HIV basics in human disease: Which of the following statements about Human Immunodeficiency Virus (HIV) and its clinical impact are correct?

Introduction / Context:
HIV is a human retrovirus that targets key cells of the immune system and, if untreated, leads to Acquired Immune Deficiency Syndrome (AIDS). This question checks foundational knowledge about what HIV is, how it acts, and why it undermines host immunity.

Given Data / Assumptions:

• HIV is classified as a retrovirus (RNA genome, reverse transcriptase).
• Helper T cells (CD4+ T lymphocytes) are primary cellular targets.
• AIDS is the clinical syndrome resulting from profound immune depletion.

Concept / Approach:
Retroviruses convert RNA to DNA that integrates into the host genome. HIV preferentially infects CD4+ T cells and some myeloid cells via CD4 and a chemokine co-receptor, progressively depleting CD4+ counts. Loss of CD4+ cells cripples both cell-mediated and humoral immunity, predisposing to opportunistic infections and certain cancers, which define AIDS.

Step-by-Step Solution:
Recognize that HIV is a retrovirus with reverse transcriptase.Understand that HIV infection kills or disables CD4+ helper T cells.Connect immune destruction to the clinical syndrome called AIDS.Therefore, all statements provided are correct.

Verification / Alternative check:
Declining CD4+ T-cell counts and rising viral load correlate with disease progression; antiretroviral therapy that blocks viral enzymes reverses immune decline and reduces AIDS-defining illnesses.

Why Other Options Are Wrong:

• Each of A, B, and C is individually true but incomplete on its own.
• Only option D captures all truths together.

Common Pitfalls:
Confusing HIV (the virus) with AIDS (the syndrome). Another pitfall is assuming only one immune arm is affected; CD4+ loss impairs multiple pathways.

Final Answer:
All of the above