1. Nature and Structure of Viruses
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| Tobacco mosaic virus | first virus to be recognized as filterable
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| Foot and mouth disease virus | first filterable animal virus
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| Yellow fever virus | first human virus
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| A. Negri | discovered inclusion bodies of rabies virus
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| P. Rous | first demonstration of a solid tumor virus
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| Rous sarcoma virus | solid tumor virus
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| Bacteriophages | discovered by Twort and d'Herelle
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| A. Woodruff and E. Goodpasture | reported on use of embryonated hen's egg as a host for viruses
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| J. Enders et al | reported that nonneural tissue supports poliovirus replication in culture
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| Knoll and Ruska | invented the electron microscope
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| Dmitri Iwanoski | Tobacco mosaic virus
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| F. Loeffler and P/ Frosch | Foot-and-mouth disease
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| Walter Reed et al. | yellow fever virus
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| Protozoa, fungi, and bacteria - unicellular or multicellular | unicellular
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| Protozoa, fungi, and bacteria possess the equipment for the production of ___ | metabolic energy and macromolecules
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| Example of macromolecules | nucleic acids, proteins, polysaccharides, and lipids
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| Viruses are dependen on ____ for functions | their cellular hosts
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| Virus particle is _____ outside a susceptible cell | metabolically inert
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| > 300 nm diameter (Bacterial, RC, Viruses) | Bacteria
Rickettsia Chlamydophila
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| Obligate intracellular parasite (Bacterial, RC, Viruses) | RC
Viruses
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| Plasma membrane (Bacterial, RC, Viruses) | Bacteria
RC
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| Binary fission (Bacterial, RC, Viruses) | Bacteria
RC
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| Possess both DNA and RNA (Bacterial, RC, Viruses) | Bacteria
RC
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| Functional ribosomes (Bacterial, RC, Viruses) | Bacteria
RC
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| ATP-generating metabolism (Bacterial, RC, Viruses) | Bacteria
Maybe RC
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| Sensitive to antibiotics | Bacteria
RC
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| Sensitive to interferon | Viruses
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| Viruses are _____ particles | submicroscopic particles
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| Viruses' genomes are elements of ____ | nucleic acid that replicate inside living cells
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| Viruses replicate by using ____ | the cellular synthetic machinery for the production of progeny virions
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| Virus | fluid poison or filterable viruses
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| Host range | range of animal species and tissue cells that the virus can infect
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| Host range for a given virus | broad or extremely limited
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| Structural unit | protomer
protein subunit which may be assembled into capsomeres, may consist of one subunit or different protein subunits
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| Capsomeres | morphologicqal subunits from which the virus capsid is built
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| Capsid | protein shell or coat that encloses the nucleic acid genome
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| Envelope | a lipid-containing membrane that surrounds some viruses
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| Nucleocapsid | capsid together with the enclosed nucleic acid
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| Virion | complete infective virus particle
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| Viral attachment proteins (VAPs) | Capsid and envelope proteins that mediate the attachment of viruses to specific host cell receptors
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| Incomplete virion | virion without nucleic acid (empty capsid)
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| Defective virus | virus that cannot replicate b/c it lacks a full complement of viral genes
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| Replication only occurs | in mixed infections with a helper virus
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| Pseudotype | when related viruses infect the same cell, the genome of one virus may be enclosed in the heterologous capsid of the second virus
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| Pseudovirion | during viral replicaton, the capsid sometimes encloses host nucleic acid rather than viral nucleic acid
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| Pseudovirion - replicate? | look like ordinary viruses particles when observed by electron microscope, but do not replicate
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| Episome | autonomous extra-chromosomal genetic element
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| Provirus | viral DNA that is integrated into a host cell chromosome in a latent state and must be activated before it is transcribed
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| Provirus is transmissible from ____ | a parent cell to its daughter cell
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| Virus consists of ___, surrounded by a protein coat, ____ | nucleic acid
capsid
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| Capsid - enveloped or nonenveloped? | could be either
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| Capsid are made up of ___ held together by ____ bonds | capsomeres
noncovalent bonds
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| Most viruses have ___ capsid except for the ____ | one
reoviruses
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| Reoviruses have ____ capsids | outer, middle, and inner
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| Cubic Symmetry | icosahedron pattern
12 corners/vertices/20 equilateral triangular faces, and 30 edges
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| Most efficient arrangement for subunits in a closed shell | cubic symmetry
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| Capsomeres are ___ in herpesviruses and reoviruses | hollow
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| Capsomeres are hollow in ____ | herpesviruses and reoviruses
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| Capsomeres located at the certices of icosahedral virions | Penton
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| Penton | Capsomeres located at the certices of icosahedral virions
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| Capsomes and nucleic acid molecules | self-assemble as a helix
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| Why is it not possible for "empty" helical particles to form | b/c of the interaction b/t capsid protein and nucleic acid
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| Incomplete virions | helical nucleocapsids
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| In all animal viruses, helical nucleocapsides are wound into ___ and ____ | into a coil
and enclosed within a lipoprotein envelope
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| Complex viruses | some virus particles do not exhibit simple cubic or helical symmetry but are more complicated
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| Poxviruses | brick-shaped with ridges on the external surface and a core and lateral bodies inside
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| Capsid function | structural symmetry
encases and protects
facilitates attachment
contain enzymes
determines antigenic characters
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| Capsid encases and protects the viral nucleic acid from | nucleases in biologic fluids
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| Capsid facilitates the attachment of virus to | susceptible cells
