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FA - Microbiology > Micro - Virology (HIV) > Flashcards

Micro - Virology (HIV) Flashcards

Pg. 164-166 Sections include: HIV HIV diagnosis Time course of HIV infection Common diseases of HIV-positive adults

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1
Q

Describe the HIV genome. Include ploidy, type(s) and number of molecules.

A

Diploid genome (2 molecules of RNA)

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2
Q

What are the structural genes of HIV?

A

(1) env (2) gag (3) pol

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3
Q

What product(s) does the HIV structural gene env encode?

A

Env codes for gp160, which is cleaved to form envelope proteins gp120 and gp41

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4
Q

In what HIV structural gene is gp120 coded? What is the role of gp120?

A

Env (which directly encodes gp160, which is later cleaved to gp120 and gp41); Docking glycoprotein for Attachment to host CD4+ T cell

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5
Q

In what HIV structural gene is gp41 coded? What is the role of gp41?

A

Env (which directly encodes gp160, which is later cleaved to gp120 and gp41); Transmembrane glycoprotein for Fusion and entry

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6
Q

What product(s) does the HIV structural gene gag encode? What is the role of this/these product(s)?

A

p24; Capsid protein

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7
Q

In what HIV structural gene is p24 coded? What is the role of p24?

A

gag; Capsid protein

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8
Q

With what product(s) is the HIV structural gene pol associated?

A

(1) Reverse transcriptase (2) Aspartate protease (3) Integrase

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9
Q

What role does reverse transcriptase play?

A

Synthesizes dsDNA from RNA (which permits the dsDNA to later be integrated into the host genome)

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10
Q

What is the fate of the dsDNA synthesized from RNA by reverse transcriptase?

A

Integrated into host genome

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11
Q

What are the envelope proteins of HIV? How are they acquired?

A

gp120 & gp41; Acquired through budding from host cell plasma membrane

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12
Q

Where does HIV virus bind in its host? Clarify binding in early versus late infection.

A

Virus binds CCR5 (early) or CXCR4 (late) co-receptor and CD4 on T-cells; Also bind CCR5 and CD4 on macrophages

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13
Q

What does homozygous CCR5 mutation cause? What does heterozygous CCR5 mutation cause?

A

Immunity; Slower course

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14
Q

How is HIV diagnosed? Compare and contrast the tests used.

A

Presumptive diagnosis made with ELISA (sensitive, high false-positive rate and low threshold, RULE OUT test); Positive results are then confirmed with Western blot assay (specific, high false-negative rate and high threshold, RULE IN test)

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15
Q

What do HIV PCR/viral load tests determine? What is the clinical relevance of this measure?

A

Amount of viral RNA in the plasma; (1) HIgh viral load associated with poor prognosis (2) Viral load used to monitor effect of drug therapy

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16
Q

What is a normal CD4+ cell count? What CD4+ cell count defines an AIDS diagnosis?

A

500-1500 cells/mm^3; Less than or equal to 200 cells/mm^3

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17
Q

What are ways to define an AIDS diagnosis?

A

(1) Less than or equal to 200 CD4+ cells/mm^3 (normal: 500-1500) (2) HIV positive with AIDS-defining condtion (e.g., Pneumocystis pneumonia, or PCP) (3) HIV positive with CD4/CD8 ratio < 1.5

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18
Q

What do the Elisa/Western Blot HIV tests detect? What kind of false readings are seen with these tests, and in what circumstances?

A

Antibodies to viral proteins; Often are fasely negative in the first 1-2 months of HIV infection & falsely positive initially in babies born to infected mothers (anti-gp120 crosses placenta)

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19
Q

What are the four stages of untreated HIV infection? What is a good way to remember this?

A

Four stages of infection: (1) Flu-like (acute) (2) Feeling fine (latent) (3) Falling count (4) Final crisis; All F’s

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20
Q

What significant event happens during the latent phase of HIV, and where?

A

Virus replicates in the lymph nodes

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21
Q

Draw the structure of HIV and its contents.

