Free AIDS and HIV Infection MCQs with Answers

1. HIV causes immune deficiency mainly because it infects and destroys

• A. helper T lymphocytes carrying the CD4 receptor
• B. red blood cells
• C. neutrophils in the bone marrow
• D. platelets in circulating blood

Explanation: The gp120 spike of HIV binds the CD4 receptor, so helper T cells are the main target, and these are the cells that activate both B lymphocytes and cytotoxic T cells. Losing them disables the whole specific immune response, which is why the patient dies of ordinary infections rather than of the virus itself. Red cells have no nucleus and no CD4 receptor, so they cannot be infected.

2. HIV is classified as a retrovirus because it

• A. carries double stranded DNA as its genome
• B. uses reverse transcriptase to make DNA from its RNA genome
• C. replicates inside the nucleolus of the host cell
• D. lacks an envelope around its capsid

Explanation: A retrovirus reverses the usual flow of information: its enzyme reverse transcriptase copies the single stranded RNA genome into DNA, which integrase then inserts into the host chromosome as a provirus. That integrated DNA is why HIV infection is lifelong and can stay latent for years. HIV does have an envelope, and its genome is RNA, not DNA.

3. Which of the following is NOT a route by which HIV is transmitted?

• A. Sharing a contaminated hypodermic needle
• B. From an infected mother to her child during breastfeeding
• C. Shaking hands with or sharing utensils with an infected person
• D. Transfusion of blood from an infected donor

Explanation: HIV is fragile outside the body and spreads only through blood, semen, vaginal secretions and breast milk, so ordinary social contact, sharing food, insect bites and swimming pools carry no risk. Needles, mother to child transmission and unscreened transfusion are all established routes. Knowing this matters because the false belief in casual spread is what drives the social isolation of patients.

4. An HIV positive person is said to have developed AIDS when

• A. antibodies against HIV first appear in the blood
• B. the provirus enters the latent phase
• C. reverse transcriptase is detected in the plasma
• D. the CD4 count falls below about 200 cells per microlitre and opportunistic infections appear

Explanation: AIDS is the late clinical stage, defined by the collapse of helper T cell numbers to roughly a fifth of normal together with opportunistic infections or certain cancers. The appearance of antibodies is seroconversion, which happens within weeks of infection and marks only that the person is HIV positive, often with years of good health still ahead. Latency is the long symptom free phase before AIDS, not AIDS itself.

5. The test most commonly used for the initial screening of a blood sample for HIV infection is

• A. ELISA
• B. Widal test
• C. ABO blood grouping
• D. Routine urine analysis

Explanation: ELISA detects antibodies against HIV and is cheap and sensitive enough for mass screening, with a positive result confirmed afterwards by a more specific test such as Western blot. It can miss a very recent infection, because during the window period of a few weeks the antibodies have not yet been made. The Widal test is for typhoid and has nothing to do with HIV.

6. Which infection is a typical opportunistic infection in a patient with AIDS?

• A. Typhoid fever
• B. Pneumocystis pneumonia
• C. Malaria
• D. Cholera

Explanation: Pneumocystis jirovecii causes pneumonia almost only in people whose cell mediated immunity has failed, so it is one of the defining opportunistic infections of AIDS, along with tuberculosis, candidiasis and Kaposi's sarcoma. Typhoid, malaria and cholera are common infections in Pakistan that attack healthy people just as readily, so their presence says nothing about immune status.

7. Anti retroviral drugs such as zidovudine (AZT) slow the progress of HIV infection by

• A. dissolving the lipid envelope of the virus
• B. stimulating plasma cells to make more antibody
• C. inhibiting the enzyme reverse transcriptase
• D. killing the infected helper T cells before the virus matures

Explanation: AZT is a nucleoside analogue that reverse transcriptase inserts into the growing DNA chain, after which the chain cannot be extended, so no provirus is made. Because the enzyme is viral and has no human counterpart, the drug harms the virus far more than the patient. Such drugs suppress replication and prolong life but do not clear the integrated provirus, so they are not a cure.