Identification of IgG1 isotype phosphorylcholine antibodies for the treatment of inflammatory cardiovascular diseases

BACKGROUND

Phosphorylcholine (PC) is an important pro-inflammatory damage-associated molecular pattern. Previous data have shown that natural IgM anti-PC protects against cardiovascular disease. We aimed to develop a monoclonal PC IgG antibody with anti-inflammatory and anti-atherosclerotic properties.

METHODS

Using various techniques PC antibodies were validated and optimized. In vivo testing was performed in a femoral artery cuff model in ApoE3*Leiden mice. Safety studies are performed in rats and cynomolgus monkeys.

RESULTS

A chimeric anti-PC (PC-mAb(T15), consisting of a human IgG1 Fc and a mouse T15/E06 Fab) was produced, and this was shown to bind specifically to epitopes in human atherosclerotic tissues. The cuff model results in rapid induction of inflammatory genes and altered expression of genes associated with ER stress and choline metabolism in the lesions. Treatment with PC-mAb(T15) reduced accelerated atherosclerosis via reduced expression of endoplasmic reticulum stress markers and CCL2 production. Recombinant anti-PC Fab fragments were identified by phage display and cloned into fully human IgG1 backbones creating a human monoclonal IgG1 anti-PC (PC-mAbs) that specifically bind PC, apoptotic cells and oxLDL. Based on preventing macrophage oxLDL uptake and CCL2 production, four monoclonal PC-mAbs were selected, which to various extent reduced vascular inflammation and lesion development. Additional optimization and validation of two PC-mAb antibodies resulted in selection of PC-mAb X19-A05, which inhibited accelerated atherosclerosis. Clinical grade production of this antibody (ATH3G10) significantly attenuated vascular inflammation and accelerated atherosclerosis and was tolerated in safety studies in rats and cynomolgus monkeys.

CONCLUSIONS

Chimeric anti-PCs can prevent accelerated atherosclerosis by inhibiting vascular inflammation directly and through reduced macrophage oxLDL uptake resulting in decreased lesions. PC-mAb represents a novel strategy for cardiovascular disease prevention.

IgM antibodies against phosphorylcholine measured early after acute ST-elevation myocardial infarction in relation to atherosclerotic disease burden and long-term clinical outcome

PURPOSE

Studies have reported an association between low levels of natural immunoglobulin M antibodies against phosphorylcholine(IgM anti-PC) and worse prognosis in patients with coronary artery disease (CAD). The aims of the present study were, in patients with ST-elevation myocardial infarction (STEMI); 1) to compare serum levels of IgM anti-PC measured acutely and after 3 months; 2) to study an association between levels of IgM anti-PC and the severity ofCAD, and; 3) to investigate whether IgM anti-PC levels are associated with long-term clinical outcome.

METHODS

A total of 213 patients without known diabetes (median age 59 years) with a PCI treated STEMI were enrolled. IgM anti-PC was measured in-hospital and after 3 months. Median follow-up time was 6.5 years (all-cause mortality, non-fatal myocardial re-infarction, recurrent ischemia causing hospital admission, heart failure and stroke). The severity of CAD was evaluated by coronary angiograms and patients were classified as having single- or multi-vessel disease and by SYNTAX score (SXscore).

RESULTS

IgM anti-PC levels were stable over time when measured acutely and after 3 months. Patients with multi-vessel disease and high SXscore had significantly lower levels of IgM anti-PC in the acute phase of STEMI. Low levels of IgM anti-PC (the 25 percentile) measured acutely were associated with a 2-fold increase in the odds of having multi-vessel disease (adjusted OR 2.28 (95% CI 1.17, 4.44), p = 0.016), but not with high SXscore (Crude OR 2.20 (95% CI 0.96, 5.07), p = 0.06). Fifty-three patients experienced a new clinical event during long-term follow-up. Low levels of IgM anti PC were not associated with worse prognosis, (crude HR 1.54 (0.87-2.76), p = 0.14).

CONCLUSION

STEMI patients with multi-vessel disease or high SXscore had significantly lower levels of IgM anti-PC in the acute phase and low levels were associated with multi-vessel disease, but not with worse clinical outcome during long-term follow-up.

Long-term Immunotoxic Effects of Oral Prenatal and Neonatal Atrazine Exposure

Atrazine and its metabolites are present at high concentrations in many water supplies in agro-intensive areas. Because residents in these areas drink water from sources fed from these contaminated supplies, we investigated the long-term immunotoxicity of combined prenatal and neonatal (perinatal) exposure to atrazine via drinking water, on the immune system in mice. At 6 months of age, upon immunization with heat-killed Streptococcus pneumoniae, the serum IgG antibody response against the T independent antigen phosphorylcholine was significantly higher in male, but not female, atrazine-exposed mice as compared with that in untreated controls. No alterations were present in all offspring in the serum antibody response against the T-dependent antigen pneumococcal surface protein A (PspA). ELISpot analysis showed only a small, insignificant reduction in PspA-specific IgG producing splenocytes in atrazine-treated male offspring. Interestingly, upon ex vivo stimulation with anti-CD3 and anti-CD28 antibodies, significant decreases in interleukin (IL)-2, tumor necrosis factor-α, interferon-γ, and IL-17A and a decreasing trend in IL-10 were observed in splenocytes from atrazine-exposed male, but not female mice. Analysis of thymic and splenic cell populations showed no effects of atrazine exposure in either sex. This is the first time that long-term changes in the immune response were observed after a perinatal exposure to atrazine and it demonstrates that these early life exposures can result in permanent changes to the immune system as well as a male bias in these effects.

Helminth-Related Tuftsin-Phosphorylcholine Compound and its Interplay with Autoimmune Diseases

The hygiene theory represents one of the environmental facets that modulate the risk for developing autoimmune diseases. There is a reverse correlation between the presence of helminthes and flares of autoimmune diseases, which explains the rise in incidence of certain autoimmune diseases in developed countries. The protective properties of certain helminthes are attributed to their secretory compounds which immunomodulate the host immune network in order to survive. Thus, the helminthes use an array of mechanisms. One of the major mechanisms enabling manipulation of the host-helminth interaction is by targeting the pattern recognition receptors (PRRs)-dependent and -independent mechanisms, which include toll-like receptors, C-type lectin receptors, and the inflammasome. The current review provides a glimpse of numerous helminth secreted products which have a role in the immunomodulation of the host immune network, focusing on bifunctional tuftsin-phosphorylcholine (TPC). TPC is a natural compound based on phosphorylcholine of helminth origin that was used in the past to cover stents and tuftsin, a self-peptide derived from the spleen. TPC was proven to be efficient in three murine experimental models (lupus, colitis, and arthritis) and ex vivo in giant cell arteritis.

Anti-phosphorylcholine IgM, an Anti-inflammatory Mediator, Predicts Peripheral Vein Graft Failure: A Prospective Observational Study

OBJECTIVES

One third of infrainguinal vein bypasses may fail within the first 1.5 years. Pro- and anti-inflammatory mechanisms are thought to be involved in these graft stenoses and occlusions. In previous studies, low levels of anti-phosphorylcholine IgM (anti-PC IgM, an innate anti-inflammatory IgM) have been associated with increased cardiovascular events. In this study, the peri-operative dynamics of anti-PC IgM levels were established during leg bypass surgery, and associations assessed between anti-PC IgM levels and primary graft patency.

DESIGN AND METHODS

This was a prospective, observational cohort study of infrainguinal autogenous vein bypass for peripheral arterial occlusive disease involving four university affiliated hospitals. Plasma cytokine and anti-PC IgM levels were measured pre- and post-operatively. The outcome of interest was loss of primary graft patency because of occlusion or intervention for graft stenosis.

RESULTS

One hundred and forty-two consecutive patients were enrolled: mean age 66 (46-91); 91% white race and male; 72.5% critical limb ischaemia (Fontaine III or IV). Median pre-operative anti-PC IgM levels were 49 units/mL (IQR 32.3-107.7, mean 89.8 + 101 sd). During follow up of an average of 1.8 years (1 month-7.4 years), 50 (35.2%) grafts lost primary patency. Pre-operative levels of interleukin 6 or C-reactive protein did not predict graft failure. Patients with pre-operative anti-PC IgM values in the lowest quartile had a twofold increased risk of graft failure (multivariable Cox proportional hazard, p = .03, HR 2.11, 95% CI 1.09-4.07), even after accounting for the other significant factors of conduit diameter, distal anastomosis, smoking, and the severity of leg ischaemia.

CONCLUSIONS

Low levels of anti-PC IgM are associated with vein bypass graft failure. This biological mediator may be a useful marker to identify patients at higher risk, and offers the potential for novel, directed therapies for vascular inflammation and its consequences.

Association between dietary and metabolic factors and IgM antibodies to phosphorylcholine and malondialdehyde in patients with systemic lupus erythematosus and population-based matched controls

OBJECTIVES

Immunoglobulin M (IgM) antibodies against phosphorylcholine (anti-PC) and malondialdehyde (anti-MDA) are implicated in systemic lupus erythematosus (SLE) as markers with potential protective properties. Low IgM anti-PC levels are more common in SLE than in control population. Little is known what influences the levels of these antibodies. We here studied associations between dietary and metabolic factors and levels of IgM anti-PC and anti-MDA.

