Micb 202: Virology - Chapter 2C - Retroviruses

Front 1

All retroviruses can insert thier genome into host's for germline transmission (T/F)

Back 1

T

Front 2

retroviruses can be oncogenic (T/F)

Back 2

T

Front 3

How man genera in retrovirus family?

Back 3

7

Front 4

HIV belongs to the ___ genera

Back 4

Lentivirus

Front 5

How are the symptoms of AIDS characterized?

Back 5

susceptibility to opportunistic pathogens

Kaposi's sarcoma

B cell lymphoma

Front 6

Avarate time from initial time of infection to disease is longer in individuals infected with HIV-_

Back 6

HIV-2

Front 7

Describe the retrovirus genome

Back 7

diploid, two identical ssRNA

Front 8

T/F: retrovirus DNA is synthesized and processed by the host cell mRNA 'handling machinery'

Back 8

T

Front 9

retrovirus DNA is associated with a specific ___ (____) which is used to prime replication

Back 9

RNA (tRNA)

Front 10

What does the retrovirus use tRNA for?

Back 10

to prime replication

Front 11

T/F: retrovirus RNA lacks a 5' cap and a 3' polyA tail

Back 11

F. It has both of these

Front 12

What is the gene order in all retroviruses?

Back 12

5'-gag-pol-env-3'

Front 13

HIV is classified as a ___ retrovirus because it contains additional genes involved in regulation of virus expression

Back 13

complex

Front 14

Retroviruses are (enveloped|non-enveloped) viruses approximately ___ nm in diamater

Back 14

enveloped
110 nm

Front 15

SU (surface) protein = gp___

Back 15

gp120

Front 16

What are SU and TM derived from?

Back 16

gp160

Front 17

TM (transmembrane) protein = gp___

Back 17

gp41

Front 18

SU and TM connected by a ___ bond

Back 18

disulphide

Front 19

SU and TM are derived from ___ gene

Back 19

env

Front 20

SU is involved in ___

Back 20

receptor binding

Front 21

TM is involved in ___

Back 21

membrane fusion

Front 22

HIV nucleocapsid classified as ___ in structure

Back 22

complex

Front 23

CA (capsid) protein derived from ___ gene

Back 23

gag

Front 24

The two RNA molecules of HIV are protected by ___

Back 24

nucleocapsid proteins

Front 25

Between the capsid (CA) and the envelope is the ___ protein

Back 25

MA (matrix)

Front 26

MA is derived from ___ gene

Back 26

proteolytic cleavage of gag gene product

Front 27

RT and IN come from ___ gene

Back 27

pol

Front 28

the protease (PR) responsible for cleavage of gag and pol gene products is encoded in ___ gene

Back 28

gag

Front 29

When does PR become activated?

Back 29

When the virus has budded from the cell

Front 30

What are the products of the gag gene?

Back 30

NC
CA
MA
PR

Front 31

What are the products of the env gene?

Back 31

SU
TM

Front 32

What are the products of the pol gene?

Back 32

IN
RT

Front 33

What is the function of IN?

Back 33

integrates viral DNA into host genome

Front 34

What is the function of RT?

Back 34

makes dsDNA from ssRNA

Front 35

SU and TM work as a team. SU is used for ___, and TM is used for ___.

Back 35

receptor binding
membrane fusion

Front 36

What is the HIV receptor? Co-receptor?

Back 36

CD4 surface molecule on T helper cells and some macrophages

chemokine receptor CXCR4 (T cells)
OR
CCR5 (macrophages)

Front 37

What is the function of CD4 in T cells?

Back 37

it is a co-receptor to the T-cell's antigen receptor

Front 38

Viral strains of HIV are assigned into groups based on what?

Back 38

the co-receptors used

the groups are: R5, X4

Front 39

Do chimpanzees see a decline in immune system functionality after HIV infection?

Back 39

no

Front 40

How is HIV transmitted?

Back 40

intimate contact of body fluid

Front 41

How is HIV spread to the target organs?

Back 41

bloodstream in the blood plasma and/or within lymphocytes or macrophages

Front 42

What systems are targeted by HIV?

Back 42

lymphoreticular
hematopoietic
nervous

Front 43

What are the critical cellular targets of HIV?

Back 43

dendritic cells (antigen presenters)
CD4-positive T lymphocytes
macrophages

Front 44

What is the function of CD4+ T cells?

Back 44

activation of macrophages (to kill intracellular pathogens)
activation of B cells (Ab production)

Front 45

T/F: macropages also function as antigen presenting cells

Back 45

T

Front 46

HIV replication cycle: Begins with attachment of viral glycoprotein ___ to ___

Back 46

gp120 (SU) to CD4 cell surface marker

Front 47

HIV replication cycle: After gp120 binds to CD4, ___ or ___ is recruited to the site and also binds the virus.

