ANTIBODY-RESPONSE AGAINST PSEUDOMONAS-AERUGINOSA MEMBRANE-PROTEINS INEXPERIMENTALLY INFECTED SHEEP

Shedded sheep inoculated epicutaneously with P. aeruginosa and then we tted experimentally by a sprinkler system, rapidly develop a green bac terial stain. This was associated with an outpouring of serous exudate s onto the skin surface in the fleecerot lesion site. Histopathologica l analysis of dermatitic lesions revealed an infiltration of polymorph onuclear leucocytes into the dermis and the formation of a mosaic of m icroabscesses beneath the sloughed sheets of cornified epithelium. P. aeruginosa if present, was always localized as aggregates at the leadi ng front of the seropurulent exudate and was never observed to invade the dermis. Animals that had been inoculated with P. aeruginosa but ke pt dry, showed no signs of dermatitis or serological reactivity agains t the inoculated bacterium. In contrast, sheep that had been inoculate d and wetted, reacted serologically against P. aeruginosa whole cells in an enzyme-linked immunosorbent assay (ELISA). Eleven of 18 sheep we re considered to be high-antibody responders and registered an ELISA r atio > 2.5 at one or more time points over the duration of the experim ent (14 weeks). Analysis of ELISA reactivity of fleecerot sheep agains t fractionated cell envelope proteins of P. aeruginosa showed a prefer ential antibody response to outer (OMP) rather than inner (LMP) membra ne proteins. Immunoblots revealed strong antibody activity against 2 m ajor OMPs - Opr F and Opr H with apparent molecular masses of 39 and 2 1 kDa respectively. OMPs prepared from sarkosyl-resistant outer membra ne vesicles were electrophoretically identical to OMPs prepared by a m ore rapid and efficient organic phase partitioning procedure (Chin and Dal, 1990). Although two other OMPs - Opr E (44 kDa) and Opr G (25 kD a) were seen in Coomassie blue-stained SDS-PAGE gels of P. aeruginosa OMPs, they were not reactive with sera from fleecerot affected sheep. It is likely that sheep with high levels of circulating serum antibody against major outer membrane proteins of P. aeruginosa may, in the ev ent of a fleecerot episode, exude such antibodies onto the skin surfac e. This could provide a strategy for the control of ovine fleecerot by vaccination if highly conserved outer membrane proteins of P. aerugin osa were found to be protective.