Genetic characterization and estimated 4CMenB vaccine strain coverage of 284 Neisseria meningitidis isolates causing invasive meningococcal disease in Argentina in 2010-2014

Meningococcal (Neisseria meningitidis) serogroup B (MenB) strain antigens are diverse and a limited number of strains can be evaluated using the human serum bactericidal antibody (hSBA) assay. The genetic Meningococcal Antigen Typing System (gMATS) was developed to predict the likelihood of coverage for large numbers of isolates by the 4CMenB vaccine, which includes antigens Neisseria adhesin A (NadA), Neisserial Heparin-Binding Antigen (NHBA), factor H-binding protein (fHbp), and Porin A (PorA). In this study, we characterized by whole-genome analyses 284 invasive MenB isolates collected from 2010 to 2014 by the Argentinian National Laboratories Network (52-61 isolates per year). Strain coverage was estimated by gMATS on all isolates and by hSBA assay on 74 randomly selected isolates, representative of the whole panel. The four most common clonal complexes (CCs), accounting for 81.3% of isolates, were CC-865 (75 isolates, 26.4%), CC-32 (59, 20.8%), CC-35 (59, 20.8%), and CC-41/44 (38, 13.4%). Vaccine antigen genotyping showed diversity. The most prevalent variants/peptides were fHbp variant 2, NHBA peptides 24, 21, and 2, and PorA variable region 2 profiles 16-36 and 14. The nadA gene was present in 66 (23.2%) isolates. Estimated strain coverage by hSBA assay showed 78.4% of isolates were killed by pooled adolescent sera, and 51.4% and 64.9% (based on two different thresholds) were killed by pooled infant sera. Estimated coverage by gMATS (61.3%; prediction interval: 55.5%, 66.7%) was consistent with the infant hSBA assay results. Continued genomic surveillance is needed to evaluate the persistence of major MenB CCs in Argentina.

Vaccination with OprB porin, and its epitopes offers protection against A. baumannii infections in mice

A. baumannii is a deadly antimicrobial resistance pathogen that acquires drug resistance through different mechanisms. Therefore, it is necessary to investigate all its virulence factors and design effective vaccines against it. For this purpose, OprB, an outer membrane porin, was investigated in this study, and its secondary and tertiary structures, physicochemical properties, and B-T epitopes were determined. The vaccine potential of this protein and its linear, non-continuous, and chimeric epitopes were also in-vivo analyzed. Based on the results, two surface epitopes and one non-continuous epitope were identified. Surface contiguous epitopes were produced recombinantly and non-continuous epitope sequences were synthesized and then produced. The chimeric epitope was also produced via the SOE-PCR technique. Active and passive immunization of mice with the whole OprB protein, non-continuous epitope, contiguous epitopes, two epitopes in chimeric form, as well as the mixture of two purified epitopes showed that the survival level and total IgG titer of the mice compared to non-vaccinated mice or mice that were vaccinated with an internal fragment increased significantly. The bacterial load in the immunized mice's lung, liver, kidney, and spleen was much lower than in the control groups, and the TNF-α, IFN-γ, and IL-6 cytokines levels were also lower in these groups and were similar to the naive mice. On the other hand, subunit vaccines showed acceptable safety and due to their minimal cross-activity, their use is much safer.

Dual template (epitope) imprinted electrode for sensing bacterial protein with high selectivity

Epitope imprinting has shown better prospects to synthesize synthetic receptors for proteins. Here, dual epitope imprinted polymer electrode (DEIP) matrix was fabricated on gold surface of electrochemical quartz crystal microbalance (EQCM) for recognition of target epitope sequence in blood samples of patients suffering from brain fever. Epitope sequences from outer membrane protein Por B of Neisseria meningitidis (MC58) bacteria predicted through immunoinformatic tools were chosen for imprinting. Self-assembled monolayers (SAM) of cysteine appended epitope sequences on gold nanoparticles were subjected to polymerization prior to electrodeposition on gold coated EQCM electrode. The polymeric matrix was woven around the cysteine appended epitope SAMs through multiple monomers (3-sulfo propyl methacrylate potassium salt (3-SPMAP), benzyl methacrylate (BMA)) and crosslinker (N, N'-methylene-bis-acrylamide). On extraction of the peptide sequences, imprinted cavities were able to selectively and specifically bind targeted epitope sequences in laboratory samples as well as 'real' samples of patients. Selectivity of sensor was examined through mismatched peptide sequences and certain plasma proteins also. The sensor was able to show specific binding towards the blood samples of infected patients, even in the presence of 'matrix' and other plasma proteins such as albumin and globulin. Even other peptide sequences, similar to epitope sequences only with one or two amino acid mismatches were also unable to show any binding. The analytical performance of DEIP-EQCM sensor was tested through selectivity, specificity, matrix effect, detection limit (0.68-1.01 nM), quantification limit (2.05-3.05 nM) and reproducibility (RSD ~ 5%). Hence, a diagnostic tool for bacterium causing meningitis is successfully fabricated in a facile manner which will broaden the clinical access and make efficient population screening feasible.

