Production Of Memory Cells Research Articles

An Immunoinformatic Approach to Designing a Multi-epitope Vaccine against Helicobacter pylori with the VacA Toxin and BabA Adhesion

Objective: Helicobacter pylori, as a carcinogen, has been related to the development of gastric cancer, particularly in developing countries. The main challenge with therapy is the recurrence of antibiotic-resistant bacteria, and vaccination is still a problem. Therefore, the objective of the current study was to rationally design a multi-epitope vaccine using two immunogenic proteins found in H. pylori. Methods: Promising epitopes for the Leb-binding adhesin A (BabA) and vacuolating cytotoxin (VacA) proteins were characterized through an immunoinformatics approach. Epitope-rich fragments were selected based on high-binding affinities with HLA classes I and II to be specifically presented to B and T lymphocytes and to selectively elicit both humoral and cellular immune responses. Results: Six constructs were planned by fusing these fragments in different arrangements with the help of GPGPG linkers. The most stable three-dimensional structure was found in Construct 6 during molecular dynamics. To improve immunogenicity and stability, an adjuvant called human β- defensin 2 (hBD-2) was joined to the N-terminus of Construct 6. Following molecular docking, the final vaccine reacted appropriately with each toll-like receptor 2 (TLR-2), TLR3, and TLR-4. The final DNA sequence was optimized for expression in E. coli K12 and in silico cloned into a pET-28a(+) plasmid. As a result of the vaccination in silico, substantial responses were developed against H. pylori. Conclusion: According to the immune response simulation, activated B and T lymphocytes and memory cell production increased. Macrophages and dendritic cells proliferated continuously, and IFN-γ and Cytokines, such as IL-2 were raised.

Designing a Multiepitope Vaccine against the Foodborne Pathogenic Bacteria Listeria monocytogenes Using Subtractive Immunoinformatics Approaches.

Listeria monocytogenes, a Gram-positive bacterium, is a prominent foodborne pathogen that causes listeriosis and poses substantial health hazards worldwide. The continuing risk of listeriosis outbreaks underlies the importance of designing an effective prevention strategy and developing a robust immune response by reverse vaccinology approaches. This study aimed to provide a critical approach for developing a potent multiepitope vaccine against this foodborne disease. A chimeric peptide construct containing 5 B-cell epitopes, 16 major histocompatibility complex I (MHC-I) epitopes, and 18 MHC-II epitopes were used to create a subunit vaccination against L. monocytogenes. The vaccine safety was evaluated by several online methods, and molecular docking was performed using ClusPro to determine the binding affinity. Immune simulation was performed using the C-ImmSimm server to demonstrate the immune response. The results validated the antigenicity, non-allergenicity, and nontoxicity of the chimeric peptide construct, confirming its suitability as a subunit vaccine. Molecular docking showed a good score of 1276.5 and molecular dynamics simulations confirmed the construct's efficacy, demonstrating its promise as a good candidate for listeriosis prophylaxis. The population coverage was as high as 91.04% with a good immune response, indicating good antigen presentation with dendritic cells and production of memory cells. The findings of this study highlight the potential of the designed chimeric peptide construct as an effective subunit vaccine against Listeria, paving the way for future advances in preventive methods and vaccine design.

Trans-Cinnamaldehyde Primes More Robust Channel Catfish Immune Responses to Edwardsiella ictaluri Infection.

