Latent persistence of specific antigens of the causative agent in the composition of circulating immune complexes in typhoid fever

This study revealed the presence of O-antigen of group D salmonellae and Vi-antigen in circulating immune complexes in patients with typhoid fever, bacteriologically confirmed (56 +/- 5.6% and 65 +/- 5.4% of cases, respectively) and not confirmed (15.5 +/- 5% and 39 +/- 7% of cases, respectively), in patients with diarrhea of nontyphoid etiology in the presence of negative results of the coagglutination test and in healthy persons. The level and dynamics of circulating immune complexes were established with respect to the antigens contained in these complexes. Altogether O- and Vi-antigens were detected in circulating immune complexes, respectively, in 92%, 96% and 94% of cases on weeks 1, 2 and 3 from the beginning of the disease, and in all cases on weeks 4 and 5, the antigens being determined together and separately. Thus, the latent persistence of S. typhi antigens as part of circulating immune complexes in the blood serum was established. The determination of such persistence is of great pathogenetic and diagnostic importance, which also applies to the early period of the disease. The use of such specific and sensitive method as the coagglutination test for this purpose accelerates and facilitates the diagnosis of typhoid fever.     

Proteomics analysis of the causative agent of typhoid fever

Typhoid fever is a potentially fatal disease caused by the bacterial pathogen Salmonella enterica serotype Typhi ( S. typhi). S. typhi infection is a complex process that involves numerous bacterially encoded virulence determinants, and these are thought to confer both stringent human host specificity and a high mortality rate. In the present study, we used a liquid chromatography-mass spectrometry (LC-MS)-based proteomics strategy to investigate the proteome of logarithmic, stationary phase, and low pH/low magnesium (MgM) S. typhi cultures. This represents the first large-scale comprehensive characterization of the S. typhi proteome. Our analysis identified a total of 2066 S. typhi proteins. In an effort to identify putative S. typhi-specific virulence factors, we then compared our S. typhi results to those obtained in a previously published study of the S. typhimurium proteome under similar conditions ( Adkins, J. N. et al. Mol. Cell. Proteomics 2006, 5, 1450-1461 ). Comparative proteomics analysis of S. typhi strain Ty2 and S. typhimurium strain LT2 revealed a subset of highly expressed proteins unique to S. typhi that were exclusively detected under conditions that are thought to mimic the infective state in macrophage cells. These proteins included CdtB, HlyE, and gene products of t0142, t1108, t1109, t1476, and t1602. The differential expression of T1108, T1476, and HlyE was confirmed by Western blot analysis. When our observations are taken together with the current literature, they suggest that this subset of proteins may play a role in S. typhi pathogenesis and human host specificity.     

Resistance to a causative agent of infection and immune response

An analytical literature review dealing with the problems of resistance to causative agents of infections. The review includes the data of experimental research, as well as the author's own immunological studies in children at the clinic of acute infections. Mechanisms of resistance at different phases of the infectious process, the multivalued role of Th1- and Th2-dependent responses in different infections, the role of vaccinal immunity in the resistance of children to the causative agents of vaccine-preventable infections (diphtheria and parotitis) are analyzed.     

Circulation of the causative agent of diphtheria in immune collectives

Prolonged observations on the spread of toxigenic C. diphtheriae carriership, made during a school year in 12 groups of immune children (3809 children), showed that the penetration of diphtherial infection could give rise to the outbreak of bacterial carriership, its level being as high as 20.9-35.1% of the total number of children in the group. The spread of bacterial carriership occurred during the first months after the penetration of the infection, achieving its peak, then followed the subsidence of the infection in the focus. Though some children in the group persistently released C. diphtheriae, almost no new cases of carriership were registered in spring. The highest spread of carriership (55.6-73%) was revealed in the first forms of boarding schools despite a higher level of antitoxic immunity in these children. Cases of the spontaneous cessation of carriership were observed. The spread and subsidence of carriership were determined by the presence or absence of a susceptible contingent. Tests on guinea pigs, carried out in the course of this study to determine the toxigenicity of C. diphtheriae, showed its variability.     

