Molecular epidemiological studies have shown that all major subtypes, including B, C, B’, BC and AE recombinant forms, exist in China, and recombinant subtypes are more prevalent [17]. In this study, we analysed the neutralizing activities of 80 serum samples derived from Chinese HIV-1 patients against a panel of HIV-1 clinical isolates and identified 8 cross-clade neutralizing sera (CNsera). We conducted further immunological characterization of the 8 CNsera to investigate the epitope specificities of the serum antibodies and the relationships to the cross-clade neutralization activity. The study shed light on the basic immunological

properties of the antibodies induced by infections of diverse viral isolates and the epitopes that mediate the cross-clade neutralizing Rucaparib purchase activities. Sera were provided by Beijing YouAn Hospital. All sera were collected from Chinese individuals infected with HIV-1 through injection drug use, sexual intercourse or commercial blood donation after informed consent was obtained. This study was approved by the institutional review board at the YouAn Hospital and Nanjing University. GHOST(3)X4/R5, 293T cell line, PNL4-3 LucR−E− and Env-expressing plasmids were kindly provided by Prof. Linqi Zhang of Comprehensive AIDS Research Center, at Tsinghua University. Mutant

Env plasmids CNE6N160K and CNE55N160K were generated using the QuickChange mutagenesis kit (Stratagene, La Jolla, CA, USA). DMEM (high glucose), Opti-MEM, trypsin and fetal bovine serum were purchased from Gibco Biotechnology Inc. (Rockville, medroxyprogesterone MD, USA). All peptides were RAD001 synthesized by GL Biochem Ltd. (Shanghai, China), and the sequences were shown in Table 1. Monoclonal antibodies (mAbs) b12, 2G12, 2F5, 4E10 and 447-52D were purchased from POLYMUN Scientific Inc. (Klosterneuburg,

Austria). Gp120IIIB, gp120JRFL, gp120JRFLD368R, gp120BC and gp120AE were purchased from HaiYuan Inc. (Taizhou, China). Mammalian cell codon-optimized V1V2BAL DNA sequences were synthesized by Invitrogen Inc. (Shanghai, China) and inserted into pTriEx-3 Hygro expression vector. V1V2BAL protein was expressed by transfecting Freestyle 293 (293F) cells in serum-free medium (Invitrogen, Carlsbad, CA, USA). Briefly, codon-optimized expression plasmid was transfected into 293F cells using PEI (Polysciences, Eppelheim, Germany) when the density of 293F cells reached 1.0 × 106/ml. The final concentrations of the plasmid and PEI were 1 μg/ml and 2 μg/ml, respectively. Supernatants were collected 6 days after transfection and concentrated using labscale tangential flow filtration cassette and system (Millipore, Billerica, MA, USA). V1V2BAL protein was purified by SwellGel Nickel-chelated discs (Pierce, Rockford, IL, USA), according to the manufacturer’s instructions.