Analysis of polymorphisms affecting immune complex handling in systemic lupus erythematosus

Targeting ADCC: A different approach to HER2 breast cancer in the immunotherapy era

The clinical outcome of patients with human epidermal growth factor receptor 2 (HER2) amplified breast carcinoma (BC) has improved with the development of anti-HER2 targeted therapies. However, patients can experience disease recurrence after curative intent and disease progression in the metastatic setting. In the current era of evolving immunotherapy agents, the understanding of the immune response against HER2 tumor cells developed by anti-HER2 antibodies (Abs) is rapidly evolving. Trastuzumab therapy promotes Natural Killer (NK) cell activation in patients with BC overexpressing HER2, indicating that the efficacy of short-term trastuzumab monotherapy, albeit direct inhibition of HER, could also be related with antibody-dependent cell-mediated cytotoxicity (ADCC). Currently, dual HER2 blockade using trastuzumab and pertuzumab is the standard of care in early and advanced disease as this combination could confer an additive effect in ADCC. In patients with disease relapse or progression, ADCC may be hampered by several factors such as FcγRIIIa polymorphism and an immunosuppressive environment, among others. Hence, new drug development strategies are being investigated aiming to boost the ADCC response triggered by anti-HER2 therapy. In this review, we summarize these strategies and the rationale, through mAbs engineering and combinatorial strategies, focusing on clinical results and ongoing trials.

Boosting therapeutic potency of antibodies by taming Fc domain functions

Monoclonal antibodies (mAbs) are one of the most widely used drug platforms for infectious diseases or cancer therapeutics because they selectively target pathogens, infectious cells, cancerous cells, and even immune cells. In this way, they mediate the elimination of target molecules and cells with fewer side effects than other therapeutic modalities. In particular, cancer therapeutic mAbs can recognize cell-surface proteins on target cells and then kill the targeted cells by multiple mechanisms that are dependent upon a fragment crystallizable (Fc) domain interacting with effector Fc gamma receptors, including antibody-dependent cell-mediated cytotoxicity and antibody-dependent cell-mediated phagocytosis. Extensive engineering efforts have been made toward tuning Fc functions by either reinforcing (e.g. for targeted therapy) or disabling (e.g. for immune checkpoint blockade therapy) effector functions and prolonging the serum half-lives of antibodies, as necessary. In this report, we review Fc engineering efforts to improve therapeutic potency, and propose future antibody engineering directions that can fulfill unmet medical needs.

Fine-tuning the function of monoclonal antibodies (mAbs) holds promise for developing new therapeutic agents. Antibodies bind to pathogens or cancer cells, flagging them with Fc (fragment crystallizable) domain for destruction by the immune system. mAbs attached only to specific target cells enable lower side effect than other conventional drugs. Sang Taek Jung at Korea University and Tae Hyun Kang at Kookmin University, both in Seoul, reviewed recent developments in engineering therapeutic potency of mAbs. They report that mAbs can be engineered to activate effective immune cell types to treat a particular disease. Engineering can also increase mAbs’ persistence in the blood, enabling less frequent administration. Antibodies engineered to bind to two different antigens at once can also improve therapeutic efficacy. Applying these techniques could help developing new treatments against cancer, and infectious and autoimmune diseases.

Mannose binding lectin (MBL) 2 gene polymorphism & its association with clinical manifestations in systemic lupus erythematosus (SLE) patients from western India

Background & objectives:

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease characterized by production of autoantibodies. Mannose binding lectin (MBL) is an important element of the innate defense system. The present study was undertaken to determine whether variant alleles in MBL2 gene were associated with disease severity in SLE patients.

Methods:

The MBL alleles [-550, -221, +4, Codon 52, Codon 54 and Codon 57] were studied by PCR- RFLP (restriction fragment length polymorphism) method in 100 SLE patients fulfilling ACR (American College of Rheumatology) criteria along with 100 healthy controls. SLE disease activity was evaluated using SLE Disease Activity Index (SLEDAI) score.

Results:

Homozygosity for MBL variant allele (O/O) was observed in 24 per cent of the SLE patients compared to 16 per cent of the normal controls, while no difference was found for heterozygosity (A/O) (37 vs 35%). A significant difference was reported in incidence of double heterozygosity for mutant allele B and D (B/D) among SLE patients as against control group (P = 0.015). MBL genotypes did not show any association with renal involvement.

Interpretation & conclusions:

In this study from western India, MBL gene polymorphism showed an influence as a possible risk factor for susceptibility to SLE, but had no direct effect on disease characteristics. Further studies need to be done on a larger number of SLE patients in different regions of the country.