CD169+ Subcapsular Macrophage Role in Antigen Adjuvant Activity

Vaccines have played a pivotal role in improving public health, however, many infectious diseases lack an effective vaccine. Controlling the spread of infectious diseases requires continuing studies to develop new and improved vaccines. Our laboratory has been investigating the immune enhancing mechanisms of Toll-like receptor (TLR) ligand-based adjuvants, including the TLR2 ligand Neisseria meningitidis outer membrane protein, PorB. Adjuvant use of PorB increases costimulatory factors on antigen presenting cells (APC), increases antigen specific antibody production, and cytokine producing T cells. We have demonstrated that macrophage expression of MyD88 (required for TLR2 signaling) is an absolute requirement for the improved antibody response induced by PorB. Here-in, we specifically investigated the role of subcapsular CD169+ marginal zone macrophages in antibody production induced by the use of TLR-ligand based adjuvants (PorB and CpG) and non-TLR-ligand adjuvants (aluminum salts). CD169 knockout mice and mice treated with low dose clodronate treated animals (which only remove marginal zone macrophages), were used to investigate the role of these macrophages in adjuvant-dependent antibody production. In both sets of mice, total antigen specific immunoglobulins (IgGs) were diminished regardless of adjuvant used. However, the greatest reduction was seen with the use of TLR ligands as adjuvants. In addition, the effect of the absence of CD169+ macrophages on adjuvant induced antigen and antigen presenting cell trafficking to the lymph nodes was examined using immunofluorescence by determining the relative extent of antigen loading on dendritic cells (DCs) and antigen deposition on follicular dendritic cells (FDC). Interestingly, only vaccine preparations containing PorB had significant decreases in antigen deposition in lymphoid follicles and germinal centers in CD169 knockout mice or mice treated with low dose clodronate as compared to wildtype controls. Mice immunized with CpG containing preparations demonstrated decreased FDC networks in the mice treated with low dose clodronate. Conversely, alum containing preparations only demonstrated significant decreases in IgG in CD169 knockout mice. These studies stress that importance of subcapsular macrophages and their unique role in adjuvant-mediated antibody production, potentially due to an effect of these adjuvants on antigen trafficking to the lymph node and deposition on follicular dendritic cells.

Meningococcal B vaccine antigen FHbp variants among disease-causing Neisseria meningitidis B isolates, Italy, 2014-2017

Background

Typing of Neisseria meningitidis isolates is crucial for the surveillance of invasive meningococcal disease (IMD). We performed a molecular epidemiology study of N. meningitidis serogroup B (MenB) causing IMD in Italy between 2014 and 2017 to describe circulating strains belonging to this serogroup, with particular regards to the two factor H-binding protein (FHbp) subfamilies present in the bivalent MenB vaccine.

Materials and methods

A total of 109 culture positive and 46 culture negative MenB samples were collected within the National Surveillance System (NSS) of IMD in Italy and molecularly analyzed by conventional methods.

Results

Overall, 71 MenB samples showed the FHbp subfamily A and 83 the subfamily B. The subfamily variants were differently distributed by age. The most frequent variants, A05 and B231, were associated with cc213 and cc162, respectively. All MenB with the FHbp A05 variant displayed the PorA P1.22,14 and 85.7% of them the FetA F5-5. The majority of MenB with the FHbp B231 variant showed the PorA P1.22,14 (65.4%) and 84.6%, the FetA F3-6.

Conclusion

MenB circulating in Italy were characterized by a remarkable association between clonal complex and FHbp variants, although a high degree of genetic diversity observed over time. A dynamic trend in clonal complexes distribution within MenB was detected. Our results stress the importance of continued meningococcal molecular surveillance to evaluate the potential vaccine coverage of the available MenB vaccines.

Immunoinformatics design of multivalent chimeric vaccine for modulation of the immune system in Pseudomonas aeruginosa infection

Increasing in drug-resistant Pseudomonas aeruginosa and high mortality and morbidity rate have become a health challenge worldwide; therefore, developing the novel therapeutic strategies such as immunogenic vaccine candidate are required. Despite a substantial research effort, the future of immunization against P. aeruginosa due to failure in covering two separate stages of infection, and furthermore, inducing ineffective type of immune response, still remains controversial. In this study, immunoinformatics approach was utilized to design multivalent chimeric vaccine from both stages of infection containing Lectin, HIV TAT peptide, N-terminal fragment of exotoxin A and Epi8 of outer membrane protein F (OprF) with hydrophobic linkers which have a high density of B-cell, T Lymphocytes (HTL), T Lymphocytes (CTL), and IFN-γ epitopes. The physicochemical properties, antigenicity, and allergenicity for designed vaccine were analyzed. 3D model generation and refinement further validation of the final vaccine were followed by computational docking with molecular dynamics analyses that demonstrated high- affinity interaction between vaccine and TLR-4. Finally, designed vaccine was in silico cloned in pET22b. We have expected that the designed vaccine able to elucidate innate, humoral and cellular innate immune responses and control the interaction of P. aeruginosa with host and maybe overcome to P. aeruginosa vaccines drawback.