METHODS

This study included 109 SLE patients and 106 controls from SLE Vascular Investigation Cohort (SLEVIC). Data on dietary intake (food frequency questionnaires) and metabolic factors were linked with IgM anti-PC and anti-MDA (determined by enzyme-linked immunosorbent assay). Associations between the dietary, metabolic factors and antibodies were analysed with logistic regression. Antibody levels ≤1st tertile were defined as low level.

RESULTS

Low IgM anti-PC and anti-MDA were associated with SLE (odds ratio (OR)=2.5 [95% confidence interval (CI) 1.4-4.4] and OR=1.7 [95% CI 1.0-3.1, respectively). Among SLE patients, overweight/obesity (body mass index >25), elevated high-density lipoprotein (>1.6 mmol/L) and dietary fibre intake (>25.9 g/day) were associated with low IgM anti-PC (OR=2.29 [95% CI 1.06-4.97], OR=2.36 [95% CI 1.01-5.53] and OR=1.24 [95% CI 1.24-6.15], respectively). Further, dietary intake of total fat (>64.0 g/day), specifically saturated fat (>27.1 g/day), was associated with low IgM anti-MDA level (OR=2.55 [95% CI 1.14-5.64] and OR=2.47 [95% CI 1.11-5.51], respectively). Micronutrients were not associated with measured antibodies.

CONCLUSIONS

Some dietary and metabolic factors were associated with IgM anti-PC and anti-MDA, though it is not clear whether the associations also represent causation.

Natural antibodies to oxidation-specific epitopes: innate immune response and venous thromboembolic disease

Essentials Natural antibodies to oxidation-specific epitopes have antithrombotic properties. We evaluated the relation between natural IgM and IgG antibodies and the venous thrombosis risk. Risk of recurrent thrombosis was higher in patients with low natural IgM antibody levels. The protective effect of high IgM levels suggests a role of innate immune response in thrombosis.

SUMMARY

Background and objectives Natural antibodies to oxidation-specific epitopes protect from atherothrombotic events. Whether mechanisms of innate immunity are relevant in the pathogenesis of venous thromboembolism (VTE) is unknown. Patients/Methods We measured plasma levels of immunoglobulin M (IgM) antibodies to oxidized low-density lipoproteins (OxLDL) and phosphocholine (PC) by enzyme linked immune assay in 663 patients with unprovoked VTE, who were prospectively followed after discontinuation of anticoagulation for a median of 8.8 years. The study endpoint was recurrent VTE. Results IgM antibody levels to OxLDL and PC were higher in patients without compared to those with recurrent VTE (n = 174, 26.2%). For each doubling of OxLDL-IgM or PC-IgM the hazard ratio (HR) of recurrence was 0.88 (95% confidence interval [CI], 0.77-1.01) and 0.82 (95% CI, 0.71-0.94), respectively. After 5 years the probability of recurrence in patients with PC-IgM levels in the highest tertile (> 19.6 RLU/100 ms) was 13.0% (95% CI, 8.1-17.6%), compared with 21.1% (95% CI, 14.9-26.9%) in the middle tertile and 20.6% (95% CI, 14.7-26.0%) in the lowest tertile. The corresponding HR was 0.56 (0.39-0.82) for PC-IgM levels in the highest compared with the lowest tertile. Neither immunoglobulin G IgG antibody levels to OxLDL nor those to PC were associated with risk of VTE. Conclusion Levels of natural IgM antibodies to oxidation-specific epitopes are inversely related to the risk of VTE.

The PCome of Ascaris suum as a model system for intestinal nematodes: identification of phosphorylcholine-substituted proteins and first characterization of the PC-epitope structures

In multicellular parasites (e.g., nematodes and protozoa), proteins and glycolipids have been found to be decorated with phosphorylcholine (PC). PC can provoke various effects on immune cells leading to an immunomodulation of the host's immune system. This immunomodulation allows long-term persistence but also prevents severe pathology due to downregulation of cellular immune responses. PC-containing antigens have been found to interfere with key proliferative signaling pathways in B and T cells, development of dendritic cells and macrophages, and mast cell degranulation. These effects contribute to the observed modulated cytokine levels and impairment of lymphocyte proliferation. In contrast to glycosphingolipids, little is known about the PC-epitopes of proteins. So far, only a limited number of PC-modified proteins from nematodes have been identified. In this project, PC-substituted proteins and glycolipids in Ascaris suum have been localized by immunohistochemistry in specific tissues of the body wall, intestine, and reproductive tract. Subsequently, we investigated the PCome of A. suum by 2D gel-based proteomics and detection by Western blotting using the PC-specific antibody TEPC-15. By peptide-mass-fingerprint matrix-assisted laser-desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), we could identify 59 PC-substituted proteins, which are in involved multiple cellular processes. In addition to membrane proteins like vitellogenin-6, we found proteins with structural (e.g., tubulins) and metabolic (e.g., pyruvate dehydrogenase) functions or which can act in the defense against the host's immune response (e.g., serpins). Initial characterization of the PC-epitopes revealed a predominant linkage of PC to the proteins via N-glycans. Our data form the basis for more detailed investigations of the PC-epitope structures as a prerequisite for comprehensive understanding of the molecular mechanisms of immunomodulation.

Antibodies against native and oxidized cardiolipin and phosphatidylserine and phosphorylcholine in atherosclerosis development

Background

Antibodies against cardiolipin and phosphatidylserine (anti-CL and anti-PS) are associated with thrombosis. In contrast, we determined that IgM antibodies against oxidized CL and PS (OxCL and OxPS) and phosphorylcholine (anti-PC) could be protection markers for cardiovascular disease (CVD).

Methods

226 individuals with established hypertension (diastolic pressure>95 mmHg) from the European Lacidipine Study on Atherosclerosis. Antibodies were tested by ELISA. As a surrogate measure of atherosclerosis, the mean of the maximum intima-media thicknesses (IMT) in the far walls of common carotids and bifurcations was determined by ultrasonography at the time of inclusion and 4 years following inclusion.

Results

Increases in IMT measures at follow-up were significantly less common in subjects which at baseline had high IgM anti-OxPS and anti-PC at above 75^th percentile: OR 0,45, CI (0,23–0,86) and OR 0.37, CI (0,19–0,71), p = 0.0137 respectively and above 90^th percentile: OR 0.32, CI (0,12–0,84) and OR 0.39, CI (0,15–1.00), p = 0.050 and OR 0,22, CI (0,08–0,59) p = 0,0029. IgM anti-OxCL was negatively associated with IMT increases (OR, 0.32, CI (0,12–0,84), p = 0231). There were no associations for IgM anti-PS or anti-CL. Anti-PC, as determined herein by a commercial ELISA, was strongly associated with data from our previously published in house ELISA (R = 0,87; p<0,0001).) Anti-PC was also a risk marker at low levels (below 25^th percentile; OR = 2,37 (1,16–4,82), p = 0,0177).

Conclusions

High levels of IgM anti-OxPS and anti-OxCL, but not traditional anti-phospholipid antibodies (anti-PS and anti-CL), are associated with protection against atherosclerosis development. In addition, low IgM anti-PC was a risk marker but high a protection marker.

IgM-antibodies against phosphorylcholine in mothers and normal or low birth weight term newborn infants

OBJECTIVE

To determine levels of athero-protective IgM antibodies against phosphorylcholine in mothers and term-born normal or low birth weight infants.

APPROACH

Twenty three mother-infant pairs were studied, of whom 16 infants were within the normal weight range for gestational age (NGA; 3652[504] g) and 7 were small for gestational age (SGA; birth weight: 2715[255] g), the latter <2SD below the Swedish reference data mean for normal fetal growth. All infants were born at term (mean ± SD 40.5 ± 1.1 weeks). Serum was available from 6 mothers with SGA and 14 with NGA infants. Participating mothers were aged 34.0 ± 3.9 years (no difference between groups). Fourteen neonates were boys and seven were girls. Levels of anti-PC IgM were determined by ELISA.

RESULTS

Neonatal IgM anti-PC levels were low (undetectable in 8 infants out of which 3 were SGA) with a median of 76[range 0-2.51] U/ml. Maternal IgM anti-PC levels were significantly higher (median 7198[range: 25.32-656.0]) U/ml) and the proportion of mothers in highest quartile (>75th percentile) was larger in mothers of NGA-infants (43%) vs. those of SGA-infants (0%, p = 0.032).

CONCLUSIONS

IgM anti-PC levels are low at birth, which suggests that these antibodies do not play a "housekeeping" role in immune function during fetal life/development, but arise predominately on exposure to external antigens after birth. Furthermore, low maternal IgM anti-PC levels may play a role in placental insufficiency, contributing to poor fetal growth and a small-for-date baby. This preliminary observation may have implications for the future risk of atherosclerosis/cardiovascular disease development in pregnant women and their offspring.

