APOL1 variant-expressing endothelial cells exhibit autophagic dysfunction and mitochondrial stress

Polymorphisms in the Apolipoprotein L1 (APOL1) gene are common in ancestrally African populations, and associate with kidney injury and cardiovascular disease. These risk variants (RV) provide an advantage in resisting Trypanosoma brucei, the causal agent of African trypanosomiasis, and are largely absent from non-African genomes. Clinical associations between the APOL1 high risk genotype (HRG) and disease are stronger in those with comorbid infectious or immune disease. To understand the interaction between cytokine exposure and APOL1 cytotoxicity, we established human umbilical vein endothelial cell (HUVEC) cultures representing each APOL1 genotype. Untreated HUVECs were compared to IFNɣ-exposed; and APOL1 expression, mitochondrial function, lysosome integrity, and autophagic flux were measured. IFNɣ increased median APOL1 expression across all genotypes 22.1 (8.3 to 29.8) fold (p=0.02). Compared to zero risk variant-carrying HUVECs (0RV), HUVECs carrying 2 risk variant copies (2RV) showed both depressed baseline and maximum mitochondrial oxygen consumption (p<0.01), and impaired mitochondrial networking on MitoTracker assays. These cells also demonstrated a contracted lysosomal compartment, and an accumulation of autophagosomes suggesting a defect in autophagic flux. Upon blocking autophagy with non-selective lysosome inhibitor, hydroxychloroquine, autophagosome accumulation between 0RV HUVECs and untreated 2RV HUVECs was similar, implicating lysosomal dysfunction in the HRG-associated autophagy defect. Compared to 0RV and 2RV HUVECs, HUVECs carrying 1 risk variant copy (1RV) demonstrated intermediate mitochondrial respiration and autophagic flux phenotypes, which were exacerbated with IFNɣ exposure. Taken together, our data reveal that IFNɣ induces APOL1 expression, and that each additional RV associates with mitochondrial dysfunction and autophagy inhibition. IFNɣ amplifies this phenotype even in 1RV HUVECs, representing the first description of APOL1 pathobiology in variant heterozygous cell cultures.

Risk of Toxicity After Initiating Immune Checkpoint Inhibitor Treatment in Patients With Rheumatoid Arthritis

INTRODUCTION

Immune checkpoint inhibitors (ICIs) are increasingly used to treat advanced cancer. Rheumatoid arthritis (RA) is associated with an increased risk of malignancies; however, patients with RA have been excluded from ICI trials. In this study, we evaluated risk of toxicity after initiation of ICI treatment in RA patients.

METHODS

We conducted a single-institution, medical records review analysis to assess the incidence of immune-related adverse events (irAEs) and autoimmune disease (AID) flares among patients with AIDs treated with ICIs from 2011 to 2018. A subgroup analysis for RA patients was performed with frequencies of irAEs and AID flares reported.

RESULTS

Twenty-two patients with RA who were treated with ICI for malignancy were identified. At the time of ICI initiation, 86% had inactive RA disease activity. Immune-related adverse events occurred in 7 (32%) of patients, with 2 (9%) developing grade 3 (i.e., severe) irAEs. Immune checkpoint inhibitors were temporarily discontinued because of irAEs in 5 patients (23%), and permanently in 1 patient. Rheumatoid arthritis flares occurred in 12 patients (55%). Of those, 10 (83%) received oral corticosteroids with an adequate treatment response.

CONCLUSIONS

Our analysis suggests that irAEs following ICI treatment are not increased among RA patients compared with other cancer patients. Heightened RA disease activity during ICI treatment is common, but most adverse events are manageable with oral corticosteroids, and few require permanent ICI discontinuation. A close collaboration between the oncologist and rheumatologist is advisable when considering ICIs in patients with RA.

THU0027 THE ASSOCIATION OF THE RS35677470 DNASE1L3 GENE POLYMORPHISM WITH SLE, RA AND SSC: STRUCTURAL/BIOLOGICAL INSIGHTS

Background:

Genome-wide association studies (GWAS) have identified hundreds of autoimmune diseases-associated loci so far but much of the heritability of these diseases remains unknown. In an attempt to identify potential causal variants, various studies revealed that the missense variant rs35677470 atDNASE1L3is associated with the development of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and systemic sclerosis (SSc), thus exhibiting a pleiotropic effect. Deoxyribonuclease I-like 3 (DNase1L3) is a member of human DNase I family, representing a nuclease that cleaves double-stranded DNA during apoptosis and is involved in the development of autoimmune diseases [1].

