[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: A novel multicomponent vaccine against meningococcal capsular group B (MenB) disease contains four major components: factor-H-binding protein, neisserial heparin binding antigen, neisserial adhesin A, and outer-membrane vesicles derived from the strain NZ98/254. Because the public health effect of the vaccine, 4CMenB (Novartis Vaccines and Diagnostics, Siena, Italy), is unclear, we assessed the predicted strain coverage in Europe. METHODS: We assessed invasive MenB strains isolated mainly in the most recent full epidemiological year in England and Wales, France, Germany, Italy, and Norway. Meningococcal antigen typing system (MATS) results were linked to multilocus sequence typing and antigen sequence data. To investigate whether generalisation of coverage applied to the rest of Europe, we also assessed isolates from the Czech Republic and Spain. FINDINGS: 1052 strains collected from July, 2007, to June, 2008, were assessed from England and Wales, France, Germany, Italy, and Norway. All MenB strains contained at least one gene encoding a major antigen in the vaccine. MATS predicted that 78% of all MenB strains would be killed by postvaccination sera (95% CI 63-90, range of point estimates 73-87% in individual country panels). Half of all strains and 64% of covered strains could be targeted by bactericidal antibodies against more than one vaccine antigen. Results for the 108 isolates from the Czech Republic and 300 from Spain were consistent with those for the other countries. INTERPRETATION: MATS analysis showed that a multicomponent vaccine could protect against a substantial proportion of invasive MenB strains isolated in Europe. Monitoring of antigen expression, however, will be needed in the future. FUNDING: Novartis Vaccines and Diagnostics.
[Show abstract][Hide abstract] ABSTRACT: The NadA adhesin is a major component of 4CMenB, a novel vaccine to prevent meningococcus B (MenB) infection. Under in vitro growth conditions nadA is repressed by the regulator NadR and poorly expressed, resulting in inefficient killing of MenB strains by anti-NadA antibodies. Interestingly, sera from children infected with strains that express low levels of NadA in laboratory growth, nevertheless recognize the NadA antigen, suggesting that during infection NadA expression may be different from that observed in vitro. In a strain panel covering a range of NadA levels, repression was relieved through deleting nadR. All nadR(-) strains expressed high levels of NadA and were efficiently killed by sera from subjects immunized with 4CMenB. A selected MenB strain, NGP165, mismatched for other vaccine antigens, is not killed by sera from immunized infants when grown in vitro. However, in an in vivo passive protection model the same sera effectively protected infant rats from bacteremia with NGP165. Furthermore, we identify a novel HPA derivative, reported by others to be produced during inflammation, which induces expression of NadA in vitro leading to efficient antibody-mediated killing. Finally, using bioluminescent reporters, nadA expression in the infant rat model is induced in vivo at three hours post infection. Our results suggest that during infectious disease, NadR repression is alleviated due to niche-specific signals, resulting in high levels of NadA expression from any nadA(+) strain and therefore efficient killing by anti-NadA antibodies elicited by the 4CMenB vaccine.
Infection and immunity 12/2012; 81(2). DOI:10.1128/IAI.01085-12 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The meningococcal antigen typing system (MATS) sandwich enzyme-linked immunosorbent assay (ELISA) was designed to measure the immunologic cross-reactivity and quantity of antigens in target strains of a pathogen. It was first used to measure the factor H-binding protein (fHbp), neisserial adhesin A (NadA), and neisserial heparin-binding antigen (NHBA) content of serogroup B meningococcal (MenB) isolates relative to a reference strain, or "relative potency" (RP). With the PorA genotype, the RPs were then used to assess strain coverage by 4CMenB, a multicomponent MenB vaccine. In preliminary studies, MATS accurately predicted killing in the serum bactericidal assay using human complement, an accepted correlate of protection for meningococcal vaccines. A study across seven laboratories assessed the reproducibility of RPs for fHbp, NadA, and NHBA and established qualification parameters for new laboratories. RPs were determined in replicate for 17 MenB reference strains at laboratories A to G. The reproducibility of RPs among laboratories and against consensus values across laboratories was evaluated using a mixed-model analysis of variance. Interlaboratory agreement was very good; the Pearson correlation coefficients, coefficients of accuracy, and concordance correlation coefficients exceeded 99%. The summary measures of reproducibility, expressed as between-laboratory coefficients of variation, were 7.85% (fHbp), 16.51% (NadA), and 12.60% (NHBA). The overall within-laboratory measures of variation adjusted for strain and laboratory were 19.8% (fHbp), 28.8% (NHBA), and 38.3% (NadA). The MATS ELISA was successfully transferred to six laboratories, and a further laboratory was successfully qualified.