Infection with Edwardsiella ictaluri, a causative agent of enteric septicemia of catfish, threatens profitable catfish production through inventory losses. We previously demonstrated that trans-cinnamaldehyde (TC) enhances the survival of catfish following E. ictaluri infection. The present study was conducted to investigate catfish immune responses to TC feeding and E. ictaluri infection. The expression of 13 proinflammatory, innate, and adaptive immune-related genes was evaluated over time in two sets of experiments using real-time polymerase chain reaction (PCR). In the first experiment, catfish were fed a basal diet with or without TC supplementation, while in the second they were fed a TC-supplemented or normal diet followed by infection with E. ictaluri. The catfish group infected with E. ictaluri and fed a TC-diet showed significant changes in the expression of innate and adaptive immune-related genes compared to control group. At 21 and 28 days post-infection, recovered fish showed significant increases in the expression of IgM in the anterior kidney and spleen. These results suggest that the supplemental dietary intake of TC can improve the immune status of catfish via engaging innate and adaptive immune responses and the production of memory cells in immunocompetent tissues. Together, this study provides an important foundation for the potential application of TC as an antimicrobial alternative in aquaculture.

The Broad Immunomodulatory Effects of IL-7 and Its Application In Vaccines.

Interleukin-7 (IL-7) is produced by stromal cells, keratinocytes, and epithelial cells in host tissues or tumors and exerts a wide range of immune effects mediated by the IL-7 receptor (IL-7R). IL-7 is primarily involved in regulating the development of B cells, T cells, natural killer cells, and dendritic cells via the JAK-STAT, PI3K-Akt, and MAPK pathways. This cytokine participates in the early generation of lymphocyte subsets and maintain the survival of all lymphocyte subsets; in particular, IL-7 is essential for orchestrating the rearrangement of immunoglobulin genes and T-cell receptor genes in precursor B and T cells, respectively. In addition, IL-7 can aid the activation of immune cells in anti-virus and anti-tumor immunity and plays important roles in the restoration of immune function. These biological functions of IL-7 make it an important molecular adjuvant to improve vaccine efficacy as it can promote and extend systemic immune responses against pathogens by prolonging lymphocyte survival, enhancing effector cell activity, and increasing antigen-specific memory cell production. This review focuses on the biological function and mechanism of IL-7 and summarizes its contribution towards improved vaccine efficacy. We hope to provide a thorough overview of this cytokine and provide strategies for the development of the future vaccines.

So Selective

Restricted B cell signaling in the areas responsible for immune memory cell production promotes affinity maturation.

Diversity in T Cell Memory: An Embarrassment of Riches

The adaptive immune response meets the needs of the organism to generate effector cells capable of controlling pathogens but also leads to production of memory cells, which mediate more effective protection during rechallenge. In this review, we focus on the generation, maintenance, and function of memory T cells, with a special emphasis on the increasing evidence for great diversity among functional memory T cell subsets.

Modeling Cyclic Waves of Circulating T Cells in Autoimmune Diabetes

Type 1 diabetes (T1D) is an autoimmune disease in which immune cells, notably T lymphocytes, target and kill the insulin‐secreting pancreatic beta cells. Elevated blood‐sugar levels and full‐blown diabetes result once a large enough fraction of these beta cells has been destroyed. Recent investigation of T1D in animals, namely nonobese diabetic (NOD) mice, has revealed large cyclic fluctuations in the levels of T cells circulating in the blood, weeks before the onset of diabetes [J. D. Trudeau, C. Kelly‐Smith, C. B. Verchere, J. F. Elliott, J. P. Dutz, D. T. Finegood, P. Santamaria, and R. Tan, J. Clin. Invest., 111 (2003), pp. 217–223], but the mechanism for these oscillations is unclear. We here describe a mathematical model for the immune response that suggests a possible explanation for the cyclic pattern of behavior. We show that cycles similar to those observed experimentally can occur when activation of T cells is an increasing function of self‐antigen level, whereas the production of memory cells declines with that level. Our model extends previous theoretical work on T‐cell dynamics in T1D [A. F. M. Marée, P. Santamaria, and L. Edelstein‐Keshet, Int. Immunol., 18 (2006), pp. 1067–1077], and leads to interesting nonlinear dynamics, including Hopf and homoclinic bifurcations in biologically reasonable regimes of parameters. The model leads to the following explanation for cycles: High rates of beta‐cell death, and corresponding elevation of self‐antigen, shut off memory‐cell production, leading to a gap in the population of activated T cells. Once peptide has been cleared by nonspecific mechanisms, the memory pool is renewed, and the cyclic behavior results.