Objectives:

To investigate the role of the rs35677470 polymorphism atDNASE1L3gene leading to the R206C mutation in SLE, RA and SSc [2-3] and the mechanism that may affect the loss of function in the protein structure.

Methods:

TheDNASE1L3evolution was investigated to define conservation elements in the protein sequence using, BLASTP extended searches [4], TCOFFEE [5] multiple sequence alignments, and MEGAX [6] for phylogenetics analysis. Three-dimensional (3D) homology modeling was used to localize the polymorphism under study. The mutant was constructed by molecular modeling using the structures of homologous DNAses (PDB entries 1atn, 4awn, 3d3w; [7-9]). Molecular mechanics/dynamics studies were applied to validate structural/functional changes caused by the R206C substitution. All figures depicting 3D models were generated using the PyMOL molecular-graphics system V.2.2 (Schrodinger, LLC).

Results:

The evolutionary analysis shows heavily conserved sequence elements among species indicating structural/functional importance. Structural analysis revealed that the rs35677470 SNP codes for a nonconservative amino acid variation, R206C, disrupts the conserved electrostatic network holding protein secondary structure elements to place. Specifically, the R206 to E170 interaction, part of a salt bridge network stabilizing two a-helices, is being interrupted, thereby affecting the molecular architecture (Fig. 1). Indeed, previous studies on the effect of this SNP in Caucasian populations resulting in a lower level of DNAse1L3 activity are consistent with this observation [10].

Figure 1.

Ribbon representation of the DNAse1L3 homology model showing the position of the stabilizing salt bridge network (E170- R206, R208- D219). Insert figure shows the R206C mutation. Positively charged R (in blue), negatively charged D,E (in red) and C (in yellow) are shown. Distances are in Angstroms.

Conclusion:

This study represents a comprehensive evaluation of the shared autoimmune loci ofDNASE1L3(rs35677470), reported to produce an inactive form of DNaseIL3 [10]. The structural analysis, explains the potential role of the produced mutation by modifying the placement of structural elements and consequently introducing disorder in the protein folding and affecting biological function. Altogether, this study contributes to the delineation of the genetic architecture of SLE, RA and SSc.

References:

[1]Sisirak V et al (2016). Cell 166:88–101

[2]Westra HJ et al (2018). Nat Genet. 50:1366-74

[3]Acosta-Herrera M et al. (2018). Ann Rheum Dis. 78:311-19

[4]Altschul SF et al (1997) Nucleic Acids Res. 25:3389-402.

[5]Notredame et al (2000) JMB, 302:205-17

[6]Kumar S et al (2018) Mol. Biol. Evol. 35:1547-9

[7]Kabsch W et al (1990) Nature 347: 37-44

[8]Parciegla et al (2012) Biochemistry 51: 10250

[9]Sasaki K et al (1993) Acta Cryst., A 49: 111-2

[10]Ueki et al (2009) Clinica Chim. Acta 407:20–4

Disclosure of Interests:

None declared

THU0017 ATTEMPTS TO LINK EXONIC GENE POLYMORPHISMS TO SYSTEMIC LUPUS ERYTHEMATOSUS (SLE)-ASSOCIATED PROTEIN MODIFIED FUNCTIONALITY: A STRUCTURAL BIOLOGY APPROACH

Background:

Gene association studies and genome wide association studies (GWAS) have played a primary role in depicting genetic contributions to systemic lupus erythematosus (SLE) development, while accommodating the exonic polymorphisms on the protein structure level, when available, enhances our understanding of protein function modification or depletion. Linking human genetics with therapeutic targets requires the biological function of the causal gene and variant to be known.

Objectives:

To investigate recently identified SLE-associated functional gene polymorphisms, such asPARP1,ITGAM, TNFAIP3, NCF1, PON1, IFIH1, SH2B3andTYK2[1-4] by correlation to protein structure and function.

Methods:

Three-dimensional (3D) homology modeling and molecular mechanics/dynamics studies were applied for the localization of the polymorphisms under study on the respective proteins. The mutants were constructed using molecular modeling with the program Maestro (Schrodinger, LLC), which was also used to analyze the conformational changes caused by the mutation. All figures depicting 3D models were created using the molecular graphics program PyMOL V.2.2 [5].

