Publications by authors named "Ilaria Ferlenghi"

35 Publications

Stability of Outer Membrane Vesicles-Based Vaccines, Identifying the Most Appropriate Methods to Detect Changes in Vaccine Potency.

Vaccines (Basel) 2021 Mar 6;9(3). Epub 2021 Mar 6.

GSK Vaccines Institute for Global Health (GVGH) S.r.l., Via Fiorentina 1, 53100 Siena, Italy.

Ensuring the stability of vaccines is crucial to successfully performing global immunization programs. Outer Membrane Vesicles (OMV) are receiving great attention as vaccine platforms. OMV are complex molecules and few data have been collected so far on their stability. OMV produced by bacteria, genetically modified to increase their spontaneous release, simplifying their production, are also known as Generalized Modules for Membrane Antigens (GMMA). We have performed accelerated stability studies on GMMA from different pathogens and verified the ability of physico-chemical and immunological methods to detect possible changes. High-temperature conditions (100 °C for 40 min) did not affect GMMA stability and immunogenicity in mice, in contrast to the effect of milder temperatures for a longer period of time (37 °C or 50 °C for 4 weeks). We identified critical quality attributes to monitor during stability assessment that could impact vaccine efficacy. In particular, specific recognition of antigens by monoclonal antibodies through competitive ELISA assays may replace in vivo tests for the potency assessment of GMMA-based vaccines.
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http://dx.doi.org/10.3390/vaccines9030229DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998687PMC
March 2021

Proteome-minimized outer membrane vesicles from as a generalized vaccine platform.

J Extracell Vesicles 2021 Feb 16;10(4):e12066. Epub 2021 Feb 16.

Department of Cellular, Computational and Integrative Biology (CIBIO) Laboratory of Synthetic and Structural Vaccinology University of Trento Trento Italy.

Because of their potent adjuvanticity, ease of manipulation and simplicity of production Gram-negative Outer Membrane Vesicles OMVs have the potential to become a highly effective vaccine platform. However, some optimization is required, including the reduction of the number of endogenous proteins, the increase of the loading capacity with respect to heterologous antigens, the enhancement of productivity in terms of number of vesicles per culture volume. In this work we describe the use of Synthetic Biology to create BL21(DE3)Δ60, a strain releasing OMVs (OMVs) deprived of 59 endogenous proteins. The strain produces large quantities of vesicles (> 40 mg/L under laboratory conditions), which can accommodate recombinant proteins to a level ranging from 5% to 30% of total OMV proteins. Moreover, also thanks to the absence of immune responses toward the inactivated endogenous proteins, OMVs decorated with heterologous antigens/epitopes elicit elevated antigens/epitopes-specific antibody titers and high frequencies of epitope-specific IFN-γ-producing CD8 T cells. Altogether, we believe that BL21(DE3)Δ60 have the potential to become a workhorse factory for novel OMV-based vaccines.
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http://dx.doi.org/10.1002/jev2.12066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7886703PMC
February 2021

Rational design of adjuvants for subunit vaccines: The format of cationic adjuvants affects the induction of antigen-specific antibody responses.

J Control Release 2021 Feb 2;330:933-944. Epub 2020 Nov 2.

Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK. Electronic address:

A range of cationic delivery systems have been investigated as vaccine adjuvants, though few direct comparisons exist. To investigate the impact of the delivery platform, we prepared four cationic systems (emulsions, liposomes, polymeric nanoparticles and solid lipid nanoparticles) all containing equal concentrations of the cationic lipid dimethyldioctadecylammonium bromide in combination with the Neisseria adhesin A variant 3 subunit antigen. The formulations were physicochemically characterized and their ability to associate with cells and promote antigen processing (based on degradation of DQ-OVA, a substrate for proteases which upon hydrolysis is fluorescent) was compared in vitro and their vaccine efficacy (antigen-specific antibody responses and IFN-γ production) and biodistribution (antigen and adjuvant) were evaluated in vivo. Due to their cationic nature, all delivery systems gave high antigen loading (> 85%) with liposomes, lipid nanoparticles and emulsions being <200 nm, whilst polymeric nanoparticles were larger (~350 nm). In vitro, the particulate systems tended to promote cell uptake and antigen processing, whilst emulsions were less effective. Similarly, whilst the particulate delivery systems induced a depot (of both delivery system and antigen) at the injection site, the cationic emulsions did not. However, out of the systems tested the cationic emulsions induced the highest antibody responses. These results demonstrate that while cationic lipids can have strong adjuvant activity, their formulation platform influences their immunogenicity.
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http://dx.doi.org/10.1016/j.jconrel.2020.10.066DOI Listing
February 2021

Synergic complement-mediated bactericidal activity of monoclonal antibodies with distinct specificity.

FASEB J 2020 08 17;34(8):10329-10341. Epub 2020 Jun 17.

GSK, Siena, Italy.

The classical complement pathway is triggered when antigen-bound immunoglobulins bind to C1q through their Fc region. While C1q binds to a single Fc with low affinity, a higher avidity stable binding of two or more of C1q globular heads initiates the downstream reactions of the complement cascade ultimately resulting in bacteriolysis. Synergistic bactericidal activity has been demonstrated when monoclonal antibodies recognize nonoverlapping epitopes of the same antigen. The aim of the present work was to investigate the synergistic effect between antibodies directed toward different antigens. To this purpose, we investigated the bactericidal activity induced by combinations of monoclonal antibodies (mAbs) raised against factor H-binding protein (fHbp) and Neisserial Heparin-Binding Antigen (NHBA), two major antigens included in Bexsero, the vaccine against Meningococcus B, for prevention from this devastating disease in infants and adolescents. Collectively, our results show that mAbs recognizing different antigens can synergistically activate complement even when each single Mab is not bactericidal, reinforcing the evidence that cooperative immunity induced by antigen combinations can represent a remarkable added value of multicomponent vaccines. Our study also shows that the synergistic effect of antibodies is modulated by the nature of the respective epitopes, as well as by the antigen density on the bacterial cell surface.
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http://dx.doi.org/10.1096/fj.201902795RDOI Listing
August 2020

Delivery of self-amplifying mRNA vaccines by cationic lipid nanoparticles: The impact of cationic lipid selection.

