Immunoproteomic Analysis of Antibody in Lymphocyte Supernatant in Patients with Typhoid Fever in Bangladesh

Abstract

iWe have previously shown that an assay based on detection of anti-Salmonella enterica serotype Typhi antibodies in supernatant of lymphocytes harvested from patients presenting with typhoid fever (antibody in lymphocyte supernatant [ALS] assay) can identify 100% of patients with blood culture-confirmed typhoid fever in Bangladesh. In order to define immunodominant proteins within the S. Typhi membrane preparation used as antigen in these prior studies and to identify potential biomarkers unique to S. Typhi bacteremic patients, we probed microarrays containing 2,724 S. Typhi proteins with ALS collected at the time of clinical presentation from 10 Bangladeshis with acute typhoid fever. We identified 62 immunoreactive antigens when evaluating both the IgG and IgA responses. Immune responses to 10 of these antigens discriminated between individuals with acute typhoid infection and healthy control individuals from areas where typhoid infection is endemic, as well as Bangladeshi patients presenting with fever who were subsequently confirmed to have a nontyphoid illness. Using an ALS enzyme-linked immunosorbent assay (ELISA) format and purified antigen, we then confirmed that immune responses against the antigen with the highest immunoreactivity (hemolysin E [HlyE]) correctly identified individuals with acute typhoid or paratyphoid fever in Dhaka, Bangladesh. These observations suggest that purified antigens could be used with ALS and corresponding acute-phase activated B lymphocytes in diagnostic platforms to identify acutely infected patients, even in areas where enteric fever is endemic.

Serodiagnosis of Acute Typhoid Fever in Nigerian Pediatric Cases by Detection of Serum IgA and IgG Against Hemolysin E and Lipopolysaccharide

“…In previous studies, we described the production and use of a S. Typhi partial proteome microarray (∼63%) for profiling antibodies in human adult typhoid cases from Malawi, 9 Vietnam, 10 and Bangladesh, 18 and in the mouse S. Typhimurium model.…”

“…10 In Bangladesh also, the same array revealed t1477 as the immunodominant antigen, able to discriminate between acute typhoid cases and uninfected controls in both serum and in plasmablast culture supernatants. 18 The t1477 antigen was not revealed as dominant in Malawian children, 9 although only two cases of typhoid were examined.…”

Plasma Immunoglobulin A Responses Against 2SalmonellaTyphi Antigens Identify Patients With Typhoid Fever

“…Our data set also does not directly address the discriminatory value of serologic analysis during acute paratyphoid fever. Paratyphoid fever caused by S. Paratyphi A now accounts for up to 1 in 5 cases of enteric fever in areas of Asia; however, the previous small analysis by Charles et al [13] of HlyE responses in patients with paratyphoid fever suggests excellent performance. Our analysis also used samples collected in highly typhoid endemic areas, and findings might be different in nonendemic areas, although the discriminatory value that we found even in young immunologically naive children is reassuring and suggests that assays based on anti-HlyE IgA detection would be promising even in nonendemic areas.…”

“…These antigens include hemolysin E (HlyE), cytolethal distending toxin B (CdtB), S. Typhi membrane preparation (MP), and S. Typhi lipopolysaccharide (LPS) [13][14][15]. HlyE and CdtB are present in S. Typhi and Salmonella Paratyphi A but are rarely found in other Salmonella serovars [16].…”

Multi‐isotype antibody responses against the multimeric Salmonella Typhi recombinant hemolysin E antigen

“…The significant titers of IgA, which are comparable to the IgG isotype recorded for the typhoid patients, are interesting because the rapid antibody tests currently on the market rely on detection of IgG and IgM only (11). In a recent study using antibody-in-lymphocyte supernatant, the authors also found that HlyE had the highest IgG and IgA immunoreactivity in their immunoproteomic screen of 2724 S. Typhi proteins (12). This is important because IgA detection in IgA rich fluids could offer an alternative route for diagnosis.…”