The Immunizing Value for Mice of Vaccines Prepared from R and S B. Enteritidis *

Although the questions of immunity induced by bacterial vaccines and of the type of vaccine best suited to the purpose have received a wealth of attention, renewed interest in this aspect of immunology has become manifest since the basic differences between smooth and rough bacterial strains have become recognized. That such qualities as smoothness and roughness are more than superficial and actually have a bearing upon immunizing potency is known, but curiously enough there is still lack of complete agreement as to which of the types is the more effective. That vaccines prepared from R strains of B. typhosus and B. paratyphosus fail to immunize guinea pigs against intraperitoneal infection with these organisms has been shown by Arkwright', who also found that vaccines prepared from the S strains of the same organisms gave effective protection against the homologous infection. Using the Rawlings type of B. typhosus, Grinnell7'reported that most of these strains are either of the rough or intermediate types, and that vaccines prepared from these rough types fail to immunize mice against the intraperitoneal injection of smooth, virulent B. typhosus cultures. Grinnell further showed that the smooth type not only had greater virulence for mice, but that vaccines of the smooth type were immunizing. Felix"'4 observed that the heatstable 0 antigen was necessary for the development of the bactericidal antibodies and he assumed the latter to be essential to immunity. This conclusion was modified by Springut'0, who, experimenting with an aertrycke infection in mice, stated that in order to immunize both the H and the 0 antigens were necessary. Ibraham and Shiutze8, also working with immunity to aertrycke infection in mice, found that the rough antigen alone was without effect, but that the presence of the H antigen increased the effectiveness of the 0 antigen, thus confirming the observation of Springut. Grinnell' showed that the injection of man with "smooth" vaccines stimulated the