Quantitative detection of HIV-1 particles using HIV-1 neutralizing antibody-conjugated beads.

The human immunodeficiency virus (HIV) pandemic mainly affects developing countries, where the Joint United Nations Programme on HIV/AIDS (UNAIDS) estimates suggest that less than 1 in 10 people are aware of their HIV sero-status. In order to enhance epidemiological surveys, prevention programs, and therapeutic interventions, development of specific, rapid, and convenient diagnostic detection systems is still warranted. Here we report the direct detection of HIV particles using broadly HIV-1 neutralizing gp120 monoclonal antibody (gp120MAbs)-conjugated magnetic beads (MBs) and fluorescent nanosized polymeric beads (FNBs). The HIV-1 envelope glycoprotein gp120 is anchored to the viral surface through gp41 and mediates entry into target cells by interaction with the main cellular receptor (CD4) and coreceptors (e.g., CCR5 and CXCR4). FNBs conjugated to gp120MAbs (gp120MAbs-FNBs) were used to generate fluorescent signals, whereas MBs conjugated to gp120MAbs (gp120MAbs-MBs) were employed to isolate HIV-1 particles. In presence of HIV-1 particles, addition of gp120MAbs-FNBs and gp120MAbs-MBs leads to the formation of a MBs/HIV-1 particles/FNB complex, which can be easily isolated and concentrated by common magnet separation. We demonstrate the ability of detecting HIV-1 particles specifically and directly using MBs and FNBs with low sample volume (less than 100 microL) and rapidity (less than 1.5 h) without any pretreatment of test samples. The specific binding of FNBs with HIV-1 particles on the surface of MBs was confirmed by fluorescence microscopy and fluorescence-activated cell sorting (FACS). Imaging and FACS analysis revealed the specific and quantitative detection of HIV-1 particles. These results provide proof-of-principle that broadly HIV-1 neutralizing gp120 antibodies coupled to nanobeads can be employed for the direct detection of HIV-1 particles with potential implication for the development of specific, rapid, and convenient diagnostic systems.