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| Some capsids contain enzymes | which play roles in the infection process
ex/ many viruses contain their own nucleic acid polymerases which transcribe the viral nucleic acid into mRNA
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| Capsids determine the antigenic characteristics of the virus | the host's protective immune response is directed against antigenic determinants of proteins or glycoproteins exposed on the surface of the virus particle
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| Enveloped virons acquired their envelopes when | the nucelocapsid buds from cellular membranes (cytoplasmic membrane, nuclear membrane, or Golgi complex)
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| Budding occurs only at sites where _____ have been inserted into the host cell membrane | virus-specific proteins
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| Envelope consists of | Virus-specified proteins
Lipid bilayer
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| Virus-specified proteins associated with | receptor binding
membrane fusion
matrix protein
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| Receptor binding associated with | glycoprotein peplomeres, observed as spikes in electron micrographs
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| Membrane fusion associated with | fusion proteins
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| Polysaccharides are dervied from | the host cell
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| Fusion proteins are associated with | peplomeres and are involved in viral entry into and release from cells
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| Matrix protein found | a layer inside of some evelopes
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| Matrix protein serves as _____ for ____at plasma membrane | recognition site
nucleocapsid
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| Matrix protein provides ____ to the envelope | added rigidity
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| Lipid bilayer derived from | host cell membrane
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| The integrity of the envelope is maintained ______, so it's readily disrupted by ____ | -maintained only in aqueous or moist environments
-disrupted by drying, acidic conditions, etc
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| Solvents or detergents are used to ______ | disrupt the integrity of the envelope
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| Examples of solvents | ether
chloroform
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| Examples of detergents | sodium deoxycholate
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| Disruptions of the envelope result in ______ except in some poxviruses | loss of infectivity
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| Capsids and envelopes both have ______ | viral attachment protein
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| Viral proteins | make up 50-70% of the virion
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| Examples of viral proteins | structural proteins
regulatory proteins
enzymes
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| Several viruses contain enzymes at are encoded in the _____ | viral genomes
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| Most important enzyme that is encoded in the viral genome | Polymerases
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| Polymerases | copies part of all of the genome of the virus, sometimes immediately upon entry into the host cell
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| Types of enzymes that are encoded in the viral genome | -enzymes transcribing the viral genome into mRNAs
-enzymes involved in copying virion RNA and DNA
-enzymes that copy the nucleic acid genome
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| Enzymes transcribing the viral genome into mRNAs | DNA-dependent RNA polymerase
RNA-dependent RNA polymerase
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| DNA-dependent RNA polymerase ___ as template | DNA
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| RNA-dependent RNA polymerase ___ as template | RNA
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| DNA-dependent RNA polymerase: carried by DNA viruses such as ________ which replicate in the cytoplasm | asfivirus
poxviruses
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| RNA-dependent RNA polymerase: carried by viruses with _____ | (-) sense RNA genome
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| RNA-dependent RNA polymerase: Host cells lack/have this enzyme | lack this enzyme
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| Enzymes involved in copying virion RNA into DNA | RNA dependent DNA polymerase
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| RNA dependent DNA polymerase | reverse transcriptase
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| RNA dependent DNA polymerase: Carried by ______ | hepadnaviruses
retroviruses
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| Enzymes that copy the nucleic acid genome | DNA-dependent DNA polymerase
RNA-dependent RNA polymerase
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| DNA-dependent DNA polymerase | copies the DNA genome
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| RNA-dependent RNA polymerase | replicase
copies the RNA genomes
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| Viral nucleic acids | encode the genetic info necessary for replication of the virus
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| All viral genomes are haploid/diploid | haploid (they contain only one copy of each gene)
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| Genome may be ___________ | Monopartite or multipartite
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| Monopartite | all viral genes contained in a single chromosome
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| Multipartite | segmented
ex/ viral genes distributed among several chromosomes that constitute the viral genome
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| DNA genome | genome of all DNA viruses of vertebrates is monopartite
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| DNA genome are double/single stranded | can be either double or single stranded
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| RNA genome | single stranded or double stranded
monopartite or multipartite
positive sense RNA genome
negative sense RNA gemone
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| Positive-sense RNA genome | can function as mRNA in the infected cell
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| can function as mRNA in the infected cell | Naked RNA extracted from a (+) sense RNA virus is infectious when injected into host cell
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| Since mRNA can be directly translated into polypeptides, it is designated ____ | plus (+) mRNA
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| Viral nucleic acids | DNA genome
RNA genome
Viral lipids
Viral glycoproteins
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| Negative -sense RNA | cannot function as mRNA, so virion carries own transcriptase enzymes
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| Injected naked RNA is infectious/not infectious | not infectious
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| Viral lipids | found only in the envelope
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| Viral lipids are a typical bilayer with ____ and in some cases, other viral proteins, embedded in it | virus-coded glycoprotein peplomeres
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| Viruses face harsh environmental conditions in the body and on the outside, including | pH changes
bile salts
proteases
temperature
osmotic changes
sunlight
dessication
humidity
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| To maintain transmissibilty, and infection in a susceptible population, a virus must ___________ | overcome some of these conditions
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| Naked viruses survive well/ not well in the body and on the outside | survive well
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| _____ are more susceptible to environmental factors, such as gastric acidity, drying, and bile salts | Enveloped viruses
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| Viral surface proteins are denatured within a few mins at temperatures of _____, whicch make the viron incapable of normal cellular attachment, penetration, and/or uncoating | 55 to 60C
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| Acidic conditions can lead to _____ of the viral capsid | reversible or irreversible
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