A Recombinant Chlamydia trachomatis MOMP Vaccine Elicits Cross-serogroup Protection in Mice Against Vaginal Shedding and Infertility

BACKGROUND

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen worldwide. Here, we determined the ability of a C. trachomatis recombinant major outer membrane protein (rMOMP) vaccine to elicit cross-serogroup protection.

METHODS

Female C3H/HeN mice were vaccinated by mucosal and systemic routes with C. trachomatis serovar D (UW-3/Cx) rMOMP and challenged in the ovarian bursa with serovars D (UW-3/Cx), D (UCI-96/Cx), E (IOL-43), or F (N.I.1). CpG-1826 and Montanide ISA 720 were used as adjuvants.

RESULTS

Immune responses following vaccination were more robust against the most closely related serovars. Following a genital challenge (as determined by number of mice with positive vaginal cultures, number of positive cultures, number of inclusion forming units recovered, and number of days with positive cultures) mice challenged with C. trachomatis serovars of the same complex were protected but not those challenged with serovar F (N.I.1) from a different subcomplex. Females were caged with male mice. Based on fertility rates, number of embryos, and hydrosalpinx formation, vaccinated mice were protected against challenges with serovars D (UW-3/Cx), D (UCI-96/Cx), and E (IOL-43) but not F (N.I.1).

CONCLUSIONS

This is the first subunit vaccine shown to protect mice against infection, pathology, and infertility caused by different C. trachomatis serovars.

Route of Vaccine Administration Influences the Impact of Fms-Like Tyrosine Kinase 3 Ligand (Flt3L) on Chlamydial-Specific Protective Immune Responses

We tested the hypothesis that the impact of the Fms-like tyrosine kinase 3-ligand (Flt3L; FL) on recombinant Vibrio cholerae ghost (rVCG) vaccine-induced chlamydial immunity is influenced by route of vaccine delivery. Female C57BL/6J mice were immunized rectally (IR) or intramuscularly (IM) with rVCG co-expressing the Chlamydia trachomatis PmpD and PorB proteins (rVCG- PmpD/PorB) with and without FL or glycoprotein D of HSV-2 (rVCG-gD2) as antigen control. Vaccine evaluation was based on measurement of T cell proliferation, Th1/Th2 cytokine, and humoral responses at systemic and mucosal compartments, and protection against intravaginal challenge infection. Results revealed that high levels of CD4+ T cell-mediated and humoral immune responses, were elicited in mice as a function of both IR and IM immunization. Unexpectedly, co-administration of vaccine with FL enhanced specific Th1-type cytokine levels and T cell proliferative responses following IR but not IM immunization. While administration of vaccine with FL enhanced the specific mucosal and systemic IgA antibody responses following both immunization routes, IgG2c responses were not enhanced following IR delivery. The vaccine-induced immune effectors protected mice against live heterologous C. muridarum infection irrespective of route of vaccine administration, with the regimen incorporating FL having a protective advantage. Further evaluation showed that protection afforded by the FL adjuvanted vaccine was facilitated by CD4+ T cells, as indicated by reduction in the intensity and duration of genital chlamydial shedding by naïve mice following adoptive transfer of immune CD4+ T cells. Taken together, the results indicate that comparable protective immunity, which is enhanced by co-delivery with FL, is elicited in the female genital tract against Chlamydia infection after mucosal and systemic administration, highlighting the ability of FL to function as an effective immunostimulator at both mucosal and systemic sites. The differential modulation of humoral and cellular immune responses, and protective immunity afforded by the FL adjuvanted vaccine following IR administration indicates that the immunomodulatory impact of FL on chlamydial-specific immunity is influenced by the route of vaccine administration. Thus, targeting of VCG-based vaccines to antigen presenting cells by co-delivery with FL is a feasible immunization approach for inducing effective chlamydial immunity in the female genital tract.

Modulation of immune response and protective efficacy of recombinant outer-membrane protein F (rOmpF) of Aeromonas hydrophila in Labeo rohita

The outer-membrane proteins (OMPs) of Aeromonas hydrophila, an imperative fish pathogen accountable for massive economic losses to aquaculture industry, are found to be immunogenic and considered as potential vaccine candidates. In spite of development in the formulation of vaccine candidates against Aeromonas infection, no commercial preparation has been done so far; in addition, the molecular mechanisms of immunoprotection induced by various vaccine formulations in Indian major carp, Labeo rohita, are little known. The present study was undertaken to evaluate the modulation of immunity and expression of immune-related genes post-rOmpF (recombinant outer-membrane protein of A. hydrophila, a novel vaccine candidate) immunization and protective efficacy after A. hydrophila challenge. The rOmpF-immunized fish showed a variable expression of the immune-related genes, viz. toll-like receptor 22 (TLR), complement component 3 (C3), chemokine (CXCa), tumor necrosis factor-α (TNFα), interleukin 1β (IL-1β), manganese superoxide dismutase (MnSOD) and natural killer enhancing factor (NKEF) in the head kidney tissues, when compared to the control group at different time intervals post-vaccination. A significant increase in serum hemolysin titer, ceruloplasmin level and myeloperoxidase activity was observed on day 140 post immunization. Also, bacterial agglutination titer and antiprotease activity were significantly increased on day 42 post immunization. No significant change was observed in lysozyme activity. Challenge studies with live A. hydrophila on day 140 post-immunization of L. rohita significantly increased the relative percentage survival (∼44%) in the vaccinated group. The results suggest that the rOmpF could be used as a potential vaccine candidate to combat A. hydrophila infection in fish.

