lab diagnosis of hiv · 2 the role of proviral dna tests • hiv-1 proviral dna can be detected by...
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Dr Sarah Sasson Immunopathology Registrar
HIV, Immunology and Infectious Diseases Department and SydPath, St Vincent's Hospital
HIV: Basic Virology
Courtesy of Philip Cunningham
HIV testing @ SydPath
1) Architect 4th generation chemiluminescence assay
• Detects p24 Ag and Ab to HIV-1 and HIV-2
2) (if +) Genscreen
• Detects Ab to HIV-1 and HIV-2
3) (if +) p24 ELISA & HIV Western Blot
Courtesy Philip Cunningham, St Vincent's Hospital Sydney
Evolution of HIV Western Blot
• Highly Specific
• Less Sensitive
• Expensive $$$
• Results may be:
POSITIVE
NEGATIVE
INDETERMINATE
DNA PCR RNA PCR
p24 Ag
1wk 2wk 3wk 2mo 6mo 1yr 2yr 3yr +8yr
early recent/established late
Evolution: antibody/ antigen testing response
Courtesy of Philip Cunningham
The role of proviral DNA tests
• Detection of HIV-1 proviral DNA by PCR can provide early evidence of HIV-1
infection (approximately 10-14 days after infection), when results of routine
diagnostic assays are inconclusive.
• The linear cDNA transcripted prior to integration is the “proviral” DNA.
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The role of proviral DNA tests
• HIV-1 proviral DNA can be detected by a PCR that targets a segment of the highly
conserved HIV-1 gag gene or LTR region. Clinical studies have indicated this is
highly sensitive (>95%) and specific (>98%).
• Currently SydPATH is the only site licensed in Australia for this test
• The limit of detection is 10 copies/μL
• Research assays can detect 0.3 copies/ μL
HIV Monitoring and management tests
• CD4 count and percentage
• HIV VL
• Viral genotype
• Viral resistance
• Viral tropism
• HLA B57