Viruses MC Spring 2025 PDF

WE MAKE DOCTORS VIRUSES Arturo Ochoa, M.D.  II. Describe the III. Detect and Associate characteristics and steps of virulence factors involved in the viral infec...

WE MAKE DOCTORS VIRUSES Arturo Ochoa, M.D.  II. Describe the III. Detect and Associate characteristics and steps of virulence factors involved in the viral infection and viral disease pathogenesis replication. outcome. I. Identify and differentiate the main characteristics of the viral agents: I. Capsid II. Genome III. Shape IV. Size Definition A virus is an obligate intracellular parasite. Smallest infectious particles. Ranging in diameter from 18 to 600 nm. Most are Penetration => Uncoating => Replication => Assembly => Viral Release Image: AMBOSS. (2024) General Virology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/Pn0Wtg?q=virus  Viral DNA Replication DNA viruses replicate in the nucleus of the host cells (except Poxviridae) Double-stranded DNA (dsDNA) Without reverse transcriptase: DNA is transcribed to viral mRNA using host RNA polymerase With reverse transcriptase (hepadnavirus only HBV) Transcription requires an RNA-dependent-DNA polymerase, viral DNA via host cell RNA polymerase to viral mRNA. Viral DNA Replication Single-stranded DNA (ssDNA) only Parvoviridae: Host cell DNA polymerase converts ssDNA to dsDNA, negative DNA strand serves as template for mRNA Image: AMBOSS. (2024) General Virology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/Pn0Wtg?q=virus Image: AMBOSS. (2024) General Virology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/Pn0Wtg?q=virus Viral RNA Replication RNA viruses replicate in cytoplasm of host cells (except Retroviriadae and Influenza) Positive-sense single-stranded RNA (+ssRNA) positive sense can be translated directly to form proteins using host ribosome. Without reverse transcriptase viral genome codes for RNA polymerase With reverse transcriptase: retroviruses It transcribes viral ssRNA to dsDNA Viral RNA Replication Negative-sense single-stranded RNA (-ssRNA) a negative strand must be transcribed into positive strand first Viral genome codes for viral polymerase, and then mRNA Includes: Orthomyxovirus, Paramyxovirus, Arenavirus, Filovirus, Bunyavirus, and Rhabdovirus Double-stranded RNA (dsRNA): Reoviridae Image: AMBOSS. (2024) General Virology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/Pn0Wtg?q=virus Pathogenicity Cytolysis: Viral replication results in the destruction of host cell Immunopathological host reactions: Cellular immune response is triggered by CD8+ cells Transfer of genetic material: Bacteriophages may transfer virulence factors  Receptors used by viruses CMV Integrins EBV CD21 HIV CD4, CXCR4, CCR5 Parvovirus B19 P antigen on erythrocytes Rabies virus Nicotinic acetylcholine receptor Rhinovirus ICAM-1 (CD54) SARS-CoV-2 ACE2 Host Defense Mechanisms Innate immune response Physical, biological, and chemical defenses NK cells Complement system Interferon Adaptive immune response Immunoglobulins T Cells Genetic Diversification Recombination (viral) Reassortment (viral) Complementation (viral) Phenotypic mixing (viral) Point Mutations Genetic Diversification Recombination (viral) Exchange of genetic material between two chromosomes of similar or related viral strains that coinfected a host cell, occurs by crossover between two regions of homologous base sequences Reassortment (viral) Occurs in viruses with segmented genomes (Influenza, Rotavirus), is the exchange between segments of two viruses of the same strain that coinfected the same cell. Can result in antigenic shift. Genetic Diversification Complementation (viral) Two mutated viruses from same/different family infect the same cell Mutated viral genome codes for a nonfunctional protein, and nonmutated codes for a functional protein Phenotypic mixing (viral) Occurs with coinfection of a cell with two related viruses, where genome of cell A is partially or completely coated by surface proteins of virus B, giving a viral hybrid. Genetic Diversification Phenotyping masking (transcapsidation) Capsid of one virus envelopes the genome of another Point mutations Causes antigenic drift Image: AMBOSS. (2024) General Virology of the AMBOSS article. Retrieved from https://next.amboss.com/us/article/Pn0Wtg?q=virus Diagnosis Antibody detection Via Hemagglutination inhibition test ELISA o direct immunofluorescence PCR Virus isolation Oncogenesis Herpesviridae Epstein-Barr Virus (HHV-4) Associated with lymphomas: Burkitt lymphoma, Nasopharyngeal carcinoma, Lymphoproliferative disease Hepadnaviridae HBV, oncogenic potential, liver cirrhosis, hepatocellular cancer Papillomaviridae Malignant transformation, (especially infection with high-risk subtypes 16, and 18) References Amboss. (2024). General Virology. Retrieved November 4, 2024, from https://next.amboss.com/us/article/KM0Upg?q=fungi Richard, Goering., Dockrell, Hazel., Zuckerman, Mark., Chiodini, Peter.(2024) Mims' Medical Microbiology and Immunology, Elsevier. 7th Ed. Chapter 3, pages 27-34. Patrick R. Murray, Ken S. Rosenthal (2020). Medical Microbiology (9th edition). Elsevier. Chapter 36-37, pages 362-387.