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von Mentzer A, Svennerholm AM. Colonization factors of human and animal-specific enterotoxigenic Escherichia coli (ETEC). Trends Microbiol 2024; 32:448-464. [PMID: 38052687 DOI: 10.1016/j.tim.2023.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 11/01/2023] [Accepted: 11/07/2023] [Indexed: 12/07/2023]
Abstract
Colonization factors (CFs) are major virulence factors of enterotoxigenic Escherichia coli (ETEC). This pathogen is among the most common causes of bacterial diarrhea in children in low- and middle-income countries, travelers, and livestock. CFs are major candidate antigens in vaccines under development as preventive measures against ETEC infections in humans and livestock. Recent molecular studies have indicated that newly identified CFs on human ETEC are closely related to animal ETEC CFs. Increased knowledge of pathogenic mechanisms, immunogenicity, regulation, and expression of ETEC CFs, as well as the possible spread of animal ETEC to humans, may facilitate the future development of ETEC vaccines for humans and animals. Here, we present an updated review of CFs in ETEC.
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Affiliation(s)
- Astrid von Mentzer
- Department of Microbiology and Immunology, Sahlgrenska Academy, University of Gothenburg, Sweden; Wellcome Sanger Institute, Hinxton, UK.
| | - Ann-Mari Svennerholm
- Department of Microbiology and Immunology, Sahlgrenska Academy, University of Gothenburg, Sweden
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2
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Qi H, Zhang Z, Zhang X, Li B, Li L. Two Dipeptide-Bound Pyrralines with Ile or Ala: A Study on Their Synthesis, Transport across Caco-2 Cell Monolayers, and Interaction with Aminopeptidase N. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:10962-10973. [PMID: 34493043 DOI: 10.1021/acs.jafc.1c03773] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In this study, pyrralylisoleucine (Pyrr-Ile) and pyrralylalanine (Pyrr-Ala), two dipeptide-bound pyrralines with different C-termini were synthesized as the representatives of dietary advanced glycation end products (dAGEs). The structures of Pyrr-Ile and Pyrr-Ala were characterized by high-resolution mass spectrometry, nuclear magnetic resonance, and Fourier transform infrared spectroscopy. Then, the transport of Pyrr-Ile and Pyrr-Ala across intestinal epithelial cells was investigated using Caco-2 cell monolayers, and their interaction with aminopeptidase N (APN) was analyzed. The results showed that the apparent permeability coefficient (Papp) of Pyrr-Ala was (14.1 ± 2.26) × 10-7 cm·s-1 calculated by free pyrraline, while the Papp values of Pyrr-Ile were (32.4 ± 5.35) × 10-7 and (19.1 ± 1.46) × 10-7 cm·s-1 when they were, respectively, calculated according to their dipeptide-bound or free form. Both Pyrr-Ala and Pyrr-Ile were potential substrates of APN, and their hydrolysis by APN may make the intact transmembrane transport of Pyrr-Ala and Pyrr-Ile more difficult, especially for Pyrr-Ala. Besides, the occurrence of product inhibition in hydrolysis of Pyrr-Ile was possible. Pyrr-Ile and Pyrr-Ala were different in Papp values and transport forms, which suggested that the C-terminus may play an important role in their transport across the Caco-2 cell monolayers. In addition, the results highlight the intact transmembrane transport of dipeptide-bound pyrraline.
