Evaluation of an in silico predicted specific and immunogenic antigen from the OmcB protein for the serodiagnosis of Chlamydia trachomatis infections

Frikha‐Gargouri, Olfa; Gdoura, Radhouane; Znazen, Abir; Gargouri, Boutheina; Gargouri, Jalel; Rebai, Ahmed; Hammami, Adnène

doi:10.1186/1471-2180-8-217

Cited by 25 publications

(22 citation statements)

References 62 publications

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“…We have confirmed that OmcB, a chlamydial outer membraneassociated, highly conserved, abundant and immunogenic protein (12,(18)(19)(20)(21)(25)(26)(27)(28), is processed during chlamydial infection since the processing was still detectable after the infected culture samples were harvested in 8 M urea, which has been shown to prevent proteolysis during cell lysis (30). Although we have previously reported that OmcB is partially cleaved (29), careful confirmation of OmcB processing in the current study is still necessary since a recent study has revealed that almost all previously reported protein cleavages in Chlamydia-infected cell samples are due to proteolysis during cell lysis (30).…”

Section: Discussionmentioning

confidence: 62%

“…OmcB may also be involved in the conversion of RBs to EBs (11,17) and contribute to cell wall rigidity and osmotic stability of the EBs (11). OmcB is an immunodominant antigen with both B-cell and T-cell epitopes (18)(19)(20)(21)(22)(23)(24) and has been considered a candidate for developing both serodiagnostics (12,25) and subunit vaccines (26)(27)(28). Nevertheless, there has been considerable debate regarding the precise location and role of OmcB during C. trachomatis infection.…”

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confidence: 99%

“…The chlamydial outer membrane complex protein B (OmcB) is an abundant outer membrane protein (10,11) and highly conserved among Chlamydia species (12), suggesting a significant role of OmcB in chlamydial biology. OmcB has been shown to function as an adhesin for chlamydial invasion into host cells (13,14).…”

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confidence: 99%

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Chlamydia trachomatis Outer Membrane Complex Protein B (OmcB) Is Processed by the Protease CPAF

Hou¹,

Lei²,

Yang³

et al. 2012

Journal of Bacteriology

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bWe previously reported that the Chlamydia trachomatis outer membrane complex protein B (OmcB) was partially processed in Chlamydia-infected cells. We have now confirmed that the OmcB processing occurred inside live cells during chlamydial infection and was not due to proteolysis during sample harvesting. OmcB processing was preceded by the generation of active CPAF, a serine protease known to be able to cross the inner membrane via a Sec-dependent pathway, suggesting that active CPAF is available for processing OmcB in the periplasm. In a cell-free system, CPAF activity is both necessary and sufficient for processing OmcB. Both depletion of CPAF from Chlamydia-infected cell lysates with a CPAF-specific antibody and blocking CPAF activity with a CPAF-specific inhibitory peptide removed the OmcB processing ability of the lysates. A highly purified wild-type CPAF but not a catalytic residue-substituted mutant CPAF was sufficient for processing OmcB. Most importantly, in chlamydial culture, inhibition of CPAF with a specific inhibitory peptide blocked OmcB processing and reduced the recovery of infectious organisms. Thus, we have identified OmcB as a novel authentic target for the putative chlamydial virulence factor CPAF, which should facilitate our understanding of the roles of CPAF in chlamydial biology and pathogenesis.C hlamydia trachomatis is a major cause of bacterial sexually transmitted diseases in the United States (1), which, if untreated, can lead to long-term complications such as pelvic inflammatory diseases, ectopic pregnancy, and infertility (2). It is thought that the inflammatory responses induced by the obligate intracellular growth of C. trachomatis significantly contribute to the pathogenicity (3-5). The C. trachomatis organisms initiate their intracellular life by invading epithelial cells in the form of elementary bodies (EBs). The intracellular EBs rapidly differentiate into reticulate bodies (RBs) that are metabolically active and able to proliferate. The progeny RBs have to differentiate back into EBs to exit the infected cells and spread to new cells. The EB-to-RB and RB-to-EB conversions require ϳ5-fold volume changes in the bacteria's size. It is not known how these large volume alterations are achieved. Nevertheless, the intracellular life of C. trachomatis organisms occurs strictly inside cytoplasmic vacuoles termed inclusions and takes 48 to 72 h to complete in cell culture systems, during which the intrainclusion chlamydial organisms secrete numerous proteins including the serine protease CPAF via a Secdependent pathway and inclusion membrane proteins via a type III secretion system (6-9). Despite many advances in chlamydial biology, the precise molecular mechanisms of how chlamydial organisms invade epithelial cells, how the intracellular organism differentiation is regulated, and how the intrainclusion organisms communicate with host cells remain unknown.The chlamydial outer membrane complex protein B (OmcB) is an abundant outer membrane protein (10, 11) and highly conserved among...