Relation of carotid plaque with natural IgM antibodies in patients with systemic lupus erythematosus

Noninvasive carotid measurements have proven value in the estimation of future cardiovascular (CV) outcomes in systemic lupus erythematosus (SLE). Natural IgM-antibodies to phosphorylcholine (PC) epitopes can enhance apoptotic-cell clearance and induce anti-inflammatory pathways. Herein, we show that subclinical CV disease, as detected by carotid ultrasound, in a cross-sectional SLE cohort was associated with lower levels of IgM anti-PC, as well as lower levels of the ratio of IgM anti-PC/total IgM, compared to patients without plaque (p=0.004 and p=0.02, respectively). The IgM anti-PC/total IgM association remained significant after adjusting for age, cholesterol and hypertension. Adiponectin and sE-selectin were significantly elevated in patients with plaque, and statistical models showed that combining adiponectin, sE-selectin and IgM anti-PC/total IgM was better for predicting plaque than either test alone. These results support the hypothesis that IgM-natural autoantibodies may inhibit atherogenesis, and confirm the utility of IgM anti-PC levels as a biomarker for subclinical CV disease.

Low levels of a natural IgM antibody are associated with vein graft stenosis and failure

BACKGROUND

All humans have natural, protective antibodies directed against phosphorylcholine (PC) epitopes, a common inflammatory danger signal appearing at sites of cell injury, oxidative stress, and on bacterial capsules. In large human cohorts, low levels of anti-PC IgM were associated with a significantly increased risk of stroke or myocardial infarction. However, it is not known if these antibodies protect against the premature closure of arterial reconstructions.

METHODS

A prospective, observational study of patients undergoing elective, infrainguinal, autogenous vein bypasses for atherosclerotic occlusive disease of the legs was conducted. Clinical data were recorded prospectively, and preoperative levels of anti-PC IgM measured with the CVDefine kit from Athera Biotechnologies (Solna, Sweden). The principal clinical end point was the loss of primary patency (loss of graft flow, or any intervention for stenosis). Patients were followed regularly by duplex ultrasound at 1, 3, 6, 12, 18 months, and yearly thereafter.

RESULTS

Fifty-six patients were studied, for an average of 1.3 years. Indications for surgery were claudication (33.9%), ischemic rest pain (17.9%), and ischemia with ulceration or gangrene (48.2%). Seventeen (30.4%) patients experienced loss of primary patency (10 graft occlusions, seven surgical or endovascular revisions of graft stenoses). Kaplan-Meier survival analysis showed that the quartile of patients with the lowest anti-PC IgM levels had significantly worse primary graft patency (log-rank test, P = .0085). Uni- and multivariate Cox proportional hazards analysis revealed that the preoperative anti-PC IgM level was an important predictor of graft failure. Patients with IgM values in the lowest quartile had a 3.6-fold increased risk of graft failure (95% confidence interval: 1.1-12.1), even after accounting for other significant clinical or technical factors such as indication for surgery, site of distal anastomosis, or vein graft diameter.

CONCLUSIONS

A naturally occurring IgM antibody directed against the proinflammatory epitope PC may be protective against vein graft stenosis and failure, through anti-inflammatory mechanisms. Measurement of this antibody may be a useful prognostic indicator, although larger studies of more diverse populations will be needed to confirm these results. The biological actions of anti-PC IgM suggest it may be useful in developing immunotherapies to improve bypass longevity.

Phosphocholine-binding antibody activities are hierarchically encoded in the sequence of the heavy-chain variable region: dominance of self-association activity in the T15 idiotype

A methodology based on the representation of each amino acid of a protein sequence by the electron-ion interaction potential and subsequent analysis by signal processing was used to determine the characteristic or common frequency (in Hz) that reflects the biological activity shared among phosphocholine (PC)-binding antibodies. The common frequency for the variable portion of the heavy chain (VH) of the PC-specific antibodies is found to be at f = 0.37 Hz. The VH sequences of the PC-binding antibodies exhibit three subsites for the PC moiety where hypervariable region 2 (CDR2) plays a role in the interaction with the phosphate group. Mutations in this VH region have an impact on the ability of mutant variants to bind PC and its carrier molecule, as well as on the characteristic frequency shift toward f = 0.12 Hz for mutants failing to bind both hapten and carrier. The VH sequence of mutants that retain the ability to bind PC still shows f = 0.37 Hz, suggesting that this frequency determines PC binding. However, this statement was not confirmed as mutation in another PC subsite impairs PC binding but retains both the phosphate-group recognition and the frequency at f = 0.37 Hz. Herein, this finding is discussed to promote the idea that the VH sequence of the PC-binding antibodies encodes the subsite for phosphate-group binding as a dominant functional activity and that only CDR2 of the T15-idiotype antibodies together with FR3 region form an autonomous self-association function represented by the T15VH50-73 peptide with f = 0.37±0.05 Hz. Thus, these data confirmed that T15VH50-73 peptide might be used in superantibody technology.

IgM antibodies against apoptotic cells and phosphorylcholine in patients with acute myocardial infarction in relation to infarct size and inflammatory response

BACKGROUND

Natural IgM antibodies, and anti-phosphorylcholine IgM (anti-PC IgM) in particular, may modulate the pathogenesis of acute myocardial infarction (AMI).

OBJECTIVES

An exploratory study was conducted to evaluate the hypothesis that circulating anti-PC IgM and IgM binding to damaged cells increases the infarct size and post-infarct inflammatory response in patients with AMI.

MATERIAL AND METHODS

Plasma IgM binding to apoptotic cells (anti-apop IgM) and anti-PC IgM levels were compared in plasma samples from 50 patients with AMI and 46 healthy controls after correction for hemodilution. The cumulative release of cardiac markers LDH (lactate dehydrogenase), CK or CK-MB in human myocardium at 48 hours was used as an indication of infarct size. The circulating levels of mediators such as activated complement, C-reactive protein (CRP), interleukin-6 (IL6), interleukin-8 (IL8) and secretory phospholipase A2 (sPLA2) were used to assess the post-infarct inflammatory response. Patients with low (< median) and high (> median) levels of anti-apop IgM or anti-PC IgM were compared regarding infarct size and post-infarct inflammatory response. An electrocardiographical scoring system (Selvester score) was used to asses myocardial infarct size in patients with a first AMI (n = 24).

RESULTS

AMI patients demonstrated lower levels of anti-PC IgM on admission (p < 0.01) and at 48 hours (p < 0.001) when compared to the healthy controls, whereas anti-apop IgM levels were comparable to control levels. In patients with a first infarct, patients with levels of anti-PC IgM above the median demonstrated larger electrocardiographic infarct sizes (p = 0.04) and a more pronounced response of the acute phase protein sPLA2 (p = 0.06), with a similar post-infarct course of LDH, CK and CK-MB.

CONCLUSIONS

These findings suggest that anti-PC IgM plasma levels may participatie in amplifying the inflammatory response of the ischemic heart and contribute to infarct size. However, the levels of anti-PC IgM in patients with AMI in this study do not show a significant effect on cardiac markers LDH, CK and CK-MB. Hence, conclusive evidence is not provided by this limited cohort.

Effect of biological therapy on levels of atheroprotective antibodies against phosphorylcholine and apolipoproteins in rheumatoid arthritis - a one year study

OBJECTIVES

To examine how treatment of rheumatoid arthritis (RA) with anti-tumour necrosis factor alpha antagonists (anti-TNF) and B-cell targeting rituximab influences novel markers of atherosclerosis and inflammation, such as atheroprotective natural IgM antibodies against phosphorylcholine (anti-PC), oxidised low-density lipoprotein (oxLDL) and apolipoproteins.

METHODS

In a prospective study 215 patients with RA were enrolled of whom 85.6% were seropositive, aged 57.9 ± 12.4 years, with mean disease duration 8.5 (5-15) years. 162 patients were treated with anti-TNF and 53 with rituximab for one year. The patients were assessed and blood sampled at 0, 3, 6 and 12 months. IgM anti-PC and oxLDL were determined by ELISA and apolipoproteins by immunoturbidimetry.

RESULTS

IgM anti-PC increased by 26% during anti-TNF treatment, p<0.001, while decreased by 14% on rituximab, p=0.023, after 12 months of treatment. Patients in remission after 12 months, DAS28<2.6, had higher baseline anti-PC levels compared with those not in remission in both anti-TNF, p=0.007, and rituximab-treated subjects, p=0.041. In both treatment groups, levels of oxLDL increased temporarily at three months but apoA1 improved throughout the study. This effect was inversely correlated with changes in disease activity. The apoB and apoB/apoA1-ratio remained stable throughout the whole study period.

CONCLUSIONS

Anti-TNF treatment demonstrated a favourable long-term effect on anti-PC levels. Low levels of IgM anti-PC may identify immune-deficient state and predict inferior therapy response. Biological therapies increased the level of the anti-atherogenic lipid apoA1. The impact of these effects on future CVD events deserves further studies.