Results:

Modeling revealed that rs1136410 SNP encodes the less common polymorphism Val762Ala onPARP1that reduces enzymatic activity of Poly(ADP-ribose) polymerase 1 (Figure 1),ITGAMpolymorphism rs1143679 (Arg77His) on Integrin alpha M, component of the macrophage-1 antigen complex affects protein surface recognition,TNFAIP3rs2230926 polymorphism encodes Cys instead of Phe at residue 127 of the ubiquitin editing A20 protein, while rs201802880 polymorphism of the neutrophil cytosolic factor 1 (NCF1) gene modifies the function of the cytosolic subunit of neutrophil NADPH oxidase with the mutation Arg90His.PON1is involved in the oxidative stress process that cause tissue damage observed in SLE and anti-phospholipid syndrome (APS). ThePON1Gln192Arg mutation (rs662 SNP) affects shape and recognition of the ligand recognition site as part of the evolutionary process, whileIFIH1(rs35667974) helicase C domain1 mutant I923V is located on an essential RNA beta loop interacting directly with the nucleic acid (Figure 2). Finally, the rs3184504 SNP ofSH2B3gene generates mutant Arg262Trp on SH2 adapter protein 3, acting as a signaling pathway involved in autoimmune disorders, while inTYK2 gene, one of the Janus kinases, the rs35018800 producing mutant Ala928Val modifies the ADP binding site.

Figure 1.

Details of the Val762 interaction where V762A mutation occurs in PARP1protein.

Figure 2.

Nucleic acid interacting IFIH1 helicase beta-loop where I923V mutation occurs (in purple).

Conclusion:

Based on several examples, we have tried to define a rational link from SLE-associated gene polymorphisms to structure and to modified function, including metagenomic analysis of SNPs, protein crystallography, protein molecular modeling, molecular mechanics and dynamics. Locating, shaping and understanding the target protein interaction interface plays a decisive role in most cases and provides clues for further pharmacological or medical actions [6].

References:

[1]Hur JW et al (2006). Rheumatology 45:711-7

[2]Maiti AK et al (2014). Hum Mol Genet 23:4161-76

[3]Shimane K et al (2010). Arthritis Rheum. 62:574-9

[4]Linge P et al (2019). Ann Rheum Dis. 2019 Nov 8. pii: annrheumdis-2019-215820

[5]Schrödinger LLC: The PyMOL Molecular Graphics System 2016 version 2.2. Available from: pymol.org/2/support.html

[6]Plenge RM et al (2013). Nat Rev Drug Discov 12:581–94

Disclosure of Interests:

None declared

ID: 133: SINGLE CELL GENE EXPRESSION IN CLASSICAL MONOCYTES CORRELATES WITH TREATMENT RESPONSE TO TNF-ALPHA INHIBITION IN RHEUMATOID ARTHRITIS

Background

In management of rheumatoid arthritis (RA), initiating effective treatment as soon as possible within the so-called therapeutic “window of opportunity” is the strategy, and disease remission is a primary goal. Recent work from our group demonstrated that pre-treatment serum type I IFN-β/α activity ratio>1.3 can predict non-response to anti-TNF-alpha therapy in RA patients. The cellular mechanisms that underlie the IFN-β/α activity ratio that predicts response are not known. Effects of IFN on single immune cells and uncommon cell populations may be masked in whole blood or mixed cell populations.

Methods

To better understand the underpinnings of the pre-treatment IFN-β/α activity ratio, we used single cell expression analysis to investigate whether monocyte gene expression differs significantly between RA patients according to their pre-TNF-α inhibitor serum IFN-β/α activity ratio. Single classical (CL) and single non-classical (NCL) blood-derived monocytes were isolated from 15 seropositive RA subjects prior to biologic therapy. Total serum type I IFN, IFN-α, and IFN-β activity were measured using a functional reporter cell assay. Subjects were grouped by pre-TNF-α inhibitor serum IFN-β/α activity ratio into two groups, IFN-β/α>1.3 (n=6) and IFN-β/α<1.3 (n=9). Comparisons between groups were by Mann-Whitney. Hierarchical clustering of 87 target genes was done to determine if there were functional gene expression differences between groups.

