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A technique for inducing pneumococcal meningitis in mice and a description of the histopathologic changes that accompany this experimentally produced disease are provided in the present report. This infection of mice was investigated to determine whether it could serve as a suitable model for detecting agents that have potential therapeutic utility in bacterial meningitis in man. 21 antibiotics, belonging to six major classes were evaluated for efficacy in the experimental infection. The three most active agents proved to be amoxicillin, cephaloridine, and chlortetracycline. Up to this time, amoxicillin has not been commercially available as an injectable dosage form. However, in view of the compound's outstanding efficacy in the present experiments, it would be desirable to investigate its effectiveness in the naturally occurring disease in man.

L-Tyrosine azobenzene-p-arsonate (RAT) induced cellular immunity without antibody production in guinea pigs. Bifunctional antigens were prepared consisting of one RAT carrier moiety linked either directly to a dinitrophenyl (DNP) haptenic determinant or through one or more 6-amino-caproyl (SAC) spacers. Each SAC unit has an extended span of 8 A. Guinea pigs immunized with these conjugates developed cellular immunity directed against the RAT determinant and antibody specific for the DNP determinant. The anti-DNP response was the same with one or three SAC spacers, but was significantly weaker when the two determinants were joined without a spacer. Animals immunized with either DNP-SAC-TYR or DNP-TYR developed neither cellular nor humoral immunity. Prior immunization with RAT potentiated the secondary anti-hapten response to DNP-SAC-RAT. Modification of RAT at either the arsonate or tyrosine positions showed that other charged groups (sulfonate and trimethylammonium) could substitute for arsonate without loss of immunogenicity. Removal of either the amino or carboxyl group from the side chain of tyrosine did not abolish immunogenicity, but immunogenicity was lost upon removal of both. Immunization with symmetrical bifunctional RAT-(SAC)(n)-RAT and cyclo-(L-RAT-D-RAT) antigens led to cellular immunity but no anti-arsonate antibody, suggesting a barrier to "self-help." These compounds were also ineffective in inducing a secondary anti-arsonate response in animals primed with arsonate-BSA conjugates and RAT.

Bovine glucagon, a polypeptide of 29 amino acids, was immunogenic in guinea pigs. The immunologic determinants of glucagon were investigated using isolated tryptic peptides of the hormone. Antibodies from virtually all of more than two dozen animals had specificity primarily for the amino-terminal heptadecapeptide (NM) and showed little or no binding with the carboxy-terminal undeca- and dodecapeptides (C). The smallest synthetic peptide of a series initiated at residue 16 which measurably bound antibody comprised residues 5-16 of glucagon. In cellular immune assays, both NM and C elicited delayed cutaneous reactions and inhibited the migration of peritoneal cells from immune animals. However, only intact glucagon and its C fragment stimulated lymphoid cells to synthesize DNA. While glucagon was somewhat more active than C, the addition of NM to C did not enhance its transforming activity. The smallest synthetic carboxy-terminal peptide with discernible transforming activity comprised residues 19-29 of glucagon. In both native and synthetic C peptide preparations, the undecapeptide was generally more active than the dodecapeptide, although cells from different animals gave different response patterns. The difference between the two is the presence of arginine at the amino-terminus of the peptide chain. Thus, the recognition specificity of populations of antigen-reactive cells from different animals displays a variation which is at least superficially analogous to that of populations of antibody molecules. In limited experiments using NM and C peptides as immunogens, neither gave rise to delayed hypersensitivity or to glucagon-binding circulating antibody, following a regimen which invariably provoked these responses when glucagon itself served as the immunogen. These results indicate that glucagon was cleaved by trypsin along functional lines into two parts, one of which housed the major antigenic determinant and the other of which carried the major immunogenic determinant, and they are highly compatible with a two-cell mechanism of immune induction. An apparent dissociation between the capacity to provoke delayed hypersensitivity reactions and to transform antigen-reactive cells in culture was observed.