1
|
Aistleitner K, Heinz C, Hörmann A, Heinz E, Montanaro J, Schulz F, Maier E, Pichler P, Benz R, Horn M. Identification and characterization of a novel porin family highlights a major difference in the outer membrane of chlamydial symbionts and pathogens. PLoS One 2013; 8:e55010. [PMID: 23383036 PMCID: PMC3561449 DOI: 10.1371/journal.pone.0055010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 12/18/2012] [Indexed: 11/24/2022] Open
Abstract
The Chlamydiae constitute an evolutionary well separated group of intracellular bacteria comprising important pathogens of humans as well as symbionts of protozoa. The amoeba symbiont Protochlamydia amoebophila lacks a homologue of the most abundant outer membrane protein of the Chlamydiaceae, the major outer membrane protein MOMP, highlighting a major difference between environmental chlamydiae and their pathogenic counterparts. We recently identified a novel family of putative porins encoded in the genome of P. amoebophila by in silico analysis. Two of these Protochlamydiaouter membrane proteins, PomS (pc1489) and PomT (pc1077), are highly abundant in outer membrane preparations of this organism. Here we show that all four members of this putative porin family are toxic when expressed in the heterologous host Escherichia coli. Immunofluorescence analysis using antibodies against heterologously expressed PomT and PomS purified directly from elementary bodies, respectively, demonstrated the location of both proteins in the outer membrane of P. amoebophila. The location of the most abundant protein PomS was further confirmed by immuno-transmission electron microscopy. We could show that pomS is transcribed, and the corresponding protein is present in the outer membrane throughout the complete developmental cycle, suggesting an essential role for P. amoebophila. Lipid bilayer measurements demonstrated that PomS functions as a porin with anion-selectivity and a pore size similar to the Chlamydiaceae MOMP. Taken together, our results suggest that PomS, possibly in concert with PomT and other members of this porin family, is the functional equivalent of MOMP in P. amoebophila. This work contributes to our understanding of the adaptations of symbiotic and pathogenic chlamydiae to their different eukaryotic hosts.
Collapse
Affiliation(s)
- Karin Aistleitner
- Department of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Christian Heinz
- Department of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Alexandra Hörmann
- Department of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Eva Heinz
- Department of Microbial Ecology, University of Vienna, Vienna, Austria
| | | | - Frederik Schulz
- Department of Microbial Ecology, University of Vienna, Vienna, Austria
| | - Elke Maier
- Rudolf-Virchow-Center, Deutsche Forschungsgemeinschaft - Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Peter Pichler
- Christian Doppler Laboratory for Mass Spectrometry, Vienna, Austria
| | - Roland Benz
- Rudolf-Virchow-Center, Deutsche Forschungsgemeinschaft - Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
- School of Engineering and Science, Jacobs University Bremen, Bremen, Germany
| | - Matthias Horn
- Department of Microbial Ecology, University of Vienna, Vienna, Austria
- * E-mail:
| |
Collapse
|
2
|
Ling Y, Li S, Yang J, Yuan J, He C. Co-administration of the polysaccharide of Lycium barbarum with DNA vaccine of Chlamydophila abortus augments protection. Immunol Invest 2010; 40:1-13. [PMID: 20942772 DOI: 10.3109/08820139.2010.504803] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lycium barbarum polysaccharides (LBP) can stimulate moderate immune responses therefore could potentially be used as a substitute for oil adjuvants in veterinary vaccines. In the present study, it was shown that the isolated active component of LBP3a, combined with a DNA vaccine encoding the major outer membrane protein (MOMP) of Chlamydophila abortus, induced protection in mice against challenge. Sixty BALB/c mice were randomly assigned to 5 groups. Sub-fractions of polysaccharide LBP3a, at 12.5, 25 and 50 mg/kg concentrations, respectively, were mixed with a pCI-neo::MOMP (pMOMP) vaccine. Mice administrated with pCI-neo + LBP3a were served as a control. All mice were inoculated at day 0, 14, and 28, and challenged on day 44. The effects of LBp3a on serum antibody levels, in vitro lymphocyte proliferation, the activity of interleaukin-2 (IL-2), interferon-γ (IFN-γ), tumor necrosis factor α(TNF-α)and chlamydia clearance were determined. A combination of DNA vaccine and LBP3a induced significantly higher antibody levels in mice, higher T cell proliferation and higher levels of IFN-γ and IL-2. Mice immunized with DNA and LBP3a also showed significantly higher levels of chlamydia clearance in mice spleens and a greater Th1 immune response. The immunoenhancement induced by 25 mg/kg LBP3a is more effective than that induced by a 12.5 and 50 mg/kg. This implies that LBP3a at 25 mg/kg has a high potential to be used as an effective adjuvant with a DNA vaccine against swine Chlamydophila abortus.
