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Other Double-Stranded DNA Viruses
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
In parallel, Brumfield et al. (2009) investigated the ultrastructural changes of STIV using both scanning and transmission electron microscopy by a near-synchronous STIV infection. The authors noticed assembly of the STIV particles—including particles lacking DNA—and formation of pyramid-like projections from the cell surface prior to cell lysis. These projections appeared to be caused by the protrusion of the cell membrane beyond the bordering surface protein layer (S-layer) and were thought to be sites at which progeny virus particles were released from infected cells.
Basic Microbiology
Published in Philip A. Geis, Cosmetic Microbiology, 2020
S-layer—Some bacteria have an external covering comprising glycoproteins, which is part of bacterial cell wall components. S-layers provide structural integrity as well as facilitate adhesion to surfaces and in some cases help avoid host immune responses.
Campylobacter
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Hongsheng Huang, Catherine D. Carrillo, Emma Sproston
Campylobacters must possess other mechanisms that enable them to successfully compete and survive under the stressful conditions encountered in the host intestines, and evade the host's defense system (76). These include numerous Campylobacter cellular responses, for example, the ability to acquire restricted nutrients such as iron, inhibition of binding by mucin, and methods to counteract the host's immunity (76,91,96). For example, the surface layer (S-layer) mediates resistance to phagocytosis and serum killing that aids in defense against the host's immune response (29,76).
Molecular insights into probiotic mechanisms of action employed against intestinal pathogenic bacteria
Published in Gut Microbes, 2020
Winschau F. van Zyl, Shelly M. Deane, Leon M.T. Dicks
Another example of a putative competitive exclusion factor is the collagen-binding protein of L. fermentum. Heinemann et al.95 characterized the collagen surface-binding protein of L. fermentum RC-14, which inhibited the adherence of E. faecalis 1131. Other studies have demonstrated the role of surface layer (S-layer) extracts in the prevention of pathogens from attaching to, and thus colonizing, IECs.96,97 Chen et al.96 showed that S-layer proteins anchored on the cell surface of Lactobacillus crispatus ZJ001 were responsible for competitive exclusion of S. typhimurium and EHEC. Similar results were recorded by Johnson-Henry et al.97 The authors showed that S-layer protein extracts from Lactobacillus helveticus R0052 inhibited the adhesion of E. coli O157:H7 to Caco-2 cells. S-layer proteins are highly hydrophobic and it was suggested that pathogen adherence inhibition was mediated by hydrophobic group interactions as opposed to adhesion-receptor interactions.
Research Progress in Bioinspired Drug Delivery Systems
Published in Expert Opinion on Drug Delivery, 2020
Qirong Tong, Na Qiu, Jianbo Ji, Lei Ye, Guangxi Zhai
Bacterial components capable of acting as a carrier include the S layer, bacterial ghost (BG), outer membrane vesicle (OMV), and endospores. The S layer is the surface coating of bacteria, present in almost all bacteria. It possesses the ability of self-assembly, as well as predictable physical and chemical properties; hence, it can be physically or chemically wrapped around solid lipid NPs to achieve targeted delivery, offering further possibilities for surface modifications [129]. BG is an empty non-denaturing envelope originating from gram-negative bacteria. It demonstrates a high-loading capacity, and the drug can be loaded on the inner surface by electrostatic interaction. This type of carrier has excellent targeting capabilities toward several cancer cells, with the same excellent immunity as live bacteria. The OMV contains bacterial membrane proteins, therapeutic markers, as well as pathogenic factors, and can be used in vaccines for the treatment of viral and bacterial infections [130]. The OMV can be used to modify immunosuppressive drug-loaded liposomes [131]. Bacterial endospores are produced only in certain bacteria with spore-specific genes and can deliver therapeutic proteins, anticancer drugs, and cytotoxic groups. Reportedly, the intratumoural injection of endospores can achieve tumor regression [132].
Anthrax prevention through vaccine and post-exposure therapy
Published in Expert Opinion on Biological Therapy, 2020
Manish Manish, Shashikala Verma, Divya Kandari, Parul Kulshreshtha, Samer Singh, Rakesh Bhatnagar
Nanobodies (Nbs) are single-domain and hydrophilic nature antibody variants produced by camels and llamas that have variable antigen-binding domains, two constant domains (CH2 and CH3), a hinge region and an antigen-binding or variable heavy chain domain but devoid of light-chains [177]. Besides being less toxic, immunogenic, and easier to produce, the Nbs display high specificity, affinity, and stability as compared to conventional antibodies [178]. Single chain Nbs overexpress easily in bacterial and yeast hosts. They have been used for the direct delivery of Nbs against pathogenic enteric bacteria. Because of their single-domain nature, Nbs can be easily expressed as intracellular proteins using viral vectors which can then target proteins that are otherwise inaccessible to conventional antibodies [179]. Their deep tissue penetration and rapid renal clearance makes them suitable for various therapeutic applications, e.g., target bacterial motility [180], prevent biofilm formation [181], inhibit bacterial toxin secretion systems [182], target some key function enzymes [183] or virulence factors [184]. Recently, a nanobody has been developed against anthrax that targets the receptor-binding domain of PA or PA-D4 [185]. The S-layer protein (Sap), a cell surface protein, forms a protective paracrystalline monolayer on the cell wall commonly known as S-layer. A recently developed nanobody that inhibited ‘Sap’ assembly was found to effectively clear B. anthracis infection in mice and protect them from succumbing to anthrax [186]. Development of Nbs that can target anthrax toxins, other virulence factors including the secretion systems, offers an excellent opportunity to develop a better antibody-based strategy to combat fulminant stage anthrax.