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A systematic approach toward stabilization of CagL, a protein antigen from Helicobacter pylori that is a candidate subunit vaccine.

ABSTRACT: An important consideration in the development of subunit vaccines is the loss of activity caused by physical instability of the protein. Such instability often results from suboptimal solution conditions related to pH and temperature. Excipients can help to stabilize vaccines, but it is important to screen and identify excipients that adequately contribute to stabilization of a given formulation. CagL is a protein present in strains of Helicobacter pylori (H. pylori) that possess type IV secretion systems. It contributes to bacterial adherence via ?5?1 integrin, thereby making it an attractive subunit vaccine candidate. We characterized the stability of CagL in different pH and temperature conditions using a variety of spectroscopic techniques. Stability was assessed in terms of transition temperature with the accumulated data, and then incorporated into an empirical phase diagram (EPD) that provided an overview of CagL physical stability. These analyses indicated maximum CagL stability at pH 4-6 up to 40°C in the absence of excipient. Using this EPD analysis, aggregation assays were developed to screen a panel of excipients with some found to inhibit CagL aggregation. Candidate stabilizers were selected to confirm their enhanced stabilizing effect. These analyses will help in the formulation of a stable vaccine against H. pylori.

SUBMITTER: Choudhari SP

PROVIDER: S-EPMC3903303 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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A systematic approach toward stabilization of CagL, a protein antigen from Helicobacter pylori that is a candidate subunit vaccine.

Choudhari Shyamal P SP Pendleton Kirk P KP Ramsey Joshua D JD Blanchard Thomas G TG Picking William D WD

Journal of pharmaceutical sciences 20130621 8

An important consideration in the development of subunit vaccines is the loss of activity caused by physical instability of the protein. Such instability often results from suboptimal solution conditions related to pH and temperature. Excipients can help to stabilize vaccines, but it is important to screen and identify excipients that adequately contribute to stabilization of a given formulation. CagL is a protein present in strains of Helicobacter pylori (H. pylori) that possess type IV secreti ...[more]

PMID: 23794457

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Project description:Helicobacter pylori is a specific gastric pathogen that colonizes the stomach in more than 50% of the world's human population. Infection with this bacterium can induce several types of gastric pathology, ranging from chronic gastritis to peptic ulcers and even adenocarcinoma. Virulent H. pylori isolates encode components of a type IV secretion system (T4SS), which form a pilus for the injection of virulence proteins such as CagA into host target cells. This is accomplished by a specialized adhesin on the pilus surface, the protein CagL, a putative VirB5 ortholog, which binds to host cell ?(1) integrin, triggering subsequent delivery of CagA across the host cell membrane. Like the human extracellular matrix protein fibronectin, CagL contains an RGD (Arg-Gly-Asp) motif and is able to trigger intracellular signaling pathways by RGD-dependent binding to integrins. While CagL binding to host cells is mediated primarily by the RGD motif, we identified an auxiliary binding motif for CagL-integrin interaction. Here, we report on a surface exposed FEANE (Phe-Glu-Ala-Asn-Glu) interaction motif in spatial proximity to the RGD sequence, which enhances the interactions of CagL with integrins. It will be referred to as RGD helper sequence (RHS). Competitive cell adhesion assays with recombinant wild type CagL and point mutants, competition experiments with synthetic cyclic and linear peptides, and peptide array experiments revealed amino acids essential for the interaction of the RHS motif with integrins. Infection experiments indicate that the RHS motif plays a role in the early interaction of H. pylori T4SS with integrin, to trigger signaling and to inject CagA into host cells. We thus postulate that CagL is a versatile T4SS surface protein equipped with at least two motifs to promote binding to integrins, thereby causing aberrant signaling within host cells and facilitating translocation of CagA into host cells, thus contributing directly to H. pylori pathogenesis.

Project description:AIM:To construct a recombinant vector which can express outer membrane protein (OMP) with M(r)18,000 and heat shock protein A (HspA) from Helicobacter pylori (H. pylori) in E. coli BL21, and to exploit the possibility for obtaining the vaccine conferring protection from H. pylori infection. METHODS:The target gene of HspA was amplified from H. pylori chromosome by PCR, and then inserted into the prokaryotic expression vector pET32a (+) by restrictive endonuclease enzyme kpn I, BamH I simultaneously. The recombinant vector was used to sequence, and then together with pET32a (+)/Omp(18), digested by restrictive endonuclease enzyme Hind III and BamH I simultaneously. pET32a(+)/HspA and Omp(18) were recovered from 1 % agarose gel by gel kit, and ligated with T(4) ligase by BamH I digested viscidity end. The recombinant plasmid of pET32a(+)/HspA/Omp(18) was transformed and expressed in E. coli BL21 (DE3) under induction of IPTG. After purification, its antigenicity of the fusion protein was detected by Western blot. RESULTS:Enzyme digestion analysis and sequencing showed that the target genes were inserted into the recombinant vector, composed of 891 base pairs, encoded objective polypeptides of 297 amino acid residues. Compared with GenBank reported by Tomb et al, there were 1.3 % and 1.4 % differences in obtained H. pylori nucleotide sequence and amino acid residues, respectively. SDS-PAGE analysis showed that relative molecule mass (M(r)) of the expressed product was M(r) 51,000, M(r) of protein expressed by pET32a (+) was about M(r) 20,000, and soluble expression product accounted for 18.96 % of total bacterial protein. After purification with Ni(+2)-NTA agarose resins, the purification of recombinant fusion protein was about 95 %. Western blot showed that recombinant fusion protein could be recognized by the patients' serum infected with H. pylori and anti-Omp(18) monoclone, suggesting that this protein had good antigenicity. CONCLUSION:The gene coding for H. pylori M(r)18,000 OMP and HspA was cloned and expressed successfully. The results obtained lay the foundation for development of H. pylori protein vaccine and a quick diagnostic kit.

Dataset Information

A systematic approach toward stabilization of CagL, a protein antigen from Helicobacter pylori that is a candidate subunit vaccine.

Publications

A systematic approach toward stabilization of CagL, a protein antigen from Helicobacter pylori that is a candidate subunit vaccine.

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