J Control Release 2020 09 1;325:370-379. Epub 2020 Jul 1.

Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral St., G4 0RE Glasgow, Scotland, United Kingdom. Electronic address:

Self-amplifying RNA (SAM) represents a versatile tool that can be used to develop potent vaccines, potentially able to elicit strong antigen-specific humoral and cellular-mediated immune responses to virtually any infectious disease. To protect the SAM from degradation and achieve efficient delivery, lipid nanoparticles (LNPs), particularly those based on ionizable amino-lipids, are commonly adopted. Herein, we compared commonly available cationic lipids, which have been broadly used in clinical investigations, as an alternative to ionizable lipids. To this end, a SAM vaccine encoding the rabies virus glycoprotein (RVG) was used. The cationic lipids investigated included 3ß-[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol), dimethyldioctadecylammonium (DDA), 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 1,2-dimyristoyl-3-trimethylammonium-propane (DMTAP), 1,2-stearoyl-3-trimethylammonium-propane (DSTAP) and N-(4-carboxybenzyl)-N,N-dimethyl-2,3-bis(oleoyloxy)propan-1-aminium (DOBAQ). Whilst all cationic LNP (cLNP) formulations promoted high association with cells in vitro, those formulations containing the fusogenic lipid 1,2-dioleoyl-sn-3-phosphoethanolamine (DOPE) in combination with DOTAP or DDA were the most efficient at inducing antigen expression. Therefore, DOTAP and DDA formulations were selected for further in vivo studies and were compared to benchmark ionizable LNPs (iLNPs). Biodistribution studies revealed that DDA-cLNPs remained longer at the injection site compared to DOTAP-cLNPs and iLNPs when administered intramuscularly in mice. Both the cLNP formulations and the iLNPs induced strong humoral and cellular-mediated immune responses in mice that were not significantly different at a 1.5 µg SAM dose. In summary, cLNPs based on DOTAP and DDA are an efficient alternative to iLNPs to deliver SAM vaccines.
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http://dx.doi.org/10.1016/j.jconrel.2020.06.027DOI Listing
September 2020

Mannosylation of LNP Results in Improved Potency for Self-Amplifying RNA (SAM) Vaccines.

ACS Infect Dis 2019 09 23;5(9):1546-1558. Epub 2019 Jul 23.

GSK , Via Fiorentina 1 , 53100 Siena , Italy.

Mannosylation of Lipid Nanoparticles (LNP) can potentially enhance uptake by Antigen Presenting Cells, which are highly abundant in dermal tissues, to improve the potency of Self Amplifying mRNA (SAM) vaccines in comparison to the established unmodified LNP delivery system. In the current studies, we evaluated mannosylated LNP (MLNP), which were obtained by incorporation of a stable Mannose-cholesterol amine conjugate, for the delivery of an influenza (hemagglutinin) encoded SAM vaccine in mice, by both intramuscular and intradermal routes of administration. SAM MLNP exhibited enhanced uptake in comparison to unglycosylated LNP from bone marrow-derived dendritic cells, and more rapid onset of the antibody response, independent of the route. The increased binding antibody levels also translated into higher functional hemagglutinin inhibition titers, particularly following intradermal administration. T cell assay on splenocytes from immunized mice also showed an increase in antigen specific CD8 T responses, following intradermal administration of MLNP SAM vaccines. Induction of enhanced antigen specific CD4 T cells, correlating with higher IgG2a antibody responses, was also observed. Hence, the present work illustrates the benefit of mannosylation of LNPs to achieve a faster immune response with SAM vaccines and these observations could contribute to the development of novel skin delivery systems for SAM vaccines.
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http://dx.doi.org/10.1021/acsinfecdis.9b00084DOI Listing
September 2019

Structural basis for cooperativity of human monoclonal antibodies to meningococcal factor H-binding protein.

Commun Biol 2019 26;2:241. Epub 2019 Jun 26.

GSK Vaccines Srl, 53100 Siena, Italy.

Monoclonal antibody (mAb) cooperativity is a phenomenon triggered when mAbs couples promote increased bactericidal killing compared to individual partners. Cooperativity has been deeply investigated among mAbs elicited by factor H-binding protein (fHbp), a surface-exposed lipoprotein and one of the key antigens included in both serogroup B meningococcus vaccine Bexsero and Trumenba. Here we report the structural and functional characterization of two cooperative mAbs pairs isolated from Bexsero vaccines. The 3D electron microscopy structures of the human mAb-fHbp-mAb cooperative complexes indicate that the angle formed between the antigen binding fragments (fAbs) assume regular angle and that fHbp is able to bind simultaneously and stably the cooperative mAbs pairs and human factor H (fH) in vitro. These findings shed light on molecular basis of the antibody-based mechanism of protection driven by simultaneous recognition of the different epitopes of the fHbp and underline that cooperativity is crucial in vaccine efficacy.
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http://dx.doi.org/10.1038/s42003-019-0493-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6595007PMC
April 2020

Dual role of the colonization factor CD2831 in Clostridium difficile pathogenesis.

Sci Rep 2019 04 3;9(1):5554. Epub 2019 Apr 3.

Glaxo Smith Kline Vaccines, Via Fiorentina 1, 53100, Siena, Italy.

