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  1. Mimotopes of heat shock proteins of Salmonella enterica serovar Typhi identified from phage-displayed peptide library
    Yuen HL, Shamala D, Thong KL
    J Infect Dev Ctries, 2008 Aug 30;2(4):313-23.
    PMID: 19741295
    BACKGROUND: Heat shock proteins (HSPs) are known to be involved in the pathogenesis of Salmonella enterica serovar Typhi (S. Typhi), the causative agent of typhoid fever. The objective of this study was to apply a phage display library to identify mimotopes of two HSPs, HSP90 and DnaK in S. Typhi.

    METHODOLOGY: A 12-mer random peptide library expressed on the surface of the filamentous phage, M13, was used to select the mimotopes of two S. Typhi heat shock proteins by biopanning with monoclonal antibodies (mAbs), DnaK and HSP90. The immunogenicity of the selected peptides was determined through binding affinity with polyclonal antibodies from pooled typhoid-confirmed patients' sera and purified HSPs mAb using Western blotting and ELISA.

    RESULTS: Five rounds of biopanning resulted in enrichment of phage clones expressing the binding motifs TDxSTRP and FPSHYWLYPPPT, respectively. The selected peptides showed strong immunoreactivity with patients' sera. Thus, monoclonal antibodies against HSP and patient sera can select common mimotopes from the random peptide library.

    CONCLUSION: These findings may provide fundamental information for further studies on diagnostic application or vaccine design against this aetiologic agent of typhoid fever.

    Matched MeSH terms: Salmonella typhi/immunology*
  2. Mimotopes of the Vi antigen of Salmonella enterica serovar typhi identified from phage display peptide library
    Tang SS, Tan WS, Devi S, Wang LF, Pang T, Thong KL
    Clin Diagn Lab Immunol, 2003 Nov;10(6):1078-84.
    PMID: 14607870
    The capsular polysaccharide Vi antigen (ViCPS) is an essential virulence factor and also a protective antigen of Salmonella enterica serovar Typhi. A random 12-mer phage-displayed peptide library was used to identify mimotopes (epitope analogues) of this antigen by panning against a ViCPS-specific monoclonal antibody (MAb) ATVi. Approximately 75% of the phage clones selected in the fourth round carried the peptide sequence TSHHDSHGLHRV, and the rest of the clones harbored ENHSPVNIAHKL and other related sequences. These two sequences were also obtained in a similar panning process by using pooled sera from patients with a confirmed diagnosis of typhoid fever, suggesting they mimic immunodominant epitopes of ViCPS antigens. Binding of MAb ATVi to the mimotopes was specifically blocked by ViCPS, indicating that they interact with the same binding site (paratope) of the MAb. Data and reagents generated in this study have important implications for the development of peptide-base diagnostic tests and peptide vaccines and may also provide a better understanding of the pathogenesis of typhoid fever.
    Matched MeSH terms: Salmonella typhi/immunology*
  3. Report from an international symposium on typhoid fever
    Pang T, Calva E, Punjabi N, Rowley D
    Asian Pac J Allergy Immunol, 1992 Jun;10(1):73-7.
    PMID: 1358084
    Matched MeSH terms: Salmonella typhi/immunology
  4. A simple adherence test for detection of IgM antibodies in typhoid
    Ong LY, Pang T, Lim SH, Tan EL, Puthucheary SD
    J Med Microbiol, 1989 Jul;29(3):195-8.
    PMID: 2473209
    A simple adherence test to detect IgM antibodies in patients with typhoid is described. The test utilises the IgM-"capture" approach, in which the test serum is applied to microtitration plate wells previously coated with anti-human IgM, followed by application of a stained Salmonella typhi antigen suspension which shows adherence in positive cases. By this test, 58 (95%) of 61 sera from confirmed cases of typhoid possessed IgM antibodies to the H or O or both antigens of S. typhi. In patients for whom a diagnosis of typhoid was based only on a significant Widal-test titre, 31 (41%) of 76 sera had IgM antibodies to the H or O or both antigens of S. typhi. Some cross-reactivity of the IgM antibodies was detected, especially with the O antigens of S. paratyphi A and B. A total of 82 sera from non-typhoidal fevers (leptospirosis, typhus, dengue fever) showed no reactivity in this test. In normal sera there was no detectable IgM to the O antigen of S. typhi and only a small number (3.9%) had low levels of IgM to the H antigen. The significance and potential importance of this simple, sensitive, specific and economical test is discussed.
