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Usmle 1 Microbiology > Virus- HIV > Flashcards

Virus- HIV Flashcards

1
Q

Which continent has the highest incidence (and prevalence) of AIDS?

A

Africa

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2
Q

What are the three major routes of HIV transmission?

A
  1. Sexual contact
  2. Vertical (mother to newborn) transmission
  3. Parenteral
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3
Q

What is the most common mode of HIV transmission on a global basis?

A

Heterosexual contact

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4
Q

What type of virus is HIV?

A

Human retrovirus of the lentivirus family

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5
Q

What test is used to screen for HIV infection?

A

Enzyme-linked immunosorbent assay (ELISA) looks for AB to viral proteins; ↑ sensitivity.

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6
Q

What test is used to confirm HIV(+) screening results?

A

Western blot assay (high false negative within 2 months of infection); ↑ specificity

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7
Q

Which enzyme creates dsDNA from RNA for integration into host genome?

A

Reverse transcriptase (RT)

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8
Q

What test is used to monitor the effects of antiretroviral therapy?

A

HIV RT-polymerase chain reaction (RT-PCR) (measures viral load)

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9
Q

What is the strongest measure of disease progression in an HIV(+) patient?

A

CD4+ T-cell count

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10
Q

Name two key glycoproteins on the surface of the HIV viral envelope:

A
  1. gp41 (fusion)

2. gp120 (attachment) proteins; together = gp160

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11
Q

Name two key HIV viral core proteins:

A
  1. p24 (nucleocapsid)

2. p17 (matrix protein)

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12
Q

Name three key HIV retroviral enzymes contained in the core:

A
  1. RT
  2. Integrase
  3. Protease (all encoded by pol gene)
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13
Q

Which viral antigen peaks within 2 months of infection, then rises again years later?

A

p24

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14
Q

What are the two cell surface molecules to which gpl20 must bind?

A
  1. CD4

2. A chemokine receptor (CCR5 or CXCR4)

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15
Q

HIV infects which three cell types?

A
  1. CD4+T cells
  2. Monocytes/macrophages
  3. Dendritic cells
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16
Q

The induction of what cellular transcription factor during an immune response leads to activation of transcription of HIV proviral DNA?

A

Nuclear factor-kappa B (NF-KB)

17
Q

Protease inhibitors of HIV prevent cleavage of the protein product of what viral genes?

A

Gag and pol genes

18
Q

What are the three mechanisms by which HIV-infected CD4+ T cells are lost?

A
  1. HIV cytopathic effect
  2. Apoptosis
  3. HlV-specific cytotoxic T-cell killing
19
Q

What are the three stages of HIV infection?

A
  1. Acute retroviral infection
  2. Chronic phase
  3. AIDS
20
Q

What is the surrogate measure of viral load in an HIV(+) patient?

A

HIV-1 RNA

21
Q

What is the strongest measure of disease progression in AIDS?

A

CD4+ T-cell count

22
Q

Which tissues are the major reservoirs of HIV-infected T cells and macrophages in patients?

A
  1. Lymph nodes
  2. Spleen
  3. Tonsils
23
Q

Which cell type in the brain is infected by HIV?

A

Microglial cells

24
Q

List the major immune abnormalities in AIDS:

A
  1. Decreased number of CD4+ T cells
  2. Decreased T-cell function
  3. Polyclonal activation of B cells
  4. Altered macrophage function
25
Q

What is the clinical picture of direct viral disease from HIV?

A

Constitutional symptoms (weight loss, fever, fatigue, and night sweats) and/or neurologic symptoms (encephalopathy with dementia and aseptic meningitis)

26
Q

How is AIDS defined?

A

CD4+ 200 or AIDS-defining illness, regardless of CD4+ count

27
Q

Name the common AIDS opportunistic organisms or infections/diseases associated with the following:

Four fungal infections

A
  1. Candidiasis (GI tract)
  2. Cryptococcosis (meningitis)
  3. Histoplasmosis (disseminated)
  4. Coccidioidomycosis (disseminated)
28
Q

Name the common AIDS opportunistic organisms or infections/diseases associated with the following:
Five bacterial infections

A
  1. Mycobacterium tuberculosis (lung/disseminated)
  2. Mycobacterium avium-intracellulare (lung)
  3. Nocardia (lung/CNS/disseminated)
  4. Salmonella (disseminated)
  5. Encapsulated organisms
29
Q

Name the common AIDS opportunistic organisms or infections/diseases associated with the following:

Four viral infections

A
  1. HSV
  2. VZV (shingles)
  3. CMV (retinitis or colitis)
  4. JC virus (PML)
30
Q

Name the common AIDS opportunistic organisms or infections/diseases associated with the following:
Three protozoal infections

A
  1. Pneumocystis (lung or disseminated)
  2. Toxoplasm (lung/CNS)
  3. Cryptosporidium (GI)
31
Q

State the typical CD4+ count associated with each:

Opportunistic infections are typically seen, especially Pneumocystis jiroveci pneumonia

A

200 cells/mL

32
Q

State the typical CD4+ count associated with each:

Mycobacterium avium complex (MAC), CMV, and cryptosporidiosis

A

50 cells/mL

33
Q

State the typical CD4+ count associated with each:

Toxoplasmosis

A

100 cells/mL

34
Q

State the typical CD4+ count associated with each:

TB becomes more common

A

400 cells/mL

35
Q

List four common neoplasms in patients with AIDS:

A
  1. Kaposi sarcoma
  2. Non-Hodgkin B-cell lymphoma
  3. CNS lymphoma
  4. Squamous cell carcinoma of the cervix or anus
36
Q

What has been shown to minimize the risk of perinatal HIV transmission?

A

Zidovudine (AZT) given to pregnant women, cesarean delivery, and avoiding breast feeding

Usmle 1 Microbiology (15 decks)

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