Heat shock proteins of S. typhi and their reactivity with sera from patients with Typhoid fever

Abstract

We studied the heat shock protein (HSP) response of Salmonella typhi following exposure to elevated growth temperatures. Three major proteins with molecular sizes of58, 68 and 88 kDa were abundantly expressed when S. typhi cells were shifted from 37°C to 45°C and 55°C. These proteins were also consitutively expressed at 37°C. Western blotting and immunoprecipitation studies with anti-HSP monoclonal antibodies, revealed that the 58 and 68 kDa proteins were analogous to the GroEL and DnaK proteins of E. coli. These HSPs are also abundantly present in the outer membrane fraction of disrupted cells and, to a lesser extent, in the cytosol. Fmmunoblotting experiments with sera from patients with a culture-positive diagnosis of typhoid fever showed the presence of antibodies to these HSPs. Nine out of twelve sera reacted with the 58, 68 and 88 kDa proteins, while three sera only with the 68 and 88 kDa proteins. All ten sera from normal, healthy individuals showed no binding to these HSPs. Three to four immunodominant regions within the S. typhi GroEL gene was also identified using peptide synthesis on polyethylene pins. In light of the well-documented roles ofHPSs in the pathogenesis of microbial infections and as immunodominant antigens, these findings may be relevant for a better understanding of disease processes and future development of diagnostic and preventive strategies.