    Matched MeSH terms: Salmonella typhi/immunology*
  5. Significance and value of the Widal test in the diagnosis of typhoid fever in an endemic area
    Pang T, Puthucheary SD
    J Clin Pathol, 1983 Apr;36(4):471-5.
    PMID: 6833514
    The diagnostic value of the Widal test was assessed in an endemic area. The test was done on 300 normal individuals, 297 non-typhoidal fevers and 275 bacteriologically proven cases of typhoid. Of 300 normal individuals, 2% had an H agglutinin titre of 1/160 and 5% had an O agglutinin titre of 1/160. On the basis of these criteria a significant H and/or O agglutinin titre of 1/320 or more was observed in 93-97% of typhoid cases and in only 3% of patients with non-typhoidal fever. Of the sera from typhoid cases which gave a significant Widal reaction, the majority (79.9%) showed increases in both H and O agglutinins and 51 of 234 (21.8%) of these sera were collected in the first week of illness. The significance and implications of these findings are discussed.
    Matched MeSH terms: Salmonella typhi/immunology
  6. Heat-killed Salmonella typhi induces the release of prostaglandins and leukotrienes from mouse macrophages
    Pang T, Devi S, Puthucheary S, Pawlowski N
    Microbiol. Immunol., 1991;35(3):267-71.
    PMID: 1870442
    Mouse macrophages pre-labeled with [3H]arachidonic acid (20:4) were shown to release metabolites generated by the lipoxygenase and cyclo-oxygenase pathways following in vitro addition of heat-killed Salmonella typhi. These metabolites were maximally released after 60-90 min of incubation and consisted of prostaglandins (85%), leukotriene C (6%), di-HETEs, leukotrienes D and E (4%), mono-HETEs (2%) and other metabolites (3%). Of the metabolites generated by the cyclo-oxygenase pathway (prostaglandins), 6-keto PGF1 alpha and PGE2 were generated at a ratio of 1.2 to 1. The significance and importance of these results are discussed.
    Matched MeSH terms: Salmonella typhi/immunology*
  7. Detection of antibodies against Salmonella typhi outer membrane protein (OMP) preparation in typhoid fever patients
    Verdugo-Rodriguez A, Gam LH, Devi S, Koh CL, Puthucheary SD, Calva E, et al.
    Asian Pac J Allergy Immunol, 1993 Jun;11(1):45-52.
    PMID: 8216558
    An indirect ELISA was used to detect antibodies against outer membrane protein preparations (OMPs) from Salmonella typhi. Sera from patients with a definitive diagnosis of typhoid fever (TF) gave a mean absorbance reading, at 414 nm, of 1.52 +/- 0.23 as compared to 0.30 +/- 0.11 for sera from healthy individuals. This gave a positive to negative ratio of absorbance readings of approximately 5.1. Suspected TF patients (no isolation of S. typhi), with positive and negative Widal titers had mean absorbance readings of 1.282 +/00.46 and 0.25 +/- 0.19, respectively. Sera from patients with leptospirosis, rickettsial typhus, dengue fever, and other infections gave mean absorbances of 0.20 +/- 0.08, 0.24 +/- 0.08, 0.27 +/- 0.08, and 0.31 +/- 0.16, respectively. The sensitivity, specificity, positive and negative predictive values were 100%, 94%, 80% and 100%, respectively. The antibody response detected in the definitive TF cases was predominantly IgG in nature and no cross-reactivity was seen with OMP preparations extracted from E. coli. Variable reactivity was noted with OMP preparations obtained from other Salmonella spp. Three major OMPs are presented in the antigen preparation and strong binding of positive sera was detected to all three bands.
