Viruses Part D Flashcards
Exam 2
What are the steps of retroviral multiplication? (Ex: HIV)
+ RNA –> -DNA
- Uses reverse transcriptase on +RNA (template) to make (-)DNA
- Reverse transcriptase uses the RNA to make DNA, then RNase is used to care up the (+) RNA template
- DNA –> (+,-) dsDNA
- DNA dependent DNA polymerase is used to give viral DNA (replicative form)
- (+,-) dsDNA –> +RNA
- Copies of the genome
- (+,-) DNA –> mRNA
- Making proteins for assembly
- (+,-) dsDNA –> +RNA
HIV structure
- Enveloped
- Spikes made up of 2 proteins:
- Stem (gp41)
- Globe like head (gp120)
- CD4 receptors found on helper T cells
Possible infections and disease acquired from HIV
Can cause chronic and acute infections
Disease acquired: AIDS
-Transmitted through saliva/spit, blood/bodily fluids
-Decrease in # of T cells that are (+) CD4 when infected
-Affects immune response
-Diagnosed when there are signs of infection
What is unique to Hepatitis B Virus (HBV)?
- Reverse transcribing DNA virus
- Genome has complete (-) strand (as a template) but partial (+) strand (partial ds) (looks like a ring, circular)
What are cytopathic effects?
Degenerative changes or abnormalities in the infected host cells
What are cytocidal effects?
Cell death caused by acute infections
- If significant enough, can affect cell tissue
- Some tissues can recover quickly (intestinal epithelium, mucus later in intestine)
- Other tissues cannot recover, may not be able to regenerate
What is a tumor?
A cytopathic effect of abnormal new cell growth due to loss of regulation of cell division
What is a synonym of tumor?
Neoplasia
What is anaplasia?
A cytopathic effect of reversion to a more primitive form
- Loss of specialized metabolic activities
- Reliance on anaerobic metabolism (usually use aerobic)
- Abnormal shapes
- Often invade surrounding tissues
What are benign tumors?
Compact mass that remain in place, typically not dangerous
What are malignant tumors?
Mass throughout the body (metastasis), which is the leading problem of cancer since it is hard to eliminate
What are proto-oncogenes?
Genes that encode proteins to increase growth and division by sending the cell into mitosis, or triggering cell division
What are tumor suppressor genes?
Genes that encode proteins that block division/shut it off/causes programmed cell death to keep an appropriate level of living cells
What are oncoviruses?
Viruses that are known to cause cancer. Commonly dsDNA but some are retroviruses
What are the mechanisms of oncoviruses to integrate their viral genes into the host chromosome?
- Viral proteins inactivate tumor suppressor proteins
- Rb: tumor suppressor protein involved in maintaining normal cell cycling (viral genes integrate between this protein)- The inactivation results in hyperproliferation (too much cell division)
- p53: tumore suppressor protein that initiates cell cycle arrest or programmed cell death - Inactivation results in absence of cell death or continuation of cell division at inappropriate times
- The inactivation results in hyperproliferation (too much cell division)
- Virus oncogenes up regulate host cell division
- Viral proteins activate host genes involved in cell division
- Viral genome incorporates near a proto-oncogene upregulating transcription of that gene
What do abnormal cell growth processes look like?
- Viral proteins inactivate tumor suppressor proteins
- Tumor suppressor genes inactivated
- Proto-oncogenes unaffected
Result: Too much cell growth and division
OR - Viral oncogene attaches to a promoter
- Increases proto-oncogene activity, increasing growth and division
- Tumor suppressor genes are not affected
Result: Too much cell growth and division
What part of the body does Hepatitis B virus cause cancer in?
Liver
What are virions?
Fully assembled viral particles (infectious)
What are viroids?
Infectious ssRNA molecules (not associated with translation or any proteins)
-Infect plants
What are satellites?
Subviral particles (DNA or RNA) that are not full viruses, consist of nucleic acid encapsulated by protein (needs a helper virus to survive) -Infects plants, animals, and bacteria
What are prions?
Infectious protein (not associated with any nucleic acids)
- Use normal proteins to replicate
- Causes proteins to denature and misfold when the prions are present
- Infect animals and plants
What is a disease that is caused by prions?`
- CJD (neurodegenerative disease) in Humans
- Mad cow disease (effects parts of the brain that responsible for sleep, can’t sleep and die) in mammals
Prions are incurable
How are prions transmitted?`
- Through exposure to infected tissues, can commonly be spread through animals when feeding leftover slaughter that was infected with prions to other animals
- Inheritance
- Sporadic
Why are prions difficult to inactivate?
Prions are highly resistant to permanent denaturation
