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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assess the antiviral activity of new drugs, but this assay has been
replaced by virus load testing using RT-PCR or bDNA tests.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
Copyright 2001
by HIV and Hepatitis.com. All Rights Reserved
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