Virulence Antigens Research Articles

Cytoplasmic and membrane proteins of yersiniae cultivated under conditions simulating mammalian intracellular environment.

A procedure is described for fractionating Yersinia grown in small cultures into inner and outer membranes and soluble cytoplasmic proteins. The procedure was applied to the three recognized species of the genus grown under conditions simulating mammalian intracellular fluid with respect to Ca2+ and Mg2+. These conditions are known to elicit the production of the plague virulence antigen V. Isolates capable of making this antigen were compared with virulence-antigen-negative derivatives by two-dimensional electrophoresis. The V antigen was localized to the soluble protein fraction as a peptide that comigrates with the major component of a specific immunoprecipitate. This peptide had an apparent molecular weight of 38,000 and was not found in either apparent molecular weight of 38,000 and was not found in either membrane fraction. The comparison of virulence antigen-producers and nonproducers of Y. pseudotuberculosis and Y. enterocolitica revealed large qualitative and quantitative differences in outer membrane protein patterns, whereas the same comparison for Y. pestis showed only minor differences. The complexity of changes in the various protein fractions corroborate data in the literature indicating that extensive physiological changes occur in virulent organisms cultivated under simulated intracellular conditions.

Infectivity and virulence of Trypanosoma (Trypanozoon) brucei for mice : IV. Dissociation of virulence and variable antigen type in relation to pleomorphism

Previous observations have indicated the possibility that the virulence of a trypanosome is closely associated with its variable antigen type. A set of clone populations has now been examined, all of which bear the same variable antigen. The clones isolated close to the point of isolation were found to be of moderate virulence to mice, whereas those isolated from the same stock following repeated passage were of extreme virulence. Virulence and variable antigen type need not, therefore, necessarily be associated and would appear to depend on the degree of pleomorphism. The degree of virulence exhibited by the clones was found not to be determined by their apparent rate of growth from inoculation to first patency.

Lymphocyte reactivity in patients with gonococcal urethritis.

Lymphocyte reactivity to virulent gonococcal antigen T2 and the non-pathogenic Neisseria pharyngis (NPN) has been studied by using the 14C-thymidine uptake in cell cultures from 42 patients with gonococcal urethritis and from 18 controls. The DNA synthesis in cell cultures with T2 antigen was higher in 21 female patients than in the 18 controls. No differences in DNA synthesis were observed in antigen-stimulated cell cultures from patients with single or multiple infections, from patients with urogenital complication, or from controls. Gonococcal antibodies in the serum were detected by the gonococcal complement-fixation test (GCFT). A study of the possible correlation between the outcome of the serological test and the cellular response to gonococcal antigen showed that 14C-thymidine uptake in lymphocyte cultures from male patients with negative GCFT, stimulated with T2 antigen, was much lower than the thymidine uptake in stimulated cell cultures from all the other male and female patients (P less than 0.001). The DNA synthesis was higher in cell cultures from seronegative women than from seronegative men (P less than 0.01). A significant difference (P less than 0.01) was also noted in the lymphocyte reactivity to gonococcal antigen between controls and all patients, except in those men who gave negative results to the serological tests. There were no differences between these two groups with respect to the thymidine uptake in NPN-stimulated cell cultures.

Specificity of secretory antibodies to bacterial immunogens.

The present investigation examined the specificity of the salivary immune response of axenic and conventional mice to topically administered Salmonella typhi, S. gallinarum, and S. typhimurium. Specific antibacterial antibodies were determined by passive hemagglutination and bacterial agglutination. Reciprocal antibody titers up to 320 were detected in saliva from mice immunized and assayed with homologous antigens. Antibodies to heterologous immunogens exhibited lower mean titers of 10 to 20 under identical conditions. High concentrations of specific antibodies to the somatic (O) antigen were detected in the saliva of mice administered these microorganisms; however, no significant differences in serum antibody levels were detectable after oral immunization. Only low levels of specific antiflagellar (H) antibodies were demonstrated in the saliva of immunized mice, whereas mean reciprocal titers of 20 were observed in the serum. Antibodies to the Vi antigen of S. typhi were detected in the saliva and serum of only those mice administered formalin-treated S. typhi. Examination of the classes of antibody elicited by these organisms indicated that immunoglobulin A (IgA) was the predominant class in saliva against the O antigens. The salivary response to the H antigens was comprised of both IgG and IgA, whereas the specific serum immunoglobulins were consistent with a primary humoral immune reaction. Local antibodies formed in response to the Vi antigen were exclusively IgG. Serum immunoglobulins produced after peroral administration of the somatic and virulence antigens were limited to the IgM class.

