Identification of a peptide-pheromone that enhances Listeria monocytogenes escape from host cell vacuoles

Listeria monocytogenes is a Gram-positive facultative intracellular bacterial pathogen that invades mammalian cells and escapes from membrane-bound vacuoles to replicate within the host cell cytosol. Gene products required for intracellular bacterial growth and bacterial spread to adjacent cells are regulated by a transcriptional activator known as PrfA. PrfA becomes activated following L. monocytogenes entry into host cells, however the signal that stimulates PrfA activation has not yet been defined. Here we provide evidence for L. monocytogenes secretion of a small peptide pheromone, pPplA, which enhances the escape of L. monocytogenes from host cell vacuoles and may facilitate PrfA activation. The pPplA pheromone is generated via the proteolytic processing of the PplA lipoprotein secretion signal peptide. While the PplA lipoprotein is dispensable for pathogenesis, bacteria lacking the pPplA pheromone are significantly attenuated for virulence in mice and have a reduced efficiency of bacterial escape from the vacuoles of nonprofessional phagocytic cells. Mutational activation of PrfA restores virulence and eliminates the need for pPplA-dependent signaling. Experimental evidence suggests that the pPplA peptide may help signal to L. monocytogenes its presence within the confines of the host cell vacuole, stimulating the expression of gene products that contribute to vacuole escape and facilitating PrfA activation to promote bacterial growth within the cytosol.

Mycoplasma gallisepticum inactivated by targeting the hydrophobic domain of the membrane preserves surface lipoproteins and induces a strong immune response

An innovative approach for inactivation of Mycoplasma gallisepticum using the hydrophobic photoinduced alkylating probe 1, 5-iodonaphthylazide (INA) is described. Treatment of washed M. gallisepticum mid-exponential culture (0.2 mg cell protein /mL) with INA followed by irradiation with far-ultraviolet light (310–380 nm) completely abolished viability. Transmission electron microscopy showed that the majority of the inactivated M. gallisepticum were comparable in size to intact cells, but that part of the INA-treated M. gallisepticum preparation also contained low density cells and membrane vesicles. Confocal microscopy revealed that untreated M. gallisepticum cells were internalized by chicken red blood cells (c-RBCs), whereas the INA-inactivated cells remained attached to the outer surface of the c-RBCs. INA treatment of M. gallisepticum resulted in a complete inactivation of F0F1 –ATPase and of the L-arginine uptake system, but the cytoplasmatic soluble NADH2 dehydrogenase was only partially affected. Western blot analysis of the lipoprotein fraction showed that the INA-treated M. gallisepticum retained their lipoproteins. Following subcutaneous injection of M. gallisepticum INA-bacterin, 100% and 68.8% of chickens were positive by the rapid serum agglutination test and enzyme-linked immunosorbent assay respectively, 2 weeks post-injection. These data suggest that the photoinducible alkylating agent INA inactivates M. gallisepticum but preserves its surface lipoproteins and thus has the potential to be used as a general approach for the inactivation of mycoplasmas for vaccine development.

Lipoprotein in the cell wall of Staphylococcus aureus is a major inducer of nitric oxide production in murine macrophages

Staphylococcus aureus is a Gram-positive bacterium that causes inflammation at infection sites by inducing various inflammatory mediators such as nitric oxide (NO). To identify the staphylococcal virulence factors contributing to NO production, we compared the ability of ethanol-killed wild-type S. aureus and mutant strains lacking lipoteichoic acid (ΔltaS), lipoproteins (Δlgt), or d-alanine (ΔdltA) to stimulate NO production in a murine macrophage cell line, RAW 264.7, and the primary macrophages derived from C57BL/6 mice. Wild-type, ΔltaS, and ΔdltA strains induced NO production in a dose-dependent manner but this response was not observed when the cells were stimulated with the Δlgt strain. Moreover, purified lipoproteins triggered NO production in macrophages. Coincident with NO induction, the wild-type, ΔltaS, and ΔdltA strains induced expression of inducible NO synthase (iNOS) at both mRNA and protein levels whereas Δlgt failed to induce iNOS protein or mRNA. Transient transfection followed by a reporter gene assay and Western blotting experiments demonstrated that wild-type, ΔltaS, and ΔdltA strains, but not the Δlgt strain, induced substantial activation of NF-κB and STAT1 phosphorylation, both of which are known to be crucial for iNOS expression. Moreover, wild-type, ΔltaS, and ΔdltA strains increased Toll-like receptor 2 (TLR2) activation, which is known to mediate S. aureus-induced innate immunity, whereas the Δlgt strain did not. Collectively, these results suggest that lipoproteins in the cell wall of S. aureus play a major role in the induction of NO production in murine macrophages through activation of the TLR2 receptor.

Release and Cytokine Production of BmpB from BmpB-Loaded pH-Sensitive and Mucoadhesive Thiolated Eudragit Microspheres

Swine dysentery is a contagious mucohaemorrhagic colitis of pigs that is caused by anaerobic intestinal spirochaete Brachyspira hyodysenteriae. Recently, an outer membrane lipoprotein of B. hyodysenteriae (BmpB) has been identified, and the mice or pigs immunized with a recombinant BmpB generated antibodies recognizing the native BmpB of B. hyodysenteriae. In this study, we cloned, expressed and purified BmpB protein from E. coli and used it as a vaccine candidate for oral delivery. The BmpB was encapsulated into the pH-sensitive and thiolated Eudragit microspheres (TEMS). The sizes of the microspheres ranged from 5-20 μ. About 22-34% of BmpB were released from the BmpB-loaded TEMS within 24 h at stomach pH 2.0 whereas the release of BmpB from the BmpB-loaded TEMS was 35% in the first one hour and reached 81% within 24 h at intestinal pH 7.2. These data revealed that the BmpB could be protected in the harsh gastric condition. Mucoadhesive experiment in vitro showed that TEMS have high binding affinity with the mucin glycoproteins of porcine intestine. Finally, in vitro production of cytokines from immune cells treated with the BmpB-loaded TEMS suggested that the TEMS would be a promising approach for oral delivery of BmpB as vaccine candidate.

[LC3-LpqH enhances the immunoprotection of Ag85B DNA vaccine against Mycobacterium tuberculosis]

OBJECTIVE

To explore the effect of microtubule-associated protein light chain 3- lipoprotein antigen precursor (pCMV-LC3-LpqH) as an DNA adjuvant on the immunoprotection of the anti-tuberculosis DNA vaccine encoding Ag85B antigen from Mycobacterium tuberculosis (MTB).

METHODS

BALB/c mice were randomly divided into four groups that were immunized three times with pCMV-Ag85B, pCMV-LpqH/pCMV-Ag85B, pCMV-LC3-LpqH/pCMV-Ag85B and pCMV, respectively. Two weeks after the final vaccination, the titers and subtypes of anti-Ag85B IgG of BALB/c mice were detected by ELISA. In vitro, the levels of interleukin 2 (IL-2), interferon γ (IFN-γ), IL-4 and IL-10 that were secreted from Ag85B-stimulated splenocytes were also measured by ELISA. Three months after the final vaccination, mice were challenged with virulent MTB H37Rv strain through the tail veins. The mice spleens and lungs were dissected out for counting colony-forming unit (CFU) and observing pulmonary histopathological changes after MTB infection.

RESULTS

LC3-LpqH/Ag85B-immunized mice showed the significant increase of IgG2a, IL-2 and IFN-γ, along with the decrease of IgG1, IL-4 and IL-10, lower MTB CFU in the spleens and lungs and a marked relief in pulmonary injury.

CONCLUSION

LC3-LpqH could enhance Ag85B-specific Th1 immune response that exerts a superior immune protection, which might be a new practical strategy for developing MTB vaccines.

