Term
| What are the receptors and coreceptors of HIV? When does it use each? What is the major cell surface molecule on HIV used to bind one of these? |
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Definition
-CD4+ (on T cell)
-CXCR4 (on T cell)
-CCR5 (on Mac)
-At the beginning, HIV uses CCR5 chemokine receptor and is thus macrophage-tropic
-Later in the infection, it uses CXCR4 chemokine receptor, making it more T-cell tropic
-HIV can bind to any CD4+ cell (TH cells, mac, and dendritic cells) and uses it *gp120 to do so |
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Term
| What are two genes from HIV that makes the cells it infects less susceptible to discovery, and how? |
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Definition
-The **Nef gene downregulates class I MHC expression
-The Tat gene inhibits cytokine synthesis |
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Term
| Describe the "deviation" of the immune response due to HIV and how that works? What cytokine levels would be expected to be elevated? |
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Definition
-Deviates toward a TH2 (humoral) response by removing/inhibiting TH1 cells to a higher degree
-Unfortunately, the humoral response is largely ineffective
-There would be more than usual IL-10, IL-4, and other TH2 cytokines |
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Term
| What are two methods of evasion that HIV uses concerning it's surface molecules? |
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Definition
-gp120 is one of it's major surface antigens
-gp120 undergoes both antigenic drift (mutation) and heavy glycosylation (blocks recognition) to avoid recognition
-Remember, gp120 is the molecule that binds CD4 |
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Term
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Definition
-Macrophages and dendritic cells are infected, but are resistant to HIVs cytopathic effect
-They therefore serve as reservoirs for infection |
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Term
| Describe the CD4+ and CD8+ interplay as the disease progresses? |
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Definition
-Starts out with twice as many CD4+ cells, and eventually progresses to having twice as many CD8+ cells
-The CD8+ cells wipe out the infected CD4+ cells very well, but as the TH cells numbers diminish, the amplification loop for CTL stimulation is eliminated |
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Term
| How can someone be immune or resistant? |
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Definition
-Immune if they are homozygous for a CCR5 mutation
-Resistant if they are homozygous
-Remember, CCR5 is on macs, so you take away the reservoir and the early infection plan of HIV |
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Term
| What are the diagnostic tests for HIV? What test will we want to run in newborns? |
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Definition
-ELISA (ELI assay), western blot (both rely on antibodies)
-We can also use PCR to amplify HIV genome
-We will want to do PCR in the case of newborns, as they will always have anti-HIV IgG from their HIV+ mother
-After 15 months, they will have their own IgG, however |
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Term
| What are the three important HIV antigens screened with in a Western blot? Which one can we test for directly? |
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Definition
-gp120
-gp41
-p24
-p24 can be tested for directly and is the first one around
-The other two are involved in CD4 binding |
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Term
| What percentage of HIV+ mothers will pass on the virus if untreated? |
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Definition
-30%
-Much less if treated (book says 8%, teacher says 0%) |
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Term
| What are the normal CD4+ levels in the plasma? |
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Definition
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