Immune profiling with a Salmonella Typhi antigen microarray identifies new diagnostic biomarkers of human typhoid

Current serological diagnostic assays for typhoid fever are based on detecting antibodies against Salmonella LPS or flagellum, resulting in a high false-positive rate. Here we used a protein microarray containing 2,724 Salmonella enterica serovar Typhi antigens (>63% of proteome) and identified antibodies against 16 IgG antigens and 77 IgM antigens that were differentially reactive among acute typhoid patients and healthy controls. The IgG target antigens produced a sensitivity of 97% and specificity of 80%, whereas the IgM target antigens produced 97% and 91% sensitivity and specificity, respectively. Our analyses indicated certain features such as membrane association, secretion and protein expression were significant enriching features of the reactive antigens. About 72% of the serodiagnostic antigens were within the top 25% of the ranked antigen list using a Naïve bayes classifier. These data provide an important resource for improved diagnostics, therapeutics and vaccine development against an important human pathogen.