Meningococcal omp85 in detergent-extracted outer membrane vesicle vaccines induces high levels of non-functional antibodies in mice.

The vaccine potential of meningococcal Omp85 was studied by comparing the immune responses of genetically modified deoxycholate-extracted outer membrane vesicles, expressing five-fold higher levels of Omp85, with wild-type vesicles. Groups (n = 6-12) of inbred and outbred mouse strains (Balb/c, C57BL/6, OFI and NMRI) were immunized with the two vaccines, and the induced antibody levels and bactericidal and opsonic activities measured. Except for Balb/c mice, which were low responders, the genetically modified vaccine raised high Omp85 antibody levels in all mouse strains. In comparison, the wild-type vaccine gave lower antibody levels, but NMRI mice responded to this vaccine with the same high levels as the modified vaccine in the other strains. Although the vaccines induced strain-dependent Omp85 antibody responses, the mouse strains showed high and similar serum bactericidal titres. Titres were negligible with heterologous or PorA-negative meningococcal target strains, demonstrating the presence of the dominant bactericidal PorA antibodies. The two vaccines induced the same opsonic titres. Thus, the genetically modified vaccine with high Omp85 antibody levels and the wild-type vaccine induced the same levels of functional activities related to protection against meningococcal disease, suggesting that meningococcal Omp85 is a less attractive vaccine antigen.

Functional and specific antibody responses in adult volunteers in new zealand who were given one of two different meningococcal serogroup B outer membrane vesicle vaccines.

This study presents detailed analyses of total and specific serum antibody levels among 26 and 24 adult volunteers before vaccination and after the third dose of the meningococcal serogroup B outer membrane vesicle (OMV) vaccines MeNZB and MenBvac, respectively, in a clinical trial in New Zealand (V. Thornton, D. Lennon, K. Rasanathan, J. O'Hallahan, P. Oster, J. Stewart, S. Tilman, I. Aaberge, B. Feiring, H. Nokleby, E. Rosenqvist, K. White, S. Reid, K. Mulholland, M. J. Wakefield, and D. Martin, Vaccine 24:1395-1400, 2006). With the homologous vaccine strains as targets, both vaccines induced significant increases in serum bactericidal and opsonophagocytic activities and in the levels of immunoglobulin G (IgG) to OMV antigens in an enzyme-linked immunosorbent assay (ELISA) and to live meningococci by flow cytometry. They also induced high levels of activity against the heterologous strains, particularly in terms of opsonophagocytic activity and IgG binding to live bacteria. The antibody levels with the homologous and heterologous strains in the four assays showed high and significant positive correlations. Specific IgG binding to 10 major OMV antigens in each vaccine was measured by scanning of immunoblots; ELISAs for two antigens, lipopolysaccharide and Neisseria surface protein A (NspA), were also performed. Both vaccines elicited significant increases in IgG binding to all homologous and heterologous OMV antigens except NspA. The total IgG band intensity on the blots correlated significantly with the IgG levels determined by the OMV ELISA and flow cytometry. In conclusion, the results of the various immunological assays showed that both OMV vaccines gave rise to high levels of specific and cross-reacting antibodies.

Selection and characterization of cyclic peptides that bind to a monoclonal antibody against meningococcal L3,7,9 lipopolysaccharides.

There is still no general vaccine for prevention of disease caused by group-B meningococcal strains. Meningococcal lipopolysaccharides (LPSs) have received attention as potential vaccine candidates, but concerns regarding their safety have been raised. Peptide mimics of LPS epitopes may represent safe alternatives to immunization with LPS. The monoclonal antibody (MoAb) 9-2-L3,7,9 specific for Neisseria meningitidis LPS immunotype L3,7,9 is bactericidal and does not cross-react with human tissue. To explore the possibility of isolating peptide mimics of the epitope recognized by MoAb 9-2-L3,7,9, we have constructed two phage display libraries of six and nine random amino acids flanked by cysteines. Furthermore, we developed a system for the easy exchange of peptide-encoding sequences from the phage-display system to a hepatitis B core (HBc) expression system. Cyclic peptides that specifically bound MoAb 9-2-L3,7,9 at a site overlapping with the LPS-binding site were selected from both libraries. Three out of four tested peptides which reacted with MoAb 9-2-L3,7,9 were successfully presented as fusions to the immunodominant loop of HBc particles expressed in Escherichia coli. However, both peptide conjugates to keyhole limpet haemocyanin and HBc particle fusions failed to give an anti-LPS response in mice.