Design and development of a novel vaccine for protection against Lyme borreliosis

There is currently no Lyme borreliosis vaccine available for humans, although it has been shown that the disease can be prevented by immunization with an OspA-based vaccine (LYMErix). Outer surface protein A (OspA) is one of the dominant antigens expressed by the spirochetes when present in a tick. The Borrelia species causing Lyme borreliosis in Europe express different OspA serotypes on their surface, B. burgdorferi (serotype 1), B. afzelii (serotype 2), B. garinii (serotypes, 3, 5 and 6) and B. bavariensis (serotype 4), while only B. burgdorferi is present in the US. In order to target all these pathogenic Borrelia species, we have designed a multivalent OspA-based vaccine. The vaccine includes three proteins, each containing the C-terminal half of two OspA serotypes linked to form a heterodimer. In order to stabilize the C-terminal fragment and thus preserve important structural epitopes at physiological temperature, disulfide bonds were introduced. The immunogenicity was increased by introduction of a lipidation signal which ensures the addition of an N-terminal lipid moiety. Three immunizations with 3.0 µg adjuvanted vaccine protected mice from a challenge with spirochetes expressing either OspA serotype 1, 2 or 5. Mice were protected against both challenge with infected ticks and in vitro grown spirochetes. Immunological analyses (ELISA, surface binding and growth inhibition) indicated that the vaccine can provide protection against the majority of Borrelia species pathogenic for humans. This article presents the approach which allows for the generation of a hexavalent vaccine that can potentially protect against a broad range of globally distributed Borrelia species causing Lyme borreliosis.

Lantibiotic immunity: inhibition of nisin mediated pore formation by NisI

Nisin, a 3.4 kDa antimicrobial peptide produced by some Lactococcus lactis strains is the most prominent member of the lantibiotic family. Nisin can inhibit cell growth and penetrates the target Gram-positive bacterial membrane by binding to Lipid II, an essential cell wall synthesis precursor. The assembled nisin-Lipid II complex forms pores in the target membrane. To gain immunity against its own-produced nisin, Lactococcus lactis is expressing two immunity protein systems, NisI and NisFEG. Here, we show that the NisI expressing strain displays an IC₅₀ of 73±10 nM, an 8–10-fold increase when compared to the non-expressing sensitive strain. When the nisin concentration is raised above 70 nM, the cells expressing full-length NisI stop growing rather than being killed. NisI is inhibiting nisin mediated pore formation, even at nisin concentrations up to 1 µM. This effect is induced by the C-terminus of NisI that protects Lipid II. Its deletion showed pore formation again. The expression of NisI in combination with externally added nisin mediates an elongation of the chain length of the Lactococcus lactis cocci. While the sensitive strain cell-chains consist mainly of two cells, the NisI expressing cells display a length of up to 20 cells. Both results shed light on the immunity of lantibiotic producer strains, and their survival in high levels of their own lantibiotic in the habitat.

[Preparation of an autophagy-targeted antituberculosis DNA vaccine encoding LpqH fused with LC3]

OBJECTIVE

To construct an autophagy-targeted vaccine harboring the genes encoding lipoprotein antigen precursor LpqH from Mycobacterium tuberculosis and microtubule-associated protein light chain-3(LC3), and to investigate its efficacy of inducing and targeting autophagy.

METHODS

The expressions of LC-3 and LC3-LpqH in RAW264.7 cells were detected by Western blotting after transfected with pCMV-LpqH and pCMV-LC3-LpqH plasmids respectively. The pCMV-LC3-LpqH or pCMV-LpqH plasmids were transfected into GFP-LC3-RAW264.7 cells to analyze the localization of LC3-LpqH by immunofluorescence staining.

RESULTS

After transfected with pCMV-LpqH DNA, RAW264.7 cells showed a significant increase of LC-3 amount. The LC3-LpqH fusion protein was also detected in RAW264.7 cells after pCMV-LC3-LpqH transfection and in a dose-dependent manner. Interestingly, LpqH was found to be transported to autophagosomes through the fusion protein, which was demonstrated by the co-localization of GFP-LC3 and LC3-LpqH on autophagosomes.

CONCLUSION

The recombinant plasmid encoding pCMV-LC3-LpqH could enhance the autophagy in vitro, and facilitate the localization of LpqH on autophagosomes. Our study provides a new practical strategy for the development of improved vaccines against Mycobacterium tuberculosis.

Efficacy of pneumococcal nontypable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in young Latin American children: A double-blind randomized controlled trial

BACKGROUND

The relationship between pneumococcal conjugate vaccine-induced antibody responses and protection against community-acquired pneumonia (CAP) and acute otitis media (AOM) is unclear. This study assessed the impact of the ten-valent pneumococcal nontypable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) on these end points. The primary objective was to demonstrate vaccine efficacy (VE) in a per-protocol analysis against likely bacterial CAP (B-CAP: radiologically confirmed CAP with alveolar consolidation/pleural effusion on chest X-ray, or non-alveolar infiltrates and C-reactive protein ≥ 40 µg/ml); other protocol-specified outcomes were also assessed.

METHODS AND FINDINGS

This phase III double-blind randomized controlled study was conducted between 28 June 2007 and 28 July 2011 in Argentine, Panamanian, and Colombian populations with good access to health care. Approximately 24,000 infants received PHiD-CV or hepatitis control vaccine (hepatitis B for primary vaccination, hepatitis A at booster) at 2, 4, 6, and 15-18 mo of age. Interim analysis of the primary end point was planned when 535 first B-CAP episodes, occurring ≥2 wk after dose 3, were identified in the per-protocol cohort. After a mean follow-up of 23 mo (PHiD-CV, n = 10,295; control, n = 10,201), per-protocol VE was 22.0% (95% CI: 7.7, 34.2; one-sided p = 0.002) against B-CAP (conclusive for primary objective) and 25.7% (95% CI: 8.4%, 39.6%) against World Health Organization-defined consolidated CAP. Intent-to-treat VE was 18.2% (95% CI: 5.5%, 29.1%) against B-CAP and 23.4% (95% CI: 8.8%, 35.7%) against consolidated CAP. End-of-study per-protocol analyses were performed after a mean follow-up of 28-30 mo for CAP and invasive pneumococcal disease (IPD) (PHiD-CV, n = 10,211; control, n = 10,140) and AOM (n = 3,010 and 2,979, respectively). Per-protocol VE was 16.1% (95% CI: -1.1%, 30.4%; one-sided p = 0.032) against clinically confirmed AOM, 67.1% (95% CI: 17.0%, 86.9%) against vaccine serotype clinically confirmed AOM, 100% (95% CI: 74.3%, 100%) against vaccine serotype IPD, and 65.0% (95% CI: 11.1%, 86.2%) against any IPD. Results were consistent between intent-to-treat and per-protocol analyses. Serious adverse events were reported for 21.5% (95% CI: 20.7%, 22.2%) and 22.6% (95% CI: 21.9%, 23.4%) of PHiD-CV and control recipients, respectively. There were 19 deaths (n = 11,798; 0.16%) in the PHiD-CV group and 26 deaths (n = 11,799; 0.22%) in the control group. A significant study limitation was the lower than expected number of captured AOM cases.

CONCLUSIONS

Efficacy was demonstrated against a broad range of pneumococcal diseases commonly encountered in young children in clinical practice.

TRIAL REGISTRATION

www.ClinicalTrials.gov NCT00466947.

Serological diagnostic assays for HIV-associated tuberculosis in sub-Saharan Africa?

In this issue of Clinical and Vaccine Immunology, Siev and colleagues present an evaluation of antibody responses to four immunodominant proteins of Mycobacterium tuberculosis in patients with HIV-associated pulmonary tuberculosis (TB) in South Africa (M. Siev, D. Wilson, S. Kainth, V. O. Kasprowicz, C. M. Feintuch, E. Jenny-Avital, and J. J. Achkar, 21:791-798, 2014, doi:http://dx.doi.org/10.1128/CVI.00805-13). This commentary discusses the enormous need for simple point-of-care assays for tuberculosis (TB) diagnosis in patients with and without HIV coinfection in high-burden settings and considers the potential role of serological assays and the huge challenges inherent in developing and validating such assays.