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Affiliation(s)
- Haiping Qi
- School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Ministry of Education Engineering Research Center of Starch & Protein Processing, South China University of Technology, Guangzhou 510640, China
| | - Zhenhui Zhang
- School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Ministry of Education Engineering Research Center of Starch & Protein Processing, South China University of Technology, Guangzhou 510640, China
| | - Xia Zhang
- School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Ministry of Education Engineering Research Center of Starch & Protein Processing, South China University of Technology, Guangzhou 510640, China
| | - Bing Li
- School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Ministry of Education Engineering Research Center of Starch & Protein Processing, South China University of Technology, Guangzhou 510640, China
| | - Lin Li
- School of Food Science and Engineering, Guangdong Province Key Laboratory for Green Processing of Natural Products and Product Safety, Ministry of Education Engineering Research Center of Starch & Protein Processing, South China University of Technology, Guangzhou 510640, China
- School of Chemical Engineering and Energy Technology, Dongguan University of Technology, College Road 1, Dongguan 523808, China
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3
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Xia P, Wu Y, Lian S, Quan G, Wang Y, Zhu G. Deletion of FaeG alleviated Enterotoxigenic Escherichia coli F4ac-induced apoptosis in the intestine. AMB Express 2021; 11:44. [PMID: 33738650 PMCID: PMC7973317 DOI: 10.1186/s13568-021-01201-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 03/03/2021] [Indexed: 12/19/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) F4ac is a major constraint to the development of the pig industry, which is causing newborn and post-weaning piglets diarrhea. Previous studies proved that FaeG is the major fimbrial subunit of F4ac E. coli and efficient for bacterial adherence and receptor recognition. Here we show that the faeG deletion attenuates both the clinical symptoms of F4ac infection and the F4ac-induced intestinal mucosal damage in piglets. Antibody microarray analysis and the detection of mRNA expression using porcine neonatal jejunal IPEC-J2 cells also determined that the absence of FaeG subunit alleviated the F4ac promoted apoptosis in the intestinal epithelial cells. Thus, targeted depletion of FaeG is still beneficial for the prevention or treatment of F4ac infection.
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Xia P, Lian S, Wu Y, Yan L, Quan G, Zhu G. Zinc is an important inter-kingdom signal between the host and microbe. Vet Res 2021; 52:39. [PMID: 33663613 PMCID: PMC7931793 DOI: 10.1186/s13567-021-00913-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 02/08/2021] [Indexed: 12/15/2022] Open
Abstract
Zinc (Zn) is an essential trace element in living organisms and plays a vital role in the regulation of both microbial virulence and host immune responses. A growing number of studies have shown that zinc deficiency or the internal Zn concentration does not meet the needs of animals and microbes, leading to an imbalance in zinc homeostasis and intracellular signalling pathway dysregulation. Competition for zinc ions (Zn2+) between microbes and the host exists in the use of Zn2+ to maintain cell structure and physiological functions. It also affects the interplay between microbial virulence factors and their specific receptors in the host. This review will focus on the role of Zn in the crosstalk between the host and microbe, especially for changes in microbial pathogenesis and nociceptive neuron-immune interactions, as it may lead to new ways to prevent or treat microbial infections.
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Affiliation(s)
- Pengpeng Xia
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Yangzhou, 225009, China. .,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China. .,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China.
| | - Siqi Lian
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Yunping Wu
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Li Yan
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Guomei Quan
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Yangzhou, 225009, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Guoqiang Zhu
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, Yangzhou, 225009, China. .,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China. .,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China.
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Cruz-Pulido D, Boley PA, Ouma WZ, Alhamo MA, Saif LJ, Kenney SP. Comparative Transcriptome Profiling of Human and Pig Intestinal Epithelial Cells after Porcine Deltacoronavirus Infection. Viruses 2021; 13:v13020292. [PMID: 33668405 PMCID: PMC7918119 DOI: 10.3390/v13020292] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/05/2021] [Accepted: 02/09/2021] [Indexed: 01/16/2023] Open
Abstract
Porcine deltacoronavirus (PDCoV) is an emerging infectious disease of swine with zoonotic potential. Phylogenetic analysis suggests that PDCoV originated recently from a host-switching event between birds and mammals. Little is known about how PDCoV interacts with its differing hosts. Human-derived cell lines are susceptible to PDCoV infection. Herein, we compare the gene expression profiles of an established host swine cells to potential emerging host human cells after infection with PDCoV. Cell lines derived from intestinal lineages were used to reproduce the primary sites of viral infection in the host. Porcine intestinal epithelial cells (IPEC-J2) and human intestinal epithelial cells (HIEC) were infected with PDCoV. RNA-sequencing was performed on total RNA extracted from infected cells. Human cells exhibited a more pronounced response to PDCoV infection in comparison to porcine cells with more differentially expressed genes (DEGs) in human, 7486, in comparison to pig cells, 1134. On the transcriptional level, the adoptive host human cells exhibited more DEGs in response to PDCoV infection in comparison to the primary pig host cells, where different types of cytokines can control PDCoV replication and virus production. Key immune-associated DEGs and signaling pathways are shared between human and pig cells during PDCoV infection. These included genes related to the NF-kappa-B transcription factor family, the interferon (IFN) family, the protein-kinase family, and signaling pathways such as the apoptosis signaling pathway, JAK-STAT signaling pathway, inflammation/cytokine–cytokine receptor signaling pathway. MAP4K4 was unique in up-regulated DEGs in humans in the apoptosis signaling pathway. While similarities exist between human and pig cells in many pathways, our research suggests that the adaptation of PDCoV to the porcine host required the ability to down-regulate many response pathways including the interferon pathway. Our findings provide an important foundation that contributes to an understanding of the mechanisms of PDCoV infection across different hosts. To our knowledge, this is the first report of transcriptome analysis of human cells infected by PDCoV.
