Question 1

Which of the following is considered the best indicator of immune function in HIV-infected individuals?

Accepted Answer

CD4 T-cell count is considered the best indicator of immune function in HIV-infected individuals because it reflects the number of helper T cells that have been destroyed by the virus, and can predict the risk of opportunistic infections and disease progression. HIV-1 viral load, presence of HIV-2 antibodies, and absolute lymphocyte count are also important parameters to monitor, but CD4 T-cell count provides the most reliable and clinically relevant information.

Question 2

CD4 T cells play a central role in the immune response system by regulating the activities of B and T lymphocytes.

Accepted Answer

CD4 T cells are also known as helper T cells, they help in activating and coordinating the immune response by releasing cytokines and other signals. They can also help in activating B cells, which produce antibodies, and cytotoxic T cells, which destroy infected cells.

Question 3

Which antigen can be routinely detected in the blood of a person who has recently been infected with HIV?

Accepted Answer

p24 is the antigen that can be routinely detected in the blood of a person who has recently been infected with HIV. This antigen is a part of the HIV virus that is released into the bloodstream during the early stages of infection. Testing for the presence of p24 antigen in the blood can help diagnose HIV infection even before antibodies to the virus are produced.

Question 4

The RT-PCR is a highly sensitive method that involves:

Accepted Answer

The RT-PCR method involves amplifying a complementary DNA sequence to a portion of the HIV RNA, making choice C the correct option. The other options (direct amplification of HIV RNA, amplification of a label attached to HIV RNA, and DNA sequencing of a portion of HIV RNA) do not accurately describe the RT-PCR method.

Question 5

Match the HIV protein product to its function.
-gp41

Accepted Answer

gp41 is a transmembrane protein that anchors the HIV envelope to the viral core.

Answer: C
 gp41 is also an envelope protein that binds to the CD4 receptor on the surface of T cells, facilitating viral entry.

Therefore, the best choices for gp41 are B and C.

Question 6

In the Western blot test for HIV antibody,a positive test result is indicated by the bands p24 and p55.

Accepted Answer

A positive Western blot test for HIV antibody is indicated by the presence of bands against several different viral proteins, including p24, gp41, and gp120/160. The presence of the p55 band alone does not confirm a positive result.

Question 7

Of the designated subtypes of HIV,which is the most common in the United States?

Accepted Answer

Subtype B is the most common strain of HIV in the United States, accounting for approximately 80-85% of HIV diagnoses in the country. Subtype C is the most common globally, but is more prevalent in parts of Africa and Asia. Subtypes A and K are relatively rare in the United States.

Question 8

Match the HIV protein product to its function.
-gp120

Accepted Answer

gp120 is an envelope protein that binds to CD4 on T cells.

Answer: B 
 gp41 is a transmembrane protein.

Answer: A 
 p66 is a component of the reverse transcriptase enzyme.

Answer: D 
 p24 is the core coat for nucleic acids.

Question 9

Match the HIV protein product to its function.
-p24

Accepted Answer

p24 is the HIV protein that forms the core coat for viral nucleic acids.

Note: A is incorrect because reverse transcriptase is composed of multiple proteins, including p51, p66, and p31. B and C are incorrect because they refer to transmembrane protein gp41 and envelope protein gp120, respectively.

Question 10

Which HIV group is responsible for a majority of the HIV infections worldwide?

Accepted Answer

Group M is responsible for a majority of HIV infections worldwide, accounting for more than 90% of all infections. Group M is further divided into subtypes, with subtype B being the most common in North America and Western Europe. Group O and Group N are relatively rare, while Group P has only been identified in a few individuals.

Question 11

The Southern blot test is the specific confirmatory test for HIV infection.

Accepted Answer

The Southern blot test is not the specific confirmatory test for HIV infection. The HIV specific confirmatory test is the Western blot test or more commonly used the HIV-1/2 antibody differentiation immunoassay.

Question 12

Histoplasmosis (disseminated or extrapulmonary)is an opportunistic infection of stage 3 HIV infection.

Accepted Answer

Histoplasmosis is commonly seen in individuals with a weakened immune system, including those with stage 3 HIV infection. Disseminated or extrapulmonary histoplasmosis can occur when the fungus spreads beyond the lungs to other parts of the body, such as the liver, spleen, or bone marrow.

Question 13

The most commonly used HIV drug-resistance assays are based on:

Accepted Answer

The most commonly used HIV drug-resistance assays are based on detecting genetic mutations in HIV. This is done through testing for specific mutations that are known to confer resistance to antiretroviral drugs. Culture of HIV in the presence of antiretroviral drugs (A) can also yield information on drug resistance, but is less commonly used. HIV antibodies do not provide information on drug resistance (C), and typing for the HLA-B27 allele (D) is not related to HIV drug resistance.

Question 14

Which of the following genes is responsible for the coding of reverse transcriptase?

Accepted Answer

The gene responsible for coding reverse transcriptase is pol, located in the pol gene cluster of retroviruses. The env gene codes for envelope glycoproteins, the gag gene codes for structural proteins, and the tat gene codes for a transcriptional activator protein.

Question 15

Match the HIV protein product to its function.
-p66

Accepted Answer

p66 is a component of the reverse transcriptase enzyme, which is responsible for converting the virus's RNA genome into DNA.

Answer: D
 The core coat for nucleic acids is made up of several HIV proteins, including p24, p17, and p7, but not p66.

Answer: B and C
 Neither p66 nor p24 is a transmembrane protein, and neither plays a direct role in binding to CD4 on T cells. These functions are carried out by the envelope protein gp120 (choice C) and the transmembrane protein gp41 (choice B).

Question 16

Which of the following peripheral blood measurements is used to determine the stage of HIV infection?

Accepted Answer

The number of CD4 T cells is used to monitor the progression of HIV infection and determine the stage of the disease. As HIV infects and destroys CD4 T cells, the number of these cells decreases and serves as a marker for the progression of the disease. The stage of HIV infection is determined by the CD4 T cell count and the presence of opportunistic infections. The other options - the number of CD8 T cells, the number of HIV RNA copies, and the HIV antibody titer - may also be important in monitoring HIV infection, but they are not used to determine the stage of the disease.

Question 17

When HIV replicates,the DNA in the viral genome is transcribed into RNA.

Accepted Answer

HIV replication involves reverse transcription, where the RNA in the viral genome is transcribed into DNA, which is then integrated into the host cell's genome.

Quiz 24: Laboratory Diagnosis of HIV Infection