Differential Antitumor Effects of IgG and IgM Monoclonal Antibodies and Their Synthetic Complementarity-Determining Regions Directed to New Targets of B16F10-Nex2 Melanoma Cells

Malignant melanoma has increased incidence worldwide and causes most skin cancer-related deaths. A few cell surface antigens that can be targets of antitumor immunotherapy have been characterized in melanoma. This is an expanding field because of the ineffectiveness of conventional cancer therapy for the metastatic form of melanoma. In the present work, antimelanoma monoclonal antibodies (mAbs) were raised against B16F10 cells (subclone Nex4, grown in murine serum), with novel specificities and antitumor effects in vitro and in vivo. MAb A4 (IgG2ak) recognizes a surface antigen on B16F10-Nex2 cells identified as protocadherin beta(13). It is cytotoxic in vitro and in vivo to B16F10-Nex2 cells as well as in vitro to human melanoma cell lines. MAb A4M (IgM) strongly reacted with nuclei of permeabilized murine tumor cells, recognizing histone 1. Although it is not cytotoxic in vitro, similarly with mAb A4, mAb A4M significantly reduced the number of lung nodules in mice challenged intravenously with B16F10-Nex2 cells. The V(H) CDR3 peptide from mAb A4 and V(L) CDR1 and CDR2 from mAb A4M showed significant cytotoxic activities in vitro, leading tumor cells to apoptosis. A cyclic peptide representing A4 CDR H3 competed with mAb A4 for binding to melanoma cells. MAb A4M CDRs L1 and L2 in addition to the antitumor effect also inhibited angiogenesis of human umbilical vein endothelial cells in vitro. As shown in the present work, mAbs A4 and A4M and selected CDR peptides are strong candidates to be developed as drugs for antitumor therapy for invasive melanoma.

Development of monoclonal antibodies against Vibrio pathogens

Monoclonal antibodies were developed against pathogenic vibrios for use in rapid identification in disease situations of humans, fish and shellfish. Of the 12 fusions performed using V. alginolyticus, V. anguillarum, V. carchariae, V. cholerae, V. damsela, V. furnissii, V. harveyi, V. ordalii, V. parahaemolyticus and V. vulnificus, a total of 102 hybridomas were obtained. Based on cross-reactivity of a wide range of Vibrio strains and other gram-negative bacteria, three broad types of monoclonal antibodies were found. The three categories were: (1) ones that were species-specific or specific to a particular surface antigen, (2) a large number that reacted with several Vibrio species, and (3) three that reacted with most Vibrio strains but no other gram-negative bacteria. Each species-specific monoclonal antibody only recognized its corresponding Vibrio species and was used for identifying unknown species, confirming diagnosis of clinical isolates. In addition, several monoclonal antibodies only cross-reacted with similar Vibrio species, e.g. V. parahaemolyticus and V. alginolyticus which share a common H-antigen. Monoclonal antibodies reacting with several Vibrio species were not of particular use in diagnostic situations. Three monoclonal antibodies of the last group did not react with other genera of the family Vibrionaceae, namely Aeromonas, Photobacterium and Plesiomonas nor a wide range of gram-negative enteric bacteria. These data indicated the existence of an antigenic surface determinant common to Vibrio species. One monoclonal reacted with the heat-stable antigenic determinants on the cell surface as v as lipopolysaccharide extracted from all the vibrios studied, thus making it useful for large- scale screening of acute infections of vibrios. In a blind test, seven Vibrio species, isolated from 6 marine and a freshwater source were identified by two laboratories using phenetic tests. Results of immunotyping using monoclonals, three of seven were diagnosed as the same species, another three were designated as Vibrio species but could not be classified further due to the library not having the corresponding monoclonal, and one was diagnostically questionable. Two further tests were carried out. An unknown Vibrio formalin-fixed isolated from diseased marine animal was identified as V. parahaemolyticus by ELISA and FITC. Clinical human isolates of V. alginolyticus, V. parahaemolyticus and V. vulnificus were confirmed by monoclonals. Australian isolates of V. anguillarum appeared to be mostly of serotype O1. monoclonals raised to V. anguillarum AFHRL 1 reacted with only serotype O1 from Denmark but also most Australian isolates. All vibrios pathogenic to fish and shellfish, i.e. V. anguillarum, V. ordalii, V. alginolyticus, V. carchariae, V. cholerae, V. damsela, V. harveyi, V. parahaemolyticus and V. vulnificus, were used for attachment studies to fish cells using phase contrast and FITC-immunofluorescence microscopy. Of these vibrios, V. anguillarum, V. ordalii and V. perahaemolyticus, were found to adhere to different cells and tissues of rainbow trout while others did not appear to attach. However, attachment was inhibited by monoclonal antibodies specific to only these three vibrios. Lipopolysaccharide is well known as being a contributing factor in pathogenicity of gram-negative bacteria. PAGE electrophoresis of extracted LPS from 9 strains covering 6 Vibrio species showed the presence of a common 15,000 D fragment. This fragment was verified by immunoblotting with a genus-specific monoclonal antibody (i.e. F11P411F) recognizing nearly all vibrios. The common LPS fragment was separated and used to raise polyclonal antisera in mouse which reacted strongly with LPS itself, live as well as sodium azide-killed vibrios, but not with other gram-negative bacteria. This raised the possibility of developing vaccine from Vibrio LPS. Monoclonal antibodies developed in the present study enabled rapid identification of a number of pathogenic Vibrio species. There is still further work to produce monoclonal antibodies against additional vibrios that are probably pathogenic. These included V. fluvialis, V. hollisae, V. metschnikovii, V. minicus, V. salmonella and V. tubiashii. Together the application will be of significance in clinical diagnostic work, in the monitoring of vibriosis in fish farms and in quarantine.

