A novel high-throughput format assay for HIV-1 integrase strand transfer reaction using magnetic beads.

Aim: To develop a novel high-throughput format assay to monitor the integrase (IN) strand transfer (ST) reaction in vitro and apply it to a reaction character study and the identification of antiviral drugs.

Methods: The donor DNA duplex, with a sequence identical to the U5 end of HIV-1 long terminal repeats, is labeled at its 5' end with biotin (BIO). The target DNA duplex is labeled at its 3' end with digoxin (DIG). IN mediates the integration of donor DNA into target DNA and results in a 5' BIO and 3' DIG-labeled duplex DNA product. Streptavidin-coated magnetic beads were used to capture the product, and the amount of DIG was measured as the ST reaction product. The assay was optimized in 96-well microplate format for high-throughput screening purpose. Moreover, the assay was applied in a ST reaction character study, and the efficiency of the assay in the identification of antiviral compounds was tested.

Results: The end-point values, measured as absorbance at 405 nm was approximately 1.5 for the IN-mediated ST reaction as compared with no more than 0.05 of background readings. The ST reaction character and the half maximal inhibitory concentration (IC50) values of 2 known IN inhibitors obtained in our assay were similar to previously reported results using other assays. The evaluation parameter Z' factor for this assay ranged from 0.6 to 0.9.

Conclusion: The assay presented here has been proven to be rapid, sensitive, and specific for the detection of IN ST activity, the reaction character study, as well as for the identification of antiviral drugs targeting IN.