Clostridium difficile is a Gram-positive, anaerobic bacterium and the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis. C. difficile modulates its transition from a motile to a sessile lifestyle through a mechanism of riboswitches regulated by cyclic diguanosine monophosphate (c-di-GMP). Previously described as a sortase substrate positively regulated by c-di-GMP, CD2831 was predicted to be a collagen-binding protein and thus potentially involved in sessility. By overexpressing CD2831 in C. difficile and heterologously expressing it on the surface of Lactococcus lactis, here we further demonstrated that CD2831 is a collagen-binding protein, able to bind to immobilized collagen types I, III and V as well as native collagen produced by human fibroblasts. We also observed that the overexpression of CD2831 raises the ability to form biofilm on abiotic surface in both C. difficile and L. lactis. Notably, we showed that CD2831 binds to the collagen-like domain of the human complement component C1q, suggesting a role in preventing complement cascade activation via the classical pathway. This functional characterization places CD2831 in the Microbial Surface Components Recognizing Adhesive Matrix Molecule (MSCRAMMs) family, a class of virulence factors with a dual role in adhesion to collagen-rich tissues and in host immune evasion by binding to human complement components.
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http://dx.doi.org/10.1038/s41598-019-42000-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447587PMC
April 2019

Synergistic Protective Activity of Tumor-Specific Epitopes Engineered in Bacterial Outer Membrane Vesicles.

Front Oncol 2017 7;7:253. Epub 2017 Nov 7.

Centre for Integrative Biology (CIBIO), University of Trento, Trento, Italy.

Introduction: Bacterial outer membrane vesicles (OMVs) are naturally produced by all Gram-negative bacteria and, thanks to their plasticity and unique adjuvanticity, are emerging as an attractive vaccine platform. To test the applicability of OMVs in cancer immunotherapy, we decorated them with either one or two protective epitopes present in the B16F10EGFRvIII cell line and tested the protective activity of OMV immunization in C57BL/6 mice challenged with B16F10EGFRvIII.

Materials And Methods: The 14 amino acid B cell epitope of human epidermal growth factor receptor variant III (EGFRvIII) and the mutation-derived CD4+ T cell neo-epitope of gene (B16-M30) were used to decorate OMVs either alone or in combination. C57BL/6 were immunized with the OMVs and then challenged with B16F10EGFRvIII cells. Immunogenicity and protective activity was followed by measuring anti-EGFRvIII antibodies, M30-specific T cells, tumor-infiltrating cell population, and tumor growth.

Results: Immunization with engineered EGFRvIII-OMVs induced a strong inhibition of tumor growth after B16F10EGFRvIII challenge. Furthermore, mice immunized with engineered OMVs carrying both EGFRvIII and M30 epitopes were completely protected from tumor challenge. Immunization was accompanied by induction of high anti-EGFRvIII antibody titers, M30-specific T cells, and infiltration of CD4+ and CD8+ T cells at the tumor site.

Conclusion: OMVs can be decorated with tumor antigens and can elicit antigen-specific, protective antitumor responses in immunocompetent mice. The synergistic protective activity of multiple epitopes simultaneously administered with OMVs makes the OMV platform particularly attractive for cancer immunotherapy.
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http://dx.doi.org/10.3389/fonc.2017.00253DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5681935PMC
November 2017

Auto-Assembling Detoxified Staphylococcus aureus Alpha-Hemolysin Mimicking the Wild-Type Cytolytic Toxin.

Clin Vaccine Immunol 2016 06 6;23(6):442-50. Epub 2016 Jun 6.

GSK Vaccines, Research Center, Siena, Italy

Staphylococcus aureus alpha-hemolysin (Hla) assembles into heptameric pores on the host cell membrane, causing lysis, apoptosis, and junction disruption. Herein, we present the design of a newly engineered S. aureus alpha-toxin, HlaPSGS, which lacks the predicted membrane-spanning stem domain. This protein is able to form heptamers in aqueous solution in the absence of lipophilic substrata, and its structure, obtained by transmission electron microscopy and single-particle reconstruction analysis, resembles the cap of the wild-type cytolytic Hla pore. HlaPSGS was found to be impaired in binding to host cells and to its receptor ADAM10 and to lack hemolytic and cytotoxic activity. Immunological studies using human sera as well as sera from mice convalescent from S. aureus infection suggested that the heptameric conformation of HlaPSGS mimics epitopes exposed by the cytolytic Hla pore during infection. Finally, immunization with this newly engineered Hla generated high protective immunity against staphylococcal infection in mice. Overall, this study provides unprecedented data on the natural immune response against Hla and suggests that the heptameric HlaPSGS is a highly valuable vaccine candidate against S. aureus.
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http://dx.doi.org/10.1128/CVI.00091-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4895005PMC
June 2016

Expression of factor H binding protein in meningococcal strains can vary at least 15-fold and is genetically determined.

Proc Natl Acad Sci U S A 2016 Mar 17;113(10):2714-9. Epub 2016 Feb 17.

GSK Vaccines, 53100 Siena, Italy

Factor H binding protein (fHbp) is a lipoprotein of Neisseria meningitidis important for the survival of the bacterium in human blood and a component of two recently licensed vaccines against serogroup B meningococcus (MenB). Based on 866 different amino acid sequences this protein is divided into three variants or two families. Quantification of the protein is done by immunoassays such as ELISA or FACS that are susceptible to the sequence variation and expression level of the protein. Here, selected reaction monitoring mass spectrometry was used for the absolute quantification of fHbp in a large panel of strains representative of the population diversity of MenB. The analysis revealed that the level of fHbp expression can vary at least 15-fold and that variant 1 strains express significantly more protein than variant 2 or variant 3 strains. The susceptibility to complement-mediated killing correlated with the amount of protein expressed by the different meningococcal strains and this could be predicted from the nucleotide sequence of the promoter region. Finally, the absolute quantification allowed the calculation of the number of fHbp molecules per cell and to propose a mechanistic model of the engagement of C1q, the recognition component of the complement cascade.
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http://dx.doi.org/10.1073/pnas.1521142113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4791009PMC
March 2016

Structural and Computational Biology in the Design of Immunogenic Vaccine Antigens.

J Immunol Res 2015 7;2015:156241. Epub 2015 Oct 7.

Novartis Vaccines & Diagnostics S.r.l. (a GSK Company), Via Fiorentina 1, 53100 Siena, Italy.