[Show abstract][Hide abstract] ABSTRACT: Current concepts of vaccines against serogroup B meningococci (MenB) are mainly based on genetically variable protein antigens. Vaccine efficacy studies for meningococcal disease in developed countries are hampered by the low incidence. Licensure must therefore exclusively rely on clinical trials and laboratory investigation of meningococcal strains. In contrast to capsule polysaccharide vaccines, serum bactericidal assays for technical reasons are limited in their practicability as the surrogate of protection provided by MenB vaccines. Therefore, assays are required for reliable laboratory based assessment of expression of those specific antigen variants that are predicted to be targeted by bactericidal antibodies elicited by the vaccine. The MATS ELISA (MATS, meningococcal antigen typing system) reported recently is an example for such an assay. The paper discusses the pre- and post-licensure application of MATS, the role of reference laboratories, concepts of sustained provision of the assay, external quality assessment, and laboratory twinning.
[Show abstract][Hide abstract] ABSTRACT: Complement-mediated bactericidal activity has long been regarded as the serological correlate of protective immunity against Neisseria meningitidis. This was affirmed in 2005 at a WHO-sponsored meningococcal serology standardization workshop. The assay currently employed by most laboratories involves determining surviving bacterial colony counts on agar as a readout which is labor-intensive, time-consuming, and not amendable to rapid data analysis for clinical trials. Consequently, there is an acute need to develop a sensitive, high-throughput bactericidal assay to enable a rapid and robust assessment of the effectiveness of vaccine candidates. To this end, we have developed an automated, kinetic assay based on the fluorescent respiration product of resazurin which reduces assay volume, shortens assay time, and facilitates automation of data analysis. We demonstrate proof of concept for applicability of this high-throughput system with multiple meningococcal strains and utilizing different lots of human complement. The assay is robust and highly reproducible. Titers obtained by the fluorescence readout method are strongly correlated with the data obtained using the conventional, agar plate-based assay. These results demonstrate that the detection of bacteria that have survived the bactericidal reaction by measuring metabolic activity using a fluorescent dye as an alternative readout is a promising approach for the development of a high-throughput bactericidal assay.
[Show abstract][Hide abstract] ABSTRACT: We previously investigated immunogenicity of meningococcal native outer membrane vesicle (NOMV) vaccines prepared from recombinant strains with attenuated endotoxin (ΔLpxL1) and over-expressed factor H binding protein (fHbp) in a mouse model. The vaccines elicited broad serum bactericidal antibody responses. While human toll-like receptor 4 (TLR-4) is mainly stimulated by wildtype meningococcal endotoxin, mouse TLR-4 is stimulated by both the wildtype and mutant endotoxin. An adjuvant effect in mice of the mutant endotoxin would be expected to be much less in humans, and may have contributed to the broad mouse bactericidal responses. Here we show that as previously reported for humans, rhesus primate peripheral blood mononuclear cells incubated with a NOMV vaccine from ΔLpxL1 recombinant strains had lower proinflammatory cytokine responses than with a control wildtype NOMV vaccine. The cytokine responses to the mutant vaccine were similar to those elicited by a detergent-treated, wildtype outer membrane vesicle vaccine that had been safely administered to humans. Monkeys (N=4) were immunized beginning at ages 2-3 months with three doses of a NOMV vaccine prepared from ΔLpxL1 recombinant strains with over-expressed fHbp in the variant 1 and 2 groups. The mutant NOMV vaccine elicited serum bactericidal titers≥1:4 against all 10 genetically diverse strains tested, including 9 with heterologous PorA to those in the vaccine. Negative-control animals had serum bactericidal titers<1:4. Thus, the mutant NOMV vaccine elicited broadly protective serum antibodies in a non-human infant primate model that is more relevant for predicting human antibody responses than mice.
[Show abstract][Hide abstract] ABSTRACT: A key missing element in the development of a successful human immunodeficiency virus (HIV) vaccine is an immunogen that can generate broadly cross-neutralizing antibodies against primary isolates of the virus.
This phase 1 clinical trial employed a DNA prime and subunit envelope protein boost in an attempt to generate cellular and humoral immune responses that might be desirable in a protective HIV vaccine. Priming was performed via intramuscular injection with gag and env DNA adsorbed to polylactide coglycolide microspheres, followed by boosting with a recombinant trimeric envelope (Env) glycoprotein delivered in MF59 adjuvant.