    Matched MeSH terms: Salmonella typhi/immunology*
  8. Immunogenic epitopes of Salmonella typhi GroEL heat shock protein reactive with both monoclonal antibody and patients sera
    Panchanathan V, Naidu BR, Devi S, Di Pasquale A, Mason T, Pang T
    Immunol Lett, 1998 Jun;62(2):105-9.
    PMID: 9698106
    A series of 122, 9-mer overlapping peptides based on the sequence of the Salmonella typhi GroEL gene was synthesized on the surfaces of polyethylene pins and screened with monoclonal antibody to GroEL and with human sera from patients with typhoid fever and normal healthy blood donors. Three immunogenic epitopes corresponding to peptides EGQDRGYSY, YSYNKETGE and GKGTEEKEK were identified upon screening with the human sera. In addition, screening of the peptides with a monoclonal antibody to GroEL detected binding to a third peptide, KGGKGTEEK, which contains a common overlapping sequence to peptide GKGTEEKEK. Identification and definition of these epitopes will be important in delineating the biological and immunological functions of this protein and in designing better diagnostic tests and vaccines.
    Matched MeSH terms: Salmonella typhi/immunology*
  9. Longevity of antibody responses to a Salmonella typhi-specific outer membrane protein: interpretation of a dot enzyme immunosorbent assay in an area of high typhoid fever endemicity
    Choo KE, Davis TM, Ismail A, Ong KH
    Am J Trop Med Hyg, 1997 Dec;57(6):656-9.
    PMID: 9430522
    The objective of this study was to investigate the longevity of positive dot enzyme immunosorbent assay (dot EIA) results for IgM and IgG to a Salmonella typhi outer membrane protein in Malaysian children with enteric fever. The patients were children one month to 12 years of age with clinical evidence of typhoid fever, positive blood or stool cultures for S. typhi, and/or a positive Widal test result who were admitted over a two-year period to General Hospital (Kota Bharu, Malaysia). These patients received standard inpatient treatment for enteric fever including chloramphenicol therapy for 14 days. Dot EIA tests were performed as part of clinical and laboratory assessments on admission, at two weeks, and then at 3, 6, 9, 12, 15, 18, and 21 months postdischarge. Assessment of the longevity of positive dot EIA IgM and IgG titers was done by Kaplan-Meier analysis. In 94 evaluable patients, 28% were dot EIA IgM positive but IgG negative on admission, 50% were both IgM and IgG positive, and 22% were IgM negative and IgG positive. Mean persistence of IgM dot EIA positivity was 2.6 months (95% confidence interval = 2.0-3.1 months) and that of IgG was 5.4 months (4.5-6.3 months). There were no significant differences between the three subgroups. Thus, positive IgM and IgG results determined by dot EIA within four and seven months, respectively, following documented or suspected enteric fever in a child from an endemic area should be interpreted with caution. In other clinical situations, the dot EIA remains a rapid and reliable aid to diagnosis.
    Matched MeSH terms: Salmonella typhi/immunology*
  10. Rapid serodiagnosis of typhoid fever by dot enzyme immunoassay in an endemic area
    Choo KE, Oppenheimer SJ, Ismail AB, Ong KH
    Clin Infect Dis, 1994 Jul;19(1):172-6.
    PMID: 7948526
    A dot enzyme immunoassay (EIA) using 50-kD outer-membrane proteins (OMPs) of Salmonella typhi was compared with the Widal test for the serodiagnosis of typhoid fever in 109 febrile children admitted to a hospital in an endemic area. In the culture-positive typhoid group, the initial dot EIA was positive in 40 of 42 cases and the initial Widal test was positive in 41. In the culture-negative clinical typhoid group, both the dot EIA and the Widal test were positive in 17 of 18 cases. In the nontyphoidal fever group, the dot EIA was negative in all of 49 cases and the Widal test was negative in 44. With culture used as the gold standard, the dot EIA is as sensitive as the Widal test (95% vs. 98%), has a similar high negative predictive value (96% vs. 98%), and is more specific (75% vs. 67%). In addition, the dot EIA offers the advantages of simplicity, speed, early diagnosis, economy, and flexibility (i.e., other diagnostic tests can be conducted simultaneously).
