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COVID-19, caused by SARS-CoV-2, and meningococcal disease, caused by Neisseria meningitidis , are relevant infectious diseases, preventable through vaccination. Outer membrane vesicles (OMVs), released from Gram-negative bacteria, such as N. meningitidis , present adjuvant characteristics and may confer protection against meningococcal disease. Here, we evaluated in mice the humoral and cellular immune response to different doses of receptor binding domain (RBD) of SARS-CoV-2 adjuvanted by N. meningitidis C:2a:P1.5 OMVs and aluminum hydroxide, as a combined preparation for these pathogens. The immunization induced IgG antibodies of high avidity for RBD and OMVs, besides IgG that recognized the Omicron BA.2 variant of SARS-CoV-2 with intermediary avidity. Cellular immunity showed IFN-γ and IL-4 secretion in response to RBD and OMV stimuli, demonstrating immunologic memory and a mixed Th1/Th2 response. Offspring presented transferred IgG of similar levels and avidity as their mothers. Humoral immunity did not point to the superiority of any RBD dose, but the group immunized with a lower antigenic dose (0.5 μg) had the better cellular response. Overall, OMVs enhanced RBD immunogenicity and conferred an immune response directed to N. meningitidis too.

The elderly are more likely to die when infected with Neisseria meningitidis. Aging is associated with immune system dysfunctions that impair responses to vaccines and infections. Therefore, immunization of middle-aged individuals could be beneficial. This study aims to evaluate the immunogenicity of N. meningitidis B outer membrane vesicles (OMVs) complexed to two different adjuvants. Middle-aged BALB/c and A/Sn mice were immunized and subsequent immune response was assessed by ELISA, immunoblotting and ELISpot. IgG levels were similar between the animals immunized with OMVs complexed to adjuvants. A total of 235 days after the last immunization only A/Sn mice presented higher IgG levels than those observed in the baseline, especially the group immunized with OMVs and aluminum hydroxide. The predominant IgG subclasses were IgG2a and IgG2b. Immunization with the three-dose regimen generated IgG antibodies that recognized a variety of antigens present in the homologous and heterologous meningococcal OMVs evaluated. There was an increase in the frequency of antigen-specific IFN-γ secreting splenocytes, after in vitro stimulation, in mice immunized with OMVs and adjuvants compared to the control group, almost 1 year after the last immunization. Both adjuvants showed similar performance. Immunization of middle-aged mice has generated a robust immune response and it appears to be advantageous., (© FEMS 2020.)

The aim of this study was to determine the value of detoxified Shiga toxins Stx1 and Stx2 (toxoids of Escherichia coli) as mucosal adjuvants in neonatal mice for immunogenicity against the outer membrane proteins (OMPs) of Neisseria meningitidis B. Mucosal immunization has been shown to be effective for the induction of antigen-specific immune responses in both the systemic and mucosal compartments. Systemic antibody levels (IgG, IgG1, IgG2a, IgG2b, IgM, and IgA) and mucosal IgM and IgA were measured by ELISA using an N. meningitidis as an antigen. In addition, IFN-γ and IL-6 production were measured after stimulated proliferation of immune cells. Intranasal administration elicited a higher anti-OMP IgA response in both saliva and vaginal fluids. Our results suggest that both Stx1 and Stx2 toxoids are effective mucosal adjuvants for the induction of Ag-specific IgG, IgM, and IgA antibodies. The toxoids significantly enhanced the IgG and IgM response against OMPs with a potency equivalent to CT, with the response being characterized by both IgG1 and IgG2a isotypes, and increased IFN-gamma production. Additionally, bactericidal activity was induced with IgG and IgM antibodies of high avidity. These results support the use of the new toxoids as potent inducing adjuvants that are particularly suitable for mucosal immunization.

Abstract Neisseria lactamica, a commensal bacterium that is non-pathogenic to humans and is usually found in the upper respiratory tract of children, is closely related to the pathogenic species Neisseria meningitidis. Colonization by Neisseria lactamica can be responsible for the development of natural immunity to meningococcal infection in childhood, when rates of meningococcal carriers are low. These features suggest that N. lactamica components can be key elements in the production of a new vaccine for N. meningitidis. The production of monoclonal antibodies for N. lactamica is an important tool in the selection of new antigens for the preparation of a vaccine for N. meningitidis B.