The DNA prime and protein boost were generally safe and well-tolerated. Env-specific CD4(+) cellular responses were generated that were predominantly detected after Env protein boosting. Neutralizing antibody responses against the homologous SF162 viral isolate were remarkably strong and were present in the majority of vaccine recipients, including a strong response against CD4-induced epitopes on gp120. Despite the promising potency of this vaccine approach, neutralization breadth against heterologous tier 2 strains of HIV-1 was minimal.
Potent neutralization against neutralization-sensitive strains of HIV is achievable in humans through a DNA prime, recombinant oligomeric Env protein boost regimen. Eliciting substantial breadth of neutralization remains an elusive goal.
The Journal of Infectious Diseases 04/2011; 203(8):1165-73. DOI:10.1093/infdis/jiq175 · 6.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Factor H binding protein (fHbp), one of the main antigens of new vaccines against serogroup B meningococcus, varies in amino acid sequence and level of expression in different clinical isolates. To evaluate the contribution of amino acid sequence variability to vaccine coverage, we constructed a strain that is susceptible to bactericidal killing only by anti-fHbp antibodies and engineered it to express equal levels of 10 different fHbp sub-variants from a constitutive promoter. Testing of these isogenic strains showed that sera from mice or adult volunteers vaccinated with fHbp variant 1.1 were bactericidal against all sub-variants 1 sequences, however the titer against the most distant sequences were several times lower. Sera from vaccinated infants were more susceptible to amino acid variations and they had lower or no bactericidal activity against the distant sub-variants 1 sequences in comparison with sera from adults given the same vaccines. The low coverage provided by fHbp could be overcome using a multicomponent vaccine. We conclude that fHbp is a very important antigen that induces bactericidal antibodies in animals, adults and infants. However, given its high variability of sequence and expression level, it is unlikely that fHbp alone can provide good protection in infants against the distant amino acid sequence variants and therefore multicomponent vaccines inducing protective immunity also against other antigens are more likely to induce a broad protective immunity in all age groups.
[Show abstract][Hide abstract] ABSTRACT: A unique multicomponent vaccine against serogroup B meningococci incorporates the novel genome-derived proteins fHbp, NHBA, and NadA that may vary in sequence and level of expression. Measuring the effectiveness of such vaccines, using the accepted correlate of protection against invasive meningococcal disease, could require performing the serum bactericidal assay (SBA) against many diverse strains for each geographic region. This approach is impractical, especially for infants, where serum volumes are very limited. To address this, we developed the meningococcal antigen typing system (MATS) by combining a unique vaccine antigen-specific ELISA, which detects qualitative and quantitative differences in antigens, with PorA genotyping information. The ELISA correlates with killing of strains by SBA and measures both immunologic cross-reactivity and quantity of the antigens NHBA, NadA, and fHbp. We found that strains exceeding a threshold value in the ELISA for any of the three vaccine antigens had ≥80% probability of being killed by immune serum in the SBA. Strains positive for two or more antigens had a 96% probability of being killed. Inclusion of multiple different antigens in the vaccine improves breadth of coverage and prevents loss of coverage if one antigen mutates or is lost. The finding that a simple and high-throughput assay correlates with bactericidal activity is a milestone in meningococcal vaccine development. This assay allows typing of large panels of strains and prediction of coverage of protein-based meningococcal vaccines. Similar assays may be used for protein-based vaccines against other bacteria.
Proceedings of the National Academy of Sciences 10/2010; 107(45):19490-5. DOI:10.1073/pnas.1013758107 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Serum bactericidal activity using human complement is the basis for established correlates of protection against invasive meningococcal disease. During the development of multicomponent protein-based vaccines against meningococcus B, it is necessary to measure antigen-specific bactericidal responses. This is not straightforward because each strain may be killed by antibodies to multiple antigens. We characterized a large panel of strains and, using a competitive inhibition SBA, we identified four strains that are each specifically killed by bactericidal antibodies to one of the major vaccine components. These strains provide a straightforward approach to demonstrate protective responses to each component of the vaccine and demonstrate that each of the antigens in the vaccine is sufficient to provide a potentially protective level of bactericidal activity.