Acutely dysregulated, chronically disabled by the enemy within: T‐cell responses to HIV‐1 infection

Human immunodeficiency virus (HIV) infection causes chronic progressive immunodeficiency and immune dysregulaton. Although simple depletion of the major target of HIV infection, the CD4+ T cell, can explain much of the immunosuppression seen, there are multiple other factors contributing to the immune dysregulation. CD4+ T-cell depletion induces a range of homeostatic mechanisms that contribute to immune activation and cell turnover, providing a milieu conducive to further viral replication and cell destruction, resulting in functional defects in various lymphoid organs. These changes are progressive and in turn compromise the homeostatic processes. Further, the infection, like any other viral infection, provokes an active immune response consisting of both CD4+ and CD8+ T-cell responses. Both appear compromised, displaying aberrant memory cell production. While some of these defects result from viral variation and the chronicity of antigen presentation, other defects of memory cell production appear very early during the primary immune response limiting the viral specific T-cell responses from the outset. This, combined with the ability of the virus to escape any successful immune responses, results in an attenuated immune response that eventually becomes exhausted, characterized by progressive deficits in T-cell repertoire. Furthermore, negative regulatory mechanisms that normally control the immune response may be aberrantly invoked, perhaps directly by the virus, further compromising the efficacy of the immune response. Rational design of effective immunotherapies depends on a clear understanding of the processes compromising the immune response to HIV.

Recycling Probability and Dynamical Properties of Germinal Center Reactions

We introduce a new model for the dynamics of centroblasts and centrocytes in a germinal center. The model reduces the germinal center reaction to the elements considered as essential and embeds proliferation of centroblasts, point mutations of the corresponding antibody types represented in a shape space, differentiation to centrocytes, selection with respect to initial antigens, differentiation of positively selected centrocytes to plasma or memory cells and recycling of centrocytes to centroblasts. We use exclusively parameters with a direct biological interpretation such that, once determined by experimental data, the model gains predictive power. Based on the experiment of Han et al. (1995b) we predict that a high rate of recycling of centrocytes to centroblasts is necessary for the germinal center reaction to work reliably. Furthermore, we find a delayed start of the production of plasma and memory cells with respect to the start of point mutations, which turns out to be necessary for the optimization process during the germinal center reaction. The dependence of the germinal center reaction on the recycling probability is analysed.

Effects of human recombinant interleukin-2 on resistance, and on the humoral and cellular response of rabbits infested with adult Ixodes ricinus ticks

Rabbits were treated with subcutaneous injections of ten doses of 5 × 10 3 units of human recombinant interleukin-2 (IL-2) during a first infestation with five adult pairs Ixodes ricinus per rabbit, while untreated controls were infested by either five (direct control) or 25 pairs (resistant control) per rabbit. During the second infestation with 25 pairs per rabbit in each group, rabbits treated with IL-2 became more resistant than the rabbits in the two untreated control groups. Stronger resistance was manifested by lower engorgement and egg laying weights, and by smaller numbers of normally fed or ovipositioning ticks. IL-2 treatment had no significant effects on the rabbit anti-tick antibody production and the lymphocyte proliferation to a salivary gland extract (SGE). By contrast. the highest cutaneous responses to SGE were observed in the IL-2 treated group. IL-2 may increase rabbit cell-mediated immunity, and stimulate an increase in the production of memory cells during the induction phase of the immune response (first infestation), allowing the development of a strong resistance in lightly infested rabbits.