Absence of N addition facilitates B cell development, but impairs immune responses

The programmed, stepwise acquisition of immunocompetence that marks the development of the fetal immune response proceeds during a period when both T cell receptor and immunoglobulin (Ig) repertoires exhibit reduced junctional diversity due to physiologic terminal deoxynucleotidyl transferase (TdT) insufficiency. To test the effect of N addition on humoral responses, we transplanted bone marrow from TdT-deficient (TdT(-/-)) and wild-type (TdT(+/+)) BALB/c mice into recombination activation gene 1-deficient BALB/c hosts. Mice transplanted with TdT(-/-) cells exhibited diminished humoral responses to the T-independent antigens α-1-dextran and (2,4,6-trinitrophenyl) hapten conjugated to AminoEthylCarboxymethyl-FICOLL, to the T-dependent antigens NP(19)CGG and hen egg lysozyme, and to Enterobacter cloacae, a commensal bacteria that can become an opportunistic pathogen in immature and immunocompromised hosts. An exception to this pattern of reduction was the T-independent anti-phosphorylcholine response to Streptococcus pneumoniae, which is normally dominated by the N-deficient T15 idiotype. Most of the humoral immune responses in the recipients of TdT(-/-) bone marrow were impaired, yet population of the blood with B and T cells occurred more rapidly. To further test the effect of N-deficiency on B cell and T cell population growth, transplanted TdT-sufficient and -deficient BALB/c IgM(a) and congenic TdT-sufficient CB17 IgM(b) bone marrow were placed in competition. TdT(-/-) cells demonstrated an advantage in populating the bone marrow, the spleen, and the peritoneal cavity. TdT deficiency, which characterizes fetal lymphocytes, thus appears to facilitate filling both central and peripheral lymphoid compartments, but at the cost of altered responses to a broad set of antigens.

Patients with polycystic ovary syndrome have lower levels of IgM anti-phosphorylcholine antibodies than healthy women

INTRODUCTION

IgM antibodies against phosphorylcholine (IgM anti-PC) are natural autoantibodies, possibly exerting one of the atheroprotective functions of the immune system. Increased levels of these antibodies reduce the development of atherosclerosis in mice, and low levels of IgM anti-PC have been associated with increased risk for cardiovascular disease (CVD). This study compared levels of IgM anti-PC in women with polycystic ovary syndrome (PCOS, n = 111) and healthy controls (n = 79).

METHOD

Levels of IgM anti-PC were measured with ELISA.

RESULTS

The median level of IgM anti-PC in patients with PCOS was not significantly different compared to control subjects. However, the proportion of patients with PCOS with low levels of IgM anti-PC, defined as number of individuals below the median level, was significantly higher than among healthy controls, p < 0.05. Patients with PCOS in the oldest age quintile had significantly lower level of IgM anti-PC than control subjects of similar age (p < 0.05) and younger women with PCOS (p < 0.01).

CONCLUSION

Our results indicate that women with PCOS more frequently display below-median levels of IgM anti-PC than controls and older women with PCOS have lower median anti-PC levels. Further studies of how this finding translates into actual CVD risk in women with PCOS are needed.

Anti-phosphorylcholine-opsonized low-density lipoprotein promotes rapid production of proinflammatory cytokines by dendritic cells and natural killer cells

BACKGROUND AND OBJECTIVE

Epidemiological and animal studies suggest that periodontal infections increase atherosclerosis risk. Periodontitis patients have elevated levels of anti-phosphorylcholine (anti-PC) reactive not only with numerous periodontal organisms but also with minimally modified low-density lipoprotein (mmLDL). Dendritic cells (DCs) reside in arterial walls and accumulate in atherosclerotic lesions. The ability of anti-PC to bind mmLDL prompted the hypothesis that opsonized mmLDL would stimulate DCs and enhance the production of proinflammatory cytokines that promote atherogenic plaque development.

MATERIAL AND METHODS

Monocyte-derived DCs (mDCs) were generated using granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, then stimulated with mmLDL or with anti-PC-opsonized mmLDL. The anti-PC effect was determined using flow cytometry, cofocal microscopy and cytokine assays. The production of CD83, IL-12p35 mRNA, IL-12p40 mRNA, IL-12p70 and IL-10 by DCs was monitored.

RESULTS

Dendritic cells stimulated with mmLDL expressed little CD83 and produced little IL-12p70. However, anti-PC-opsonized mmLDL enhanced DC maturation, as indicated by upregulated CD83 and rapid (≤ 48 h) production of IL-12p70 if a source of interferon-γ (IFN-γ) was available. In leukocyte cultures, natural killer (NK) cells rapidly produced IFN-γ (≤ 48 h) when interacting with IL-12-producing DCs activated by anti-PC-opsonized mmLDL. Moreover, IFN-γ promoted DC IL-12 responses that were further augmented when mmLDL was opsonized with anti-PC.

CONCLUSION

Minimally modified LDL-stimulated DCs and NK cells were mutually stimulatory, with DC IL-12p70 needed by NK cells and with NK cell IFN-γ needed by DCs. Moreover, production of these proinflammatory cytokines was markedly enhanced when LDL was opsonized by anti-PC. In short, the data suggest that the elevated anti-PC levels in periodontitis patients could promote a mechanism that facilitates atherosclerosis.

National pholcodine consumption and prevalence of IgE-sensitization: a multicentre study

BACKGROUND

The aim of this study was to test, on a multinational level, the pholcodine (PHO) hypothesis, i.e. that the consumption of PHO-containing cough mixtures could cause higher prevalence of IgE antibodies to PHO, morphine (MOR) and suxamethonium (SUX). As a consequence the risk of anaphylaxis to neuromuscular blocking agents (NMBA) will be increased.

METHODS

National PHO consumptions were derived from the United Nations International Narcotics Control Board (INCB) database. IgE and IgE antibodies to PHO, MOR, SUX and P-aminophenyl-phosphoryl choline (PAPPC) were measured in sera from atopic individuals, defined by a positive Phadiatop test (>0.35 kU(A)/l), collected in nine countries representing high and low PHO-consuming nations.

RESULTS

There was a significant positive association between PHO consumption and prevalences of IgE-sensitization to PHO and MOR, but not to SUX and PAPPC, as calculated both by exposure group comparisons and linear regression analysis. The Netherlands and the USA, did not have PHO-containing drugs on the markets, although the former had a considerable PHO consumption. Both countries had high figures of IgE-sensitization.

CONCLUSION

This international prevalence study lends additional support to the PHO hypothesis and, consequently, that continued use of drugs containing this substance should be seriously questioned. The results also indicate that other, yet unknown, substances may lead to IgE-sensitization towards NMBAs.

Recognition of lyso-phospholipids by human natural killer T lymphocytes

Natural killer T (NKT) cells are a subset of T lymphocytes with potent immunoregulatory properties. Recognition of self-antigens presented by CD1d molecules is an important route of NKT cell activation; however, the molecular identity of specific autoantigens that stimulate human NKT cells remains unclear. Here, we have analyzed human NKT cell recognition of CD1d cellular ligands. The most clearly antigenic species was lyso-phosphatidylcholine (LPC). Diacylated phosphatidylcholine and lyso-phosphoglycerols differing in the chemistry of the head group stimulated only weak responses from human NKT cells. However, lyso-sphingomyelin, which shares the phosphocholine head group of LPC, also activated NKT cells. Antigen-presenting cells pulsed with LPC were capable of stimulating increased cytokine responses by NKT cell clones and by freshly isolated peripheral blood lymphocytes. These results demonstrate that human NKT cells recognize cholinated lyso-phospholipids as antigens presented by CD1d. Since these lyso-phospholipids serve as lipid messengers in normal physiological processes and are present at elevated levels during inflammatory responses, these findings point to a novel link between NKT cells and cellular signaling pathways that are associated with human disease pathophysiology.

Rheumatoid cachexia is associated with dyslipidemia and low levels of atheroprotective natural antibodies against phosphorylcholine but not with dietary fat in patients with rheumatoid arthritis: a cross-sectional study

INTRODUCTION

Patients with rheumatoid arthritis (RA) have an increased risk for cardiovascular disease (CVD) independent of traditional risk factors. The aim of this study was to analyze the associations between diet, body composition, lipids and atheroprotective natural antibodies against phosphorylcholine (anti-PC) in patients with RA.

METHODS

A total of 80 RA patients (76% women), mean age (standard deviation (SD)) 61.4 (12) years and median disease duration of 6 years, were assessed by food frequency questionnaire (FFQ), fatty acid profile in adipose tissue and whole-body dual energy x ray absorptiometry (DXA). Rheumatoid cachexia was defined as fat free mass index below the 25th percentile and fat mass index above the 50th percentile of a reference population. Blood lipids, oxidized low-density lipoprotein (oxLDL) and anti-PC levels were determined.

RESULTS

The mean body mass index for the women and men was 25.0 and 27.0, respectively. Central obesity was found in 57% of the women (waist circumference >80 cm) and in 89% of the men (waist circumference >94 cm). In all, 18% of the women and 26% of the men had rheumatoid cachexia. These patients had significantly higher total cholesterol (P < 0.033), LDL (P < 0.029), and trendwise oxLDL (P = 0.056) as well as lower anti-PC IgM (P = 0.040), higher frequency of hypertension (69%) and metabolic syndrome (25%) than those without. The patients reported a high dietary intake of saturated fat, which partly correlated with fatty acid composition in adipose tissue and significantly with disease activity. However, patients with or without cachexia did not differ with respect to dietary fat intake or intake of Mediterranean-like diet. Additionally, patients on a Mediterranean-like diet had high levels of anti-PC (P < 0.001).

