Gas exchange measurement as a non-destructive viability assay for frozen-thawed, winter-dormant apple buds.

Low temperature studies with winter-dormant buds are severely limited by the lack of a rapid, non-destructive assay for their viability. Investigations involving the winter harvest of ecodormant buds of woody subjects, including cryopreservation, are restricted if viability cannot be assessed until dormancy is broken. If post-treatment grafting indicates low survival of the harvested population then further collection and study has to be delayed until the next winter season. This study trials the use of a portable gas exchange system able to discriminate between live and dead buds rapidly, with the assay confirmed as non-destructive by subsequent micropropagation. Active respiration was recorded for 85% of a winter-dormant Malus domestica buds population that showed 91% viability when grafted (n = 45). Lethally stressed material gave no false positive results. When micropropagated after respiratory measurement, a population viability of 76% was recorded. There was a significant, positive correlation between respiration and fresh weight for buds of mass >10 mg, from a population with a mean fresh weight of 17 mg.

Preclinical immunogenicity study of trivalent meningococcal AWX-OMV vaccines for the African meningitis belt.

In the recent decade, epidemic meningitis in the African meningitis belt has mostly been caused by Neisseria meningitidis of serogroups A, W and X (MenA, MenW and MenX, respectively). There is at present no licensed vaccine available to prevent MenX meningococcal disease. To explore a trivalent MenAWX vaccine concept, we have studied the immunogenicity in mice of MenX outer membrane vesicles (X-OMV) or MenX polysaccharide (X-PS) when combined with a bivalent A-OMV and W-OMV (AW-OMV) vaccine previously shown to be highly immunogenic in mice. The vaccine antigens were produced from three representative wild type strains of MenA (ST-7), MenW (ST-11) and MenX (ST-751) isolated from patients in the African meningitis belt. Groups of mice were immunized with two doses of X-OMV or X-PS combined with the AW-OMV vaccine or as individual components. All vaccine preparations were adsorbed to Al(OH)3. Sera from immunized mice were tested by ELISA and immunoblotting. Functional antibody responses were measured as serum bactericidal activity (SBA) and opsonophagocytic activity (OPA). Immunization of mice with X-OMV, alone or in combination with AW-OMV induced high levels of anti-X OMV IgG. Moreover, X-OMV alone or in combination with the AW-OMV vaccine induced high SBA and OPA titers against the MenX target strain. X-PS alone was not immunogenic in mice; however, addition of the AW-OMV vaccine to X-PS increased the immunogenicity of X-PS. Both AWX vaccine formulations induced high levels of IgG against A- and W-OMV and high SBA titers against the MenA and MenW vaccine strains. These results suggest that a trivalent AWX vaccine, either as a combination of OMV or OMV with X-PS, could potentially prevent the majority of meningococcal disease in the meningitis belt.

Avidity of IgG antibodies against meningococcal serogroup a polysaccharide and correlations with bactericidal activity in sera from meningitis patients and controls from Ethiopia.

Meningococcal meningitis is a significant global health challenge, especially for sub-Saharan area: the African meningitis belt. Neisseria meningitidis of serogroup A (MenA) is responsible for the large number of epidemics that have been recorded in these countries. To determine the level of antibodies against meningococcal A polysaccharide (APS) that correlates with protection against MenA disease in the African meningitis belt, it may be important to consider antibody avidity along with quantity. In this study, two ELISA methods using the chaotropic agent ammonium thiocyanate were compared and employed to measure avidity indexes (AI) of IgG antibodies against APS in controls and in acute and convalescent sera from Ethiopian meningococcal patients. High statistical correlations between the AIs determined by the two methods were observed. The geometric mean AI (GMAI) increased with time from acute to convalescent sera indicating affinity maturation. GMAI was significantly higher in convalescent sera from the MenA patients and in sera from the controls than in acute sera from patients with meningococcal disease. A significant correlation between serum bactericidal activity titres (SBA) and concentration of IgG antibodies against APS was observed; however, our results did not indicate that determination of antibody avidities by the thiocyanate elution method gave a better correlation with SBA than anti-APS IgG concentrations determined by the standard ELISA method.

