The phenotype of those with specific or unique amino acid mutation at integrase gene will be determined using in-house phenotypic assay. Briefly, the p7 to vif fragment, about 3.6kb, will be amplified from patients' plasma viral RNA and cloned into our backbone viral clone (Figure 1). The resultant clones will be transfected into 293 cells to produce infectious viruses, whose titers will be determined by p24 assay and equal amounts of viruses will be subsequently used to infect PBMC from healthy donors. Virus titers in the supernatants from infected cells after 3, 5, and 7 days post infection in the presence or absence of tested compounds will be determined by real-time PCR or p24 assay. The minimal concentration of compounds required to reduce 50% of supernatant viral copies (EC50) will be calculated by regression analysis of the dose-response curves generated from real-time PCR or p24 assay.