Diagnostic utility of serological biomarkers in patients with Crohn's disease: A case-control study

The aim of this study was to examine the expression of serological markers in patients with inflammatory bowel disease in China, and determine the diagnostic utility of serological markers, individually and in combination, for the diagnosis and differential diagnosis of Crohn's disease (CD).Serum samples were obtained from 160 participants in Eastern China. Among the participants, 98 were diagnosed with CD, 33 had ulcerative colitis (UC), and 29 were healthy controls (HC). The serum samples were tested for the presence of antibodies against outer membrane porin C (anti-OmpC), Pseudomonas fluorescens bacterial sequence I2 (anti-I2), anti-laminarin (anti-L), anti-chitin (anti-C), anti-chitobioside carbohydrate antibody (ACCA), anti-laminaribioside carbohydrate antibody (ALCA), anti-mannobioside carbohydrate antibody (AMCA), and anti-Saccharomyces cerevisiae antibody (ASCA) by indirect enzyme-linked immunosorbent assay (ELISA).Individually, anti-C, anti-L, ASCA-IgG, and ALCA lacked diagnostic value in the differentiation of CD. ASCA-IgA remained the most accurate marker for the diagnosis of CD, with an area under the curve (AUC) of 0.77; however, its sensitivity and specificity were both lower than 75%. Among the combinations of the 5 markers with significant diagnosing ability for CD, combinations with any 2 of the 3 markers, ASCA IgA, AMCA, and ACCA positive, provided the best accuracy in the diagnosis and differential diagnosis of CD (sensitivity and specificity both above 75%) and had the highest Youden index.Serological antibodies, when considered in combination, have remarkable value in the diagnosis and differential diagnosis of CD. Especially, the combination of any 2 of the 3 markers, ASCA-IgA, AMCA, ACCA positive, appears to be optimal.

Serologic Reactivity Reflects Clinical Expression of Ulcerative Colitis in Children

Background

In contrast to pediatric Crohn's disease (CD), little is known in pediatric ulcerative colitis (UC) about the relationship between disease phenotype and serologic reactivity to microbial and other antigens.

Aim

The aim of this study was to examine disease phenotype and serology in a well-characterized inception cohort of children newly diagnosed with UC during the PROTECT Study (Predicting Response to Standardized Pediatric Colitis Therapy).

Methods

Patients were recruited from 29 participating centers. Demographic, clinical, laboratory, and serologic (pANCA, ASCA IgA/IgG, Anti-CBir1, and Anti-OmpC) data were obtained from children 4-17 years old with UC.

Results

Sixty-five percent of the patients had positive serology for pANCA, with 62% less than 12 years old and 66% 12 years old or older. Perinuclear anti-neutrophil cytoplasmic antibodies did not correspond to a specific phenotype though pANCA ≥100, found in 19%, was strongly associated with pancolitis (P = 0.003). Anti-CBir1 was positive in 19% and more common in younger children with 32% less than 12 years old as compared with 14% 12 years old or older (P < 0.001). No association was found in any age group between pANCA and Anti-CBir1. Relative rectal sparing was more common in +CBir1, 16% versus 7% (P = 0.02). Calprotectin was lower in Anti-CBir1+ (Median [IQR] 1495 mcg/g [973-3333] vs 2648 mcg/g [1343-4038]; P = 0.04). Vitamin D 25-OH sufficiency was associated with Anti-CBir1+ (P = 0.0009).

Conclusions

The frequency of pANCA in children was consistent with adult observations. High titer pANCA was associated with more extensive disease, supporting the idea that the magnitude of immune reactivity may reflect disease severity. Anti-CBir1+ was more common in younger ages, suggesting host-microbial interactions may differ by patient age.

Recombinant Hsp33 and OmpC protein can serve as promising divalent vaccine with protection against Vibrio anguillarum and Edwardsiella tarda in flounder (Paralichthys olivaceus)