Results

Hierarchical clustering revealed striking differences of expression of gene sets in CL monocytes between patients with IFN-β/α<1.3 and IFN-β/α>1.3, the groups which correspond to response/non-response to anti-TNF-α agents. This same clustering was not observed in NCL monocytes, and the differentiation between anti-TNF-α response patient groups was lost when hierarchical clustering was done on total monocytes (CL and NCL). Two major gene sets which differentiated subjects with IFN-β/α>1.3 (non-response to anti-TNF-α group) in CL monocytes included TLR and IFN pathway genes, cell surface markers and cytokines as follows: cluster 1 (TLR2, CD16, JAK1, IFI27, IL1A, and MAVS) and cluster 2 (GMCSF, TLR7, STAT2, ILT7, MYD88).

Conclusion

These within-cell expression patterns demonstrate biological differences in CL monocytes of RA patients with an IFN-β/α>1.3, the ratio of type I IFNs previously found to be predictive of non-response to anti-TNF-α therapy. Differentiation by gene expression among the response/non-response patient groups is lost when comparing gene expression in single NCL monocytes and single mixed population monocytes (CL and NCL), suggesting that further study of CL monocytes will likely illuminate molecular differences that determine treatment response to TNF-α inhibition in RA. This work will help to develop a more individualized approach to therapy in RA based upon the underlying biology of disease in a given patient.

Identification of the major regenerative III protein (RegIII) in the porcine intestinal mucosa as RegIIIγ, not RegIIIα

During the last years, an antimicrobial protein from the RegIII family has been consistently identified as one of the main up-regulated mRNA transcripts in the pig small intestinal mucosa during different infections such as enterotoxigenic Escherichia coli (ETEC). This transcript has been mainly referred to in the literature as pancreatitis-associated protein (PAP/RegIIIα). However, the identity of this transcript has not been confirmed, and no evidence of its expression at the protein level is available in the literature, because the absence of a specific antibody. In this study, we first unequivocally identified the PAP/RegIII family protein mainly expressed in ETEC infected pig intestine as RegIIIγ by 2D-DIGE and MALDI-TOF/TOF. This shows that the pig differs from species like human and mice in that RegIIIγ (and not RegIIIα) might be the major RegIII isotype during intestinal infection. Immunoblotting analysis with a specifically generated polyclonal rabbit antibody revealed that pig RegIIIγ is expressed throughout the intestinal tract, but most abundantly in the ileum. Although a higher abundance of mRNA was paralleled by higher protein abundance, a lack of linear relationship was found between RegIIIγ mRNA and protein abundances in the jejunal mucosa, the latter most pronounced in the case of natural infection. This may be related to the secretory nature of RegIIIγ. This would mean that the antimicrobial protein RegIIIγ is a good candidate as a non-invasive faecal intestinal health biomarker in swine.

Relationship between wheat characteristics and nutrient digestibility in broilers: comparison between total collection and marker (titanium dioxide) technique

Three wheat cultivars (Orpheus, Rustic, and Viscount) were used to formulate 3 test feeds (62.4% wheat) in a broiler digestibility trial. The diets were fed to male Ross 308 broiler chickens. The wheat cultivars mainly differed in their amount of non-starch polysaccharides ( NSP: ). The cultivar Orpheus was chosen to represent a high amount of NSP (102 g/kg DM), whereas the cultivars Rustic and Viscount represented low amounts of NSP (83.4 g/kg DM and 73.9 g/kg DM, respectively). Furthermore, the cultivars Orpheus and Viscount were feed quality wheat, whereas Rustic was a milling quality wheat. Nutrient digestibilities and AMEn contents of the diets were measured from 18 to 22-days-old by total excreta collection, or with the use of the indigestible marker titanium dioxide. In addition, the ileal viscosity was measured when the broilers were 25-days-old. Wheat cultivar affected N retention, DM digestibility, and AMEn. In general, the feed formulated with the high NSP wheat cultivar Orpheus resulted in the least favorable nutrient digestibilities and AMEn, whereas the results were better when the feed was formulated with the low NSP cultivars Viscount and Rustic. Feeding the Rustic cultivar caused the highest intestinal viscosity, although this was not reflected in the animal responses. Nutrient digestibilities and AMEn content of the diets were lower when calculated with the titanium dioxide marker than with the total excreta collection procedure. Moreover, the P-values of the effect of wheat cultivar on DM digestibility, N retention, crude fat digestibility and AMEn were lower with the use of the titanium dioxide marker. It can be concluded that wheat cultivar affected nutrient digestibility and AMEn, and that the observed differences were related to the amount of NSP. Furthermore, both the titanium dioxide marker and the total excreta collection methods showed the same trends despite the different values obtained. The titanium dioxide marker method was the simplest to use and produced valid results.

