Identification of the innate human immune response to surface-exposed proteins of coagulase-negative staphylococci

The presumed host defense against coagulase-negative staphylococci (ConS), recognized pathogens in hosts with compromised immunity or indwelling medical devices, is opsonophagocytosis. Targets for opsonization remain unclear. Using radiolabeling techniques, we identified the surface-exposed proteins of ConS and determined the innate humoral immune responses to them among healthy adults. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of surface proteins extrinsically labeled with 125I demonstrated 20 to 30 proteins with molecular weights of 15,000 to greater than 130,000. Five to ten of these proteins were immunogenic and recognized by normal human sera, including predominant 18-, 41-, 48-, and 51-kDa proteins. We also evaluated the humoral response of cancer patients with ConS bacteremia. Patients' sera obtained before bacteremic episodes demonstrated a pattern of reactivity similar to that of normal human sera. When patients' sera obtained after bacteremic episodes were used to determine whether an expanded immune response followed infection, only one of seven showed reactivity with more proteins than seen with the innate response. Western blot (immunoblot) analysis and whole-cell enzyme-linked immunosorbent assays were also evaluated. This study identifies (i) the surface-exposed proteins available for host interaction, (ii) the innate human antibody response to these proteins, and (iii) the immune response of cancer patients with ConS bacteremia.