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51 Cards in this Set
- Front
- Back
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What are the components of the virus structure?
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1. genome
2. capsid 3. nucleocapsid 4. envelope 5. virion |
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What are the four types of viral genomes?
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ssRNA (+/-)
dsRNA ssDNA dsDNA |
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What is the capsid and what viruses have them?
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protective protein shell that surrounds the genome. all viruses have these
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What is the nucleocapsid?
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this is the name that encompasses the capsid and the genome as they exist together. nothing more.
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What is the envelope?
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lipid membrane bilayer that surrounds the nucleocapsid of SOME (not all) viruses. All helical capsids have envelopes. lipid membranes are derived from modified portion of infected cellular membrane, and lipid solvents can disrupt that membrane and kill the virus.
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What is the virion?
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this is the name for the complete infectious particle.
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What are the two types of DNA genomes found in viruses?
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1. linear DNA
2. circular DNA |
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What are examples of ss and ds linear DNA genomes?
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linear dsDNA - herpesvirus, poxvirus, adenovirus
linear ssDNA - parvovirus (B19) |
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What are examples of ss and ds circular DNA genomes?
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circular dsDNA - papovavirus (papillomavirus)
circular part ssDNA and part dsDNA - hepadenavirus (hepatitis B) |
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What is significant about the number of DNA molecules in a DNA based viral genome?
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there is always only one molecule of DNA that is contained in a DNA based viral genome
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What is significant about RNA viral genomes?
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1. they have a high mutation rate because there is no proof reading
2. there is only linear RNA, no circular 3. RNA genomes exist in one or several RNA fragments |
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What are examples of RNA based genomes?
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dsRNA - reovirus causing gastroenteritis
ssRNA - all others |
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What is the infectious agent (virion) for viruses that do not have an envelope?
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capsid. makes sense because the capsid is the protein layer that exists below the lipid bi-layer of an envelope. if there is no envelope, then the capsid is exposed.
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What is a protomer?
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single unit of protein molecules that repeats to make up the capsid. they are held together by non-covalent hydrogen bonds. the repeating architecture always presents symmetry
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What three types of symmetry occur as a result of the highly ordered protomer arrangement?
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1. helical
2. icosahedral (cubic) 3. complex (unknown) |
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Describe the structure of a virus that exhibits helical symmetry.
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Protomer-protomer bonding forms a single continuous protein of helical shape like a curly phone cord. The diameter is determined by the protein-protein interactions of the protomer. The length is determined by the size of the ssRNA molecule. The complete package is folded up and packaged.
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What is the difference between positive-stranded and negative-stranded ssRNA?
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+: RNA genomes can act as mRNA, inherently
-: RNA genomes that must first be transcribed into mRNA |
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Describe the structure of a virus that exhibits icosahedral symmetry.
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This is a 20 faced, 12 vertices 3d shape that has the advantage of having the smallest volume but biggest relative space for the most genetic material.
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Describe the structure of a virus that exhibits complex symmetry.
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I dare you to describe it. You'd win. It hasn't been figured out, but it looks like a ball of yarn. We know it's symmetrical because it will crystallize.
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What is a peplomer?
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transmembrane viral glycoproteins that protrude in a spike-like fashion from the envelope. they assist in several key steps in viral replication and attachment.
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What is an example of a virus that inoculates in the skin?
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papillomavirus innoculate in the epidermis and form warts. they will not spread since there is no circulation in the epidermis.
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What is an example of a virus that inoculates through the skin?
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arthropod bites go through the dermis and can disseminate causing yellow fever, dengue fever, encephalites
needle sticks can cause hepadnavirus - Hep B animal bites - rhabdovirus - rabies |
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What is an example of a virus that inoculates through the respiratory tract?
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herpesvirus, adenovirus, influenza, mumps, rhinovirus
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How does the body inherently act against viruses in the respiratory tract?
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goblet cells secrete mucus, ciliated epithelial cells move foreign bodies upward, IgA, alveolar macrophage, lymph system, lower temperature in upper respiratory tract
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What is an example of a virus that inoculates through the GI tract?
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Reoviridae - Rotavirus
Picomaviridae - Hep A, Polio Caliciviridae - Hep C |
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How does the body inherently act against viruses in the GI tract?
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low pH, proteolytic enzymes of small intestine, bile salts all will lyse the lipid envelope, so viruses that infect via GI are resistant to these defenses and will be non-enveloped
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What is the transmission circulation of GI tract infecting viruses?
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fecal-oral
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What is an example of a virus that inoculates through the GU tract?
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Herpesvirus - HSV-1, HSV-2
Retrovirus - HIV1, HIV2 Pepillomavirus - HPV6 |
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How does the body inherently act against viruses in the GU tract?
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cervical mucus
pH of vaginal secretions chemical composition of urine |
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What is an example of a virus that inoculates through the conjuntiva?
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adenoviruses - swimmer's eye
enterovirus |
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What is a primary viral infection?
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first encounter of a virus in general or encounter prior to systemic effects. usually no clinical presentation
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What are two examples of viruses that have no or trivial clinical presentation during primary infection?
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1. Polio - GI tract infection with fever, GI distress, but NO CNS symptoms
2. Measles - fever, cough but NO systemic rash |
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What is prodrome proper?
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any symptoms experienced before the main disease presentation
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What are examples of viruses that only produce clinical symptoms of a primary infection?
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1. Reovirus - GI effects only causing diarrhea w/o spread
2. Picornavirus - only infect respiratory tract causing common cold |
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What is local spread proper?
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virus only replicates at site of inoculation, there is no dissemination
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What is an example of a virus that only does local spread?
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Papillomavirus - causes warts that don't disseminate
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How does a virus spread from initial site of replication into subepithelium and lymphatic systems?
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virus penetrates basement membrane and macrophage engulfs and moves virus systemically
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What is viremia?
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systemic (in blood) spread of virus
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What is the difference between primary viremia and secondary viremia?
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Primary: virus is unapparent with low numbers
Secondary: large numbers of virus that occur after Primary viremia has occurred and a second round of replication occurs causing a burst of numbers |
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What is direct travel mechanism of viral spread?
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viruses that move via peripheral nerves to CNS
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What are three examples of direct travel viral spread?
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HSV, VZV, Rabies
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What are three types of maternal-fetal transfer of viruses?
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1. spread to fetus
2. perinatal 3. postnatal |
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What is tropism?
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tropism is the mandatory type of tissue that a virus can only infect because of intracellular factors, cell surface receptors, route of viral entry, etc
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What interferon produces a general, non-specific anti-viral state?
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gamma
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What two types of Ab interactions can viruses use to further infection?
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1. Antibody enhancement - Ab that is produced after initial infection is used upon second infection to assist virus into macrophage
2. Autoantibodies - autoimmune antibodies |
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What is the subclinical outcome of viral infection?
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the host is unaware of infection because immune response does its job
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What is the acute outcome of a viral infection?
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many different presentations, but will present clinically and cause necrosis, apoptosis and collapse of cellular structure in general
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What is the persistent infection outcome of a viral infection?
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a host is always infected and continually sheds a small amount of virus. this condition may or may not display clinically.
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What is the chronic infection outcome of a viral infection?
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this is a subtype of persistent infection in which there is a chronic production of virus over a long period of time
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What is the slow viral disease outcome of a viral infection?
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very long incubation period in which there are years between initial infection and release of virus -> disease
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What is the transformation outcome of viral infection?
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this is the phenomenon that viruses do in which cells are forced into the cell cycle which can lead to perpetual cell cycle production -> leads to cancer
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