Immunization with gingipain A hemagglutinin domain of Porphyromonas gingivalis induces IgM antibodies binding to malondialdehyde-acetaldehyde modified low-density lipoprotein.

Treatment of periodontitis has beneficial effects on systemic inflammation markers that relate to progression of atherosclerosis. We aimed to investigate whether immunization with A hemagglutinin domain (Rgp44) of Porphyromonas gingivalis (Pg), a major etiologic agent of periodontitis, would lead to an antibody response cross-reacting with oxidized low-density lipoprotein (OxLDL) and how it would affect the progression of atherosclerosis in low-density lipoprotein receptor-deficient (LDLR-/-) mice. The data revealed a prominent IgM but not IgG response to malondialdehyde-acetaldehyde modified LDL (MAA-LDL) after Rgp44 and Pg immunizations, implying that Rgp44/Pg and MAA adducts may share cross-reactive epitopes that prompt IgM antibody production and consequently confer atheroprotection. A significant negative association was observed between atherosclerotic lesion and plasma IgA to Rgp44 in Rgp44 immunized mice, supporting further the anti-atherogenic effect of Rgp44 immunization. Plasma IgA levels to Rgp44 and to Pg in both Rgp44- and Pg-immunized mice were significantly higher than those in saline control, suggesting that IgA to Rgp44 could be a surrogate marker of immunization in Pg-immunized mice. Distinct antibody responses in plasma IgA levels to MAA-LDL, to Pg lipopolysaccharides (Pg-LPS), and to phosphocholine (PCho) were observed after Rgp44 and Pg immunizations, indicating that different immunogenic components between Rpg44 and Pg may behave differently in regard of their roles in the development of atherosclerosis. Immunization with Rgp44 also displayed atheroprotective features in modulation of plaque size through association with plasma levels of IL-1α whereas whole Pg bacteria achieved through regulation of anti-inflammatory cytokine levels of IL-5 and IL-10. The present study may contribute to refining therapeutic approaches aiming to modulate immune responses and inflammatory/anti-inflammatory processes in atherosclerosis.

IgA antibodies to phosphocholine associate with long-term cardiovascular disease risk.

BACKGROUND AND AIMS: Antibodies to phosphocholine and oxidized LDL (oxLDL) are proposed to modify progression of atherosclerosis. We investigated the prognostic value of antibodies to phosphocholine (PCho), Streptococcus pneumoniae cell wall polysaccharide (CWPS) and oxLDL in defining long-term CVD survival. METHODS: CVD incidence was followed for 18 years and analyzed with baseline plasma IgM, IgG and IgA antibody levels to PCho, CWPS and oxLDL in 1044 subjects of Oulu Project Elucidating Risk of Atherosclerosis study (OPERA). RESULTS: During the follow-up period, 195 subjects (18.7%) had a CVD event. Cox model with ACC/AHA CVD adjustments (ASCVD) showed that IgA levels to PCho and IgA to CWPS were statistically significant factors predicting CVD risk. IgM and IgG antibodies to PCho, CWPS and oxLDL had no effect on CVD risk after adjusting for other risk factors. Net reclassification improvement (categories: 17-year risk <15%, 15-30%, >30%), was 0.06 (-0.001-0.12, p < 0.054), and IDI was 0.0124 (0.0036-0.0211, p < 0.006) with IgA-PCho added to the ASCVD risk model. Seventeen (9.4%) study subjects with CVD events were correctly reclassified into higher risk category while 9 (5.0%) subjects were classified into lower risk category. Among the non-cases, 58 (8.7%) subjects were correctly reclassified into lower risk, and 46 (5.9%) were reclassified into higher risk category. CONCLUSIONS: Plasma IgA antibodies to PCho and Streptococcus pneumoniae CWPS are significant predictors of long-term CVD risk. Additional studies on the role of IgA antibodies in atherogenesis and CVD are warranted.

Characterization of a natural mouse monoclonal antibody recognizing epitopes shared by oxidized low-density lipoprotein and chaperonin 60 of Aggregatibacter actinomycetemcomitans.

Natural antibodies are predominantly antibodies of the IgM isotype present in the circulation of all vertebrates that have not been previously exposed to exogenous antigens. They are often directed against highly conserved epitopes and bind to ligands of varying chemical composition with low affinity. In this study we cloned and characterized a natural mouse monoclonal IgM antibody selected by binding to malondialdehyde acetaldehyde epitopes on low-density lipoprotein (LDL). Interestingly, the IgM antibody cross-reacted with Aggregatibacter actinomycetemcomitans (Aa) bacteria, a key pathogenic microbe in periodontitis reported to be associated with risk factor for atherosclerosis, thus being named as Aa_Mab. It is more intriguing that the binding molecule of Aa to Aa_Mab IgM was found to be Aa chaperonin 60 or HSP60, a member of heat-shock protein family, behaving not only as a chaperone for correct protein folding but also as a powerful virulence factor of the bacteria for inducing bone resorption and as a putative pathogenic factor in atherosclerosis. The findings will highlight the question of whether molecular mimicry between pathogen components and oxidized LDL could lead to atheroprotective immune activity, and also would be of great importance in potential application of immune response-based preventive and therapeutic strategies against atherosclerosis and periodontal disease.

Cerebrospinal fluid antibodies to oxidized LDL are increased in Alzheimer's disease.

Lipoprotein oxidation may play an important role in the pathogenesis of Alzheimer's Disease (AD), and therefore, we investigated cerebrospinal fluid (CSF) antibodies to oxidized low-density lipoprotein (OxLDL) in patients with AD and other neurodegenerative dementias. IgM and IgG antibody titers to OxLDL were measured in 50 CSF samples and 11 plasma samples using chemiluminescent ELISA. All CSF samples contained IgG antibodies, and also most IgM, binding to OxLDL. CSF antibodies to OxLDL were not related to CSF protein or albumin concentrations or plasma antibodies to OxLDL. Competition immunoassay for specificity demonstrated that about 50% of the CSF IgG binding to OxLDL was inhibited by soluble OxLDL. CSF IgG antibodies to OxLDL were significantly increased in AD patients compared to controls and to patients with frontotemporal lobar degeneration. The role of these antibodies in CSF is unknown and further investigations are needed.