Development of an immunochromatographic test with anti-LipL32-coupled gold nanoparticles for Leptospira detection

Detection of antibody specific to Leptospira by various immunological techniques has been used for leptospirosis diagnosis. However, the sensitivity of antibody detection during the first few days after infection is low. Molecular techniques are suggested to provide earlier diagnosis than antibody detection, but a rapid and easy to perform assay for Leptospira antigen detection would provide an additional useful tool for disease diagnosis. In this study, we coupled gold nanoparticles with antibody to LipL32, a protein commonly found in pathogenic Leptospira. This coupled gold reagent was used in the immunochromatographic strip for Leptospira detection. We demonstrated that the sensitivity of Leptospira detection by this strip was 10(3) ml(-1). There was no positive result detected when strips were tested with non-pathogenic Leptospira, Staphylococcus aureus, Streptococcus group B, Acinetobacter baumannii, Escherichia coli, Salmonella typhi, Klebsiella pneumoniae, Enterococcus faecalis or Enterococcus faecium. These data suggest that gold nanoparticles coupled with antibody to LipL32 could be used for Leptospira detection by a rapid test based on an immunochromatographic technique.

Immunogenicity, impact on carriage and reactogenicity of 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine in Kenyan children aged 1-4 years: a randomized controlled trial

Background

The impact on carriage and optimal schedule for primary vaccination of older children with 10-valent pneumococcal non-typeable Haemophilus influenzae protein-D conjugate vaccine (PHiD-CV) are unknown.

Methods

600 Kenyan children aged 12–59 months were vaccinated at days 0, 60 and 180 in a double-blind randomized controlled trial according to the following vaccine sequence: Group A: PHiD-CV, PHiD-CV, diphtheria/tetanus/acellular pertussis vaccine (DTaP); Group B: PHiD-CV, DTaP, PHiD-CV; Group C: hepatitis A vaccine (HAV), DTaP, HAV. Nasopharyngeal carriage of Streptococcus pneumoniae was measured at five timepoints. In 375 subjects, serotype-specific responses were measured by 22F-inhibition ELISA and opsonophagocytic killing assays (OPA) one month after vaccination.

Results

Following one dose of PHiD-CV, >90% of recipients developed IgG≥0.35 µg/mL to serotypes 1, 4, 5, 7F, 9V and 18C and OPA≥8 to serotypes 4, 7F, 9V, 18C, 23F. After a second dose >90% of recipients had IgG≥0.35 µg/mL to all vaccine serotypes and OPA≥8 to all vaccine serotypes except 1 and 6B. At day 180, carriage of vaccine-type pneumococci was 21% in recipients of two doses of PHiD-CV (Group A) compared to 31% in controls (p = 0.04). Fever after dose 1 was reported by 41% of PHiD-CV recipients compared to 26% of HAV recipients (p<0.001). Other local and systemic adverse experiences were similar between groups.

Conclusions

Vaccination of children aged 12–59 months with two doses of PHiD-CV two to six months apart was immunogenic, reduced vaccine-type pneumococcal carriage and was well-tolerated. Administration of PHiD-CV would be expected to provide effective protection against vaccine-type disease.

Trial Registration

ClinicalTrials.gov NCT01028326

Achieving directed immunostimulating complexes incorporation

In recent years, several studies have been reported with the common aim of generating general expression systems for straightforward production and subsequent coupling of expressed antigens to an adjuvant system. Here, we describe a series of such efforts with a common theme of using gene fusion technology for association of recombinant antigens to immunostimulating complexes (iscoms). In the early stages of vaccine development, uniform antigen preparations are crucial to allow the comparison of immune responses to different antigens, or even subdomains thereof, and we believe that the described systems constitute an important development in this context.

Identification of a novel Haemophilus parasuis-specific B cell epitope using monoclonal antibody against the OppA protein

Monoclonal antibody (MAb) 1B3 against Haemophilus parasuis (H. parasuis) was generated by fusing SP2/0 murine myeloma cells and spleen cells from BALB/c mice immunized with the whole-bacterial-cell suspension of H. parasuis HS80 (serotype 5). The MAb 1B3 showed strong reactivity with 15 serotype reference strains of H. parasuis using Dot blot and Western blot analysis. Immunoprecipitation and protein spectral analysis indicated that MAb 1B3 recognized by Oligopeptide permease A (OppA) belongs to the ATP binding cassette transporter family. In addition, a linear B-cell epitope recognized by MAb 1B3 was identified by the screening of a phage-displayed 12-mer random peptide library. Sequence analysis showed that MAb 1B3 was recognized by phages-displaying peptides with the consensus motif KTPSEXR (X means variable amino acids). Its amino acid sequence matched (469)KTPAEAR(475) of H. parasuis OppA protein. A series of progressively truncated peptides were synthesized to define the minimal region that was required for MAb 1B3 binding. The epitope was highly conserved in OppA protein sequences from the isolated H. parasuis strains, which was confirmed by alignment analysis. Furthermore, the minimal linear epitope was highly specific among 75 different bacterial strains as shown in sequence alignments. These results indicated MAb 1B3 might be potentially used to develop serological diagnostic tools for H. parasuis.

Memory cytolytic T-lymphocytes: induction, regulation and implications for vaccine design

The design of vaccines that protect against intracellular infections or cancer remains a challenge. In many cases, immunity depends on the development of antigen-specific memory CD8+ T-cells that can express cytokines and kill antigen-bearing cells when they encounter the pathogen or tumor. Here, the authors review current understanding of the signals and cells that lead to memory CD8+ T-cell differentiation, the relationship between the primary CD8+ T-cell response and the memory response and the regulation of memory CD8+ T-cell survival and function. The implications of this new knowledge for vaccine design are discussed, and recent progress in the development of lipidated peptide vaccines as a promising approach for vaccination against intracellular infections and cancer is reviewed.

Computational antigenic epitope prediction by calculating electrostatic desolvation penalties of protein surfaces

The prediction of antigenic epitopes on the surface of proteins is of great importance for vaccine development and to specifically design recombinant antibodies. Computational methods based on the three-dimensional structure of the protein allow for the detection of noncontinuous epitopes in contrast to methods based on the primary amino-acid sequence only. A method recently developed to predict protein-protein binding sites is presented, and the application to predict putative antigenic epitopes is described in detail. The prediction approach is based on the local perturbation of the electrostatic field at the surface of a protein due to a neutral probe of low dielectric constant that represents an approaching binding partner. The calculated change in electrostatic energy corresponds to an energy penalty of desolvating a protein surface region, and antigenic epitope surface regions tend to be associated with a lower penalty compared to the average protein surface. The protocol to perform the calculations is described and illustrated on an example antigen, the outer surface protein A of Borrelia burgdorferi, a pathogenic organism causing lyme disease.

Immunogenicity, safety and reactogenicity of the 10-valent pneumococcal non-typeable haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in Nigerian Infants: a randomised trial

AIMS AND OBJECTIVES

The immunogenicity, reactogenicity and safety of the 10- valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) were evaluated in a cohort of Nigerian infants included in a study conducted in Mali and Nigeria (ClinicalTrials.gov identifier: NCT00678301).

SUBJECTS AND METHODS

In this open, randomised, controlled study, 119 healthy infants received combined diphtheria-tetanus-whole-cell pertussis-hepatitis B/ Haemophilus influenzae type b vaccine (DTPw-HBV/Hib) and oral poliovirus vaccine (OPV) co-administered with PHiD-CV (PHiD-CV group) or without PHiD-CV (control group) at 6-10-14 weeks of age. Pneumococcal antibody responses and opsonophagocytic activity were measured and adverse events were recorded.

