Laboratory Diagnosis of HIV (Exam 3-5b)

Question 1

What is the structural gene called gag coding for?

Answer 1

core structural proteins - nucleocapsid and matrix

Question 2

What is the structural gene env coding for?

Answer 2

glycoproteins that make up the envelope

Question 3

What is the structural gene pol coding for?

Answer 3

enzymes for replication - in the core

Question 4

What is gp41 referring to?

Answer 4

The transmembrane protein

Question 5

What is gp120 referring to?

Answer 5

The docking protein

Question 6

What is p24 referring to?

Answer 6

The capsid

Question 7

What is p17 referring to?

Answer 7

The matrix protein

Question 8

What coreceptors can HIV use to infect cells?

Answer 8

CCR5 or CXCR4

Question 9

Which patients remain healthy for longer, patients with HIV that prefers R5 or X4?

Answer 9

Patients with HIV that prefers R5

Question 10

What is the preferred receptor for M-trophic (R5) strains?

Answer 10

CCR5

Question 11

What is the preferred receptor for T-trophic (X4) strains?

Answer 11

CXCR4

Question 12

When are abs detectable in HIV patients?

Answer 12

3-12 weeks after primary infection

Question 13

Which type of immune cell does HIV attack directly?

Answer 13

T helper cells

Question 14

What are two other cellular/immunological effects of HIV?

Answer 14

Defective ag presentation (down-regulation of MHC I expression), and decrease in NK activity

Question 15

What happens to CD4 T cells during the primary infection?

Answer 15

They decrease

Question 16

What happens to CD4 T cells during the clinical latency phase?

Answer 16

They increase

Question 17

What happens to CD4 T cells during AIDS?

Answer 17

They decrease

Question 18

What are the characteristics of long-term nonprogressors (LTNP)?

Answer 18

Normal or mildly depressed CD4 T cells,
low viral loads,
asymptomatic for >10 years in absence of ART

Question 19

What kind of test is done to look for p24?

Answer 19

ELISA (antibody+antigen)

Question 20

What generation of testing is described below?

EIAs used antigen consisting of viral lysates to detect IgG antibodies. The window period = 56 days

Answer 20

First-generation

Question 21

What generation of testing is described below?
Tests relied on recombination HIV proteins or synthetic peptides to detect HIV-1/2 IgG antibodies. Window period = 42 days

Answer 21

Second-generation

Question 22

What generation of testing is described below?
Combination tests that can detect HIV-1 Groups M and O, as well as HIV-2. They also use recombinant/synthetic peptides to detect IgG antibodies, as well as IgM produced by B cells. Window period = 22 days

Answer 22

Third-generation

Question 23

What generation of testing is described below?

Could detect HIV-1, Group M, and HIV-2 IgG and IgM, as well as the HIV-1 p24 antigen. Window period = 15 to 17 days

Answer 23

Fourth-generation

Question 24

What generation of testing is described below?
A multiplexed screening that detecs and differentiates all three HIV analyte markers: HIV-1 Abs, HIV-2 Abs, and the HIV-1 p24 antigen

Answer 24

Fifth-generation

Question 25

What indicateds a positive Western Blot test for HIV?

Answer 25

Bands for at least 2 of the 3 proteins: p24, gp41, and gp120/gp160

Question 26

What are some of the limitations of Western Blot?

Answer 26

May misidentify HIV-2, less sensitive than newer screenings, frequently indeterminate, performed by ref labs (slow), labor intensive, technically difficult, and expensive

Question 27

When does the p24 antigen become undetectable?

Answer 27

After host anti-p24 antibodies develop and viral load drops

Question 28

What is the common test for DH to use to detect HIV?

Answer 28

Alere HIV Ab/Ag combo (rapid EIA)

Question 29

In what order do HIV markers appear in an infetced person?

Answer 29

HIV RNA, p24 antigen, and then HIV-1/2 antibodies

Question 30

Early infection, before seroconversion can lead to a false negative test. T or F?

Answer 30

True

Question 31

Autoreactive antibodies can lead to a false positive test. T or F?

Answer 31

True

Question 32

When is serological testing used for children to confirm diagnosis?

Answer 32

12 to 18 months of age

Question 33

What is the preferring method for diagnosis of children?

Answer 33

Qualitative HIV-1 DNA PCR (detects proviral DNA)

Question 34

Causative agent of syphilis?

Answer 34

gram-neg helically coiled spirochete bacteria - Treponema pallidum

Question 35

Clinical manifestations of syphilis?

Answer 35

Localized skin infection, moves to organs, has latent stage, and can cause cardiac and neurological involvement

Question 36

Transmission of syphilis?

Answer 36

Sexual, congenital (vertical), and parenteral (rarely)

Question 37

Causative agent of lyme disease?

Answer 37

Borrelia burdorferi

Question 38

Causative agent of relapsing fever?

Answer 38

Borrelia spp.