[Show abstract][Hide abstract] ABSTRACT: We have previously shown that rhesus macaques were partially protected against high-dose intravenous challenge with simian-human immunodeficiency virus SHIV(SF162P4) following sequential immunization with alphavirus replicon particles (VRP) of a chimeric recombinant VEE/SIN alphavirus (derived from Venezuelan equine encephalitis virus [VEE] and the Sindbis virus [SIN]) encoding human immunodeficiency virus type 1 HIV-1(SF162) gp140DeltaV2 envelope (Env) and trimeric Env protein in MF59 adjuvant (R. Xu, I. K. Srivastava, C. E. Greer, I. Zarkikh, Z. Kraft, L. Kuller, J. M. Polo, S. W. Barnett, and L. Stamatatos, AIDS Res. Hum. Retroviruses 22:1022-1030, 2006). The protection did not require T-cell immune responses directed toward simian immunodeficiency virus (SIV) Gag. We extend those findings here to demonstrate antibody-mediated protection against mucosal challenge in macaques using prime-boost regimens incorporating both intramuscular and mucosal routes of delivery. The macaques in the vaccination groups were primed with VRP and then boosted with Env protein in MF59 adjuvant, or they were given VRP intramuscular immunizations alone and then challenged with SHIV(SF162P4) (intrarectal challenge). The results demonstrated that these vaccines were able to effectively protect the macaques to different degrees against subsequent mucosal SHIV challenge, but most noteworthy, all macaques that received the intramuscular VRP prime plus Env protein boost were completely protected. A statistically significant association was observed between the titer of virus neutralizing and binding antibodies as well as the avidity of anti-Env antibodies measured prechallenge and protection from infection. These results highlight the merit of the alphavirus replicon vector prime plus Env protein boost vaccine approach for the induction of protective antibody responses and are of particular relevance to advancing our understanding of the potential correlates of immune protection against HIV infection at a relevant mucosal portal of entry.
Journal of Virology 06/2010; 84(12):5975-85. DOI:10.1128/JVI.02533-09 · 4.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: GNA2132 is a Neisseria meningitidis antigen of unknown function, discovered by reverse vaccinology, which has been shown to induce bactericidal antibodies in animal models. Here we show that this antigen induces protective immunity in humans and it is recognized by sera of patients after meningococcal disease. The protein binds heparin in vitro through an Arg-rich region and this property correlates with increased survival of the unencapsulated bacterium in human serum. Furthermore, two proteases, the meningococcal NalP and human lactoferrin, cleave the protein upstream and downstream from the Arg-rich region, respectively. We conclude that GNA2132 is an important protective antigen of N. meningitidis and we propose to rename it, Neisserial Heparin Binding Antigen (NHBA).
Proceedings of the National Academy of Sciences 02/2010; 107(8):3770-5. DOI:10.1073/pnas.0915162107 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The standard serological methods present limitations for the measurement of immunity against H5N1 influenza strains. The hemagglutination inhibition (HI) assay lacks sensitivity and requires standardization, while the viral micro-neutralization (MN) assay needs handling of live virus. We produced pseudoparticles expressing hemagglutinin from clades 1 or 2 H5N1 in order to measure neutralizing antibodies in human sera after prime-boost vaccination with plain or MF59-adjuvanted H5N1 clade 1 subunit vaccines. Titers measured by pseudoparticle neutralization (PPN) assay significantly correlated with those measured by HI, single radial haemolysis or MN, with a PPN titer of 1:357 corresponding to an MN titer of 1:80. Notably, results from the PPN assay, confirm that MF59-H5N1 vaccine induces potent and long-lasting neutralizing antibody responses not only against the vaccine strain, but also against several heterologous clade 2 strains. Overall, the PPN assay represents a valid alternative to conventional serological methods for the evaluation of H5N1 vaccine immunogenicity.
[Show abstract][Hide abstract] ABSTRACT: Pandemic H1N1 influenza vaccine antigens are currently being manufactured. The MF(59) adjuvant has an established safety profile in humans and a proven ability to increase responses to some influenza vaccines in humans. To inform initial decisions on the use of these vaccine components to protect human populations, we have immunized mice with MF(59)-adjuvanted or non-adjuvanted pandemic influenza vaccine. Immunizing unprimed mice with a single dose of MF(59)-adjuvanted vaccine elicits functional antibody titers equivalent to those associated with protection of humans from seasonal influenza. Without adjuvant, two doses are required for a robust antibody response. Unadjuvanted vaccines with 0.5 and 1 microgram of antigen elicit equivalent titers. These data support including MF(59) in pandemic flu vaccines to rapidly protect young adults and children, who may have little or no previous exposure to influenza infection or immunization.
[Show abstract][Hide abstract] ABSTRACT: The induction of resistance by immune selective pressure to bactericidal antibodies from humans immunized with Novartis recombinant meningococcal group B vaccines was assessed. Serum bactericidal antibody titers against selected bacteria were within assay variability through a selection event frequency of 1 in 10(-5). No change in antigen expression was observed by Western blotting.
