HIV Virus and Drugs Flashcards
What is the env gene for in HIV?
What does it code for?
Cleavage product of envelope glycoproteins–> gp120 and gp41
gp41 = fusion and entry
gp120 = attachment to host CD4+T cells
What is the function of the pol gene in HIV
pol—reverse transcriptase, aspartate protease, integrase.
integrates the virus into the host
What is the function of the gag (p24) in HIV?
gag = capsid protein
What are the three structual genes in HIV?
env (gp120 and gp41):: Formed from cleavage of gp160 to form envelope glycoproteins.
gp120—attachment to host CD4+ T cell (docking). gp41—fusion and entry (transmembrane)
- *gag (p24)**—capsid protein
- ***
pol—reverse transcriptase, aspartate protease, integrase.
Explain how HIV gets into host?
What does it bind to?
Who may have immunity to this virus?
Reverse transcriptase synthesizes dsDNA from genomic RNA; dsDNA integrates into host genome.
Virus binds CD4 as well as a coreceptor, either
CCR5 on macrophages (early infection) or CXCR4 on T cells (late infection).
Homozygous CCR5 mutation = immunity.
Heterozygous CCR5 mutation = slower course.
What is the role of CCR5 in HIV
What about CXCR4
Virus binds CD4 as well as a coreceptor, either
CCR5 on macrophages (early infection) or
CXCR4 on T cells (late infection).
What do we use to screen for HIV? What characteritstics do we want this to have?
What do we confirm Dx with? What do we want this test to have?
Presumptive diagnosis made with ELISA (sensitive, high false-positive rate and low threshold, rule out test);
⊕ results are then confirmed with Western blot assay (specific, low false-positive rate and high threshold, rule in test).
When does pt have AIDS?
Three different ways to determine this:
Viral load tests determine the amount of viral RNA in the plasma.
1. AIDS diagnosis ≤ 200 CD4+ cells/mm (normal: 500–1500 cells/mm3).
- HIV-positive with AIDS-defining condition (e.g., Pneumocystis pneumonia)
- CD4+ percentage < 14%.
When is an ELISA and Western Blot a less reliable test?
ELISA/Western blot tests look for antibodies to viral proteins; these tests often are falsely negative in the first 1–2 months of HIV infection and falsely positive initially in babies born to infected mothers (anti-gp120 crosses placenta).
What pathogens are seen when viral count falls below 500
- Scrapable white plaque, pseudohyphae on microscopy = thrush or Albicans
- Unscrapable white plaque on lateral tongue= Hairy leukoplakia or EBV
- Biopsy with neutrophilic inflammation= BAcillary angiomatosis or Bartonella Henselae
- Biopsy with lymphocytic inflammation = Kaposis sarcoma or HHV-8
- Acid-fast oocysts in stool or Cryptosporidium (chronic watery diarrhea)
- Scrapable white plaque, pseudohyphae on microscopy
- Unscrapable white plaque on lateral tongue
- Biopsy with neutrophilic inflammation
- Biopsy with lymphocytic inflammation
- Acid-fast oocysts in stool
What disease do we worry about with AIDS pts when counts fall under 200
- MUltiple ring enhancing lesions on MRI
- Dementia
- Non enhancing areas of demyelination on MRI
- Ground glass opacities on CXR
- MUltiple ring enhancing lesions on MRI= brain abcess = Toxoplasmossis
- Dementia = from HIV
- Non enhancing areas of demyelination on MRI = PML from JC virus
- Ground glass opacities on CXR = PNeumocytisis pneumo from PCP
Aids pts has horrible cough with pleuritic chest pain and hemoptysis. You get chest xray and see several cavitations and inflitrates. What is the pathogen responsible, what are his counts below?
Aspergillus fumigatus
Below 100
AIDS pt has sensitivity to light, neck stiffness. The agent can be culture on Sabouraud agar and stains with indian ink
What is the causitive agent?
What is his CD4 count?
What is a better way to dxs this?
Cryptococcus neoformans
CD4 under 100
Latex agglutination test detects THICK polysaccharide capsular YEAST and “Soap bubble” lesions in brain.
Pt with AIDS comes in with trouble seeing. You lineary ulcers on endoscopic exam and see white spots on endoscopy.
What is the causitive agent?
What will you see on biopsy
CMV! can also cause retinitis, esophagitis, colitis, pneumonitis, encephalitis
Biopsy reveals cells with intranuclear (owl eye) inclusion bodies
seen with CD4 under 100
Single ring enhancing lesion in AIDs pt on MRI
Causitive agent?
EBV associated B-cell lymphoma (e.g., non-Hodgkin lymphoma, CNS lymphoma)
