Intro to Viruses Flashcards
Size of a virus vs. a bacteria
Viruses are smaller than the smallest bacteria
Viruses (can or cannot) be seen w/ a light microscope
Cannot
What type of nucleic acids to viruses have?
Either DNA or RNA, but NOT BOTH
Protein coating of a virus is called a ____?
Capsid
A capsid is composed of identical protein subunits called ____
Capsomeres
Some viruses have a lipid/protein membranous outer coating called ____
Envelope
Glycoprotein spikes or projections that protrude from the envelope are called ____
Peplomers
Viruses w/o envelopes are called ____
“Naked”
2 configurations a capsid can have
- Icosahdral (cubic)
- Helical
Nucleic acid + capsid = ?
Nucleocapsid
- Infectious form of “naked” viruses
Nucleic acid + capsid + envelope = ?
Virion
- Infectious form of enveloped viruses
Viral replication occurs only w/in a ____ ____
Living cell
How are viruses classified?
- Nucleic acid type
- Virus size, configuration, and composition
- Serological cross-reactivity of group Ags
6 steps of viral replication
- Attachment
- Penetration
- Eclipse
- Replication
- Maturation
- Release
What happens in the attachment stage of viral replication?
Virus binds to receptors on cell surface
What happens in the penetration stage of viral replication?
Virus enters cell (by engulfment, though fusion of cell membrane and viral envelope, or by direct passage)
What happens in the eclipse stage of viral replication?
Nucleic acid is freed from capsid; intact virion is not detectable. The protein coding of the nucleic acid is often inserted into the cell membrane.
What happens in the replication stage of viral replication?
Host cell manufactures viral nucleic acids and capsid proteins (at spearate locations w/in infected cells)
What happens in the maturation stage of viral replication?
New nucleocapsid or virons are assembled
What happens in the release stage of viral replication?
New nucleocapsids or virions are released from the host cell (budding or cell lysis)
What are the protein substances produced by virus-infected cells that act on infected and surrounding cells to interfere w/ viral replication
Interferons
Do interferons act on cells or viruses?
On cells NOT VIRUSES!
Interferons are most effective on host cells from same ____
Species
Why are antibiotics not effective against viruses?
Viruses do not have target components
Papilloma virus aka ____
Wart virus (known for genital warts)
Is there a vaccine available for papilloma virus?
Yes
Papilloma virus
- Rapid Ag tests available or not?
No
Papilloma virus
- Does or doesn’t grow in cell culture?
No
Papilloma virus
- What approach is used for lab diagnosis?
Molecular approach
- Use on materal from pap smear or other source
Measles
- Clincal presentation
- Rash on trunk and elsewhere
- 7-10 days of fiver
- Complications (i.e., encephalitis)
Mumps
- Clinical presentation
- Swollen parotid glands
- 7-10 days of symptoms
- Complications (i.e,. testicular involvement, CNS symptoms)
Measles and mumps
- What happened when U.S. introduced vaccine (MMR)?
Virtually eradicated in the U.S. but recent resurgences
Measles and mumps
- Rapid Ag detection available?
No
Measles and mumps
- Does it grow in cell culture?
Yes
Measles and mumps
- Ab detection useful?
Yes, for immune status determinations
Rabies virus
- Infection is “____” → CNS symptoms resulting in inability to what?
“Hydrophobia”; swallow, breathe
Rabies virus
- Chances of living w/ rabies
Little chance, routinely fatal
Rabies virus
- How does this virus travel in the body?
Travels through nerves from bite site to brain
Rabies virus
- Rapid Ag detection available?
No
Rabies virus
- Does it grow in cell culture?
Not well
Rabies virus
- How is it best diagnosed in humans?
Biopsy of nerve near bite site
Rabies virus
- How is it diagnosed in animals?
Examine brain for Negri bodies
Smallpox (Variola) virus
- How is it transmitted?
Person to person
Smallpox (Variola) virus
- Symptoms
- High fever
- Large vesicular lesions
Smallpox (Variola) virus
- Fatal in 10-30% of cases due to ____
Toxemia
Smallpox (Variola) virus
- Rapid Ag detection available?
No
Smallpox (Variola) virus
- Does it grow in cell culture?
Yes; do not attempt to isolate in hospital lab!!!!
Smallpox (Variola) virus
- What to do for smallpox diagnosis?
CALL CDC!!!