Vibrio anguillarum and Edwardsiella tarda are severe aquaculture pathogens shared similar epidemiological characteristics and susceptible to flounder (Paralichthys olivaceus). In our previous studies, recombinant(r) protein heat shock protein 33 (rHsp33) from V. anguillarum and outer membrane protein C (rOmpC) from E. tarda were proved to have protection against V. anguillarum and E. tarda, respectively. In this paper, the cross protection of rHsp33 against E. tarda and rOmpC against V. anguillarum, and the protection of divalent vaccine candidate (rHsp33 + rOmpC, rHC) against both V. anguillarum and E. tarda were evaluated. RHC, rHsp33, and rOmpC were vaccinated to flounder, respectively, and the percentages of surface immunoglobulin-positive (sIg+) cells in peripheral blood lymphocytes (PBLs), serum IgM, specific antibodies against V. anguillarum or E. tarda, specific antibodies against rHsp33, rOmpC or rHC, the expression of immune-related genes and relative percent survival (RPS) against V. anguillarum or E. tarda were measured. The results showed that: RHC could induced the enhancement of sIg + cells and high levels of specific antibodies against both V. anguillarm and E. tarda; Also a significant increase of specific antibodies against rHsp33, rOmpC or rHC, and up-regulation of gene expression of CD3, CD4-1, CD4-2, CD8α, CD8β and IgM in spleen, head-kidney, and hindgut, RPS of 70 ± 3.45% against V. anguillarum and 60 ± 1.48% against E. tarda, respectively. In addition, rHsp33 induced specific antibodies against E. tarda and rOmpC, and had a RPS of 43.3 ± 3.73% against E. tarda; rOmpC could evoke specific antibodies against V. anguillarum and rHsp33, and had a RPS of 44 ± 1.27% against V. anguillarm; The results demonstrated that there was cross protection of rHsp33 against E. tarda and rOmpC against V. anguillarum, rHC as a divalent vaccine can induce significant immune response and efficient protection against both E. tarda and V. anguillarum in flounder.

Surface display of OmpC of Salmonella serovar Pullorum on Bacillus subtilis spores

Salmonellosis is a major public health problem throughout the world. Thus, there is a huge need for diversified control strategies for Salmonella infections. In this work, we have assessed the potential use of Bacillus subtilis (B. subtilis) spores for the expression of a major protective antigen of Salmonella serovar Pullorum, OmpC. The expression of OmpC on the surface of spores was determined by immunofluorescence microscopy. Mice immunized with recombinant spores expressing the OmpC antigen presented significant levels of OmpC-specific serum IgG and mucosal SIgA antibodies than in mice immunized with non-recombinant spores (p<0.01). In addition, oral immunization with recombinant spores was able to induce a significant level of protection in mice against lethal challenge with Salmonella serovar Typhimurium. These results suggest that B. subtilis spores have promising potential in the development of mucosal vaccines against Salmonella infections.

Identification and characterization of a novel conserved 46 kD maltoporin of Aeromonas hydrophila as a versatile vaccine candidate in European eel (Anguilla anguilla)

European eel (Anguilla anguilla) is a crucial economic fish that has been plagued by Aeromonas hydrophila infections for many years. Vaccines that are cross-protective against multiple serotypes could provide an effective control against A. hydrophila-mediated diseases. The outer membrane proteins (OMPs) are highly immunogenic and capable of eliciting protective immune responses. This study reports the identification of a novel 46 kD maltoporin that is a conserved protective antigen for different serotypes of A. hydrophila. First, this study purified OMPs from the strains of A. hydrophila B10, B11, B12, B15, B19, and B20. Western blot analysis revealed that the 46 kD maltoporin of B11 could be strongly reacted with all the specific European eel antisera against the above OMPs from different serotypes A. hydrophila. Cloning and sequencing of the maltoporin revealed that it contains an open reading frame (ORF) of 1281 nucleotides encoding 426 amino acids. Further sequence alignment analysis using the NCBI Conserved Domain Database (CDD) along with performing three-dimensional structure analysis showed that this protein belongs to maltoporin family. Three different study groups of European eels were intraperitoneal injected with one of the following conditions: phosphate-buffered saline (PBS group), formaline-killed-whole-cell (FKC) of A. hydrophila (FKC group) or with the recombinant maltoporin (OMP group) to analyze the immunogenicity of the recombinant maltoporin purified by nickel chelate affinity chromatography. On 14, 21, 28 and 42 days post-vaccination respectively, proliferation of the whole blood cells, titers of specific antibody, and lysozyme activities of experimental eels were detected. On 28d post-vaccination, eels from the three groups were challenged by intraperitoneal injection with five different live strains of A. hydrophila (B10, B11, B15, B19, and B20). The results showed that the proliferation of whole blood cells in the OMP group was significantly enhanced on 14d and the serum antibody titers of vaccinated European eels in FKC and OMP group were significantly increased on 28d and 42d. Lysozyme activities in serum were significantly up-regulated in FKC and OMP groups on 21d. The relative percent survival (RPS) of OMP group challenged by A. hydrophila B10, B11, and B20 was 75%, 62.5%, and 88%. This was higher than the corresponding RPS of FKC group with 50%, 37.5%, and 66%, respectively. The RPS was up to 100% in both OMP and FKC group when challenged by A. hydrophila B15 and B19. These results indicate that the 46 kD maltoporin is an effective potent vaccine candidate against different serotypes of A. hydrophila.

