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p24 Antigen Assays
An alternative approach
to diagnosing HIV-1 infection is to detect the presence of viral antigens
in the blood. The best antigen for this purpose is the capsid antigen,
p24, a viral structural protein that makes up most of the virus core
particle. Because high titers of p24 antigen are present in the serum
of acutely infected individuals during the short period between infection
and seroconversion, p24 antigen assays are useful in the diagnosis
of primary HIV-1 infection.
After seroconversion the antigen is bound by p24-specific antibodies
and becomes undetectable in the majority of infected individuals.
For this reason p24 antigen assays are not useful for diagnosing HIV-1
infection in otherwise healthy individuals who are thought to have
established infection.
Later in the course of
disease, serum p24 antigen again becomes detectable in 30-70% of
patients (34; 35).
Presence of detectable p24 antigen is associated with an increased
risk of clinical progression (36). Early
studies of antiretroviral therapy used quantitative p24 assays to
assess the antiviral activity of new drugs, but this assay has been
replaced by virus load testing using RT-PCR or bDNA tests.
4/15/01
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by HIV and Hepatitis.com. All Rights Reserved
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