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Biomedical subjects

A B Petrov

Publications and source records attributed to A B Petrov.

13 recordsLinked to original sources
PubMed1999

Cardiovascular aspects of experimental meningococcal sepsis in young and older awake piglets: age-related differences.

Severe meningococcal disease is characterized by: a high load of specific endotoxin, capillary leakage and coagulation disorders. We studied the possible age-related differences in global hemodynamic and regional blood flow responses to different dosages (1 and 10 microg/kg body weight) of rough meningococcal endotoxin in young (8 kg) and older piglets (40 kg). Animals were chronically instrumented and studied in the awake state. The response to plasma infusion (30 mL/kg in 30 min) was evaluated after placebo and endotoxin infusion. The clinical picture was similar in all groups. The mortality was 0/8, 3/8,1/8, 4/9 in young-low, young-high, old-low, and old-high dose respectively. Most important findings were that cardiac index (CI) decreased in the young animals after endotoxin infusion, while it was well preserved in the older animals; in the older animals the systemic vascular resistance dropped 20%, while in the younger ones there was no change in resistance. Conductance to the kidneys, intestines, and spleen decreased significantly more in the young animals, while the increase in conductance and flow to the liver was higher in the old animals; subsequent volume loading resulted only partly in a recovery of the hemodynamic parameters, but failed to improve oxygen delivery.

Age Factors↗
PubMed1994

Non-specific modulation of the immune response with liposomal meningococcal lipopolysaccharide: role of different cells and cytokines.

The immunomodulating action of Neisseria meningitidis lipopolysaccharide (LPS) incorporated into liposomes and the activation of different populations of immunocompetent cells or the secretion of cytokines were studied. LPS stimulated an anti-sheep red blood cell (SRBC) plaque-forming cell response in the spleen of mice after simultaneous injection of LPS and SRBC but if LPS was administered 3 days before the immunization with SRBC the response to SRBC was strongly suppressed. After the incorporation of LPS into liposomes the stimulation index was increased from 6 to 19 and the liposomal LPS did not suppress the immune response to SRBC. The incorporation of LPS into liposomes leads to enhancement of B-mitogenic properties of LPS, as liposomal LPS stimulated the proliferation of splenocytes in mice better than free LPS and has no influence on the thymocytes. The liposomal LPS induced more prolonged and significant accumulation of IgM-secreting cells in the spleen of mice in comparison with the free LPS. Liposomal LPS also induced more active accumulation of IFN-gamma in human peripheral blood mononuclear cells and less active accumulation of monokines, contributing to the realization of the toxic properties of endotoxin (IL-1 alpha, TNF-alpha, IL-6 and GM-CSF). These results demonstrated that the incorporation of N. meningitidis LPS into liposomes dramatically changed its immunomodulating activity. The data obtained are important for the construction of an adjuvant formulation for synthetic immunogens capable of inducing genetically unrestricted immune responses.

Adjuvants, Immunologic↗
PubMed1992

Toxicity and immunogenicity of Neisseria meningitidis lipopolysaccharide incorporated into liposomes.

To obtain nontoxic and highly immunogenic lipopolysaccharide (LPS) for immunization, we incorporated Neisseria meningitidis LPS into liposomes. Native LPS and its salts were incorporated by the method of dehydration-rehydration of vesicles or prolonged cosonication. The most complete incorporation of LPS into liposomes and a decrease in toxicity were achieved by the method of dehydration-rehydration of vesicles. Three forms of LPS (H+ form, Mg2+ salt, and triethanolamine salt) showed different solubilities in water, the acidic form of LPS, with the most pronounced hydrophobic properties, being capable of practically complete association with liposomal membranes. An evaluation of the activity of liposomal LPS in vitro (by the Limulus amoebocyte test) and in vivo (by monitoring the pyrogenic reaction in rabbits) revealed a decrease in endotoxin activity of up to 1,000-fold. In addition, the pyrogenic activity of liposomal LPS was comparable to that of a meningococcal polysaccharide vaccine. Liposomes had a pronounced adjuvant effect on the immune response to LPS. Thus, the level of anti-LPS plaque-forming cells in the spleens of mice immunized with liposomal LPS was 1 order of magnitude higher and could be observed for a longer time (until day 21, i.e., the term of observation) than in mice immunized with free LPS. The same regularity was revealed in a study done with an enzyme-linked immunosorbent assay. This study also established that antibodies induced by immunization belonged to the immunoglobulin M and G classes, which are capable of prolonged circulation. Moreover, liposomal LPS induced a pronounced immune response in CBA/N mice (defective in B lymphocytes of the LyB-5+ subpopulation). The latter results indicate that the immunogenic action of liposomal LPS occurs at an early age.

