Porphyromonas gingivalis has been implicated as an important pathogen in the development of periodontitis. Hemagglutinins have been identified a s i m p o r t a n t a d h e s i o n m o l e c u l e s , a l l ow i n g Porphyromonas gingivalis to adhere to gingival tissue cells, and to attach and lyse erythrocytes in order to u p t a ke Fe i o n s a s e s s e n t i a l n u t r i t i o n . O n e hemagglutinin, hemagglutinin A (HagA), has been molecularly cloned via functional screening for

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... inating activity. We previously cloned the gene encoding the 200-kDa cell-surface antigenic protein that was reacted by sera from periodontitis patients and was identified as a truncated protein of HagA by nucleotide sequence analysis. We further subcloned the gene encoding an 122-kDa protein (122k-HagA) which is a fusion protein composed of an 80-kDa truncated HagA containing the functional motif PVQNLT and a 42-kDa maltose binding protein. Passive immunization against infectious pathogens by specific antibodies produced from hen egg yolk antibody (IgY) has been extensively developed. In the present study, to develop passive immunotherapy against periodontal disease, we purified the recombinant 122k-HagA and used this to immunize hens and produce IgY. The purified IgY reacted with the recombinant 122k-HagA and the synthetic peptide containing PVQNLT, and inhibited hemagglutinating activity of Porphyromonas gingivalis. Thus, the novel IgY may be useful in the development of a passive immunization against periodontal diseases caused by P. gingivalis infection. (J. Oral Sci. 48, 227-232, 2006)