Aggregatibacter actinomycetemcomitans–Induced Bone Loss and Antibody Response in Three Rat Strains

Background: The aim of this study is to compare the colonization, immunoglobulin (Ig) G response, and alveolar bone loss in Aggregatibacter actinomycetemcomitans (Aa)–inoculated Fawn Hooded Hypertensive (FHH), Dahl Salt‐Sensitive (DSS), and Brown Norway (BN) rats. Methods: Each rat strain was divided into wild‐type Aa‐inoculated and non‐inoculated control groups. Blood taken at 12 weeks after inoculation was assessed for Aa‐specific IgG antibodies by an enzyme‐linked immunosorbent assay. Colonization was assessed 12 weeks postinoculation. Bone loss was estimated by measuring the distance from the cemento‐enamel junction (CEJ) to the alveolar bone crest (ABC) at 20 molar sites. Colonization and antibody levels were compared by using the Student t test. Diseased rats were defined as having two sites per quadrant with CEJ–ABC distances that were significantly greater than the control CEJ–ABC distances. Results: The Aa colonization of FHH rats was significantly higher than in other strains (P <0.05). The Aa‐specific IgG levels in the DSS Aa‐inoculated group were significantly higher than in its control group (P <0.05). Only FHH rats showed Aa disease‐associated bone loss (P = 0.0021). Conclusions: Aa colonized and caused more disease in FHH rats than in the other rat strains. The rat strains each responded differently to the same Aa strain.