Antigenic relationships between bluetongue virus serotypes as defined by monoclonal antibodies

Panels of monoclonal antibodies (MAbs) were generated to individual proteins of an Australian isolate of bluetongue virus (BTV) serotype 1 (VP2, VPS, VP5, VP6, NS1 and NS2). The number of individual epitopes and antigenic regions each panel defined were then determined. Relative epitope conservation levels amongst heterologous serotypes of BTV from three geographic regions (Australia, the United States and South Africa) were then investigated for each protein through the development of a quantitative binding assay. Epitopes on VP2 displayed the most and VP7 and NS1 epitopes the least, variation in epitope conservation across the BTV serogroup. Epitopes on VPS and VP6 showed moderate to high levels of variation and NS2 epitopes displayed surprisingly high levels of variation. A comparison of epitope reactivity on released and cytoplasmic lysate antigen preparations revealed the expression of several epitopes on VP2 and VP7 are blocked through the conformational changes induced by the incorporation of each protein into the virus particle* This suggested some form of environmental pressure/s were responsible for the selection of specific protein conformations. For VP7, the patterns of epitope expression on the virus displayed some relationship to the geographic origin of BTV isolates and therefore indicated the detection of such epitopes might assist in the topotyping of unknown isolates. Binding and neutralization studies applied to the reaction of VP2-specific MAbs with natural and experimentally selected BTV-1 variants showed at least seven neutralization epitopes exist within a single domain. However, only one of these appeared crucial to serotype determination. In addition, escape from virus neutralization was shown to involve the re-conformation of previously neutralizing epitopes to a non-neutralizing orientation which did not necessarily compromise the binding properties of the epitope. The simultaneous reaction of certain neutralization-resistant variants and heterologous serotypes with several MAbs specific for such epitopes, resulted in low level virus neutralization. This may explain the phenomenon of heterotypic immune responses frequently observed in natural hosts.

Analysis of the serological variability of Lettuce mosaic virus using monoclonal antibodies and surface plasmon resonance technology

A panel of 19 monoclonal antibodies (mAbs) was used to study the immunological variability of Lettuce mosaic virus (LMV), a member of the genus Potyvirus, and to perform a first epitope characterization of this virus. Based on their specificity of recognition against a panel of 15 LMV isolates, the mAbs could be clustered in seven reactivity groups. Surface plasmon resonance analysis indicated the presence, on the LMV particles, of at least five independent recognition/ binding regions, correlating with the seven mAbs reactivity groups. The results demonstrate that LMV shows significant serological variability and shed light on the LMV epitope structure. The various mAbs should prove a new and efficient tool for LIVIV diagnostic and field epidemiology studies.