Characteristics of the immunocyte cooperation in 2 strains of mice opposite in their sensitivity to dermaphytoses during the immune response to antigens of the causative agent

C57BL/6 and BALB/c mice, opposite in their sensitivity to dermatophytic infections, show similar activity of phagocytes as regards their capacity for the destruction of injected conidia of dermatophytes, but differ in the changes of this activity after immunization with dermatophytic antigenic complexes (DAC). Shortly after the injection of the antigens, the lymphocyte-mediated suppression of the fungicidal activity of macrophages, caused by the interaction of DAC with intact T-lymphocytes, was detected in the animals of both strains. Later in C57BL/6 mice resistant to mycosis the formation of cell-mediated immunity to DAC occurs, with the simultaneous production of factor stimulating the fungicidal activity of macrophages. In BALB/c mice sensitive to mycosis the injection of DAC induces active antibody production, but not the formation of delayed hypersensitivity with the resulting stimulation of the fungicidal activity of phagocytes. The injection of DAC into mice of the above-mentioned strains induces changes, peculiar to each strain, in the mitogen-induced proliferation of spleen cells and in the character of immune response to sheep red blood cells. Differences in the influence of DAC on the induction of immune response in C57BL/6 and BALB/c mice are realized by cells belonging to the population of T-lymphocytes.     

The effect of immunostimulants on the resistance of white mice to the causative agent of typhoid fever

The influence of prodigiosan, salmosan, polyribonate and levamisole on the body nonspecific and specific resistance to S. typhi strain 4446 has been studied. Prodigiosan and salmosan have proved to be the most effective. The injection of these compounds simultaneously with typhoid vaccine (both chemical adsorbed vaccine and alcohol-treated vaccine, enriched with Vi-antigen) significantly increases the survival rate of immunized animals (by 35-45%), elevates the resistance index (1.5- to 2.3-fold) and the effectiveness index of the vaccine (17- to 32-fold) in comparison with the controls. Besides, prodigiosan and salmosan alone are capable of increasing nonspecific resistance to S. typhi strain 4446, which is manifested by an increase of the survival rate of stimulated animals by 61.87%. Proceeding from the results thus obtained, the possibility of good prospects for prodigiosan and salmosan in the prophylaxis of typhoid fever in humans may be inferred.     

Detection of the antigens of the causative agent of brucellosis by an immunoenzyme method

The conditions of the enzyme immunoassay for the detection of Brucella antigens have been selected, making it possible to detect these antigens both in solutions and in biological material within 3-4 hours. In guinea pigs infected with B. abortus 99 in a dose of 1,000 microbial cells, brucellar antigen has been detectable in the organs and blood serum of the animals as early as 24 hours after infection. This assay, if carried out under the optimal conditions, detects soluble brucellar polysaccharide antigen at a concentration of 1 ng/ml and Brucellae at a concentration of 5 X 10(4) microbial cells/ml in the presence of 200-fold surplus of other bacterial cells.     

Genomics of immune response to typhoid and cholera vaccines

Considerable variation in antibody response (AR) was observed among recipients of an injectable typhoid vaccine and an oral cholera vaccine. We sought to find whether polymorphisms in genes of the immune system, both innate and adaptive, were associated with the observed variation in response. For both vaccines, we were able to discover and validate several polymorphisms that were significantly associated with immune response. For the typhoid vaccines, these polymorphisms were on genes that belonged to pathways of polysaccharide recognition, signal transduction, inhibition of T-cell proliferation, pro-inflammatory signalling and eventual production of antimicrobial peptides. For the cholera vaccine, the pathways included epithelial barrier integrity, intestinal homeostasis and leucocyte recruitment. Even though traditional wisdom indicates that both vaccines should act as T-cell-independent antigens, our findings reveal that the vaccines induce AR using different pathways.     