Collapse
Affiliation(s)
- Yong Ling
- Key Lab of Zoonosis of Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Haidian District, Beijing 100193, China
| | | | | | | | | |
Collapse
|
3
|
Schulte A, Ruamchan S, Khunkaewla P, Suginta W. The outer membrane protein VhOmp of Vibrio harveyi: pore-forming properties in black lipid membranes. J Membr Biol 2009; 230:101-11. [PMID: 19672645 DOI: 10.1007/s00232-009-9194-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2009] [Accepted: 07/28/2009] [Indexed: 11/27/2022]
Abstract
Vibrio harveyi is known to cause fatal vibriosis in marine animals. Here, an outer membrane protein from V. harveyi, namely, VhOmp, was isolated and functionally characterized in terms of pore-forming contact with artificial lipid membranes. The native VhOmp exists as a trimer of a molecular weight similar to that of the porin OmpF from Escherichia coli. Reconstitution of VhOmp into black lipid membranes demonstrated its ability to form ion channels. The average pore conductance of VhOmp was revealed to be about 0.9 and 2 nS in 0.2 and 1 M KCl, respectively. Within transmembrane potentials of +/-100 mV, VhOmp pores behaved as ohmic conduits, and their conductance scaled linearly with voltage. Nonlinear plots of the pore conductance versus symmetrical salt concentrations at either side of the protein-incorporating membrane suggested the influence of interior channel functionalities on the passage of charged species. In the presence of Omp-specific polyclonal antibodies, the pore-forming property of VhOmp was modulated so that the usual step-like current increments were replaced by random transitory current fluctuations. VhOmp exhibited a strong biological activity by causing hemolysis of human red blood cells, indicating that VhOmp may act as a crucial determinant during bacterial infection to animal host cells.
Collapse
Affiliation(s)
- Albert Schulte
- Biochemistry-Electrochemistry Research Unit, School of Chemistry and Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | | | | | | |
Collapse
|
4
|
Savijoki K, Alvesalo J, Vuorela P, Leinonen M, Kalkkinen N. Proteomic analysis ofChlamydia pneumoniae-infected HL cells reveals extensive degradation of cytoskeletal proteins. ACTA ACUST UNITED AC 2008; 54:375-84. [DOI: 10.1111/j.1574-695x.2008.00488.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
5
|
Juul N, Timmerman E, Gevaert K, Christiansen G, Birkelund S. Proteolytic cleavage of the Chlamydia pneumoniae major outer membrane protein in the absence of Pmp10. Proteomics 2008; 7:4477-87. [PMID: 18022938 DOI: 10.1002/pmic.200700447] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The genome of the obligate intracellular bacteria Chlamydia pneumoniae contains 21 genes encoding polymorphic membrane proteins (Pmp). While no function has yet been attributed to the Pmps, they may be involved in an antigenic variation of the Chlamydia surface. It has previously been demonstrated that Pmp10 is differentially expressed in the C. pneumoniae CWL029 isolate. To evaluate whether the absence of Pmp10 in the outer membrane causes further changes to the C. pneumoniae protein profile, we subcloned the CWL029 isolate and selected a clone with minimal Pmp10 expression. Subsequently, we compared the proteome of the CWL029 isolate with the proteome of the subcloned strain and identified a specific cleavage of the C-terminal part of the major outer membrane protein (MOMP), which occurred only in the absence of Pmp10. In contrast, when Pmp10 was expressed we predominantly observed full-length MOMP. No other proteins appeared to be regulated according to the presence or absence of Pmp10. These results suggest a close association between MOMP and Pmp10, where Pmp10 may protect the C-terminal part of MOMP from proteolytic cleavage.
