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An Introduction to the Immune System and Vaccines
Published in Patricia G. Melloy, Viruses and Society, 2023
Another critical immunology question is understanding how reinfection by the same pathogen is “remembered” by the adaptive immune system. A strong memory response is necessary to protect the body if a pathogen presents itself in the future. Antibodies are a part of that memory bank. There are five major kinds of antibodies in the body, also known as immunoglobulins (Ig). They include IgM, IgA, IgD, IgG, and IgE (MADGE acronym to remember) (Nicholson 2016). A molecule that is foreign to the body that can react with an antibody is known as an antigen. Immunologists also use the more specific term of “immunogen” as a molecule that reacts with an antibody and causes an immune response (Cruse and Lewis 2009). However, antigen is more commonly used. Any of the four major macromolecules in nature—carbohydrate, nucleic acid, protein, or lipid—could be an antigen (Coico and Sunshine 2015). These macromolecules can be quite large, however, so it is not the entire macromolecule involved in the antigen-antibody interaction. A short region of the antigen, known as an epitope, is considered the “antigenic determinant” (Cruse and Lewis 2009).
The Inducible System: Antigens
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Any molecule that will induce an immune response and interact specifically with the products of the induced immune response is an antigen, Immunogen is another term preferred by some for molecules that will induce such a response. Classically, antigens have been considered to consist of a hapten, which cannot induce an immune response by itself, and a carrier protein which will induce a response. An antigenic determinant, or epitope, is the site on an antigen to which the antibody binds. The three-dimensional shape, amino acid sequence, and ionic charge of the antigen are all crucial to antibody binding. T cell receptors bind to protein fragments presented on the surface of MHC proteins. Therefore, the TCR recognizes two molecules at once: the MHC protein and the presented antigen-fragment.
Cryptococcosis
Published in Rebecca A. Cox, Immunology of the Fungal Diseases, 2020
Humoral and cell-mediated immune responses against C. neoformans antigens can be stimulated providing the proper conditions are employed. The route of administration, the dose, and nature of the immunogen, all affect the kind and level of the resulting immune response.
Research progress on substitution of in vivo method(s) by in vitro method(s) for human vaccine potency assays
Published in Expert Review of Vaccines, 2023
Xuanxuan Zhang, Xing Wu, Qian He, Junzhi Wang, Qunying Mao, Zhenglun Liang, Miao Xu
Potency is ‘The measure of the biological activity using a suitably quantitative biological assay, based on the attribute of the product which is linked to the relevant biological properties’ [4,5]. The potency of a final lot, which is directly associated with its efficacy, is a critical quality attribute (CQA) for vaccine quality control and release [6]. Typically, vaccine potency assays include in vivo and in vitro methods. In vivo assays require the assessment of protection against a challenge or antibody detection after immunization of animals. In vitro assays generally require the determination of the vaccine immunogen content. Vaccine potency assays are selected depending on vaccine types. In general, the in vitro virus titration method or bacterial content determination is employed for attenuated live vaccines; in vivo assays are adopted for assessing inactivated vaccines; the contents of major immunogenic components are determined for subunit vaccines; in vitro or in vivo assays are utilized for nucleic acid or viral vector vaccines [7–10]. During the initial stage of recombinant vaccine, in vivo assays are used, while confirming the correlation between in vitro and in vivo assays, in vivo assays can be substituted by in vitro assays.
Nanotechnology-based promising strategies for the management of COVID-19: current development and constraints
Published in Expert Review of Anti-infective Therapy, 2022
Mahendra Rai, Shital Bonde, Alka Yadav, Yulia Plekhanova, Anatoly Reshetilov, Indarchand Gupta, Patrycja Golińska, Raksha Pandit, Avinash P. Ingle
The nanoparticles used for vaccine delivery typically have three different parts: (i) the material(s) that the nanoparticles are composed of natural polymers, synthetic polymers, inorganic substances, lipids, etc. (ii) immunogen or immunomodulatory agents such as antigens, DNA vaccines, siRNA, cytokines, etc. (iii) targeting and immune-stimulatory ligands that are added to the particle surface including immune specific ligands, tissue-specific ligands, and pathogen-associated molecular patterns (PAMPs). The composition of nanomaterial play an important role in transport, cellular uptake, and intracellular trafficking of the nanoparticles, and also, its biodegradability and biocompatibility. Likewise, it plays an important role in pharmacokinetic properties, the discharge rate, biodistribution, and bioavailability of the immunogen. The immunogen, which is a key part of a nano-based vaccine, might be attached to the nanoparticles in three different ways: (i) conjugation (covalent binding), (ii) adsorption (on the surface of the nanoparticles), and (iii) encapsulation (within the nanoparticles). The incorporation of PAMP ligands to the vaccine formulations can provoke inflammatory responses by stimulating pathogen recognition receptors (PRRs). These receptors are mainly expressed on immune cells together with macrophages, dendritic cells, and B cells. Toll-like receptors (TLRs) are a main cluster of PRRs. TLR ligands, such as CpG DNA, lipopolysaccharide (LPS), monophosphoryl lipid A, and muramyl peptides are strong adjuvants that are useful in a variety of vaccine formulations.
Human lymph node immune dynamics as driver of vaccine efficacy: an understudied aspect of immune responses
Published in Expert Review of Vaccines, 2022
Eirini Moysi, Robert M. Paris, Roger Le Grand, Richard A. Koup, Constantinos Petrovas
Vaccination remains today one of the most cost-effective public health interventions available against infectious diseases [1], resulting in improvements in morbidity and mortality indices, especially amongst infants as well as quality-adjusted life year improvements in adults [1]. Despite these advances, non-protective immunologic responses to vaccination remain an important consideration for both routine vaccination regimens (2–10% of vaccinated healthy individuals fail to mount responses) [2] and clinical development of new vaccines. To tackle this problem, vaccine research efforts have focused on two major roadmaps: improving immunogen design and delivery and a better understanding of the complex immune dynamics that govern protective and/or poor immune responses (Figure 1).