Immune-response against Streptococcus pyogenes in the development of abdominal aortic aneurysm – A population-based case-control study

Background: In a population-based case-control study the association between antibodies to Streptococcus pyogenes antigens and the development of abdominal aortic aneurysm (AAA) was analysed. Patients and methods: Forty-two patients with screening-detected AAA were compared to 100 age- and sex matched controls with normal aortas. Antibodies against three recently characterized cell wall-attached proteins of S. pyogenes (SclA, SclB and GRAB) were analysed in plasma samples obtained at screening (current), and in samples obtained from a study conducted 12 years previously on the same population (historical). Results: Historical antibody levels against the S. pyogenes antigen GRAB were significantly higher in AAA patients compared with controls (0.25 vs 0.17, p = 0.021). A similar trend was observed in current GRAB antibody levels (0.23 vs 0.17, p = 0.072). GRAB-antibody levels at age 60 years retained the association with AAA in a logistic regression model after adjustment for a history of atherosclerosis (OR 20.2, p = 0.022), current smoking (OR 21.4, p = 0.025) and family history of AAA (OR 12.9, p = 0.053). Current and historical antibody levels against SclA and SclB in AAA patients were similar to those in controls. Conclusions: The results indicate that the immune response against S. pyogenes protein GRAB may be involved in the pathogenesis of AAA.