A

See illustration on pg. 164 in First Aid

22
Q

What initially occurs upon HIV infection?

A

Acute phase = (1) Acute HIV syndrome (2) Wide dissemination of virus (3) Seeding of lymphoid organs

23
Q

What CD4+ T cell count is considered to be immunocompromised? Again, what is the AIDS-defining CD4+ T cell count?

A

Less than 400 CD4+ cells/mm^3; Less than 200 CD4+ cells/mm^3

24
Q

Draw the time course of HIV infection as a dual graph of CD4+ T cells/mm^3 and HIV RNA copies/mL as separate y axes & months to years on the x axis. Label the following based on the time at which they occur: Primary infection, Acute HIV Syndrome, Wide dissemination of virus, Seeding of lymphoid organs, Clinical latency, Constitutional Symptoms, Opportunistic disease, Death.

A

See pg. 165 in First Aid

25
Q

As CD4 count decreases in HIV-positive adults, what risks increase?

A

(1) Reactivation of past infections (e.g., TB, HSV, shingles) (2) Dissemination of bacterial and/or fungal infections (e.g., coccidioidomycosis) (3) Non-Hodgkin’s lymphomas

26
Q

What are common systemic clinical presentations in HIV-positive adults? What is the causative pathogen? What are associated findings/labs?

A

Low grade fevers, cough, hepatosplenomegaly, tongue ulcer; Histoplasma capsulatum (causes only pulmonary symptoms in immunocompetent hosts); Oval yeast cells within macrophages, CD4 < 100 cells/mm^3

27
Q

What effect does Histoplasma capsulatum have on HIV-positive adults versus immunocompetent hosts?

A

HIV-POSITIVE ADULTS - Low grade fevers, cough, splenomegaly, tongue ulcer; IMMUNOCOMPETENT - Only pulmonary symptoms

28
Q

Again, what effect does Histoplasma capsulatum have on HIV-positive adults? What are its associated findings/labs?

A

Systemic - Low grade fever, cough, splenomegaly, tongue ulcer; Oval yeast cells within macrophages, CD4 < 100 cells/mm^3

29
Q

What are 3 common dermatologic clinical presentations in HIV-positive adults? What pathogen causes each?

A

(1) Fluffy white cottage-cheese lesions - C. albicans (2) Hairy leukoplakia - EBV (3) Superficial vascular proliferation - Bartonella henselae

30
Q

What pathogen causes fluffly white cottage-cheese lesions in HIV-positive adults? What are the associated findings/labs?

A

C. albicans (causes thrush and esophagitis); Pseudohyphae, commonly oral if CD4 < 400 cells/mm^3, esophageal if CD4 < 100 cells/mm^3

31
Q

What pathogen causes Superficial vascular proliferation in HIV-positive adults? What are the associated findings/labs?

A

Bartonella henselae (causes bacillary angiomatosis); Biopsy reveals neutrophil inflammation

32
Q

In general, what do C. albicans, EBV, and Bartonella henselae both cause in HIV-positive adults? What disease/condition should you associate with each pathogen?

A

All cause dermatologic clinical presentation; C. albicans causes oral thrush and esophagitis, EBV causes hairy leukoplakia, and Bartonella henselae causes bacillary angiomatosis

33
Q

What is a common gastrointestinal clinical presentation in HIV-positive adults? What pathogen causes it? What are the associated findings/labs?

A

Chronic, watery diarrhea; Cryptosporidium spp.; Acid-fast cysts seen in stool especially when CD4 < 200 cells/mm^3

34
Q

What are the common neurology clinical presentations in HIV-positive adults? What is the pathogen that causes each?

A

(1) Encephalopathy - JC virus reactivation (cause of PML) (2) Abscess - Toxoplasma gondii (3) Meningitis - Crytococcus neoformans (4) Retinitis - CMV (5) Dementia - Directly associated with HIV

35
Q

What pathogen/process causes encephalopathy in HIV-positive adults? What findings/lab may you expect to see in this case?

