Fluent Essays

Reading Assignments - Review week 5 course content topics “General Properties of Viruses” and “Viral Replication (Life Cycle)” and week 5 reading assignments in course module 4 - Review week 5 reading assignments in Course Module 4 Commentary topics: “Viral Characteristics”, “Viral Structure”, “Viral Nucleic Acid” and “Animal Virus Life Cycle” -Review Parker, et al (2016) 6.1 Viruses, in Microbiology. OpenStax (see citation in week 5 assignments topic) - Read Course Module 5 on immunity NOTE I only need you to cover section V through VI Wk. 5 Key Concept Virus Replication.html General Steps in the Viral Replication Cycle Key Concept: The general steps in viral replication (life cycle) are similar for enveloped and non-enveloped (naked) animal viruses.   Although viruses vary in viral replication and transmission strategies, the following general stages of the viral replication cycle (also referred to as the viral life cycle) are similar for all known animal viruses. Attachment (Adsorption) occurs when a virus binds to specific receptors on the host cell envelope. Some viruses have a specific tropism in that infect certain types of cells, and some viruses have a broad host range (that is they can infect many different host species, for example rabies) and others have a narrow host range (they only infect one or few species, for example HIV). Penetration (Entry) is when the attached virion (virus particle) is taken into the host cell cytoplasm by fusion of the viral envelope with the host cell membrane (enveloped viruses) or endocytosis or in some cases by direct penetration of the virion across the plasma membrane (enveloped viruses) Uncoating is the stage in which the virion the separation of the virion nucleic acid from the viral capsid. The viral capsid is degraded and the nucleic acid is available for the biosynthesis stage. Biosynthesis is the stage in which the viral genome is replicated and viral enzymes and other proteins are produced.  Assembly occurs when a certain level of newly synthesized viral proteins and nucleic acid genomes has been produced and is the process in which immature viral particles are formed by packaging viral nucleic acids and proteins into a new synthesized capsid. Maturation is the stage in which a virus becomes infectious. This may require modifications to viral or host cell proteins or other mechanisms. Release of the infectious virion may occur by budding from the host cell membrane or lysis of the cell allowing the release of the virions. Note: Assembly, maturation, and release are not always recognized as distinct stages. The general stages of an animal virus life cycle are illustrated in Figures 4.6 to 4.9 of Course Module 4 Commentary (UMGC, n.d.) and Figure 6.10 in Parker et al (2016).   Viral Genome Replication and Viral Protein Synthesis As previously noted viruses differ in the structure and nucleic acid compositions of their genome. The genome of viruses can be circular or linear, segmented or a single molecule of nucleic acid. The genome can be either single stranded (ss) or double stranded (ds) DNA or RNA, and single stranded nucleic acid genomes can be either a positive strand or a negative strand based on how it becomes transcribed to mRNA. Only a positive (+) viral mRNA strand can bind to ribosomes of the host cell and be translated into viral proteins. There are seven different genome groups by which viruses can store their genetic information (see Table 4.1 Viral Genome Groups in Course Module 4). Table 4.1 from Course Module 4 Viral Genome Groups Group DNA or RNA Nucleic Acid Type and Orientation Examples of Viruses Examples of Disease(s) Caused I DNA double-stranded adenoviruses respiratory illnesses II DNA (+) single-stranded parvoviruses fifth disease (childhood rash) III RNA double-stranded reoviruses gastroenteritis IV RNA (+) single-stranded picornaviruses polio, foot and mouth disease, common cold, hepatitis A (HAV) V RNA (–) single-stranded orthomyxoviruses influenza VI RNA single-stranded retroviral HIV AIDS   As previously noted, for replication a virus uses the host cell molecules and machinery to make viral proteins. DNA viruses need to make mRNA that is then translated to produce viral proteins. Some DNA viruses enter the host cell nucleus and use the host cell machinery to make mRNA and replicate the viral DNA (e.g., adenoviruses, human herpesviruses, and Human parvovirus B-19). Other DNA viruses do not enter the host cell nucleus, but replicate in the cytoplasm (e.g., vaccinia virus) (Hunt, 2016, Chapter 3). These viruses enter the host cell with their own viral RNA polymerase, which is used for transcription, and other enzymes Some RNA viruses have a DNA phase (i.e., they copy their RNA into DNA) – Group VI and Group VII; these viruses include HIV and other retroviruses. Other RNA viruses do not have a DNA phase – Groups III, IV, and V (Hunt, 2016, Chapter 4).  Cited Sources Hunt, M. (2016, May  31) Virology Chapter 3 “DNA Virus Replication Strategies” with additions by Mcllroy, D. in Microbiology and Immunology Online, University of South Carolina Medical School. Retrieved from http://www.microbiologybook.org/book/virol-sta.htm.  Hunt, M. (2016, May 31) Virology Chapter 4 “RNA Virus Replication Strategies” with additions by Mcllroy, D. in Microbiology and Immunology Online, University of South Carolina Medical School. Retrieved from http://www.microbiologybook.org/book/virol-sta.htm Parker, N., Schneegurt, M., Thi Tu, A.