Animals↗
PubMed1991

[The effect of the nature of the strain on the character of the production of iron-dependent proteins by meningococci].

The comparative study of three Neisseria meningitidis strains (15, 125, 2394) was carried out by the method of electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate and by the method of immunoblotting. The intensive expression of 8 iron-regulated proteins (IRP) was shown to occur in iron-deficient culture medium. The major IRP with a molecular weight of 35 kD was expressed by all above-mentioned N. meningitidis strains under the conditions of iron deficiency and cross-reacted with 10 mouse and rabbit antisera to N. meningitidis of different groups, i.e. it was common to all Neisseria species. The antigenic activity of various IRP essentially differed with respect to antisera of animals and sera of patients with meningococcal infection.

Animals↗
PubMed1991

[The effect of the iron content in the culture medium on the nature of the protein spectrum in Neisseria meningitidis].

The protein spectra of Neisseria meningitidis, strain A 208, in the process of its cultivation on solid culture medium based on peptone agar under the conditions of the surplus or deficiency of ions of trivalent iron in the medium. The creation of iron deficiency by the introduction of two iron-binding admixtures, desferol and diethylenetriaminepentaacetic acid (DTPA), was found to lead to the production of two additional proteins with molecular weights of 72 kD and 36-37 kD by meningococcal cells. Of these two admixtures, DTPA more readily stimulated the production of low-molecular protein with a molecular weight of 36-37 kD. This protein was found to be noticeably labile, while protein with a molecular weight of 72-73 kD showed no such lability. As the result of the cultivation of meningococci in iron-deficient medium, the content of protein in microbial residue was 2- to 3-fold greater than that obtained by the cultivation of meningococci in culture medium with the surplus of iron in the form of ferric nitrate.

Bacterial Proteins↗
PubMed1991

[The immunological status indices of monkeys inoculated with a meningococcal B vaccine].

The method for the determination of bacterial antibodies to group B meningococci was worked out. The method was used for the determination of antibodies to group B meningococcal vaccine produced in the USSR. The dynamic study of antibodies to protein, polysaccharide and lipopolysaccharide antigens of group B meningococci was made by the method of the enzyme immunoassay (EIA), and the safety of the vaccine was studied by the determination of autoantibodies active against brain tissue antigens. The data thus obtained were indicative of the immunological activity of group B protein-polysaccharide vaccines, manifested by the capacity for stimulating bactericidal antibodies whose level increased 8- to 10-fold after the immunization of monkeys in 2 and 3 injections. Similarity in the dynamics of the formation of bacteriolysins and antibodies to protein antigen, as determined in EIA, was noted. The vaccine was found to stimulate no cytotoxic anticerebral antibodies in the glia migration test, which was indicative of the safety of group B meningococcal vaccine.

Animals↗
PubMed1990

FITC-labeled lipopolysaccharide: use as a probe for liposomal membrane incorporation studies.

FITC-labeled LPS from Neisseria meningitidis can be used as a probe to follow the process of LPS incorporation into liposomal membrane and to study its interaction with a bilayer. The incorporation of FITC-LPS into the bilayer was proved by physicochemical methods as well as by liposomal LPS toxicity decrease in actinomycin D-sensitized mice. Fluorescence intensity increase was observed upon the insertion of FITC-LPS into the membrane of dehydration/rehydration vesicles and vesicles obtained by co-sonication of lipid suspension and FITC-LPS. Following FITC-LPS fluorescence polarization it was shown that the substance seems to be clusterized in the liposomal membrane starting from FITC-LPS/lipid molar ratio 1:800.