Directing the immune response to carbohydrate antigens

Peptide mimetics may substitute for carbohydrate antigens in vaccine design applications. At present, the structural and immunological aspects of antigenic mimicry, which translate into immunologic mimicry, as well as the functional correlates of each, are unknown. In contrast to screening peptide display libraries, we demonstrate the feasibility of a structure-assisted vaccine design approach to identify functional mimeotopes. By using concanavalin A (ConA), as a recognition template, peptide mimetics reactive with ConA were identified. Designed peptides were observed to compete with synthetic carbohydrate probes for ConA binding, as demonstrated by enzyme-linked immunosorbent assay and isothermal titration calorimetry (ITC) analysis. ITC measurements indicate that a multivalent form of one particular mimetic binds to ConA with similar affinity as does trimannoside. Splenocytes from mimeotope-immunized mice display a peptide-specific cellular response, confirming a T-cell-dependent nature for the mimetic. As ConA binds to the Envelope protein of the human immunodeficiency virus, type 1 (HIV-1), we observed that mimeotope-induced serum also binds to HIV-1-infected cells, as assessed by flow cytometry, and could neutralize T-cell line adapted HIV-1 isolates in vitro, albeit at low titers. These studies emphasize that mimicry is based more upon functional rather than structural determinants that regulate mimeotope-induced T-dependent antibody responses to polysaccharide and emphasize that rational approaches can be employed to develop further vaccine candidates.     

Effect of a typhoid lipopolysaccharide on the primary and secondary immunological response to ram erythrocytes

The effect of typhoid bacterial lipopolysaccharide (LPS) on the primary and secondary response to sheep red blood cells was studied. LPS, injected simultaneously with the antigen, stimulated the synthesis of IgM and IgG, as well as the production of rosette-forming cells. When injected on days 2 and 3 after the secondary immunization, LPS induced the maximum stimulation of IgM, IgG and rosette-forming cells, while the injection of LPS prior to immunization induced immunosuppression which particularly affected IgG and rosette-forming cells.     

In vivo experimental modelling of the infectious process caused by stable L forms of the causative agent of typhoid

To simulate the infectious process and to study the persistence of L-forms, rabbits and guinea pigs were infected with S. typhi stable L-forms. The materials presented in this work indicate that both subconjunctival and intraperitoneal infection led to the development of the clinically indistinct, but morphologically pronounced pathological process with characteristic localization and typical changes in the gastrointestinal tract. The typical features of the process were the generalized immunomorphological reaction of the lymphoid apparatus with the appearance of light-colored reticulomacrophagal elements, the signs of the activation of humoral and cell-mediated immunity and the formation of small epitheloidocellular granulomas. The results of the investigation indicate that the stable cultures of S. typhi L-forms are highly pathogenic and capable of inducing the infectious process in experimental animals.     

Specific antigens of the causative agents and their antibodies in the circulating immune complexes in acute dysentery

The level of circulating immune complexes has been determined in 53 patients in the dynamics of the disease. For the first time circulating immune complexes have been found to contain Shigella sonnei K-antigen and Shigella flexneri O-antigen, as well as IgA, IgG and IgM to Shigella. Shigella antigens can be detected from the first week of the disease, and their occurrence does not depend on the level of circulating complexes in patients blood serum.     

Humoral immune response to filarial antigens in chyluria

Humoral immune parameters like total immunoglobulins and specific antibody levels in serum were studied in filarial chyluria patients. Mean serum IgG was significantly reduced in this group compared to normal controls, while IgA and IgM levels remained comparable to controls. Anti-filarial antibody titre as measured by enzyme-linked immunosorbent assay also was significantly reduced. However, the total and specific IgE antibody titre was similar to that of controls. Specific IgE contents of the patients’ sera could be related to their microfilaraemic status.