Vaccination is historically one of the most important medical interventions for the prevention of infectious disease. Previously, vaccines were typically made of rather crude mixtures of inactivated or attenuated causative agents. However, over the last 10-20 years, several important technological and computational advances have enabled major progress in the discovery and design of potently immunogenic recombinant protein vaccine antigens. Here we discuss three key breakthrough approaches that have potentiated structural and computational vaccine design. Firstly, genomic sciences gave birth to the field of reverse vaccinology, which has enabled the rapid computational identification of potential vaccine antigens. Secondly, major advances in structural biology, experimental epitope mapping, and computational epitope prediction have yielded molecular insights into the immunogenic determinants defining protective antigens, enabling their rational optimization. Thirdly, and most recently, computational approaches have been used to convert this wealth of structural and immunological information into the design of improved vaccine antigens. This review aims to illustrate the growing power of combining sequencing, structural and computational approaches, and we discuss how this may drive the design of novel immunogens suitable for future vaccines urgently needed to increase the global prevention of infectious disease.
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http://dx.doi.org/10.1155/2015/156241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4615220PMC
August 2016

Expression and Characterization of Recombinant, Tetrameric and Enzymatically Active Influenza Neuraminidase for the Setup of an Enzyme-Linked Lectin-Based Assay.

PLoS One 2015 17;10(8):e0135474. Epub 2015 Aug 17.

Research Center, Novartis Vaccines and Diagnostics s.r.l., (a GSK Company), Siena, Italy.

Developing a universal influenza vaccine that induces broad spectrum and longer-term immunity has become an important potentially achievable target in influenza vaccine research and development. Hemagglutinin (HA) and neuraminidase (NA) are the two major influenza virus antigens. Although antibody responses against influenza virus are mainly directed toward HA, NA is reported to be more genetically stable; hence NA-based vaccines have the potential to be effective for longer time periods. NA-specific immunity has been shown to limit the spread of influenza virus, thus reducing disease symptoms and providing cross-protection against heterosubtypic viruses in mouse challenge experiments. The production of large quantities of highly pure and stable NA could be beneficial for the development of new antivirals, subunit-based vaccines, and novel diagnostic tools. In this study, recombinant NA (rNA) was produced in mammalian cells at high levels from both swine A/California/07/2009 (H1N1) and avian A/turkey/Turkey/01/2005 (H5N1) influenza viruses. Biochemical, structural, and immunological characterizations revealed that the soluble rNAs produced are tetrameric, enzymatically active and immunogenic, and finally they represent good alternatives to conventionally used sources of NA in the Enzyme-Linked Lectin Assay (ELLA).
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135474PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4539205PMC
May 2016

An Innovative Pseudotypes-Based Enzyme-Linked Lectin Assay for the Measurement of Functional Anti-Neuraminidase Antibodies.

PLoS One 2015 12;10(8):e0135383. Epub 2015 Aug 12.

GSK, Research Center, Via Fiorentina 1, 53100, Siena, Italy; GSK, Peter Merian Strasse, 4056, Basel, Switzerland.

Antibodies (Ab) to neuraminidase (NA) play a role in limiting influenza infection and might help reduce the disease impact. The most widely used serological assay to measure functional anti-NA immune responses is the Enzyme-Linked Lectin Assay (ELLA) which relies on hemagglutinin (HA) mismatched virus reassortants, or detergent treated viruses as the NA source to overcome interference associated with steric hindrance of anti-HA Ab present in sera. The difficulty in producing and handling these reagents, which are not easily adapted for screening large numbers of samples, limits the routine analysis of functional anti-NA Ab in clinical trials. In this study, we produced influenza lentiviral pseudoparticles (PPs) containing only the NA antigen (NA-PPs) with a simple two-plasmid co-transfection system. NA-PPs were characterized and tested as an innovative source of NA in the NA inhibition (NI) assay. Both swine A/California/07/2009 (H1N1) and avian A/turkey/Turkey/01/2005 (H5N1) N1s within NA-PPs retained their sialidase activity and were specifically inhibited by homologous and N1 subtype-specific, heterologous sheep sera. Moreover, A/California/07/2009 N1-PPs were a better source of NA compared to whole live and detergent treated H1N1 viruses in ELLA, likely due to lack of interference by anti-HA Ab, and absence of possible structural modifications caused by treatment with detergent. This innovative assay is safer and applicable to all NAs. Taken together, these results highlight the potential of NA-PPs-based NI assays to be developed as sensitive, flexible, easy to handle and scalable serological tests for routine NA immune response analysis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135383PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4534301PMC
May 2016

Ultrastructural Visualization of Vaccine Adjuvant Uptake In Vitro and In Vivo.

Microsc Microanal 2015 Aug;21(4):791-5

2Novartis Vaccines and Diagnostics (a GSK company),53100 Siena,Italy.

Adjuvants are substances that enhance adaptive immune responses when formulated in a vaccine. Alum and MF59 are two vaccine adjuvants licensed for human vaccination. Their mode of action has not been completely elucidated. Here we show the first ultrastructural visualization of Alum and MF59 interaction with immune cells in vitro and in vivo. We observed that Alum is engulfed by cells as inclusions of laminae that are detectable within draining lymph nodes. MF59 is instead engulfed by cells in vitro as low-electron-dense lipid-like inclusions that display a vesicle pattern, as confirmed by confocal microscopy using fluorescently labeled MF59. However, lipid-like inclusions with different high- and low-electron-dense content are detected within cells of draining lymph nodes when injecting MF59. As high-electron-dense lipid-like inclusions are also detected upon injection of Alum, our results suggest that the low-electron-dense inclusions are formed by engulfed MF59, whereas the high-electron-dense inclusions are proper lipid inclusions. Thus, we demonstrated that vaccine adjuvants are engulfed as inclusions by lymph node cells and hypothesize that adjuvant treatment may modify lipid metabolism.
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http://dx.doi.org/10.1017/S1431927615013744DOI Listing
August 2015

Streptococcus agalactiae capsule polymer length and attachment is determined by the proteins CpsABCD.