THE EFFECT OF CA++ AND MG++ ON LYSIS, GROWTH, AND PRODUCTION OF VIRULENCE ANTIGENS BY PASTEURELLA PESTIS.

Abstract : Experiments were designed to define phenomena of virulence antigen production, bacterial stasis, and lysis in virulent Pasteurella pestis. The observations, by Lawton, that Mg ''induces'' and Ca ''represses'' virulence antigduc tion were verified. Optimal production of these antigens occurred in a chemically defined medium containing 0.02 M MgCl2. and no added CaCl2. This environment results in stasis of cells possessing the genetic potential for producing virulence antigens. The addition of 0.0025 M Ca in the presence of 0. 02 M Mg completely repressed the production of these antigens and permitted cell division to occur. Cells of the rare avirulent mutant type that produces virulence antigens and forms a typical colonies on agar made Ca-deficient grow more slowly in Ca-deficient broth than do those avirulent cells that produce no virulence antigens. Of 16 tested energy sources, none was found to enhance virulence antigen production in the presence of Mg without equally favoring cell division in the presence of Ca. Induced virulent cells retained their morphological integrity; however, they appeared to be somewhat larger and the formation of new cross-septa was not observed.

GENOTYPIC ALTERATIONS ASSOCIATED WITH AVIRULENCE IN STREPTOMYCIN-RESISTANTPASTEURELLA PESTIS

Brubaker, Robert R. (Fort Detrick, Frederick, Md.) and Michael J. Surgalla. Genotypic alterations associated with avirulence in streptomycin-resistant Pasteurella pestis. J. Bacteriol. 84:615-624. 1962.-Avirulence in Pasteurella pestis, as indicated by the existence of a new genotype, was associated with the genetic loss of Ca(++) dependence rather than with the usual concomitant loss of ability to produce virulence antigens. Strains of the new type exhibited all four of the known virulence factors of P. pestis but were avirulent for mice and guinea pigs (ld(50) > 10(8) cells). In addition to producing virulence antigens, the new strains formed rough colonies at 37 C when grown on Ca(++)-deficient medium, as opposed to typical avirulent strains which formed smooth colonies on this medium and failed to produce virulence antigens. Growth of the new strains in a corresponding Ca(++)-deficient broth medium was slow, as compared with that of typical avirulent strains, but was more rapid than that of virulent strains. The new strains were obtained (i) at 26 C by selecting for resistance to streptomycin or (ii) at 37 C by isolation from rough colonies growing on a Ca(++)-deficient agar medium plated with either a virulent streptomycin-sensitive or -resistant culture. Usually, isolates obtained at 26 C exhibited a marked reduction in ability to form colonies upon primary plating at 37 C. Of 108 streptomycin-resistant isolates obtained from six virulent strains, 20% were of the new type. In addition, five isolates were of reduced virulence (mouse ld(50) approximately 10(4) cells) but differed in being Ca(++)-dependent; they possessed all of the known virulence properties. Certain streptomycin-resistant strains failed to give rise to avirulent colonies when plated on a Ca(++)-deficient agar medium containing streptomycin. The significance of this phenomenon, which was not exhibited by the five strains of reduced virulence, is discussed, as are some apparent differences between isolates from a glycerol-fermenting strain and similar isolates obtained from five nonglycerol-fermenting strains.

