Rate of Development of Pneumococcus Immunity.

Abstract

Inasmuch as pneumonia is a self-limited disease ending by crisis or lysis generally between the 7th and 10th days, 3 to 5 days are frequently afforded in which an attempt may be made to produce active immunity before the natural termination of the disease takes place. At the suggestion of Dr. A. R. Dochez a study was therefore undertaken of the onset and rate of development of pneumococcus immunity.

The development of pneumococcus immunity after the introduction of pneumococcus vaccine has been studied from many points of view. The onset of immunity has been noted from the 5th to the 14th day by different workers,¹ in a few observations as early as the 3rd day. Many preparations of the antigens have been employed. Some workers² have believed the intact cell necessary for the production of well-marked type-specific immunity, whereas others have found that extracts or solutions of the cells were equally effective.³ As we were interested in the preparation of a vaccine that would be especially effective in initiating early immunity, we compared in this regard a vaccine made from the intact cell with that obtained from a watery extract of the cell.

Three antigens were employed (1) a vaccine made from the intact cell, (2) a Berkefeldt filtrate of shaken bacteria, (3) a Berkefeldt filtrate of the broth culture. The method of preparation was as follows:

A pneumococcus type 11 organism of high virulence was grown for 6 hours in 2.5% human serum beef-infusion broth. This was used to inoculate 250 cc. flasks of similarly prepared broth in the proportion of 0.1 cc. inoculum to 5 cc. broth. At the end of 11 hours' incubation, part of the broth culture was centrifuged and the supernatant fluid passed through a Berkefeldt filter, the so-called broth filtrate.