Campylobacter jejuni 81-176 grown in vivo in rabbit ileal loops expresses novel
proteins that are not expressed under standard laboratory culture conditions. A new
protein with a molecular mass of ca. 180 kDa is expressed at 14, 24, and 48 h of
infection. Three other
proteins, with molecular masses of ca. 66, 43, and 35 kDa, are overexpressed during different phases of
infection. Expression of these
proteins stops immediately during the first passage in laboratory media, and they do not elicit a human immune response. Two other
proteins, with molecular masses of ca. 84 and 47 kDa, expressed 48 h after
infection can be identified by using convalescent sera from human volunteers who were immune to C. jejuni
infection upon rechallenge; these
proteins were not visualized on
sodium dodecyl sulfate-
polyacrylamide gel electrophoresis
gels by
Coomassie blue staining or
silver staining.
Antibodies to the 84- and 47-kDa
proteins are of the
immunoglobulin G class. Both preinfection and convalescent human sera react strongly to the C. jejuni
flagellin (a 58-kDa
protein), suggesting the presence of cross-reactive
antibodies to this
protein in healthy humans. Major outer
membrane protein and flagella may play a role in providing protection against C. jejuni disease, but our data suggest that there are other
proteins expressed only during in vivo growth of the organism that elicit a strong immune response in human C. jejuni
infections.