The four mouse IgG isotypes differ extensively in bactericidal and opsonophagocytic activity when reacting with the P1.16 epitope on the outer membrane PorA protein of Neisseria meningitidis.

Mouse monoclonal antibodies (MoAbs) of the four IgG isotypes, all specific for the P1.16 epitope on the meningcoccal PorA protein, were tested for functional activities. The avidities of the antibodies, measured by NH4SCN elution in enzyme-linked immunosorbent assay, showed similar values for all the MoAbs. The serum bactericidal activity (SBA) defined as the lowest concentration of antibodies giving 50% reduction in the number of meningococcal colony-forming units using human serum as complement, showed a hierarchy of IgG3 >> IgG2b > IgG2a >> IgG1. For the opsonophagocytosis (OP), the hierarchy was IgG3 > IgG2b = IgG2a >> IgG1. OP was measured in flow cytometry using log-phase live meningococci as target cells, normal human peripheral blood polymorphonuclear cells (PMNs) as effector cells and human serum as a complement source. The mouse MoAbs were negative in OP when using human PMNs in the absence of complement. The results demonstrate the importance of choosing the right isotype of mouse MoAbs when using them to judge the potential vaccine importance of their corresponding antigen. If such MoAbs should be used for passive vaccination against infectious diseases, the isotype would presumably play an important role for their anticipated clinical effects.

Binding properties and anti-bacterial activities of V-region identical, human IgG and IgM antibodies, against group B Neisseria meningitidis.

We have constructed chimaeric (ch) mouse/human antibodies with identical binding regions isolated from the V-genes of two mouse parent hybridoma cell lines, with specificity against the P1.7 and P1.16 epitopes on the outer-membrane protein PorA on meningococci. The chimaeric antibodies can be used to analyse relationships between specificity, binding activity (avidity and kinetics), isotype (antibody class and antibody subclass) and in vitro anti-bacterial activity of meningococcal antibodies. The antibody sets represented the human isotypes IgG1, IgG3 and IgM, which dominate during immune response against protein antigens. The binding activities were quite similar for all these isotypes, surprisingly also for the pentameric IgM. Interestingly, monomeric IgM, prepared from pentameric IgM by partially reduction and alkylation, had similar binding activities as the original pentameric IgM. Regarding in vitro anti-bacterial activity, chIgG1 was superior in SBA (serum bactericidal activity) compared with chIgG3, while chIgG3 was more efficient in OP (opsonophagocytosis; measured by flow cytometry) than chIgG1. ChIgM showed slightly higher SBA than chIgG1 on molar basis, and much higher OP than chIgG3 and chIgG1. A lower concentration of antibodies was needed against the P1.16 than against the P1.7 epitope to induce SBA, but this was not the case for OP.

Comparison of functional immune responses in humans after intranasal and intramuscular immunisations with outer membrane vesicle vaccines against group B meningococcal disease.

A serogroup B meningococcal outer membrane vesicle (OMV) vaccine was delivered either intranasally or intramuscularly to 12 and 10 volunteers, respectively. The mucosal vaccine was given as four weekly doses followed by a fifth dose after 5 months; each dose consisted of OMVs equivalent to 250 microg of protein. The intramuscular (i.m.) vaccine, consisting of the same OMVs but adsorbed to Al(OH)(3), was administered as three doses each of 25 microg of protein, with 6 weeks interval between first and second doses and the third dose after 10 months. Both groups of vaccinees demonstrated significant immune responses when measured as specific IgG antibodies against live meningococci, as serum bactericidal activity (SBA) and as opsonophagocytic activity. Two weeks after the last dose, the anti-meningococcal IgG concentrations were significantly higher in the i.m. group (median IgG concentration: 43.1 microg/ml) than in the intranasal group (10.6 microg/ml) (P=0.001). The corresponding opsonophagocytic activity was 7.0 and 3.0 (median log(2) titre) (P=0.001), and the SBA was 5.0 and 2.0 (median log(2) titre) (P=0.005), for the i.m. and intranasal groups, respectively. The last immunisation induced an enhanced immune response in the i.m. group, whereas the intranasal group showed no significant booster response. Accordingly, affinity maturation of anti-OMV-specific IgG antibodies was seen only after i.m. vaccination. The IgG1 subclass dominated the responses in both groups, whereas the significant IgG3 responses observed in the i.m. group were absent in the intranasal group. Although the intranasal OMV vaccination schedule used here induced functional immune responses relevant to protection, an improved vaccine formulation and/or a modified mucosal immunisation regimen may be needed to achieve a systemic effect comparable to that seen after three doses of intramuscular vaccination.