Animals↗
PubMed1990

[The sorption of a protein-polysaccharide complex isolated from Neisseria meningitidis serogroup B on aluminum hydroxide gels and the immunological activity of the sorbed preparations].

The protein-polysaccharide complex, isolated from group B N. meningitidis, is a variant of vaccine for the prophylaxis of group B N. meningitidis infection. In this investigation the influence of the complex of the physical properties of aluminium hydroxide gels, the amount of gel, pH and the duration of sorption on the process of sorption has been studied. Aluminium hydroxide has been shown to produce a stimulating effect on the response of mice to the polysaccharide and protein contained in the complex after immunization made in two injections. Gels with a smaller particle size have been found to possess greater adjuvant activity, as well as greater absorbing activity. The immunological activity of the complex, adsorbed ex tempore, has proved to be no different from that of the complex adsorbed in an hour.

Aluminum Hydroxide↗
PubMed1984

[Effect of Neisseria meningitidis on the humoral response of various strains of mice immunized with ram erythrocytes].

The capacity of heat-killed meningococci and the polysaccharide-protein-lipopolysaccharide fraction ( PPLF ) isolated from the microbial cell wall for changing nonspecific immunological reactivity was studied. In this investigation CBA mice with high response and C57BL/6 mice with low response to sheep red blood cells (SRBC) were used. Heat-killed N. meningitidis, serogroup A, and PPLF , serogroups A and B, were found to enhance and suppress humoral response to the heterologous antigen. The effect of modulation depended on the dose of the antigen, the serogroup of meningococci, the scheme of the experiment and the strain of mice. The immune response of the vaccinated animals to the heterologous antigen was characterized by the following stages: the state of the adjuvant effect was replaced by the state of temporary immunodeficiency and then by enhanced response to SRBC.

Animals↗
PubMedDate not supplied

[The immunological activity of Neisseria meningitidis lipo-oligosaccharide incorporated into liposomes].

Immune response to lipooligosaccharide (LOS), isolated from group B N. meningitidis cell wall, was studied after its incorporation into liposomes. The adjuvant effect produced by liposomal LOS, more pronounced in comparison with that produced by native LOS, was observed after the injection of the preparation by different routes (intravenous, intraperitoneal and subcutaneous injections), but the highest level of response was achieved after the intravenous and intraperitoneal injections of the preparation. Experiments aimed at the study of the dynamics of plaque-forming cells and the level of antibodies after intraperitoneal immunization of CBA mice with LOS revealed that immune response to liposomal LOS was more intense and prolonged than that to the free antigen. Liposomal LOS induced genetically nonrestricted and T-independent immune response. This fact was confirmed in experiments on mice having different haplotypes, such as CBA (k), C57BL/6 (b), BALB/c (d) and in nude mice with congenital thymic aplasia. In addition, liposomal LOS induced mainly the accumulation of IgM and IgG and did not produce the effect of immunological memory.

Animals↗
PubMedDate not supplied

[The effect of detergents on the immunological activity of the antigens of Neisseria meningitidis serogroup B[].

The complex study of the influence of detergents of different classes and aluminum hydroxide, a traditional adjuvant, on the immunological activity of individual N. meningitidis antigens (outer membrane proteins, polysaccharide B) and the complex preparation containing all these antigens revealed that changes in the antigenic and immunogenic properties of the antigens under study depended on the degree of their purification and the character of modifying substances. Aluminum hydroxide proved to be the most active adjuvant: it stimulated immune response to both outer membrane proteins and antigens of the protein-polysaccharide complex, while decreasing the antigenicity of outer membrane proteins and polysaccharide. Detergents increased the antigenicity of outer membrane proteins, both purified and, to a lesser extent, contained in the complex; still the immune response only to the purified preparation could be stimulated.

Aluminum Hydroxide↗