Biomedical subjects

R J Arko

Publications and source records attributed to R J Arko.

At least 37 records · Page 2Linked to original sources

PubMed1982

Effects of tampon components on growth and dissemination of Neisseria gonorrhoeae.

Six components used in vaginal tampons were tested for their effects on a strain of Neisseria gonorrhoeae isolated from a patient with disseminated infection. Tampon components containing carboxymethyl cellulose or its derivative prolonged the in-vitro survival of gonococci and, when injected with mucin into mice, significantly (P less than 0.0001) increased the dissemination of gonococci from the peritoneal cavity. In contrast, a component extracted from rayon tampons reduced in-vitro survival and appeared to suppress gonococcal dissemination in mice. Since tampons are used by a large number of women at a time when the risk of developing complications from venereal infections are increased, their effects on potential urogenital pathogens warrant further study.

Animals↗

PubMed1980

Murine infection model for contagious equine metritis: a new venereal disease of horses.

An infection model in laboratory mice for studying the bacterium (proposed name Haemophilus equigenitalis) causing contagious equine metritis is described. Small porous chambers were implanted subcutaneously into mice and after 1 to 3 weeks were inoculated with H equigenitalis. Infections that persisted for > 30 days were established by direct transfer of infective chamber fluid or by injection of laboratory-grown cultures. Immunization of mice with formaldehyde-treated cells induced significant, strain-related immunity to infection and did not appear to require complement as a protection mediator. Substantial differences in staining characteristics and cell morphology were observed between bacteria grown in mouse chambers and those grown on a laboratory medium. These differences were more apparent in smears of the organism stained by a modified Gimenez method than in smears stained by the conventional Gram stain. This murine model may be a convenient and inexpensive method for studying the immunobiology of this newly discovered animal pathogen.

Animals↗

PubMed1979

Complement-enhanced immunity to infection with Neisseria gonorrhoeae in mice.

Subcutaneous chambers were implanted in mice, injected with Neisseria gonorrhoeae, and supplemented with complement as a model for studying the immunogenicity and strain diversity of N. gonorrhoeae. Immunotypic resistance to N. gonorrhoeae in immunized mice was significantly (P less than 0.01) increased by injection of exogenous guinea pig complement into the host before challenge with gonococci. By using this model to test gonococcal isolates from various geographical areas, two highly immunogenic but immunotypically different gonococcal strains were identified. The piliated cells of these strains induced both complement-enhanced immunity and a degree of exogenous complement-independent immunity. The immunity in mice not treated with complement developed more slowly, was less effective, and waned earlier than that which was complement-dependent. Pretreatment with complement, although highly effective in preventing infection in immunized mice, was much less beneficial in terminating already established infections, even though bactericidal antibodies were present at the time of complement treatment. The mouse chamber model in which both complement-mediated and complement-independent mechanisms of protection can be evaluated may provide an additional tool for elucidating the immunology of gonococcal or other microbial infections.

Animals↗

PubMed1979

Immunological and serological diversity of Neisseria gonorrhoeae: identification of new immunotypes and highly protective strains.

Gonococci, irrespective of serotype or immunotype, varied significantly in their capacity to induce immunity in animal models, and in vitro serological relatedness did not always insure in vivo cross-protection. By using a serum bactericidal assay followed by in vivo cross-protection studies, new immunotypic strains which were highly protective were identified from cultures isolated in different geographical areas and from patients with various clinical manifestations. Beta-lactamase production and gonococcal immunotype did not appear as related characteristics in that certain penicillin-sensitive strains were highly effective in immunizing animals against infection with beta-lactamase producers. The findings of this study emphasize the importance of using appropriate biological tests and strains for the investigation of gonococcal immunity and vaccine development. Immunization with a combination of a few major gonococcal immunotypic immunogens may provide substantial protection against the majority of penicillin-sensitive and beta-lactamase-producing gonococci. Investigation of isolated immunotypic immunogens is in progress.

Animals↗

PubMed1979

Nuclease enhancement of specific cell agglutination in a serodiagnostic test for Neisseria gonorrhoeae.

