Early HIV detection (first 6 months) is key to control HIV pandemic. Primary infection comprises both acute and early infection, and acute infection 5 phases (eclipse/Fiebig stages I-IV) until seroconversion. HIV-1 P24 capsid protein can be detected by 4th-5th generation screening immunoassays, detecting ?10pg/mL P24 (?105 virions), allowing diagnosis 3–4 weeks after infection. We present the first evaluation of a biosensor based on gold-plasmonic nanoparticles for P24 detection in samples from early and chronic infection with different HIV variants.
A new plasmonic immunoassay was used to detect 23 plasmas from patients in different HIV-1 early infection stages (4 Eclipse/19 Fiebig I-V; Panel-0800-0297-Seracare), in 25 culture supernatant with different HIV-1 subtypes and recombinants (Eqapol Genetic Diversity panel), and in 6 paired plasma/DBS from subjects in chronic infection (viremia <1.6-4.15log cop/ml). The measurement by duplicate of the plasmonic response used AVAC scanner platform (Mecwins). The gold nanoparticles were optically identified, and their scattering was analyzed to characterize, classify and count the nanoparticles present on the silicon surface due P24 detection with high specificity. Capture anti-P24-IBAB1 antibodies were used on the silicon surface and detection-anti-P24-IBAB12-antibodies (Infinity-Biomarkers) conjugated to carboxyl-polymer coated 100nm-diameter gold nanoparticles (Nanopartz).
The new biosensor showed extreme sensitivity for P24 detection at early stages, undetectable by nucleic acid technologies (NAATs), detecting 50% of Eclipse Stage, all Stage I, and all but one samples in chronic infection. The rates of false-negative samples increased in Stage II-V samples. The LOD of the new P24 assay was 10ag/mL (10?5pg/mL), equivalent to one virion in 100?l of plasma (10 virions/ml). This sensitivity is 5 orders of magnitude better than the first approved 5th immunoassay (7.02pgP24/ml, BioPlex-BioRad) and 2 orders of magnitude better than NAATs. The assay also detected P24 in all DBS/Plasma pairs, and in 11 (44%) Eqapol samples, being the remaining not detected, undetermined or discarded by biosensor surface contamination by analytes in supernatants.
We present a new molecular nanotechnology able to detect HIV in plasma and DBS specimens from acute infection, even in the first week, before any commercial serological or molecular assay. Further research is required to adapt this new tecnology at low cost and the point-of-care.