work is being followed with much interest. In this country strict 

 legal restrictions and regulations exist regarding the sending of living 

 cultures through the mails. If, therefore, the method should fulfil the 

 high claims and expectations made for it, there may be considerable 

 difficulty in bringing it into general use. 



