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72 Human Anti-V3 Monoclonal Antibodies (mAbs) Selected with a V3-Fusion Protein (V3-FP) Cross-React with and Neutralize HIV-1 Primary Isolates from Various Clades
M. K. Gorny*1, C. Williams1, K. Revesz2, S. Cohen1, W. J. Honnen3, C. Krachmarov3, A. Pinter3, and S. Zolla-Pazner1,2
1New York Univ. Sch. of Med.; 2Veterans Affairs Med. Ctr.; and 3Publ. Hlth. Res. Inst., New York, NY
Background: Abs against the V3 loop recognize both linear and conformational antigenic determinants, but several studies suggest that Abs specific for conformational epitopes may have more potent neutralizing activity against HIV-1. To test this hypothesis, human anti-V3 mAbs were selected using a V3-FP, which retains the V3 conformation.
Methods: Human mAbs were selected using a V3-FP consisting of the V3JR-CSF sequence inserted into a truncated form of MuLV gp70. Binding of these mAbs to preparations of 16 intact, native, primary HIV-1 virions representing clades A-G was tested by capture ELISA. The neutralizing activity of the mAbs was determined by a flow-cytometric assay, which measures the infectivity of GHOST cells by primary isolates, and a luciferase assay using SF162 and JR-FL pseudoviruses.
Results: Several human mAbs selected with the V3-FP recognize the epitopes at the crown of the V3 loop. They were found to be more dependent on conformational than linear epitopes. Extensive and strong cross-clade binding was observed with virions of clades A, B, F, and G, with only weak and sporadic binding to clades C, D, and E. The mAbs displayed cross-clade neutralizing activity in the GHOST assay, with 1 mAb neutralizing primary isolates of clades A, B, C, and F. Results with the luciferase assay showed that 50% neutralization of SF162 and JR-FL was achieved by 2 mAbs at <10 ng/ml and <25 mug/ml, respectively.
Conclusions: These studies demonstrate that anti-V3 mAbs selected with a V3 fusion protein are specific for conformational epitopes in the V3 loop. These mAbs display extensive cross-clade reactivity both in binding to native, intact primary isolates and in neutralizing primary isolates.
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