Characterization of a V3 domain-specific neutralizing human monoclonal antibody that preferentially recognizes non-syncytium-inducing human immunodeficiency virus type 1 strains

1 Institute of Virology, Erasmus University Rotterdam, Dr Molewaterplein 50, PO Box 1738, 3000 DR Rotterdam 2 Laboratory for Molecular Immunology, Central Veterinary Institute, Edelhertweg 15, 8200 AB Lelystad and 3 Laboratory of Immunobiology, National Institute of Public Health and Environmental Protection, A. van Leeuwenhoeklaan 9, 3720 BA Bilthoven, The Netherlands A type-specific human immunodeficiency virus type 1 (HIV-1)-neutralizing human monoclonal antibody (HuMAb MN215) is described that reacts with the V3 domain of a number of subtype B virus strains. Pepscan analysis indicated that amino acids at both sides of the tip of the V3 loop were involved in the binding of HuMAb MN215. The minimum epitope in a V3 sequence, obtained from the donor from whom the cell line originated, was 9 amino acids long and proved to be located at the C-terminal side of the tip of the loop. In a replacement Pepscan analysis, individual amino acids of the V3 loop important for binding of HuMAb MN215 were identified. Amino acids at positions 15 (H), 16 (I), 17 (G) and 18 (P) were found to be essential for binding of the antibody, whereas changes at positions 19 of G to N, 20 of R to K and 23 of F to L, as well as the addition of a negative charge at the C terminus, improved binding. Thus, amino acids involved in the binding of HuMAb MN215 are primarily located within highly variable regions of the V3 loop. HuMAb MN215 showed a higher affinity for the V3 domain sequences and recombinant envelope glycoproteins derived from non-syncytium-inducing strains than for those derived from syncytium-inducing strains. * Author for correspondence. Fax +31 10 4365145. e-mail osterhaus@viro.fgg.eur.nl Present address: BPRC, Lange Kleiweg 151, 2288 GJ Rijswijk, The Netherlands. Received 7 December 1994; accepted 10 March 1995.