First Aid/ (4.16) Quiz 3:
2024/2025
HIV diagnosis
- CORRECT ANSWER -Presumptive diagnosis made with ELISA (sensitive, high false+
rate and low threshold, rule out test); ⊕ results are then confirmed with Western blot
assay (specific, low false+ rate and high threshold, rule in test).
Viral load tests determine the amount of viral RNA in the plasma. High viral load
associated with poor prognosis. Also use viral load to monitor effect of drug therapy.
AIDS diagnosis ≤ 200 CD4+ cells/mm3 (normal: 500-1500 cells/mm3). HIV-positive with
AIDS-defining condition (e.g., Pneumocystis pneumonia) or CD4+ percentage < 14%.
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).
Time course of untreated HIV infection
- CORRECT ANSWER -Four stages of untreated infection:
1. Flu-like (acute)
2. Feeling fine (latent)
3. Falling count
4. Final crisis
-During latent phase, virus replicates in lymph
nodes.
-Red line = CD4+ T cell count (cells/mm3); blue line = HIV RNA copies/mL plasma.
-Blue boxes on vertical CD4+ count axis indicate moderate immunocompromise (< 400
CD4+ cells/mm3) and when AIDS-defining illnesses emerge (< 200 CD4+ cells/mm3).
Common diseases of HIV-positive adults
- CORRECT ANSWER As CD4+ count decreases, risks of reactivation of past
infections (e.g., TB, HSV, shingles), dissemination of bacterial infections and fungal
infections (e.g., coccidioidomycosis), and non-Hodgkin lymphomas increases.
Common disease in HIV positive adult with < 500 cells/mm3 - CORRECT ANSWER -
Candida albicans: oral thrush (scrapable white plaque, pseudohyphae on microscopy)
-EBV: oral hairy leukoplakia (unscrapable white plaque)
,-Bartonella henselae: bacillary angiomatosis (biopsy with neutrophilic inflammation)
-HHV-8: Kaposi sarcoma (biopsy with lymphocytic inflammation)
-Cryptosporidium spp.: chronic, watery diarrhea (acid-fast oocyst in stool)
-HPV: SCC, commonly of anus (for gay men) or cervix (women)
Common disease in HIV positive adult with < 200 cells/mm3 - CORRECT ANSWER HIV
dementia: dementia
JC virus (reactivation): progressive multifocal leukoencephalopathy (nonenhancing
areas of demyelination on MRI)
Pneumocystis jirovecii: Pneumocystis pneumonia ("ground glass" opacities on CXR)
Common disease in HIV positive adult with < 100 cells/mm3 - CORRECT ANSWER -
Aspergillus fumigatus: hemoptysis, pleuritic pain (cavitation or infiltrates on chest
imaging)
-Cryptococcus neoformans: meningitis (thickly encapsulated yeast on India ink stain or
capsular antigen+)
-Candida albicans: esophagitis (white plaques on endoscopy, yeast and pseudohyphae
on biopsy)
-CMV: retinitis, esophagitis, colitis, pneumonitis, encephalitis (linear ulcers on
endoscopy, cotton-wool spots on fundoscopy; biopsy reveals cells with intranuclear (owl
eye) inclusion bodies
-EBV: B-cell lymphoma (e.g. non-Hodgkin lymphoma, CNS lymphoma) (CNS
lymphoma—ring enhancing, may be solitary (vs. Toxoplasma))
-Histoplasma capsulatum: fever, weight loss, fatigue, cough, dyspnea, nausea,
vomiting, diarrhea (oval yeast cells within macrophages)
-Mycobacterium avium-intracellulare, Mycobacterium avium complex: nonspecific
systemic symptoms (fever, night sweats, weight loss) or focal lymphadenitis
-Toxoplasma gondii: brain abscesses (multiple ring enhancing lesions on MRI)
Prions - CORRECT ANSWER -Prion diseases are caused by the conversion of a
normal (predominantly α-helical) protein termed prion protein (PrPc) to a β-pleated form
(PrPsc), which is transmissible via CNS-related tissue (iatrogenic CJD) or food
contaminated by BSE-infected animal products (variant CJD).