    Matched MeSH terms: Salmonella typhi/immunology*
  11. Evaluation of Salmonella Typhi antigen YncE alongside HlyE for the detection of typhoid fever and its carriers
    Franklin F, Chong CW, Chua LH, Anthony AA, Liew MWO, Aziah I, et al.
    Med Microbiol Immunol, 2020 Oct;209(5):593-601.
    PMID: 32246197 DOI: 10.1007/s00430-020-00667-1
    Typhoid fever is a disease caused by Salmonella Typhi that was implicated in millions of illnesses worldwide annually. Individuals that do not recover fully from typhoid fever can become asymptomatic carriers of the disease. Host antibodies against the S. Typhi antigens, HlyE (for acute typhoid) and YncE (for carriers) were previously reported to be useful biomarkers for the disease. Here, we expressed and purified recombinant HlyE and YncE antigens and tested the IgG, IgA and IgM responses in 422 sera samples retrieved from acute typhoid patients, other febrile, food handlers, and healthy individuals. The results showed that HlyE-IgG, -IgA and -IgM ELISAs have a collective sensitivity of 83% while YncE-IgG and -IgA ELISAs identified 16 possible carriers based on their antibody profiles. The identification of sensitive biomarkers for typhoid carrier detection is crucial for disease eradication.
    Matched MeSH terms: Salmonella typhi/immunology*
  12. Fulltext Retrospective review of dot enzyme immunoassay test for typhoid fever in an endemic area
    Jackson AA, Ismail A, Ibrahim TA, Kader ZS, Nawi NM
    Southeast Asian J. Trop. Med. Public Health, 1995 Dec;26(4):625-30.
    PMID: 9139364
    Typhoid fever remains a common problem in Malaysia, but for its diagnosis both blood culture and the Widal test have drawbacks. A dot enzyme immunoassay (EIA) has been developed which detects IgM and IgG antibodies to a specific 50 kDa outer membrane protein on Salmonella typhi. This study was performed among outpatients attending the university hospital in Kelantan, a state on the east coast of Peninsular Malaysia where typhoid is endemic. The dot EIA was done on 149 outpatients of all ages in whom typhoid was suspected. Of these, 60 were not analysable due to insufficient data. The other 89 were retrospectively classed as typhoid (total = 21), or not typhoid (total = 68). The criteria for diagnosis of typhoid was either, blood culture was positive, or with blood culture negative, temperature was at least 38 degrees C and Widal O and/or H titer greater than or equal to 1/160. We then compared the diagnosis with the EIA result. For the result where either IgM or IgG was positive, sensitivity was 90%, specificity 91% and negative predictive value 97%. For IgM positive, specificity was 100%. But the specificity of IgG positive alone was reduced by six false positives, which were probably due to persistence of IgG after acute infection. Other cases were found where IgG positive alone appeared in the first week of typhoid fever, probably due to rapid response in a second or subsequent infection. We also found that IgM-producing patients were significantly younger than those showing IgG alone positive.
    Study site: Community Medicine clinic, Accident & emergency department, Hospital Universiti Sains Malaysia (HUSM), Kelantan, Malaysia
    Matched MeSH terms: Salmonella typhi/immunology*
  13. Rapid serologic diagnosis of pediatric typhoid fever in an endemic area: a prospective comparative evaluation of two dot-enzyme immunoassays and the Widal test
    Bhutta ZA, Mansurali N
    Am J Trop Med Hyg, 1999 Oct;61(4):654-7.