J Biol Chem 2015 Apr 9;290(15):9521-32. Epub 2015 Feb 9.

From Novartis Vaccines and Diagnostics, Research Center, Via Fiorentina 1, 53100 Siena, Italy

The production of capsular polysaccharides (CPS) or secreted exopolysaccharides is ubiquitous in bacteria, and the Wzy pathway constitutes a prototypical mechanism to produce these structures. Despite the differences in polysaccharide composition among species, a group of proteins involved in this pathway is well conserved. Streptococcus agalactiae (group B Streptococcus; GBS) produces a CPS that represents the main virulence factor of the bacterium and is a prime target in current vaccine development. We used this human pathogen to investigate the roles and potential interdependencies of the conserved proteins CpsABCD encoded in the cps operon, by developing knock-out and functional mutant strains. The mutant strains were examined for CPS quantity, size, and attachment to the cell surface as well as CpsD phosphorylation. We observed that CpsB, -C, and -D compose a phosphoregulatory system where the CpsD autokinase phosphorylates its C-terminal tyrosines in a CpsC-dependent manner. These Tyr residues are also the target of the cognate CpsB phosphatase. An interaction between CpsD and CpsC was observed, and the phosphorylation state of CpsD influenced the subsequent action of CpsC. The CpsC extracellular domain appeared necessary for the production of high molecular weight polysaccharides by influencing CpsA-mediated attachment of the CPS to the bacterial cell surface. In conclusion, although having no impact on cps transcription or the synthesis of the basal repeating unit, we suggest that these proteins are fine-tuning the last steps of CPS biosynthesis (i.e. the balance between polymerization and attachment to the cell wall).
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http://dx.doi.org/10.1074/jbc.M114.631499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4392257PMC
April 2015

Structure of the meningococcal vaccine antigen NadA and epitope mapping of a bactericidal antibody.

Proc Natl Acad Sci U S A 2014 Dec 17;111(48):17128-33. Epub 2014 Nov 17.

Novartis Vaccines, 53100 Siena, Italy; and.

Serogroup B Neisseria meningitidis (MenB) is a major cause of severe sepsis and invasive meningococcal disease, which is associated with 5-15% mortality and devastating long-term sequelae. Neisserial adhesin A (NadA), a trimeric autotransporter adhesin (TAA) that acts in adhesion to and invasion of host epithelial cells, is one of the three antigens discovered by genome mining that are part of the MenB vaccine that recently was approved by the European Medicines Agency. Here we present the crystal structure of NadA variant 5 at 2 Å resolution and transmission electron microscopy data for NadA variant 3 that is present in the vaccine. The two variants show similar overall topology with a novel TAA fold predominantly composed of trimeric coiled-coils with three protruding wing-like structures that create an unusual N-terminal head domain. Detailed mapping of the binding site of a bactericidal antibody by hydrogen/deuterium exchange MS shows that a protective conformational epitope is located in the head of NadA. These results provide information that is important for elucidating the biological function and vaccine efficacy of NadA.
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http://dx.doi.org/10.1073/pnas.1419686111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4260552PMC
December 2014

Modulation of endotoxicity of Shigella generalized modules for membrane antigens (GMMA) by genetic lipid A modifications: relative activation of TLR4 and TLR2 pathways in different mutants.

J Biol Chem 2014 Sep 14;289(36):24922-35. Epub 2014 Jul 14.

From the Novartis Vaccines Institute for Global Health and

Outer membrane particles from Gram-negative bacteria are attractive vaccine candidates as they present surface antigens in their natural context. We previously developed a high yield production process for genetically derived particles, called generalized modules for membrane antigens (GMMA), from Shigella. As GMMA are derived from the outer membrane, they contain immunostimulatory components, especially lipopolysaccharide (LPS). We examined ways of reducing their reactogenicity by modifying lipid A, the endotoxic part of LPS, through deletion of late acyltransferase genes, msbB or htrB, in GMMA-producing Shigella sonnei and Shigella flexneri strains. GMMA with resulting penta-acylated lipid A from the msbB mutants showed a 600-fold reduced ability, and GMMA from the S. sonnei ΔhtrB mutant showed a 60,000-fold reduced ability compared with GMMA with wild-type lipid A to stimulate human Toll-like receptor 4 (TLR4) in a reporter cell line. In human peripheral blood mononuclear cells, GMMA with penta-acylated lipid A showed a marked reduction in induction of inflammatory cytokines (S. sonnei ΔhtrB, 800-fold; ΔmsbB mutants, 300-fold). We found that the residual activity of these GMMA is largely due to non-lipid A-related TLR2 activation. In contrast, in the S. flexneri ΔhtrB mutant, a compensatory lipid A palmitoleoylation resulted in GMMA with hexa-acylated lipid A with ∼10-fold higher activity to stimulate peripheral blood mononuclear cells than GMMA with penta-acylated lipid A, mostly due to retained TLR4 activity. Thus, for use as vaccines, GMMA will likely require lipid A penta-acylation. The results identify the relative contributions of TLR4 and TLR2 activation by GMMA, which need to be taken into consideration for GMMA vaccine development.
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http://dx.doi.org/10.1074/jbc.M114.566570DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4155660PMC
September 2014

Structural vaccinology: a three-dimensional view for vaccine development.

Curr Top Med Chem 2013 ;13(20):2629-37

Novartis Vaccines and Diagnostics, Siena, Italy.

