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Krone L, Mahankali S, Geiger T. Cytolysin A is an intracellularly induced and secreted cytotoxin of typhoidal Salmonella. Nat Commun 2024; 15:8414. [PMID: 39341826 PMCID: PMC11438861 DOI: 10.1038/s41467-024-52745-0] [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: 01/16/2024] [Accepted: 09/20/2024] [Indexed: 10/01/2024] Open
Abstract
Typhoidal Salmonella enterica serovars, such as Typhi and Paratyphi A, cause severe systemic infections, thereby posing a significant threat as human-adapted pathogens. This study focuses on cytolysin A (ClyA), a virulence factor essential for bacterial dissemination within the human body. We show that ClyA is exclusively expressed by intracellular S. Paratyphi A within the Salmonella-containing vacuole (SCV), regulated by the PhoP/Q system and SlyA. ClyA localizes in the bacterial periplasm, suggesting potential secretion. Deletion of TtsA, an essential Type 10 Secretion System component, completely abolishes intracellular ClyA detection and its presence in host cell supernatants. Host cells infected with wild-type S. Paratyphi A contain substantial ClyA, with supernatants capable of lysing neighboring cells. Notably, ClyA selectively lyses macrophages and erythrocytes while sparing epithelial cells. These findings identify ClyA as an intracellularly induced cytolysin, dependent on the SCV environment and secreted via a Type 10 Secretion System, with specific cytolytic activity.
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Affiliation(s)
- Lena Krone
- Max von Pettenkofer-Institute, Chair for Medical Microbiology and Hygiene, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany
| | - Srujita Mahankali
- Max von Pettenkofer-Institute, Chair for Medical Microbiology and Hygiene, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany
| | - Tobias Geiger
- Max von Pettenkofer-Institute, Chair for Medical Microbiology and Hygiene, Ludwig-Maximilians-Universität München (LMU Munich), Munich, Germany.
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2
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Pereira-Dias J, Taneja N, Mahindroo J, Maheshwari G, Patel PJ, Thu TNH, Keane J, Dyson ZA, Baker S, Mylona E. The genomic characterization of Salmonella Paratyphi A from an outbreak of enteric fever in Vadodara, India. Microb Genom 2023; 9:mgen000914. [PMID: 36748526 PMCID: PMC9973848 DOI: 10.1099/mgen.0.000914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 10/18/2022] [Indexed: 01/09/2023] Open
Abstract
Salmonella enterica Typhi (S. Typhi) and Paratyphi A (S. Paratyphi A) are the causative agents of enteric fever, a systemic human disease with a burden of 300 000 cases per year in India. The majority of enteric fever cases are associated with S. Typhi, resulting in a paucity of data regarding S. Paratyphi A, specifically with respect to genomic surveillance and antimicrobial resistance (AMR). Here, we exploited whole-genome sequencing (WGS) to identify S. Paratyphi A genotypes and AMR determinants associated with an outbreak of S. Paratyphi A in Vadodara, India, from December 2018 to December 2019. In total 117 S. Paratyphi A were isolated and genome sequenced, most were genotype 2.4.2 (72.6 % of all cases), which is the globally dominant genotype. The remainder were genotype 2.3 (25.6 %), while only two isolates belonged to genotype 2.4.1. A single base-pair mutation in gyrA, associated with reduced susceptibility to fluoroquinolones, was present in all of the outbreak isolates; with 74.35 % of isolates having a S83F substitution and the remainder having an S83Y substitution. Our surveillance study suggests that S. Paratyphi A is an emergent pathogen in South Asia, which may become increasingly relevant with the introduction of Vi conjugate vaccines.