Effective phagocytosis of low Her2 tumor cell lines with engineered, aglycosylated IgG displaying high FcγRIIa affinity and selectivity

Glycans anchored to residue N297 of the antibody IgG Fc domain are critical in mediating binding toward FcγRs to direct both adaptive and innate immune responses. However, using a full length bacterial IgG display system, we have isolated aglycosylated Fc domains with mutations that confer up to a 160-fold increase in the affinity toward the low affinity FcγRIIa-R131 allele as well as high selectivity against binding to the remarkably homologous human inhibitory receptor, FcγRIIb. The mutant Fc domain (AglycoT-Fc1004) contained a total of 5 amino acid substitutions that conferred an activating to inhibitory ratio of 25 (A/I ratio; FcyRIIa-R131:FcγRIIb). Incorporation of this engineered Fc into trastuzumab, an anti-Her2 antibody, resulted in a 75% increase in tumor cell phagocytosis by macrophages compared to that of the parental glycosylated trastuzumab with both medium and low Her2-expressing cancer cells. A mathematical model has been developed to help explain how receptor affinity and the A/I ratio relate to improved antibody dependent cell-mediated phagocytosis. Our model provides guidelines for the future engineering of Fc domains with enhanced effector function.

Anti-tumor activity and toxicokinetics analysis of MGAH22, an anti-HER2 monoclonal antibody with enhanced Fcγ receptor binding properties

INTRODUCTION

Response to trastuzumab in metastatic breast cancer correlates with expression of the high binding variant (158V) of the activating Fcγ receptor IIIA (CD16A). We engineered MGAH22, a chimeric anti-HER2 monoclonal antibody with specificity and affinity similar to trastuzumab, with an Fc domain engineered for increased binding to both alleles of human CD16A.

METHODS

MGAH22 was compared to an identical anti-HER2 mAb except for a wild type Fc domain. Antibody-dependent cell cytotoxicity (ADCC) assays were performed with HER2-expressing cancer cells as targets and human PBMC or purified NK cells as effectors. Xenograft studies were conducted in mice with wild type murine FcγRs; in mice lacking murine CD16; or in mice lacking murine CD16 but transgenic for human CD16A-158F, the low-binding variant. The latter model reproduces the differential binding between wild type and the Fc-optimized mAb for human CD16A. The JIMT-1 human breast tumor line, derived from a patient that progressed on trastuzumab therapy, was used in these studies. Single and repeat dose toxicology studies with MGAH22 administered intravenously at high dose were conducted in cynomolgus monkeys.

RESULTS

The optimized Fc domain confers enhanced ADCC against all HER2-positive tumor cells tested, including cells resistant to trastuzumab's anti-proliferative activity or expressing low HER2 levels. The greatest improvement occurs with effector cells isolated from donors homozygous or heterozygous for CD16A-158F, the low-binding allele. MGAH22 demonstrates increased activity against HER2-expressing tumors in mice transgenic for human CD16A-158F. In single and repeat-dose toxicology studies in cynomolgus monkeys, a species with a HER2 expression pattern comparable to that in humans and Fcγ receptors that exhibit enhanced binding to the optimized Fc domain, MGAH22 was well tolerated at all doses tested (15-150 mg/kg) and exhibited pharmacokinetic parameters similar to that of other anti-HER2 antibodies. Induction of cytokine release by MGAH22 in vivo or in vitro was similar to that induced by the corresponding wild type mAb or trastuzumab.

CONCLUSIONS

The data support the clinical development of MGAH22, which may have utility in patients with low HER2 expressing tumors or carrying the CD16A low-binding allele.

Monocyte polarization: the relationship of genome-wide changes in H4 acetylation with polarization

The character of monocytes is both molded by and contributes to ongoing immune responses. We hypothesized that monocyte polarization could have durable qualities and these would be mediated partly by changes in the chromatin. We defined genome-wide expression and histone H4 acetylation (H4ac) changes after γ-interferon (IFN), α-IFN and interleukin-4 treatment. To identify genes with altered potential for expression, we stimulated polarized monocytes and identified genes up- or downregulated after polarization and stimulation but not either treatment alone. We also defined durability after an 18-h or 3-day washout. Genes uniquely regulated after the combination of polarization and stimulus were durably altered, with 51% of the effects being durable. This gene set was highly enriched for cytokine-induced alterations in H4ac, with P-values ranging from 10(-24) to 10(-37). Certain regulons defined by patterns of expression were also associated with altered H4ac, with P-values ranging from 10(-4) to 10(-29). Networking software revealed a high density of mitogen-activated protein (MAP) kinase nodes in these clusters. Therefore, some changes in monocyte gene expression were sustained over a 3-day period. These durably altered gene sets were enriched for changes in H4ac and were associated with potential MAP kinase effects.