, PrPsc resists protease degradation and facilitates the conversion of still more PrPc to
PrPsc.
Resistant to standard sterilizing procedures, including standard autoclaving.
Accumulation of PrPsc results in spongiform encephalopathy (see picture) and
dementia, ataxia, and death.
Prion diseases - CORRECT ANSWER -Creutzfeldt-Jakob disease—rapidly progressive
dementia, typically sporadic (some familial forms).
-Bovine spongiform encephalopathy (BSE)—also known as "mad cow disease."
-Kuru—acquired prion disease noted in tribal populations practicing human
cannibalismViral structure - general features schematic - CORRECT ANSWER
Viral recombination - CORRECT ANSWER Exchange of genes between 2
chromosomes by crossing over within regions of significant base sequence homology.
Viral reassortment - CORRECT ANSWER When viruses with segmented genomes
(e.g., influenza virus) exchange genetic material. For example, the 2009 novel H1N1
influenza A pandemic emerged via complex viral reassortment of genes from human,
swine, and avian viruses.
Has potential to cause antigenic shift.
Viral complementation - CORRECT ANSWER -When 1 of 2 viruses that infect the cell
has a mutation that results in a nonfunctional protein. The nonmutated virus
"complements" the mutated one by making a functional protein that serves both viruses.
-For example, hepatitis D virus requires the presence of replicating hepatitis B virus to
supply HBsAg, the envelope protein for HDV.
Viral phenotypic mixing - CORRECT ANSWER Occurs with simultaneous infection of a
cell with 2 viruses. Genome of virus A can be partially or completely coated (forming
pseudovirion) with the surface proteins of virus B. Type B protein coat determines the
tropism (infectivity) of the hybrid virus. However, the progeny from this infection have a
type A coat that is encoded by its type A genetic material.
Live attenuated viral vaccines vs. killed/inactive vaccines - CORRECT ANSWER Induce
humoral and cell-mediated immunity but have reverted to virulence on rare occasions.
Killed/inactivated vaccines induce only humoral immunity but are stable.
No booster needed for live attenuated vaccines.
Dangerous to give live vaccines to
2024/2025
HIV diagnosis
- CORRECT ANSWER -Presumptive diagnosis made with ELISA (sensitive, high false+
rate and low threshold, rule out test); ⊕ results are then confirmed with Western blot
assay (specific, low false+ rate and high threshold, rule in test).
Viral load tests determine the amount of viral RNA in the plasma. High viral load
associated with poor prognosis. Also use viral load to monitor effect of drug therapy.
AIDS diagnosis ≤ 200 CD4+ cells/mm3 (normal: 500-1500 cells/mm3). HIV-positive with
AIDS-defining condition (e.g., Pneumocystis pneumonia) or CD4+ percentage < 14%.
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).
Time course of untreated HIV infection
- CORRECT ANSWER -Four stages of untreated infection:
1. Flu-like (acute)
2. Feeling fine (latent)
3. Falling count
4. Final crisis
-During latent phase, virus replicates in lymph
nodes.
-Red line = CD4+ T cell count (cells/mm3); blue line = HIV RNA copies/mL plasma.
-Blue boxes on vertical CD4+ count axis indicate moderate immunocompromise (< 400
CD4+ cells/mm3) and when AIDS-defining illnesses emerge (< 200 CD4+ cells/mm3).
Common diseases of HIV-positive adults
- CORRECT ANSWER As CD4+ count decreases, risks of reactivation of past
infections (e.g., TB, HSV, shingles), dissemination of bacterial infections and fungal
infections (e.g., coccidioidomycosis), and non-Hodgkin lymphomas increases.