Preclinical immunogenicity and functional activity studies of an A+W meningococcal outer membrane vesicle (OMV) vaccine and comparisons with existing meningococcal conjugate- and polysaccharide vaccines.

Meningococci of serogroups A and W (MenA and MenW) are the main causes of epidemic bacterial meningitis outbreaks in sub-Saharan Africa. In this study we prepared a detergent extracted outer membrane vesicle (dOMV) vaccine from representative African MenA and MenW strains, and compared the immunogenicity of this vaccine with existing meningococcal conjugate and polysaccharide (PS) vaccines in mice. NMRI mice were immunized with preclinical batches of the A+W dOMV vaccine, or with commercially available vaccines; a MenA conjugate vaccine (MenAfriVac(®), Serum Institute of India), ACYW conjugate vaccine (Menveo(®), Novartis) or ACYW PS vaccine (Mencevax(®), GlaxoSmithKline). The mice received 2 doses of 1/10 or 1/50 of a human dose with a three week interval. Immune responses were tested in ELISA, serum bactericidal activity (SBA) and opsonophagocytic activity (OPA) assays. High levels of IgG antibodies against both A and W dOMV were detected in mice receiving the A+W dOMV vaccine. High SBA titers against both MenA and MenW vaccine strains were detected after only one dose of the A+W dOMV vaccine, and the titers were further increased after the second dose. The SBA and OPA titers in mice immunized with dOMV vaccine were significantly higher than in mice immunized with the ACYW-conjugate vaccine or the PS vaccine. Furthermore, the A+W dOMV vaccine was shown to induce SBA and OPA titers against MenA of the same magnitude as the titers induced by the A-conjugate vaccine. In conclusion, the A+W dOMV vaccine induced high levels of functional antibodies to both MenA and MenW strains, levels that were shown to be higher or equal to the levels induced by licensed meningococcal vaccines. Thus, an A+W dOMV vaccine could potentially serve as an alternative or a supplement to existing conjugate and PS vaccines in the African meningitis belt.

An outer membrane vesicle vaccine for prevention of serogroup A and W-135 meningococcal disease in the African meningitis belt.

The bacterium Neisseria meningitidis of serogroups A and W-135 has in the recent decade caused most of the cases of meningococcal meningitis in the African meningitis belt, and there is currently no efficient and affordable vaccine available demonstrated to protect against both these serogroups. Previously, deoxycholate-extracted outer membrane vesicle (OMV) vaccines against serogroup B meningococci have been shown to be safe and induce protection in humans in clonal outbreaks. The serogroup A and W-135 strains isolated from meningitis belt epidemics demonstrate strikingly limited variation in major surface-exposed protein structures. We have here investigated whether the OMV vaccine strategy also can be applied to prevent both serogroups A and W-135 meningococcal disease. A novel vaccine combining OMV extracted from recent African serogroup A and W-135 strains and adsorbed to aluminium hydroxide was developed and its antigenic characteristics and immunogenicity were studied in mice. The specificity of the antibody responses was analysed by immunoblotting and serum bactericidal activity (SBA) assays. Moreover, the bivalent A+W-135 vaccine was compared with monovalent A and W-135 OMV vaccines. The bivalent OMV vaccine was able to induce similar SBA titres as the monovalent A or W-135 OMV towards both serogroups. High SBA titres were also observed against a meningococcal serogroup C strain. These results show that subcapsular antigens may be of importance when developing broadly protective and affordable vaccines for the meningitis belt.

Avidity of serogroup A meningococcal IgG antibodies after immunization with different doses of a tetravalent A/C/Y/W135 polysaccharide vaccine.

