Sialic Acid-Binding Immunoglobulin-like Lectin G Promotes Atherosclerosis and Liver Inflammation by Suppressing the Protective Functions of B-1 Cells.

Atherosclerosis is initiated and sustained by hypercholesterolemia, which results in the generation of oxidized LDL (OxLDL) and other metabolic byproducts that trigger inflammation. Specific immune responses have been shown to modulate the inflammatory response during atherogenesis. The sialic acid-binding immunoglobulin-like lectin G (Siglec-G) is a negative regulator of the functions of several immune cells, including myeloid cells and B-1 cells. Here, we show that deficiency of Siglec-G in atherosclerosis-prone mice inhibits plaque formation and diet-induced hepatic inflammation. We further demonstrate that selective deficiency of Siglec-G in B cells alone is sufficient to mediate these effects. Levels of B-1 cell-derived natural IgM with specificity for OxLDL were significantly increased in the plasma and peritoneal cavity of Siglec-G-deficient mice. Consistent with the neutralizing functions of OxLDL-specific IgM, Siglec-G-deficient mice were protected from OxLDL-induced sterile inflammation. Thus, Siglec-G promotes atherosclerosis and hepatic inflammation by suppressing protective anti-inflammatory effector functions of B cells

The effect of a 13-valent conjugate pneumococcal vaccine on circulating antibodies against oxidized LDL and phosphorylcholine in man: a randomized placebo-controlled clinical trial

using the Prevenar-13 vaccine. Twenty-four healthy male volunteers were vaccinated with Prevenar-13, either three times, twice or once in a double-blind, placebo-controlled, randomized single center clinical study. Anti-pneumococcal wall, oxLDL and phosphorycholine antibody levels were measured at a fixed serum dilution, as well as circulating lipid levels over the course of 68 weeks. A significant increase in anti-oxLDL IgG and IgM was seen in the group receiving two doses six months apart compared to the placebo. However, these differences were not observed in the groups receiving a single dose, two doses one month apart, or three doses. This study shows that vaccination with Prevenar-13 does not result in robust anti-oxLDL IgM levels in humans. Further research would be required to test alternative pneumococcal-based vaccines, vaccination regimens or study populations, such as cardiovascular disease patients.Biopharmaceutic

Low levels of IgM antibodies recognizing oxidation-specific epitopes are associated with human non-alcoholic fatty liver disease

Background: Lipid oxidation of membrane phospholipids is accompanied by the formation of oxidation-specific epitopes (OSE). These epitopes are recognized by specific antibodies and represent danger-associated molecular patterns that are generated during chronic inflammatory processes. In a murine model for hepatic inflammation during non-alcoholic fatty liver disease (NAFLD), increased antibody levels targeting OSE were found to be protective. Here, our aim was to determine an association between OSE-specific antibody titers and NAFLD in humans. Methods: IgM and IgG levels with specificity for various OSE were assessed in the plasma of patients with NAFLD (n = 71) and healthy controls (n = 68). Antibody titers were comprehensively analyzed in patients with NAFLD after classification by histological evaluation of liver biopsies. Statistical analysis was performed to determine significant correlations and odds ratios. To study the specificity for NAFLD, plasma antibody titers were measured in patients with hepatitis C (n = 40) and inflammatory bowel disease (n = 62). Results: IgM titers against OSE were lower in patients with NAFLD compared to controls. Further biopsy-based classification of patients with NAFLD did not show any difference in IgM levels. Plasma IgM titers towards the P1 mimotope demonstrated an inverse correlation with markers for obesity, systemic inflammation, and liver damage. In contrast, hepatitis C and increased disease activity during inflammatory bowel disease was not associated with reduced IgM titers. Conclusions: Our data highlight the importance of immune recognition of OSE by IgM antibodies in the pathophysiology of NAFLD

Increased Plasma IgE Accelerate Atherosclerosis in Secreted IgM Deficiency.

