Broadly cross-reactive HIV neutralizing human monoclonal antibody Fab selected by sequential antigen panning of a phage display library Mei-Yun Zhang a,b , Yuuei Shu a , Sanjay Phogat a , Xiaodong Xiao a , Fatim Cham c , Peter Bouma c , Anil Choudhary c , Yan-Ru Feng c , Inaki Sanz d , Susanna Rybak e , Christopher C. Broder c , Gerald V. Quinnan Jr. c , Thomas Evans f , Dimiter S. Dimitrov a, * a Human Immunovirology Group, Laboratory of Experimental and Computational Biology, CCR, NCI-Frederick, NIH, Bldg 469, Rm 246, P.O. Box B, Miller Drive, Frederick, MD 21702-1201, USA b BRP, SAIC-Frederick, Inc., NCI-Frederick, Frederick, MD 21702, USA c Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA d Department of Medicine, University of Rochester, Rochester, NY 14642, USA e Biological Testing Branch, National Cancer Institute-Frederick, NIH, Frederick, MD 21702, USA f University of California, Davis, Tupper Hall, Davis, CA 95616, USA Received 17 June 2003; received in revised form 22 July 2003; accepted 22 July 2003 Abstract Identification of broadly cross-reactive human monoclonal antibodies (mAbs) has major implications for development of vaccines, inhibitors and research tools. Here we describe a sequential antigen panning (SAP) methodology that may facilitate the selection of such antibodies. An HIV-specific antibody Fab (m18) was selected from a human Fab phage-display library by SAP against several recombinant soluble HIV envelope glycoproteins (Envs) and Env – sCD4 complexes. This Fab bound to a variety of recombinant soluble Envs (gp140s) from primary HIV isolates representing different clades, and inhibited cell fusion and virus entry mediated by Envs of primary HIV isolates. The methodology and the results may have implications for development of HIV vaccines and inhibitors, as well as for identification of antibodies to conserved epitopes on rapidly mutating viruses and cells. Published by Elsevier B.V. Keywords: HIV; Antibody; Phage display; gp120; Inhibitors; Vaccines 1. Introduction A fundamental problem in prevention and treat- ment of HIV infections is the virus ability to rapidly generate mutants resistant to immune responses and drugs. Identification and characterization of conserved 0022-1759/$ - see front matter. Published by Elsevier B.V. doi:10.1016/j.jim.2003.07.003 * Corresponding author. Tel.: +1-301-846-1352; fax: +1-301- 846-5598. E-mail address: dimitrov@ncifcrf.gov (D.S. Dimitrov). www.elsevier.com/locate/jim Journal of Immunological Methods 283 (2003) 17 – 25