    PMID: 10548305
    We evaluated the diagnostic sensitivity and specificity of two dot-enzyme-linked immunoassays (Typhidot and Typhidot-M; Malaysian Biodiagnostic Research SDN BHD, Kuala Lumpur, Malaysia), assessing IgG and IgM antibodies against the outer membrane protein (OMP) of Salmonella typhi, and the Widal test in comparison with blood culture in a consecutive group of children with suspected typhoid fever. Of 97 children with suspected typhoid fever, the disease was confirmed bacteriologically in 46 (47%), whereas 25 (26%) were considered to have typhoid fever on clinical grounds. An alternative diagnosis was made in 26 (27%). The Typhidot and Typhidot-M were superior to the Widal test in their diagnostic sensitivity and specificity, although values (sensitivity = 85-94% and specificity = 77-89%) were significantly lower than in other regional reports. The lower specificity of the Typhidot in our series may represent regional differences in the genomic structure and plasticity of the OMP of S. typhi and merits further evaluation of these tests in diverse geographic locations.
    Matched MeSH terms: Salmonella typhi/immunology
  14. Fulltext Multi-isotype antibody responses against the multimeric Salmonella Typhi recombinant hemolysin E antigen
    Ong EB, Ignatius J, Anthony AA, Aziah I, Ismail A, Lim TS
    Microbiol. Immunol., 2015 Jan;59(1):43-7.
    PMID: 25399538 DOI: 10.1111/1348-0421.12211
    The detection and measurement of different antibody isotypes in the serum provide valuable indicators of the different stages of typhoid infection. Here, the ability of S. Typhi recombinant hemolysin E (HlyE) to detect multi-isotype antibody responses in sera of patients with typhoid and paratyphoid A was investigated using an indirect antibody immunoassay. Nanogram amounts of HlyE were found to be sufficient for detection of IgG and IgA isotypes and, in a study of individuals' sera (n = 100), the immunoassay was able to distinguish between typhoid and non-typhoid sera. The overall sensitivity, specificity and efficiency of the ELISA were 70% (39/56), 100% (44/44) and 83% respectively.
    Matched MeSH terms: Salmonella typhi/immunology*
  15. Overexpression, purification and validation of antigenic Salmonella enterica serovar Typhi proteins identified from LC-MS/MS
    Chin CF, Teh BA, Anthony AA, Aziah I, Ismail A, Ong EB, et al.
    Appl Biochem Biotechnol, 2014 Nov;174(5):1897-906.
    PMID: 25149461 DOI: 10.1007/s12010-014-1173-y
    In our earlier study, an immunoblot analysis using sera from febrile patients revealed that a 50-kDa band from an outer membrane protein fraction of Salmonella enterica serovar Typhi was specifically recognized only by typhoid sera and not sera from other febrile illnesses. Here, we investigated the identities of the proteins contained in the immunogenic 50-kDa band to pinpoint antigens responsible for its immunogenicity. We first used LC-MS/MS for protein identification, then used the online tool ANTIGENpro for antigenicity prediction and produced recombinant proteins of the lead antigens for validation in an enzyme-linked immunosorbent assay (ELISA). We found that proteins TolC, GlpK and SucB were specific to typhoid sera but react to antibodies differently under native and denatured conditions. This difference suggests the presence of linear and conformational epitopes on these proteins.
    Matched MeSH terms: Salmonella typhi/immunology*
  16. Cloning, expression, and purification of the hemolysin/cytolysin (HlyE antigen) from Salmonella enterica serovar Typhi: potential application for immunoassay development
    Ong EB, Anthony AA, Ismail A, Ismail A, Lim TS
    Diagn Microbiol Infect Dis, 2013 Sep;77(1):87-9.
    PMID: 23790417 DOI: 10.1016/j.diagmicrobio.2013.05.010
    The hemolysin (HlyE) protein of Salmonella enterica serovar Typhi was reported to be antigenic. This work describes the cloning, expression, and purification of a hexahistidine-tagged HlyE protein under native conditions. Immunoblot analysis and a competitive enzyme-linked immunosorbent assay using sera from typhoid patients showed the presence of HlyE-specific antibodies in circulation.
