Introduction to virus structure, classification, replication, and hosts
Avindra Nath, Joseph R. Berger in Clinical Neurovirology, 2020
Viral replication is a complex process that is being heavily investigated using both traditional virology as well as systems biology approaches. Modern techniques such as RNA microarrays, next-generation sequencing and mass spectrometry-based proteomics have combined with advances in bioinformatics, led to a better understanding of virus–host interactions. Still, there is great diversity in methods employed by different viruses, with adaptations depending not only on the types of cells they can infect but also on the specific replicative machinery each virus carries and the context of the host immunological response. Furthermore, the current inability to culture some viruses in the laboratory contributes to lack of understanding of their replication cycles.
An Overview of Parasite Diversity
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Availability of genome sequence information for a broad variety of organisms has made it clear that in addition to inheriting genetic information vertically from one’s ancestors, genetic information can move laterally between organisms, without the involvement of sexual reproduction. This process is known as HGT, horizontal (or lateral) gene transfer (see Figure 2.2). Because of HGT, some have argued that the essential concept of the tree of life and divergence from common ancestry has little relevance for bacteria and archaea. It has been further argued that instead of the diversity of all life being derived from common ancestry, that multiple genetic and environmental circumstances acting over a long time have created the diversity of life. Also quite ambiguous with respect to the tree of life are the viruses, which probably infect the cells of all types of organisms and are very adept at moving genetic information from one host cell to another. Standard versions of the tree of life do not include viruses, yet viruses have had a profound impact on all phases of organismal life. In addition to their parasitic role and their involvement in causing disease, viruses regularly provide their host organisms with novel genetic material. A thorough discussion of viruses is beyond the bounds of this book, and the reader is referred to virology textbooks for more discussion of these inherently parasitic, important, and fascinating entities.
Inflection points
J. Michael Ryan in COVID-19, 2020
Significant challenges in the history of virology have been that until the invention of the electron microscope in the 1940s, viruses, unlike bacteria, were not visible. Viruses do not grow in a Petri dish, they only replicate in a living cell. A virus and its genome are small, about one-tenth the size of a bacterium; and due to the structure of viruses, modern antibiotics are ineffective. Science writer David Quammen (2012) explained that despite their small size, viruses are wily and effective, and the genome is “simplified down to the bare necessities for an opportunistic, dependent existence” (267). The tasks a virus must accomplish are getting from one host to another, penetrating a cell within the host, commandeering the cell’s machinery to reproduce multiple copies of itself, and exiting one host, entering another, and surviving.
Could a specific ACE2 activator drug improve the clinical outcome of SARS-CoV-2? A potential pharmacological insight
Published in Expert Review of Clinical Pharmacology, 2020
Lucas A. D. Nicolau, Isabela R. S. G Nolêto, Jand V. R. Medeiros
As an acute viral disease, Covid-19 has some phases already observed and suggestively proposed by epidemiologists. Chakraborty and colleagues (2020) published a very organized compilation which brings these phases of coronavirus outbreak with SARS-CoV-2 in (i) incubation period (up to 5 days), (ii) symptoms appear (6–7 days); (iii) painful breathing (8 day); (iv) respiratory distress syndrome – acute phase (9 days), and (v) severe case – patient admitted to ICU (more than 10 days). In early stages, before acute phase, the appropriate recommendation in the scope of medical virology is the use of antivirals to mitigate viral replication. In Covid-19, there is not a specific antiviral although a plenty of clinical studies are ongoing with off-label medications such as chloroquine, hydroxychloroquine, lopinavir, and remdesivir [18,19]. However, in late phases, patients with Covid-19 have been minor benefits with antiviral therapies. Recently, preliminary study results suggested dexamethasone, a commonly used steroid, to reduce risk of death in sickest Covid-19 patients [20]. Clinical pharmacology is yet seeking effective options for treating Covid-19 due to the high nonresponsive patients to suggested drugs up to this date.
The management of anti-infective agents in intensive care units: the potential role of a ‘fast’ pharmacology
Published in Expert Review of Clinical Pharmacology, 2020
Dario Cattaneo, Alberto Corona, Francesco Giuseppe De Rosa, Cristina Gervasoni, Danijela Kocic, Deborah Je Marriott
A disadvantage of traditional bacteriological culture techniques has always been the time taken between the inoculation of the agar plates and the growth and identification of the pathogenic organisms. In other areas of microbiology such as virology, the problem was even greater as routine laboratories were unable to culture viruses and many viruses were difficult to grow even in tissue culture systems. Therefore, rapid diagnostics were not possible and microbiology remained relatively unchanged for many decades. Recently there has been a remarkable effort to develop novel technologies for faster microbiological diagnosis and antimicrobial susceptibility testing, enabling information on pathogen identification and, in some cases, antimicrobial resistance profiles in a shorter timeframe when compared with the conventional diagnostic workflow which involves subculture followed by identification and antimicrobial susceptibility testing carried out from isolated bacterial or fungal colonies. A result could be available within hours, as opposed to the 72 hours required by conventional methods.
Molecular engineering tools for the development of vaccines against infectious diseases: current status and future directions
Published in Expert Review of Vaccines, 2023
Wenhui Xue, Tingting Li, Ying Gu, Shaowei Li, Ningshao Xia
The utilization of viral vectors for gene therapy dates back to the early days of virology [143]. However, due to the continuous evolution of virology, viral vectors have now become important engineering tools that facilitate the creation of a diverse array of innovative vector vaccines (Figure 3b) [144]. By introducing target antigen sequences at appropriate positions in the viral vector, the vector can deliver the antigen to host cells, thereby triggering a comprehensive immune response [145]. Among the various vector tools available, replication-defective viruses such as adenovirus, lentivirus, and poxvirus are particularly attractive for vaccine development due to their safety, wide range of host cells, low vector immunogenicity, and ability to express exogenous genes for prolonged periods in vivo [146].
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