Figure 1. Schematic diagram of the surface protein detection assay.

One sample of the S. suis-derived antiserum was pre-absorbed with whole-cell S. suis to remove the antibodies that recognize outer surface proteins (“pre-absorbed”). Then, untreated and “pre-absorbed” antisera were used to probe 2-DE gels of S. suis proteins. Spots that appear in the blot probed with untreated antiserum, but that were absent from the blot probed with “pre-absorbed” antiserum, were evaluated to identify the surface proteins.