In the absence of an affordable conjugate meningococcal vaccine, mass vaccination campaigns with polysaccharide vaccines are the means to control meningitis epidemics in sub-Saharan Africa. Facing global vaccine shortage, the use of reduced doses, which have been shown to be protective by serum bactericidal activity, can save many lives. In this study, we investigated the antibody responses and avidity of IgG antibodies evoked against the serogroup A capsule of Neisseria meningitidis by different doses of an A/C/Y/W135 polysaccharide vaccine. Volunteers in Uganda were vaccinated with 1/10, 1/5 or a full dose (50 µg) and revaccinated with a full dose after 1 year. Specific IgG geometric mean concentrations and geometric mean avidity indices (GMAI) were determined by a modified enzyme-linked immunosorbent assay (ELISA) using thiocyanate as a chaotropic agent. After vaccination with 1/10 or 1/5 doses, the GMAI increased from 1 month to 1 year. One year following the initial dose, the GMAI levels were higher in the arm receiving reduced doses than for the arm receiving a full dose. Following the second full dose, avidity indices equalized at approximately the same level in the three arms. Although there are practical challenges to the use of reduced doses in the field, our findings suggest that reduced doses of polysaccharide vaccine are able to elicit antibodies of as good avidity against serogroup A polysaccharide as a full dose.

Leaf physiological versus morphological acclimation to high-light exposure at different stages of foliar development in oak.

We investigated light acclimation in seedlings of the temperate oak Quercus petraea (Matt.) Liebl. and the co-occurring sub-Mediterranean oak Quercus pyrenaica Willd. Seedlings were raised in a greenhouse for 1 year in either 70 (HL) or 5.3% (LL) of ambient irradiance of full sunlight, and, in the following year, subsets of the LL-grown seedlings were transferred to HL either before leaf flushing (LL-HLBF plants) or after full leaf expansion (LL-HLAF plants). Gas exchange, chlorophyll a fluorescence, nitrogen fractions in photosynthetic components and leaf anatomy were examined in leaves of all seedlings 5 months after plants were moved from LL to HL. Differences between species in the acclimation of LL-grown plants to HL were minor. For LL-grown plants in HL, area-based photosynthetic capacity, maximum rate of carboxylation, maximum rate of electron transport and the effective photochemical quantum yield of photosystem II were comparable to those for plants grown solely in HL. A rapid change in nitrogen distribution among photosynthetic components was observed in LL-HLAF plants, which had the highest photosynthetic nitrogen-use efficiency. Increases in mesophyll thickness and dry mass per unit area governed leaf acclimation in LL-HLBF plants, which tended to have less nitrogen in photosynthetic components and a lower assimilation potential per unit of leaf mass or nitrogen than LL-HLAF plants. The data indicate that the phenological state of seedlings modified the acclimatory response of leaf attributes to increased irradiance. Morphological adaptation of leaves of LL-HLBF plants enhanced photosynthetic capacity per unit leaf area, but not per unit leaf dry mass, whereas substantial redistribution of nitrogen among photosynthetic components in leaves of LL-HLAF plants enhanced both mass- and area-based photosynthetic capacity.

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.

Safety and immunogenicity of New Zealand strain meningococcal serogroup B OMV vaccine in healthy adults: beginning of epidemic control.

As the first step towards control of a strain specific epidemic of meningococcal disease in New Zealand (NZ), this study, an observer-blind, randomised controlled trial in 75 healthy adults, evaluated safety and immunogenicity of two different dosages of a meningococcal group B vaccine administered in a three dose regime. The "tailor-made" outer membrane vesicle (OMV) vaccine (candidate vaccine) developed using a New Zealand meningococcal group B strain (B:4:P1.7b,4) was well tolerated with no vaccine related serious adverse events. Similar local and systemic reactions were observed in those receiving the New Zealand candidate vaccine and the control parent Norwegian vaccine (MenBvac). A four-fold rise in serum bactericidal antibodies (SBAb) against the vaccine strain 4-6 weeks after the third vaccination was achieved in 100% of New Zealand candidate vaccine 2,519 microg participants and in 87% of 50 microg participants. The safety and immunogenicity profile observed in this study of healthy adults enabled studies in children to be initiated using 25 microg dosage.