Germinal Centers and the B Cell System VIII. Functional Characteristics and Cell Surface Markers of Germinal Center Cell Subsets Differing in Density and in Sedimentation Velocity

Germinal center cells from the rabbit appendix were fractionated by velocity sedimentation and isopycnic gradient centrifugation. Subsets were analysed with respect to cell size and surface markers, and were functionally characterized by testing the capacities for primary antibody synthesis, memory cell production, and formation of new germinal centers in an autologous transfer system. The migratory behaviour of the germinal center cell subsets within the spleen of homologous recipients was also studied using autoradiography. Both cell fractionation methods yielded a separation of large and small cells. Surface immunoglobulin and C 3 receptors were equally expressed on germinal center cells differing in size and density. The different subsets were also equally capable in giving rise to IgM-antibody-forming cells and memory cells upon antigenic stimulation. Furthermore, large germinal centers were newly formed in the spleen of the recipients, irrespective of the cell subset injected. It was concluded that the results do not support the hypothesis that, inside germinal centers, the differentiation of large lymphoid cells (centro-blasts) into small centrocytes also implies a maturation process. Subsets of germinal center cells, however, showed a different and characteristic migratory behaviour: while small cells migrated preferentially to the corona of lymphocytes in spleen follicles, large, light cells showed an affinity for the germinal center area. We postulate that, upon stimulation, immature B cells develop an affinity for the germinal center microenvironment, to participate in a germinal center reaction.

Germinal centres and the B cell system. IV. Functional characteristics of rabbit appendix germinal centre (-derived) cells.

Functional capacities of rabbit appendix germinal centre cells were tested in appendectomized, 450 rads X-irradiated rabbits, reconstituted with autologous appendix germinal centre cells, which are obtained by mechanical separation--"stripping"--of the appendix. For comparison, functional capacities of appendix germinal centre derived cells were tested in rabbits, 450 rads X-irradiated with the appendix shielded. In both types of experimental systems, slow restoration of primary IgM responsiveness to Salmonella Java paratyphi-B (PAR) was observed; in contrast, the capacity for memory cell production (of both mu and gamma-type) to PAR was restored very early in both systems. These results suggest germinal centres to be antigen dependent microenvironments for selective as well as non-selective amplification of immature B cells, which after subsequent maturation become part of the pool of either memory or virgin mature B cells respectively.

Optimal strategies in immunology

After a first encounter with most antigens, the immune system responds to susequent encounters with a faster, more efficient and more strenuous antibody response. The memory of previous antigen contacts is carried by lymphocytes. Expanding on the model developed in Part 1 of this paper, we examine the optimal strategy available to the immune system for B memory cell production. We again find that the strategy should be of the bang-bang variety. The model we consider assumes that antigen triggers a subpopulation of B-lymphocytes. These triggered lymphocytes can proliferate and secrete modest amounts of antibody, or differentiate into non-dividing plasma cells which secrete large amounts of antibody, or differentiate into non-antibody secreting memory cells. Given injections of antigen at two widely spaced times we compute the strategy which minimizes a linear combination of the primary and secondary response times. We find that for all biologically reasonable parameter values the best strategies are ones in which memory cells are produced at the end of the primary response. Exerimental results which bear on the actual strategies employed are discussed.

Enhancement of Reaginic and Hemagglutinating Antibody Production by an Extract of Bordetella Pertussis Containing Histamine Sensitizing Factor

The effect of an extract containing the histamine-sensitizing factor (HSF) of Bordetella pertussis on the immune response of mice to ovalbumin was investigated with respect to dose of antigen and adjuvant. Of particular interest was the enhancement of reaginic antibody production. In comparison to the Al(OH)3 induced production of reaginic antibody where low doses of antigen and adjuvant yield high titers of reagin, the HSF extract demonstrated optimal adjuvant activity at high doses of both adjuvant and antigen. The reaginic antibody response was maximal usually by 2 to 3 weeks post-immunization and persisted for long periods of time. The hemagglutinating antibody response was maximal at 8 to 10 weeks post-immunization. The initial treatment of mice with HSF extract plus antigen resulted in the production of memory cells since a subsequent immunization with ovalbumin alone evoked a secondary reaginic response. These observations may have implications in clinical allergy since substances similar to the pertussis factor might be produced by other microbial organisms and these substances could modulate the immunologic response of individuals to common allergens.