CONCLUSIONS

About one in five patients with low-active RA displayed rheumatoid cachexia. This condition was associated with high levels of LDL cholesterol, low levels of atheroprotective anti-PC and high frequency of hypertension, which is of interest in the context of CVD in RA. The cachexia could not be related to diet fat intake. However, patients on a Mediterranean-like diet had high anti-PC levels in spite of similar frequency of cachexia. High anti-PC levels may provide some protection against CVD.

Lipooligosaccharides containing phosphorylcholine delay pulmonary clearance of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi) causes pulmonary infections in patients with chronic obstructive pulmonary disease and other mucociliary clearance defects. Like many bacteria inhabiting mucosal surfaces, NTHi produces lipooligosaccharide (LOS) endotoxins that lack the O side chain. Persistent NTHi populations express a discrete subset of LOS glycoforms, including those containing phosphorylcholine (PCho). In this study, we compared two NTHi strains with isogenic mutants lacking PCho for clearance from mice following pulmonary infection. Consistent with data from other model systems, populations of the strains NTHi 2019 and NTHi 86-028NP recovered from mouse lung contained an increased proportion of PCho+ variants compared to that in the inocula. PCho- mutants were more rapidly cleared. Serial passage of NTHi increased both PCho content and bacterial resistance to clearance, and no such increases were observed for PCho- mutants. Increased PCho content was also observed in NTHi populations within non-endotoxin-responsive C3H/HeJ and Toll-like receptor 4 null (TLR4-/-) mice, albeit at later times postinfection. Changes in bacterial subpopulations and clearance were unaffected in TLR2-/- mice compared to the subpopulations in and clearance from mice of the parental strain. The clearance of PCho- mutants occurred at earlier time points in both strain backgrounds and in all types of mice. Comparison of bacterial populations in lung tissue cryosections by immunofluorescent staining showed sparse bacteria within the air spaces of C57BL/6 mice and large bacterial aggregates within the lungs of MyD88-/- mice. These results indicate that PCho promotes bacterial resistance to pulmonary clearance early in infection in a manner that is at least partially independent of the TLR4 pathway.

The phosphorycholine moiety of the filarial nematode immunomodulator ES-62 is responsible for its anti-inflammatory action in arthritis

OBJECTIVE

In countries where parasitic infections are endemic, autoimmune disease is relatively rare, leading to the hypothesis that parasite-derived immunomodulators may protect against its development. Consistent with this, we have previously demonstrated that ES-62, a 62 kDa phosphorylcholine (PC)-containing glycoprotein that is secreted by filarial nematodes, can exert anti-inflammatory action in the murine collagen-induced arthritis (CIA) model and human rheumatoid arthritis-derived synovial tissue cultures. As a first step to developing ES-62-based drugs, the aim of this study was to determine whether the PC-moiety of ES-62 was responsible for its anti-inflammatory actions.

METHODS

We compared the anti-inflammatory activity of a PC-free form of recombinant ES-62 (rES-62) and a synthetic PC-ovalbumin conjugate (OVA-PC) with that of native ES-62 in the CIA model and synovial tissues from patients with rheumatoid arthritis.

RESULTS

The anti-inflammatory actions of ES-62 in CIA appear to be dependent on the PC moiety as indicated by the reduction in severity of disease and also suppression of collagen-specific T helper 1 cytokine production observed when testing OVA-PC, but not rES-62. Interestingly, the anti-inflammatory activity of PC did not correlate with a reduction in anti-collagen IgG2a levels. Also, the ES-62-mediated suppression of interferon-gamma from human patient tissues could be mimicked by OVA-PC but not rES-62 or ovalbumin.

CONCLUSIONS

In countries where filariasis is endemic the reduced detection of inflammatory diseases, such as rheumatoid arthritis may be because of the anti-inflammatory action of the PC moieties of ES-62. PC may thus provide the starting point for the development of novel, safe immunomodulatory therapies.

Phosphorylcholine-Targeting Immunization Reduces Atherosclerosis

OBJECTIVES

The present study evaluated the effect of phosphorylcholine (PC) immunization on the extent of experimental atherosclerosis.

BACKGROUND

Immunization against oxidized lipoprotein (oxLDL) or Streptococcus pneumoconiae reduces atherosclerosis. Phosphorylcholine is the main epitope recognized by both antipneumococcus and anti-oxLDL antibodies. Therefore we reasoned that PC-specific antibodies might play an important role in atherogenesis.

METHODS

Apolipoprotein E knockout mice were immunized with PC every second week over 4 months. At the end of the study, serum antibodies directed to either PC or oxLDL were measured. Splenic and peritoneal B cells were analyzed by flow cytometry. Aortic root atherosclerotic lesions were quantified by morphometry and phenotyped by immunohistochemistry. Immune and control sera were also tested for their effect on foam cell formation in macrophage culture in the presence of oxLDL.

RESULTS

The PC-immunized mice showed 3-fold increase in titers of anti-PC and -oxLDL antibodies compared with control mice (p < 0.01). The PC-immunized mice also showed a significant increase in the number of splenic mature B cells. The extent of atherosclerotic aorta root lesions was reduced by >40% in the PC-immunized mice (p < 0.01). Immunohistochemistry showed reduced expression of major histocompatibility complex class II antigens (p < 0.05) and the presence of B-cell clusters in plaques of PC-immunized mice. Finally, PC-immune serum was able to reduce macrophage-derived foam cell formation in the presence of oxLDL in vitro.

CONCLUSIONS

Phosphorylcholine immunization drives a specific humoral immune response that reduces foam cell formation in vitro and is atheroprotective in vivo.

Sphingosylphosphorylcholine activates dendritic cells, stimulating the production of interleukin-12

Compared with other lysophospholipid mediators such as sphingosine-1-phosphate and lysophosphatidic acid, little is known about the physiological significance of the related bioactive lysosphingolipid sphingosylphosphorylcholine (SPC), which is present in high-density lipoprotein particles. The present study was undertaken to evaluate the effect of SPC on human immature dendritic cells (DCs). Reverse transcription-polymerase chain reaction and flow cytometry assays revealed that DCs express two putative receptors for SPC, ovarian cancer G-protein-coupled receptor 1 and G-protein-coupled receptor 4. Exposure to SPC induced a rapid and transient increase in intracellular free calcium concentrations but did not stimulate endocytosis or chemotaxis of DCs. SPC increased the expression of HLA-DR, CD86 and CD83 and improved the T-cell priming ability of DCs, as well as the ability of DCs to stimulate the production of interferon-gamma by allogeneic peripheral blood mononuclear cells during the mixed lymphocyte reaction. Consistent with these results, we also observed that SPC stimulated the production of interleukin (IL)-12 and IL-18 by DCs. Taken together, our results support the notion that the accumulation of SPC in peripheral tissues during the course of inflammatory processes may favour the development of T helper type 1 immunity.

Cross-reactivity of anti-phosphorylcholine antibodies to neuromuscular blockers in a murine model of immunization

Hypersensitivity reactions to curare-like neuromuscular blocking agents (NMBA) used in anesthesiology are more frequent in females and often occur at the first exposure to these drugs. To evaluate the antibody response to a hapten sharing the same allergenic epitope with NMBA in a murine model of immunization with Nitrophenylphosphorylcholine (NPPC) coupled with Keyhole Limpet Hemocyanin (KLH). BALB/c mice from both sexes were intraperitoneally immunized with NPPC-KLH with alum and boosted twice, on 7 and 14 days. The antibodies were tested for specificity to PC and for cross-reactivity to the haptens, NPPC and PC, as well as to the NMBAs. Mice immunized with NPPC-KLH produced anti-PC antibodies mainly of IgM, IgG1 and IgG3 isotypes, at similar levels in both sexes. Different affinities for the haptens were detectable between isotypes, with anti-PC IgG3 antibody reactivity mostly related to the choline portion of the NPPC hapten. When comparing among sexes, females developed greater IgG2 affinity to the hapten than males. Cross-reactivity to NMBAs was predominant among the anti-PC IgG3 antibodies, mainly in females achieving 75% of inhibition with 16 mM of suxamethonium, while other isotypes achieved up to 30% and was absent for IgE. The investigation of antibody isotypes regarding sensitization to choline-derived structures could contribute to understanding the differential ability of females to produce antibodies that are cross-reactive with NMBAs.

Phosphorylcholine mimics the effects of ES-62 on macrophages and dendritic cells

Modulation of macrophage/dendritic cell (DC) cytokine production by the filarial nematode phosphorylcholine (PC)-containing product, ES-62, is mediated by Toll-like receptor (TLR) 4 and signal transduction depends on the TLR adaptor MyD88. Intriguingly, comparison of TLR4 knock-out (ko) mice with TLR4 mutant C3H/HeJ mice indicates that ES-62 cytokine responses are not dependent on the Pro712 residue of TLR4, which is crucial for the response to bacterial lipopolysaccharide (LPS). Because other immunomodulatory effects of ES-62 have been attributed to PC we have now investigated, using PC conjugated to ovalbumin (PC-Ova), whether PC is responsible for the interaction of ES-62 with TLR4. PC-Ova mimicked the modulation of interleukin (IL)-12 production by ES-62 in a TLR4- and MyD88-dependent manner and as with native ES-62, PC-Ova effects were not dependent on Pro712. Furthermore, both native ES-62 and PC-Ova suppressed Akt phosphorylation, whereas neither altered the activation of p38 or Erk MAP kinases. To rule out any role for the ES-62 protein component, we tested a PC-free recombinant ES-62 (rES-62) generated in the yeast Pichia pastoris. Surprisingly, rES-62 also modulated IL-12 production, but in a TLR4/MyD88-independent manner. Furthermore, rES-62 strongly activated both the p38 and Erk MAP kinases and Akt. However, recent biophysical analysis suggests there are differences in folding/shape between native and rES-62 and hence data obtained with the latter should be treated with caution. Nevertheless, although our study indicates that PC is likely to be primarily responsible for the modulation of cytokine production observed with native ES-62, an immunomodulatory role for the protein component cannot be ruled out.

