Describe the structure of the human immunodeficiency virus (HIV).

A test sample of 500 mm3 of blood is taken from an HIV controller to determine the viral load.

Tick (✓) one box that shows the number of virus particles that would be present in a test sample of blood taken from an HIV controller with the median viral load.

☐ 106 000

☐ 10 600

☐ 1060

☐ 106

Use the data in Table 3 and your knowledge of the immune response to suggest why HIV controllers do not develop symptoms of AIDS.