Immunological Characterization of Differentially Extracted Whole Cell Bacterial Protein derived from Salmonella Typhi and invasive Non Typhoidal Salmonella

Abstract The diagnosis of typhoid fever and invasive non-typhoidal Salmonella (iNTS) is complicated due to their non-specific symptoms that overlap with other febrile illnesses. Conventional diagnostic methods such as culture isolation are time-consuming and expensive, while serological tests have lower sensitivity and produce false positives. Protein depletion has been shown to enhance low abundant proteins. Therefore, our study aims to expand upon this approach by analyzing differentially extracted protein fractions to improve the accuracy and sensitivity of diagnostic methods. In this study, the immunological properties of differentially extracted protein fractions derived from S.Typhi and S.spp were analyzed using dot Enzyme Immunoassay (dot EIA) with pooled sera from typhoid patients, healthy subjects, vaccinated subjects, subjects with other diseases, and invasive non-typhoidal patients. The results showed dynamic profiles of humoral immune response against the arrays of protein fractions, revealing their antigenic properties. The comparative analysis of the differentially extracted protein fractions demonstrated that the use of sdWCP along with WCP and CSP was the most suitable for the serodiagnosis of typhoid fever. The experiment also confirmed the separation of protein upon fractionation and the presence of O and dH antigens in different protein fractions. The findings of this study can be useful in developing a vaccine and improving the accuracy of serodiagnosis for typhoid fever and iNTS infections.