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.

Serum bactericidal activity correlates with the vaccine efficacy of outer membrane vesicle vaccines against Neisseria meningitidis serogroup B disease.

For evaluation of serum bactericidal activity (SBA) as surrogate for the efficacy of outer membrane vesicle (OMV) vaccines against Neisseria meningitidis serogroup B disease, we have reanalyzed data from a randomized double blind placebo-controlled efficacy trial involving 172000 secondary school students (aged 13-14 years) in Norway (1988-1991). A cohort of the efficacy trial consisting of 880 individuals was selected for immunogenicity studies. An efficacy of 87% was calculated for a 10-month observation period. However, after an observation period of 29 months, the estimated efficacy against group B disease induced by vaccination was 57%. The immunogenicity study showed that the SBA geometric mean titer (GMT) for the vaccinees was 2.4 before vaccination and 19.0 six weeks after the second vaccine dose. One year after vaccination the GMT was reduced to 2.8. A separate three-dose study with 304 adolescents showed that with a third dose at 10 months after the second dose (i.e. when cases of disease started to appear) a strong booster response was induced. Ten months after the second dose the SBA was reduced to near pre-immunization level. Following the third dose the SBA geometric mean titer of 2.7 increased to 62.3. One year after the third dose, the GMT was markedly higher than 6 weeks after the second dose (12.6 versus 8.8). Thus, protection after vaccination corresponds with the level of SBA. In order to reach lasting protective levels of SBA in a population, three vaccine doses are probably required. Measurements of SBA are likely to be useful for evaluating various upcoming formulations and improvements of immunization regimens for OMV vaccines.

Analysis of the expression of the putatively virulence-associated neisserial protein RmpM (class 4) in commensal Neisseria and Moraxella catarrhalis strains.

The RmpM protein has been reported to be present only in pathogenic Neisseria species. In the present study we demonstrate that this protein is also present at least in N. lactamica and N. sicca strains. The N. lactamica protein reacts with a RmpM-specific monoclonal antibody (185,H-8), having a molecular mass ( approximately 31 kDa) slightly lower than that of the meningococcal RmpM, and mouse antibodies from sera against outer membrane vesicles from both N. lactamica and N. sicca strains cross-react with the meningococcal RmpM. PCR and hybridization experiments with a complete rmpM probe agree with the immunodetection experiments. Our results strongly suggest that the meningococcal RmpM should not be considered a virulence marker, and the presence of this protein in the commensal species agrees with its role as a structural protein, proposed for the RmpM, which should be considerably conserved in the Neisseria species.

PorB3 outer membrane protein on Neisseria meningitidis is poorly accessible for antibody binding on live bacteria.

It is reported here that the PorB3 porin proteins of serotype 4 and 15 are poorly accessible for antibody binding on live Neisseria meningitidis bacteria, whereas the allelic PorB2 and the PorA outer membrane protein appear to be highly accessible. This was revealed by flow cytometry analysis using several mouse monoclonal antibodies (mAbs) as well as PorB3 specific antibodies isolated from post vaccination and patient sera. However, strong antibody binding to the PorB3 protein was observed after killing the bacteria with ethanol. The reason for the lack of epitope exposure could be a shielding effect of the carbohydrate chains of lipopolysaccharides (LPS) possibly combined with short extra-cellular loops in the PorB3 protein. The findings indicate that the PorB3 protein is not an optimal target for protective antibodies induced by vaccination.

Light acclimation maintains the redox state of the PS II electron acceptor Q(A) within a narrow range over a broad range of light intensities.