RATIONALE: Deficiency of secreted IgM (sIgM-/-) accelerates atherosclerosis in Ldlr-/-mice. Several atheroprotective effects of increased levels of IgM antibodies have been suggested, including preventing inflammation induced by oxidized low-density lipoprotein and promoting apoptotic cell clearance. However, the mechanisms by which the lack of sIgM promotes lesion formation remain unknown. OBJECTIVE: To identify the mechanisms by which sIgM deficiency accelerates atherosclerosis in mice. METHODS AND RESULTS: We here show that both sIgM-/- and Ldlr-/-sIgM-/- mice develop increased plasma IgE titers because of impaired generation of B cells expressing the low-affinity IgE receptor CD23, which mediates the clearance of IgE antibodies. We further report that Ldlr-/-sIgM-/- mice exhibit increased numbers of activated mast cells and neutrophils in the perivascular area of atherosclerotic plaques. Treatment with an anti-IgE-neutralizing antibody fully reversed vascular inflammation and accelerated atherosclerotic lesion formation in cholesterol-fed Ldlr-/-sIgM-/- mice. CONCLUSIONS: Thus, our data identify a previously unsuspected mechanism by which sIgM deficiency aggravates atherosclerosis

Increasing test specificity without impairing sensitivity: lessons learned from SARS-CoV-2 serology

Background: Serological tests are widely used in various medical disciplines for diagnostic and monitoring purposes. Unfortunately, the sensitivity and specificity of test systems are often poor, leaving room for false-positive and false-negative results. However, conventional methods were used to increase specificity and decrease sensitivity and vice versa. Using SARS-CoV-2 serology as an example, we propose here a novel testing strategy: the € sensitivity improved two-test' or € SIT²' algorithm. Methods: SIT² involves confirmatory retesting of samples with results falling in a predefined retesting zone of an initial screening test, with adjusted cut-offs to increase sensitivity. We verified and compared the performance of SIT² to single tests and orthogonal testing (OTA) in an Austrian cohort (1117 negative, 64 post-COVID-positive samples) and validated the algorithm in an independent British cohort (976 negatives and 536 positives). Results: The specificity of SIT² was superior to single tests and non-inferior to OTA. The sensitivity was maintained or even improved using SIT² when compared with single tests or OTA. SIT² allowed correct identification of infected individuals even when a live virus neutralisation assay could not detect antibodies. Compared with single testing or OTA, SIT² significantly reduced total test errors to 0.46% (0.24-0.65) or 1.60% (0.94-2.38) at both 5% or 20% seroprevalence. Conclusion: For SARS-CoV-2 serology, SIT² proved to be the best diagnostic choice at both 5% and 20% seroprevalence in all tested scenarios. It is an easy to apply algorithm and can potentially be helpful for the serology of other infectious diseases

Impaired Autophagy in CD11b+ Dendritic Cells Expands CD4+ Regulatory T Cells And Limits Atherosclerosis in Mice.

Rationale: Atherosclerosis is a chronic inflammatory disease. Recent studies have shown that dysfunctional autophagy in endothelial cells, smooth muscle cells and macrophages, plays a detrimental role during atherogenesis, leading to the suggestion that autophagy-stimulating approaches may provide benefit. Objective: Dendritic cells (DCs) are at the crossroad of innate and adaptive immune responses and profoundly modulate the development of atherosclerosis. Intriguingly, the role of autophagy in DC function during atherosclerosis and how the autophagy process would impact disease development has not been addressed. Methods and Results: Here, we show that the autophagic flux in atherosclerosis-susceptible low-density lipoprotein receptor deficient (Ldlr-/-) mice is substantially higher in splenic and aortic DCs compared to macrophages, and is further activated under hypercholesterolemic conditions. RNA sequencing and functional studies on selective cell populations reveal that disruption of autophagy through deletion of Atg16l1 differentially affects the biology and functions of DC subsets in Ldlr-/- mice under high fat diet. Atg16l1 deficient CD11b+ DCs develop a TGF-beta-dependent tolerogenic phenotype and promote the expansion of regulatory T cells (Tregs), whereas no such effects are seen with Atg16l1 deficient CD8alpha+ DCs. Atg16l1 deletion in DCs (all CD11c-expressing cells) expands aortic Tregs in vivo, limits the accumulation of T helper cells type 1 (Th1), and reduces the development of atherosclerosis in Ldlr-/- mice. In contrast, no such effects are seen when Atg16l1 is deleted selectively in conventional CD8alpha+ DCs and CD103+ DCs. Total T cell or selective Treg cell depletion abrogates the atheroprotective effect of Atg16l1 deficient DCs. Conclusions: In contrast to its pro-atherogenic role in macrophages, autophagy disruption in DCs induces a counter-regulatory response that maintains immune homeostasis in Ldlr-/- mice under high fat diet and limits atherogenesis. Selective modulation of autophagy in DCs could constitute an interesting therapeutic target in atherosclerosis.This study was supported by the British Heart Foundation (CH/10/001/27642 and Grant No. 1659), and the European HEALTH 2013.1.3-3 programm