Collapse
Affiliation(s)
- Nicolai Juul
- Institute of Medical Microbiology and Immunology, University of Aarhus, Aarhus C, Denmark
| | | | | | | | | |
Collapse
|
6
|
Igietseme J, Eko F, He Q, Bandea C, Lubitz W, Garcia-Sastre A, Black C. Delivery of Chlamydia vaccines. Expert Opin Drug Deliv 2005; 2:549-62. [PMID: 16296774 DOI: 10.1517/17425247.2.3.549] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The plethora of ocular, genital and respiratory diseases of Chlamydia, including nongonococcal urethritis, cervicitis pelvic inflammatory disease, ectopic pregnancy, tubal factor infertility, conjunctivitis, blinding trachoma and interstitial pneumonia, and chronic diseases that may include atherosclerosis, multiple sclerosis, adult onset asthma and Alzheimer's disease, still pose a considerable public health challenge to many nations. Although antibiotics are effective against Chlamydia when effectively diagnosed, asymptomatic infections are rampart, making clinical presentation of complications often the first evidence of an infection. Consequently, the current medical opinion is that an effective prophylactic vaccine would constitute the best approach to protect the human population from the most severe consequences of these infections. Clinical and experimental studies have demonstration that Chlamydia immunity in animals and humans is mediated by T cells and a complementary antibody response, and the completion of the genome sequencing of several isolates of Chlamydia is broadening our knowledge of the immunogenic antigens with potential vaccine value. Thus, major advances have been made in defining the essential elements of a potentially effective subunit vaccine design and parameters for evaluation. However, the challenge to develop effective delivery systems and human compatible adjuvants that would boost the immune response to achieve long-lasting protective immunity remains an elusive objective in chlamydial vaccine research. In response to evolving molecular and cellular technologies and novel vaccinology approaches, considerable progress is being made in the construction of novel delivery systems, such as DNA and plasmid expression systems, viral vectors, living and nonliving bacterial delivery systems, the use of chemical adjuvants, lipoprotein constructs and the codelivery of vaccines and specific immuno-modulatory biological agonists targeting receptors for chemokines, Toll-like receptors, and costimulatory molecules. The application of these novel delivery strategies to Chlamydia vaccine design could culminate in timely achievement of an efficacious vaccine.
Collapse
Affiliation(s)
- Joseph Igietseme
- National Center for Infectious Disease/CDC, Atlanta, GA 30333, USA.
| | | | | | | | | | | | | |
Collapse
|
7
|
Findlay HE, McClafferty H, Ashley RH. Surface expression, single-channel analysis and membrane topology of recombinant Chlamydia trachomatis Major Outer Membrane Protein. BMC Microbiol 2005; 5:5. [PMID: 15673471 PMCID: PMC549562 DOI: 10.1186/1471-2180-5-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Accepted: 01/26/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Chlamydial bacteria are obligate intracellular pathogens containing a cysteine-rich porin (Major Outer Membrane Protein, MOMP) with important structural and, in many species, immunity-related roles. MOMP forms extensive disulphide bonds with other chlamydial proteins, and is difficult to purify. Leaderless, recombinant MOMPs expressed in E. coli have yet to be refolded from inclusion bodies, and although leadered MOMP can be expressed in E. coli cells, it often misfolds and aggregates. We aimed to improve the surface expression of correctly folded MOMP to investigate the membrane topology of the protein, and provide a system to display native and modified MOMP epitopes. RESULTS C. trachomatis MOMP was expressed on the surface of E. coli cells (including "porin knockout" cells) after optimizing leader sequence, temperature and medium composition, and the protein was functionally reconstituted at the single-channel level to confirm it was folded correctly. Recombinant MOMP formed oligomers even in the absence of its 9 cysteine residues, and the unmodified protein also formed inter- and intra-subunit disulphide bonds. Its topology was modeled as a (16-stranded) beta-barrel, and specific structural predictions were tested by removing each of the four putative surface-exposed loops corresponding to highly immunogenic variable sequence (VS) domains, and one or two of the putative transmembrane strands. The deletion of predicted external loops did not prevent folding and incorporation of MOMP into the E. coli outer membrane, in contrast to the removal of predicted transmembrane strands. CONCLUSIONS C. trachomatis MOMP was functionally expressed on the surface of E. coli cells under newly optimized conditions. Tests of its predicted membrane topology were consistent with beta-barrel oligomers in which major immunogenic regions are displayed on surface-exposed loops. Functional surface expression, coupled with improved understanding of MOMP's topology, could provide modified antigens for immunological studies and vaccination, including live subunit vaccines, and might be useful to co-express MOMP with other chlamydial membrane proteins.