The Structural Vaccinology (SV) approach is the logical evolution of Reverse Vaccinology: a genome-based approach combined with structural biology, with the idea that protective determinants can be used to selectively engineer the antigens that can be re-designed and simplified for inclusion in vaccine combinations. The final objectives of the rational structure-based antigen optimization are the facilitation of industrial-scale production of the antigens combination, obtain a greater immunogenicity and a greater safety profile and finally expand the breadth of protection. Structural Vaccinology is particularly powerful in case of antigenic variation between closely related strains and species. Several examples are available in literature of how SV has already been applied successfully to several bacterial and viral projects. The examples of structure-based antigens optimization reviewed here describe different template procedures that can be followed to develop improved vaccines against other pathogens and potentially help resolve challenges in manufacturing or efficacy.
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http://dx.doi.org/10.2174/15680266113136660187DOI Listing
June 2014

High yield production process for Shigella outer membrane particles.

PLoS One 2012 6;7(6):e35616. Epub 2012 Jun 6.

Novartis Vaccines Institute for Global Health, Siena, Italy.

Gram-negative bacteria naturally shed particles that consist of outer membrane lipids, outer membrane proteins, and soluble periplasmic components. These particles have been proposed for use as vaccines but the yield has been problematic. We developed a high yielding production process of genetically derived outer membrane particles from the human pathogen Shigella sonnei. Yields of approximately 100 milligrams of membrane-associated proteins per liter of fermentation were obtained from cultures of S. sonnei ΔtolR ΔgalU at optical densities of 30-45 in a 5 L fermenter. Proteomic analysis of the purified particles showed the preparation to primarily contain predicted outer membrane and periplasmic proteins. These were highly immunogenic in mice. The production of these outer membrane particles from high density cultivation of bacteria supports the feasibility of scaling up this approach as an affordable manufacturing process. Furthermore, we demonstrate the feasibility of using this process with other genetic manipulations e.g. abolition of O antigen synthesis and modification of the lipopolysaccharide structure in order to modify the immunogenicity or reactogenicity of the particles. This work provides the basis for a large scale manufacturing process of Generalized Modules of Membrane Antigens (GMMA) for production of vaccines from gram-negative bacteria.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0035616PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3368891PMC
November 2012

FdeC, a novel broadly conserved Escherichia coli adhesin eliciting protection against urinary tract infections.

mBio 2012 10;3(2). Epub 2012 Apr 10.

Novartis Vaccines and Diagnostics Srl, Siena, Italy.

Unlabelled: The increasing antibiotic resistance of pathogenic Escherichia coli species and the absence of a pan-protective vaccine pose major health concerns. We recently identified, by subtractive reverse vaccinology, nine Escherichia coli antigens that protect mice from sepsis. In this study, we characterized one of them, ECOK1_0290, named FdeC (factor adherence E. coli) for its ability to mediate E. coli adhesion to mammalian cells and extracellular matrix. This adhesive propensity was consistent with the X-ray structure of one of the FdeC domains that shows a striking structural homology to Yersinia pseudotuberculosis invasin and enteropathogenic E. coli intimin. Confocal imaging analysis revealed that expression of FdeC on the bacterial surface is triggered by interaction of E. coli with host cells. This phenotype was also observed in bladder tissue sections derived from mice infected with an extraintestinal strain. Indeed, we observed that FdeC contributes to colonization of the bladder and kidney, with the wild-type strain outcompeting the fdeC mutant in cochallenge experiments. Finally, intranasal mucosal immunization with recombinant FdeC significantly reduced kidney colonization in mice challenged transurethrally with uropathogenic E. coli, supporting a role for FdeC in urinary tract infections.

Importance: Pathogenic Escherichia coli strains are involved in a diverse spectrum of diseases, including intestinal and extraintestinal infections (urinary tract infections and sepsis). The absence of a broadly protective vaccine against all these E. coli strains is a major problem for modern society due to high costs to health care systems. Here, we describe the structural and functional properties of a recently reported protective antigen, named FdeC, and elucidated its putative role during extraintestinal pathogenic E. coli infection by using both in vitro and in vivo infection models. The conservation of FdeC among strains of different E. coli pathotypes highlights its potential as a component of a broadly protective vaccine against extraintestinal and intestinal E. coli infections.
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http://dx.doi.org/10.1128/mBio.00010-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3324786PMC
June 2012

Characterization of human endogenous retroviral elements in the blood of HIV-1-infected individuals.

J Virol 2012 Jan 26;86(1):262-76. Epub 2011 Oct 26.

Department of Internal Medicine, and Programs in Cancer Biology, Immunology, and Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA.

We previously reported finding the RNA of a type K human endogenous retrovirus, HERV-K (HML-2), at high titers in the plasma of HIV-1-infected and cancer patients (R. Contreras-Galindo et al., J. Virol. 82:9329-9236, 2008.). The extent to which the HERV-K (HML-2) proviruses become activated and the nature of their activated viral RNAs remain important questions. Therefore, we amplified and sequenced the full-length RNA of the env gene of the type 1 and 2 HERV-K (HML-2) viruses collected from the plasma of seven HIV-1-infected patients over a period of 1 to 3 years and from five breast cancer patients in order to reconstruct the genetic evolution of these viruses. HERV-K (HML-2) RNA was found in plasma fractions of HIV-1 patients at a density of ∼1.16 g/ml that contained both immature and correctly processed HERV-K (HML-2) proteins and virus-like particles that were recognized by anti-HERV-K (HML-2) antibodies. RNA sequences from novel HERV-K (HML-2) proviruses were discovered, including K111, which is specifically active during HIV-1 infection. Viral RNA arose from complete proviruses and proviruses devoid of a 5' long terminal repeat, suggesting that the expression of HERV-K (HML-2) RNA in these patients may involve sense and antisense transcription. In HIV-1-infected individuals, the HERV-K (HML-2) viral RNA showed evidence of frequent recombination, accumulation of synonymous rather than nonsynonymous mutations, and conserved N-glycosylation sites, suggesting that some of the HERV-K (HML-2) viral RNAs have undergone reverse transcription and are under purifying selection. In contrast, HERV-K (HML-2) RNA sequences found in the blood of breast cancer patients showed no evidence of recombination and exhibited only sporadic viral mutations. This study suggests that HERV-K (HML-2) is active in HIV-1-infected patients, and the resulting RNA message reveals previously undiscovered HERV-K (HML-2) genomic sequences.
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http://dx.doi.org/10.1128/JVI.00602-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3255917PMC
January 2012

The full-length Streptococcus pneumoniae major pilin RrgB crystallizes in a fibre-like structure, which presents the D1 isopeptide bond and provides details on the mechanism of pilus polymerization.

