Lecture 10

Question 1

Why aren’t all vaccines 100% effective?

Answer 1

vaccines are dependent on the individual’s immune response, so some immune systems may not generate an adequate response

Question 2

Why type of virus is HIV?

Answer 2

a retrovirus

Question 3

Why discovered HIV?

Answer 3

Gallo and Montagnier

Question 4

What is happening to the CD+ T lymphocytes during acute HIV syndrome?

Answer 4

As RNA copies rapidly increase, CD+T cell count decreases

Question 5

What occurs during the classical latency phase of HIV?

Answer 5

virus is in the body but mostly inactive, however CD+ T cells are still slowly declining

Question 6

What causes HIV to lead to death?

Answer 6

because CD+ T cells are so low, an opportunistic disease will lead to death

Question 7

When does AIDs develop in HIV?

Answer 7

when the CD+ T cell count drops extremely low

Question 8

Why is there no cure for AIDs yet?

Answer 8

• complex replication
• high mutation rate due to RT enzyme error
• evolves into quasispecies
• antigens are constantly changing

Question 9

Describe the structure of HIV.

Answer 9

• enveloped
• two copies of +ssRNA
• six accessory proteins
• diploid
• spike protiens: transmembrane (anchor envelop to matrix) and surface subunit (binds to host receptor)

Question 10

How does HIV enter host cell?

Answer 10

gp120/gp41 spike protein complex binds the host CD4 receptor of T cells to CCR5 to induce conformation change and fusion peptides fuse viral and host membranes together

Question 11

What can cause people to be resistant to HIV?

Answer 11

A defective CCR5

Question 12

Describe HIV replication cycle.

Answer 12

• HIV fuses to membrane and protein capsid dissolves
• RT uses +ssRNA to make dsDNA
• dsDNA integrates into host DNA
• viral RNA transcripts are made and exported to cytoplasm for translation and synthesis of viral proteins
• virus particles are assembled and viral proteins cleave most tethering to release virions without cell lysis

Question 13

What are the two methods that HIV uses to infect cells?

Answer 13

• regular HIV binding and replication

- budding directly from one infected cell to another (formation of syncytia)

Question 14

Why does the replication cycle of HIV have a high mutation rate?

Answer 14

RT is very error prone

Question 15

What is immune escape?

Answer 15

the constantly changing of envelope antigens

Question 16

What causes progression to AIDS?

Answer 16

• insertion of viral genome into host genome may destroy host gene regulation

Question 17

What might potential anti-HIV drugs do?

Answer 17

• prevent fusion of viral and host membrane

- inhibit RT, integrase, or HIV protease

Question 18

What is AZT?

Answer 18

an anti-HIV drug that blocks RT activity

Question 19

What is Fuzeon?

Answer 19

an anti-HIV drug that blocks fusion of HIV envelop with host cell plasma

Question 20

How does HIV progress from HIV to AlDS?

Answer 20

tumor formation, lysis, persistent infection, latent infection, and cell fusion