Chrysanthemum inducum-hybrid 'Coral Charm', Hibiscus rosa-sinensis L. 'Cairo Red' and Spathiphyllum wallisii Regel 'Petit' were grown in natural light in a greenhouse at three levels of irradiance using permanent shade screens. Light acclimation of photosynthesis was characterized using modulated chlorophyll a fluorescence of intact leaves. A close correlation was found between the degree of reduction of the primary electron acceptor Q(A) of Photosystem II (PS II) approximated as the fluorescence parameter 1-q(P), and light acclimation. The action range of 1-q(P) was 0-0.4 from darkness to full irradiance around noon, within the respective light treatments in the greenhouse, indicating that most PS II reaction centres were kept open. In general, the index for electron transport (ETR) measured by chlorophyll fluorescence was higher for high-light (HL) than intermediate-(IL) and low-light (LL) grown plants. However, HL Chrysanthemum showed 40% higher ETR than HL Hibiscus at light saturation, despite identical redox states of Q(A). The light acclimation of the non-radiative dissipation of excess energy in the antenna, NPQ, varied considerably between the species. However, when normalized against q(P), a strong negative correlation was found between thermal dissipation and ETR measured by chlorophyll fluorescence. To be able to accommodate a high flux of electrons through PS II, the plants with the highest light-saturated ETR had the lowest NPQ/q(P). The possibility of using chlorophyll fluorescence for quantification of the energy balance between energy input and utilization in PS II in intact leaves is discussed.

Outer membrane protein vesicle vaccines for meningococcal disease.

Alternative strategies exist for prevention of group B Neisseria meningitidis (meningococcal) disease through vaccination (see Chapters 5 , 8 , 13 , 14 in this volume). However, the most promising approach to date has been the use of outer-membrane vesicle (OMV) vaccines for induction of bactericidal antibodies against cell-surface outer-membrane proteins (OMPs).

Determination of antibody responses to meningococcal antigens by ELISA.

Enzyme-linked immunosorbent assay (ELISA, EIA) is a highly versatile and sensitive technique that can be used for quantitative as well as qualitative determination of almost any antigen or antibody. Reagents are stable, non-radioactive and, in most cases, commercially available. Owing to the simplicity and versatility of the method, ELISA represents probably one of the most used methods for studying antibody responses and antibody levels. Since Engvall and Perlman's first paper describing the ELISA in 1971 (1), almost all laboratories working in serology or immunology have designed their own assays with different protocols for coating with antigens, incubation conditions, detecting systems, and ways of reporting of the results. In most cases, there is no need for strict interlaboratory standardization of ELISAs and each laboratory will develop a system that suits their needs. However, for some ELISAs, e.g., used in diagnostic laboratories and in vaccine trials, standardization is important, and this is considered in "Meningococcal Disease" Edited by AJ Pollard and MCJ Maiden, (1a).

[Meningococcal disease in Africa--epidemiology and prevention]. / Meningokokksjukdom i Afrika--epidemiologi og førebyggjing.

Neisseria meningitidis is one of the most common causes of purulent meningitis all over the world. Large epidemics caused by meningococci have spread during the last decade throughout vast areas of Africa, also outside the region referred to as the classic "Meningitis Belt". Globally, this organism each year causes about 300,000 cases and 30,000 deaths; most of these are children. Meningococci of serogroup A cause a major part of these epidemics, and a remarkable feature of the epidemical situation is that the bacteria differ very little in antigenic properties as they belong to the same clonal group of meningococci. Immunization with safe and effective vaccines is the most efficient way of combatting these epidemics. The currently available polysaccharide vaccines against serogroup. A meningococcal disease do not induce long-term immunological memory and do not provide adequate protection of children below two years of age. There is an urgent need for a vaccine that induces long-term immunological memory in all age groups, so it can be included in the routine vaccination program. In contrast to serogroup C, the development of conjugate vaccines against serogroup A meningococcal disease has not yielded the positive results hoped for. The development of alternative protein-based vaccines therefore needs to be intensified.

Functional activities and immunoglobulin variable regions of human and murine monoclonal antibodies specific for the P1.7 PorA protein loop of Neisseria meningitidis.