Altered soluble mediator levels and systemic lupus erythematosus-specific Connective Tissue Disease Screening Questionnaire (CSQ) scores differentiate unaffected relatives of lupus patients from healthy individuals with no family history of SLE (CCR4P.214)

Identifying populations at risk of SLE who remain unaffected would provide insights for potential disease prevention. Using a unique resource of SLE patient family members, first degree relatives (FDRs) of SLE patients (n = 154) with plasma samples available from previous genetic studies and who remained unaffected at follow-up evaluation (mean time = 6.8 years) were matched to healthy individuals unrelated to SLE patients (Controls). FDRs and Controls provided clinical and demographic information, and completed screening questionairres at baseline (BL) and follow-up (FU). BL and FU plasma samples were assessed for autoantibody production and soluble mediators. FDRs had significantly higher BL and FU CSQ scores (p&lt;0.0001), but no difference in the number of positive autoantibodies compared to Controls. FDRs had significant (p &lt; 0.01) increases in 38 (of 52) soluble mediators at BL and FU, including IFN-associated chemokines, TNFR ligands, and regulatory mediators (p&lt;0.002). Levels of MIP-1α (p=0.008), MIG (p=0.019), GROα (p=0.001), ICAM-1 (p=0.007), and VEGF (p=0.004), along with CSQ scores (p=0.010), best distinguished FDRs from Controls in logistic regression models. These alterations are present despite lack of progression to classified SLE, suggesting that multiple perturbations in immune-mediated inflammatory processes present in FDRs of SLE patients may be offset by inhibitory factors.

Single cell gene expression in lupus patient monocytes reveals a differential impact of interferon signaling between monocyte subtypes (TECH2P.920)

Background/Purpose Interferon (IFN) gene expression signatures have been observed in whole blood and mixed immune cell populations in systemic lupus erythematosus (SLE), but the significance of this IFN signaling in immune cell subsets is not well understood. We examined gene expression in individual SLE patient monocytes to explore the impact of increased IFN-induced transcription in single cells. Methods CD14++CD16- classical monocytes and CD14dimCD16+ non classical monocytes from SLE patients were purified by magnetic separation. Single cells were isolated, and gene expression in each individual cell was examined by rtPCR. Results Monocytes from the same SLE patient blood sample demonstrated varying levels of IFN-induced gene expression. In classical monocytes, high IFN score correlated with CD32a, IL1B, and IL8 expression. In non-classical monocytes, high IFN score was correlated with a larger number of inflammatory mediators, including cytokines such as IL12, IL23, and IL15; the immune receptors CD36, CD32a, CD80, and TLR7; and inflammatory signaling genes such as RELA, STAT2, IRAK1, IRAK4, and MyD88. Conclusion We observed striking diversity in the IFN responses of individual monocytes, demonstrating that IFN signaling has distinct effects upon classical and non-classical monocytes. Single cell studies can reveal effects of IFN on single immune cells and uncommon populations such as non-classical monocytes, which would be masked in whole blood or mixed cell populations.

Dysregulation of type II interferon associated mediators precedes autoantibody accumulation and type I interferon elevation and predicts transition to systemic lupus erythematosus classification (BA3P.109)

Autoantibodies and interferon (IFN) are associated with clinical illness in systemic lupus erythematosus (SLE), but how these factors influence autoimmune disease development is unknown. This study evaluates the timing and changes in SLE-linked autoantibody specificities, serum IFN-α activity, and IFN-associated soluble mediator levels in the years preceding SLE classification. Serial sera from 55 SLE cases spanning pre- and post-SLE classification (average time = 4.3 years) and matched healthy controls (HC) were obtained from the Department of Defense Serum Repository. Cases with positive serum IFN-α activity had more SLE-linked autoantibody specificities (p&lt;0.05). Growth curve modeling and path analysis corroborated that most autoantibody specificities precede IFN-α activity, and IFN-γ and IP-10 were elevated prior to or concurrent with autoantibody positivity (p&lt;0.01). The number of autoantibody specificities and IFN-associated soluble mediators, as well as female gender, predicted increases in IFN-α activity (p&lt;0.04; ANCOVA). IFN-γ and MCP-3 levels, as well as the presence of anti-chromatin and spliceosomal autoantibodies, best predicted transition to SLE with 93% accuracy &gt;4 years before SLE classification (Random Forest). These data indicate that pre-clinical immune system perturbations allow for the accumulation of autoantibodies and subsequent elevation in IFN-α activity immediately preceding clinical symptoms and SLE classification.