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Affiliation(s)
- Joana Pereira-Dias
- University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
| | - Neelam Taneja
- Post Graduate Institute of Medical Education and Research, Department Medical Microbiology, Chandigarh, India
| | - Jaspreet Mahindroo
- Post Graduate Institute of Medical Education and Research, Department Medical Microbiology, Chandigarh, India
| | - Geeti Maheshwari
- Department of Microbiology, Toprani Advanced Lab Systems, Vadodara, Gujarat, India
| | - Padma J. Patel
- Department of Microbiology, Toprani Advanced Lab Systems, Vadodara, Gujarat, India
| | | | - Jacqui Keane
- University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
| | - Zoe A. Dyson
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK
- Department of Infectious Diseases, Central Clinical School, Monash University, Melbourne, Victoria 3004, Australia
- Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, UK
| | - Stephen Baker
- University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
| | - Elli Mylona
- University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Cambridge, UK
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3
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Ma PY, Tan JE, Hee EW, Yong DWX, Heng YS, Low WX, Wu XH, Cletus C, Kumar Chellappan D, Aung K, Yong CY, Liew YK. Human Genetic Variation Influences Enteric Fever Progression. Cells 2021; 10:cells10020345. [PMID: 33562108 PMCID: PMC7915608 DOI: 10.3390/cells10020345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 02/02/2021] [Accepted: 02/04/2021] [Indexed: 01/06/2023] Open
Abstract
In the 21st century, enteric fever is still causing a significant number of mortalities, especially in high-risk regions of the world. Genetic studies involving the genome and transcriptome have revealed a broad set of candidate genetic polymorphisms associated with susceptibility to and the severity of enteric fever. This review attempted to explain and discuss the past and the most recent findings on human genetic variants affecting the progression of Salmonella typhoidal species infection, particularly toll-like receptor (TLR) 4, TLR5, interleukin (IL-) 4, natural resistance-associated macrophage protein 1 (NRAMP1), VAC14, PARK2/PACRG, cystic fibrosis transmembrane conductance regulator (CFTR), major-histocompatibility-complex (MHC) class II and class III. These polymorphisms on disease susceptibility or progression in patients could be related to multiple mechanisms in eliminating both intracellular and extracellular Salmonella typhoidal species. Here, we also highlighted the limitations in the studies reported, which led to inconclusive results in association studies. Nevertheless, the knowledge obtained through this review may shed some light on the development of risk prediction tools, novel therapies as well as strategies towards developing a personalised typhoid vaccine.
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Affiliation(s)
- Pei Yee Ma
- School of Postgraduate Studies, International Medical University, Bukit Jalil, Kuala Lumpur 57000, Malaysia;
| | - Jing En Tan
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Edd Wyn Hee
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Dylan Wang Xi Yong
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Yi Shuan Heng
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Wei Xiang Low
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Xun Hui Wu
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Christy Cletus
- School of Pharmacy, International Medical University, Kuala Lumpur 57000, Malaysia; (J.E.T.); (E.W.H.); (D.W.X.Y.); (Y.S.H.); (W.X.L.); (X.H.W.); (C.C.)
| | - Dinesh Kumar Chellappan
- Department of Life Sciences, International Medical University, Kuala Lumpur 57000, Malaysia;
| | - Kyan Aung
- Department of Pathology, International Medical University, Kuala Lumpur 57000, Malaysia;
| | - Chean Yeah Yong
- Department of Microbiology, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Selangor 43400, Malaysia;
| | - Yun Khoon Liew
- Department of Life Sciences, International Medical University, Kuala Lumpur 57000, Malaysia;
- Correspondence:
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Generation and Characterization of Typhoid Toxin-Neutralizing Human Monoclonal Antibodies. Infect Immun 2020; 88:IAI.00292-20. [PMID: 32661121 DOI: 10.1128/iai.00292-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 07/06/2020] [Indexed: 11/20/2022] Open
Abstract
Typhoid toxin is a virulence factor of Salmonella enterica serovar Typhi, the causative agent of typhoid fever, and is thought to be responsible for the symptoms of severe disease. This toxin has a unique A2B5 architecture with two active subunits, the ADP ribosyl transferase PltA and the DNase CdtB, linked to a pentameric B subunit, which is alternatively made of PltB or PltC. Here, we describe the generation and characterization of typhoid toxin-neutralizing human monoclonal antibodies by immunizing genetically engineered mice that have a full set of human immunoglobulin variable region genes. We identified several monoclonal antibodies with strong in vitro and in vivo toxin-neutralizing activity and different mechanisms of toxin neutralization. These antibodies could serve as the basis for the development of novel therapeutic strategies against typhoid fever.