Intranasal immunization with phosphorylcholine induces antigen specific mucosal and systemic immune responses in mice

Phosphorylcholine (PC) is a structural component of a wide variety of pathogens including Streptococcus pneumoniae and Haemophilus influenzae, and anti-PC immune responses are known to protect mice against invasive bacterial diseases. The present study tested the capability of PC as an intranasal plurispecific vaccine against upper airway infections. BALB/c mice immunized with intranasal PC-keyhole limpet hemocyanin (KLH) plus cholera toxin (CT) as a mucosal adjuvant showed increased PC-specific IgM in serum, IgA in nasal wash and saliva, and numbers of PC-specific nasal and splenic antibody producing cells. Enhanced production of IL-4 and IFN-gamma by CD4+ T cells indicated the participation of Th2- and Th1-type cells. Salivary IgA antibodies produced by intranasal immunization with PC-KLH plus CT reacted to most strains of S. pneumoniae and H. influenzae. Further we demonstrated that the clearance of S. pneumoniae and H. influenzae from the nasal tract was significantly enhanced by nasal immunization with PC-KLH and CT. Thus, intranasal vaccination to induce PC-specific immune responses might help to prevent upper airway infections caused by S. pneumoniae and H. influenzae.

Carrier-specificity of a phosphorylcholine-binding antibody requires the presence of the constant domains and is not dependent on the unique VH49 glycine or VH30 threonine residues

Bacterially-produced antibody fragments, such as single-chain Fv (scFv) which comprises the variable regions of the light (VL) and heavy (VH) chains joined together by a short flexible linker, are useful as diagnostic and therapeutic agents. We previously constructed a scFv fragment from a hybridoma antibody (Mab2) but it unexpectedly lacked the unique carrier specificity of the native antibody. Thus, it bound indiscriminately to various phosphorylcholine (PC)-associated antigens, whereas the hybridoma antibody recognized the PC epitope only in the context of the immunizing antigen. Here, we investigated whether the problem was linker-related by changing the linker composition or by deleting it, but these attempts proved futile. Instead, we have constructed a recombinant Fab fragment of the antibody in bacteria that was carrier-specific. This suggests that constant regions are required for the carrier specificity, which presumably helps to mould the fine structure of the antibody combining site or in stabilizing such a structure. Consistent with this global effect is the finding that replacing specific residues in VH with germ-line residues, namely, VH49 glycine and VH30 threonine, both thought previously to be important for the carrier specificity, had no effect on the carrier specificity of the recombinant Fab.

Phosphorylcholine decreases early inflammation and promotes the establishment of stable biofilm communities of nontypeable Haemophilus influenzae strain 86-028NP in a chinchilla model of otitis media

Nontypeable Haemophilus influenzae (NTHi) is a leading causative agent of otitis media. Much of the inflammation occurring during NTHi disease is initiated by lipooligosaccharides (LOS) on the bacterial surface. Phosphorylcholine (PCho) is added to some LOS forms in a phase-variable manner, and these PCho(+) variants predominate in vivo. Thus, we asked whether this modification confers some advantage during infection. Virulence of an otitis media isolate (NTHi strain 86-028NP) was compared with that of an isogenic PCho transferase (licD) mutant using a chinchilla (Chinchilla lanigera) model of otitis media. Animals infected with NTHi 86-028NP licD demonstrated increased early inflammation and a delayed increase in bacterial counts compared to animals infected with NTHi 86-028NP. LOS purified from chinchilla-passed NTHi 86-028NP had increased PCho content compared to LOS purified from the inoculum. Both strains were recovered from middle ear fluids as long as 14 days postinfection. Biofilms were macroscopically visible in the middle ears of euthanized animals infected with NTHi 86-028NP 7 days and 14 days postchallenge. Conversely, less dense biofilms were observed in animals infected with NTHi 86-028NP licD 7 days postinfection, and none of the animals infected with NTHi 86-028NP licD had a visible biofilm by 14 days. Fluorescent antibody staining revealed PCho(+) variants within biofilms, similar to our prior results with tissue culture cells in vitro (S. L. West-Barnette, A. Rockel, and W. E. Swords, Infect. Immun. 74:1828-1836, 2006). Animals coinfected with equal proportions of both strains had equal persistence of each strain and somewhat greater severity of disease. We thus conclude that PCho promotes NTHi infection and persistence by reducing the host inflammatory response and by promoting formation of stable biofilm communities.

Passive immunization with monoclonal IgM antibodies against phosphorylcholine reduces accelerated vein graft atherosclerosis in apolipoprotein E-null mice

Phosphorylcholine (PC) headgroup is one of the neoantigens exposed by LDL oxidation that can elicit an immune response. Active immunization with Streptococcus pneumoniae, which bears PC on its cell wall, reduced atherosclerosis in hypercholesterolemic mice and this effect was attributed to an immune response to PC. In this study we tested the hypothesis that passive immunization with a monoclonal anti-PC IgM antibody can be athero-protective in a murine model of native aortic and vein graft atherosclerosis. Inferior vena cava from 16-week-old donor male apoE-null mice was grafted into right carotid artery of age-matched male recipient apoE-null mice. Anti-PC IgM titers were evaluated before and 4 weeks after surgery. For the immunization protocol, a separate group of mice received weekly intraperitoneal injection of monoclonal anti-PC IgM (400 microg) for 4 weeks, starting the day of surgery. Controls received PBS or pooled polyclonal IgM. Anti-PC IgM titres significantly increased at 4 weeks following surgery. Passive immunization with anti-PC IgM reduced vein graft plaque size and neointimal thickness resulting in a larger luminal area; in addition immunization reduced the inflammatory cell content of the plaques. There was no significant effect on the established native aortic atherosclerotic lesions. Immunization did not affect circulating cholesterol levels. Taken together our data suggest that passive immunization with anti-PC IgM significantly reduces vein graft lesion size with less inflammatory phenotype without affecting cholesterol levels, indicating an athero-protective immune response to PC. Lack of effect on established native aortic lesions may have been due to short duration of therapy and/or reduced efficacy in established lesions as compared to evolving lesions of vein graft atherosclerosis.

Investigation of strategies with potential for producing a phosphorylcholine-free version of the filarial nematode immunomodulator, ES-62

Phosphorylcholine (PC) is found attached to N-type glycans of proteins secreted by filarial nematodes, where it appears to act as an immunomodulator. Based on information on the structure and biosynthesis of the PC-glycan of a major secreted protein, ES-62, strategies were designed with potential for preparing PC-free material to better understand the importance of PC in filarial nematode immunomodulation. The strategies involve either enzymatic removal of PC or inhibition of its attachment during ES-62 synthesis. No method tested was found to be 100% effective although approximately 70% removal was obtained by culturing worms in Et18OCH3. Reasons for failure to obtain complete absence of PC moieties are discussed in relation to the structure and synthesis of PC-glycans and in addition PC-glycan biosynthesis is briefly commented on as a target for chemotherapy.

Antibody responses to Ascaris-derived proteins and glycolipids: the role of phosphorylcholine

In addition to proteins, glycolipids can be targets of antibody responses and contribute to host-pathogen interaction. Following the structural analysis of Ascaris lumbricoides-derived glycolipids, the antibody responses of a group of children with no, light and heavy infections were analysed. The role of the phosphorylcholine moiety, present on Ascaris glycoproteins and glycolipids, in antibody reactivity of these infected individuals was determined. Children carrying heavy infections showed highest IgG reactivity to glycolipids compared to lightly or non-infected children. Substantial IgG antibody reactivity to both (glyco)proteins and glycolipids was found to be directed to the phosphorylcholine moiety as determined by either removal of this group or a competition assay. This was most pronounced for glycolipids, where removal of the phosphorylcholine moieties by hydrofluoric acid treatment abrogated IgG antibody reactivity. Measurement of IgG4 and IgE isotypes showed no IgG4 reactivity to Ascaris glycolipids, but raised IgE responses were detected in subjects with light or no Ascaris infections, suggesting that IgE responses to glycolipids may play a role in controlling parasite burden. Differences found in antibody profiles to glycolipids and (glyco)proteins, indicate that these different classes of compounds may have distinct roles in shaping of and interacting with humoral immune responses.