RESULTS

One month post-dose 3, for each of the vaccine pneumococcal serotypes, e"90.1% of PHiD-CV recipients had an antibody concentration e"0.2 ug/mL compared to < 9 % (except for serotypes 14 [32.4%] and 19F [27.8%]) in the control group. For each of the vaccine pneumococcal serotypes, e"90.6% of infants in the PHiD-CV group had an OPA titre e"8, compared to % 18% (except for serotype 7F [60.0%]) in the control group. Anti-protein D antibody geometric mean antibody concentrations were 2949.7 EL.U/mL in the PHiD-CV group and 68.9 EL.U/mL in the control group. For each DTPw-HBV/Hib antigen antibody seroprotection/seropositivity rates were e"94.4%. Tolerability was generally comparable between the PHiD-CV and control vaccination groups.

CONCLUSIONS

PHiD-CV co-administered with routine vaccines was immunogenic for all vaccine pneumococcal serotypes and protein D in Nigerian infants. Vaccine tolerability was generally comparable between the PHiD-CV and control groups. These results suggest PHiD-CV can be co-administered with other vaccines included in the National Programme on Immunisation.

Evaluation of OspA vaccination-induced serological correlates of protection against Lyme borreliosis in a mouse model

BACKGROUND

For clinical development of a novel multivalent OspA vaccine against Lyme borreliosis, serological assays are required which can be used to establish immune correlates of protection against infection with Borrelia.

METHODS

Four assays (an OspA IgG ELISA, a competitive inhibition (CI) ELISA, a Borrelia surface-binding (SB) assay and a Borrelia killing assay) were used to evaluate the correlation between immune responses induced by rOspA 1/2 (a chimeric immunogen containing protective epitopes from OspA serotypes 1 and 2), and protective immunity against infection by B. burgdorferi s.s. (OspA-1) and B. afzelii (OspA-2). Mice were immunized with OspA 1/2 doses ranging from 0.3 ng to 100 ng, to induce a range of OspA antibody titers, and exposed to needle challenge with B. burgdorferi s.s. or tick challenge with B. afzelii. Receiver operator characteristics (ROC) curves were constructed for each assay, and the area under the curve (AUC), sensitivity, specificity and Youden Index were calculated. Potential cutoff antibody titers which could be used as correlates of vaccine-induced protection were derived from the maximum Youden Index.

RESULTS

Immunization with OspA-1/2 provided dose-dependent protection against infection with B. burgdorferi s.s. and B. afzelii. Antibody responses detected by all four assays were highly significantly correlated with protection from infection by either B. burgdorferi s.s. (p<0.0001 to 0.0062) or B. afzelii (p<0.0001). ROC analyses of the diagnostic effectiveness of each assay showed the AUC to range between 0.95 and 0.79, demonstrating that all assays distinguish well between infected and non-infected animals. Based on sensitivity, specificity and AUC, the OspA IgG ELISA and SB assays best discriminated between infected and non-infected animals.

CONCLUSIONS

All four assays differentiate well between Borrelia-infected and non-infected animals. The relatively simple, high throughput IgG ELISA would be suitable to establish immune correlates of protection for the novel OspA vaccine in clinical trials.

[Pseudomonas aeruginosa recombinant proteins: effect on mice cytokine profile]

AIM

Study cytokine-mediated immune response in mice vaccinated with Pseudomonas aeruginosa recombinant antigen preparations.

MATERIALS AND METHODS

Cytokine-mediated immune response was studied in mice vaccinated with membrane recombinant proteins OprF, OprL, a hybrid recombinant protein OprF-I consisting of sequences of OprF and OprI proteins and a recombinant atoxic form of exotoxin A with a deletion of 106 amino acid sequences (recombinant anatoxin - aTox) of P. aeruginosa.

RESULTS

An induction of a wide specter of studied cytokines was detected in the mice. The highest level was observed for IL-1 and IL-6 after administration of recombinant proteins OprL, OprF, OprF-1, aTox. OprF-I actively stimulated production of IL-2 that is a factor of growth and differentiation of lymphocytes, natural killers and cytotoxic lymphocytes; as well as IL-5, IL-O10, TNF-alpha and IFN-gamma. Recombinant protein OprF-I facilitated induction of IL-6, IL-17, TNF-alpha and IFN-gamma, whereas aTox - expression of IL-1, IL-2, IFN-gamma. Recombinant protein OprL induced IL-17 synthesis to the most extent and TNF-alpha and IL-10 - moderately.

CONCLUSION

The P. aeruginosa recombinant proteins obtained during intraperitoneal administration to mice facilitated formation of immune response with the direction of induction in both Thl and Th2 pathways.

Functional insights into recombinant TROSPA protein from Ixodes ricinus

Lyme disease (also called borreliosis) is a prevalent chronic disease transmitted by ticks and caused by Borrelia burgdorferi s. l. spirochete. At least one tick protein, namely TROSPA from I. scapularis, commonly occurring in the USA, was shown to be required for colonization of the vector by bacteria. Located in the tick gut, TROSPA interacts with the spirochete outer surface protein A (OspA) and initiates the tick colonization. Ixodes ricinus is a primary vector involved in B. burgdorferi s. l. transmission in most European countries. In this study, we characterized the capacities of recombinant TROSPA protein from I. ricinus to interact with OspA from different Borrelia species and to induce an immune response in animals. We also showed that the N-terminal part of TROSPA (a putative transmembrane domain) is not involved in the interaction with OspA and that reduction of the total negative charge on the TROSPA protein impaired TROSPA-OspA binding. In general, the data presented in this paper indicate that recombinant TROSPA protein retains the capacity to form a complex with OspA and induces a significant level of IgG in orally immunized rats. Thus, I. ricinus TROSPA may be considered a good candidate component for an animal vaccine against Borrelia.

ATP-binding cassette sterol transporters are differentially expressed in normal and diseased human gallbladder

BACKGROUND AND AIMS

Gallbladder epithelial cells (GBEC) are exposed to high cholesterol concentrations in bile, and export cholesterol via an ATP-binding cassette (ABC) transporter-mediated pathway in vitro. These findings suggest that aberrant expression and/or function of ABC sterol transporters may be associated with cholesterol-related gallbladder diseases (CAGD). In this study, we investigated the relative levels of the sterol transporters ABCA1, ABCG5, and ABCG8 in human gallbladders in CAGD, and the relationship between ABCA1 and inflammation.

METHODS

Expression of ABCA1, ABCG5, and ABCG8 was evaluated in 31 gallbladders with CAGD and 6 normal gallbladders by western blotting and immunohistochemistry. RT-PCR was used to measure ABCA1 mRNA expression. To investigate the relationship between ABCA1 and inflammation, wWestern blots were performed on cultured dog GBEC treated with lipopolysaccharide (LPS) using an anti-ABCA1 antibody.

RESULTS

Immunohistochemistry showed ABCA1 to be localized predominantly to the basolateral membrane, while ABCG8 formed a diffuse intracellular pattern at the apical pole of human GBEC. ABCA1 and ABCG8 expression was more prominent in GBEC that were surrounded by cholesterol-laden macrophages. ABCA1 and ABCG8 expression was increased in gallbladders with CAGD. Western blots showed increased ABCA1, ABCG5, and ABCG8 expression in CAGD. ABCA1 mRNA levels were increased in all gallbladders with CAGD. LPS treatment of cultured dog GBEC enhanced ABCA1 expression.

CONCLUSIONS

The sterol transporters ABCA1, ABCG5, and ABCG8 may play a role in the pathogenesis of human CAGD. Inflammation appears to be a key factor that increases ABCA1 expression and activity in the human gallbladder.