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Chromogenic media for the detection of Salmonella enterica serovar Paratyphi A in human stool samples: evaluation in a reference setting. Eur J Clin Microbiol Infect Dis 2018; 37:2181-2190. [PMID: 30151777 DOI: 10.1007/s10096-018-3360-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Accepted: 08/14/2018] [Indexed: 10/28/2022]
Abstract
Detection of Salmonella Paratyphi A stool carriers by conventional stool culture media is hindered by the absence of hydrogen sulphide production compared to most other Salmonella serovars. This study evaluated the detection of Salmonella Paratyphi A in stool samples using Salmonella chromogenic media compared to a conventional medium. Four chromogenic media, COMPASS Salmonella agar (Biokar Diagnostics, Beauvais, France), BBL™ CHROMagar™ Salmonella (BD Diagnostics, Erembodegem-Aalst, Belgium), Brilliance™ Salmonella agar (Oxoid Ltd., Basingstoke, UK) and Salmonella PLUS CHROMagar™ (CHROMagar, Paris, France), were compared to conventional Salmonella-Shigella agar (Oxoid Ltd.). The colony morphology of 29 freshly grown stock isolates (Salmonella and competing organisms) was assessed. The limit of detection (LOD) was also determined using saline and stool suspensions. Finally, recognizability of Salmonella Paratyphi A isolates was assessed using 20 human stool samples spiked with different concentrations of Salmonella Paratyphi A. All Salmonella Paratyphi A isolates demonstrated detectable growth with typical purple-coloured colonies that could be clearly differentiated from competing organisms on all four chromogenic media. The LOD for Salmonella Paratyphi A was 103 colony-forming units (CFU)/ml for all media, except for Brilliance agar (105 CFU/ml of stool). Salmonella Paratyphi A was easy to differentiate from competing organisms in the spiked stool samples. Colony yields improved when an enrichment step (Selenite-F broth (BD Diagnostics, Erembodegem-Aalst, Belgium)) and prolonged incubation for 48 h were performed. Chromogenic media demonstrated good specificity and a low LOD for the detection of Salmonella Paratyphi A in stool samples.
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Abstract
Typhoid and paratyphoid fever may follow a seasonal pattern, but this pattern is not well characterized. Moreover, the environmental drivers that influence seasonal dynamics are not fully understood, although increasing evidence suggests that rainfall and temperature may play an important role. We compiled a database of typhoid, paratyphoid, or enteric fever and their potential environmental drivers. We assessed the seasonal dynamics by region and latitude, quantifying the mean timing of peak prevalence and seasonal variability. Moreover, we investigated the potential drivers of the seasonal dynamics and compared the seasonal dynamics for typhoid and paratyphoid fever. We observed a distinct seasonal pattern for enteric and typhoid fever by latitude, with seasonal variability more pronounced further from the equator. We also found evidence of a positive association between preceding rainfall and enteric fever among settings 35°–11°N and a more consistent positive association between temperature and enteric fever incidence across most regions of the world. In conclusion, we identified varying seasonal dynamics for enteric or typhoid fever in association with environmental factors. The underlying mechanisms that drive the seasonality of enteric fever are likely dependent on the local context and should be taken into account in future control efforts.