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Section: Discussionmentioning

confidence: 62%

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confidence: 99%

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Chlamydia trachomatis Outer Membrane Complex Protein B (OmcB) Is Processed by the Protease CPAF

Hou¹,

Lei²,

Yang³

et al. 2012

Journal of Bacteriology

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“…OmcB is highly conserved among Chlamydia species (21), suggesting that it plays a significant role during intracellular chlamydial infection. OmcB may function as an adhesin for chlamydial invasion into host cells (17,18), since heparin can block the infectivity of some C. trachomatis serovars by binding to an N-terminal peptide of OmcB (41,56).…”

mentioning

confidence: 99%

“…Due to its abundance and strong immunogenicity, OmcB has been considered a target for developing both serodiagnosis methods (2,21) and subunit vaccines (15,49,50). Nevertheless, there has been considerable debate regarding the precise location and role of OmcB during C. trachomatis infection.…”

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A Chlamydia trachomatis OmcB C-Terminal Fragment Is Released into the Host Cell Cytoplasm and Is Immunogenic in Humans

Gong

Lei

et al. 2011

Infect Immun

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The Chlamydia trachomatis outer membrane complex protein B (OmcB) is an antigen with diagnostic and vaccine relevance. To further characterize OmcB, we generated antibodies against OmcB C-terminal (OmcBc) and N-terminal (OmcBn) fragments. Surprisingly, the anti-OmcBc antibody detected dominant signals in the host cell cytosol, while the anti-OmcBn antibody exclusively labeled intrainclusion signals in C. trachomatisinfected cells permeabilized with saponin. Western blot analyses revealed that OmcB was partially processed into OmcBc and OmcBn fragments. The processed OmcBc was released into host cell cytosol, while the OmcBn and remaining full-length OmcB were retained within the chlamydial inclusions. The organism-associated OmcB epitopes became detectable only after the C. trachomatis-infected cells were permeabilized with strong detergents such as SDS. However, the harsh permeabilization conditions also led to the leakage of the already secreted OmcBc and chlamydia-secreted protease (CPAF) out of the host cells. The OmcBc processing and release occurred in all biovars of C. trachomatis. Moreover, the released OmcBc but not the retained OmcBn was highly immunogenic in C. trachomatis-infected women, which is consistent with the concept that exposure of chlamydial proteins to host cell cytosol is accompanied by increased immunogenicity. These observations have provided important information for further exploring/optimizing OmcB as a target for the development of diagnosis methods and vaccines.

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Antigenic and conserved peptides from diverse Helicobacter pylori antigens

Calado

2022

Biotechnol Lett

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Since the revolutionary finding of Helicobacter pylori as a common bacterial infection, that a high research effort for its eradication has been conducted. Epitope based-vaccine presents advantages over protein-based, as they can be designed to contain epitopes from diverse proteins, therefore, more easily representing the immune-variability of the bacterial population, while minimizing the toxicity associated to some whole proteins. In the present work, an iterative method, to design antigenic and conserved B-epitopes from diverse virulent factors of H. pylori, was established. The method considered the trade-off between epitopes antigenicity and conservation among the bacterial population. For the method validation, five virulent factors from H. pylori were selected. From each virulent factor, two epitopes were predicted, each with twelve residues of aminoacids. The corresponding ten peptides were synthesised and evaluated by enzyme-linked immunosorbent assay using polyclonal antibodies raised against a specific H. pylori strain. All ten peptides were recognised by the antibodies and were consequently antigenic and conserved. This result could strongly contribute to the design of a multivalent epitope-based vaccine, representing the immunogenetic variability within the bacterial population, leading to a sustained and effective immunogenic protection.

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Evaluation of an in silico predicted specific and immunogenic antigen from the OmcB protein for the serodiagnosis of Chlamydia trachomatis infections

Cited by 25 publications

References 62 publications

Chlamydia trachomatis Outer Membrane Complex Protein B (OmcB) Is Processed by the Protease CPAF

Chlamydia trachomatis Outer Membrane Complex Protein B (OmcB) Is Processed by the Protease CPAF

A Chlamydia trachomatis OmcB C-Terminal Fragment Is Released into the Host Cell Cytoplasm and Is Immunogenic in Humans

Antigenic and conserved peptides from diverse Helicobacter pylori antigens

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