Pathogenesis of experimental cholera. Preparation and isolation of choleragen and choleragenoid

Choleragen, a diarrheagenic protein enterotoxin elaborated by Vibrio cholerae, has been isolated from the supernate of fermenter cultures by steps involving ammonium sulfate precipitation, DEAE cellulose, Sephadex G-75, and Agarose A-5m chromatography. The resulting product appears to be pure according to immunoelectrophoretic, disc electrophoretic, ultracentrifugal, and immunologic criteria. Sephadex gel filtration and membrane filtration studies suggest a molecular size of 61,000. The isolated product is highly active in inducing experimental cholera in infant and adult rabbit models. It also elicits, in small dosage, an increased vascular permeability in skin. These observations indicate that choleragenicity and increased vascular permeability are intimately associated phenomena and may be manifestations of the same basic mechanism. An additional, antigenically identical, protein has also been isolated by the same procedures. The latter substance, termed "choleragenoid", lacks the permeability effect and choleragenicity of the choleragen moiety. Its size (estimated from Sephadex gel filtration at 42,000) is smaller than that of choleragen and it also differs in charge. Choleragenoid may prove useful as a nontoxic immunogen to protect against pathologic effects of V. cholerae infection.

The mechanism of action of anti-lymphocyte serum. Studies of antibody eluate

Studies designed to gain insight into the mechanism of action of the active component of antilymphocyte serum were carried out using an antibody eluate prepared from the IgG fraction of anti-lymphocyte serum by absorption and subsequent elution from thymocyte membrane. The resulting antibody eluate was labeled with radionuclide tracer to determine the fate of the antibody in vivo. The result indicated that anti-lymphocytic antibodies are eliminated from recipients extremely rapidly. The mechanism for this rapid clearance appears to depend upon the absorption of antibody molecules onto lymphocyte surfaces and the subsequent clearing and degradation of the antibody-lymphocyte complexes by the reticuloendothelial system. Distribution studies confirm that the major site of antibody-lymphocyte interaction occurs in the periphery with relatively little penetration of antibody within lymphoid organs. Radioautographic studies showed that the pattern of localization within lymphoid and other organs is confined to rather specific areas. These observations are believed to offer strong support for the notion that anti-lymphocyte serum achieves its immunosuppressive effect by bringing about a selective ablation of the population of recirculating lymphocytes.

The anamnestic antibody response to type 3 specific pneumococcal polysaccharide

Rabbits immunized with killed type III pneumococci respond to anamnestic challenge by type specific polysaccharide (S III) with the synthesis of anti-S III antibody if a long interval is allowed to elapse between primary and secondary immunization. A study of the anti-S III antibody produced early and late in the immune response revealed no change in molecular class, banding pattern of dissociated light chains, or S III binding characteristics as measured under equilibrium conditions or by study of dissociation kinetics utilizing radioiodinated p-OH-benzyl-S III. Sequential booster injections of S III into rabbits primarily immunized with whole organisms 8 or 9 months earlier led to a progressive decrease in the number of animals showing successful anamnestic responses and in the magnitude of those responses. It is concluded that S III depletes the antigen sensitive cell population in the secondary response largely because of its limited ability to stimulate sustained proliferation by such cells.