    Matched MeSH terms: Salmonella typhi/immunology*
  17. Generation of a naïve human single chain variable fragment (scFv) library for the identification of monoclonal scFv against Salmonella Typhi Hemolysin E antigen
    Lim BN, Chin CF, Choong YS, Ismail A, Lim TS
    Toxicon, 2016 Jul;117:94-101.
    PMID: 27090555 DOI: 10.1016/j.toxicon.2016.04.032
    Antibody phage display is a useful tool for the isolation and identification of monoclonal antibodies. Naive antibody libraries are able to overcome the limitations associated with the traditional hybridoma method for monoclonal antibody generation. Antibody phage display is also a preferred method for antibody generation against toxins as it does not suffer from toxicity mediated complications. Here, we describe a naïve multi ethnic scFv antibody library generated via two-step cloning with an estimated diversity of 2 × 10(9). The antibody library was used to screen for monoclonal antibodies against Hemolysin E antigen, a pore forming toxin produced by Salmonella enterica serovar Typhi. A soluble monoclonal scFv antibody against the HlyE toxin (IgM scFv D7 anti-hlyE) was isolated from the library. This shows the value of the naïve library to generate antibodies against toxin targets in addition to the potential use of the library to isolate antibodies against other immunogenic targets.
    Matched MeSH terms: Salmonella typhi/immunology*
  18. Fulltext Delineation of B-cell Epitopes of Salmonella enterica serovar Typhi Hemolysin E: Potential antibody therapeutic target
    Chin CF, Lai JY, Choong YS, Anthony AA, Ismail A, Lim TS
    Sci Rep, 2017 05 19;7(1):2176.
    PMID: 28526816 DOI: 10.1038/s41598-017-01987-8
    Hemolysin E (HlyE) is an immunogenic novel pore-forming toxin involved in the pathogenesis of typhoid fever. Thus, mapping of B-cell epitopes of Salmonella enterica serovar Typhi (S. Typhi) is critical to identify key immunogenic regions of HlyE. A random 20-mer peptide library was used for biopanning with enriched anti-HlyE polyclonal antibodies from typhoid patient sera. Bioinformatic tools were used to refine, analyze and map the enriched peptide sequences against the protein to identify the epitopes. The analysis identified both linear and conformational epitopes on the HlyE protein. The predicted linear GAAAGIVAG and conformational epitope PYSQESVLSADSQNQK were further validated against the pooled sera. The identified epitopes were then used to isolate epitope specific monoclonal antibodies by antibody phage display. Monoclonal scFv antibodies were enriched for both linear and conformational epitopes. Molecular docking was performed to elucidate the antigen-antibody interaction of the monoclonal antibodies against the epitopes on the HlyE monomer and oligomer structure. An in-depth view of the mechanistic and positional characteristics of the antibodies and epitope for HlyE was successfully accomplished by a combination of phage display and bioinformatic analysis. The predicted function and structure of the antibodies highlights the possibility of utilizing the antibodies as neutralizing agents for typhoid fever.
    Matched MeSH terms: Salmonella typhi/immunology*
  19. Demonstration of an antigenic protein specific for Salmonella typhi
    Ismail A, Hai OK, Kader ZA
    Biochem Biophys Res Commun, 1991 Nov 27;181(1):301-5.
    PMID: 1958200
    Current studies were undertaken to determine the presence of a specific antigenic protein on the outer membrane of Salmonella typhi. Immunoblot analysis using sera from patients with fevers revealed that the 50 kD band was specifically recognized only by typhoid sera. The 50 kD band located on the outer membrane is protein by nature and is not a Vi (capsular), dH (flagellar), or O9 (somatic) antigen of S. typhi. These results indicate the usefulness of the specific antigen in the development of a serodiagnostic test for typhoid fever since antibodies of both the IgM and IgG class responses were obtained.
    Matched MeSH terms: Salmonella typhi/immunology*
  20. Fulltext Standardisation of the Widal test
    Cheong YM, Jegathesan M
    Med J Malaysia, 1989 Sep;44(3):267.
    PMID: 2483249
    Matched MeSH terms: Salmonella typhi/immunology
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