Background: A simple filter paper method was developed for, the transport and storage of monoclonal antibodies (Mabs) at room temperature or -20 degrees C after spotting on filter paper, for subsequent serotyping of outer membrane antigens of N.meningitidis by dot-blot ELISA., Methods: Monoclonal antibodies (Mabs) were spotted within a 0.5-1 cm diameter area of Whatman grade 903 paper, which were stored individually at room temperature or at -20 degrees C. These MAbs were stored and analyzed after periods of one week, 4 weeks, 12 months, or 13 years in the case of frozen Mab aliquots, or after 4 weeks at -20 degrees C or at room temperature (RT) in the case of Mabs dried on filter paper strips. Assays were performed in parallel using dot-blot ELISA. In addition to the MAbs specific for serotyping class 1, 2 or 3, we used a larger number of Mabs for polysaccharides, lipooligosaccharides (LOS), class 5 and cross-reactive antigens for native outer membrane of N.meningitidis. The Mabs dried on filter paper were eluted with phosphate-buffered saline (PBS) containing 0.2% gelatin., Results: Mabs of the isotypes IgG and IgM dried on filter papers were not affected by duration of storage. The detection by serotyping Mabs was generally consistent for dried filter paper MAb samples stored frozen for over 1 year at -20 degrees C, and although decreased reactive antibody titers were found after storage, this did not interfere with the specificity of the Mabs used after 13 years as dry spots on filter paper., Conclusion: The use of filter paper is an inexpensive and convenient method for collecting, storing, and transporting Mab samples for serotyping studies. In addition, the samples occupy little space and can be readily transported without freezing. The efficiency of using immunoglobulin G (IgG) or M (IgM) eluted was found to be consistent with measurement of IgG or IgM titers in most corresponding, ascites Mabs stored frozen for over 1 year. The application of meningococcal typing methods and designations depend on the question being asked.

A rapid and efficient method for preparing monoclonal antibody (MAb) serotypes using Neisseria meningitidis outer membrane were used in BALB/c mouse footpads for the immunization. The popliteal lymph nodes were isolated 19 days later for MAb-producing hybridomas, from which the MAbs against the 37 kDa protein were screened. Variations in class 2/3 (PorB) proteins form the basis for meningococcal serotyping. This is the first report on the preparation of MAbs against N. meningitidis that is specific to PorB protein using popliteal lymph nodes. The new monoclonal antibodies were specific for PorB outer membrane protein FL24(PL)Br, a new serotype 24 class 3 antigens of non-typeable (NT:NST) serogroup B strain, and FL14(PL)Br specific for the serotype 14, and reacted with the S3446 reference strain analyzed. A total of 12% of the case isolates reacted with one or more of the monoclonal antibodies. The high-affinity MAbs produced by hybridoma methodology provide a basis for further research on the pathogenesis and early diagnosis of meningococcus.

A new monoclonal antibody (5F81A4P1.9), which is specific for subtype 9 antigen of meningococci, was studied. The antibodies were raised against a previously non-typable (NT) serogroup B strain from Brazilian patients and were found to react with the subtype antigen of prototype reference strains for subtype 9 (M982), as well as with those of homologous strains. The subtype 9 epitope was found in 6.8% of serogroup B strains among 602 strains of Neisseria meningitidis case isolates, including representative isolates from Brazilian states. Subtype P1.9 was predominantly related to serogroup B in Brazil among the isolates collected during the N. meningitidis epidemic in 1992. No significant differences were observed in the occurrence of subtype P1.9 among strains isolated from several Brazilian states. Fluorescence-activated cell-sorter analysis showed that 5F81A4 MAb recognized a 46 kDa protein on the surface of a homologous strain of N. meningitidis (B:4:P1.9). These results, in association with a bactericidal activity assay for 5F81A4, and with experimental passive protection in mice, demonstrated the importance of subtype 9 class 1 proteins of N meningitidis in Brazil. Serotyping is essential for the development of vaccination strategies.

The meningococcal disease is a global health threat, but is preventable through vaccination. Adjuvants improve meningococcal vaccines and are able to trigger different aspects of the immune response. The present work evaluated the immune response of mice against Neisseria meningitidis outer membrane vesicles (OMV) complexed with the adjuvants aluminium hydroxide (AH), via subcutaneous route; and dimethyldioctadecylammonium bromide (DDA) or Saponin (Sap), via intranasal/subcutaneous routes. ELISA demonstrated that all adjuvants increased IgG titers after the booster dose, remaining elevated for 18 months. Additionally, adjuvants increased the avidity of the antibodies and the bactericidal titer: OMVs alone were bactericidal until 1:4 dilution but, when adjuvanted by Alum, DDA or Sap, it increased to 1/32. DDA and Sap increased all IgG isotypes, while AH improved IgG1 and IgG2a levels. Thus, Sap led to the recognition of more proteins in Immunoblot, followed by DDA and AH. Sap and AH induced higher IL-4 and IL-17 release, respectively. The use of adjuvants improved both cellular and humoral immune response, however, each adjuvant contributed to particular parameters. This demonstrates the importance of studying different adjuvant options and their suitability to stimulate different immune mechanisms, modulating the immune response. [ABSTRACT FROM AUTHOR]

