Virus Replication Mechanisms - Study Guide PDF

10.9 Negative-Strand RNA Animal Viruses No known prokaryotic ss(–)RNA viruses ~ Rabies virus rhabdovirus: bullet-shaped, enveloped, helical nucleocapsid … containing several enzymes (Figure 10.20a) must first be transcribed by viral replicase in host cytoplasm into two di...

10.9 Negative-Strand RNA Animal Viruses No known prokaryotic ss(–)RNA viruses ~ Rabies virus rhabdovirus: bullet-shaped, enveloped, helical nucleocapsid … containing several enzymes (Figure 10.20a) must first be transcribed by viral replicase in host cytoplasm into two distinct classes series of mRNAs encoding the structural genes of the virus positive-strand RNA that is a copy of the complete viral genome (template for genomic RNA) complex assembly process release by budding RNA-dependent RNA polymerase  Figure 6. Budding of Recombinant Viruses from the Cell Surface Analyzed by Electron Microscopy https://www.cell.com/fulltext/S0092-8674(00)81072-7  Rabies disease a fatal disease caused by bites from wild animal or pets. infecting brain and 100% death from active disease exposed person should be treated immediately: postexposure prophylaxis (PEP) consists of a dose of human rabies immune globulin (HRIG) and rabies vaccine can be prevented by vaccinating pets and staying away from wildlife https://mappingignorance.org/2016/08/15/rabid-aggression/  Influenza virus enveloped, pleomorphic (non-uniform), budding virus with segmented genome (separate pieces) (Figure 10.21a) surface proteins interact with host cell surface Hemagglutinin (HA) stimulates immune system; anti-hemagglutinin antibodies prevent infection (immunization). Neuraminidase (NA) breaks down sialic acid component of host cytoplasmic membrane, functions in virus assembly. has RNA replicase and RNA endonuclease. Nucleocapsid goes to nucleus for transcription and required for RNA viral RNA replication Enveloped virion forms by budding.  Replication cycle of influenza virus Remember multiple RNA genome in the virns I. Virus replication: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2612335/  Segmented genome results in antigenic shift. Segments of the RNA genome from two genetically distinct ~ strains of virus infecting the same cell are reasserted. ^ generates hybrid virions that express a unique set of surface proteins unrecognized by immune system triggers major outbreaks because immunity to new forms exl iutect hunau sn low absent from population bir 4 fln s tenchenyto ' ' , but close contect make it hazpen 「 can. Then , hybrid uliions can bo made. https://medcraveonline.com/BBIJ/how-influenza-a-causes-epidemics-and-pandemics-among-the-population-novel-targets-for-anti-influenza-molecules.html  Segmented genome and flu pandemics H1N1 is a member of influenza A family (alpha influenza virus), causing Spanish influenza pandemic of 1918–1919 Animal-derived (zoonotic) influenza A viruses, e.g., poultry-adapted influenza A viruses such as H5N1 (60% fatality) and H7N9 (40% fatality), are posing a great risk to human. ' don t name anlmalss WHo : to virus ! conhtuls https://stm.sciencemag.org/content/11/502/eaau5485?rss=1  10.10 Double-Stranded RNA Viruses dsRNA (Class III) virus infect animals, plants, fungi, few bacteria Reoviruses (Figure 10.22a and b) example: rotavirus (causes diarrhea in 6-24-month olds) _ Others cause respiratory infections or infect plants. nonenveloped nucleocapsid with a double shell of icosahedral symmetry Virions contain virus-encoded enzymes necessary to synthesize mRNA and the new RNA genomes. segmented genome binds to receptor, enters and transported into lysosomes, uncoating nucleocapsid, activates RNA replicase in cytoplasm  Reovirus replication Replication occurs exclusively in host cytoplasm within the nucleocapsid. (Figure 10.22c) (+) mRNA synthesized using ss(– )RNA as template Viral proteins aggregate, trapping RNA replicase. Nucleocapids take up genomic (+)RNA fragments and RNA replicase forms dsRNA. coat proteins added in host endoplasmic reticulum and mature reoviral virions released by budding or lysis Synthesis of genomic dsRNA occurs only off (+) strand.