Antiserum to a purified type R lipopolysaccharide antigen isolated from Neisseria gonorrhoeae was used in a slide agglutination test and compared with conventional carbohydrate utilization and fluorescent antibody tests to confirm the identity of laboratory cultures classified as typical or "atypical" N. gonorrhoeae. Cultures of Corynebacterium vaginalis, N. meningitidis, N. catarrhalis, N. sicca, and N. lactamicus were also tested in the slide agglutination procedure. The addition of both deoxyribonuclease and ribonuclease (1 mg/ml) to the cell suspension medium of phosphate-buffered saline improved the sensitivity and specificity of the agglutination reaction for N. gonorrhoeae. Problems relating to the agglutination test as an aid in identification of N. gonorrhoeae are discussed.

Agglutination Tests↗

PubMed1979

"Endotoxicity" of the Legionnaires' disease bacterium.

The Legionnaires' disease (LD) bacterium is a gram-negative organism whose "endotoxicity" appears to differ in several respects from the classic endotoxicity generally associated with gram-negative bacteria. Discrepancies were noted between the high activity of LD bacteria in gelating limulus lysate in vitro and their low pyrogenicity in rabbits. Further in-vivo biologic tests indicated that LD bacteria were relatively weak in "endotoxicity". Analysis of LD bacterial cells and in their cellular fractions by gas-liquid chromatography indicated that LD bacteria did not contain hydroxy fatty acids commonly associated with lipid A of endotoxin. The branched-chain fatty acids that were characteristic of LD bacteria were associated with the cell envelope, and were readily extracted into organic solvents without prior saponification. The presence of 2-keto-3-deoxyoctonate in LD bacteria and cell extracts was detected by a microassay method but remains to be confirmed with gas-liquid chromatography and mass spectrometry. The active principle "endotoxicity" in LD bacteria may be a new type of bacterial lipopolysaccharide.

Animals↗

PubMed1979

Immunochemical, serologic, and immunologic properties of major antigens isolated from the Legionnaires' disease bacterium. Observations bearing on the feasibility of a vaccine.

Two antigens were isolated from each of three strains of the Legionnaires' disease (LD) bacterium. One antigen was serotype-specific; the other cross-reacted with strains of LD bacteria of different serotypes. The serotypic antigens contained all the major branched-chain fatty acids characteristic of LD bacteria and were a lipid-protein-carbohydrate complex. Electrophoresis resolved the serotypic antigen of Knoxville 1 strain into four protein bands and one glycoprotein band with molecular weights ranging from 0.5 to 7.2 x 10(5). The specificity of the serotypic antigens was established by immunofluorescent staining, and double gel diffusion confirmed the absence of cross-reactions between the serotypic antigens of different types and the partial identity of the serotypic antigens from serologically related strains. The cross-reacting antigens formed precipitin bands with all the homologous and heterologous sera tested. Induction of immunity by vaccination with serotypic antigens was shown in three animal models using guinea pigs and mice. Passive-transfer of immunity (IgG) was also shown in mice and guinea pigs. These observations raise the possiblity of a vaccine for protection against infection of LD bacteria.

Animals↗

PubMed1979

Immunologic factors affecting the in-vivo and in-vitro survival of the Legionnaires' disease bacterium.

Immunologic factors affecting viability of the Legionnaires' disease (LD) bacterium were studied in vitro and in vivo in mice and guinea pigs. In bactericidal tests, fresh human serum quickly killed LD cells. Heating fresh serum to 56 degrees C for 30 min destroyed bactericidal activity; absorbing it with bentonite had little effect. Fresh normal human serum was more effective than guinea pig serum. Adding LD cells to fresh normal human serum caused a greater than 50% depletion in functional complement activity, apparently by activating the classic C-142 pathway, because human serum deficient in C4 was not bactericidal. Antibodies to the Knoxville 1 LD strain in guinea pigs showed enhanced complement-mediated bactericidal activity. Without complement, immune guinea pig or human sera prolonged in-vitro LD cell survival. Antibodies to Knoxville 1 in mice depressed in-vitro bactericidal activity of human complement against Knoxville 1. In-vitro bactericidal tests support in-vivo studies in subcutaneous chambers. Complement-deficient mice immunized with Knoxville 1 were (P less than 0.01) less resistant to homologous challenge than nonimmunized mice. Immunized guinea pigs had a greater than 80-fold increase in resistance to subcutaneous-chamber infection.

Animals↗

PubMed1977

Immunity to gonococcal infection induced by vaccination with isolated outer membranes of Neisseria gonorrhoeae in guinea pigs.