SIRP alpha on Mouse B1 Cells Restricts Lymphoid Tissue Migration and Natural Antibody Production

The inhibitory immunoreceptor SIRPα is expressed on myeloid and neuronal cells and interacts with the broadly expressed CD47. CD47-SIRPα interactions form an innate immune checkpoint and its targeting has shown promising results in cancer patients. Here, we report expression of SIRPα on B1 lymphocytes, a subpopulation of murine B cells responsible for the production of natural antibodies. Mice defective in SIRPα signaling (SIRPαΔCYT mice) displayed an enhanced CD11b/CD18 integrin-dependent B1 cell migration from the peritoneal cavity to the spleen, local B1 cell accumulation, and enhanced circulating natural antibody levels, which was further amplified upon immunization with T-independent type 2 antigen. As natural antibodies are atheroprotective, we investigated the involvement of SIRPα signaling in atherosclerosis development. Bone marrow (SIRPαΔCYT>LDLR−/−) chimaeric mice developed reduced atherosclerosis accompanied by increased natural antibody production. Collectively, our data identify SIRPα as a unique B1 cell inhibitory receptor acting to control B1 cell migration, and imply SIRPα as a potential therapeutic target in atherosclerosis

The Advancement of Biomaterials in Regulating Stem Cell Fate.

Stem cells are well-known to have prominent roles in tissue engineering applications. Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) can differentiate into every cell type in the body while adult stem cells such as mesenchymal stem cells (MSCs) can be isolated from various sources. Nevertheless, an utmost limitation in harnessing stem cells for tissue engineering is the supply of cells. The advances in biomaterial technology allows the establishment of ex vivo expansion systems to overcome this bottleneck. The progress of various scaffold fabrication could direct stem cell fate decisions including cell proliferation and differentiation into specific lineages in vitro. Stem cell biology and biomaterial technology promote synergistic effect on stem cell-based regenerative therapies. Therefore, understanding the interaction of stem cell and biomaterials would allow the designation of new biomaterials for future clinical therapeutic applications for tissue regeneration. This review focuses mainly on the advances of natural and synthetic biomaterials in regulating stem cell fate decisions. We have also briefly discussed how biological and biophysical properties of biomaterials including wettability, chemical functionality, biodegradability and stiffness play their roles

Prevention of congenital toxoplasmosis in Szeged, Hungary.

Background. Toxoplasma gondii infection of the fetus can only be discovered or prevented by the appropriate serological screening and subsequent treatment of the mother and her offspring. In Hungary, there is no obligatory toxoplasma screening for pregnant women and both the reporting and follow-up of congenital toxoplasmosis cases is limited. In 1987 we started a systematic study in the Szeged region of Hungary, in which all pregnant women were screened and appropriate treatment given to all mothers and their offspring where congenital toxoplasmosis was suspected. Methods. All pregnant women were routinely screened within the first 16 weeks of gestation;or toxoplasma antibodies by complement fixation test (CFT). Seronegative cases were retested for possible seroconversion every second month, Patients with CFT litres greater than or equal to 1:256 were retested for anti-P30 immunoglobulin A (IgA), IgM and IgG antibodies by ELISA and/or SDS-PAGE-Western immunoblot in order to distinguish the acute and chronic phases of the infection. Results. Up to the end of 1994, the sera of 17 735 gravidae were screened. Ten women were found to have seroconverted during pregnancy and 78 had high initial antibody levels accompanied by anti-P30 IgA antibodies at the very first screening. These two groups together were considered as definitely (10) or possibly (78) infected with Toxoplasma during pregnancy and were treated with Spiramycin. Ali of their offspring were also treated for one month and followed-up by systematic serological and clinical screening for 2 years. No congenital toxoplasmosis was found in any of the offspring. Conclusions. Antenatal, early diagnosis and treatment of toxoplasmosis in mothers, together with treatment and followup of their offspring, may considerably reduce the incidence of the disease in the offspring