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The Inducible System: Antigens
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
An antigenic determinant is defined as a region of an antigenic molecule that fits into the combining site of an antibody. It comprises only a small part of the invading pathogen or molecuLe to which the immune system of the host has responded. The word determinant is usually used synonymously with the term epitope which literally means “surface shape” and refers to the site on the surface of the molecule to which the antibody binds. Short segments (i.e., polypeptides) of proteins or of polysaccharides may also serve as epitopes. Complex molecules such as proteins and polysaccharides may, therefore, have multiple determinants. The number of epitopes to which an animal responds, however, is usually fewer than the total number of potential epitopes of any protein or carbohydrate. At the same time, some epitopes are immunodominant and produce a stronger immune response than other epitopes on the same protein.
Modulating Cytolytic Responses to Infectious Pathogens
Published in Thomas F. Kresina, Immune Modulating Agents, 2020
Rebecca Pogue Caley, Jeffrey A. Frelinger
The CTL recognition of a virus-encoded peptide complexed to the MHC HC can result in the destruction of that infected cell, thereby stopping the viral replication cycle within the cell and limiting virus production in the host. The virus’s goal is to produce as many progeny as possible in order to increase the probability for transmission to the next host. Thus, if a viral population contains peptides which elicit strong immune responses, the CTL can easily destroy cells producing that strain of virus. As a result, the immune system selects against such strong immune response-inducing strains. Such selection results in the development of virus escape mutants and initiates the coevolution of virus and host. As a consequence of this warfare, many viruses have generated mechanisms to evade CTL immune response through interfering in one or more of the steps in normal peptide presentation. For example, a wild-type immunodominant peptide can be mutated in the virus such that the peptide is incapable of binding efficiently to the MHC class I heavy chain. Alternatively, changes in the amino acid sequence can occur in the region surrounding the epitope. Such changes may lead to a diminished ability for the proper epitope to be generated from the whole protein through altered proteolysis (discussed later).
Introduction: HLA Matching in Transplantation
Published in M. Kam, Jeffrey L. Bidwell, Handbook of HLA TYPING TECHNIQUES, 2020
Anomalies are attributed to incomplete sets of typing reagents, overinterpretation of DR "blanks" that in reality are undisclosed mismatches, and a lack of sensitivity in B cell typing technology. Which HLA region is immunodominant?
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).
COVID-19 vaccine: where are we now and where should we go?
Published in Expert Review of Vaccines, 2021
Saman Soleimanpour, Atieh Yaghoubi
The M protein with a molecular mass of 25 kDa is the most abundant trans-membrane glycoprotein of SARS-CoV, which has a role in virus assembly [78]. This protein contains three different domains, including a short N-terminal ectodomain, a triple-spanning transmembrane domain, and a large interior C-terminal domain. Evidence suggests that M proteins can induce the responses of the neutralizing antibodies. Moreover, an attenuated recombinant virus, which is encoded as M protein, can induce effective antibody responses in the host [79,80]. The recombinant M protein, expressed in Pichia Pastoris, also demonstrates proper potential in eliciting protective humoral responses relative to SARS-CoV [81]. Moreover, the data analysis suggests that the transmembrane domain of the M protein has a T cell epitope cluster, which can induce the powerful cellular immune response [81]. Furthermore, two main immunodominant epitopes of M protein are placed in the extreme N-terminal region (residues1-31) and the interior C-terminal region (residues132-161), respectively. M1-31 and M132-161 are the synthetic peptides derived from N-terminal and C-terminal epitopes, respectively. These two synthetic peptides show great ability in inducing the high titers of neutralizing the antibody responses in the animal models. All these data suggest that this highly conserved protein can be a suitable candidate antigen for developing the SARS-CoV-2 vaccine (Figure 2).
Understanding the relationship between norovirus diversity and immunity
Published in Gut Microbes, 2021
Lauren A. Ford-Siltz, Kentaro Tohma, Gabriel I. Parra
The identification and manipulation of immunodominant epitopes are important factors in designing a vaccine that is able to induce functional, protective antibodies against a foreign antigen.72 It was demonstrated that the emergence of the GII.4 New Orleans/2009 variant was associated with changes in the immunodominant antigenic site A, whereby ~40% of blockade antibodies from human outbreak sera were directed against this site.69 Similarly, using polyclonal guinea pig sera, our group showed that antigenic sites A and G from the GII.4 Sydney/2012 variant were both important immunodominant blockade sites.70 Whether these immunodominant sites can induce cross-protective antibodies against multiple strains or if these antibodies are variant-specific remains to be determined. For example, as antigenic site G is more conserved compared to the other major antigenic sites/motifs, antibodies targeting site G could potentially provide protection against multiple GII.4 variants. These immunodominant sites may potentially mask protective epitopes from the immune response as seen in other viruses (e.g. influenza and HIV).73–75