Detection of HIV-1 p24 Gag in plasma by a nanoparticle-based bio-barcode-amplification method.
BACKGROUND
Detection of HIV-1 in patients is limited by the sensitivity and selectivity of available tests. The nanotechnology-based bio-barcode-amplification method offers an innovative approach to detect specific HIV-1 antigens from diverse HIV-1 subtypes. We evaluated the efficacy of this protein-detection method in detecting HIV-1 in men enrolled in the Chicago component of the Multicenter AIDS Cohort Study (MACS).


METHODS
The method relies on magnetic microparticles with antibodies that specifically bind the HIV-1 p24 Gag protein and nanoparticles that are encoded with DNA and antibodies that can sandwich the target protein captured by the microparticle-bound antibodies. The aggregate sandwich structures are magnetically separated from solution, and treated to remove the conjugated barcode DNA. The DNA barcodes (hundreds per target) were identified by a nanoparticle-based detection method that does not rely on PCR.


RESULTS
Of 112 plasma samples from HIV-1-infected subjects, 111 were positive for HIV-1 p24 Gag protein (range: 0.11-71.5 ng/ml of plasma) by the bio-barcode-amplification method. HIV-1 p24 Gag protein was detected in only 23 out of 112 men by the conventional ELISA. A total of 34 uninfected subjects were negative by both tests. Thus, the specificity of the bio-barcode-amplification method was 100% and the sensitivity 99%. The bio-barcode-amplification method detected HIV-1 p24 Gag protein in plasma from all study subjects with less than 200 CD4(+) T cells/microl of plasma (100%) and 19 out of 20 (95%) HIV-1-infected men who had less than 50 copies/ml of plasma of HIV-1 RNA. In a separate group of 60 diverse international isolates, representative of clades A, B, C and D and circulating recombinant forms CRF01_AE and CRF02_AG, the bio-barcode-amplification method identified the presence of virus correctly.


CONCLUSIONS
The bio-barcode-amplification method was superior to the conventional ELISA assay for the detection of HIV-1 p24 Gag protein in plasma with a breadth of coverage for diverse HIV-1 subtypes. Because the bio-barcode-amplification method does not require enzymatic amplification, this method could be translated into a robust point-of-care test.
Division of Infectious Diseases, The Feinberg School of Medicine, Northwestern University, 676 North St. Clair, Chicago, IL 60611, USA.
Eun-Young
EY
Kim
Jennifer
J
Stanton
Bette T M
BT
Korber
Kendall
K
Krebs
Derek
D
Bogdan
Kevin
K
Kunstman
Samuel
S
Wu
John P
JP
Phair
Chad A
CA
Mirkin
Steven M
SM
Wolinsky
D001681:Biological Assay / Q000379:methods; D001774:Blood Chemical Analysis / Q000379:methods*; D016655:HIV Core Protein p24 / Q000097:blood*; D015658:HIV Infections / Q000097:blood*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D018189:Immunomagnetic Separation; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods
D016655:HIV Core Protein p24; C514799:p24 protein, Human Immunodeficiency Virus Type 1