Biochem J 2012 Feb;441(3):833-41

CEA, Institut de Biologie Structurale Jean-Pierre Ebel, F-38027 Grenoble, France.

RrgB is the major pilin which forms the pneumococcal pilus backbone. We report the high-resolution crystal structure of the full-length form of RrgB containing the IPQTG sorting motif. The RrgB fold is organized into four distinct domains, D1-D4, each of which is stabilized by an isopeptide bond. Crystal packing revealed a head-to-tail organization involving the interaction of the IPQTG motif into the D1 domain of two successive RrgB monomers. This fibrillar assembly, which fits into the electron microscopy density map of the native pilus, probably induces the formation of the D1 isopeptide bond as observed for the first time in the present study, since neither in published structures nor in soluble RrgB produced in Escherichia coli or in Streptococcus pneumoniae is the D1 bond present. Experiments performed in live bacteria confirmed that the intermolecular bond linking the RrgB subunits takes place between the IPQTG motif of one RrgB subunit and the Lys183 pilin motif residue of an adjacent RrgB subunit. In addition, we present data indicating that the D1 isopeptide bond is involved in RrgB stabilization. In conclusion, the crystal RrgB fibre is a compelling model for deciphering the molecular details required to generate the pneumococcal pilus.
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http://dx.doi.org/10.1042/BJ20111397DOI Listing
February 2012

EM reconstruction of adhesins: future prospects.

Adv Exp Med Biol 2011 ;715:271-84

Novartis Vaccines and Diagnostics srl, 53100, Siena, Italy.

Both Gram-negative and Gram-positive pathogenic bacteria present a remarkable number of surface-exposed organelles and secreted toxins that allow them to control the primary stages of infection, bacterial attachment to host cell receptors and colonization. The mediators of these processes, called adhesins, form a heterogeneous group that varies in architecture, domain content and mechanism of binding. A full understanding of how adhesins mediate cellular adhesion and colonization requires quantitative functional assays to evaluate the strength of the binding interactions, as well as determination of the high-resolution three-dimensional structures of the molecules to provide the atomic details of the interactions. The combination of classical imaging techniques like X-ray crystallography and Nuclear Magnetic Resonance (NMR) with the emerging technique of single-particle electron cryomicroscopy has become a tremendously helpful tool to understand the three-dimensional structure at near atomic-level resolution of newly discovered adhesins and their complexes. A detailed study of the structure of these molecules, both isolated and expressed on bacterial surface is a fundamental requirement for understanding the adhesion mechanism to host cells. This chapter will focus on the structure determination of such surface-exposed protein structures in both Gram-negative and Gram-positive bacterial adhesins.
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http://dx.doi.org/10.1007/978-94-007-0940-9_17DOI Listing
July 2011

Structural and functional characterization of the Streptococcus pneumoniae RrgB pilus backbone D1 domain.

J Biol Chem 2011 Apr 2;286(16):14588-97. Epub 2011 Mar 2.

Novartis Vaccines and Diagnostics Research Center, Via Fiorentina 1, Siena 53100, Italy.

Streptococcus pneumoniae expresses on its surface adhesive pili, involved in bacterial attachment to epithelial cells and virulence. The pneumococcal pilus is composed of three proteins, RrgA, RrgB, and RrgC, each stabilized by intramolecular isopeptide bonds and covalently polymerized by means of intermolecular isopeptide bonds to form an extended fiber. RrgB is the pilus scaffold subunit and is protective in vivo in mouse models of sepsis and pneumonia, thus representing a potential vaccine candidate. The crystal structure of a major RrgB C-terminal portion featured an organization into three independently folded protein domains (D2-D4), whereas the N-terminal D1 domain (D1) remained unsolved. We have tested the four single recombinant RrgB domains in active and passive immunization studies and show that D1 is the most effective, providing a level of protection comparable with that of the full-length protein. To elucidate the structural features of D1, we solved the solution structure of the recombinant domain by NMR spectroscopy. The spectra analysis revealed that D1 has many flexible regions, does not contain any intramolecular isopeptide bond, and shares with the other domains an Ig-like fold. In addition, we demonstrated, by site-directed mutagenesis and complementation in S. pneumoniae, that the D1 domain contains the Lys residue (Lys-183) involved in the formation of the intermolecular isopeptide bonds and pilus polymerization. Finally, we present a model of the RrgB protein architecture along with the mapping of two surface-exposed linear epitopes recognized by protective antisera.
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http://dx.doi.org/10.1074/jbc.M110.202739DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3077656PMC
April 2011

Structure analysis and site-directed mutagenesis of defined key residues and motives for pilus-related sortase C1 in group B Streptococcus.

FASEB J 2011 Jun 25;25(6):1874-86. Epub 2011 Feb 25.

Novartis Vaccines and Diagnostics, Via Fiorentina 1, 53100 Siena, Italy.

In group B Streptococcus (GBS), 3 structurally distinct types of pili have been discovered as potential virulence factors and vaccine candidates. The pilus-forming proteins are assembled into high-molecular-weight polymers via a transpeptidation mechanism mediated by specific class C sortases. Using a multidisciplinary approach including bioinformatics, structural and biochemical studies, and in vivo mutagenesis, we performed a broad characterization of GBS sortase C1 of pilus island 2a. The high-resolution X-ray structure of the enzyme revealed that the active site, into the β-barrel core of the enzyme, is made of the catalytic triad His157-Cys219-Arg228 and covered by a loop, known as the "lid." We show that the catalytic triad and the predicted N- and C-terminal transmembrane regions are required for the enzyme activity. Interestingly, by in vivo complementation mutagenesis studies, we found that the deletion of the entire lid loop or mutations in specific lid key residues had no effect on catalytic activity of the enzyme. In addition, kinetic characterizations of recombinant enzymes indicate that the lid mutants can still recognize and cleave the substrate-mimicking peptide at least as well as the wild-type protein.
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http://dx.doi.org/10.1096/fj.10-174797DOI Listing
June 2011

The two variants of the Streptococcus pneumoniae pilus 1 RrgA adhesin retain the same function and elicit cross-protection in vivo.

