Lecture 5: viruses pt 2 Flashcards
How do double stranded RNA enter/infect a cell?
dsRNA stays in the cytoplasm
- Can make -ssRNA and viral proteins
- Must encode it’s own RNA polymerase
What is the funtion of retroviruses?
+ssRNA that converts to into DNA
- DNA travels to nucleus
- Makes more dsDNA and mRNA
- mRNA travels to cytoplasm to make viral proteins
How is a virus assembled on a host?
- Empty capsid is laid down
- Insertion of Viral spikes into the host
- nucleic acid packaged into the capsid
- Uses host ATP energy to move viral parts around
essentially, the virus uses the host’s cells against itself
How is the virus released?
- Lysis by nonenveloped viruses
- Exocytosis by enveloped viruses
- budding by enveloped viruses
What happens when the cell undergoes lysis?
it kills the cell, ruptures the membrane and releases the virons
-typical of nonenveloped viruses
What happens when the cell undergoes budding?
viral proteins assemble at cell membrane, capsid fuses with membrane, pinches off for release
-typical of enveloped viruses
What happens when the cell undergoes exocytosis?
Virus particle enclosed in vesicle by the golgi, fuses with membrane, pinches off for release
-typical of enveloped viruses
What type of antiviral do you give patients?
depends on what area of the cycle you are trying to stop
What is the purpose of entry inhibitors? (antiviral)
it interferes with binding and fusion
What is the purpose of reverse transcriptase? (antiviral)
it inhibits reverse transcription
What is the purpose of integrase inhibitors? (antiviral)
inhibits viral DNA from host genome
What is the purpose of protease inhibitors?(antiviral)
inhibits virions from budding from host cell
What is the Acute type of infection?
it is the lytic stage; short term infection
- virus infects host cell
- virus multiplies
- virus lyses cell, releases
What is the persistent/chronic type of infection?
Can infected cells divide?
latent; long term infection
- become integrated into the host genome
- when host cell divides all resulting cells will contain the viral genes
- Cell does not lyse and appears normal
What are oncoviruses?
viruses that cause cancer
What are good treatment tactics for viruses?
- Vaccination
- Antivirus (only lessen severity)
- surgery
What is the cytopathic effect (CPE)?
virus induced damage that alters appearance of host cell
What are the different ways CPE could be present?
- Inclusion bodies
- Syncytia
- Changes in shape, size, etc
What are inclusion bodies?
aggregation of viruses or damaged organelles
What is syncytia?
fusion of multiple infected host cells
What are viruses that infect bacteria?
bacteriaphages; only specific bacteriaphages affect specific bacteria and do not harm human cells
What are other non-living infectious agents called?
Spongiform encephalopathies; tissue that looks like a sponge
What are the effects of spongiform encephalopathies?
What are they caused by?
- long period of latency before clinical signs
- Range from mental derangement to loss of muscle control
- progressive, often fatal
- Caused by prions, only made of proteins, no nucleic acid
How does (+/-) ssRNA infect a host?
-stays in the cytoplasm
- (-)ssRNA must be translated to (+)ssRNA
-becomes -ssRNA
most encode its own RNA polymerase
What type of polymerase do retrograde viruses use?
Reverse Transcriptase polymerase
How do oncoviruses cause cancer?
1) Activate proto-oncogenese
2) Viral genes that are cancerous are integrated into host genome
3) Turn off host cell tumor repressor