Back 47

CCR5 (macrophages)
CXCR4 (T cells)

Front 48

HIV replication cycle: After binding of gp120 to receptor and co-receptor, ___ inserts itself in ___, causing fusion of virus envelope with host cell membrane

Back 48

gp41 (TM)
host cell membrane

Front 49

HIV replication cycle: After fusion of virus envelope with membrane of host cell, ___ is released into the cytoplasm

Back 49

virus core

Front 50

HIV replication cycle: The DNA intermediate that is produced by the RT is known as a ___

Back 50

provirus

Front 51

T/F: RT is an enzyme unique to Retroviruses

Back 51

T

Front 52

What are two activities of RT?

Back 52

RNA dependent DNA polymerase
RNase (enzyme to degrade RNA)

Front 53

RT of the RNA genome: RT uses a ___ as a primer to make a DNA copy of the RNA genome

Back 53

tRNA

Front 54

RT of the RNA genome: What does RT initially create?

Back 54

DNA:RNA hybrid molecule

Front 55

RT of the RNA genome: What happens to the DNA:RNA hybrid created?

Back 55

most of the RNA is removed, but just enough is left to use as a primer for synthesis of the complementary DNA strand

Front 56

RT of the RNA genome: What removes the RNA portion of the hybrid DNA:RNA?

Back 56

RNase H

Front 57

RT of the RNA genome: What is used as a primer for the complementary DNA strand?

Back 57

A portion of the RNA left by the RNase H

Front 58

HIV replication cycle: What is the "pre-integration complex"?

Back 58

provirus + integrase

Front 59

HIV replication cycle: What does the integrase portion of the "pre-integration complex" do?

Back 59

catalyzes integration of provirus into host cell DNA at random site

Front 60

HIV replication cycle: After integration into genome, the (host | virus) cell enzyme RNA polymerase II "takes over" replication and transcription

Back 60

host

Front 61

HIV replication cycle: What does host cell RNA polymerase II do?

Back 61

takes over replication and transcription of viral genome using integrated provirus as template

Front 62

What takes over replication and transcription of viral genome using integrated provirus as template?

Back 62

RNA polymerase II from the host cell

Front 63

___ ribosomes translate HIV mRNA to produce Env proteins

Back 63

ER-bound

Front 64

The Env proteins are transported through the ___ where they are glycosylated and cleaved to form the ___ and ___ complex

Back 64

Golgi
SU
TM

Front 65

SU and TM (freshly made) are localized to ___

Back 65

the plasma membrane of infected cell

Front 66

T/F: HIV lyses the cell to escape

Back 66

F. It buds off.

Front 67

During or shortly after budding, HIV undergoes a maturation process mediated by ___

Back 67

PR (protease)

Front 68

What does protease do during HIV maturation?

Back 68

cleaves specific sites in the Gag and Gag/Pol polyprotein, resulting in a morphologically distinct core

Front 69

When the ribosome starts translation at the 5' end, and stops at the stop codon, what is produced?

Back 69

the Gag precursor, cleaved to yiled MA, CA, NC, and PR

Front 70

T/F: The Gag and Gag/Pol precursors are cleaved immediately after translation.

Back 70

F. They are cleaved much later, during the maturation process (during budding or shortly after)

Front 71

When the ribosome slips at the first stop codon in the retroviral mRNA (__% of the time), what is produced?

Back 71

The Gag/Pol precursor (recall, the Pol portion gives rise to RT and IN)

Front 72

How are env gene products made?

Back 72

splicing out the gag and pol genes like introns (inside the nucleus), then translation on the rough ER

Front 73

In what part of the cell is the env mRNA portion spliced out of the retroviral mRNA?

Back 73

nucleus

Front 74

After translation on the rough ER, what happens to the env gene product?

Back 74

passed thru Golgi
glycosylated
cleaved into SU and TM
inserted in cell membrane

Front 75

T/F: most cases of primary HIV infection are asymptomatic

Back 75

T

Front 76

Symptoms of primary HIV infection may include...

Back 76

influenza-like illness lasting 2 weeks

Front 77

What is the termed used to describe production of Ab to HIV virus during primary infection?

Back 77

Seroconversion

Front 78

How long can the asymptomatic period of HIV infection last?

Back 78

many years

Front 79

What is AIDS defined as?

Back 79

< 200 CD4+ cells per microlitre

Front 80

What are five of the immune system abnormalities seen with AIDS?

Back 80

less Ab responses
less MHC class II expression
less CD4+ T cells
less IL-2

Front 81

What are the two models used to explain AIDS caused by HIV?

Back 81

Direct Cell Killing: immune system kills cells expressing viral antigens

Antigenic Diversity: New antigenic variants of HIV continually arising overwhelms immune system, causing collapse

Front 82

What are potential vaccine candidates for HIV?

Back 82

inactivated virus (may not be suitable due to denaturing of epitope on glycoprotein, and safety concerns)

subunit vaccines
synthetic peptides
DNA vaccines

Front 83

What are the two classes of HIV antiviral drugs?

Back 83

RT inhibitors: AZT looks like a nucleotide after cell phosphorylates it to AZT-TP, but has an azide group instead of hydroxyl. Blocks DNA synthesis.

Protease inhibitors: inhibit HIV-1 protease, preventing maturation of virus.