Production of the entire extracellular domain of BP180 (type XVII collagen) by baculovirus expression

Bullous pemphigoid (BP) is an acquired autoimmune skin disease, and its tar get antigens are a 230 kDa plaque protein (BP230) and a 180 kDa transmembra ne protein with interrupted collagenous domains (BP180, type XVII collagen) , which localize at the hemidesmosome. In this study we have attempted to e xpress the entire extracellular domain of BP180 (rBP180EC) as a secreted pr otein by baculovirus expression. Seventy out of 83 BP sera (84.4%) showed p ositive reactivity against rBP180EC by immunoblot analysis, and 56 out of 8 3 BP sera (67.5%) were positive against rBP180EC by ELISA. These figures we re comparable with those when a bacterial recombinant protein encoding the NC16a domain of BP180 (rNC16a) was used as an antigen source. Reactivity of BP sera against rBP180EC by ELISA was completely abolished or significantl y reduced by immunocompetition with rNC16a in 11 out of 14 BP sera tested, while the reactivity was not altered in the rest of the three sera. These f indings indicate that the NC16a domain represents the major epitopes on the extracellular domain of BP180, although there are some other minor epitope s outside of NC16a which are uniquely expressed by rBP180EC. rBP180EC will be useful to develop a diagnostic tool for BP as well as to dissect a molec ular role for BP180 in interactions of keratinocytes with epidermal basemen t membrane. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.