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Zellweger RM, Basnyat B, Shrestha P, Prajapati KG, Dongol S, Sharma PK, Koirala S, Darton TC, Dolecek C, Thompson CN, Thwaites GE, Baker SG, Karkey A. A 23-year retrospective investigation of Salmonella Typhi and Salmonella Paratyphi isolated in a tertiary Kathmandu hospital. PLoS Negl Trop Dis 2017; 11:e0006051. [PMID: 29176850 PMCID: PMC5720835 DOI: 10.1371/journal.pntd.0006051] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 12/07/2017] [Accepted: 10/19/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Salmonella serovars Typhi (S. Typhi) and Paratyphi A (S. Paratyphi A), the causative agents of enteric fever, have been routinely isolated organisms from the blood of febrile patients in the Kathmandu Valley since the early 1990s. Susceptibility against commonly used antimicrobials for treating enteric fever has gradually changed throughout South Asia since this time, posing serious treatment challenges. Here, we aimed to longitudinally describe trends in the isolation of Salmonella enterica and assess changes in their antimicrobial susceptibility in Kathmandu over a 23-year period. METHODS We conducted a retrospective analysis of standardised microbiological data from April 1992 to December 2014 at a single healthcare facility in Kathmandu, examining time trends of Salmonella-associated bacteraemia and the corresponding antimicrobial susceptibility profiles of the isolated organisms. RESULTS Over 23 years there were 30,353 positive blood cultures. Salmonella enterica accounted for 65.4% (19,857/30,353) of all the bacteria positive blood cultures. S. Typhi and S. Paratyphi A were the dominant serovars, constituting 68.5% (13,592/19,857) and 30.5% (6,057/19,857) of all isolated Salmonellae. We observed (i) a peak in the number of Salmonella-positive cultures in 2002, a year of heavy rainfall and flooding in the Kathmandu Valley, followed by a decline toward pre-flood baseline by 2014, (ii) an increase in the proportion of S. Paratyphi in all Salmonella-positive cultures between 1992 and 2014, (iii) a decrease in the prevalence of MDR for both S. Typhi and S. Paratyphi, and (iv) a recent increase in fluoroquinolone non-susceptibility in both S. Typhi and S. Paratyphi isolates. CONCLUSIONS Our work describes significant changes in the epidemiology of Salmonella enterica in the Kathmandu Valley during the last quarter of a century. We highlight the need to examine current treatment protocols for enteric fever and suggest a change from fluoroquinolone monotherapy to combination therapies of macrolides or cephalosporins along with older first-line antimicrobials that have regained their efficacy.
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Affiliation(s)
- Raphaël M. Zellweger
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Buddha Basnyat
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
- Centre for Tropical Medicine and Global Health, Oxford University, Oxford, United Kingdom
- Global Antibiotic Resistance Partnership, Centre for Disease Dynamics Economics and Policy, Washington DC, Unites States of America
| | - Poojan Shrestha
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
| | | | - Sabina Dongol
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
| | - Paban K. Sharma
- Patan Academy of Health Sciences, Patan Hospital, Kathmandu, Nepal
| | - Samir Koirala
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
| | - Thomas C. Darton
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
| | - Christiane Dolecek
- Centre for Tropical Medicine and Global Health, Oxford University, Oxford, United Kingdom
| | - Corinne N. Thompson
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Guy E. Thwaites
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine and Global Health, Oxford University, Oxford, United Kingdom
| | - Stephen G. Baker
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine and Global Health, Oxford University, Oxford, United Kingdom
- The Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Abhilasha Karkey
- Oxford University Clinical Research Unit, Patan Academy of Health Sciences, Kathmandu, Nepal
- Centre for Tropical Medicine and Global Health, Oxford University, Oxford, United Kingdom