Purified outer membranes from Neisseria gonorrhoeae strain M or B were prepared. Gonococcal outer membranes were pure as evidenced by banding insucrose gradients at a density of 1.23 g/cm3, simple protein composition patterns when analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, low succinic dehydrogenase levels, and few precipitin peaks obtained in two-dimensional immuno-electrophoresis against hyperimmune serum to gonococcal sonicates. Isolated outer membranes administered as antigen to guinea pigs produced strain-related protection against gonococcal infection in amounts less than 1% of the weight of whole gonococci required to produce comparable protection in chimpanzees. One-hundred percent (18 of 18) and 95% of control guinea pigs (19 of 20) were infected when challenged with M and B strain gonococci, respectively. In contrast, 26% (eight of 31) and 94% (16 of 17) of guinea pigs immunized with M strain outer membrane were infected when challenged with comparable inocula of M and B strain gonococci, respectively. Similarly, 25% (two of eight) and 100% (six of six) of animals immunized with B strain outer membrane were infected when challenged with comparable inocula of B and M strain gonococci respectively. These results suggest that antigens capable of inducing strain-related protection to gonococcal infection are present within the gonococcal outer membrane.

Animals↗

PubMed1977

Protection against infection with Neisseria gonorrhoeae by immunization with outer membrane protein complex and purified pili.

Some of the antigens that are capable of producing strain-related immunity to gonococcal infection in the guinea pig are located on the outer membrane of Neisseria gonorrhoeae. This finding has been demonstrated by immunization of guinea pigs with isolated outer membranes from two different strains of N. gonorrhoeae prior to challenged. Isolated principal outer membrane protein complex proved a better protective immunogen than purified pili from the same strain of N. gonorrhoeae. Principal outer membrane protein appears to react in antibody-complement-mediated killing of gonococci, whereas antibodies to pili are only weakly bactericidal. Pili-mediated attachment of N. gonorrhoeae to human cells is inhibited by antibodies to pili, and maximal inhibition occurs when antibodies are directed at pili antigenically identical to the pili mediating the attachment.

Animals↗

PubMed1977

Comparative physical and immunological aspects of the chimpanzee and guinea-pig subcutaneous chamber models of Neisseria gonorrhoeae infection.

Physical and immunological characteristics of the chimpanzee and guinea-pig subcutaneous chamber models for Neisseria gonorrhoeae infection were compared to evaluate their usefulness for gonococcal research. Urethral infection in chimpanzees anatomically resembled the human infection; however, individual variation in response, limited availability, and the presence of interfering micro-organisms in the urethra were found to limit the usefulness of the chimpanzee in immunological research. Although the guinea-pig subcutaneous chamber model may not be suitable for studying the attachment of gonococci to host cells or for the local production of IgA, it does have the immunological advantages of being more sensitive to infection, less variable in response, free of interfering micro-organisms, and is readily available to investigators. Except for differences in sensitivity and variability, results with the guinea-pig model paralleled results obtained in experiments with chimpanzees. Unlike chimpanzees, guinea-pigs are a comparatively inexpensive, rapidly replenishable animal, which after subcutaneous implantation with small porous chambers provide a convenient model for studying most immunological aspects of gonococcal infections.

Animals↗

PubMed1977

Virulence and immunogenicity of types 1 and 3 Neisseria gonorrhoeae in guinea pig subcutaneous chambers.

The relative virulence and immunogenicity of type 1 (T1) and type 3 (T3) cells of Neisseria gonorrhoeae were determined by tests with two different kinds of subcutaneous chambers in guinea pigs. In tests with a tissue nonencapsulated (NE) chamber, T1 gonococci were found to be greater than 1000 times more virulent as well as about 1000 times more immunogenic than T3 cells of the same gonococcal strain. However, T1 and T3 cells were found to be equally virulent for a tissue encapsulated (TE) chamber in guinea pigs. Analysis of fluids from the two types of chambers in a complement-dependent bactericidal assay revealed that the NE chamber fluid contained a substantially higher level of complement activity than fluid from TE chambers. The decline in complement level of chamber fluids due to tissue encapsulation was also confirmed by quantitation with rocket gel electrophoresis. A greater resistance of T1 cells to the bactericidal effects of complement appeared to provide a mechanism by which the T1 cells were most virulent than T3 cells for subcutaneous chambers in guinea pigs. Consequently, the NE chamber implant would appear to provide a more relevant environment for studying the virulence, as well as immunological characteristics of gonococcal strains and experimental immunogens.

