Chapter 26: Retroviridae, HIV, and AIDS

Question 1

Contact inhibiton

Answer 1

Normal cells, when growing on a plate, will form a single layer and stop dividing when they touch each other

Malignant cells lose contact inhibition and pile up

Question 2

Rous sarcoma virus

Answer 2

Acute transforming virus - carries intact oncogene within viral genome
ONLY known acute transforming virus that is non-defective andhas full RNA genome needed for replication

Src encodes Transmembrane protein that phosphorylates tyrosine ten times the normal rate

It is a retrovirus

Question 3

HTLV-1

Answer 3

Linked to paralytic disease: tropical spastic paraparesis

Induces leukemia

Question 4

Describe HIV structure

Answer 4

Sperical enveloped virion with central cylindrical nucleocapsid
Virion core: 2 identical SS RNA pieces
NC proteins bound to RNA
3 enzymes: protease, reverse transcriptase and integrase

p24-capsid shell
surface glycoproteins: gp120 gp41

Question 5

nef

Answer 5

crucial to HIV virulence and evasion of the host immune system
Downregulates expression of both and CD4 and MHC class I

Question 6

vif

Answer 6

blocks the effects of APOBEC3 enzyme

Question 7

APOBEC3

Answer 7

break down newly synthesized viral DNA

Question 8

In order for fusion and translocation of HIV across the cell membrane what must happen

Answer 8

CD4 binds gp 160

and coreceptor CCR5 or CXCR4 (helper T cells and Mo)

Question 9

If pts fail to produce normal levels of CCR5 what happens?

Answer 9

appears to be resistant to HIV infection

Question 10

What are the stages of HIV?

Answer 10

1. acute viral illness: viremia, symptoms like mononucleosis, 1 month after exposure
2. Clinical latency: 8 years, no symptoms, steady gradual destruction of CD4 T cells
3. AIDS: 2 years then death, Opportunistic infection,

Question 11

Viral load

Answer 11

High levels correlates with a greater risk of opportunistic infection
Tells you the speed of the train
*CD4 count tells you where the train currently is

Question 12

Multinucleated giant cells

Answer 12

T-cell to T-cell fusion allows virus to pass from infected cell to uninfected cell without contacting blood and protects from antibodies

Question 13

B-cells and HIV

Answer 13

Polyclonal activation
Hypergammaglobulinemia
Diminished ability to produce antibodies in response to new antigens or immunizations

Question 14

Monocytes and Mo and HIV

Answer 14

Serve as reservoirs for HIV as it replicates, protects from immune system

Migrate across BBB carrying HIV to CNS

Question 15

What malignancies do AIDS pts often suffer from?

Answer 15

B-cell lymphoma: EPV

Kaposi’s sarcoma: HHV-8, lesions red to purple, plaques or nodules and arise on skin all over the body

Question 16

What bacterial and mycobacterial infections do HIV pts often suffer from?

Answer 16

Streptococcus pneumoniae
Mycobacterium tuberculosis
Mycobacterium avium-intracellulare (MAI): non tuberculous mycobacterium, smoldering

Question 17

What fungal infections do AIDS pts often suffer from?

Answer 17

Candida albicans
Cryptococcus neoformans: cryptococcal meningitis, fever no Kernigs
Histoplasma capsulatum
Coccidioides immitis
Pneumocystis jiroveci penumonia (MOST COMMON)

Question 18

What is the most common opportunistic infection in the U.S among pts with AIDS?

Answer 18

Pneumocystis jiroveci pneumonia

Question 19

What viral infections do AIDS pts often suffer from?

Answer 19

Herpes zoster: shingles
EBV: oral hair leukoplakia (hairlike projections arising from side of tongue), B-cell lymphoma
Herpes simplex
Cytomegalovirus

Question 20

What protozoal infections do AIDS pts often suffer from?

Answer 20

Toxoplasma gondii: mass lesions in the brain
Cryptosporidium
Microsporidia
Isospora belli (#1 cause of diarrhea in AIDS pts)
- diarrhea

Question 21

How to diagnose HIV

Answer 21

ELISA: detects Abs, sensitive but gives false positive results
then Western blot test

PCR for early weeks of infectivity