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Affiliation(s)
- Diana Cruz-Pulido
- Department of Veterinary Preventive Medicine, Food Animal Health Research Program (FAHRP), Wooster, OH 44691, USA; (D.C.-P.); (P.A.B.); (M.A.A.); (L.J.S.)
| | - Patricia A. Boley
- Department of Veterinary Preventive Medicine, Food Animal Health Research Program (FAHRP), Wooster, OH 44691, USA; (D.C.-P.); (P.A.B.); (M.A.A.); (L.J.S.)
| | | | - Moyasar A. Alhamo
- Department of Veterinary Preventive Medicine, Food Animal Health Research Program (FAHRP), Wooster, OH 44691, USA; (D.C.-P.); (P.A.B.); (M.A.A.); (L.J.S.)
| | - Linda J. Saif
- Department of Veterinary Preventive Medicine, Food Animal Health Research Program (FAHRP), Wooster, OH 44691, USA; (D.C.-P.); (P.A.B.); (M.A.A.); (L.J.S.)
| | - Scott P. Kenney
- Department of Veterinary Preventive Medicine, Food Animal Health Research Program (FAHRP), Wooster, OH 44691, USA; (D.C.-P.); (P.A.B.); (M.A.A.); (L.J.S.)
- Correspondence: ; Tel.: +1-330-263-3747
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Van der Weken H, Cox E, Devriendt B. Advances in Oral Subunit Vaccine Design. Vaccines (Basel) 2020; 9:1. [PMID: 33375151 PMCID: PMC7822154 DOI: 10.3390/vaccines9010001] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/17/2020] [Accepted: 12/19/2020] [Indexed: 02/06/2023] Open
Abstract
Many pathogens invade the host at the intestinal surface. To protect against these enteropathogens, the induction of intestinal secretory IgA (SIgA) responses is paramount. While systemic vaccination provides strong systemic immune responses, oral vaccination is the most efficient way to trigger protective SIgA responses. However, the development of oral vaccines, especially oral subunit vaccines, is challenging due to mechanisms inherent to the gut. Oral vaccines need to survive the harsh environment in the gastrointestinal tract, characterized by low pH and intestinal proteases and need to reach the gut-associated lymphoid tissues, which are protected by chemical and physical barriers that prevent efficient uptake. Furthermore, they need to surmount default tolerogenic responses present in the gut, resulting in suppression of immunity or tolerance. Several strategies have been developed to tackle these hurdles, such as delivery systems that protect vaccine antigens from degradation, strong mucosal adjuvants that induce robust immune responses and targeting approaches that aim to selectively deliver vaccine antigens towards specific immune cell populations. In this review, we discuss recent advances in oral vaccine design to enable the induction of robust gut immunity and highlight that the development of next generation oral subunit vaccines will require approaches that combines these solutions.
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Affiliation(s)
| | | | - Bert Devriendt
- Department of Virology, Parasitology and Immunology, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium; (H.V.d.W.); (E.C.)
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Quan G, Xia P, Lian S, Wu Y, Zhu G. Zinc uptake system ZnuACB is essential for maintaining pathogenic phenotype of F4ac + enterotoxigenic E. coli (ETEC) under a zinc restricted environment. Vet Res 2020; 51:127. [PMID: 33028391 PMCID: PMC7539401 DOI: 10.1186/s13567-020-00854-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 09/22/2020] [Indexed: 01/19/2023] Open
Abstract
Zinc is the second trace element of living organisms after iron. Given its crucial importance, mammalian hosts restrict the bioavailability of Zinc ions (Zn2+) to bacterial pathogens. As a countermeasure, pathogens utilize high affinity Zn2+ transporters, such as ZnuACB to compete with the host for zinc. It is essential for bacteria to maintain zinc homeostasis and thus maintain their physiology and pathogenesis. In an attempt to uncover the zinc transporter in F4+ enterotoxigenic E. coli (ETEC) C83902, we analyzed two RNA-seq data sets of bacteria samples when different zinc treatments (restriction or abundance) were applied. Considering data revealing that the high affinity zinc uptake system ZnuACB acts as the main transporter in ETEC C83902 to resist zinc deficiency, we deleted znuACB genes to study the role of them in ETEC C83902. The deletion of znuACB genes results in growth perturbation and a sharp decrease in the ability of biofilm formation and adhesion of bacteria in vitro. Taking the data together, this study demonstrates that the ZnuACB system is required for ETEC C83902 to acquire zinc, which highly contributes to ETEC pathogenicity as well.
