05c: Retroviruses/HIV

Question 1

HTLV-1 and HTLV-2 are examples of (X) viruses that cause which diseases?

Answer 1

X = retroviruses;

T-cell leukemias (HTLV = human T-cell leukemia virus)

Question 2

HIV-1 and HIV-2 are examples of (X) viruses that cause which diseases? Which strain is less virulent?

Answer 2

X = retroviruses;

AIDS (HIV = human immunodeficiency virus); HIV-2 less virulent

Question 3

T/F: The DNA sequence that defines HIV-1 is most related to that which defines HIV-2.

Answer 3

False - no such thing as “single” DNA sequence that defines HIV

Question 4

Retroviruses are (enveloped/non-enveloped) viruses, about (X) nm in diameter.

Answer 4

Enveloped;

X = 100

Question 5

Retrovirus structure: inner shell is composed of (X) proteins and inner core composed of (Y) proteins. What’s contained within the core?

Answer 5

X = matrix
Y = capsid

1. Genome (2 copes of (+) sense mRNA)
2. Proteins (Reverse transcriptase, Integrase, Protease)

Question 6

T/F: HIV-1 genome is more complex than most retroviruses.

Answer 6

True - Encodes additional gene products (regulate virus replication and play role in pathogenesis)

Question 7

HIV: The (X) gene product functions as transcriptional transactivator. It can be released from infected cells and induce which processes in uninfected cells?

Answer 7

X = tat

1. Alter gene expression
2. Apoptosis

Question 8

HIV: The (X) gene product downregulates CD4 and MHC-1 expression.

Answer 8

X = nef

Question 9

Long-term non-progressors of HIV (are/aren’t) viremic. Some harbor HIV-1 variants that have mutant of (X) gene product.

Answer 9

Are (but not pathogenic);

X = nef

Question 10

Worldwide, most common method of HIV-1 transmission is:

Answer 10

M to F sex contact

Question 11

What are the routes of HIV-1 infection?

Answer 11

1. Sexual
2. Parenteral
3. Perinatal

Question 12

Primary receptor for HIV-1 is (X), found on (Y) cells. Which viral protein attaches to (X)?

Answer 12

X = CD4
Y = T-helper lymph and macrophages

gp120

Question 13

The major HIV-1 co-receptors are (X).

Answer 13

X = CCR5 and CXCR4

Question 14

HIV-1 establishes low-level infection in which cell types?

Answer 14

1. DCs

2. Langerhan’s cells

Question 15

T/F: Macrophages are the cells thought to facilitate HIV-1 dissemination from mucosa to lymph nodes.

Answer 15

False - DCs and Langerhan’s cells

Question 16

Individuals thought to be resistant to HIV-1 infection are (homo/hetero)-zygous for which gene alteration?

Answer 16

Homozygous;

Deletion in CCR5 gene

Question 17

A group of long-term non-progressors of HIV-1 expresses high levels of (X), which compete with the virus for (Y).

Answer 17

X = chemokines (MIP-1a, MIP-2b, RANTES)
Y = CCR5 binding

Question 18

List the steps in HIV-1 life cycle that have been targeted by anti-retroviral drugs.

Answer 18

1. Receptor binding
2. Entry
3. Integration
4. Proteolytic maturation

Question 19

HIV-1: (X) co-receptor is expressed on T-cells and macrophages. (Y) co-receptor is preferentially expressed on T-cells.

Answer 19

X = CCR5
Y = CXCR4

Question 20

HIV-1: drugs block entry of virus into cell by preventing (X) from..

Answer 20

X = gp41

Adopting fusion-competent conformation

Question 21

Reverse transcriptase synthesizes (X) from (Y). AZT and other anti-retroviral drugs block this step via which mechanism?

Answer 21

X = dsDNA
Y = ssRNA

They’re nucleoside analogs that compete with normal nucleoside (terminate DNA chain elongation)

Question 22

Non-nucleoside inhibitors of reverse transcriptase function as anti-retroviral drugs via which mechanism?

Answer 22

Bind RT near active site and block its activity

Question 23

HIV-1: lack of proofreading activity of (X) polymerase(s) contribute to viral variants.

Answer 23

X = RNA-dependent DNA Pol (reverse transcriptase) and RNA polymerase II

Question 24

T/F: HIV-1, like most retroviruses, cannot productively infect non-dividing cells.

Answer 24

False

Question 25

For most retroviruses, entry of DNA into nucleus requires (X). HIV-1 has (Y) protein that allows DNA transport in absence of (X).

Answer 25

X = nuclear membrane breakdown (during cell division)
Y = CA

Question 26

T/F: Assembled HIV-1 virions, released from cell, are mature.

Answer 26

False - contain uncleaved polyproteins (must undergo proteolytic maturation)

Question 27

High rates of (X) during HIV-1 infection result in extensive sequence heterogeneity and outgrowth of viral strains with higher (Y) capacity.

Answer 27

X = replication, mutation, and recombination
Y = replicative and pathogenic

Question 28

In acute HIV-1 infection, there’s a sudden drop, followed by rebound increase, in (CD4 cells/viral load).

Answer 28

CD4 cells

Question 29

In acute HIV-1 infection, there’s a sudden spike, followed by sudden drop, in (CD4 cells/viral load).

Answer 29

Viral load

Question 30

In acute HIV-1 infection, (CD4 cells/viral load) initially spikes. (X) cells also spike, but then steadily decline.

Answer 30

Viral load;

X = HIV-1 specific CTL

Question 31

During latent phase of HIV-1 infection, replication is (stopped/slow).

Answer 31

Still very high! (10^8 to 10^9 virions/day)

Question 32

List examples of HIV-1 induced T-cell abnormalities.

Answer 32

1. Lack of Ag response
2. Impaired proliferation
3. Impaired IL-2 expression (T cell growth)
4. Shift from Th1 (CM) to Th2 (humoral) profile

Question 33

List examples of HIV-1 induced macrophage abnormalities.

Answer 33

Impaired chemotaxis, phagocytosis, and cytokine production

Question 34

List the general mechanisms by which HIV-1 kills.

Answer 34

1. Direct killing (cytotoxicity)
2. Syncytium formation
3. Immune attack/apoptosis

Question 35

Worldwide HIV-1 epidemic has epicenters in which countries?

Answer 35

1. Sub-saharan Africa
2. India
3. China
4. Russia

Question 36

T/F: Significant exposure to body fluids from HIV+ person has 30% transmission risk.

Answer 36

False - 0.3%! (Very low).

30% transmission risk for HBV

Question 37

CDC recommends primary assay for HIV test that detects (X).

Answer 37

X = HIV p24 Ag and HIV Ab

Question 38

CDC recommends secondary assay for HIV test. If primary assay is (negative/positive), the secondary assay detects (X). What’s the point of this second assay?

Answer 38

X = HIV-1/HIV-2 Ab

Differentiate between HIV-1 v. HIV-2

Question 39

T/F: Patients can opt-out of screening tests for HIV.

Answer 39

True

Question 40

T/F: Written consent is required for HIV testing.

Answer 40

False - general consent for medical care is sufficient

Question 41

List some side effects of HAART.

Answer 41

1. Fat redistribution
2. Hypercholesterolemia
3. Other specific drug adverse effects