The TLR2 Binding Neisserial Porin PorB Enhances Antigen Presenting Cell Trafficking and Cross-presentation

TOLL-like receptor (TLR) ligands activate both innate and adaptive immune cells, while modulating the cellular immune response. The outer membrane protein (OMP) from Neisseria meninigitidis, PorB, is a naturally occurring TLR2 ligand and functions as an adjuvant. Here, we demonstrate that PorB increases the level of OVA in the endo-/lysosomal cellular compartment of BMDCs, increases antigen presenting cell (APC) trafficking to draining lymph nodes, and enhances antigen cross-presentation. PorB is capable of mounting an antigen specific T cell response by efficiently stimulating antigen cross-presentation in vivo and in vitro assessed by BMDC OT-I cocultivation assays. The enhanced antigen cross-presentation and the increased APC recruitment to secondary lymphoid tissues expand the scope of known adjuvant effects of PorB on the immune system. Our findings lead to a better understanding of how TLR-ligand based adjuvants can alter and modulate immune responses.

[Purification of Salmonella Typhimurium OmpD porin induces long-term high levels of antibodies: implications on the development of vaccines against non-typhoid salmonella]

In the present work, we report, for the first time, on the purification of the Salmonella Typhimurium OmpD porin. We assessed the integrity and purity of the protein and evaluated the immunogenicity of the protein and its ability to induce antibody without exogenous adjuvant. We observed that 10 μg OmpD induced high antibody levels of IgM and IgG, which were maintained for more than 260 days after immunization. Immunization with OmpD induced multiple IgG antibody isotypes including IgG1, IgG2a, IgG2b, and IgG3 subclasses. Furthermore, these antibodies were able to recognize and bind to the bacterial surface. Our results demonstrate the high immunogenicity of S. Typhimurium OmpD porin, which induces long-lasting antibodies which may be and important target of the immune response against Salmonella infection. In conclusion, we propose the OmpD porin could be used within novel subunit vaccine formulations that do not need additional adjuvant and that confer long lasting humoral immunity against Salmonella infections.

Evaluation of the Leptospira interrogans Outer Membrane Protein OmpL37 as a Vaccine Candidate

The identification of potential vaccine candidates against leptospirosis remains a challenge. However, one such candidate is OmpL37, a potentially surface-exposed antigen that has the highest elastin-binding ability described to date, suggesting that it plays an important role in host colonization. In order to evaluate OmpL37's ability to induce a protective immune response, prime-boost, DNA and subunit vaccine strategies were tested in the hamster model of lethal leptospirosis. The humoral immune response was evaluated using an indirect ELISA test, and the cytokine profile in whole blood was determined by quantitative real-time PCR. Unlike the DNA vaccine, the administration of recombinant OmpL37 induced a strong IgG antibody response. When individually administrated, both formulations stimulated a TNF-α mediated inflammatory response. However, none of the OmpL37 formulations or vaccination strategies induced protective immunity. Further studies are required towards the identification of new vaccine targets against leptospirosis.

Chronic Infection by Mucoid Pseudomonas aeruginosa Associated with Dysregulation in T-Cell Immunity to Outer Membrane Porin F

RATIONALE

Pseudomonas aeruginosa (PA) is an environmental pathogen that commonly infects individuals with cystic fibrosis (CF) and non-CF bronchiectasis, impacting morbidity and mortality. To understand the pathobiology of interactions between the bacterium and host adaptive immunity and to inform rational vaccine design, it is important to understand the adaptive immune correlates of disease.

OBJECTIVES

To characterize T-cell immunity to the PA antigen outer membrane porin F (OprF) by analyzing immunodominant epitopes in relation to infection status.

METHODS

Patients with non-CF bronchiectasis were stratified by frequency of PA isolation. T-cell IFN-γ immunity to OprF and its immunodominant epitopes was characterized. Patterns of human leukocyte antigen (HLA) restriction of immunodominant epitopes were defined using HLA class II transgenic mice. Immunity was characterized with respect to cytokine and chemokine secretion, antibody response, and T-cell activation transcripts.

MEASUREMENTS AND MAIN RESULTS

Patients were stratified according to whether PA was never, sometimes (<50%), or frequently (≥50%) isolated from sputum. Patients with frequent PA sputum-positive isolates were more likely to be infected by mucoid PA, and they showed a narrow T-cell epitope response and a relative reduction in Th1 polarizing transcription factors but enhanced immunity with respect to antibody production, innate cytokines, and chemokines.

CONCLUSIONS

We have defined the immunodominant, HLA-restricted T-cell epitopes of OprF. Our observation that chronic infection is associated with a response of narrowed specificity, despite strong innate and antibody immunity, may help to explain susceptibility in these individuals and pave the way for better vaccine design to achieve protective immunity.

A new ELISA method for serological diagnosis of Legionella pneumophila: use of five purified proteins, FLA, MOMP, MIP, IP, and PILE, as diagnostic antigen

BACKGROUND

Legionella pneumophila plays an important role in human infection. Commercial ELISA kits commonly used, which take Legionella pneumophila whole-cell protein as the coating antigen, often have cross-reactivity among serogroups or species. In this study, five Legionella pneumophila proteins FLA, MOMP, MIP, IP, and PILE were purified and further applied in serological diagnosis of Legionella pneumophila infections compared with R & D Legionella ELISA kits.