- Global Antibiotic Resistance Partnership, Centre for Disease Dynamics Economics and Policy, Washington DC, Unites States of America
- * E-mail:
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Chang SJ, Song J, Galán JE. Receptor-Mediated Sorting of Typhoid Toxin during Its Export from Salmonella Typhi-Infected Cells. Cell Host Microbe 2017; 20:682-689. [PMID: 27832592 DOI: 10.1016/j.chom.2016.10.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Revised: 09/16/2016] [Accepted: 10/09/2016] [Indexed: 11/30/2022]
Abstract
Typhoid toxin is an essential virulence factor of Salmonella Typhi, the cause of typhoid fever. Typhoid toxin is secreted into the lumen of Salmonella-containing vacuole (SCV), after which it is packaged into vesicle carrier intermediates and released extracellularly through incompletely understood mechanisms. Following export, the toxin targets cells by interacting with human-specific Neu5Ac-terminated glycan receptors. We show that typhoid toxin is sorted from the SCV into vesicle carrier intermediates via interactions of its B subunit, PltB, with specific lumenal sialylated glycan packaging receptors. Cells deficient in N-glycosylation or the synthesis of specific gangliosides or displaying Neu5Gc-terminated, as opposed to Neu5Ac-terminated, glycans do not support typhoid toxin export. Additionally, typhoid toxin packaging requires the specific SCV environment, as toxin produced by an S. Typhi mutant with impaired trafficking is not properly sorted into vesicles. These results reveal how the exotoxin of an intracellular pathogen engages host pathways for packaging and release.
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Affiliation(s)
- Shu-Jung Chang
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Jeongmin Song
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA
| | - Jorge E Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06536, USA.
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Abstract
Salmonella enterica subspecies enterica includes several serovars infecting both humans and other animals and leading to typhoid fever or gastroenteritis. The high prevalence of associated morbidity and mortality, together with an increased emergence of multidrug-resistant strains, is a current global health issue that has prompted the development of vaccination strategies that confer protection against most serovars. Currently available systemic vaccine approaches have major limitations, including a reduced effectiveness in young children and a lack of cross-protection among different strains. Having studied host-pathogen interactions, microbiologists and immunologists argue in favor of topical gastrointestinal administration for improvement in vaccine efficacy. Here, recent advances in this field are summarized, including mechanisms of bacterial uptake at the intestinal epithelium, the assessment of protective host immunity, and improved animal models that closely mimic infection in humans. The pros and cons of existing vaccines are presented, along with recent progress made with novel formulations. Finally, new candidate antigens and their relevance in the refined design of anti-Salmonella vaccines are discussed, along with antigen vectorization strategies such as nanoparticles or secretory immunoglobulins, with a focus on potentiating mucosal vaccine efficacy.
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Typhoid toxin provides a window into typhoid fever and the biology of Salmonella Typhi. Proc Natl Acad Sci U S A 2016; 113:6338-44. [PMID: 27222578 DOI: 10.1073/pnas.1606335113] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Salmonella Typhi is the cause of typhoid fever, a disease that has challenged humans throughout history and continues to be a major public health concern. Unlike infections with most other Salmonellae, which result in self-limiting gastroenteritis, typhoid fever is a life-threatening systemic disease. Furthermore, in contrast to most Salmonellae, which can infect a broad range of hosts, S. Typhi is a strict human pathogen. The unique features of S. Typhi pathogenesis and its stringent host specificity have been a long-standing puzzle. The discovery of typhoid toxin not only has provided major insight into these questions but also has offered unique opportunities to develop novel therapeutic and prevention strategies to combat typhoid fever.
