[Gene cloning of an Actinobacillus actinomycetemcomitans Y4 antigen that reacts to peripheral blood sera in advanced destructive periodontitis patients].

Actinobacillus actinomycetemcomitans (A.a.) has been implicated in the etiology of juvenile periodontitis and also of advanced destructive periodontitis (ADP). It has been reported that the levels of the IgG antibody against the A.a. in the peripheral blood sera of the ADP patients were often high as well as those against the Bacteroides gingivalis. To clone the genes of antigen reactive to the sera of the ADP patients, we constructed a phage library of the A.a. strain Y4 DNA in lambda L47, which was then screened by the immunochemical detection method using a serum from the ADP patient. Of about 1,000 phage clones six were positive with the serum and also the sera of the other patients, and were named 3, 4, 6, 7, 8 and 9 respectively. Restriction enzyme and Southern blot analyses indicated that clones 8 and 9 were identical and that these clones, 3 to 8 were overlapping since they shared in common the 4 kbp and 5kbp Hinc II DNA fragments of the A.a. The cloned DNA fragment hybridized to the DNAs of the two other strains of the A.a. but did not to those of the Bacteroides intermedius, Bacteroides fragilis, Bacteroides melaninogenicus, Bacteroides gigivalis, Capnocytophaga ochracea and Fusobacterium nucleatum. These results suggest that the DNA sequence encoding an A.a. Y4 antigen strongly reactive to the sera of the ADP patients was present specifically in the A.a. but not in the other bacteria isolated from the periodontal patients. Thus, the DNA could serve also as a DNA probe for the diagnosis of periodontitis.