METHODS

The five recombinant plasmids pET-fla, pET-momp, pET-mip, pET-ip, and pET-pile were transformed into E. coli BL21 and then induced them with IPTG. The expression products were analyzed by SDS-PAGE and purified by affinity chromatography. Indirect enzyme-linked immunosorbent assays (ELISAs) were established with the five purified proteins FLA, MOMP, MIP, IP, and PILE altogether as the coating antigen and tested for the presence of IgG, IgM, and IgA antibody independently from 50 positive sera and 40 negative sera, compared with R & D IgG, IgM, and IgA Legionella ELISA kits.

RESULTS

The FLA protein about 42 kDa in size, the MOMP protein about 45 kDa, the MIP protein about 40 kDa, the IP protein about 46 kDa, and the PILE protein about 35.7 kDa were separately expressed and purified. Compared with R & D IgG, IgM, and IgA Legionella ELISA kit, the outcome of indirect ELISAs set up with the five purified proteins showed that for IgG the sensitivity was 90.4%, the specificity was 97.4%, the area under ROC curve was 0.939, the kappa value was 0.865, the 95% confidence interval was 0.883 - 0.995. For IgM the sensitivity was 91.8%, the specificity was 95.1%, the area under ROC curve was 0.935, the kappa value was 0.866, the 95% confidence interval was 0.876 - 0.994. For IgA the sensitivity was 93.6%, the specificity was 95.3%, the area under ROC curve was 0.945, the kappa value was 0.889, the 95% confidence interval was 0.890 - 0.999.

CONCLUSIONS

The proteins FLA, MOMP, MIP, IP, and PILE were successfully expressed and purified, and they seemed to be suitable coating antigens for the serological diagnosis of Legionella pneumophila.

A novel recombinant bivalent outer membrane protein of Vibrio vulnificus and Aeromonas hydrophila as a vaccine antigen of American eel (Anguilla rostrata)

The immogenicity of a novel vaccine antigen was evaluated after immunized American eels (Anguilla rostrata) with a recombinant bivalent expressed outer membrane protein (OMP) of Vibrio vulnificus and Aeromonas hydrophila. Three groups of eels were intraperitoneal (i.p) injected with phosphate-buffered saline (PBS group), formaline-killed-whole-cell (FKC) of A. hydrophila and V. vulnificus (FKC group) or the bivalent OMP (OMP group). On 14, 21, 28 and 42 days post-vaccination respectively, proliferation of the whole blood cells, titers of specific antibody and lysozyme activities of experimental eels were detected. On 28 day post-vaccination, eels from three groups were challenged by i.p injection of live A. hydrophila or V. vulnificus. The results showed that, compared with the PBS group, proliferation of whole blood cells in OMP group was significant enhanced on 28 days, and the serum titers of anti-A.hydrophila and anti-V. vulnificus antibody in eels of FKC and OMP group were significant increased on 14, 21 and 28d. Lysozyme Activities in serum, skin mucus, liver and kidney were significant changed between the three groups. Relative Percent Survival (RPS) after challenged A. hydrophila in KFC vs. PBS group and OMP vs. PBS group were 62.5% and 50% respectively, and the RPS challenged V. vulnificus in FKC and OMP vs. PBS group were 37.5% and 50% respectively. These results suggest that American eels immunized with the bivalent OMP would positively affect specific as well as non-specific immune parameters and protect against infection by the two pathogens in fresh water farming.

Adjuvant effects elicited by novel oligosaccharide variants of detoxified meningococcal lipopolysaccharides on Neisseria meningitidis recombinant PorA protein: a comparison in mice

Neisseria meningitidis lipopolysaccharide (LPS) has adjuvant properties that can be exploited to assist vaccine immunogenicity. The modified penta-acylated LPS retains the adjuvant properties of hexa-acylated LPS but has a reduced toxicity profile. In this study we investigated whether two modified glycoform structures (LgtE and IcsB) of detoxified penta-acylated LPS exhibited differential adjuvant properties when formulated as native outer membrane vesicles (nOMVs) as compared to the previously described LgtB variant. Detoxified penta-acylated LPS was obtained by disruption of the lpxL1 gene (LpxL1 LPS), and three different glycoforms were obtained by disruption of the lgtB, lgtE or icsB genes respectively. Mice (mus musculus) were immunized with a recombinant PorA P1.7-2,4 (rPorA) protein co-administered with different nOMVs (containing a different PorA serosubtype P1.7,16), each of which expressed one of the three penta-acylated LPS glycoforms. All nOMVs induced IgG responses against the rPorA, but the nOMVs containing the penta-acylated LgtB-LpxL1 LPS glycoform induced significantly greater bactericidal activity compared to the other nOMVs or when the adjuvant was Alhydrogel. Compared to LgtE or IcsB LPS glycoforms, these data support the use of nOMVs containing detoxified, modified LgtB-LpxL1 LPS as a potential adjuvant for future meningococcal protein vaccines.