Animals↗

PubMed1976

Immunological and serological diversity of Neisseria gonorrhoeae: immunotyping of gonococci by cross-protein in guinea pig subcutaneous chambers.

An in vivo typing system for studying the immunological relationship of gonococcal strains was established. Nine gonococcal strains of proven virulence for guinea pig subcutaneous chambers were selected, and these isolates were used to immunize groups of guinea pigs that were subsequently cross-challenged with graduated numbers of gonococci from these isolates. Resistance to infection was determined by culture of fluid from challenged chambers; results were expressed as the median dose, in colony-forming units, of gonococci required to produce infection in each group of immunized guinea pigs. This information was then used to develop immunotypes of gonococci based on the cross-protection results obtained. Four cross-protecting immunotypes were established from the preliminary nine strains tested.

Animals↗

PubMed1976

Immunological and serological diversity of Neisseria gonorrhoeae: gonococcal serotypes and their relationship with immunotypes.

Strains of gonococcus were shown to be immunologically heterologous. Serum bactericidal activity generally correlated with induced immunity to gonococcal challenge as detected by the guinea pig subcutaneous chamber model. Sera devoid of bactericidal activity reflected the lack of cross-protection in subcutaneous chambers. Factors affecting the bactericidal assay described in this report include (i) source of complement, (ii) concentration of test antigen and complement activity, and (iii) presence of calcium and magnesium ions and bovine serum albumin in diluent. Poor correlation was observed between agglutinating activity of the immune sera and protection.

Agglutination Tests↗

PubMed1976

Effects of laboratory maintenance on the nature of surface reactive antigens of Neisseria gonorrhoeae.

The extensive in vitro cultivation methods used in propagating and maintaining gonococcal cells were found to affect their virulence, antigenicity, and ultrastructure. Adapting a laboratory-maintained strain of gonococci to animal virulence resulted in two lines of pilated cells with similar colonial morphologies. The animal-adapted cells, however, had a greater amount of extracellular pili and a more prominent peptidoglycan cell wall layer. They were also more resistant to the bactericidal effects of guinea-pig complement and more reactive in macroagglutination and bactericidal tests with strain-specific gonococcal antibody. In comparative guinea-pig protection trials, formalin-fixed cells of the animal-adapted cell line were 500 times more effective as immunogens than the laboratory-maintained cell line.

Agglutination Tests↗

PubMed1976

T-strain mycoplasma in the chimpanzee.

Specimens from 4 chimpanzees were cultured for T-strain mycoplasma and Mycoplasma hominis. T-strain mycoplasmas were recovered from the genital tract and throat of a male and the genital tract of his female cagemate; neither had clinical evidence of infection. Two other male chimpanzees were culturally negative for T-strain mycoplasmas. M hominis was not isolated from any of the animals. The chimpanzee may serve as a suitable experimental model for studying the role of T-strain mycoplasmas in human urethritis and reproductive failure.

Animals↗

PubMed1976

Immunity in infection with Neisseria gonorrhoeae: duration and serological response in the chimpanzee.

Relative and absolute resistance to urethral and pharyngeal infection with Neisseria gonorrhoeae persisted for up to two years in male chimpanzees parenterally immunized with a colony type 2 gonococcal antigen. Twelve additional adult males were immunized with either a colony type 1 gonococcal antigen or a sham diluent before being challenged with the immunizing isolate of N. gonorrhoeae. Serum specimens were obtained throughout the immunization procedure and tested for indirect fluorescent, bactericidal, microhemagglutinating, and complement-fixing antibody to the immunizing isolate of N. gonorrhoeae. The serological response measured by the indirect fluorescent antibody and serum bactericidal tests correlated most closely with the resistance of individual chimpanzees when they were challenged in the pharynx and urethra with graduated doses of N. gonorrhoeae one month after the last immunization. In this study, the resistance of the immunized chimpanzees to urethral infection with N. gonorrhoeae varied from one to greater than 1,000 times that of sham-injected controls.

Animals↗

PubMed1975

Effects of oxygen and nitrogen on the character of T. pallidum is subcutaneous chambers in mice.

Nitrogen and oxygen gases were injected into mouse subcutaneous chambers which contained virulent Treponema pallidum. The effect of each gas on the viability and survival of T. pallidum in an in vivo system was determined. In comparison with the effects in nontreated control mice, injection of nitrogen enhanced both motility and survival time, but oxygen exerted a deleterious effect.

Animals↗