-H., Lister, P., & Forster, B. M. (2016) 6.2 The Viral Life Cycle in Microbiology. Houston: OpenStax. Online version retrieved from https://openstax.org/details/books/microbiology UMGC (n.d.) Animal Virus Life Cycle in BIOL 302 Course Module 4 Viruses: Commentary. Document posted in University of Maryland Global Campus (UMGC) BIOL 302 6981 (2205) online classroom archived at: http//:campus.umuc.edu Preliminary title Thesis Statement: I. Overview of Virus A. Structural characteristics of a virus B. Explain how a virus causes disease and illness II. Overview of specific virus SArS-CoV-2 A. Describe how virus infects cell B. Explain why transmission rate if so high III. Overview of vaccines A. Explain in detail how vaccines provide protection B. Describe the steps in developing a vaccine IV. Overview of ChAdOx1 A. Summary of monkey study B. Summary of pilot test in humans V. Overview of NCT04324606 clinical trial VI. Summary of terms A. Phase 2 clinical trials B. Phase 3 clinical trials C. Immunizations Monkey study: · Single dose of ChAdOx1 nCoV-19 protected six rhesus macaques from pneumonia caused by the virus. · Not peer reviewed yet. · Phase 1 trial of the candidate vaccine began on April 23 in healthy volunteers · Developed at the University of Oxford Jenner Institute · Uses a replication -deficient chimpanzee adenovirus to deliver a SARS-COV-2 protein to induce a protective immune response · Study showed vaccine rapidly induced immune responses against SARS-COV-2 in mice and rhesus macaques. · Then conducted vaccine effectiveness by giving six animals the vaccine 28 days before infecting the with SARS-COV-2. They were compared to three control animas who did not receive the vaccine. Animals showed no signs of virus replication in the lungs, lower levels of respiratory disease and no ling damage compared to the control animals. · Oxford University has entered into a partnership with UK-based global biopharmaceutical company AstraZeneca for the further development, large-scale manufacture and potential distribution of the vaccine. Pilot test in humans: · Phase 1 trail in healthy adult volunteers began in April. More than 1,000 immunizations have been completed and follow-up is currently ongoing. · Phase 2 will include older adults and children. Total of 10, 260 adults and children – randomized to receive one or two doses of either ChAdOx1 nCoV-19 vaccine or license vaccine (MenACWY). Study participants will not know whether they have received the ChAdOx1 nCoV-19 vaccine until the end of the trial. · Phase 3 will study how the vaccine works in large number of people over 18 - randomized to receive one or two doses of either ChAdOx1 nCoV-19 vaccine or license vaccine (MenACWY). Study participants will not know whether they have received the ChAdOx1 nCoV-19 vaccine until the end of the trial. · Genetic material has been added to the ChAdOx1 construct, that is used to make proteins from the COVID-19 virus (SARS-CoV-2) called Spike glycoprotein (S). This protein is usually found on the surface of SARS-CoV-2 and plays an essential role in the infection pathway of the SARS-CoV-2 virus. The SARS-CoV-2 coronavirus uses its spike protein to bind to ACE2 receptors on human cells to gain entry to the cells and cause an infection · By vaccinating with ChAdOx1 nCoV-19, we are hoping to make the body recognise and develop an immune response to the Spike protein that will help stop the SARS-CoV-2 virus from entering human cells and therefore prevent infection.  NCT04324606  · 1090 participants · Primary measures: · Secondary measures : Wk. 5 Key Concept General Properties of Viruses.html General Properties of Viruses Key concepts: Viruses are not cells and require host cell components for replication. The basic structure of a virion (a virus, also described as a complete virus particle) includes a nucleic acid core of either DNA or RNA and a protein coat called a capsid. What are viruses? Viruses and several diseases they cause were introduced in Course Module 1 Introduction to Microbiology and others are described in Course Module 4 Viruses. Recall that viruses are not cells (they are acellular). Unlike bacteria, they don't have cytoplasm or ribosomes, and they don't grow (increase in size), metabolize nutrients, or produce waste products. The viral genome is either DNA or RNA, and there is a lot of diversity in the physical characteristic of the genome (Parker et al., 2016 & UMGC, n.d.). Similar to bacteria and other cellular microbes, viruses are able to mutate and reproduce, but viruses require the structures and molecules of a host cell for replication. Most viruses have a diameter in the 20 nm to 300 nm range. Some viruses are larger than mycoplasma and other small bacteria, and there are the Giant Mimiviruses, which have capsid (the outer protein coat of the virion) diameters of 400 – 500 nm, which when stained are visible with a light microscope (Wessner, 2010). However, as a group, viruses are one of the smallest infectious agents known. There are viruses that infect vertebrates, invertebrates, plants, fungi, and even bacteria. Several hundred different viruses are known to infect humans. This week you will learn more about the structure and classification of viruses, and their productive life cycles (also described as viral replication cycle). General Structure of a Virion A virion is a single complete virus particle composed of nucleic acid (either DNA or RNA), a capsid (a protein shell that encloses the DNA or RNA genome), and attachment proteins (used to bind the virus to the surface of host cell) and other proteins. The capsid and genome complex is called a nucleocapsid. Some viral particles are surrounded by a lipid envelope derived from the host cell and some viruses have enzymes or other protein. The structure of a typical virion is illustrated below. Components of a Typical Virion (Figure 4.2 from UMGC, n.d.) In the following YouTube video Paul Anderson (2012) describes and illustrates structural components and reproductive features common for all viruses and some differences in structural components (for example, presence or absence of envelope and type of genome) and life cycle that contribute to the wide diversity in the structure and life cycle of viruses.