Lecture22: HIV and AIDs Flashcards Preview

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Flashcards in Lecture22: HIV and AIDs Deck (26):
1

HIV ___ is responsible for causing AIDS in much of West Aftica but HIV___ causes AIDS throughout the rest of the world

  • West Africa: HIV-2
  • Rest of world: HIV-1
  • (note the differences) 
    • 40% genetically different
      • HIV-1 is more progressive and more infections 
    • Different origins
      • HIV-1:
        • single subspecies of the chimpanzee (Pan troglodytes troglodytes)
      • HIV-2: 
        • Sooty mangabey (Cercocebus atys)

2

  • What are the four groups of HIV-1?
  • What is the most important group?

  • Groups: M,N,O,and P (note that within each group is 9 subtypes (A,B,C, etc.))
    • M is the most important group (the Major group)

3

Structure of HIV virus

  • Retrovirus containing 2 positive strands of ssRNA
  • Has reverse trancriptase and integrase 
  • Glycoproteins gp120 and gp41 on the outer membrane are involved in adsorption and penetration 
  • Capsid protein p24 (this can be found in blood as an indicator of HIV progression)
  • p17: is a matrix protein that forms the iner surface of the viral membrane and orchestrates viral assembly 
  •  

4

Are the envelop glycoproteins of HIV-1 and HIV-2 cross- reactive 

No they are distinct and thus not immunologically cross-reactive 

5

  • HIV Genomic Organization
    • What are the major structural genes of HIV

6

Binding and entry of HIV

  • CD4 is high affinity receptor for gp120 
  • Co-receptor 
    • consists of the cell surface receptors that bind chemokines, CXCR4 or CCR5
  • ​Surface expression of CXCR4, CCR5 on CD4 T cells, DCs and Macrophages defines the cellular targets for HIV

7

what are the major cellular reservoirs of HIV in the host

  • Latently-infected (integrated) memory T cells 
    • half life of months/year
  • Infected macrophages 
    • have half life of months/year

8

Clinical Disease progression of HIV/AIDS

9

CD4+/CD8+ cell ratio in healthy individual is ___ while in an HIV infected individual it is 

  • 2:1
  • 1:1

10

Normal CD4 T cell count is 

600-1200 cells/mL

11

Mechanisms of CD4+ cell depletion

  • It can be caused by:
    • Direct infection of HIV
    • Chronic immune activation causes apoptosis of CD4+ T cells
    • AICD (activation induced cell death)  killing of CD4+ T cells carrying gp120 viral protein 
    • CTL activity against normal CD4+ T cells
    • Bone marrow toxicity--> inhibition of lymphocyte regeneration 

12

Why antibody responses not effective against HIV

  • Results from Low Fidelity of reverse transcriptase 
    • leads to production of mutant virions with distinct antigenic make up
      • this means that the Abs can't keep up with the changing virions 

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