Collapse
Affiliation(s)
- Heather E Findlay
- Division of Biomedical Sciences, University of Edinburgh Medical School, George Square, Edinburgh EH8 9XD, UK
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Heather McClafferty
- Division of Biomedical Sciences, University of Edinburgh Medical School, George Square, Edinburgh EH8 9XD, UK
| | - Richard H Ashley
- Division of Biomedical Sciences, University of Edinburgh Medical School, George Square, Edinburgh EH8 9XD, UK
| |
Collapse
|
8
|
Abstract
Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions.
Collapse
Affiliation(s)
- Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA.
| |
Collapse
|
9
|
Hoelzle LE, Hoelzle K, Wittenbrink MM. Expression of the Major Outer Membrane Protein (MOMP) of Chlamydophila abortus, Chlamydophila pecorum, and Chlamydia suis in Escherichia coli using an Arabinose-inducible Plasmid Vector. ACTA ACUST UNITED AC 2003; 50:383-9. [PMID: 14633208 DOI: 10.1046/j.1439-0450.2003.00685.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ompA genes encoding the 40 kDa major outer membrane protein (MOMP) of Chlamydophila (Ch.) abortus, Ch. pecorum, and Chlamydia (C.) suis were cloned into the arabinose-inducible plasmid vector pBADMycHis, and recombinant MOMPs (rMOMP) from the three chlamydial species were expressed at high levels in Escherichia (E.) coli. The proteins lacking the 22 aa N-terminal signal peptide were expressed as insoluble cytoplasmic inclusion bodies which were readily purified using immobilized metal-affinity chromatography. The rMOMPs including the N-terminal signal peptide were expressed and translocated as a surface-exposed immunoaccessible protein into the outer membrane of E. coli. Transformants expressing this full-length rMOMP were significantly reduced in viability. Purified native elementary bodies (EB) and rMOMPs of the three chlamydial species purified from the E. coli cytoplasm were used for immunization of rabbits. The resulting sera were analysed for their ability to recognize homologous and heterologous rMOMP and native EB. When testing rMOMP antisera against rMOMP and EB antigens, marked cross-reactivities were detected between the three species. Using EB antisera and rMOMPs as antigens, a significant species-specific reactivity was measured.
Collapse
Affiliation(s)
- L E Hoelzle
- Institute of Veterinary Bacteriology, University of Zurich, Winterthurerstrasse 270, CH-8057 Zurich, Switzerland.
| | | | | |
Collapse
|
10
|
Klein M, Kötz A, Bernardo K, Krönke M. Detection of Chlamydia pneumoniae-specific antibodies binding to the VD2 and VD3 regions of the major outer membrane protein. J Clin Microbiol 2003; 41:1957-62. [PMID: 12734234 PMCID: PMC154690 DOI: 10.1128/jcm.41.5.1957-1962.2003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although Chlamydia pneumoniae is an important human pathogen, the antigens eliciting a specific humoral immune response remain elusive. We scrutinized several recombinant chlamydial surface proteins for species-specific recognition by a panel of human sera previously tested for the presence of anti-C. pneumoniae and anti-C. trachomatis antibodies by microimmunofluorescence and enzyme-linked immunosorbent assay. The 15-kDa cysteine-rich protein (CrpA), porin-b (PorB), 9-kDa outer membrane protein (OMP3), 60-kDa outer membrane protein (OMP2), and four fragments of the major outer membrane protein (MOMP) representing each variable domain (VD) were overexpressed in Escherichia coli, affinity purified, and employed for Western blot analysis. None of the sera tested contained antibodies recognizing PorB and OMP3 of C. pneumoniae. Sera from C. pneumoniae-immune patients cross-reacted with OMP2 of C. trachomatis, and sera from C. trachomatis-immune patients cross-reacted with CrpA of C. pneumoniae, indicating that some of chlamydial surface molecules share antigenic epitopes. In contrast, the VD2, as well as the VD3, regions of the MOMP of C. pneumoniae were only recognized by C. pneumoniae-positive sera, suggesting the existence of species-specific epitopes. The identification of such epitopes of cell surface molecules provides new insights into C. pneumoniae-specific immune responses and may be of value for the improvement of C. pneumoniae-specific diagnostic assay systems based on defined recombinant antigens.
