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Background
Published in Mesut Karahan, Synthetic Peptide Vaccine Models, 2021
In general, the adaptive immune system is divided into two different categories, cellular and humoral (Skwarczynski and Toth 2016). Also, cells of this adaptive immune system respond to specific regions of infectious agents known as epitopes (peptides and peptide vaccines are most commonly used in the adaptive immune system). One or more epitopes are located in various regions of infectious agents, a larger molecule known as an antigen, and these antigens are highly related to stimulating the immune system. Humoral immune responses are very important and basically these responses are dependent on the action of glycoproteins, antibodies secreted from B cells by binding to specific epitopes by B cell-specific receptors on the cell surface, and upon the binding of the B cell receptor to a matching epitope; B cells can mature into plasma. B cells formed in this way provide an important protection by starting to secrete epitope-specific antibodies that will protect an individual from infectious diseases (Siegrist 2013). Cellular immune responses are based on the action of T immune cells. All these cells contain histocompatibility complex class I (MHC-I) molecules in their nuclear activities. When an intracellular infectious agent is formed near the cell membrane, cells may be present on surface linear epitopes of these infectious agents complexed with MHC-I because this molecule is responsible for stimulating the immune system against infectious (Moser and Leo 2010) (Figure 1.1).
Antibodies and Antisera
Published in Lars-Inge Larsson, Immunocytochemistry: Theory and Practice, 2020
The foregoing discussion concerned the biochemical binding reaction between the antigen-combining site on an antibody and its epitope on the antigen. We have emphasized that the antibody does not recognize the entirety of most antigens, but reacts only with a characteristic region or site (epitope or antigenic region). Usually, this region consists of three to eight amino acids. Designation of an epitope is convenient, but it should be remembered that the antibody and the antigen are flexible and that recognition is probably of shapes rather than of amino acids per se. Thus, in many of the tri- to octapeptide sequences, some constituent amino acid side chains are more critical than others. Substitution of less important amino acids may still allow recognition, perhaps with a lower avidity. Chemically introduced modifications (e. g., fixation-induced) will also variably affect the recognizability of the epitope by the antibody, by influencing either more or less important amino acid components or by changing the overall conformation or molecular mobility of the epitope. Despite these often unpredictable limitations, immunocytochemistry, and particularly region-specific immunocytochemistry, is exceedingly potent in localizing chemically defined molecules in tissue specimens.
Modulating Cytolytic Responses to Infectious Pathogens
Published in Thomas F. Kresina, Immune Modulating Agents, 2020
Rebecca Pogue Caley, Jeffrey A. Frelinger
Other viral mechanisms of immune system evasion exist, including viral latency; down-regulation of MHC class 1, or adhesion molecules; and replication in “immune-privileged” sites [1]. Our focus in this review is on alteration of viral epitopes to induce stronger, more effective CTL responses while retaining activity toward the original virus-encoded peptide. In some cases, the coevolution of mammals with viruses and intracellular bacteria has resulted in pathogen genomes lacking strong immunodominant epitopes. The mammalian host is consequently hindered in its ability to mount a strong, specific, effective, and protective response quickly. A method to improve on these moderate to weak epitopes in viruses, intracellular bacteria, and tumors is imperative in order to generate epitopes which can induce enhanced CTL activity. Epitope improvement can lead to more direct and efficient immune responses in vaccine development and bypasses the higher costs, side effects, and lower immunogenicity associated with some attenuated or heat-killed virus-based vaccines.
Recent trends in next generation immunoinformatics harnessed for universal coronavirus vaccine design
Published in Pathogens and Global Health, 2023
Chin Peng Lim, Boon Hui Kok, Hui Ting Lim, Candy Chuah, Badarulhisam Abdul Rahman, Abu Bakar Abdul Majeed, Michelle Wykes, Chiuan Herng Leow, Chiuan Yee Leow
An epitope is the part of an antigen that is recognized by the adaptive immune system. It binds to specific receptors including antibodies, MHC molecules and T-cell receptors [28]. The binding portion of an antibody is termed a paratope. Epitopes can be either continuous or discontinuous. A continuous or linear epitope is a relatively short (usually 5–6) amino acid sequences recognized by the paratope of a corresponding antibody. In contrast, a discontinuous epitope consists of non-adjacent segments of amino acids, not necessarily from one chain, which form a specific 3D structure, which can also be recognized by antibodies. Since discontinuous epitope arises from a specific 3D fold, it is also known as conformational epitope. Notably, epitopes recognized by B-cell epitopes may contain lipids, nucleic acids or carbohydrates, giving resultant antibodies a vast repertoire while T-cell epitopes are usually peptide fragments. The investigation, identification and development of epitopes are crucial in promoting the advancement of diagnostics and therapeutics [110].
Reverse engineering approach: a step towards a new era of vaccinology with special reference to Salmonella
Published in Expert Review of Vaccines, 2022
Shania Vij, Reena Thakur, Praveen Rishi
Epitope-based vaccine refers to a single specific potent epitope or a collection of multiple epitopes (B cell epitopes, cytotoxic- and helper-T cell epitopes), which may be derived from one or more pathogenic microorganisms. Although epitope-based vaccines exhibit several advantages over the conventional vaccines but are less immunogenic in nature. This drawback can be overcome by conjugating antigenic epitopes with certain adjuvants or built-in adjuvants (e.g. some carrier proteins or new biomaterials) with specific properties, such as biocompatibility, immunologic specificity, non-toxicity, and the ability to vastly improve the immune response of epitope vaccines [133]. In this section, along with describing the examples of epitopes-based Salmonella vaccines, details of the adjuvants and linkers have also been provided.
B Cell Response to Vaccination
Published in Immunological Investigations, 2021
Immunodominance is generally recognized as the immune response is focused on only a few of the many potential epitopes, and it happens to both T cells and B cells (Frank 2002). The epitopes dominating the responses are called the immunodominant epitopes, whereas those who are not targeted or targeted to a lesser degree are termed subdominant epitopes (Akram and Inman 2012). Evidence for B cell/antibody immunodominance has been extensively reported. The durable humoral responses against viruses such as influenza or HIV are usually dominated by antibodies focused on the variable and mutable epitopes; on the other hand, immunodominance determines which epitopes of viruses are favored to vary antigenically in order to escape immune pressure (Altman et al. 2018). Thus, to overcome immunodominance and elicit the immune responses targeting both dominant and subdominant epitopes are the goals in designing effective vaccines against highly variable and mutable viruses such as HIV and influenza. B cells compete with each other for antigens at different stages. Immunodominance results from a few dominant winner clones beating the other loser clones to survive into the memory compartment. The factors affecting B cell competence and immunodominance are complex. Epitope accessibility, precursor frequency, antigen affinity, T-cell help, and previous antigen exposure all have been shown to influence B cell/antibody immunodominance (Abbott and Crotty 2020; Abbott et al. 2018; Akram and Inman 2012).