Soluble mediators and clinical features predict transition to systemic lupus erythematosus classification in previously unaffected relatives of SLE patients (HUM3P.243)

Healthy relatives of lupus patients have an increased risk of developing SLE, but predictors and mechanisms of disease transition are unknown. Unaffected relatives of SLE patients (n=409) were enrolled in this follow-up study to identify factors associated with transition to SLE. Participants provided detailed demographic and clinical information, including the Connective Tissue Disease Screening Questionnaire (CSQ). Medical records were reviewed for ACR classification criteria. Plasma samples were tested for the presence of autoantibodies and soluble mediators. Forty-five relatives (11%) transitioned to classified SLE during follow-up (mean time = 6.4 years) who had more autoantibodies (p&lt;0.0001) and higher pre-classification (baseline) CSQ scores (p&lt;0.0001). Relatives who transitioned also had elevated baseline levels of inflammatory mediators, including BLyS, SCF, and IFN-associated chemokines (p&lt;0.05), with concurrent decreased regulatory mediators, including TGF-β and IL-10 (p&lt;0.05). Logistic regression analysis revealed that baseline ACR and CSQ scores (but not autoantibodies), and baseline plasma levels of SCF and TGF-β were significant and independent predictors of SLE transition. Thus, perturbations in immune-mediated processes precede SLE clinical classification and can help identify unaffected relatives at highest risk of future SLE classification for early intervention studies.

The IRF5-TNPO3 association with systemic lupus erythematosus has two components that other autoimmune disorders variably share

Exploiting genotyping, DNA sequencing, imputation and trans-ancestral mapping, we used Bayesian and frequentist approaches to model the IRF5-TNPO3 locus association, now implicated in two immunotherapies and seven autoimmune diseases. Specifically, in systemic lupus erythematosus (SLE), we resolved separate associations in the IRF5 promoter (all ancestries) and with an extended European haplotype. We captured 3230 IRF5-TNPO3 high-quality, common variants across 5 ethnicities in 8395 SLE cases and 7367 controls. The genetic effect from the IRF5 promoter can be explained by any one of four variants in 5.7 kb (P-valuemeta = 6 × 10(-49); OR = 1.38-1.97). The second genetic effect spanned an 85.5-kb, 24-variant haplotype that included the genes IRF5 and TNPO3 (P-valuesEU = 10(-27)-10(-32), OR = 1.7-1.81). Many variants at the IRF5 locus with previously assigned biological function are not members of either final credible set of potential causal variants identified herein. In addition to the known biologically functional variants, we demonstrated that the risk allele of rs4728142, a variant in the promoter among the lowest frequentist probability and highest Bayesian posterior probability, was correlated with IRF5 expression and differentially binds the transcription factor ZBTB3. Our analytical strategy provides a novel framework for future studies aimed at dissecting etiological genetic effects. Finally, both SLE elements of the statistical model appear to operate in Sjögren's syndrome and systemic sclerosis whereas only the IRF5-TNPO3 gene-spanning haplotype is associated with primary biliary cirrhosis, demonstrating the nuance of similarity and difference in autoimmune disease risk mechanisms at IRF5-TNPO3.

Interferon and TNF family soluble inflammatory mediators are detected prior to and increase at Systemic Lupus Erythematosus classification in serum samples from military personnel acquired from the Department of Defense Serum Repository (P3087)

Processes that lead to clinical illness in SLE years before diagnosis are not well characterized. This study evaluates the temporal relationship between autoantibody production, cytokine levels and the onset of SLE. Serial sera from 60 SLE cases before diagnosis with no ACR criteria to SLE classification (average timespan=4.4 years) and matched healthy controls (HC) were obtained from the DODSR. Sera samples were tested for autoantibodies (BioPlex2200), C-reactive protein (hs-CRP), Von Willebrand’s Factor (VWF) and 32 soluble inflammatory mediators, including cytokines, chemokines, and soluble receptors. Patient samples before ACR classification had significant (p &lt; 0.01) alterations in 16 soluble mediators of inflammation, as well as VWF and hs-CRP. TNF Receptor levels, TNFRI, TNFRII, BLyS, and APRIL, dramatically increased as lupus classification approached (p &lt; 0.001). The increase in TNFR shedding parallels the accumulation of autoantibodies in SLE cases. Interferon (IFN)-associated mediators of inflammation, IFN-γ, IP-10, MIG, and MIP-1α (p &lt; 0.01), were also increased leading up to classification. That these alterations are present prior to the transition to active SLE suggests that multiple perturbations in immune-mediated inflammatory processes occur long before clinical classification and suggest that high-risk, pre-clinical individuals, can be identified before their illness is clinically manifested and damage occurs.