Collapse
Affiliation(s)
- Marcus Klein
- Institute for Medical Microbiology, Immunology, and Hygiene, University of Cologne, 50935 Cologne, Germany.
| | | | | | | |
Collapse
|
11
|
Héchard C, Grépinet O, Rodolakis A. Evaluation of protection against Chlamydophila abortus challenge after DNA immunization with the major outer-membrane protein-encoding gene in pregnant and non-pregnant mice. J Med Microbiol 2003; 52:35-40. [PMID: 12488563 DOI: 10.1099/jmm.0.04983-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The protective effect of DNA vaccination with the gene encoding the major outer-membrane protein (MOMP) of Chlamydophila abortus has been studied in non-pregnant and pregnant mouse models after chlamydial challenge. OF1 outbred mice were vaccinated intramuscularly three times every 3 weeks, mated and challenged with C. abortus 2 weeks after the last injection of DNA. In non-pregnant mice, the MOMP DNA vaccine elicited a specific humoral response with predominantly IgG2a antibodies, suggesting a Th1-type immune response. The induced antibodies showed no in vitro neutralizing effect on C. abortus infectivity. Moreover, immunization with the momp gene showed no reduction in the mean splenic bacterial counts of non-pregnant or pregnant mice or in the mean placental bacterial counts of pregnant mice after the C. abortus challenge. Nevertheless, the MOMP DNA immunization induced a non-specific and partial protection in fetuses against challenge.
Collapse
MESH Headings
- Abortion, Spontaneous/immunology
- Abortion, Spontaneous/microbiology
- Abortion, Spontaneous/prevention & control
- Animals
- Animals, Outbred Strains
- Antibodies, Bacterial/immunology
- Antigens, Bacterial/genetics
- Antigens, Bacterial/immunology
- Bacterial Outer Membrane Proteins/genetics
- Bacterial Outer Membrane Proteins/immunology
- Chlamydophila/immunology
- Chlamydophila Infections/immunology
- Chlamydophila Infections/prevention & control
- Female
- Fetus/immunology
- Fetus/microbiology
- Immunoglobulin G/immunology
- Membrane Proteins/genetics
- Membrane Proteins/immunology
- Mice
- Placenta/microbiology
- Pregnancy
- Pregnancy Complications, Infectious/immunology
- Pregnancy Complications, Infectious/microbiology
- Pregnancy Complications, Infectious/prevention & control
- Spleen/microbiology
- Time Factors
- Vaccines, DNA/genetics
- Vaccines, DNA/immunology
Collapse
Affiliation(s)
- Céline Héchard
- Unité de Pathologie Infectieuse et Immunologie, INRA - Centre de Tours, 37380 Nouzilly, France
| | | | | |
Collapse
|
12
|
Abstract
The ultimate goal of current chlamydial vaccine efforts is to utilise either conventional or modern vaccinology approaches to produce a suitable immunisation regimen capable of inducing a sterilising, long-lived heterotypic protective immunity at mucosal sites of infection to curb the severe morbidity and worldwide prevalence of chlamydial infections. This lofty goal poses tremendous challenges that include the need to clearly define the relevant effectors mediating immunity, the antigens responsible for inducing these effectors, the anti-chlamydial action(s) of effectors, and establishment of the most effective method of vaccine delivery. Tackling these challenges is further compounded by the biological complexity of chlamydia, the existence of multiple serovariants, the capacity to induce both protective and deleterious immune effectors, and the occurrence of asymptomatic and persistent infections. Thus, novel molecular, immunological and genetic approaches are urgently needed to extend the frontiers of current knowledge, and develop new paradigms to guide the production of an effective vaccine regimen. Progress made in the last 15 years has culminated in various paradigm shifts in the approaches to designing chlamydial vaccines. The dawn of the current immunological paradigm for antichlamydial vaccine design has its antecedence in the recognition that chlamydial immunity is mediated primarily by a T helper type1 (Th1) response, requiring the induction and recruitment of specific T cells into the mucosal microenvironment. Additionally, the ancillary role of humoral immune response in complementing the Th1-driven protective immunity, through ensuring adequate memory and optimal Th1 response during a reinfection, has been recognised. With continued progress in chlamydial genomics and proteomics, select chlamydial proteins, including structural, membrane and secretory proteins, are being targeted as potential subunit vaccine candidates. However, the development of an effective adjuvant, delivery vehicle or system for a potential subunit vaccine is still an elusive objective in these efforts. Promising delivery vehicles include DNA and virus vectors, bacterial ghosts and dendritic cells. Finally, a vaccine still represents the best approach to protect the greatest number of people against the ocular, pulmonary and genital diseases caused by chlamydial infections. Therefore, considering the urgency and the enormity of these challenges, a partially protective vaccine preventing certain severe sequelae would constitute an acceptable short-term goal to control Chlamydia. However, more research efforts and support are needed to achieve the worthy goal of protecting a significant number of the world's population from the devastating consequences of chlamydial invasion of the human mucosal epithelia.
