Serotype-specific opsonization of Treponema hyodysenteriae.

Treponema hyodysenteriae was shown to attach to mouse peritoneal cells in the absence of serum opsonins in vitro. If serotype-specific antiserum from pigs was added to the media and treponemes of that corresponding serotype were employed in the assay, the amount of attachment increased an average of 3.7 times that of the control without pig sera. However, the amount of attachment was increased an average of only 1.5 times that of the control if organisms of any noncorresponding serotype of T. hyodysenteriae were used in the assay. Since the lipopolysaccharide (LPS) extracted from T. hyodysenteriae is the basis for serotyping the treponeme, the ability of these distinct LPS types to block attachment by blocking opsonization of the organisms was tested. Attachment, using corresponding antisera and treponemes, was blocked by LPS extracted from treponemes of that serotype, but not by LPS extracted from treponemes of other serotypes. These results indicate that antibody response to T. hyodysenteriae infection in pigs is serotype-specific. Furthermore, since opsonization and subsequent attachment of bacteria to phagocytes is known to be a protective mechanism, we suggest that the LPS may be an important antigen in the stimulation of host defense against the treponeme.