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Liu G, Wang K, Yang Z, Tang X, Chang YF, Dai K, Tang X, Hu B, Zhang Y, Cao S, Huang X, Yan Q, Wu R, Zhao Q, Du S, Wen X, Wen Y. Identification of a Novel Linear B-Cell Epitope of HbpA Protein from Glaesserella parasuis Using Monoclonal Antibody. Int J Mol Sci 2023; 24:8638. [PMID: 37239984 PMCID: PMC10218323 DOI: 10.3390/ijms24108638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 04/27/2023] [Accepted: 04/27/2023] [Indexed: 05/28/2023] Open
Abstract
Glaesserella parasuis (G. parasuis.) is the etiological pathogen of Glässer's disease, which causes high economic losses to the pig industry. The heme-binding protein A precursor (HbpA) was a putative virulence-associated factor proposed to be potential subunit vaccine candidate in G. parasuis. In this study, three monoclonal antibodies (mAb) 5D11, 2H81, and 4F2 against recombinant HbpA (rHbpA) of G. parasuis SH0165 (serotype 5) were generated by fusing SP2/0-Ag14 murine myeloma cells and spleen cells from BALB/c mice immunized with the rHbpA. Indirect enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence assay (IFA) demonstrated that the antibody designated 5D11 showed a strong binding affinity with the HbpA protein and was chosen for subsequent experiments. The subtypes of the 5D11 were IgG1/κ chains. Western blot analysis showed that mAb 5D11 could react with all 15 serotype reference strains of G. parasuis. None of the other bacteria tested reacted with 5D11. In addition, a linear B-cell epitope recognized by 5D11 was identified by serial truncations of HbpA protein and then a series of truncated peptides were synthesized to define the minimal region that was required for mAb 5D11 binding. The 5D11 epitope was located on amino acids 324-LPQYEFNLEKAKALLA-339 by testing the 5D11 monoclonal for reactivity with 14 truncations. The minimal epitope 325-PQYEFNLEKAKALLA-339 (designated EP-5D11) was pinpointed by testing the mAb 5D11 for reactivity with a series of synthetic peptides of this region. The epitope was highly conserved among G. parasuis strains, confirmed by alignment analysis. These results indicated that mAb 5D11 and EP-5D11 might potentially be used to develop serological diagnostic tools for G. parasuis. Three-dimensional structural analysis revealed that amino acids of EP-5D11 were in close proximity and may be exposed on the surface of the HbpA protein.
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Affiliation(s)
- Geyan Liu
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Kang Wang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Zhen Yang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Xiaoyu Tang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Yung-Fu Chang
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, New York, NY 14850, USA;
| | - Ke Dai
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Xinwei Tang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Bangdi Hu
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Yiwen Zhang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Sanjie Cao
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Xiaobo Huang
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Qigui Yan
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Rui Wu
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Qin Zhao
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Senyan Du
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Xintian Wen
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
| | - Yiping Wen
- Research Center of Swine Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, China; (G.L.); (K.W.); (Z.Y.); (X.T.); (K.D.); (X.T.); (B.H.); (Y.Z.); (S.C.); (X.H.); (Q.Y.); (R.W.); (Q.Z.); (S.D.); (X.W.)
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Ehrlichia chaffeensis and E. canis hypothetical protein immunoanalysis reveals small secreted immunodominant proteins and conformation-dependent antibody epitopes. NPJ Vaccines 2020; 5:85. [PMID: 32963815 PMCID: PMC7486380 DOI: 10.1038/s41541-020-00231-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 08/12/2020] [Indexed: 01/05/2023] Open
Abstract
Immunomolecular characterization of Ehrlichia chaffeensis (E. ch.) and E. canis (E. ca.) has defined protein orthologs, including tandem repeat proteins (TRPs) that have immunodominant linear antibody epitopes. In this study, we combined bioinformatic analysis and cell-free protein expression to identify undiscovered immunoreactive E. ch. and E. ca. hypothetical proteins. Antigenicity of the E. ch. and E. ca. ORFeomes (n = 1105 and n = 925, respectively) was analyzed by the sequence-based prediction model ANTIGENpro, and we identified ~250 ORFs in each respective ORFeome as highly antigenic. The hypothetical proteins (E. ch. n = 93 and E. ca. n = 98) present in the top 250 antigenic ORFs were further investigated in this study. By ELISA, 46 E. ch. and 30 E. ca. IVTT-expressed hypothetical proteins reacted with antibodies in sera from naturally E. ch.-infected patients or E. ca.-infected dogs. Moreover, 15 E. ch. and 16 E. ca. proteins consistently reacted with a panel of sera from patients or dogs, including many that revealed the immunoreactivity of “gold standard” TRPs. Antibody epitopes in most (>70%) of these proteins exhibited partial or complete conformation-dependence. The majority (23/31; 74%) of the major immunoreactive proteins identified were small (≤250 aa), and 20/31 (65%) were predicted to be secreted effectors. Unlike the strong linear antibody epitopes previously identified in TRP and OMP orthologs, there were contrasting differences in the E. ch. and E. ca. antigenic repertoires, epitopes and ortholog immunoreactivity. This study reveals numerous previously undefined immunodominant and subdominant antigens, and illustrates the breadth, complexity, and diversity of immunoreactive proteins/epitopes in Ehrlichia.
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