Immunological Properties of a Sonic Extract of Pneumococci

Abstract

Formalin-killed, young cultures of pneumococci have been found by one of us (Weil) 1 to evoke infiltration when injected intradermally into rabbits, the infiltration being type-specifically neutralizable by antipneumococcal sera. Subsequent experience has shown that for a given amount of antigen the extent of the neutralizing effect is proportional to the antibody content of the anti-sera. In the absence of information as to the nature of the active principle it was tentatively called “the irritating substance”. Type specific carbohydrates alone do not produce infiltration. On the other hand, since there is type-specificity in neutralization with antisera, it must be concluded that the specific soluble substance determines the specificity of the reaction. Therefore, it seemed possible that the “irritating substance” might be related to the long sought complete antigen of the pneumococci.

Because of the apparent lability of the “irritating substance” toward most manipulative procedures, attempts to obtain further knowledge of its nature by chemical methods were unsuccessful. Recently, however, we have obtained the active principle by sonic disintegration of the pneumococci.

The magnetostriction oscillator used in this work was similar to that previously employed by Chambers and Flosdorf² in the sonic extraction of labile antigenic substances from Strep. hemolyticus and Eberthella typhosa. Suspensions of the bacteria were exposed in lots of about 4-0 ml to 9000 c.p.s. vibrations of sufficient intensity to cavitate the liquid vigorously. Temperature of the cultures was so controlled by water cooling that it did not rise above 20°C at any time.

Experiments were done with pneumococci of types 1 and 2, grown for 6 hours at 37°, and with formalinized vaccines from 6-hour cultures of pneumococci of Types 1, 2, 3, 7, and 14. All strains used were highly virulent and the cultures and vaccines were strictly Gram-positive. Heavy suspensions containing 20 to 100 billion organisms per cc were used. All types gave essentially the same results and can therefore be reported together. With the oscillator we used, 60 to 75 minutes of vibration were found necessary to destroy all cocci. Progress of the dissolution could be followed on smears made at different times during the treatment.