The meningococcal PorA protein is considered a promising vaccine candidate. Although much is understood regarding the structure of PorA proteins, little is known about the structure-function relationships of PorA antibodies. The aim of this study was to compare the functional and molecular characteristics of a human monoclonal antibody (MAb) and three murine MAbs specific for the PorA P1.7 serosubtype. Murine MAbs 207,B-4 (immunoglobulin G2a [IgG2a]) and MN14C11.6 (IgG2a) were both bactericidal and opsonophagocytic for P1.7-expressing meningococci, whereas human MAb SS269 (IgG3) and murine MAb 208,D-5 (IgA) initiated neither effector function. Epitope mapping with synthetic peptides revealed that MAbs 207,B-4 and 208,D-5 recognized the sequence ASGQ, which is the same specificity motif that a previous study had established for SS269 and MN14C11.6. Nucleotide and amino acid sequence analyses of the variable regions of the four MAbs showed that the SS269 V(H) region belonged to the VH3 family and was approximately 70% homologous to those of the murine MAbs which were all from the 7183 family, whereas the SS269 V(L) region belonged to the Vlambda1-b family and was less than 40% homologous to those of the murine MAbs which were all members of the Vkappa1 family. The Fab fragment of SS269 was cloned and expressed in Escherichia coli and was shown by enzyme-linked immunosorbent assay analyses to bind as well as intact SS269 MAb to P1.7,16 serosubtype group B strain 44/76. We conclude that distinct differences exist in the effector function activities and variable region gene sequences of human and murine P1.7-specific MAbs despite their recognition of similar epitopes.

Cellular activating properties and morphology of membrane-bound and purified meningococcal lipopolysaccharide.

Neisseria meningitidis, the cause of epidemic meningitis and acute lethal sepsis, synthesizes surplus lipopolysaccharides (LPSs) during growth, which are released as outer membrane vesicles (OMV) or "blebs". Meningococcal disease severity is related to plasma LPS levels. We have compared the biological activities of native outer membrane vesicles (nOMV) to those of purified Nm-LPS (Nm-LPS) and LPS-depleted OMV (dOMV) prepared from N. meningitidis. The LPS content of nOMV was determined spectrophotometrically by quantifying KDO and by silver-stained SDS-PAGE gels. The morphology of the preparations was studied by transmission electron microscopy. The Limulus amoebocyte lysate (LAL) assay was used to quantify LPS in the plasma solutions. The preparations were diluted in endotoxin-free heparin plasma to equal amounts of LPS (w/w) in the range 50-5000 pg/ml. The biological reactivity was tested by: (i) a monocyte target-assay (monocyte purity > or =96%); and (ii) a whole blood model, measuring the secretion of TNF-alpha and IL-6 induction of procoagulant activity in monocytes (PCA). In both models, nOMV induced dose-dependent cell responses (TNF-alpha, IL-6, PCA) similar to purified Nm-LPS, whereas dOMV induced minimal responses. However, LAL activity was significantly higher for nOMV than for purified Nm-LPS and dOMV. The cellular responses of purified Nm-LPS and nOMV were reduced (>95%) by a specific anti-CD14-antibody.

The infant rat model adapted to evaluate human sera for protective immunity to group B meningococci.

The infant rat infection model previously developed to evaluate protective ability of passively administered murine antibodies to group B meningococcal (MenB) surface antigens was adapted for human sera. Several challenge doses were tested, aiming at sensitive detection of protection with little interassay variability. Doses of 10(5) and 10(6) colony forming units of strain IH5341 (MenB:15:P1.7,16) injected intraperitoneally gave consistently high levels of bacteremia and meningitis developed in 6 h in 50-100% of the pups. A monoclonal antibody mAb735 to the MenB capsule, injected 1-2 h before bacterial challenge, gave full protection at a dose of 2 microg/pup. Sera from adult volunteers immunized with a MenB outer membrane vesicle vaccine reproducibly reduced bacterial counts in the blood and cerebrospinal fluid, whereas a normal human serum, lacking bactericidal and opsonophagocidal activity, was unprotective.