The effects of methionine acquisition and synthesis on Streptococcus pneumoniae growth and virulence

Bacterial pathogens need to acquire nutrients from the host, but for many nutrients their importance during infection remain poorly understood. We have investigated the importance of methionine acquisition and synthesis for Streptococcus pneumoniae growth and virulence using strains with gene deletions affecting a putative methionine ABC transporter lipoprotein (Sp_0149, metQ) and/or methionine biosynthesis enzymes (Sp_0585 - Sp_0586, metE and metF). Immunoblot analysis confirmed MetQ was a lipoprotein and present in all S. pneumoniae strains investigated. However, vaccination with MetQ did not prevent fatal S. pneumoniae infection in mice despite stimulating a strong specific IgG response. Tryptophan fluorescence spectroscopy and isothermal titration calorimetry demonstrated that MetQ has both a high affinity and specificity for L-methionine with a K_D of ∼25 nM, and a ΔmetQ strain had reduced uptake of C₁₄-methionine. Growth of the ΔmetQ/ΔmetEF strain was greatly impaired in chemically defined medium containing low concentrations of methionine and in blood but was partially restored by addition of high concentrations of exogenous methionine. Mixed infection models showed no attenuation of the ΔmetQ, ΔmetEF and ΔmetQ/ΔmetEF strains in their ability to colonise the mouse nasopharnyx. In a mouse model of systemic infection although significant infection was established in all mice, there were reduced spleen bacterial CFU after infection with the ΔmetQ/ΔmetEF strain compared to the wild-type strain. These data demonstrate that Sp_0149 encodes a high affinity methionine ABC transporter lipoprotein and that Sp_0585 – Sp_0586 are likely to be required for methionine synthesis. Although Sp_0149 and Sp_0585-Sp_0586 make a contribution towards full virulence, neither was essential for S. pneumoniae survival during infection.

In vivo magnetic enrichment, photoacoustic diagnosis, and photothermal purging of infected blood using multifunctional gold and magnetic nanoparticles

Bacterial infections are a primary cause of morbidity and mortality worldwide. Bacteremia is a particular concern owing to the possibility of septic shock and the development of metastatic infections. Treatment of bacteremia is increasingly compromised by the emergence of antibiotic resistant strains, creating an urgent need for alternative therapy. Here, we introduce a method for in vivo photoacoustic (PA) detection and photothermal (PT) eradication of Staphylococcus aureus in tissue and blood. We show that this method could be applicable for label-free diagnosis and treatment of in the bloodstream using intrinsic near-infrared absorption of endogenous carotenoids with nonlinear PA and PT contrast enhancement. To improve sensitivity and specificity for detection of circulating bacteria cells (CBCs), two-color gold and multilayer magnetic nanoparticles with giant amplifications of PA and PT contrasts were functionalized with an antibody cocktail for molecular targeting of S. aureus surface-associated markers such as protein A and lipoprotein. With a murine model, the utility of this approach was demonstrated for ultrasensitive detection of CBCs with threshold sensitivity as low as 0.5 CBCs/mL, in vivo magnetic enrichment of CBCs, PT eradication of CBCs, and real-time monitoring of therapeutic efficacy by CBC counting. Our PA-PT nano-theranostic platform, which integrates in vivo multiplex targeting, magnetic enrichment, signal amplification, multicolor recognition, and feedback control, could be used as a biological tool to gain insights on dissemination pathways of CBCs, infection progression by bacteria re-seeding, and sepsis development and treatment, and could potentially be feasible in humans, especially using bypass schematic.

Different patterns of expression and of IL-10 modulation of inflammatory mediators from macrophages of Lyme disease-resistant and -susceptible mice

C57BL/6J (C57) mice develop mild arthritis (Lyme disease-resistant) whereas C3H/HeN (C3H) mice develop severe arthritis (Lyme disease-susceptible) after infection with the spirochete Borrelia burgdorferi. We hypothesized that susceptibility and resistance to Lyme disease, as modeled in mice, is associated with early induction and regulation of inflammatory mediators by innate immune cells after their exposure to live B. burgdorferi spirochetes. Here, we employed multiplex ELISA and qRT-PCR to investigate quantitative differences in the levels of cytokines and chemokines produced by bone marrow-derived macrophages from C57 and C3H mice after these cells were exposed ex vivo to live spirochetes or spirochetal lipoprotein. Upon stimulation, the production of both cytokines and chemokines was up-regulated in macrophages from both mouse strains. Interestingly, however, our results uncovered two distinct patterns of spirochete- and lipoprotein-inducible inflammatory mediators displayed by mouse macrophages, such that the magnitude of the chemokine up-regulation was larger in C57 cells than it was in C3H cells, for most chemokines. Conversely, cytokine up-regulation was more intense in C3H cells. Gene transcript analyses showed that the displayed patterns of inflammatory mediators were associated with a TLR2/TLR1 transcript imbalance: C3H macrophages expressed higher TLR2 transcript levels as compared to those expressed by C57 macrophages. Exogenous IL-10 dampened production of inflammatory mediators, especially those elicited by lipoprotein stimulation. Neutralization of endogenously produced IL-10 increased production of inflammatory mediators, notably by macrophages of C57 mice, which also displayed more IL-10 than C3H macrophages. The distinct patterns of pro-inflammatory mediator production, along with TLR2/TLR1 expression, and regulation in macrophages from Lyme disease-resistant and -susceptible mice suggests itself as a blueprint to further investigate differential pathogenesis of Lyme disease.

Genetics of Borrelia burgdorferi

The spirochetes in the Borrelia burgdorferi sensu lato genospecies group cycle in nature between tick vectors and vertebrate hosts. The current assemblage of B. burgdorferi sensu lato, of which three species cause Lyme disease in humans, originated from a rapid species radiation that occurred near the origin of the clade. All of these species share a unique genome structure that is highly segmented and predominantly composed of linear replicons. One of the circular plasmids is a prophage that exists as several isoforms in each cell and can be transduced to other cells, likely contributing to an otherwise relatively anemic level of horizontal gene transfer, which nevertheless appears to be adequate to permit strong natural selection and adaptation in populations of B. burgdorferi. Although the molecular genetic toolbox is meager, several antibiotic-resistant mutants have been isolated, and the resistance alleles, as well as some exogenous genes, have been fashioned into markers to dissect gene function. Genetic studies have probed the role of the outer membrane lipoprotein OspC, which is maintained in nature by multiple niche polymorphisms and negative frequency-dependent selection. One of the most intriguing genetic systems in B. burgdorferi is vls recombination, which generates antigenic variation during infection of mammalian hosts.

[Epitope structure prediction of antigen B of Echinococcus granulosus and construction of multi-epitope recombinant antigen]

OBJECTIVE

To improve the reactivity of Echinococcus granulosus antigen B (EgAgB) multi-epitope antigens using the gene fragment from 3 subunits, EgAgB1, EgAgB2, and EgAgB4.

METHODS

Discovery Studio Visualizer software and I-TASSER on-line server were used to predict protein structure gene sequence of the 3 subunits and their combinations in different way. The epitope or subunit combination higher prediction scores was selected for gene recombination. The target sequence was amplified with primers and by using overlap extension PCR technology. The target sequence was then cloned to pET32a constructing expression plasmid and expressing recombinant proteins. The expressed products were served recombinant antigens after purification. The immuno-response of the recombinant multi-epitope antigens were Western blotting analysis.

RESULTS

Structure prediction showed that all the three subunits EgAgB1, EgAgB4 are in a "Z" word structure. The epitope region is located in the central part of the sequence. For from the three subunits and four reactive epitopes (KK36, RK30, B4-2, and B4-3), 57 different combinations tried for structure prediction. Six of them were selected for recombination and expression. Western blotting six multi-epitope antigens (MEA-8, MEA-20, MEA-26, MEA-36, MEA-49, and MEA-52) suggested reactivity of multi-epitope antigen was much stronger than AgB subunit antigens when the positive echinococcosis were used.