Infect Immun 2010 Dec 7;78(12):5033-42. Epub 2010 Sep 7.

Novartis Vaccines and Diagnostics, Via Fiorentina, Siena 53100, Italy.

Thirty percent of Streptococcus pneumoniae isolates contain pilus islet 1, coding for a pilus composed of the backbone subunit RrgB and two ancillary proteins, RrgA and RrgC. RrgA is the major determinant of in vitro adhesion associated with pilus 1, is protective in vivo in mouse models, and exists in two variants (clades I and II). Mapping of the sequence variability onto the RrgA structure predicted from X-ray data showed that the diversity was restricted to the "head" of the protein, which contains the putative binding domains, whereas the elongated "stalk" was mostly conserved. To investigate whether this variability could influence the adhesive capacity of RrgA and to map the regions important for binding, two full-length protein variants and three recombinant RrgA portions were tested for adhesion to lung epithelial cells and to purified extracellular matrix (ECM) components. The two RrgA variants displayed similar binding abilities, whereas none of the recombinant fragments adhered at levels comparable to those of the full-length protein, suggesting that proper folding and structural arrangement are crucial to retain protein functionality. Furthermore, the two RrgA variants were shown to be cross-reactive in vitro and cross-protective in vivo in a murine model of passive immunization. Taken together, these data indicate that the region implicated in adhesion and the functional epitopes responsible for the protective ability of RrgA may be conserved and that the considerable level of variation found within the "head" domain of RrgA may have been generated by immunologic pressure without impairing the functional integrity of the pilus.
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http://dx.doi.org/10.1128/IAI.00601-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2981310PMC
December 2010

Supramolecular organization of the repetitive backbone unit of the Streptococcus pneumoniae pilus.

PLoS One 2010 Jun 15;5(6):e10919. Epub 2010 Jun 15.

Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America.

Streptococcus pneumoniae, like many other Gram-positive bacteria, assembles long filamentous pili on their surface through which they adhere to host cells. Pneumococcal pili are formed by a backbone, consisting of the repetition of the major component RrgB, and two accessory proteins (RrgA and RrgC). Here we reconstruct by transmission electron microscopy and single particle image reconstruction method the three dimensional arrangement of two neighbouring RrgB molecules, which represent the minimal repetitive structural domain of the native pilus. The crystal structure of the D2-D4 domains of RrgB was solved at 1.6 A resolution. Rigid-body fitting of the X-ray coordinates into the electron density map enabled us to define the arrangement of the backbone subunits into the S. pneumoniae native pilus. The quantitative fitting provide evidence that the pneumococcal pilus consists uniquely of RrgB monomers assembled in a head-to-tail organization. The presence of short intra-subunit linker regions connecting neighbouring domains provides the molecular basis for the intrinsic pilus flexibility.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0010919PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2886109PMC
June 2010

Molecular architecture of Streptococcus pneumoniae TIGR4 pili.

EMBO J 2009 Dec;28(24):3921-30

Research Center, Novartis Vaccines and Diagnostics s.r.l., Siena, Italy.

Although the pili of Gram-positive bacteria are putative virulence factors, little is known about their structure. Here we describe the molecular architecture of pilus-1 of Streptococcus pneumoniae, which is a major cause of morbidity and mortality worldwide. One major (RrgB) and two minor components (RrgA and RrgC) assemble into the pilus. Results from TEM and scanning transmission EM show that the native pili are approximately 6 nm wide, flexible filaments that can be over 1 microm long. They are formed by a single string of RrgB monomers and have a polarity defined by nose-like protrusions. These protrusions correlate to the shape of monomeric RrgB-His, which like RrgA-His and RrgC-His has an elongated, multi-domain structure. RrgA and RrgC are only present at the opposite ends of the pilus shaft, compatible with their putative roles as adhesin and anchor to the cell wall surface, respectively. Our structural analyses provide the first direct experimental evidence that the native S. pneumoniae pilus shaft is composed exclusively of covalently linked monomeric RrgB subunits oriented head-to-tail.
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http://dx.doi.org/10.1038/emboj.2009.360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2797065PMC
December 2009

CT043, a protective antigen that induces a CD4+ Th1 response during Chlamydia trachomatis infection in mice and humans.

Infect Immun 2009 Sep 13;77(9):4168-76. Epub 2009 Jul 13.

Novartis Vaccines and Diagnostics, 53100 Siena, Italy.

Despite several decades of intensive studies, no vaccines against Chlamydia trachomatis, an intracellular pathogen causing serious ocular and urogenital diseases, are available yet. Infection-induced immunity in both animal models and humans strongly supports the notion that for a vaccine to be effective a strong CD4(+) Th1 immune response should be induced. In the course of our vaccine screening program based on the selection of chlamydial proteins eliciting cell-mediated immunity, we have found that CT043, a protein annotated as hypothetical, induces CD4(+) Th1 cells both in chlamydia-infected mice and in human patients with diagnosed C. trachomatis genital infection. DNA priming/protein boost immunization with CT043 results in a 2.6-log inclusion-forming unit reduction in the murine lung infection model. Sequence analysis of CT043 from C. trachomatis human isolates belonging to the most representative genital serovars revealed a high degree of conservation, suggesting that this antigen could provide cross-serotype protection. Therefore, CT043 is a promising vaccine candidate against C. trachomatis infection.
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http://dx.doi.org/10.1128/IAI.00344-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738022PMC
September 2009