Adjuvants are important components of vaccines, increasing immunogenicity and modulating the immune response. SARS-CoV-2 vaccines are still being developed in order to improve worldwide access to immunization. Specific populations should be addressed in these investigations, such as pregnant women—to protect both mothers and neonates. In this study, female adult mice were immunized with Receptor-binding domain (RBD) from SARS-CoV-2 adjuvanted by a mixture of DDA and Saponin and put to mating to verify the maternal transference of IgG. For comparison, other group received RBD adjuvanted by OMVs from Neisseria meningitidis and Alum. The adjuvants enhanced IgG production and neutralization. DDA/Sap contributed to increase IgG1, IgG2a, IgG2b, and IgG3 isotypes. Total IgG avidity was considered high, as well as IgG1, IgG2a, and IgG2b avidity. IgG antibodies were effectively transferred to the offspring, predominantly IgG2a, IgG2b, and IgG3. The passive transferred immunoglobulin maintained the neutralizing ability, although it lost avidity. ELISA data was confirmed in Dot-ELISA and immunoblotting assays. DDA and Saponin seem a promising adjuvant mixture to enhance the humoral response of SARS-CoV-2 antigens. Further studies considering the effects of maternal immunization in the protection of offspring are needed, regardless the platform used in COVID-19 vaccines. [ABSTRACT FROM AUTHOR]

Purpose: In the present study, meningococcal serogroup B outer membrane vesicles (OMVs) were associated with bilayer fragments of a cationic lipid, dioctadecyldimethylammonium (DDA-BF), used as adjuvant, in an antigenic preparation tested in adult female outbred mice. This adjuvant was compared to the traditional adjuvant aluminum hydroxide. Materials and Methods: The potential in generating humoral response was evaluated by enzyme-linked immunosorbent assay (ELISA). Individual serum was collected and immunoglobulin G (IgG), IgG1, IgG2a, and IgG2b were quantified. Analyses were carried out 15 and 60 days after immunization. Antibodies avidity index were also analyzed by ELISA. Immunoblot and dot-ELISA were carried out to evaluate specific reaction for homologous strains and crossreactive antigens present in other meningococcal strains isolated in 2011-2012 year, in Brazil. Delayed type hypersensitivity was used as indicative of cellular immunity and compared between two experimental groups, 24 hours after homologous strain challenge. Results: The OMVs of Neisseria meningitidis, and N. lactamica (related species) were characterized by electrophoretic separation of proteins in 13% polyacrylamide gel. The strains presented antigens in the range of 8 to 130 kDa, showing a heterogeneous protein migration pattern. In the group immunized with OMVs/DDA-BF, we found no significant production of total IgG 15 days after the first immunization. On the other hand, 60 days after first immunization both adjuvants act benefiting total IgG production similarly. The antibodies of the IgG isotype produced by animals immunized after one or two doses after first immunization, showed intermediate and high avidity, independent on the adjuvant used. In both experimental groups the swelling of the footpads was significantly higher than those of the controls, suggesting that only one dose was enough to stimulate the generation of cellular immunity. Conclusion: The use of this cationic adjuvant for N. meningitidis OMVs preparation revealed good potential for future new antigen preparation for N. meningitidis vaccine. [ABSTRACT FROM AUTHOR]

Literature reports the association between aging and decline in the immune system function. The elderly have a higher risk of developing infectious diseases and are often less responsive to vaccines that are effective in the young. The case fatality rate of invasive meningococcal disease is higher in the elderly; therefore, vaccination for this population should be evaluated. Although new vaccines have been developed against Neisseria meningitidis, there is still a need to evaluate a vaccine for those older than 60 years, as the currently licensed vaccines are not indicated for this population. [ABSTRACT FROM AUTHOR]

Neisseria meningitidis bacterium is a Gram-negative diplococcus. Among their serogroups, the B is one of the main causes of invasive meningococcal disease. Newborns and children are particularly susceptible to this infection because of their immune systems that are still maturing and relatively inexperienced. Thus, further studies on the use of maternal immunization for protection against this disease are needed. The purpose of this study was to evaluate the potential immunogenic antigens from the outer membrane of N. meningitidis serogroup B in outbred mice and the influence of maternal immunization in the offspring, and analyze the adjuvant effect of bilayer fragments of dioctadecyldimethylamonium bromide (DODAB-BF) and hydroxide aluminium (alum) in enhancing antibodies production and transference to offspring. IgG and IgG1, IgG2a and IgG2b subclasses of antibodies in serum from immunized mice and controls were quantified and compared. Immunization by subcutaneous and intramuscular routes exhibited evidence of IgG, and both adjuvants promoted the production of IgG1 and IgG2b that were transferred to the offspring. These antibodies also showed specificity with the outer membrane vesicles from homologous strain and were capable to cross react with different strains. The use of DODAB-BF seems to enhance immune response on mothers and offspring and may have immunological advantages. [ABSTRACT FROM AUTHOR]

The article highlights a study on the preparation of monoclonal antibodies (Mab) against Neisseria (N.) meningitidis B. The native outer membrane complex (NOMC) of N. meningitidis B was used in a mice for immunization. The antibodies produced were FL24(PL)Br, a new serotype 24 class 3 antigen of nontypeable serogroup B strain and FL14(PL)Br, which was specific for the serotype 14 and reacted with the S3446 reference strain of N. meningitidis.