CONCLUSION

By using protein tertiary structural prediction and screening the higher prediction score of combinations, six multi-epitope recombinant antigens were constructed. Western blotting shows that the hand reactivity of multi-epitope antigen is much stronger than that of AgB subunit antigens.

The immunomodulatory activity of meningococcal lipoprotein Ag473 depends on the conformation made up of the lipid and protein moieties

We have previously demonstrated that the meningococcal antigen Ag473 in the presence of Freund’s adjuvant can elicit protective immune responses in mouse challenge model. In this study, we evaluated the structural requirement for the immunological activity and the possible signaling pathway of recombinant Ag473 antigen produced in E. coli. We found that lipidated Ag473 (L-Ag473) possesses an intrinsic adjuvant activity that could be attributed to its ability to activate dendritic cells and promote their maturation. In addition, we found that L-Ag473 can activate human monocytes and promote maturation of human monocyte-derived dendritic cells. These results provide an indirect support that L-Ag473 may also be immunogenic in human. Interestingly, the observed activity is dependent on the overall conformation of L-Ag473 because heating and proteinase K treatment can diminish and abolish the activity. Furthermore, our data suggest a species-differential TLR recognition of L-Ag473. Overall, these data suggest a new paradigm for the ligand-TLR interaction in addition to demonstrating the self-adjuvanting activity of the vaccine candidate L-Ag473.

Tissue factor pathway inhibitor is an inhibitor of factor VII-activating protease

BACKGROUND

Factor VII-activating protease (FSAP) is a serine protease that circulates in plasma in its inactive single-chain form and can be activated upon contact with dead cells. When activated by apoptotic cells, FSAP leads to the release of nucleosomes. The serpins C1-inhibitor and α(2) -antiplasmin are reported to be the major inhibitors of FSAP. However, regulation of FSAP activity by Kunitz-type inhibitors is not well studied.

OBJECTIVES

To compare the inhibition of FSAP activity and FSAP-induced nucleosome release from apoptotic cells by tissue factor pathway inhibitor (TFPI) with that of C1-inhibitor and α(2) -antiplasmin.

METHODS

Apoptotic cells were incubated with plasma or FSAP in presence of the inhibitor, and nucleosome release was analyzed with flow cytometry. Monoclonal antibodies against TFPI and altered forms of TFPI were used to investigate which domains of TFPI contribute to FSAP inhibition.

RESULTS AND CONCLUSIONS

We show that TFPI abrogates FSAP activity and nucleosome release from apoptotic cells. TFPI is a much more efficient inhibitor than C1-inhibitor or α(2) -antiplasmin. The active site of K2 is required for inhibition of FSAP. A direct binding interaction between FSAP and the C-terminal domain of TFPI is also required for efficient inhibition. Inhibition of FSAP-induced nucleosome release by recombinant TFPI might, in part, explain the anti-inflammatory effects of recombinant TFPI infusion observed in animal and human sepsis.

[Production of hybrid protein OprF-OprL of Pseudomonas aeruginosa]

AIM

Production of preparation consisting of amino acid sequences of 2 proteins of outer membrane--OprF and OprI--of P. aeruginosa and study of its protective properties from experimental P. aeruginosa infection.

MATERIALS AND METHODS

Nucleotide sequences coding OprF protein (1 kb) as well as its C-terminal region (0.6 kb) and OprI protein (0.25 kb) were integrated into pQE-30 plasmid (QIAGEN). And oprF gene (C-terminal region of oprF in variant 2) and oprI gene were combined and cloned sequentially into a single vector. E. coli M15 strain cells (QIAGEN) were used for the production of producent strains of recombinant proteins. Protein products were analyzed by electrophoresis in polyacrylamide gel by Lammle. Purification of recombinant proteins was performed by affinity chromatography in Ni-sepharose columns. Live virulent culture P. aeruginosa PA-170015 strain was used for the analysis of protective properties of recombinant proteins.

RESULTS

2 hybrid recombinant proteins were produced including amino acid sequences of F and I proteins of outer membrane (OprF and OprI) of P. aeruginosa. Recombinant protein 1 included whole size sequences of OprF and OprI and protein 2--C-terminal region (including amino acid residues 192-342) of OprF and whole size sequence of OprI. These recombinant proteins after 2 immunizations protected mice from the experimental intraperitoneal infection with P. aeruginosa. Hybrid protein consisting of whole size sequences had the best protective effect.

CONCLUSION

The results obtained open a perspective for further immunobiological testing of hybrid recombinant protein OprF-OprI with the aim of creating immunopreparations for prophylaxis of P. aeruginosa infection.

[Mechanisms of the liver anti-endotoxin defence]

Current knowledge of immunocellular and lipoprotein mechanisms of the liver-induced anti-endotoxin tolerance has been summarized. The role of T regulatory cells, different macrophage phenotypes, high density lipoproteins, oxidized low density lipoproteins and their receptors as the key players in mechanism of tolerance to endotoxin has been discussed.

NMR resonance assignment of the autoimmunity protein SpaI from Bacillus subtilis ATCC 6633

Bacillus subtilis ATCC 6633 produces the lipid II targeting lantibiotic subtilin. For self-protection these gram-positive bacteria express a cluster of four self-immunity proteins named SpaIFEG. SpaI is a 16.8 kDa lipoprotein which is attached to the outside of the cytoplasmic membrane via a covalently linked diacylglycerol anchor. Together with the ABC-transporter SpaFEG, SpaI protects the membrane from subtilin insertion and there is evidence for a direct interaction of SpaI with subtilin. As a prerequisite for further structural studies of SpaI and the SpaI/subtilin complex we report here the full (1)H, (15)N, (13)C chemical shift assignment for a stable 14.9 kDa C-terminal fragment of SpaI.

Immunofixation electrophoresis for identification of proteins and specific antibodies

Immunofixation electrophoresis (IFE) is a technique for the identification of proteins within complex mixtures after separation by either conventional zone electrophoresis or isoelectric focusing. Most commonly antigens (which are often immunoglobulins) are separated by electrophoresis followed by precipitation with specific antibodies in situ. However, immunoglobulins with specific reactivity can be also precipitated with the proper antigens after electrophoresis in reverse or reversed IFE. Because of its great versatility, potentially high sensitivity, ease to perform and customize, and relatively low cost with no requirement for expensive instrumentation, manual IFE remains a valuable tool for both clinical diagnostic testing and research. Any low-viscosity body fluid specimen or, possibly, culture fluid could be tested with IFE if proper antibodies (or antigens in reverse[d] IFE) are available. After pretreatment with chaotropic and/or reducing agents, even high-viscosity specimens might be amenable to testing with IFE.

Inactivation of the gene encoding zinc-binding lipoprotein 103 impairs the infectivity of Streptococcus suis

The Streptococcus suis 103 gene product is an immunogenic and protective lipoprotein that is a component of an ATP-binding cassette transporter implicated in zinc uptake. Belonging to the same transcriptional unit and downstream of the 103 gene is a gene that encodes a homologue of the pneumococcal histidine triad (Pht) protein Pht309. In an intraperitoneal mouse model the virulence of a mutant lacking the 103 gene was more than 50 times lower than that of the wild-type (WT) parent strain, S. suis serotype 2 strain P1/7. In addition, the immunogenicity of this mutant was dramatically decreased. In striking contrast, the virulence and immunogenicity of a P1/7 mutant lacking the Pht309 gene were similar to those of the parent strain. These results demonstrate that the 103 lipoprotein is strongly involved in S. suis virulence and support the hypothesis that this lipoprotein might be an excellent candidate for vaccines aiming to achieve broad protection against streptococci.