The effect of enterotoxigenic Escherichia coli F4ab,ac on early-weaned piglets: a gene expression study

Diarrhoea in neonatal and early-weaned piglets due to enterotoxigenic Escherichia coli-F4 (ETEC-F4) is an important problem in the pig farming industry. There is substantial evidence for a genetic basis for susceptibility to ETEC-F4 since not all pigs suffer from diarrhoea after an ETEC-F4 infection. A region on SSC13 has been found to be in close linkage to the susceptibility of piglets for ETEC-F4ab,ac. Potential candidate genes on SSC13 have been examined and although some polymorphisms were found to be in linkage disequilibrium with the phenotype, the causative mutation has not yet been found. In this study we are looking at the expression of porcine genes in relation to ETEC-F4ab,ac. With the aid of the Affymetrix GeneChip Porcine Genome Array we were able to find differentially expressed genes between ETEC-F4ab,ac receptor positive (Fab,acR(+)) piglets without diarrhoea and F4ab,acR(+) piglets with diarrhoea or F4ab,acR(-) animals. Since the susceptibility to ETEC-F4ab,ac was described as a Mendelian trait, it is not so surprisingly that only two differentially expressed genes, transferrin receptor (TFRC) and trefoil factor 1 (TFF1), came out of the analysis. Although both genes could pass for functional candidate genes only TFRC also mapped to the region on SSC13 associated with susceptibility for ETEC-F4, which makes TFRC a positional functional candidate gene. Validation by qRT-PCR confirmed the differential expression of TFRC and TFF1. In piglets without diarrhoea, the expression of both genes was higher in F4ab,acR(+) than in F4ab,acR(-) piglets. Similarly, TFRC and TFF1 expression in F4ab,acR(+) piglets without diarrhoea was also higher than in F4ab,acR(+) piglets with diarrhoea. Consequently, although both genes might not play a role as receptor for F4 fimbriae, they could be of great importance during an ETEC-F4 outbreak. An upregulation of TFRC can be a consequence of the piglets ability to raise an effective immune response. An elevation of TFF1, a protein involved in mucin formation, may also affect the piglet's capability to cope with ETEC bacteria, rather than being a receptor for its fimbriae.

Labile complexes facilitate cadmium uptake by Caco-2 cells

The Free Ion Activity Model (FIAM) predicts that metal uptake in biota is related to the free ion activity in the external solution and that metal complexes do not contribute. However, studies with plants have shown that labile metal complexes enhance metal bioavailability when the uptake is rate-limited by transport of the free ion in solution to the uptake site. Here, the role of labile complexes of Cd on metal bioavailability was assessed using Caco-2 cells, the cell model for intestinal absorption. At low Cd(2+) concentration (1 nM), the CdCl(n)(2-n) complexes contributed to the uptake almost to the same extent as the free ion. At large Cd(2+) concentration (10 μM), the contribution of the complexes was much smaller. At constant Cd(2+) concentration, Cd intake in the cells from solutions containing synthetic ligands such as EDTA increased as the dissociation rate of the cadmium complexes increased, and correlated well with the Cd diffusion flux in solution measured with the Diffusive Gradient in Thin Films technique (DGT). The Cd intake fluxes in the cells were well predicted assuming that the specific uptake is limited by diffusion of the free Cd(2+) ion to the cell surface. Our results underline that speciation of Cd has a major effect on its uptake by intestinal cells, but the availability is not simply related to the free ion concentration. Labile complexes of Cd enhance metal bioavailability in these cells, likely by alleviating diffusive limitations.