Collapse
Affiliation(s)
- Joseph U Igietseme
- Microbiology & Immunology, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, Georgia 30310, USA.
| | | | | |
Collapse
|
13
|
The lipid bilayer concept and its experimental realization: from soap bubbles, kitchen sink, to bilayer lipid membranes. J Memb Sci 2001. [DOI: 10.1016/s0376-7388(01)00394-5] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
14
|
Tanzer RJ, Longbottom D, Hatch TP. Identification of polymorphic outer membrane proteins of Chlamydia psittaci 6BC. Infect Immun 2001; 69:2428-34. [PMID: 11254603 PMCID: PMC98175 DOI: 10.1128/iai.69.4.2428-2434.2001] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genomes of Chlamydia spp. encode a family of putative outer membrane proteins, referred to as polymorphic outer membrane proteins (POMPs), which may play a role in the avoidance of host immune defenses. We analyzed avian strain 6BC of Chlamydia psittaci by polyacrylamide gel electrophoresis for the expression of POMPs. At least six putative POMPs were identified on the basis of their size (90 to 110 kDa) and labeling with an outer membrane-specific probe, 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine. Three of the putative POMPs reacted with antiserum raised against a recombinant ovine C. psittaci strain POMP, and two possessed surface-exposed, trypsin-sensitive sites. The POMPs were dependent on disulfide bonds for their maintenance in sodium lauryl sarcosine- and sodium dodecyl sulfate-insoluble complexes but did not appear to be interpeptide disulfide bond cross-linked. The putative POMPs were found to be synthesized during the late phase of the chlamydial developmental cycle, cotemporally with the cysteine-rich doublet periplasmic proteins.
Collapse
Affiliation(s)
- R J Tanzer
- Department of Molecular Sciences, University of Tennessee Center for Health Sciences, Memphis, Tennessee 38163, USA
| | | | | |
Collapse
|
15
|
Hughes ES, Shaw KM, Ashley RH. Mutagenesis and functional reconstitution of chlamydial major outer membrane proteins: VS4 domains are not required for pore formation but modify channel function. Infect Immun 2001; 69:1671-8. [PMID: 11179342 PMCID: PMC98071 DOI: 10.1128/iai.69.3.1671-1678.2001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chlamidial organisms are obligate intracellular pathogens containing highly antigenic porin-like major outer membrane proteins (MOMPs). MOMP epitopes are of substantial medical interest, and they cluster within four relatively short variable (VS) domains. If MOMPs adopt a beta-barrel fold, like bacterial porins, the VS domains may form extramembranous loops and the conserved regions of the protein may correspond to predicted membrane-located beta-strands. However, molecular studies on native MOMPs have been hampered by the need to culture chlamydiae in eukaryotic host cells and purification and reconstitution remain problematic. In addition, the organisms are difficult to manipulate genetically, and it has also been difficult to functionally reconstitute recombinant MOMPs. To help overcome these problems and improve our understanding of MOMP structure and function, we cloned and expressed C. trachomatis and C. psittaci MOMPs and functionally reconstituted them at the single-channel level. We measured significant functional differences between the two proteins, and by removing and exchanging VS4, we tested the hypothesis that the largest variable domain forms an extramembranous loop that contributes to these differences. Proteins in which VS4 was deleted continued to form functional ion channels, consistent with the idea that the domain forms an extramembranous protein loop and incompatible with models in which it contributes to predicted membrane-located beta-strands. Additionally, the properties of the chimeric proteins strongly suggested that the VS4 domain interacts closely with other regions of the protein to form the channel entrance or vestibule. Our approach can be used to probe structure-function relationships in chlamydial MOMPs and may have implications for the generation of effective antichlamydial vaccines.
