1. Within the
envelope of the HIV
virus is a bullet-shaped core made of another protein, p24, that surrounds the viral
RNA. 2. The
p24 antigen test looks for the presence of this protein in a patient's blood. 3. A positive result for the
p24 antigen suggests active HIV replication.
p24 found in the peripheral blood is thought to also correlate with the amount of
virus in the peripheral blood. It is believed that there are measurable levels of
p24 when first infected with the
virus after which there is a strong antibody response to
p24 in early disease. Low or unmeasurable levels of
p24 may indicate that the
virus is in a dormant stage. Spikes in
p24 levels may indicate that HIV has begun active replication.