[Show abstract][Hide abstract] ABSTRACT: GNA1870, also named factor H-binding protein (fHbp) or rLP-2086, is a genome-derived antigen and one of the components of a rationally designed vaccine against Neisseria meningitidis serogroup B, which has entered phase III clinical trials. It has been classified into three main non-cross-protective variant groups. GNA1870 has also been termed fHbp because of its ability to bind factor H, a key regulatory component of the alternative complement pathway. fHbp is important for survival in human blood, human sera, and in presence of antimicrobial peptides, independently of its expression level. All these properties make fHbp a unique vaccine antigen.
[Show abstract][Hide abstract] ABSTRACT: The immunologic and virologic outcome of therapeutic DNA-vaccines administered during antiretroviral therapy (ART) using electroporation with or without (interleukin) IL-2 treatment was evaluated in the SIVmac239/macaque model. Rhesus macaques inoculated with pathogenic SIVmac239 were treated with ART [(R(-9-(2-phosphonomethoxypropyl) adenine) (PMPA), FTC, Zerit] from weeks 13 to 41 postinfection (wpi). Group 1 (n = 7) received ART only, groups 2 and 3 (each n = 6) additionally received SIVmac239-derived gp140Env, GagPol, and TatRevNef plasmids by in vivo electroporation at 22, 26, 30, and 34 wpi, and group 3 also IL-2 for 14 days after each vaccination. Endpoints evaluated were viral load, Gag(181189)-specific CD8+ T-cell responses in MamuA01+ animals, lymphoproliferative responses, and CD4 T-cell counts. Viremia in all animals dropped below 200 RNA copies/ml during ART. Frequencies of Gag(181189)-specific CD8+ T cells prior to ART were detectable in all three groups (1.27-3.01%) and increased significantly (p < 0.01) postvaccination with maximum responses after the fourth immunization (0.2% versus 3.49-7.15%). Gag(181189)-specific CD8+ T-cell frequencies increased post-ART cessation in all groups and remained at significantly higher levels (p < 0.001) until the end of the study (75 wpi) in both groups of vaccinated animals. Lymphoproliferative responses were detected against Gag in a limited number of animals after vaccination and post-ART. However, plasma RNA viral loads rebounded after ART termination to similar levels in all three groups, but remained below 10(5) copies/ml until the end of the study, which could be a late effect of the triple drug therapy.
AIDS research and human retroviruses 07/2008; 24(8):1103-16. DOI:10.1089/aid.2008.0055 · 2.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vaccination strategies that can block or limit heterosexual human immunodeficiency virus (HIV) transmissions to local and systemic tissues are the goal of much research effort. Herein, in a mouse model, we aimed to determine whether the enhancement of antibody responses through mucosal and systemic immunizations, previously observed with protein-based vaccines, applies to immunizations with DNA- or RNA-based vectors. Intranasal (i.n.) followed by intramuscular (i.m.) immunizations (i.n./i.m.) with polylactide-coglycolide (PLG)-DNA microparticles encoding HIV-gag (PLG-DNA-gag) significantly enhanced serum antibody responses, compared with i.m., i.n. or i.m. followed by i.n. (i.m./i.n.) immunizations. Moreover, while i.n./i.m., i.n. or i.m./i.n. immunizations with PLG-DNA-gag resulted in genital tract antibody responses, i.m. immunizations alone failed to do so. Importantly, beta7-deficient mice developed local and systemic antibody responses following i.n./i.m. immunization, or immunization via any other route, similar to those of wild-type mice. To compare the DNA with an RNA delivery system, immunizations were performed with VEE/SIN-gag replicon particles, composed of Venezuelan equine encephalitis virus (VEE) replicon RNA and Sindbis surface structure (SIN). i.n./i.m., compared with any other immunizations, i.n./i.m. immunization with VEE/SIN-gag resulted in enhanced genital tract but not serum antibody responses. These data show for the first time that mucosal followed by systemic immunizations with gene delivery systems enhance B-cell responses independent of the mucosal homing receptors alpha4beta7 and alphaEbeta7.
[Show abstract][Hide abstract] ABSTRACT: Recombinant DNA technology, combined with the current understanding of antigen processing and recognition, provides a wide selection of possible approaches for vaccine development. The selection of a particular vaccine approach can thus be based on the desired outcome. Modern vaccinologists can select from a range of vaccines including subunits, purified proteins or polysaccharides, proteins made by recombinant methods in vitro, live vectors, or polynucleotides. Therefore, the treatment can be tailored according to the immune response desired and the safety, efficacy, and availability of the wild-type organism or naturally produced antigen. This article aims to review several of the recent advances and major patent applications in this area.