Common disease in HIV positive adult with < 500 cells/mm3 - CORRECT ANSWER -
Candida albicans: oral thrush (scrapable white plaque, pseudohyphae on microscopy)
-EBV: oral hairy leukoplakia (unscrapable white plaque)
,-Bartonella henselae: bacillary angiomatosis (biopsy with neutrophilic inflammation)
-HHV-8: Kaposi sarcoma (biopsy with lymphocytic inflammation)
-Cryptosporidium spp.: chronic, watery diarrhea (acid-fast oocyst in stool)
-HPV: SCC, commonly of anus (for gay men) or cervix (women)
Common disease in HIV positive adult with < 200 cells/mm3 - CORRECT ANSWER HIV
dementia: dementia
JC virus (reactivation): progressive multifocal leukoencephalopathy (nonenhancing
areas of demyelination on MRI)
Pneumocystis jirovecii: Pneumocystis pneumonia ("ground glass" opacities on CXR)
Common disease in HIV positive adult with < 100 cells/mm3 - CORRECT ANSWER -
Aspergillus fumigatus: hemoptysis, pleuritic pain (cavitation or infiltrates on chest
imaging)
-Cryptococcus neoformans: meningitis (thickly encapsulated yeast on India ink stain or
capsular antigen+)
-Candida albicans: esophagitis (white plaques on endoscopy, yeast and pseudohyphae
on biopsy)
-CMV: retinitis, esophagitis, colitis, pneumonitis, encephalitis (linear ulcers on
endoscopy, cotton-wool spots on fundoscopy; biopsy reveals cells with intranuclear (owl
eye) inclusion bodies
-EBV: B-cell lymphoma (e.g. non-Hodgkin lymphoma, CNS lymphoma) (CNS
lymphoma—ring enhancing, may be solitary (vs. Toxoplasma))
-Histoplasma capsulatum: fever, weight loss, fatigue, cough, dyspnea, nausea,
vomiting, diarrhea (oval yeast cells within macrophages)
-Mycobacterium avium-intracellulare, Mycobacterium avium complex: nonspecific
systemic symptoms (fever, night sweats, weight loss) or focal lymphadenitis
-Toxoplasma gondii: brain abscesses (multiple ring enhancing lesions on MRI)
Prions - CORRECT ANSWER -Prion diseases are caused by the conversion of a
normal (predominantly α-helical) protein termed prion protein (PrPc) to a β-pleated form
(PrPsc), which is transmissible via CNS-related tissue (iatrogenic CJD) or food
contaminated by BSE-infected animal products (variant CJD).
, PrPsc resists protease degradation and facilitates the conversion of still more PrPc to
PrPsc.
Resistant to standard sterilizing procedures, including standard autoclaving.
Accumulation of PrPsc results in spongiform encephalopathy (see picture) and
dementia, ataxia, and death.
Prion diseases - CORRECT ANSWER -Creutzfeldt-Jakob disease—rapidly progressive
dementia, typically sporadic (some familial forms).
-Bovine spongiform encephalopathy (BSE)—also known as "mad cow disease."
-Kuru—acquired prion disease noted in tribal populations practicing human
cannibalismViral structure - general features schematic - CORRECT ANSWER
Viral recombination - CORRECT ANSWER Exchange of genes between 2
chromosomes by crossing over within regions of significant base sequence homology.
Viral reassortment - CORRECT ANSWER When viruses with segmented genomes
(e.g., influenza virus) exchange genetic material. For example, the 2009 novel H1N1
influenza A pandemic emerged via complex viral reassortment of genes from human,
swine, and avian viruses.
Has potential to cause antigenic shift.
Viral complementation - CORRECT ANSWER -When 1 of 2 viruses that infect the cell
has a mutation that results in a nonfunctional protein. The nonmutated virus
"complements" the mutated one by making a functional protein that serves both viruses.
-For example, hepatitis D virus requires the presence of replicating hepatitis B virus to
supply HBsAg, the envelope protein for HDV.
Viral phenotypic mixing - CORRECT ANSWER Occurs with simultaneous infection of a
cell with 2 viruses. Genome of virus A can be partially or completely coated (forming
pseudovirion) with the surface proteins of virus B. Type B protein coat determines the
tropism (infectivity) of the hybrid virus. However, the progeny from this infection have a
type A coat that is encoded by its type A genetic material.
Live attenuated viral vaccines vs. killed/inactive vaccines - CORRECT ANSWER Induce
humoral and cell-mediated immunity but have reverted to virulence on rare occasions.
Killed/inactivated vaccines induce only humoral immunity but are stable.
No booster needed for live attenuated vaccines.
Dangerous to give live vaccines to