Experimental Comparison of the Immunogenicity of Antigens in the Residue of Ultrasonated Avirulent Pasteurella Pestis with a Vaccine Prepared with Killed Virulent Whole Organisms

Summary Several P. pestis cell wall antigens were prepared by repeated ultrasonation, and their toxicity and immunogenicity were studied and compared with killed virulent whole organism vaccine by means of toxicity, serologic and immunogenicity tests in guinea pigs and mice. The antigenic components were determined with the gel diffusion test. Preparation of the residue antigens requires a large quantity of starting material and is complicated in comparison with the preparation of killed whole organism vaccine. The solubility of the final material was less than that reported elsewhere. Only a small amount was available for toxicity tests, and this was toxic to neither mice nor guinea pigs. Guinea pigs inoculated with TJW or E. V. 76 in distilled water preparations had rather severe local reactions. The immunogenicity of the tested vaccines was satisfactory and similar except in a few tests in which the whole organism vaccine was superior to the others. In the test system, in which the interval between immunization and challenge was rather short, the antibody response expressed in serologic tests was not pronounced, but in some instances it gave a rough prediction of immunity. The virulence antigens V and W did not play an essential role in these tests. The immunity was directly related to Fraction I antibody. The administration of the whole organism vaccine in oil adjuvant to guinea pigs enhanced and sustained Fraction I antibody formation.

Progress in Bacteriological Technique

PROF. J. CRUICKSHANK has prepared for the British Council an account of recent advances in bacteriological methods (Brit. Med. Bull., 1, No. 8; 1943). The principal advances in the last ten years have, in his opinion, been made in the discovery of more efficient selective culture media for the isolation of bacteria, in the determination of the stable subgroups or types of bacteria and in the development of typing methods which make it possible to trace the probable source of an infection or an epidemic. Antigenic analysis has resulted in such valuable discoveries as the Vi or virulence antigen of the typhoid bacillus. Antityphoid serum made for therapeutic use should contain Vi antibodies. The blood of typhoid carriers almost always contains these, so that the Vi agglutination test has become a valuable means of helping to trace the sources of the infection. The discovery of a Vi bacteriophage, which has a specific action on Vi strains of typhoid bacilli, can be used for the identification of particular strains of these bacilli. Epidemiologists have used this means of tracing the source of isolated infections or epidemics. The typing of diphtheria bacilli has also produced valuable results.

Sonic Extraction of Labile Bacterial Constituents

Recent investigations have indicated that the killing of certain bacteria by available agents destroys or alters at least some of their antigenic constituents. Thus the investigations of Felix1 have revealed a labile virulence (Vi) antigen detected only in living, virulent strains of Eb. typhi. Similarly, Mudd, Pettit, Lackman and Czarnetzky2 have found that the antibody responsible for the phagocytosis of a strain of Streptococcus hemolyticus is elicited in rabbits by the injection of living organisms and that the living organisms will absorb the antibody from immune serum so produced. The corresponding bacterial antigen itself has resisted all ordinary methods of separation or fractionation.Since it has been shown that sonically killed bacteria are disintegrated3,4,5 and since some heat labile proteins are not denatured by the sonic treatment,6 it appeared possible that labile but important antigens such as those referred to above might be extracted by an adaptation of the method of sonic disintegration...

A Contribution to the Problem of the Virulence (“VI”) Antigen of B. typhosus

SUMMARY1. The strains of B. typhosus, which are inagglutinable, or non-sensitive to somatic O agglutinins, are virulent, whereas the agglutinable, or sensitive strains, show a low virulence.2. Virulence and inagglutinability of strains seem to depend upon the presence in them of a virulence (Vi) antigen.3. A considerable protective action, observed by means of active and passive immunisation, is exerted by the inagglutinable strain used (205 D), because it contains Vi antigen.4. When the O and H agglutinins are eliminated through absorption, the agglutination reaction may serve to demonstrate in vitro the presence of the Vi antibody.