Epitope mapping of antibodies to VlsE protein of Borrelia burgdorferi in post-Lyme disease syndrome

The VlsE lipoprotein of Borrelia burgdorferi elicits a strong immune response during the course of Lyme disease. The present study was aimed at characterization of the epitopes of VlsE targeted by the antibody response in patients with post-Lyme disease syndrome, a condition characterized by persisting symptoms of pain, fatigue, and/or neurocognitive impairment despite antibiotic treatment of B. burgdorferi infection. Epitope mapping was carried out using microarrays that contained synthesized overlapping peptides covering the full sequence of VlsE from B. burgdorferi B31. In addition to the previously characterized IR6 region in the variable domain, specific sequences in the N- and C-terminal invariable domains of VlsE were found to be major B cell epitopes in affected patients. The crystal structure of VlsE indicated that the newly described epitopes form a contiguous region in the surface-exposed membrane-proximal part of the monomeric form of the protein.

Food anaphylaxis in antiphospholipid syndrome and thrombosis

BACKGROUND

We have observed that some cases of food anaphylaxis were followed by severe thrombosis associated to anticardiolipin antibodies. Food anaphylaxis associated with antiphospholipid syndrome has seldom been published.

OBJECTIVE

The aims were: 1) to test anticardiolipin antibodies in an important number of patients with anaphylaxis due to vegetal foods and their relationship with possible thrombosis; and 2) to study seed and fruit hypersensitivity in patients with previous thrombotic events associated with antiphospholipid antibodies (aCL).

METHODS

We included 30 patients diagnosed of thrombosis associated with aCL, 52 patients who suffered from anaphylaxis due to seeds or fruits, and 120 control patients. Haematological, cardiopulmonary vascular and rheumatologic studies had been performed as needed. In vivo and in vitro allergy tests with a large battery of vegetal allergens were carried out in all the patients. Measurement of IgG aCL antibodies and specific IgE to vegetal food was done by ELISA and CAP-FEIA (Phadia). Immunodetection and inhibitions with lipoproteins belonging to seeds were performed.

RESULTS

Seventy-five percent of the patients diagnosed as having antiphospholipid primary syndrome had specific IgE against different proteins from different vegetable allergens, most of them seeds, and clearly against lipoproteins that were also recognised by the patients with food anaphylaxis but not by the control cases. Among the patients with anaphylaxis, 28% had anticardiolipin antibodies and 17.3% thrombosis.

CONCLUSION

Our study suggests that seed lipoproteins which cause severe food anaphylaxis might have a potential role in the antiphospholipid syndrome and related thrombosis.

Proinflammatory response of human endothelial cells to Brucella infection

Although vascular pathologies such as vasculitis, endocarditis and mycotic aneurysms have been described in brucellosis patients, the interaction of Brucella with the endothelium has not been characterized. In this study we show that Brucella abortus and Brucella suis can infect and replicate in primary human umbilical vein endothelial cells (HUVEC) and in the microvascular endothelial cell line HMEC-1. Infection led to an increased production of IL-8, MCP-1 and IL-6 in HUVEC and HMEC-1 cells, and an increased expression of adhesion molecules (CD54 in both cells, CD106 and CD62E in HUVEC). Experiments with purified antigens from the bacterial outer membrane revealed that lipoproteins (Omp19) but not lipopolysaccharide mediate these proinflammatory responses. Infection of polarized HMEC-1 cells resulted in an increased capacity of these cells to promote the transmigration of neutrophils from the apical to the basolateral side of the monolayer, and the same phenomenon was observed when the cells were stimulated with live bacteria from the basolateral side. Overall, these results suggest that Brucella spp. can infect and survive within endothelial cells, and can induce a proinflammatory response that might be involved in the vascular manifestations of brucellosis.

[Study on the nuclear translocation mechanism in the inhibition of nuclear factor-ΚB activation in bacterial lipoprotein-tolerant THP-1 cells]

OBJECTIVE

To approach the nuclear factor-ΚB (NF-ΚB) nuclear translocation mechanism in bacterial lipoprotein (BLP) tolerance.

METHODS

Human monocytic THP-1 cells were first pretreated with 10, 100, 1 000 ng/ml BLP for 20 hours to induce BLP tolerance. Then THP-1 cells without BLP pretreatment (control group) or with BLP pretreatment (tolerance group) were stimulated with 0, 10, 100, 1 000 ng/ml BLP again for 6 hours. The tumor necrosis factor-α (TNF-α) content in culture medium was measured by enzyme linked immunosorbent assay (ELISA) in order to determine the most suitable BLP pretreatment and stimulation concentration. Western blotting was used to detect the protein level, nuclear translocation and phosphorylation of NF-ΚB p50 and p65 in the cells of control and tolerance groups treated with respective conditions for 0, 0.5, 1, 2 and 6 hours.

RESULTS

In control group BLP stimulation (10, 100, 1 000 ng/ml) could induce THP-1 activation and TNF-α production (pg/ml: 184.86±32.51, 3 215.88±167.09, 6 042.96±245.37) in a dose-dependent manner. In tolerance group, 100 ng/ml BLP pretreatment resulted in almost complete inhibition of TNF-α production as induced by 101 000 ng/ml BLP stimulation. Therefore, 100 ng/ml BLP pretreatment and 1 000 ng/ml stimulation were selected for following cell treatment. Western blotting analysis showed that there was an increase of p50 protein level in BLP-tolerant cells comparing with control group (0 hour: 542.9±15.6 vs. 272.8±13.2, 0.5 hour: 558.0±16.9 vs. 236.4±11.8, 1 hour: 524.7±17.5 vs. 211.6±9.8, 2 hours: 584.9±15.6 vs. 222.4±12.3, all P<0.01), whereas the p65 protein level was similar between the two groups. BLP stimulation also induced the nuclear translocation of p50 and p65 in control group (1-hour p50: 344.2±13.6 vs. 79.0±5.2, p65: 78.4±4.5 vs. 0, both P<0.05), but not in tolerance group. In addition, the phosphorylation of p65 at serine 536 was induced after BLP stimulation in control THP-1 cells (0.5 hour: 0.67±0.08 vs. 0.04±0.01, 1 hour: 0.71±0.11 vs. 0.04±0.01, both P<0.05), but this change was not detected in BLP-tolerant cells.

CONCLUSION

It was found that in BLP-tolerant cells, the expression of inhibitory subunit p50 was increased and the nuclear translocation and phosphorylation of p65 with trans-activation ability was inhibited. These changes are likely responsible for the reduced gene expression of NF-ΚB dependent genes in BLP-tolerant cells.

[Echinococcus granulosus recombinant antigen B induced IDO expression in mouse bone marrow-derived dendritic cells in vitro]

OBJECTIVE

To observe the expression of indoleamine 2,3-dioxygenase (IDO) in mouse bone marrow-derived dendritic cells (DCs) after adding Echinococcus granulosus recombinant antigen B (rAgB) in vitro.

METHODS

CD11c+ DCs generated from bone marrow precursor cells of C57BL/6 mice and cultured in the presence of recombinant mouse GM-CSF (rmGM-CSF). The morphology of DCs was observed by inverted microscope and scanning electronic microscope. The level of I-A/I-E, CD40, CD80, and CD86 on DCs were determined by flow cytometry. T cell proliferation induced by DCs were evaluated by using mixed lymphocyte reaction (MLR) assay. At day 6 post culture, the immature DCs were collected, and part of the immature DCs stimulated with lipopolysaccharide (LPS) for 24 h were examined by flow cytometry. Immature DCs were divided into 3 groups: negative control group, positive control group (rmIFN-gamma, 1000 U/ml) and rAgB group. Immature DCs of positive control group and rAgB group were induced with 1000 U/ml rmIFN-gamma and 15 microg/ml rAgB, respectively. IDO expression in DCs was examined 24 h after induction using immunohistochemical method and Western blotting.

