Retroviruses, AIDS, & Tumor Viruses Flashcards
when was AIDS first identified and what acronym was used to describe those infected?
-late 1970s-early 1980s: Homosexual men, heroine addicts, Haitians, and hmeophiliacs (4H risk group) began dying of normally-benign opportunistic infections in the US, defining a new disease
where is the origin of HIV?
appears to have evolved (genetic evidence) from simian virus in Africa (SIV) and spread through the rest of the world due to an increasingly mobile population and aberrant sexual behaviors
eating and harvesting ape meat
describe the retrovirus class
- large and diverse group of viruses
- unique replication cycle
- ubiquitous in vertebrates
- many are benign, cause little to no impact on the host cell or host animal
- others have significant pathogenicity cause disease and cancer
what genus and subfamily do HIV-1 and HIV-2 come from?
- genus: lentivirus
- subfamily: orthoretroviridae
spumaviruses (subfamily of retroviruses) do not cause human disease, however, what kind of structures do they make inside the cell
foamy structures
**what type of viruses are retroviruses?
- retroviridae: 2 subfamilies (othroretroviridae, spumaviridae)
- genome: (+) ssRNA: diploid, identical copies
- virion: enveloped
- proteins:
- reverse transcriptase (RNA->DNA, DNA->DNA)
- integrase
- protease
- *antivirals go after one of these proteins
how were retroviruses once classified?
by nucleocapsid structure & location in the particle
- A type: shell & hollow center, immature particle
- B type: circular NC, eccentric location
- C type: circular NC, central location
- D-type: cylindrical NC, central location (AIDS)
simple retroviruses only encode the ___, ___, ___, and ____ genes
gag, pro, pol, env
what is the replication cycle like for retroviruses?
- attachment: membrane fusion @ cell surf when it inserts itself doesn’t discriminate
- entry
- REVERSE TRANSCRIPTION: ssRNA genome to dsDNA
- INTEGRATION: virus dsDNA into host making provirus
- transcription from provirus
- translation
- assembly
- release by budding
- maturation: protease activity
why is retrovirus replication an exception to the rule?
because makes dsDNA intermediate and uses the nucleus even though it is (+)ssRNA
when does the reverse transcription of retroviruses occur?
initiates once nucleocapsid is in cytoplasm
- need high levels of NTPs present otherwise no transc.
- low NTP levels prevent reverse transcription
where does the reverse transcription of retroviruses occur?
-occurs within a large complex similar to nucleocapsid
can infection progress if reverse transcription does not occur?
no
T/F: reverse transcription in retroviruses is not promiscuous among genome copies
FALSE: “silent” when copies are identical
many different recombinations when different genomes are in the virion
**adds to high mutation=hard to develop vaccine
describe the integration process in retrovirus replication
- must access the nucleus during mitosis b/c requires dividing cells
- importation (mech unknown): can infect nondividing cells
- 3’ end processing of dsDNA
- attack target DNA, nick created
- host repair
is the integration process in retrovirus replication permanent?
yes, no mech to remove it
when is the provirus considered “endogenous” in retroviruses?
if integrated into the germ-line
integration can cause cancer. what are some integration identified oncogenes?
- TFs
- secreted growth factors
- growth factor receptors
- cell signal transduction pathways
many defective viruses are made during replication what are they typically missing?
at least one: gag, pol, or env
however, require complementary infection to make progeny
how is it that most retroviruses are benign?
- not cytopathic
- chronic infections exert small demand on cell and host resources (few percent of cell RNA and protein)
- do cause viremia and elicit an immune response, but host animals live normal lives for many months or years
- viruses are never limited by the host response