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Affiliation(s)
- Guomei Quan
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, 12 East Wenhui Road, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Pengpeng Xia
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, 12 East Wenhui Road, Yangzhou, 225009, China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China. .,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China.
| | - Siqi Lian
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, 12 East Wenhui Road, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Yunping Wu
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, 12 East Wenhui Road, Yangzhou, 225009, China.,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Guoqiang Zhu
- College of Veterinary Medicine (Institute of Comparative Medicine), Yangzhou University, 12 East Wenhui Road, Yangzhou, 225009, China. .,Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, 225009, China. .,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China.
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8
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Chen J, Pan K, Chen Z, Li Y, Ding B, Han C, Cao Z, Bao W, Zhang Y. Production of porcine aminopeptidase N (pAPN) site-specific edited pigs. Anim Sci J 2019; 90:366-371. [PMID: 30623527 PMCID: PMC7159506 DOI: 10.1111/asj.13163] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2018] [Revised: 11/26/2018] [Accepted: 11/30/2018] [Indexed: 12/26/2022]
Abstract
Porcine viral diarrhea is an acute and highly contagious enteric disease in pigs which causes huge economic losses in pig industry worldwide. Transmissible gastroenteritis virus (TGEV) is main pathogens responsible for piglets viral diarrhea. Knockout the host cellular surface receptor for TGEV may be an effective way to accelerate the breeding of resistant pigs. In this study, we applied site‐specific editing pAPN which is effective in swine testis (ST) cells. Site‐specific editing of pAPN reduced TGEV proliferation in ST cells by 96%–99% at different time periods post‐infection. Next, the site‐specific editing of pAPN porcine fetal fibroblasts were produced, and then the cell colonies were used as donor cells to generate the site‐specific editing of pAPN pigs. Our research findings will not only offer a more thorough understanding of the pathogenesis of piglet diarrhea and lay the foundation for breeding TGEV‐resistant piglets, but also understanding the molecular mechanisms involved in coronaviral infections.
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Affiliation(s)
- Jianwen Chen
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Kaiyuan Pan
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Zhen Chen
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Yunsheng Li
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Biao Ding
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Chunyang Han
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Zubing Cao
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
| | - Wenbin Bao
- College of Animal Science and Technology, Yangzhou University, Yangzhou, Jiangsu, China
| | - Yunhai Zhang
- Anhui Provincial Laboratory of Local Livestock and Poultry Genetical Resource Conservation and Breeding, College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, China
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9
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Binding determinants in the interplay between porcine aminopeptidase N and enterotoxigenic Escherichia coli F4 fimbriae. Vet Res 2018; 49:23. [PMID: 29482635 PMCID: PMC5828407 DOI: 10.1186/s13567-018-0519-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 02/06/2018] [Indexed: 11/25/2022] Open
Abstract
The binding of F4+ enterotoxigenic Escherichia coli (ETEC) and the specific receptor on porcine intestinal epithelial cells is the initial step in F4+ ETEC infection. Porcine aminopeptidase N (APN) is a newly discovered receptor for F4 fimbriae that binds directly to FaeG adhesin, which is the major subunit of the F4 fimbriae variants F4ab, F4ac, and F4ad. We used overlapping peptide assays to map the APN-FaeG binding sites, which has facilitated in the identifying the APN-binding amino acids that are located in the same region of FaeG variants, thereby limiting the major binding regions of APN to 13 peptides. To determine the core sequence motif, a panel of FaeG peptides with point mutations and FaeG mutants were constructed. Pull-down and binding reactivity assays using piglet intestines determined that the amino acids G159 of F4ab, N209 and L212 of F4ac, and A200 of F4ad were the critical residues for APN binding of FaeG. We further show using ELISA and confocal microscopy assay that amino acids 553–568, and 652–670 of the APN comprise the linear epitope for FaeG binding in all three F4 fimbriae variants.
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