KMU Past Paper Practice

Question:

A researcher examines an HIV virion and identifies an envelope glycoprotein responsible for binding to the CD4 molecule on a susceptible T lymphocyte. Which viral component performs this function?

Correct Answer: gp120

Explanation: gp120 binds CD4 and an appropriate co-receptor during HIV attachment. gp41 subsequently facilitates fusion of the viral envelope with the host-cell membrane.

Question:

An HIV virion has attached to a CD4-positive lymphocyte through its surface glycoprotein and co-receptor. The next step requires fusion of the viral envelope with the host-cell membrane. Which viral component is most directly involved?

Correct Answer: gp41

Explanation: gp120 mediates attachment, whereas gp41 promotes membrane fusion and viral entry. This distinction is a commonly tested structural concept.

Question:

HIV DNA has been successfully inserted into the chromosome of an infected CD4-positive cell. Which viral enzyme was directly responsible for this step?

Correct Answer: Integrase

Explanation: Integrase inserts newly synthesized HIV DNA into host-cell DNA, creating the proviral stage that allows persistent infection.

Question:

A patient with untreated HIV initially had few symptoms for several years but later developed recurrent severe infections. Which sequence best explains this clinical progression?

Correct Answer: Persistent viral replication → immune-cell damage → progressive immunodeficiency

Explanation: Continuing HIV replication progressively damages CD4-mediated immunity. Clinical opportunistic disease becomes more likely as immune competence declines.

Question:

Two investigations are reviewed in a patient with HIV. One reflects the extent of immune-system impairment, while the other reflects active viral replication. Which pairing is correct?

Correct Answer: CD4 count for immune status; HIV RNA for viral replication

Explanation: CD4 T-cell assessment indicates the degree of immune impairment, while plasma HIV RNA reflects the burden of actively replicating virus.

Question:

A patient recovers completely from a primary herpesvirus infection. Years later, impaired immunity is followed by renewed viral replication and clinical disease. Which sequence best represents the natural behavior of this viral family?

Correct Answer: Primary replication → latency → reactivation

Explanation: Herpesviruses characteristically establish lifelong latency following primary infection and can resume active replication during later reactivation.

Question:

A patient with recurrent painful genital vesicles undergoes laboratory evaluation because the clinical appearance is uncertain. The physician requires a rapid test that can specifically identify viral genetic material in the lesion. Which approach is most appropriate?

Correct Answer: Viral nucleic-acid detection

Explanation: Molecular detection of viral nucleic acid provides specific evidence of herpesvirus in an appropriate lesion specimen and is useful when rapid confirmation is needed.

Question:

A patient with recurrent herpes labialis asks whether acyclovir will permanently remove the virus and prevent any future episode. Which explanation best describes the limitation of therapy?

Correct Answer: It inhibits active replication but does not eradicate latent virus

Explanation: Acyclovir suppresses DNA synthesis during active herpesvirus replication. Latent viral genomes persist, so future reactivation remains possible.

Question:

An older patient with impaired renal function is prescribed acyclovir for a severe herpesvirus infection. Without appropriate adjustment, the patient is at increased risk of drug accumulation. Which feature best explains this concern?

Correct Answer: The drug depends mainly on renal elimination

Explanation: Acyclovir is predominantly eliminated by the kidneys. Reduced renal function therefore increases exposure and the risk of renal and neurological toxicity.

Question:

A patient with a severe HSV infection requires systemic antiviral therapy. The treating physician selects acyclovir rather than assuming that it can only be used locally. Which statement about its administration is correct?

Correct Answer: It can be given orally, intravenously or topically

Explanation: Acyclovir is available by oral, intravenous and topical routes. The route is selected according to the site and severity of infection.

Question:

Acyclovir enters a herpesvirus-infected cell and undergoes phosphorylation to its active triphosphate form. Which sequence best describes the resulting antiviral effect?

Correct Answer: DNA polymerase inhibition → impaired chain elongation → reduced replication

Explanation: Activated acyclovir preferentially inhibits herpesvirus DNA polymerase and terminates DNA-chain elongation, thereby suppressing active viral replication.

Question:

A patient with HIV begins a drug that interferes with the interaction between the virus and a host-cell co-receptor. Viral replication falls because the earliest stage of infection is interrupted. Which antiretroviral class is being used?

Correct Answer: Entry inhibitors

Explanation: Entry inhibitors act before intracellular replication by interfering with attachment, co-receptor interaction or membrane fusion required for HIV entry.

Question:

Two anti-HIV drugs both inhibit reverse transcriptase. Drug X acts as an abnormal nucleoside substrate, whereas Drug Y binds directly to a separate site on the enzyme. Which classification correctly identifies Drug X and Drug Y?

Correct Answer: NRTI and NNRTI

Explanation: NRTIs act as abnormal nucleoside/nucleotide substrates during viral DNA synthesis, whereas NNRTIs bind directly to reverse transcriptase at a different site.

Question:

An HIV-infected cell releases newly assembled viral particles. A prescribed drug prevents cleavage of large viral precursor proteins, so the released particles fail to mature normally. At which stage is the drug acting?

Correct Answer: Viral maturation

Explanation: HIV protease cleaves viral polyproteins during maturation. Protease inhibition therefore produces immature particles with markedly reduced infectivity.

Question:

A patient taking zidovudine develops weakness after prolonged therapy. In addition to hematological toxicity, which adverse effect is consistent with the recognized toxicity profile of this drug?

Correct Answer: Myopathy

Explanation: Zidovudine can cause myopathy in addition to its important bone-marrow toxicity. Renal stone formation is more characteristically associated with indinavir.

Question:

An HIV-positive patient is taking combination antiretroviral therapy. Viral replication becomes strongly suppressed, but the clinician explains that treatment cannot be considered eradication of infection. Which feature of HIV best accounts for this limitation?

Correct Answer: Viral DNA can persist after integration into host DNA

Explanation: Integrated proviral DNA can persist within host cells despite suppression of active replication, explaining why effective antiretroviral therapy does not simply eradicate HIV.

Question:

Several children in the same household develop chickenpox after one child becomes ill. Which combination of epidemiological factors best explains efficient spread in this setting?

Correct Answer: Human reservoir with susceptible close contacts

Explanation: Humans are the reservoir for varicella-zoster virus, and close contact among susceptible individuals facilitates efficient chickenpox transmission.

Question:

During an outbreak investigation, a community medicine student compares chickenpox cases among children and adults. Which statement best describes the expected epidemiological distribution?

Correct Answer: Disease commonly affects susceptible children but can affect nonimmune adults

Explanation: Chickenpox occurs worldwide and commonly affects susceptible children, although adults who lack immunity remain susceptible to primary VZV infection.

Question:

A competent adult is offered HIV testing during clinical evaluation. The patient asks why the test is being performed and what a positive result could mean before deciding whether to proceed. Which medico-legal principle is most directly involved?

Correct Answer: Informed consent

Explanation: Informed consent requires that a competent patient understand the nature, purpose and relevant implications of testing before making a decision.

Question:

A patient known to have HIV requires treatment for an unrelated illness. A member of the healthcare team suggests refusing routine care solely because of the patient’s HIV status. Which professional principle is most appropriate?

Correct Answer: Provide appropriate care using standard precautions without discrimination

Explanation: HIV status alone is not a justification for denying appropriate medical care. Standard precautions protect healthcare workers while respecting patient dignity and non-discrimination.