Retroviruses, AIDS & Tumor Viruses

Question 0

Retrovirus Biology

subfamilies, genome, virion, characterization

Answer 0

subfamilies: orthoretroviridae, sumaviridae
genome: (+)ssRNA (diploid identical copies)
virion: enveloped
characterization: via genome contents

Question 1

Basic features of retroviruses

Answer 1

many are benign, some are linked to cancer
unique replication cycle: RNA->DNA, reverse transcriptase
known as Retroviridae: two subfamilies

Question 2

Describe Spumaviruses

Answer 2

don’t cause human disease

create foamy structures inside the cell

Question 3

Simple retroviruses only encode what genes?

Answer 3

Gag
Pro
Pol
Env

Question 4

Describe replication of retroviruses

Answer 4

Attachment
Entry
Reverse transcription
Integration
Transcription from provirus
Translation 
Assembly
Release
Maturation-protease activity

Question 5

Describe reverse transciption

Answer 5

defining feature of retroviruses
initiates once nucleocapsid is in cytoplasm
need higher levels of NTPs, low NTP prevents reverse transcription
infection can’t progress if reverse transcription doesn’t occur

Question 6

Describe mutations in retroviruses

Answer 6

many different recombinations occur when the virion contains different genomes
this is why retroviruses are hard to control, mutations outpace the immune systems ability to respond
“reverse transcription is promiscuous btwn genome copies)

Question 7

Describe integration of retroviruses

Answer 7

requires access to the nucleus and dividing cells during mitosis
but can also infect non-dividing cells: importation
integration is permanent
if integrated into germ line then it become inherited (endogenous)

Question 8

Describe how retroviruses may relate to cancer

Answer 8

integration may occur in one of the regulators of cell growth (oncogenes)
example: transcription factors, growth factor receptors ect
if this occurs it may lead to cancer

Question 9

Retrovirus Disease

Answer 9

many defective viruses made during replication
many retrovirus infections are benign
some cause significant disease

Question 10

What are the three basic categories of retroviruses

Answer 10

Slow retroviruses
Cytopathic retroviruses
Acute transforming viruses

Question 11

Describe slow retroviruses

Answer 11

effect is like high-level mutagenesis
eventually results in tumorigenesis
example: leukemia viruses

Question 12

Describe cytopathic retroviruses

Answer 12

minority of retroviruses

cause tissue damage directly

Question 13

Describe Acute transforming viruses

Answer 13

induce rapid tumor formation: carcinogenic in nature
carry host genes-mitogenic or antiapoptotic
replication often defective

Question 14

Describe HTLV

how many types,

Answer 14

4