The endogenous immune response modulates the course of IgA-immune complex mediated nephropathy

In animal models of IgA nephropathy, the inevitable endogenous immune response to passively administered antigens alone or in complex with specific IgA mask the exact role each might play in pathogenesis. To delineate the role the immune response might play, we have developed a passive model with exclusive IgA-immune complex-mediated nephropathy in B-cell-deficient (BCD) mice. Glomerular IgA immune deposits were induced by administration of purified IgA antiphosphorylcholine and the specific pneumococcal C-polysaccharide (PnC) antigen daily for 2 weeks into BCD and wild-type (WT) mice. In BCD mice IgA+PnC deposits induced severe glomerular injury and renal dysfunction. In contrast, WT mice developed intense glomerular IgG and IgM and C3 co-deposits of the IgA+PnC with significantly less renal injury. Cytofluorometric analysis revealed that PnC induced in BCD, but not in WT, a rapid and dramatic increase in number of activated CD3(+)/CD69(+) T-cell population. The nuclear factor-kappa B (NF-kappaB) transcription factor was activated early and progressively increased in response to glomerular IgA+PnC deposits. These results suggest that nephritogenic IgA+PnC immune deposits induce glomerular and renal dysfunction through activation of the NF-kappaB. This inflammatory pathway is modulated by the endogenous cellular and antibody response to the antigen affecting the course of IgA nephropathy progression.

Capsule does not block antibody binding to PspA, a surface virulence protein of Streptococcus pneumoniae

Of the proteins on the surface of Streptococcus pneumoniae, one of those best able to elicit protection against pneumococcal infection is pneumococcal surface protein A (PspA). Although this protein is attached to the membrane molecule, lipoteichoic acid, which is well beneath the capsule, PspA's ability to inhibit complement deposition and killing by apolactoferrin, suggests that it must have surface exposure. This study provides quantitative data showing that the capsular polysaccharide on types 2 and 3 pneumococci provides little or no masking ability of antibodies to bind PspA. Capsule was even observed to enhance, rather than inhibit the binding of two protective monoclonal antibodies to their epitopes on cell surface PspA. These results with antibodies to PspA are in contrast to binding by antibodies to the phosphocholine (PC) epitope of the lipoteichoic and teichoic acids. The binding of antibody to PC was largely, but not completely, blocked by capsular polysaccharide.

Induction of autoimmunity by immunization with hapten-modified hen egg lysozyme in hen egg lysozyme-transgenic mice

To understand the mechanism of autoimmunity induction, hen egg lysozyme (HEL)-transgenic (Tg) C57BL/6 (B6) mice were immunized with HEL or phosphorylcholine-conjugated HEL (PC-HEL). Repeated immunization of HEL-Tg mice with native HEL failed to induce the antibody response against HEL. However, immunization with PC-HEL generated a significant anti-HEL antibody response. Immunization of the Tg mice with dominant (HEL(74-88)) or cryptic (HEL(47-61)) T-cell epitope peptide stimulated the corresponding T-cell response and similarly yielded the anti-HEL antibody response. Predominance of immunoglobulin G1 (IgG1) anti-HEL antibody response in the HEL-Tg mice and preferential IL-4 production by HEL-specific T cells suggested the dependency of the antibody response to the presence of T helper 2. HEL-Tg mice received HEL-primed B6 T cells, but not HEL-primed Tg T cells, were able to generate anti-HEL antibody response following PC-HEL immunization. The pattern and the level of epitope peptides generated by splenic antigen-presenting cells indicated that PC-HEL results in much more efficient processing as compared to HEL. These results strongly suggest that the enhancement of antigen processing by hapten (PC) conjugation to the antigen facilitates more efficient stimulation of T cells reactive to self antigen, HEL in HEL-Tg mice resulting in the production of anti-self HEL antibody.

Dissecting Ascaris glycosphingolipids for immunomodulatory moieties - the use of synthetic structural glycosphingolipid analogues

We have previously shown glycosphingolipids of Ascaris suum to have phosphorylcholine (PC) and non-PC immunomodulatory moieties. In the present study we further investigated the nature of the immunomodulatory moieties by employing three synthetic glycosphingolipids each possessing features of the original molecule to examine effects on macrophage and dendritic cell (DC) cytokine production and surface co-stimulatory molecule expression. Compound 2, which lacked PC but contained ceramide, had no effect on either macrophages or DCs. Surprisingly however, Compound 1, which contained PC and hence arguably most resembled the native material, had, with the exception of a small increase in surface antigen expression, no immunomodulatory properties. Conversely, Compound 3, which contained PC but was otherwise least like the native molecule, demonstrated a number of effects on both macrophages and DCs, including induction of Th-1/pro-inflammatory cytokines, inhibition of such cytokines induced by IFN-gamma/LPS and increased expression of co-stimulatory molecules. Taken together these results indicate: (i) that although PC is an immunomodulatory component of the native molecule other structural feature are necessary to allow it to act; (ii) that carbohydrate rather than ceramide is likely to represent a non-PC immunomodulatory moiety; and (iii) that synthetic PC-containing molecules have the potential to act as immunomodulatory drugs.

Antibodies of IgM subclass to phosphorylcholine and oxidized LDL are protective factors for atherosclerosis in patients with hypertension

OBJECTIVE

To determine the importance of antibodies against phosphorylcholine (PC) and oxidized low density lipoprotein (OxLDL) for development of atherosclerosis.

METHODS AND RESULTS

Two hundred and twenty six individuals with established hypertension (diastolic pressure > 95mmHg) were from European Lacidipine Study on Atherosclerosis. Antibodies of IgG and IgM subclass were tested by ELISA against PC (aPC), cupper-oxidized (ox)- or malondialdehyde (MDA)-modified LDL. High-sensitivity C-reactive protein was measured by nephelometry. As a surrogate measure of atherosclerosis, we used the mean of the maximum intima-media thicknesses (IMT) in the far walls of common carotids and bifurcations was determined by ultrasonography at the time of enrolment, and 4 years following enrolment. aPC could be competed out by PC and OxLDL, while cardiolipin (CL) and beta2-glycoprotein I (beta2GPI) were less effective and phosphatidylserine (PS) not at all. Increases in IMT at follow-up were less common in subjects which at the time of enrolment had high IgM aPC (both 75th and 90th; odds ratios: 0.46; CI: 0.25-0.85; 0.36; CI: 0.15-0.87) and high IgM aOxLDL and aMDA-LDL (90th; odds ratios 0.27; p = 0.01; CI: 0.11-0.69 and 0.27; p = 0.01; CI: 0.11-0.69). CRP was unrelated to IMT-changes. The relationship between IgM aPC, aOxLDL and aMDA-LDL and changes in IMT was independent of age, treatment with atenolol or lacidipine, smoking and lipids. Women had higher levels of IgM antibodies tested (p < 0.05).

CONCLUSIONS

High levels of IgM-antibodies against PC and OxLDL predict a favourable outcome in the development of carotid atherosclerosis in hypertensive subjects. Whether these antibodies could be used therapeutically deserves further study.

Human resting CD16-, CD16+ and IL-2-, IL-12-, IL-15- or IFN-alpha-activated natural killer cells differentially respond to sphingosylphosphorylcholine, lysophosphatidylcholine and platelet-activating factor

The phosphorylcholine-containing lipid lysophosphatidylcholine (LPC) is abundant in the bloodstream, whereas sphingosylphosphorylcholine (SPC) and platelet-activating factor (PAF) highly accumulate at inflamed sites. Utilizing RT-PCR, flow cytometry and immunoblot analyses, we show for the first time that ovarian cancer G protein-coupled receptor 1, the receptor for SPC, is expressed in IL-2-, IL-12- and IL-15-activated but not in resting CD16-, resting CD16+ or IFN-alpha-activated NK cells. Similarly, G2 accumulation and PAF receptor are variably expressed in these subsets of NK cells. SPC, LPC and PAF differentially induce the chemotaxis of resting and activated NK cells. In the chemotaxis assay, it is observed that resting CD16-CD56bright and CD16+CD56dim cells predominantly respond to LPC, whereas activated NK cells, regardless of the sort of stimulus, robustly respond to PAF. SPC is also a potent chemoattractant for IL-2-, IL-12- and IL-15- but not for IFN-alpha-activated NK cells. Further analysis shows that, depending on the cytokine pattern of NK cell activation, phosphorylcholine-containing lipids differentially affect IFN-gamma secretion by these cells. Our results provide one possible explanation for the tissue compartmentation of NK cells and their ability to secrete IFN-gamma. Furthermore, these results may provide novel information regarding NK cell regulation during inflammation.

Specific ICAM-3 grabbing nonintegrin-related 1 (SIGNR1) expressed by marginal zone macrophages is essential for defense against pulmonaryStreptococcuspneumoniaeinfection

The dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) homolog, SIGN-related 1 (SIGNR1) is a pathogen receptor expressed by splenic marginal zone and peritoneal macrophages, and is essential for clearance of Streptococcus pneumoniae by phagocytosis after intraperitoneal infection. Here, we identified an important in vivo function for SIGNR1 in S. pneumonia infection induced via its natural entrance route. Upon intranasal infection with S. pneumoniae, SIGNR1-deficient mice did not clear bacteria from lung and blood, and displayed severely enhanced inflammatory parameters compared to the wild-type mice. However, SIGNR1 is not expressed by alveolar macrophages, suggesting that another mechanism than a decrease in phagocytosis is responsible for this difference. Natural anti-phosphorylcholine IgM produced by marginal zone B cells is essential for protection against infection with S. pneumoniae. Strikingly, during infection, SIGNR1-deficient mice failed to produce a rapid anti-phosphorylcholine IgM response. Marginal zone macrophages have been suggested to capture antigens for presentation to marginal zone B cells. We demonstrate that marginal zone macrophages from SIGNR1-deficient mice in contrast to wild-type mice are not able to capture pneumococci from blood, suggesting that SIGNR1 on marginal zone macrophages captures S. pneumoniae for antigen presentation to and activation of marginal zone B cells, resulting in an anti-phosphorylcholine IgM response.

