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COVID-19 Vaccine Development and Applications
Published in Yashwant V. Pathak, Gene Delivery Systems, 2022
Traditional live-attenuated vaccines are produced by growing the virus in suboptimal conditions or through successive passage in cultures or by generating a genetically weakened version of the virus. These weakened viruses replicate in the recipient to induce an immune response but do not cause disease (31). These vaccines are very effective in stimulating both humoral and cellular immune responses and are efficacious in preventing infection. They can be administered intranasally or orally, which could induce a mucosal immunity based on secretory IgA and IgM. Several COVID-19 vaccines have been developed using this platform (see Table 12.2). However, safety concerns related to live attenuated vaccines include occurrence of mutations or recombination with the wild-type virus, which may lead to virulence reversal, so that this type of vaccine is not recommended for immune-compromised patients.
X-Ray and Computed Tomography
Published in Ravishankar Chityala, Sridevi Pudipeddi, Image Processing and Acquisition using Python, 2020
Ravishankar Chityala, Sridevi Pudipeddi
The spectrum (Figure 13.2) does not have a unique energy but has a wide range of energies. When such an energy spectrum is incident on a material, the lower energy gets attenuated faster as it is preferentially absorbed than the higher-energy. Hence a polychromatic beam becomes harder or richer in higher-energy photons as it passes through the material. Since the reconstruction process assumes an “ideal” mono-chromatic beam, the images acquired using a polychromatic beam produce cupping artifacts [BK04]. The cupping artifact is characterized by a radial increase in intensity from the center of the reconstructed image to its periphery. Unlike ring artifacts, this artifact presents difficulty, as it can mimic some pathology and hence can lead to misdiagnosis. The cupping artifacts also shift the intensity values and hence present difficulty in quantification of the reconstructed image data. They can be reduced by hardening the beam prior to reaching the patient, using a filter made of aluminum, copper, etc. Algorithmic approaches [BK04] for reducing these artifacts have also been proposed.
VNPs as Tools for Nanomedicine
Published in Nicole F Steinmetz, Marianne Manchester, Viral Nanoparticles, 2019
Nicole F Steinmetz, Marianne Manchester
An attenuated virus strain is a strain whose pathogenicity has been reduced. Attenuated virus strains are still infectious; however, their virulence is reduced to a level where it is no longer dangerous. Attenuated viruses have historically been generated by serial passage through non-human hosts or cell lines, and through such passage undergo selection for genetic modifications that result in reduced virulence in humans. The overall structural and immunogenic properties of attenuated viruses are usually not sufficiently altered and provide natural interactions with cells and the immune system. Some disadvantages of attenuated virus vaccines are when the viruses cannot be sufficiently attenuated to eliminate adverse affects while maintaining effective immune priming, as well as potential reversion to the virulent genotype (Doan et al., 2005].
An update on COVID-19: SARS-CoV-2 life cycle, immunopathology, and BCG vaccination
Published in Preparative Biochemistry & Biotechnology, 2021
Shankar M. Khade, Shivraj M. Yabaji, Jyoti Srivastava
Mycobacterium bovis BCG is an attenuated strain of virulent mycobacterial strain M. bovis and this attenuated strain has been used a vaccine for tuberculosis. The BCG vaccine is preferred to give in children and administered intradermally. The BCG vaccine was shown to protect TB in children in a better way as compared to adults. The BCG vaccine boosts the immune response, which helps to protect against infection of Mycobacterium tuberculosis (Mtb) and few other unrelated pathogens, including viral infection.[57] The clinical trial data from BCG showed improved innate and adaptive immunity such as inflammatory Th1 cytokines, including IFNg, IL-1 and TNFa, and reduces Th2 cytokines IL-4.[58] The improved immune response play important role in control the upcoming viral or bacterial infections, and this is referred as a trained immunity.[59]
Polymer-based nano-therapies to combat COVID-19 related respiratory injury: progress, prospects, and challenges
Published in Journal of Biomaterials Science, Polymer Edition, 2021
From the history of vaccine development, it is well established that vaccination is one of the most effective strategies to prevent and control the spread of infectious diseases, where naturally developed immunity induces protective long-term immune memory in patients.[132] In general, vaccines introduce specific viral antigens on the cell surface of antigen-presenting cells (APCs), particularly dendritic cells, embodied in the major histocompatibility complex (MHC) I and II.[133] Such an event triggers the adaptive immune system by recognizing these antigens as invaders and induces antibodies production or T cells to eliminate these unwanted invaders. Consequently, memory B cells in the body develop virus-specific antibodies on its cell surface, which triggers a fast immune response to clear the similar viral infection in the future. There are three different generations of vaccine formulations currently used to trigger immune responses against infection, including live attenuated (whole inactivated pathogen) vaccines or first-generation vaccines, recombinant subunit vaccines (second-generation), and RNA/DNA vaccines or third-generation vaccines.[134,135] Since the outbreak of COVID-19, several different vaccine candidates have been developed and reached clinical phases due to a high urgency to halt the pandemic.[136]
PEGylated liposomes: immunological responses
Published in Science and Technology of Advanced Materials, 2019
Marwa Mohamed, Amr S. Abu Lila, Taro Shimizu, Eman Alaaeldin, Amal Hussein, Hatem A. Sarhan, Janos Szebeni, Tatsuhiro Ishida
The use of alternative polymers, such as polyglycerol [108,109], polyvinyl alcohol, polyvinylpyrrolidone (PVP) [110] or polyacrylamide (PAM) [111] instead of PEG, to impart long circulation times to liposome is a promising approach to reduce the induction of the ABC phenomenon. It was reported that surface modification of liposomes with polyglycerol 760 coupled to DSPE significantly attenuated anti-PEG and anti-polyglycerol antibody response. The hydroxylmethyl side group, in the repeating (OCH2CH (CH2OH)) n – subunit of the polyglycerols might sterically prevent the binding of modified liposomes to immunoglobulin on splenic B cells and consequently hinder B cells stimulation. Consequently, polyglycerol coupled to the liposome surface could reduce the clearance of second and subsequent doses when this is a problem [108].