Collapse
Affiliation(s)
- E S Hughes
- Department of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | | | | |
Collapse
|
16
|
Vretou E, Psarrou E, Kaisar M, Vlisidou I, Salti-Montesanto V, Longbottom D. Identification of protective epitopes by sequencing of the major outer membrane protein gene of a variant strain of Chlamydia psittaci serotype 1 (Chlamydophila abortus). Infect Immun 2001; 69:607-12. [PMID: 11119563 PMCID: PMC97929 DOI: 10.1128/iai.69.1.607-612.2001] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protective monoclonal antibodies (MAbs) to the major outer membrane protein (MOMP) of species of the family Chlamydiaceae, which is the primary vaccine candidate antigen, recognize nonlinear epitopes conferred by the oligomeric conformation of the molecule. Protective MAbs failed to recognize oligomeric MOMP of the variant strain LLG, which bears amino acid substitutions in variable segments (VSs) 1, 2, and 4, and competed with monomer-specific MAbs mapping to these VSs in reference strain 577. The results suggest that multiple sites located in the three VSs contribute to the epitope of protective MAbs.
Collapse
Affiliation(s)
- E Vretou
- Department of Microbiology, Hellenic Pasteur Institute, Athens 115 21, Greece.
| | | | | | | | | | | |
Collapse
|
17
|
Jones HM, Kubo A, Stephens RS. Design, expression and functional characterization of a synthetic gene encoding the Chlamydia trachomatis major outer membrane protein. Gene 2000; 258:173-81. [PMID: 11111055 DOI: 10.1016/s0378-1119(00)00367-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A synthetic gene coding for the Chlamydia trachomatis serovar L2 major outer membrane protein (MOMP) was designed, constructed and expressed in Escherichia coli. The native amino acid sequence was reverse translated and the resulting nucleotide combinations manipulated in order to evenly distribute 25 unique restriction sites along the length of the gene while retaining the native amino acid sequence. The synthetic gene was cloned into a T7 promoter-controlled plasmid (pET-3a) and the expressed product was analyzed to assess antigenicity, cellular localization and function. Monoclonal antibodies specific for native MOMP reacted to the expressed product by immunoblot. Outer membrane fractionation confirmed that the processed protein was located in the outer membrane. MOMP expressed in E. coli and present in the outer membrane was shown to function as a general diffusion porin. This system provides the means to produce readily modifiable MOMP either in purified form or as a membrane-associated protein, and so facilitate the investigation of its functional, structural and antigenic properties.
Collapse
Affiliation(s)
- H M Jones
- Francis I. Proctor Foundation and the Department of Laboratory Medicine, University of California, San Francisco, CA 94143, USA
| | | | | |
Collapse
|
18
|
Abstract
beta-Barrel proteins are found in the outer membranes of bacteria, mitochondria and chloroplasts. The presently known sizes range from small eight-stranded to large twenty-two-stranded beta barrels existing as monomers and oligomers. Their functions are as diverse as active ion transport, passive nutrient intake, membrane anchors, membrane-bound enzymes and defense against attack proteins. Of further interest are the folding process, the crystallization, the observed limited structural diversity and the manifold channel engineering options of these beta-barrel proteins.
Collapse
Affiliation(s)
- G E Schulz
- Institut für Organische Chemie und Biochemie, Freiburg im Breisgau, Germany.
| |
Collapse
|