Signalling mechanisms underlying subversion of the immune response by the filarial nematode secreted product ES-62

Secretion of immunomodulatory molecules is a key strategy employed by pathogens to enable their survival in host organisms. For example, arthropod-transmitted filarial nematodes, which achieve longevity within the infected host by suppressing and modulating the host immune response, produce excretory-secretory (ES) products that have been demonstrated to possess immunomodulatory properties. In this review we discuss the immunomodulatory effects of the phosphorylcholine-containing filarial nematode-secreted glycoprotein ES-62 and describe the intracellular signal transduction pathways it targets to achieve these effects.

The polysaccharide antibody response after Streptococcus pneumoniae vaccination is differentially enhanced or suppressed by 3,4-dichloropropionanilide and 2,4-dichlorophenoxyacetic acid

Propanil (3,4-dichloropropionanilide) and 2,4-D (2,4-dichlorophenoxyacetic acid) are commonly used herbicides that have toxic effects on the immune system. The present study determined the effect of exposure to these chemicals on the immune response to a bacterial vaccine. The antibody responses to the T-independent type 2 antigen, phosphorylcholine (PC) and the T-dependent antigen, pneumococcal surface protein A (PspA) were characterized in C57BL/6 mice after heat-killed Streptococcus pneumoniae (HKSP) immunization and single or mixture herbicide exposure. Propanil exposure significantly increased the number of PC-specific IgM, IgG2b, and IgG3 antibody-secreting B cells (ASC) in the spleen 4-6-fold over control animals in a dose-dependent manner. However, the number of ASC in the bone marrow and serum titers were comparable in control and propanil-treated mice. In contrast, 2,4-D exposure decreased the number of PC-specific IgM and IgG bone marrow ASC 2-3-fold from control animals. The decrease in bone marrow ASC in 2,4-D-treated mice corresponded to a 3-4-fold decrease in PC-specific IgM, IgG2b, and IgG3 serum titers compared to control mice. The number of ASC in the spleens of 2,4-D-treated mice was, however, comparable to control mice. The antibody response to PspA was not affected by any of the treatments. There were no mixture interactions between the two herbicides in any of the responses measured. These results characterize the primary PC-specific antibody response in the bone marrow, spleen, and serum after HKSP vaccination and herbicide exposure. The differential effects of propanil and 2,4-D on the antibody response to a bacterial vaccine demonstrate the potential of chemical exposure to augment or suppress immune responses to vaccines and infectious diseases.

A monoclonal antibody that conveys in vitro killing and partial protection in experimental syphilis binds a phosphorylcholine surface epitope of Treponema pallidum

Immunization with purified Treponema pallidum outer membrane vesicles (OMV) has previously resulted in high-titer complement-dependent serum bactericidal activity. In this study, OMV immunization resulted in the isolation of a monoclonal antibody, M131, with complement-dependent killing activity. Passive immunization of rabbits with M131 administered intravenously conferred significant immunity demonstrated by the failure of syphilitic lesions to appear at 29% of intradermal challenge sites (7/24) and a mean delay of approximately 8 days to lesion appearance at the remaining sites (17/24). M131 not only bound to OMV and to the surfaces of intact motile T. pallidum cells but also bound to organisms whose outer membranes were removed, indicating both surface and subsurface locations for the killing target. This target was determined to be a T. pallidum lipid. Lipid extracted from T. pallidum and made into liposomes bound M131. Reverse-phase high-pressure liquid chromatography separation and fraction collection mass spectrometry (LC-MS+) of T. pallidum lipid showed that the target of M131 was phosphorylcholine. M131 binding required both liposome formation and a critical concentration of phospholipid containing phosphorylcholine, suggesting that the epitope has both a conformational and a compositional requirement. M131 did not react with red blood cells, which have phosphorylcholine-containing lipids in their exterior membrane leaflets, or with Venereal Disease Research Laboratory antigen that also contains phosphorylcholine, further indicating the specificity of M131. This is the first physical demonstration of an antigen on the T. pallidum surface and indication that such a surface antigen can be a target of immunity.

Interleukin-8 response in cells from the human urinary tract induced by lipopolysaccharides of Proteus mirabilis O3 and O18

PURPOSE

Proteus mirabilis is a common pathogen associated mainly with complicated urinary tract infections and sometimes with septicemia. There is great serological diversity of the microorganism. While P. mirabilis O3 is commonly found in patients with infections, the serotype O18 rarely occurs. The O18 lipopolysaccharide contains a phosphocholine substitute, which makes it unique among Proteus strains. To explain different clinical significance of the strains we evaluated the biological activity of the lipopolysaccharides of P. mirabilis O3 and O18, as measured by interleukin-8 (IL-8) production.

MATERIALS AND METHODS

Three cell lines were used, namely uroepithelial cells, renal epithelial cells and monocytes. IL-8 production was determined on the protein and mRNA levels using enzyme-linked immunosorbent assay and real-time polymerase chain reaction, respectively, and CD14 expression on the cell surface was studied using flow cytometry.

RESULTS

Uroepithelial cells and monocytes reacted to lipopolysaccharides by higher IL-8 production compared with renal epithelial cells. Cell specific IL-8 response corresponded to the cell expression of CD14. Renal epithelial cells produced more IL-8 after stimulation with the phosphocholine rich lipopolysaccharide O18, although adding phosphocholine alone did not induce or increase IL-8 production.

CONCLUSIONS

Our data suggest that different cells within the human urinary tract have different roles during urinary tract infection. The biological activity and pathogenicity of P. mirabilis lipopolysaccharides might be determined by their specific chemical structure.

Induction of immune response toStreptococcus pneumoniaeby administration of oral viridans streptococci via phosphorylcholine determinant

Expression of the phosphorylcholine (PC) epitope was examined in 48 viridans streptococcal strains, including Streptococcus pneumoniae R36a as the positive control, and their immunogenicity to induce an S. pneumoniae-cross-reactive response was evaluated in mice. Thirteen strains were found to express the PC epitope, while no obvious association was found between the taxonomic categories and PC expression. Serum antibody responses to S. pneumoniae cells were induced in mice by intraperitoneal injection of the PC-positive, but not PC-negative, strains. The cross-reactive antibodies induced by non-pneumococcal oral streptococci were readily inhibited by free hapten PC. IgM was the sole isotype of the anti-pneumococcal and anti-PC antibodies, and the phenomenon of immunological memory was not observed. Since the anti-PC antibody is critically important for resistance against pneumococcal infection in mice, the present results indicate the possibility that PC-expressing oral commensal bacteria have a significant influence on the hosts' responsiveness to S. pneumoniae.

In vivo exposure of murine dendritic cell and macrophage bone marrow progenitors to the phosphorylcholine-containing filarial nematode glycoprotein ES-62 polarizes their differentiation to an anti-inflammatory phenotype

We have previously shown in an in vitro study that the filarial nematode phosphorylcholine (PC)-containing glycoprotein ES-62 promotes a murine dendritic cell (DC) phenotype that induces T helper type 2 (Th2) responses. We now show that, in addition to directly priming Th2 responses, ES-62 can act to dampen down the pro-inflammatory DC responses elicited by lipopolysaccharide. Furthermore, we also demonstrate that murine DCs and macrophages derived ex vivo from bone marrow cells exposed in vivo to ES-62 by release from osmotic pumps are hyporesponsive to subsequent stimulation with lipopolysaccharide. These effects can be largely mimicked by exposure to the PC moiety of ES-62 conjugated to an irrelevant protein. The data we provide are, as far as we aware, the first to show that a defined pathogen product can modulate the developmental pathway of bone marrow cells of the immune system in vivo. Such a finding could have important implications for the use of pathogen products or their derivatives for immunotherapy.

Innate-like B cells

Numerous studies in several species have shown that certain subsets of T and B lymphocytes express antigen receptors which are either semi-invariant, or germline encoded, and often autoreactive. In the case of B cells they appear to use a distinct immune recognition strategy during developmental selection and functional activation. These B cells respond to foreign antigens, and have the ability to protect against a variety of infections; however, they can also react with self or neoself antigens. They appear to use the latter as positively selecting ligands facilitating their entry into and maintenance in a functional repertoire, as well as providing cues for positioning themselves in strategic microenvironmental niches in the immune system and at interfaces with the environment. These innate-like B cell subsets form a bridge between the rapidly occurring innate immune responses, and the slower acting primary, T cell-dependent, adaptive antibody response by providing a rapid T cell-independent antibody response.