Persistently elevated IgA antibodies to Mycoplasma pneumoniae in patients with internal carotid artery stenosis

Background: It has been suggested that Mycoplasma pneumoniae may play a role in the development of atherosclerosis, but to date this association is still a matter of debate due to conflicting findings. Methods: We have investigated the levels of specific IgA antibodies to M. pneumoniae in 91 patients with internal carotid artery (ICA) stenosis using a commercial kit (SeroMP™ IgA; Savyon Diagnostics, Israel; cut-off value: 20 binding units; BU). All patients underwent surgery for ICA stenosis. From each patient, the first serum sample (S1) was taken before surgery, and the second after an interval of 6 month (S2). Results: The S1 seroprevalence was 18.7% (17/91). Thirteen of the 17 patients with positive S1 levels also remained positive after six month, whereby no decrease of IgA level was seen (median S1 level: 34 BU, range: 22–65 BU; median S2 level: 37 BU, range: 22–58 BU). Specifically, six of the patients showed an increased level after 6 months, and six a decrease, with the level remaining constant in one patient. In contrast, only 3 of the 74 S1 negative patients became positive for anti-M. pneumoniae IgA between the taking of the first and the second serum specimen (p<0.01). None of the assessed demographic factors or risk factors for atherosclerosis was associated with IgA seropositivity, neither were the degree CAVK or the degree of stenosis. Conclusion: These findings cannot be explained throughout by the general seroprevalence, or by past respiratory tract infections with the pathogen, and therefore may suggest a role for M. pneumoniae in the development of atherosclerosis, since a chronic infection must be assumed.