DEVELOPMENT, CHARACTERIZATION, AND BIOLOGICAL PROPERTIES OF MENINGOCOCCAL IMMUNOTYPE L3,7,(8),9-SPECIFIC MONOCLONAL-ANTIBODIES

In this study, we characterize the properties of nine monoclonal antib odies (MAbs) that recognize meningococcal lipopolysaccharides (LPS). T he following three specific MAbs that had not been described previousl y were elicited in BALB/c mice by using an immunotype L3,7,9 oligosacc haride-tetanus toxoid conjugate in combination with Quil A:4D1-B3, 3A1 2-E1, and 4A8-B2. These MAbs reacted with L3,7,9 LPS on immunoblots an d in the LPS enzyme-linked immunosorbent assay (ELISA) and recognized strains containing L3, L3,7, L8 (except 3A12-E1), or L9 LPS in the who le-cell ELISA. The six other MAbs have been described in previous stud ies (K. Saukkonen, M. Leinonen, H. Abdillahi, and J. T. Poolman, Vacci ne 7:325-328, 1989; R. J. P. M. Scholten, B. Kuipers, H. A. Valkenburg , J. Danjert, W. D. Zollinger, and J. T. Poolman, J. Med. Microbiol., in press) and were obtained after immunization with outer membrane pro tein complexes containing LPS: MN15A11, MN15A8-1, MN15A17-1, MN11A11G, MN14F20-11, and MN14F21-11. MN15A11 was specific for L3,7,9 LPS and d isplayed properties similar to those of 3A12-E1. MN15A17-1, MN14F20-1, and MN11A11G were cross-reactive, and MN14F21-11 was specific for the L1,8 immunotype. Epitope specificities of MAbs reacting with L3,7,(8) ,9 strains were analyzed. MAbs 4D1-B3, 3A12-E1, and 4A8-B2 recognized phosphoethanolamine group-containing oligosaccharide-specific epitopes . MN15A11 and MN15A17-1 were probably directed against a conformationa l epitope, although for MN5A11 recognition of an unknown L3,7,9-specif ic epitope in the 2-keto-3-deoxyoctulosonic acid (KDO)-lipid A region cannot be excluded. MN15A8-1, a strongly cross-reactive MAb, recognize d a determinant which included the KDO-lipid A region and the more ter minal saccharides. Binding inhibition assays with the four specific MA bs demonstrated that each MAb recognized a different epitope. The epit ope specificities of the other MAbs could not be defined. The biologic al functionalities of a number of the MAbs were evaluated in a bacteri cidal assay and an opsonophagocytosis assay (chemiluminescence assay). Of all MAbs that were tested (specific or cross-reactive), MN15A8-1 d isplayed strong bactericidal activity against L3,7,(8),9 and L2 strain s. However, both the specific MAbs 4A8-B2 and 3A12-E1 and the cross-re active MAb MN15A8-1 enhanced the chemiluminescence response induced by strain H44/76 (L3,7,9) but not by strains 3006 (L2) and L126E (L1,8), indicating (i) that antibodies directed against phosphoethanolamine g roup-containing oligosaccharide-specific epitopes on L3,7,9 LPS are op sonic but not bactericidal and (ii) that MAb MN15A8-1 defines a strong bactericidal determinant on immunotype L3,7,(8),9 and L2 strains.