Tryptic Shaving of Staphylococcus aureus Unveils Immunodominant Epitopes on the Bacterial Cell Surface

The opportunistic pathogen Staphylococcus aureus has become a major threat for
human health and well-being by developing
resistance to antibiotics and by fast evolution into new lineages
that rapidly spread within the healthy human population. This calls
for development of active or passive immunization strategies to prevent
or treat acute phase infections. Since no such anti-staphylococcal
immunization approaches are available for clinical implementation,
the present studies were aimed at identifying new leads for their
development. For this purpose, we profiled the cell-surface-exposed
staphylococcal proteome under infection-mimicking conditions by combining
two approaches for “bacterial shaving” with immobilized
or soluble trypsin and subsequent mass spectrometry analysis of liberated
peptides. In parallel, non-covalently cell-wall-bound proteins extracted
with potassium thiocyanate and the exoproteome fraction were analyzed
by gel-free proteomics. All data are available through ProteomeXchange
accession PXD000156. To pinpoint immunodominant bacterial-surface-exposed
epitopes, we screened selected cell-wall-attached proteins of S. aureus for binding of immunoglobulin G from patients
who have been challenged by different types of S. aureus due to chronic wound colonization. The combined results of these
analyses highlight particular cell-surface-exposed S. aureus proteins with highly immunogenic exposed
epitopes as potential targets for development of protective anti-staphylococcal
immunization strategies.