Immunocytochemical detection of isolated epithelial cells in bone marrow: non-specific staining and contribution by plasma cells directly reactive to alkaline phosphatase.

Detection of isolated tumour cells (TCs) in bone marrow (BM) from epithelial cancer patients by immunocytochemical (ICC) analysis seems to predict future relapse, but the reported percentages of positive BMs among patients with localized cancer show large variations and the number of detected TCs is low. This emphasizes the importance of thoroughly testing the methods in use. This study was performed to clarify to what extent positive staining of haematopoietic cells (HCs) interferes with the ICC detection of epithelial cells in BM. BM mononuclear cells (MNCs) from normal donors and stage I-II breast cancer patients were stained with anti-cytokeratin (CK) and isotype control monoclonal antibodies (MAbs) followed by alkaline phosphatase (AP)-based visualization of immunolabelled cells. In the ICC staining of normal donors by the anti-CK MAbs AE1/AE3 or A45-B/B3, rare immunoreactive cells were detected in 7/20 and 8/19 BMs, respectively. Morphological examination recognized all these cells as typical HCs. In the breast cancer patients (n = 257), anti-CK-positive cells were detected in 26.6 per cent, excluding cells with HC morphology. Using the same morphological criteria, isotype control-positive cells were detected in 5.4 per cent of patients. Some of the false-positive events were further analysed and cells with strong reactivity against the AP enzyme alone were detected. Double ICC staining recognized the majority of these AP directly-reactive cells as CD45-negative and human Ig kappa/lambda-positive, in accordance with the phenotype of mature plasma cells. Morphological evaluation and adequate controls are important to ensure the diagnostic specificity of micrometastases in BM. It is recommended that the number of BM MNCs included in negative controls should equal the number of cells in the diagnostic specimens.

Immunomagnetic techniques for the enrichment and detection of isolated breast carcinoma cells in bone marrow and peripheral blood.

Detection of isolated tumor cells (TC) in bone marrow (BM) from patients with breast cancer is usually accomplished by immunocytochemical (ICC) analysis of up to 2 X 10(6) mononuclear cells (MNC). However, this method is cumbersome if large numbers of BM cells (i.e. > 1 X 10(7) cells) are to be analyzed. This emphasizes the need for TC enrichment strategies. This report describes immunomagnetic separation (IMS) techniques for enrichment and detection of viable breast carcinoma cells in BM and peripheral blood (PB). The positive IMS technique was performed by incubation of MNC with 2.8 microns magnetic particles (rat antimouse IgG1 M280-Dynabeads) coated with monoclonal antibody (mAb) against epithelial surface antigens. The rosetted tumor cells were then visualized by ICC staining using alkaline phosphatase-conjugated A45-B/B3 anticytokeratin mAb (Fab). The negative IMS technique was performed by incubation of MNC with anti-CD45-coated M450-Dynabeads (4.5 microns), followed by ICC staining of the nonrosetted cells. When 1000, 100, and 10 breast carcinoma cells were mixed with 1 X 10(7) MNC, an average of 748 (n = 9), 70 (n = 10), and 7.8 TC (n = 8), respectively, were detected with the positive IMS technique. With the negative IMS technique, 648 (n = 8), 57.8 (n = 6), and 7.3 TC (n = 6), respectively, were detected. The analysis of 1 X 10(7) MNC with the IMS techniques was compared with the ICC analysis of 2 X 10(6) unseparated MNC. A mean 3.7-fold (range 1.5-6.4) to 4.2-fold (2.5-8.2) (positive IMS) and 3.1-fold (range 2.0-5.0) to 3.8-fold (2.0-6.0) (negative IMS) higher TC detection frequency was achieved after enrichment by IMS in experiments with 100 and 1000 TC/10(7) MNC. The IMS techniques were used for examination of BM samples from locally advanced breast cancer patients. A 5.3-fold mean increase (range 2.1-13.3) in the number of TC detected was obtained when the use of positive and negative IMS together was compared with the direct ICC analysis of unseparated MNC (n = 11). Enrichment of TC by IMS techniques enables us to examine large numbers of MNC from BM or PB, which can result in the detection and characterization of minimal residual disease with increased sensitivity and specificity.