Taenia saginata: Production and characterization of monoclonal antibodies against Taenia saginata metacestode antigens

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

IMMUNOCYTOCHEMICAL DIFFERENTIATION OF REACTIVE HYPERPLASIA FROM FOLLICULAR LYMPHOMA USING MONOCLONAL-ANTIBODIES TO CELL-SURFACE AND PROLIFERATION-RELATED MARKERS

We tested the hypothesis that a panel of antibodies to cell surface, cytoplasmic, and nuclear antigens could reliably distinguish the cells composing reactive germinal centers from those composing follicular lymphoma. Immunocytochemistry was performed on deparaffinized sections of methacarn-fixed lymph node and tonsil (15 cases of reactive hyperplasia and 14 cases of follicular lymphoma) using antibodies to the nerve growth factor receptor (NGFR5), bcl-2 protein (124), proliferating cell nuclear antigen (PCNA; 19A2), and CD45RA (MT2). In 100% of cases of reactive hyperplasia, both MT2 and 124 showed positive immunostaining of mantle zone and scattered interfollicular lymphocytes, but in all cases there was a sharply demarcated absence of immunostaining of germinal center cells. However, diffuse immunostaining of follicular centers with MT2 (64%) and 124 (93%) and scattered intervening cells were seen in follicular lymphoma. The combination of antibodies to CD45RA and bcl-2 yielded positive immunostaining of follicular center cells in 93% of follicular lymphomas. The germinal center cells of reactive hyperplasia showed >75% nuclear positivity with antibodies to PCNA, in contrast to the follicular lymphoma cells, which showed variable PCNA indices ranging from 25 to >75%. A minority of follicular lymphoma cases (29%) showed PCNA indices comparable with those seen in cases of reactive hyperplasia. Antibodies to NGFR were positive in all cases of reactive hyperplasia and in 79% of cases of follicular hyperplasia, although the immunostaining intensity was generally decreased in follicular hyperplasia. In summary, antibodies to bcl-2 appear to be superior to those to CD45RA in distinguishing reactive hyperplasia from follicular lymphoma. Reactive hyperplasia cannot be discriminated from follicular hyperplasia using antibodies to PCNA or to nerve growth factor receptor.

Monoclonal antibodies against the 43,000 da glycoprotein from Paracoccidioides brasiliensis modulate laminin-mediated fungal adhesion to epithelial cells and pathogenesis

The surface glycoprotein gp43, a highly immunogenic component of Paracoccidioides brasiliensis, is used in the serodiagnosis of paracoccidioidomycosis (PCM) and has recently been shown to specifically bind the extracellular matrix protein laminin, Binding to laminin induces the increased adhesion of the fungus to epithelial cells; a hamster testicle infection model has shown that the gp43-dependent binding of fungal cells to laminin enhances their pathogenicity in vivo. We report on the production and characterization of 12 monoclonal antibodies against the gp43 that recognize peptide sequences in the molecule detecting at least three different epitopes as well as different isoforms of this antigen. MAbs interfered in the fungal pathogenicity in vivo either by inhibiting or enhancing granuloma formation and tissue destruction, Results suggest that P. brasiliensis propagules may start infection in man by strongly adhering to human lung cells, Thus, laminin-mediated fungal adhesion to human lung carcinoma (A549) cells was much more intense than to Madin-Darby canine kidney cells (MDCK), indicating differences in binding affinity, Subsequent growth of fungi bound to the lung cells could induce the granulomatous inflammatory reaction characteristic of PCM. Both steps are greatly stimulated by laminin binding in infective cells expressing gp43.

Production of monoclonal antibodies against Streptococcus mutans antigens

Several studies have been conducted in the last decades aiming to obtain an anti-canies vaccine, however some studies have demonstrated cross reactivity between Streptococcus mutans surface antigens and the human cardiac tissue. In this work, the reactivity of five anti-Streptococcus mutans monoclonal antibodies (MoAb) (24A, 56G, G8, E8 and F6) was tested against oral streptococci, cardiac antigens and skeletal and cardiac myosins, aiming to evaluate the specificity of these MoAb. The hybrid producers of immunoglobulins of the IgG 2b class were cloned by limit dilution and expanded in vivo. MoAb were tested by ELISA. The hybrid 24A reacted with S. mutans CCT 1910, S. salivarius CCT 0365 and S. pyogenes T23. No reactivity difference was observed among the tested species. Cross reactivity with heart and cardiac myosin was not confirmed and only reaction with myosin of skeletal muscle was observed (p = 0.0381). The hybrid 56G reacted with all the tested microorganisms and there was statistically significant difference between S. mutans and S. pyogenes T23 (p < 0.001). This hybrid also reacted with myosin of skeletal muscle (p = 0.0095). C8, E8 and F6 presented low reactivity against oral streptococci strains and no reactivity against cardiac antigens. The data of this study showed that the 24A and 56G anti-S. mutans MoAb presented reactivity with S. pyogenes and S. salivarius, reinforcing the occurrence of common antigens between these species. The tested MoAb presented low cross-reactivity with myosin of skeletal muscle, but anti-heart activity could not be confirmed.