A

JC virus reactivation (cause of PML); Due to reactivation of a latent virus, results in demyelination, CD4 < 200 cells/mm^3

36
Q

What pathogen causes abscesses in HIV-positive adults? What findings/lab may you expect to see in this case?

A

Toxoplasma gondii; Many ring-enhancing lesions on imaging, CD4 < 100 cells/mm^3

37
Q

What pathogen causes meningitis in HIV-positive adults? What findings/lab may you expect to see in this case?

A

Crytococcus neoformans; Indian ink stain reveals yeast with narrow-based budding and large capsule, CD4 < 50 cells/mm^3

38
Q

What pathogen causes retinitis in HIV-positive adults? What findings/lab may you expect to see in this case?

A

CMV; Cotton-wool spots on funduscopic exam and may also occur with esophagitis, CD4 < 50 cells/mm^3

39
Q

What pathogen causes dementia in HIV-positive adults? What is the purpose/relevance of findings/lab in this case?

A

Directly associated with HIV; Must differentiate from other causes

40
Q

What are the common oncologic clinical presentations in HIV-positive adults? What is the pathogen that causes each?

A

(1) Non-Hodgkin’s lymphoma (large cell type) - May be associated with EBV (2) Primary CNS lymphoma - Often associated with eBV (3) Squamous cell carcinoma - HPV (4) Superficial neoplastic proliferation of vasculature - HHV-8 (causes Karposi’s sarcoma, do not confuse with bacillary angiomatosis caused by B. henselae)

41
Q

What pathogen causes superficial neoplastic proliferation of vasculature in HIV-positive adults? What findings/lab may you expect to see in this case?

A

HHV-8 (causes Karposi’s carcoma, do NOT confuse with bacillary angiomatosis caused by B. henselae); Biopsy reveals lymphocyte infiltration

42
Q

What pathogen causes Non-Hodgkin’s lymphoma (large cell type) in HIV-positive adults? What findings/lab may you expect to see in this case?

A

May be associated with EBV; Often on oropharynx (Waldeyer’s ring)

43
Q

What pathogen causes Squamous cell carcinoma in HIV-positive adults? What findings/lab may you expect to see in this case?

A

HPV; Often in anus (men who have sex with men) or cervis (female)

44
Q

What pathogen causes primary CNS lymphoma in HIV-positive adults? What findings/lab may you expect to see in this case, and what is important to do?

A

Often associated with EBV; Focal or multiple, differentiate from toxoplasmosis

45
Q

What are the common respiratory clinical presentations in HIV-positive adults? What is the pathogen that causes each?

A

(1) Interstitial pneumonia - CMV (2) Invasive aspergillosis - Aspergillus fumigatus (3) Pneumocystis Pneumonia - Pneumocystis jirovecii (4) Pneumonia - S. pneumoniae (5) Tuberculosis-like disease - Mycobacterium avium-intracellulare (aka Mycobacterium avium complex or MAC)

46
Q

What pathogen causes interstitial pneumonia in HIV-positive adults? What findings/lab may you expect to see in this case?

A

CMV; Biopsy reveals cells with intranuclear (owl’s eyes) inclusion bodies

47
Q

What pathogen causes invasive aspergillosis in HIV-positive adults? What findings/lab may you expect to see in this case?

A

Aspergillus fumigatus; Pleuritic pain, hemoptysis, infiltrates on imaging

48
Q

What pathogens cause pneumonia in HIV-positive adults? What findings/lab may you expect to see in each case?

A

(1) Pneumocystis jirovecii; Especially with CD4 < 200 cells/mm^3 (2) S. pneumonia: generally with CD4+ < 200 cells/mm^3

49
Q

What pathogen causes tuberculosis-like disease in HIV-positive adults? What findings/lab may you expect to see in this case?

A

Mycobacterium avium-intracellulare (aka Mycobacterium avium complex or MAC); Especially with CD4 < 50 cells/mm^3

50
Q

What pathogen causes Hairy leukoplakia in HIV-positive adults? What is (are) the associated finding/lab(s)?

A

EBV; Often on lateral tongue

FA - Microbiology (43 decks)

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