Serum antibody response in patients with mild Typhoid fever from southern Vietnam

The aim of this study was to describe the antibody response to Salmonella typhi (S. typhij antigens (lipolysaccharide (LPS), flagella, Vi) m patients with non-severe typhoid fever from an endemic region. Acute serum samples were obtained from 164 patients with blood culture proven typhoid fever. Serum levels of anti-LPS (total Immunoglobulin (Ig), IgA, IgG, IgM), anti-flagella (total Ig, IgG) and anti-Vi (total Ig, IgG) antibodies were determined. Inter-individual variation was high for all antibody-antigen combinations investigated. Correlation analyses showed this was due, in part, to differences in age and duration of fever. Some patients had relatively low antibody levels despite a long history of illness, particularly children. Our results suggest that serological diagnostic tests based on the antigens used in this study may have limited sensitivity, particularly in young children, in patient with a short history of illness, and in those living in endemic areas.