Antigenic variation of TprK facilitates development of secondary syphilis

Although primary syphilis lesions heal spontaneously, the infection is chronic, with subsequent clinical stages. Healing of the primary chancre occurs as antibodies against outer membrane antigens facilitate opsonophagocytosis of the bacteria by activated macrophages. TprK is an outer membrane protein that undergoes antigenic variation at 7 variable regions, and variants are selected by immune pressure. We hypothesized that individual TprK variants escape immune clearance and seed new disseminated lesions to cause secondary syphilis. As in human syphilis, infected rabbits may develop disseminated secondary skin lesions. This study explores the nature of secondary syphilis, specifically, the contribution of antigenic variation to the development of secondary lesions. Our data from the rabbit model show that the odds of secondary lesions containing predominately TprK variant treponemes is 3.3 times higher than the odds of finding TprK variants in disseminated primary lesions (odds ratio [OR] = 3.3 [95% confidence interval {CI}, 0.98 to 11.0]; P = 0.055) and that 96% of TprK variant secondary lesions are likely seeded by single treponemes. Analysis of antibody responses demonstrates significantly higher antibody titers to tprK variable region sequences found in the inoculum compared to reactivity to tprK variant sequences found in newly arising secondary lesions. This suggests that tprK variants escape the initial immune response raised against the V regions expressed in the inoculum. These data further support a role for TprK in immune evasion and suggest that the ability of TprK variants to persist despite a robust immune response is instrumental in the development of later stages of syphilis.

Antigenic relatedness defines Toll-like receptor 2 is crafted on ligand blueprint

Toll-like receptors are located particularly on mammalian immune cells to recognize pathogen-associated molecules. Toll-like receptors are categorized on the basis of ligand specificity that includes Toll-like receptor 2 with affinity for bacterial porin, the major outer membrane protein. Here we show TLR2 antibody recognizes the monomer of porin, primarily a TLR2-ligand in Western blot, thus displaying relatedness of primary structures between the receptor and its ligand. Quantitative analysis revealed relatedness of the native porin molecule with TLR2 was as high as 71%, suggesting imprint of native porin trimer is mostly copied by the receptor crossing limits of primary structures. Flow cytometric analysis of TLR2 on HEK-293 cells shows the receptor and ligand also have common molecular patterns on surface, which is distinctively separate from regions assigned for putative TLR(*)ligand interaction. Molecular mimetic and specificity of TLR will caution investigators targeting TLR-ligands to develop adjuvants and vaccines.

Frequency of Chlamydia trachomatis-specific T cell interferon-γ and interleukin-17 responses in CD4-enriched peripheral blood mononuclear cells of sexually active adolescent females

An evaluation of CD4 T cell responses to candidate Chlamydia trachomatis vaccine antigens was conducted in an adolescent female cohort exposed through natural infection to explore antigen immunogenicity and correlation with protection from reinfection. The frequency of peripheral blood CD4 T cell IFN-γ and IL-17 responses to three candidate vaccine antigens, polymorphic membrane protein G (PmpG), F (PmpF), and major outer membrane protein (MOMP), were determined by ELISPOT; responses to chlamydial heat shock protein 60 (HSP60) and to elementary bodies (EB) were included for comparison. Responses of Infected (n=8), Seropositive/Uninfected (n=13), and Seronegative/Uninfected (n=18) participants were compared. The median CD4 IFN-γ response to EB was significantly increased in Infected (P=0.003) and Seropositive/Uninfected (P=0.002) versus Seronegative/Uninfected female subjects. Higher rates of positive IFN-γ responders to EB, PmpF, and MOMP were detected in Seropositive/Uninfected versus Seronegative/Uninfected participants (P=0.021). IL-17 responses were generally low. A positive IFN-γ response to any of the antigens tested was associated with a trend toward a reduced risk of reinfection, although not statistically significant. Among this adolescent cohort, chlamydial-specific CD4 IFN-γ but not IL-17 responses were detected in acutely and previously infected participants and a positive CD4 IFN-γ response was associated with a non-significant reduced risk of reinfection.

Variability of genes encoding surface proteins used as vaccine antigens in meningococcal endemic and epidemic strain panels from Norway

Surface-expressed protein antigens such as factor H-binding protein (fHbp), Neisserial adhesin A (NadA), Neisserial heparin-binding antigen (NHBA) and Porin protein A (PorA); all express sequence variability that can affect their function as protective immunogens when used in meningococcal serogroup B vaccines like the recently-approved 4CMenB (Bexsero(®)). We assessed the sequence variation of genes coding for these proteins and two additional proteins ("fusion partners" to fHbp and NHBA) in pathogenic isolates from a recent low incidence period (endemic situation; 2005-2006) in Norway. Findings among strains from this panel were contrasted to what was found among isolates from a historic outbreak (epidemic situation; 1985-1990). Multilocus sequence typing revealed 14 clonal complexes (cc) among the 66 endemic strains, while cc32 vastly predominated in the 38-strain epidemic panel. Serogroup B isolates accounted for 50/66 among endemic strains and 28/38 among epidemic strains. Potential strain-coverage ("sequence match") for the 4CMenB vaccine was identified among the majority (>70%) of the endemic serogroup B isolates and all of the epidemic serogroup B isolates evaluated. Further information about the degree of expression, surface availability and the true cross-reactivity for the vaccine antigens will be needed to fully characterize the clinical strain-coverage of 4CMenB in various geographic and epidemiological situations.