Grouping of haemolytic streptococci by monoclonal antibodies: determinant specificity, cross-reactivity and affinity

Immunogenicity of liposome-bound hyaluronate in mice. At least two different antigenic sites on hyaluronate are identified by mouse monoclonal antibodies

Hyaluronate (HA) was previously demonstrated to be immunogenic in rabbits. The immunogenicity of HA in mice was studied. Hyaluronidase-digested streptococcal HA (IA1) covalently linked to liposomes (IA1-liposomes) were produced for immunization. Mice immunized with IA1-liposomes developed measurable serum antibodies to IA1, while mice immunized with IA1 in Freund's adjuvant did not. mAbs produced by two stable hybridomas (10G6 and 5F11) from mice immunized with IA1-liposomes produced IgG antibody reactive with HA in ELISA. 10G6 had a much higher avidity for liposome-bound IA1 than free IA1, while 5F11 did not, suggesting that the mode of presentation of IA1 is important in HA immunogenicity and antigenicity. Both mAbs recognized terminal HA immunodeterminants exposed by hyaluronidase treatment. Sonication had no effect on HA reactivity for either mAb. However, ascorbic acid treatment significantly reduced the antigenicity of HA for mAb 5F11, but not 10G6. Only 10G6 was inhibited by glucuronic acid. Electrostatic forces appear to play a role in the binding site of 5F11, but not 10G6. 5F11 crossreacts with heparan sulfate and phosphorylcholine, while 10G6 did not crossreact with any glycosaminoglycans or phosphorylated compounds tested. These results confirm that HA is immunogenic. They suggest that the mode of presentation of HA is important for the induction of the immune response, and in HA antigenicity. At least two different antigenic sites on HA were demonstrated. 10G6 recognizes a terminal HA antigenic site expressed on IA1-liposomes that contains glucuronic acid in its immunodominant site. 5F11 recognizes an HA antigenic site in which electrostatic forces appear to play a role, is sensitive to ascorbic acid treatment, and is crossreactive with heparan sulfate. The use of mAbs should facilitate immunologic studies of HA.

Monoclonal antibodies to the multienzyme enniatin synthetase. Production and use in structural studies

Monoclonal antibodies have been prepared against the multifunctional enzyme enniatin synthetase, which catalyses the biosynthesis of the cyclodepsipeptide antibiotic enniatin. Five different antibodies (designated 1.56, 21.1, 25.91, 28.7 and 28.34) were characterized. 1.56, 21.1 and 25.91 were of IgG1 and 28.7 and 28.34 of IgM subclass. Binding studies showed that 21.1 and 25.91 are obviously directed against determinants based on the primary structure of the enzyme, whereas 28.7, 28.34 and 1.56 bind to the native enzyme. All antibodies inhibited enniatin formation. Based on their ability to inhibit different partial reactions of the multienzyme the antibodies could be divided into three groups: 21.1 and 25.91 inhibit valyl thioester formation, 1.56 additionally inhibits D-2-hydroxyisovaleric acid thioesterification, and 28.7 and 28.34 block both thioester sites as well as the N-methylation step. None of the antibodies affected the formation of L-valyl or D-hydroxyisovaleryl adenylate by the enzyme. The results indicate that there must be distinct thioester activation sites for valine and D-hydroxyisovalerate close to each other and in the neighbourhood of the methyltransferase site. The adenylation sites for D-hydroxy-isovalerate and L-valine are obviously located at some distance.

Serotyping and electron microscopy studies of Staphylococcus aureus clinical isolates with monoclonal antibodies to capsular polysaccharide types 5 and 8

Monoclonal antibodies to Staphylococcus aureus capsular polysaccharide types 5 and 8 were prepared and used to serotype 821 clinical isolates of S. aureus from four countries. The capsular polysaccharide-binding sites on the bacterial membrane were examined by transmission and scanning electron microscopy.

Clinical applications of monoclonal antibodies

This review highlights the properties, problems, and potentials of monoclonal antibodies as diagnostic and therapeutic agents. The most extensive experience has been obtained with antibodies specific for functionally distinct subsets of lymphocytes. They have been used to monitor the immunosuppression of organ-graft recipients and to attempt to elucidate the disturbance of immunologic function in a variety of conditions. Current therapeutic applications under trial include immunosuppression to treat organ-graft rejection and to eliminate cells responsible for graft-vs-host disease from the bone marrow. Applications to cancer diagnosis and treatment have been hampered by the difficulty of identifying truly tumor-specific antigens. Successes have, however, been obtained in the location of metastases and in the extracorporeal treatment of autologous marrow to purge it of malignant cells, and, more rarely, with the direct administration of monoclonal antibodies in vivo. The conjugation of cell-type specific monoclonal antibodies with cytotoxic agents should overcome a number of limitations.