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51 Cards in this Set

  • Front
  • Back
When were viruses first detected and what were they thought to be?
1890's, proposed as "poisons"
When were viruses first seen and how?
First seen in the 1930's via an electron microscope.
What is the definition of a virus?
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.
Viruses are obligate intracellular parasites, true or false?
What size range are viruses? Are they larger or smaller than bacteria?
20-300nm (20-3000*10^-9) in diameter. Smaller
What is the only type of microscope that is powerful enough to see a virus?
electron microscope
What is the central core made of?
DNA or RNA, can be single or double stranded
What is the name for the protective coat around a virus? What's it made of? What are the subuits also known as?
Capsid; made of protein subunits called capsomeres.
What is the core + capsid called?
Do all viruses have enelopes?
What does the outter covering (envelope) consist of?
proteins, lipids, carbohydrates, and in some viruses, "spikes
What is a virion?
The complete, infective viral structure
What are 6 ways of categorizing viruses?
1. Nucleai Acid
2. Enveloped vs. Non-enveloped
3. Capsid Architecture
4. Symptoms
5. Mechanism of transmission
6 Organ system affected
What are three types of capsid architecture and an example for each?
Helical: rabies, ebola
Polyhedral: polio, adenovirus
Complex: bacteriophage
List 6 routes of infection
Gastrointestinal Tract, Respiratory Tract, Injection (insects, vaccines), Skin Breaks, Urogenital Tract, Conjunctiva
Are viruses specific (ie, will only attack certein cells depending on what virus they are)?
Yes, they are specific
What is tissue tropism?
Viral specificity towards its host cell type
Give an example of tissue tropism?
Influenza virus affects respiratory cells.
List the steps in viral infection.
1. Adsorption/attachment
2. Penetration and uncoating
3. Synthesis of viral proteins
4. Maturation and assembly
5. Release
Describe adsorption/attachment.
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.
List the different kinds of penetration and uncoating
Endocytosis, Fusion, Direct penetration
Describe Endocytosis
receptor/virus complexes are invaginated on cell surface, combine w/lysozymes that digest the viral layers & release the nucleocapsid into the cell
Describe Fusion
fusion of viral envelope w/cell membrane, releasing nucleocapsid into cell
Describe direct penetration
Direct passage of small, non-enveloped virus through cell membrane.
What happens once the virus is inside the cell?
It's uncoated, the capsid and envelope are removed and the viral nucleic acid is released.
Describe the synthesis of viral proteins.
The viral genome is transcribed by the host cell machinery, producing viral proteins
What are two types of release (of the virus from the host cell) and describe them.
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.
List 4 viral effects on the host cells.
1. Cell lysis
2. Alteration in cell function
3. Persistent infection
4. Cell transformation
Give an example of a virus and its effect on the host cell
Poliovirus lyses motor neurons, leading to loss of function of corresponding muscles.
What causes the alteration in cell function?
The viral genome incorporation into the host cell's genome causes an alteration in host cell protein synthesis.
Give an example of how influenza virus alters it host cell
it alters respiratory epithelium and thereby decreasesciliary activity.
What are the three types of persistent infection?
Latent, chronic, and slow virus infection
Describe the qualities of a latent infection
Virus is in equilibrium w/host. Infectious virus is not produced but its genome is present in its host cell
Describe the qualities of a chronice infection
Virus does cause cell death, but symptoms are subclinical
Describe the qualities of a slow virus infection
Long incubation period (yrs). Virus continues to multiply slowly and causes protracted tissue damage.
Give 1 or more examples of latent infection, chronic infection, and slow virus infection
latent= herpes, cold sores
chronic= hepatites B in human
slow= HIV & scrapie
Which persistant infection type may be affected by stress and immunosuppression and what is the result of the stress or immunosuppression?
Latent infection; acute, intermittent flare-ups of clinical disease and virus is released and detectable during these episodes
What happens in cell transformation by a virus?
Viral transformation of normal cells into cancerous cells (oncogenic virus). Loss of the property of contact inhibition
Give some examples of cell transformation
Human carriers of hepatitis B vius are 100x more likely to develop liver cancer. Also, FeLV in cats.
List 3 ways to diagnose a viral disease
1. Complete history and physical exam
2. Procedures that demonstrate the presence of infectious virus
3. Serology
What must be done in getting a Complete History and Physical Exam?
Must secure appropriate tissue samples
What types of ways/machines are used to demonstrate the presence of infectious viruses?
1. Electron microscopy
2. Virus isolation/culture
3. PCR (polymerase chain reaction-identifies viral DNA)
Describe virus isolation/culturing
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
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)
Detect the presence of either viral antigen in the sample or presence of host serum antibody
What reaction must be made visible during serology? What type of reaction is this typically?
The reaction b/w viral Ag and host Ab: it usually is an agglutination reaction.
What are 3 types of methods/tags used to carry out serology?
1. Fluorescent antibody(FA)2. ELISA test (enzyme linked immunosorbent assay, "snap test")
3. HAI (haemagglutination inhibition)
What is titre?
The concentration of serum antibody compared to a particular organism
Give an example of titre
Serial dilution
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
Is a single titre generally enough to make a diagnostic of the disease?
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?)
What is the diagnosis of the disease based on in regard to titre?
A significant rise in titre from an initial (acute) sample to a second (convalescent) titre taken later (usually about 2 weeks)