HIV

Question 1

Genus

Answer 1

Lentivirus

• Note:*
• Part of the family Retroviridae

Question 2

The 3 structural genes (protein coded for)

Answer 2

• env (gp120 and gp41)
  
  • gp120
    
    • attachment to host CD4+ T cell
  • gp41
    
    • fusion & entry
• gag (p24 and p17)
  
  • capsid and matrix proteins, respectively
• pol
  
  • reverse transcriptase, aspartate protease, integrase
• Samplex alert:*
• Role of each protein
• Note:*
• gp120 is ligand of HIV
• CD 4 is the receptor in host cell

Question 3

Why is it difficult to develop HIV vaccine?

Answer 3

gp120 antigenicity changes rapidly

Question 4

Env genes

• General function
• Relationship of gp41 to gp120
• Most immunogenic region of gp120

Answer 4

• General function
  
  • Codes for envelope glycoproteins
• Relationship of gp41 to gp120
  
  • Both are envelope proteins
  • gp41 is a transmembrane protein (fusion protein) linked to a surface protein (attachment protein) gp120
• Most immunogenic region of gp120
  
  • V3 loop

Question 5

Where does the virus bind in host?

Answer 5

• Virus binds CD4 as well as a coreceptor, either:
  
  • CCR5 on macrophages (early infection); or
  • CXCR4 on T cells (late infection)

Question 6

Result of CCR5 mutation

Answer 6

• Homozygous CCR5 mutation
  
  • Immunity
• Heterozygous CCR5 mutation
  
  • Slower course

Question 7

Gag genes

Answer 7

• General role of gag proteins
  
  • Codes for structural proteins
• Role of p17
  
  • Outer matrix protein / MA
  • Directs entry of the dsDNA provirus into the nucleus, and is later essential for the process of virus assembly
• p24 location and function
  
  • Major capsid protein / CA
  • Contained in the cone-shaped icosahedral core
  • Consistent diagnostic antibody (marker of infection)

Question 8

General function of pol genes

Answer 8

Codes for enzymes (reverse transcriptase, protease, integrase)

Question 9

Function of HIV enzymes

• Function of reverse transcriptase
• Function of protease
• Function of integrase

Answer 9

• Function of reverse transcriptase
  
  • Synthesizes dsDNA from genomic RNA; dsDNA integrates into host genome
• Function of protease
  
  • Cleaves precursor polypeptides
• Function of integrase
  
  • Integrates viral DNA into host cell DNA

Question 10

The p24 gag protein is located in the _____ (envelope/matrix/capsid) of HIV

Answer 10

Capsid

Question 11

Glycoproteins 41 and 120 are located in the _____ (envelope/matrix/capsid) of HIV

Answer 11

Envelope

Question 12

People homozygous for mutations of which receptor are immune to HIV infection?

Answer 12

CCR5; HIV cannot invade cells without the presence of CCR5; heterozygosity leads to a slower course of illness

Question 13

The p17 protein is located in the _____ (envelope/matrix/capsid) of HIV

Answer 13

Matrix

Question 14

Pharmacologic correlates

• Inhibits fusion with host cell
• CCR5 receptor antagonist

Answer 14

• Inhibits fusion with host cell
  
  • Infuvirtide
• CCR5 receptor antagonist
  
  • Maraviroc