Depression by slime-extract from Pseudomonas aeruginosa of delayed type hypersensitivity to sheep erythrocytes.

High doses of slime-extract from Pseudomonas aeruginosa was found to suppress the delayed type hypersensitivity response to sheep erythrocytes when administered intraperitoneally 1 to 3 days before or 3 days after intravenous sensitization of mice. Moreover, the spleen cells from sensitized and slime-extract treated mice transferred the depression to normal recipients. Inhibition of DTH response was also seen when recipients were injected with slime-extract 24 h before they were infused with spleen cells from donor mice immunized with sheep erythrocytes. The development of skin DTH was quantitated by footpad increase. The data suggest that slime-extract from P. aeruginosa induces in spleens of mice immunosuppressive cells which affect the immunization with sheep red blood cells.

Nonopsonic phagocytosis and intracellular killing of Salmonella typhimurium by peritoneal macrophages of mice immunized with slime-extract from Pseudomonas aeruginosa.

Treatment of mice with slime-extract (SE) from Pseudomonas aeruginosa strain 219 failed to increase the proportion of ingested cells of Salmonella typhimurium by immune macrophages (M phi) of mice. However, activated with SE peritoneal SE peritoneal M phi displayed the enhancement of their nonspecific bactericidal activity. It has been found that immune M phi, depending on the dose of SE used for vaccination, killed intracellularly 38 to 67% of bacterial cells, whereas the mean value for the bactericidal capacity of normal resident phagocytes was 7%. The dose of 100 micrograms of SE enhanced activation of M phi to higher degree than 200 or 400 micrograms. The increase of microbicidal properties of M phi was also seen when mice were pretreated with 50 or 100 micrograms of SE and 24 h later were injected with live S. typhimurium cells. However, the amount of 200 or 400 micrograms significantly reduced the killing activity of M phi against these bacteria.

Phagocytosis and intracellular killing of mucoid and nonmucoid variants of Pseudomonas aeruginosa by polymorphonuclear leukocytes: effect of specific immune sera.

Nonmucoid variants (NM) of 6 Pseudomonas aeruginosa strains were better phagocytized and intracellulary killed by rabbit peripheral polymorphonuclear leukocytes (PMNs) than their mucoid variants (M). The ratios of ingested and killed bacteria of both variants significantly increased in the presence of immune serum with antibodies against slime and somatic antigen (anti-OM) in the phagocytic mixture. Immune sera prepared for slime layer only enhanced the both activities of PMNs against M variant. The anti-O sera significantly increased the phagocytosis and killing of NM variants belonging to the same serogroup of O antigen as the strain used for the preparation of immune serum.

Phagocytosis and intracellular killing of Pseudomonas aeruginosa by peritoneal macrophages of mice.

The poorly mucoid P. aeruginosa 87 strain was better phagocytized by peritoneal macrophages from normal mice than highly mucoid P. aeruginosa 219. However, the macrophages killed significantly greater number of mucoid bacterial cells of P. 219 strain. The immunization of mice with 10, 50 or 100 micrograms of slime-extract P. 87 or P. 219 did not significantly enhance the phagocytic and bactericidal properties of macrophages. The vaccination of animals with viable bacterial cells of P. 219 strain, using several schemes of treatment, slightly augmented both activities of macrophages but the differences between them and control group were statistically not significant. However, the ingestion and killing of the bacteria were suppressed when macrophages were harvested from mice treated with 200 or 400 micrograms of slime-extract P. 219.

Kinetics of humoral response and mechanism of the protection in mice vaccinated with slime-extract from Pseudomonas aeruginosa.

The in vivo experiments on the immunity of mice to P. aeruginosa showed that the vaccination with slime-extract or transfer of immune anti-slime serum enhances the resistance of mice to these organisms. Immunity against P. aeruginosa appears early after vaccination, is long-lasting and very effective since the challenging organisms are eliminated from the mouse spleens within 4 days.

Arthus and delayed type of hypersensitivity to Pseudomonas aeruginosa antigens in mouse.

