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51 Cards in this Set
- Front
- Back
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When were viruses first detected and what were they thought to be?
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1890's, proposed as "poisons"
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When were viruses first seen and how?
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First seen in the 1930's via an electron microscope.
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What is the definition of a virus?
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Subcellular agent, consisting of a core of nucleic acid, surrounded by a protein coat that must use the metabolic machinery of a living host to replicate and produce more viral particles.
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Viruses are obligate intracellular parasites, true or false?
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True
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What size range are viruses? Are they larger or smaller than bacteria?
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20-300nm (20-3000*10^-9) in diameter. Smaller
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What is the only type of microscope that is powerful enough to see a virus?
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electron microscope
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What is the central core made of?
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DNA or RNA, can be single or double stranded
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What is the name for the protective coat around a virus? What's it made of? What are the subuits also known as?
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Capsid; made of protein subunits called capsomeres.
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What is the core + capsid called?
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nucleocapsid
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Do all viruses have enelopes?
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No
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What does the outter covering (envelope) consist of?
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proteins, lipids, carbohydrates, and in some viruses, "spikes
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What is a virion?
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The complete, infective viral structure
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What are 6 ways of categorizing viruses?
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1. Nucleai Acid
2. Enveloped vs. Non-enveloped 3. Capsid Architecture 4. Symptoms 5. Mechanism of transmission 6 Organ system affected |
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What are three types of capsid architecture and an example for each?
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Helical: rabies, ebola
Polyhedral: polio, adenovirus Complex: bacteriophage |
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List 6 routes of infection
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Gastrointestinal Tract, Respiratory Tract, Injection (insects, vaccines), Skin Breaks, Urogenital Tract, Conjunctiva
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Are viruses specific (ie, will only attack certein cells depending on what virus they are)?
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Yes, they are specific
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What is tissue tropism?
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Viral specificity towards its host cell type
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Give an example of tissue tropism?
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Influenza virus affects respiratory cells.
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List the steps in viral infection.
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1. Adsorption/attachment
2. Penetration and uncoating 3. Synthesis of viral proteins 4. Maturation and assembly 5. Release |
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Describe adsorption/attachment.
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It's the interaction b/w receptors on the surface of the host cell and the virus. It's the basis for tissue tropism. Interaction results in binding of the virus to the host cell surface.
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List the different kinds of penetration and uncoating
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Endocytosis, Fusion, Direct penetration
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Describe Endocytosis
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receptor/virus complexes are invaginated on cell surface, combine w/lysozymes that digest the viral layers & release the nucleocapsid into the cell
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Describe Fusion
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fusion of viral envelope w/cell membrane, releasing nucleocapsid into cell
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Describe direct penetration
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Direct passage of small, non-enveloped virus through cell membrane.
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What happens once the virus is inside the cell?
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It's uncoated, the capsid and envelope are removed and the viral nucleic acid is released.
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Describe the synthesis of viral proteins.
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The viral genome is transcribed by the host cell machinery, producing viral proteins
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What are two types of release (of the virus from the host cell) and describe them.
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1. Budding: enveloped viruses are released through exocytosis...the host cell survives.
2. Cell lysis: rupture of cell and release of formed virions. Cell host dies. |
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List 4 viral effects on the host cells.
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1. Cell lysis
2. Alteration in cell function 3. Persistent infection 4. Cell transformation |
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Give an example of a virus and its effect on the host cell
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Poliovirus lyses motor neurons, leading to loss of function of corresponding muscles.
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What causes the alteration in cell function?
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The viral genome incorporation into the host cell's genome causes an alteration in host cell protein synthesis.
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Give an example of how influenza virus alters it host cell
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it alters respiratory epithelium and thereby decreasesciliary activity.
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What are the three types of persistent infection?
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Latent, chronic, and slow virus infection
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Describe the qualities of a latent infection
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Virus is in equilibrium w/host. Infectious virus is not produced but its genome is present in its host cell
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Describe the qualities of a chronice infection
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Virus does cause cell death, but symptoms are subclinical
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Describe the qualities of a slow virus infection
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Long incubation period (yrs). Virus continues to multiply slowly and causes protracted tissue damage.
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Give 1 or more examples of latent infection, chronic infection, and slow virus infection
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latent= herpes, cold sores
chronic= hepatites B in human slow= HIV & scrapie |
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Which persistant infection type may be affected by stress and immunosuppression and what is the result of the stress or immunosuppression?
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Latent infection; acute, intermittent flare-ups of clinical disease and virus is released and detectable during these episodes
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What happens in cell transformation by a virus?
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Viral transformation of normal cells into cancerous cells (oncogenic virus). Loss of the property of contact inhibition
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Give some examples of cell transformation
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Human carriers of hepatitis B vius are 100x more likely to develop liver cancer. Also, FeLV in cats.
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List 3 ways to diagnose a viral disease
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1. Complete history and physical exam
2. Procedures that demonstrate the presence of infectious virus 3. Serology |
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What must be done in getting a Complete History and Physical Exam?
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Must secure appropriate tissue samples
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What types of ways/machines are used to demonstrate the presence of infectious viruses?
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1. Electron microscopy
2. Virus isolation/culture 3. PCR (polymerase chain reaction-identifies viral DNA) |
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Describe virus isolation/culturing
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1. Introduction of suspected virus sample into appropriate living cell culture
2. If present, the virus will damage the culture cells, giving a visible cytopathic effect(s) (CPE) 3. CPE's will be characteristic for different viruses and culture cell |
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What are two things to look for during serology? (the wording may not be getting at what the answer is, but this last section was hard to do)
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Detect the presence of either viral antigen in the sample or presence of host serum antibody
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What reaction must be made visible during serology? What type of reaction is this typically?
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The reaction b/w viral Ag and host Ab: it usually is an agglutination reaction.
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What are 3 types of methods/tags used to carry out serology?
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1. Fluorescent antibody(FA)2. ELISA test (enzyme linked immunosorbent assay, "snap test")
3. HAI (haemagglutination inhibition) |
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What is titre?
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The concentration of serum antibody compared to a particular organism
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Give an example of titre
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Serial dilution
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Explain titre dilution results/logic??
Umm...yeah, no clue; Bree, can u think of a way to word this question better? |
The greatest dilution at which a positive reaction is seen. The greater (higher) the titre, the greater (stronger) the immunity to the disease
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Is a single titre generally enough to make a diagnostic of the disease?
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No. Previous exposure, Vaccination, and exposure to similar organisms (i'm not sure what these are supposed to be, maybe other things that need to be taken into account? What do u think?)
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What is the diagnosis of the disease based on in regard to titre?
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A significant rise in titre from an initial (acute) sample to a second (convalescent) titre taken later (usually about 2 weeks)
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