The Titration of Pneumococcus “Exudate” Antisera.

Abstract

In a previous communication 1 a method for the production of anti-pneumococcus serum by means of the immunization of horses with type specific pneumococcus pleural exudates was reported. Sera prepared by this method were found to contain protective substances in about the same concentration as other sera prepared by intravenous immunization with pneumococcus vaccine, when tested in mice. However, in view of the fact that it was felt that the “exudate” antisera might contain certain anti-substances resulting from a possible antigenic effect of the cellular components of the inflammatory exudate (acting either alone, or in the nature of a haptene to the type specific pneumococcus protein radicle therein present) it seemed necessary to titrate such antisera under conditions in which both the bacterial and the cellular antigenic components would co-exist and be capable of some quantitative measurement. The method of producing an acute inflammatory lesion by intradermal injection of the pneumococcus as outlined by Zinsser 2 and later studied in detail by Goodner 3 , 4 provided at the local site of inflammation both the bacterial and the cellular components in the course of an active infection of the skin, and therefore seemed suitable for measuring the potency of such “exudate” antisera.

Tests conducted with serum from a horse immunized with Type I pneumococcus exudate intravenously, and controlled with several sera from horses immunized with vaccine show that a larger number of rabbits are protected against a standard dose of Type I pneumococcus culture injected intradermally when they receive a given mouse unit dose of “exudate” antiserum, than when a similar dose of “vaccine” antiserum is administered at the same time after infection. Thus, of a group of 53 rabbits receiving a skin infection of about 200,000 organisms each, of 27 treated with 450 units of “exudate” antiserum, six hours after infection, 19 survived (70.4%) while of a similar group of 26 receiving 450 units of “vaccine” antiserum six hours after infection, only 9 (34.7%) survived.