Pathogenesis of rinderpest virus infection in rabbits. II. Effect of rinderpest virus on the immune functions of rabbits.

Rinderpest virus infection was shown to induce marked suppression of both humoral antibody response and cell-mediated immunity in rabbits. The virus exhibited a suppressive effect on primary antibody response as indicated by a decrease in numbers of plaque-forming cells (immunoglobulin [Ig]M) and hemagglutinating antibody titers of both IgM and IgG types to sheep red blood cells, whereas there was no detectable effect of the virus on the production of memory cells. Virus-induced suppression of cell-mediated immunity was demonstrated by a decreased rate of proliferative response of peripheral lymphocytes to phytohemagglutinin stimulus and by a depression of delayed-type skin reactions to purified protein derivative. Such suppressive effects were indicated to persist for 14 days or longer. Alteration in phagocytic activity of the reticuloendothelial system was not observed. The relevance of the virus-induced histological lesions in the lymphoid tissues to the virus-induced immunosuppression was discussed.

Mechanism of adjuvant activity of poly A:U on antibody responses to hapten-carrier conjugates

The adjuvant action of poly A:U has been analyzed in a system measuring humoral immune responses to hapten-carrier conjugates in mice. Administration of poly A:U at the time of primary immunization with 2,4-dinitrophenyl (DNP)-keyhole limpet hemocyanin (KLH) shortens the induction period for, and heightens the magnitude of peak anti-DNP antibody and specific memory cell production. In order to define the cellular locus of poly A:U action, the effect of this adjuvant on adoptive secondary anti-DNP antibody responses was studied. Spleen cells from DNP-KLH-primed donors, which normally fail to develop adoptive secondary anti-DNP responses to a heterologous conjugate such as DNP-bovine gamma globulin (BGG), can be stimulated to do so when an appropriate dose of poly A:U is administered with DNP-BGG. The capacity for poly A:U to exert this effect requires the presence of T lymphocytes, since depletion of such cells by treatment of the donor cell inoculum with anti-θ serum and complement in vitro prior to adoptive transfer abrogates the response to DNP-BGG plus poly A:U. Moreover, evidence is presented that demonstrates that poly A:U exerts its adjuvant action on the small number of unimmunized BGG-specific T lymphocytes in the donor cell inoculum. This conclusion derives from the failure of poly A:U to augment adoptive secondary anti-DNP responses to the DNP derivative of a nonimmunogenic copolymer of d-glutamic acid and d-lysine ( d-GL) for which there are few or no specific, functional T cells.

Time Relationships Between Injection of Antigen and Adjuvant I. Adjuvancy of Bordetella pertussis Given at Various Times Before the Primary Antigenic Stimulus

The adjuvant activity of Bordetella pertussis was investigated, both at the cellular and humoral levels, when the bacterial adjuvant was administered at various times before the primary antigenic stimulus of both 8 x 10(6) and 4 x 10(8) sheep erythrocytes. In all experiments, both adjuvant and erythrocyte antigen were given intraperitoneally. Adjuvant activity was measured on the basis of the primary immune response and on the degree of priming for the secondary immune reaction. A maximal effect on the primary immune response was found in mice which had received B. pertussis vaccine simultaneously with the erythrocyte antigen. A significant degree of adjuvancy was also demonstrable when B. pertussis vaccine was administered within a period of 48 hr before antigen. Adjuvant effectiveness was less as the time interval between the injection of antigen and adjuvant increased. The process of priming for the secondary response, however, was found to be equally affected when the adjuvant was given either simultaneously with the antigen or 12, 24, and 48 hr before sheep erythrocytes. On the basis of these and previous findings, it is suggested that adjuvancy of B. pertussis is caused chiefly by additional recruitment of responding cells. It is also suggested that memory-cell production may develop concurrently with, but independently of, the cellular proliferative events which lead to antibody formation during the primary immune response.