RESULTS

More than 80% CD11c+ DCs were harvested. The typical DCs were observed under inverted microscope and scanning electronic microscope. The level of CD40, CD80, and IA/IE (MHC II) in mature DCs group was significantly higher than that of immature DCs group (P < 0.05). In MLR, mitomycin-treated DCs can stimulate T lymphocytes proliferation activity. There were significantly differences in IDO expression in the negative control group [(4.544 +/- 1.752)%], positive control group [(20.464 +/- 4.452)%] and rAgB group [(11.148 +/- 1.966)%] (P < 0.05). Western blotting result indicated that the ratio of IDO/GAPDH in rAgB group (0.573 +/- 0.129) was significantly higher than that of negative group (0.229 +/- 0.085) (P < 0.05), and there were no significant difference in the ratio of IDO/GAPDH between IFN-gamma group (0.794 +/- 0.114) and rAgB group (P > 0.05).

CONCLUSION

rAgB can induce IDO expression in bone marrow-derived dendritic cells in vitro.

The tissue factor pathway inhibitor 1 of Sciaenops ocellatus possesses antimicrobial activity and is involved in the immune response against bacterial infection

Tissue factor pathway inhibitor 1 (TFPI-1) is a Kunitz-type serine protease inhibitor that regulates the activation of tissue factor-induced coagulation. In teleosts, TFPI-1-like sequences have been found to exist in two species (Danio rerio and Cyprinus carpio); however, the potential function of fish TFPI-1 has not been investigated. In this study, we identified and analyzed a TFPI-1 homologue, SoTFPI-1, from red drum (Sciaenops ocellatus). The deduced amino acid sequence of SoTFPI-1 is 284 residues in length and contains three Kunitz domains, an acidic N-terminus, and a basic C-terminus. SoTFPI-1 shares 49.5% and 46.9% overall sequence identities with the TFPI-1 of D. rerio and C. carpio, respectively. Quantitative real time RT-PCR analysis showed that constitutive SoTFPI-1 expression occurred, in increasing order, in kidney, brain, liver, gill, blood, spleen, muscle, and heart. Bacterial infection and lipopolysaccharide exposure upregulated SoTFPI-1 expression in kidney in time-dependent manners. Recombinant SoTFPI-1 (rSoTFPI-1) purified from Escherichia coli exhibits not only serine protease inhibitor activity but also bactericidal activity in a manner that is independent of any host factors. A synthetic peptide, TO17, corresponding to the C-terminal basic region of SoTFPI-1 also possesses antibacterial effect that is more potent than that of the full-length rSoTFPI-1. Taken together, these results demonstrate that (i) SoTFPI-1 is a biologically active serine protease inhibitor endowed with bactericidal property; (ii) provide the first indication that teleost TFPI-1 is likely to be involved in anti-microbial infection and thus is linked to innate immune defense.

Invasion and destruction of a murine fibrosarcoma by Salmonella-induced effector CD8 T cells as a therapeutic intervention against cancer

We have developed a new vaccination strategy by using the Salmonella type III secretion system (T3SS) to translocate heterologous antigens into the cytosol of host cells. This leads to an efficient antigen-specific CD8 T cell induction. Recently, we have demonstrated the use of Salmonella's T3SS for the immunoprophylaxis of a solid tumor. The murine fibrosarcoma WEHI 164 was transfected with the DNA sequence encoding the MHC class I-peptide p60(217-225) from Listeria monocytogenes. In the present study, we used this tumor model to investigate the potential of vaccination with recombinant Salmonella in a therapeutic setting. BALB/c mice were subcutaneously challenged with WEHI-p60 cells. Simultaneously or 4 days later, these mice received either an orogastric or intravenous immunization with Salmonella translocating p60. Interestingly, 71-80% of the intravenously and 50-52% of the orogastrically immunized mice showed a complete tumor regression after 14 days. In addition, the distribution of tetramer-positive p60(217-225)-specific CD8 T cell subpopulations in blood and tumor tissue was analyzed. Co-staining with CD62L and CD127 revealed that the frequencies of p60(217-225)-specific effector and effector memory CD8 T cells in blood and in fibrosarcoma tissue were related to the kinetics of tumor regression. In summary, our study demonstrates that therapeutic vaccination with Salmonella leads to efficient induction of tumor-invading effector CD8 T cells that may result in significant tumor regression.

The peptide sequence of diacyl lipopeptides determines dendritic cell TLR2-mediated NK activation

Natural killer (NK) cells are lymphocyte effectors that are activated to control certain microbial infections and tumors. Many NK-activating and regulating receptors are involved in regulating NK cell function. In addition, activation of naïve NK cells is fundamentally triggered by cytokines or myeloid dendritic cells (mDC) in various modes. In this study, we synthesized 16 S-[2,3-bis(palmitoyl)propyl]cysteine (Pam2Cys) lipopeptides with sequences designed from lipoproteins of Staphylococcus aureus, and assessed their functional properties using mouse (C57BL/6) bone marrow-derived DC (BMDC) and NK cells. NK cell activation was evaluated by three criteria: IFN-γ production, up-regulation of NK activation markers and cytokines, and NK target (B16D8 cell) cytotoxicity. The diacylated lipopeptides acted as TLR2 ligands, inducing up-regulation of CD25/CD69/CD86, IL-6, and IL-12p40, which represent maturation of BMDC. Strikingly, the Pam2Cys lipopeptides induced mouse NK cell activation based on these criteria. Cell-cell contact by Pam2Cys peptide-stimulated BMDC and NK cells rather than soluble mediators released by stimulated BMDC induced activation of NK cells. For most lipopeptides, the BMDC TLR2/MyD88 pathway was responsible for driving NK activation, while some slightly induced direct activation of NK cells via the TLR2/MyD88 pathway in NK cells. The potential for NK activation was critically regulated by the peptide primary sequence. Hydrophobic or proline-containing sequences proximal to the N-terminal lipid moiety interfered with the ability of lipopeptides to induce BMDC-mediated NK activation. This mode of NK activation is distinctly different from that induced by polyI:C, which is closely associated with type I IFN-inducing pathways of BMDC. These results imply that the MyD88 pathway of BMDC governs an alternative NK-activating pathway in which the peptide sequence of TLR2-agonistic lipopeptides critically affects the potential for NK activation.

Immune response to Lactobacillus plantarum expressing Borrelia burgdorferi OspA is modulated by the lipid modification of the antigen

BACKGROUND

Over the past decade there has been increasing interest in the use of lactic acid bacteria as mucosal delivery vehicles for vaccine antigens, microbicides and therapeutics. We investigated the mechanism by which a mucosal vaccine based in recombinant lactic acid bacteria breaks the immunological tolerance of the gut in order to elicit a protective immune response.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed how the lipid modification of OspA affects the localization of the antigen in our delivery vehicle using a number of biochemistry techniques. Furthermore, we examined how OspA-expressing L. plantarum breaks the oral tolerance of the gut by stimulating human intestinal epithelial cells, peripheral blood mononuclear cells and monocyte derived dendritic cells and measuring cytokine production. We show that the leader peptide of OspA targets the protein to the cell envelope of L. plantarum, and it is responsible for protein export across the membrane. Mutation of the lipidation site in OspA redirects protein localization within the cell envelope. Further, we show that lipidated-OspA-expressing L. plantarum does not induce secretion of the pro-inflammatory cytokine IL-8 by intestinal epithelial cells. In addition, it breaks oral tolerance of the gut via Th1/Th2 cell mediated immunity, as shown by the production of pro- and anti-inflammatory cytokines by human dendritic cells, and by the production of IgG2a and IgG1 antibodies, respectively.

CONCLUSIONS/SIGNIFICANCE

Lipid modification of OspA expressed in L. plantarum modulates the immune response to this antigen through a Th1/Th2 immune response.