Susceptibility of piglets to enterotoxigenic Escherichia coli is not related to the expression of MUC13 and MUC20

Enterotoxigenic Escherichia coli (ETEC) is one of the most frequently isolated enteropathogens in production animals, especially pigs and calves. Economically, the swine industry is by far the most affected by infections with ETEC because of mortality, morbidity and decreased growth rate of newborn and early-weaned piglets. After ingestion by the animal, these bacteria attach themselves to specific receptors on the small intestinal epithelium by means of proteinaceous surface appendages, the fimbriae. The F4 fimbriae, which attach to the F4 receptor, are the most studied. The aim of our study was to investigate gene expression in the small intestine of piglets of MUC13 and MUC20 in relation to animals with a different treatment towards or a different reaction on ETEC-F4ac by means of quantitative reverse transcription chain reaction (qRT/PCR). MUC13 and MUC20 are positional candidate genes for this F4ac receptor and are located in the region on SSC13q41 that segregates with the susceptibility to ETEC-F4ac. The condition of the small intestine is crucial when examining expression differences between different samples. Therefore, the expression of two genes, fatty-acid binding protein 2, intestinal (FABP2) and pancreatitis-associated protein (PAP), now known as regenerating islet-derived 3 alpha (REG3A) in the small intestine was simultaneously checked. FABP2, a standard for epithelial content, reflects the state of damage, whereas REG3A is a measure for inflammation in the small intestine. The four different substudies presented here suggest that expression of MUC13 and MUC20 is not related to the susceptibility of piglets to ETEC-F4ac.

A loss-of-function variant of the antiviral molecule MAVS is associated with a subset of systemic lupus patients (47.10)

Dysregulation of the antiviral immune response may contribute to autoimmune diseases. Here, we hypothesized that altered expression or function of MAVS, a key molecule downstream of the viral sensors RIG-I and MDA-5, may impair antiviral cell signaling and thereby influence the risk for systemic lupus erythematosus (SLE), the prototype autoimmune disease. We used molecular techniques to screen non-synonymous single-nucleotide polymorphisms (SNPs) in the MAVS gene for functional significance in human cell lines, and identified one critical loss-of-function variant (C79F, rs11905552). This SNP substantially reduced expression of type I interferon and other proinflammatory mediators, and was found almost exclusively in the African-American population. Importantly, in African-American SLE patients, the C79F allele was associated with low type I interferon production and absence of anti-RNA-binding protein antibodies. These serologic associations were not related to a distinct, functionally neutral, MAVS SNP Q198K. Hence, this is the first demonstration that an uncommon genetic variant in the MAVS gene has a functional impact upon the anti-viral interferon pathway in vivo in humans, and is associated with a novel sub-phenotype in SLE.

C8orf13/BLK association with systemic lupus erythematosus across different ethnicities (136.28)

SLE is a complex autoimmune disease with immunological abnormalities that targets B cell functions and development. Previous genome-wide association studies identified C8orf13/BLK as a novel SLE risk factor. BLK (B lymphoid tyrosine kinase) has been shown to have potential effects on B cell develoment. The main objectives of this study are to: 1.) assess this association in independent populations and 2.) determine if BLK risk alleles correlate with alteration in peripheral blood B cell development and protein expression. We genotyped 52 SNPs within the C8orf13/BLK region in European-derived, Asian and African American populations. rs13277113 is associated with SLE in all three populations. A few novel upstream SNPs within the intergenic region demonstrate a stronger association in Asians. Flow cytometry data suggests there is a significant difference in BLK expression and T2 cells B cell numbers between high-risk and non-risk individuals based on the risk haplotype. Our results suggest that the BLK genetic polymorphisms alter immune system development and function to increase the risk for SLE development. Supported by NIH RR020143, RR015577, NIAID-DAIT-BAA-05-11, AI031584, AR053483, AR48940, AI063274, AR052125, AR043247 and OCAST # HR08-037.

Virion polypeptide specificity of immune complexes and antibodies in cats inoculated with feline infectious peritonitis virus

Immune complexes purified from sera and ascitic fluids of cats after inoculation with feline infectious peritonitis (FIP) virus contained proteins and proteolytic fragments of the peplomer, nucleocapsid, and envelope polypeptides; in addition, host proteins were demonstrated in the immune complexes. Free (uncomplexed) antibodies against the 3 classes of virion polypeptides were detected and quantitated; the weakest and latest response was directed against the peplomer protein. Immunofluorescence titers showed the best correlation with the antibody response directed against the envelope polypeptides. Differences in reactivity were not found between sera and ascitic fluids from the same animals and between seropositive healthy cats and cats which had died of FIP. Humoral antibody and hypergammaglobulinemia showed a linear correlation, but the wide variation in antiviral titers at a given concentration of gamma-globulin indicated that additional (autoimmune) reactions occur during the pathogenesis of FIP.