The time course of footpad swelling in mice of the inbred 129 strain sensitized with the living Pseudomonas aeruginosa or slime extracted from bacteria was studied. Reactions of Arthus type were observed in animals immunized intraperitoneally (i.p.) or intravenously (i.v.) with slime extract and then challenged into the footpad with this preparation. Mice immunized subcutaneously (s.c.) with slime-extract in complete Freund's adjuvant (CAF) and on day 15 challenged into the footpad displayed the swelling characteristic of the delayed-type hypersensitivity (DTH). The delayed onset of reactivity was also seen in mice sensitized with living bacteria into the footpad and then challenged with slime-extract. Maximum DTH reactions were induced in mice challenged on day 14 after priming. The skin infiltration in DTH reacting mice was characteristic of the polysaccharide antigens. At the 24th h following challenge, the predominance of polymorphonuclear (PMN) cells in footpad hypodermis was found as well as heavy infiltration of mononuclear (M) cells.

Protective activity of immune sera against extracellular slime from Pseudomonas aeruginosa on experimental infection in mice.

Slime-extracts from Pseudomonas aeruginosa strains induced in rabbit synthesis of antibodies which protected mice against lethal intraperitoneal challenge. The antislime sera produced the maximal protection when given simultaneously with challenge dose of bacteria or 3 to 24 h before inoculation of animals. Some antisera exhibited also marked activity in groups of mice passively immunized 48, 72 or even 96 h before challenge. No effect was observed when immune serum was administered after infection.

Phagocytosis and intracellular killing of mucoid and nonmucoid Pseudomonas aeruginosa strains isolated from wounds of burned patients.

Phagocytosis and intracellular killing of 10 Pseudomonas aeruginosa strains in mucoid and nonmucoid state were studied. All strains were isolated from wounds of burned patients and belonged to Habs serogroup 0:6. It has been found that nonmucoid P. aeruginosa were phagocytized by guinea-pig leukocytes in greater proportion than mucoid variants of the same strain. Similarly, nonmucoid organisms were more susceptible to phagocytic killing than mucoid ones. These differences have been found statistically significant.

Immunogenic properties of slime produced by Pseudomonas aeruginosa.

The slime of 8 various Pseudomonas aeruginosa strains was purified and used to immunize rabbits. All studied slime-extracts were strongly immunogenic for animals. The level of antibodies against slime was determined by the passive hemagglutination test. Immune hemagglutinins were present mainly in the IgM fraction of antisera.

Some biological and immunological properties of extracellular slime from Pseudomonas aeruginosa.

Extracellular slime from 8 different Pseudomonas aeruginosa strains was extracted and purified. All slime-preparations exhibited immunogenic properties in rabbits vaccinated with detoxified or not detoxified slime. The antisera of both groups of immunized animals possessed strong hemagglutination activity against homologous slime. Immune hemagglutinins were present in the IgM and IgG fractions of serum globulins. The high value of these antibodies was found in rabbit's sera short after injection of slime-extract. The hemagglutinins quickly reached the peak value and maintained in serum over 60-70 days. Biological properties of lyophilized slime-preparations were defined in rabbit-skin test, local Shwartzman test, pyrogenic reaction and measured as LD50 for mouse. Intravenous injection of slime elicited marked changes in the number of leukocytes in the peripheral blood of rabbit. The animals responded to slime either with leukopenia passing into leukocytosis or with leukocytosis without leukopenia.

Effect of bacteriocins on interferon production.

The level of interferon induced with NDV in human diploid cell cultures treated with pyocins was decreased compared with the control culture. This effect was maximal when pyocins were given simultaneously with interferon inducers. In experiments in vivo it was shown that pyocin itself induced very small amount if any of interferon, but administered together with NDV inhibited production of circulating interferone in mice. Similar decrease of interferon production was found when other bacteriocins, namely pneumocin 114 or E-47 aerocin, were used.

Adsorption of pneumocins and aerocins on bacterial cells.

Adsorption of aerocins 1a-E26, 1b-E47, 1b-E43, 2-E26, 2-E47 and pneumocins A-114 and A-902 was found to be dependent on the presence of specific receptors on the surface of sensitive bacteria. Resistant mutants, selected by these bacteriocins, were incapable of adsorption owing to loss or altered structure of receptors. Maximal numbers of Killing Units of pneumocins and aerocins adsorbed by one bacterial cell of sensitive strains were determined. Kinetics of adsorption and degree of killing of bacteria in relation to concentration of bacteriocins were studied. The lethal effect on bacteria was of the "single hit" type, i. e. one particle of aerocin respectively pneumocin killed one bacterial cell.