At which stage of HIV infection does one usually show symptoms of AIDS?

Options

A. When the infecting retrovirus inters host cells.
B. When viral DNA is produced by reverse transcriptase.
C. When HIV replicates rapidly in helper T-lymphocytes and damages large number of these.
D. Within 15 days of sexual contact with an infected person.

Explanation

To determine at which stage of HIV infection one usually shows symptoms of AIDS, we need to analyze the options provided in the question:

1. **When the infected retrovirus enters into the host cell**: This is the initial stage of infection where the virus begins to enter the body and infect cells. At this stage, symptoms of AIDS are not typically present.

2. **When viral DNA is produced by reverse transcriptase**: This step involves the conversion of viral RNA into DNA, which is a crucial part of the HIV life cycle. However, symptoms of AIDS do not manifest at this stage either.

3. **When HIV replicates rapidly in helper T lymphocytes and damages a large number of these**: This is the critical stage where the virus is actively replicating and destroying helper T cells (CD4 cells). A significant decline in these cells leads to the symptoms associated with AIDS, as the immune system becomes severely compromised.

4. **Within 15 days of sexual contact with an infected person**: This option refers to the acute phase of HIV infection, which may involve mild flu-like symptoms but does not equate to the full-blown symptoms of AIDS.

Based on this analysis, the correct answer is:

**When HIV replicates rapidly in helper T lymphocytes and damages a large number of these.**

### Step-by-Step Solution:
1. **Identify the stages of HIV infection**: Understand the progression from initial infection to the development of AIDS.
2. **Evaluate each option**: Consider what happens at each stage and whether symptoms of AIDS would be present.
3. **Focus on the replication phase**: Recognize that the rapid replication of HIV in helper T cells is where significant damage occurs, leading to AIDS symptoms.
4. **Select the correct answer**: Conclude that the correct answer is the option regarding rapid replication and damage to helper T lymphocytes.