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Zhu C, Xiong K, Chen Z, Hu X, Li J, Wang Y, Rao X, Cong Y. Construction of an attenuated Salmonella enterica serovar Paratyphi A vaccine strain harboring defined mutations in htrA and yncD. Microbiol Immunol 2016; 59:443-51. [PMID: 26084199 DOI: 10.1111/1348-0421.12276] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 06/09/2015] [Accepted: 06/12/2015] [Indexed: 11/27/2022]
Abstract
The global epidemic features of enteric fever have changed greatly in recent years. The incidence of enteric fever caused by Salmonella enterica serovar Paratyphi A has progressively increased. In some areas of Asia, infections with S. Paratyphi A have exceeded those with S. Typhi, resulting in S. Paratyphi A becoming the main causative agent of enteric fever. However, two currently licensed typhoid vaccines do not confer adequate cross-protection against S. Paratyphi A infection. Therefore, development of specific vaccines against enteric fever caused by S. Paratyphi A is urgently needed. In the present study, an attenuated strain was constructed by double deletion of the htrA and yncD genes in a wild-type strain of S. Paratyphi A and its safety and immunogenicity assessed. In a mouse model, the 50% lethal dose of the double deletion mutant and the wild-type strain were 3.0 × 10(8) CFU and 1.9 × 10(3) CFU, respectively, suggesting that the double deletion resulted in remarkably decreased bacterial virulence. Bacterial colonization of the double deletion mutant in the livers and spleens of infected mice was strikingly less than that of the wild-type strain. A single nasal administration of the attenuated vaccine candidate elicited high concentrations of anti-LPS and anti-flagellin IgG in a mouse model and protected immunized mice against lethal challenge with the wild-type strain. Thus, our findings suggest that the attenuated vaccine strain is a promising candidate worthy of further evaluation both as a human enteric fever vaccine and as a vaccine delivery vector for heterologous antigens.
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Affiliation(s)
- Chunyue Zhu
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Kun Xiong
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Zhijin Chen
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Xiaomei Hu
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Jianhua Li
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Yiran Wang
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Xiancai Rao
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
| | - Yanguang Cong
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, China
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12
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Xiong K, Chen Z, Zhu C, Li J, Hu X, Rao X, Cong Y. Safety and immunogenicity of an attenuated Salmonella enterica serovar Paratyphi A vaccine candidate. Int J Med Microbiol 2015; 305:563-71. [PMID: 26239100 DOI: 10.1016/j.ijmm.2015.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 07/02/2015] [Accepted: 07/22/2015] [Indexed: 02/08/2023] Open
Abstract
Enteric fever caused by Salmonella enterica serovar Paratyphi A has progressively increased in recent years and became a global health issue. Currently licensed typhoid vaccines do not confer adequate cross-immunoprotection against S. Paratyphi A infection. Therefore, vaccines specifically against enteric fever caused by S. Paratyphi A are urgently needed. In the present study, an attenuated vaccine strain was constructed from S. Paratyphi A CMCC50093 by the deletions of aroC and yncD. The obtained strain SPADD01 showed reduced survival within THP-1 cells and less bacterial burden in spleens and livers of infected mice compared with the wild-type strain. The 50% lethal doses of SPADD01 and the wild-type strain were assessed using a murine infection model. The virulence of SPADD01 is approximately 40,000-fold less than that of the wild-type strain. In addition, SPADD01 showed an excellent immunogenicity in mouse model. Single intranasal inoculation elicited striking humoral and mucosal immune responses in mice and yielded effective protection against lethal challenge of the wild-type strain. A high level of cross-reactive humoral immune response against LPS of Salmonella enterica serovar Typhi was also detected in immunized mice. However, SPADD01 vaccination only conferred a low level of cross-protection against S. Typhi. Our data suggest that SPADD01 is a promising vaccine candidate against S. Paratyphi A infection and deserves further evaluation in clinical trial. To date, no study has demonstrated a good cross-protection between serovars of S. Typhi and S. Paratyphi A, suggesting that the dominant protective antigens of both serovars are likely different and need to be defined in future study.
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Affiliation(s)
- Kun Xiong
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
| | - Zhijin Chen
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
| | - Chunyue Zhu
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
| | - Jianhua Li
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
| | - Xiaomei Hu
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
| | - Xiancai Rao
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
| | - Yanguang Cong
- Department of Microbiology, Third Military Medical University, Chongqing, 400038, PR China.
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