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. 2024 Apr 9;12(4):398.
doi: 10.3390/vaccines12040398.

Surface-Exposed Protein Moieties of Burkholderia cenocepacia J2315 in Microaerophilic and Aerobic Conditions

Affiliations

Surface-Exposed Protein Moieties of Burkholderia cenocepacia J2315 in Microaerophilic and Aerobic Conditions

António M M Seixas et al. Vaccines (Basel). .

Abstract

Burkholderia cepacia complex infections remain life-threatening to cystic fibrosis patients, and due to the limited eradication efficiency of current treatments, novel antimicrobial therapies are urgently needed. Surface proteins are among the best targets to develop new therapeutic strategies since they are exposed to the host's immune system. A surface-shaving approach was performed using Burkholderia cenocepacia J2315 to quantitatively compare the relative abundance of surface-exposed proteins (SEPs) expressed by the bacterium when grown under aerobic and microaerophilic conditions. After trypsin incubation of live bacteria and identification of resulting peptides by liquid chromatography coupled with mass spectrometry, a total of 461 proteins with ≥2 unique peptides were identified. Bioinformatics analyses revealed a total of 53 proteins predicted as localized at the outer membrane (OM) or extracellularly (E). Additionally, 37 proteins were predicted as moonlight proteins with OM or E secondary localization. B-cell linear epitope bioinformatics analysis of the proteins predicted to be OM and E-localized revealed 71 SEP moieties with predicted immunogenic epitopes. The protegenicity higher scores of proteins BCAM2761, BCAS0104, BCAL0151, and BCAL0849 point out these proteins as the best antigens for vaccine development. Additionally, 10 of the OM proteins also presented a high probability of playing important roles in adhesion to host cells, making them potential targets for passive immunotherapeutic approaches. The immunoreactivity of three of the OM proteins identified was experimentally demonstrated using serum samples from cystic fibrosis patients, validating our strategy for identifying immunoreactive moieties from surface-exposed proteins of potential interest for future immunotherapies development.

Keywords: Burkholderia cenocepacia; aerobic conditions; cystic fibrosis; microaerophilic conditions; surfomics.

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Conflict of interest statement

The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Schematic representation of the cloning of bcal1985 and bcam1931 genes in pET23a+, yielding the plasmids pJMM1 and pJMM2, respectively. In the middle, the agarose gel of the PCR products bcam1931 and bcam1985 is represented. M—Gene Ruler 1kb Plus DNA ladder (20,000–75 bp). The sequencing results from the pJMM1 and pJMM2 using the T7 promoter primer are represented in the bottom boxes.
Figure 2
Figure 2
Schematic representation of the subcellular localization of the proteins identified using the surface-shaving approach, with the number of proteins identified in each environmental condition represented. The programs PsortB v3.0 and LocTree3 were used to predict the subcellular localization. Moonlight proteins with secondary functions at the outer membrane or extracellularly were identified using the Databases MoonProt 3.0 and MultitaskProtDBII. Localization: (C) cytoplasm; (CM) cytoplasmic membrane, (PM) periplasm; (U) unknown; (OM) outer membrane; (E) extracellular.
Figure 3
Figure 3
Subcellular localization of B. cenocepacia J2315 BCAL3146 (GroEL), BCAL2645 (OmpA), and BCAL1538 (HFQ2). After bacterial growth in ASM medium under aerobic conditions, cells were harvested and divided into the following fractions: Cytoplasmic proteins (Lane 1), Outer Membrane proteins (Lane 2), and Extracellular proteins (Lane 3). These fractions were analyzed by SDS-PAGE (A) and by Western blot using the goat IgG antibodies anti-BCAL3146, anti-BCAL2645, or anti-Hfq2 (B). M-PageRulerTM unstained broad-range protein ladder (Thermo Scientific).
Figure 4
Figure 4
Heatmaps of z-scored abundances of identified OM, fimbrial, and flagellar proteins (A), and extracellular proteins (B) in the surface-shaving approach. Proteins are shown in rows, and the surfomics samples are shown in columns in each heatmap. A1, A2, A3 refer to aerobic environment, and M1, M2, M3 refer to microaerophilic environment. The numbers next to the growth condition tested represent each of the three biological replicates. Increasing intensity in the positive range (Orange) exemplifies abundances that are greater than the mean abundance resulting from both conditions relative to the standard deviation associated with the mean. Increasing intensity in the negative range (Blue) represents abundances that are lower than the mean abundance derived from both conditions relative to the standard deviation associated with the mean. * Surfomic samples with no peptide identified for the protein in the analysis.
Figure 5
Figure 5
SDS-PAGE and Western blot of purified recombinant proteins BCAM1931, BCAL1985, and BCAL2645 from B. cenocepacia J2315 probed with the human serum samples SCF1, SCF2, SCF3, SCF4 obtained from CF patients infected with Bcc bacteria or a pool of human serum sample from healthy donors, SH. Lanes: M—PageRuler Unstained Broad Range Protein Ladder (Thermofischer); 1—purified BCAM1931 recombinant protein; 2—purified BCAL1985 recombinant protein; 3—purified BCAL2645 recombinant protein; 4—BSA.

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