Genetic susceptibility to systemic lupus erythematosus in the genomic era

Our understanding of the genetic basis of systemic lupus erythematosus (SLE) has been rapidly advanced using large-scale, case-control, candidate gene studies as well as genome-wide association studies during the past 3 years. These techniques have identified more than 30 robust genetic associations with SLE including genetic variants of HLA and Fcγ receptor genes, IRF5, STAT4, PTPN22, TNFAIP3, BLK, BANK1, TNFSF4 and ITGAM. Most SLE-associated gene products participate in key pathogenic pathways, including Toll-like receptor and type I interferon signaling pathways, immune regulation pathways and those that control the clearance of immune complexes. Disease-associated loci that have not yet been demonstrated to have important functions in the immune system might provide new clues to the underlying molecular mechanisms that contribute to the pathogenesis or progression of SLE. Of note, genetic risk factors that are shared between SLE and other immune-related diseases highlight common pathways in the pathophysiology of these diseases, and might provide innovative molecular targets for therapeutic interventions.

Plasminogen activator inhibitor-1 polymorphisms (-844 G>A and HindIII C>G) in systemic lupus erythematosus: association with clinical variables

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the presence of autoantibodies against nuclear autoantigens as well as cytoplasmic and circulating proteins. Recent studies have demonstrated mechanisms responsible for modulation of the immune response by the plasminogen activator inhibitor-1 (PAI-1). Furthermore, the endogenous PAI-1 has shown to promote a Th2 immune response. We assessed the -844 G>A and HindIII C>G PAI-1 polymorphisms in SLE. In a case-control study of 71 SLE patients classified according to ACR criteria and 71 healthy subjects (HS). The A allele of -844 PAI-1 polymorphism showed a significant difference in SLE patients (41%) when compared with HS (27%) [P = 0.01; OR = 1.8, 95%, CI = 1.1-3.0]. In addition, the -844 G>A PAI-1 polymorphism was associated with increased risk for SLE in a dominant genetic model (G/G vs. G/A + A/A; OR = 2.3, 95% CI = 1.14-4.44). Also, anti-RNP positive antibodies in SLE were associated with G/G -844 PAI-1 genotype. The HindIII polymorphism did not show any differences. The haplotype analysis showed that the AC haplotype confers susceptibility to SLE (OR = 3.1, 95% CI, 1.45-6.52; P = 0.003). The AC haplotype of the -844 and HindIII PAI-1 polymorphism might be an additional susceptibility factor to SLE in Mexicans.

Fc receptor-mediated antiviral antibodies

PURPOSE OF REVIEW

We summarize current information on Fc receptor-mediated antiviral activities of antibodies. These activities include Fcgamma receptor-mediated inhibition and neutralization of HIV on antigen-presenting cells, antibody-dependent cellular cytotoxicity, and antibody-dependent cell-mediated virus inhibition (ADCVI).

RECENT FINDINGS

An Fcgamma receptor-mediated mechanism that results in augmented neutralization and may render nonneutralizing antibodies inhibitory has been demonstrated in antigen-presenting cell. Antibody-dependent cellular cytotoxicity antibody activity correlates inversely with HIV disease progression in humans, and higher vaccine-induced antibody-dependent cellular cytotoxicity antibody responses are associated with lower acute simian immunodeficiency virus viremia levels in macaques. Following vaccination with rgp120, ADCVI antibody levels are higher among those with a lower rate of sexually acquired HIV infection. Nonneutralizing simian immunodeficiency virus immune serum that prevents infection of newborn macaques after oral challenge has potent ADCVI antibody activity. Abrogating the ability of the Fc segment of the broadly neutralizing mAb b12 to bind to Fcgamma receptors and to mediate ADCVI substantially reduces b12's protective effect in a simian/human immunodeficiency virus vaginal challenge model.

SUMMARY

Fc-FcgammaR interactions play a critical role in the biological function of antibody and are likely to be instrumental in preventing or modulating lentiviral infection. Exploiting antibody responses that depend on Fc-FcgammaR interactions may help widen the breadth and increase the potency of vaccine-induced antibody. Although the importance of generating optimal Fab-antigen interactions cannot be overestimated, improving Fc-FcgammaR interactions through adjuvants or other strategies provides another option for improving HIV vaccines and immunotherapies.

Complement receptor 1 (A3650G RsaI and intron 27 HindIII) polymorphisms and risk of gallbladder cancer in north Indian population

Decreased expression due to genetic variations in complement receptor 1 (CR1) on erythrocytes might result in reduced clearance of immune complexes, conferring interindividual variation for gallbladder cancer (GBC) susceptibility. We studied role of CR1 (A(3650)G RsaI and Intron 27 HindIII) polymorphisms in gallstone disease and GBC in north Indian population. Study included 185 GBC patients, 185 gallstone patients and 200 controls. Genotyping was done by PCR-RFLP. Result showed GG genotype and G allele of CR1 A(3650)G RsaI were conferring significant risk for GBC [(P = 0.022; OR = 1.94; 95% CI = 1.1-3.4) and (P = 0.035; OR = 1.35; 95% CI = 1.0-3.8) respectively]. Also, comparison of GBC patients with gallstone patients showed increased risk for GBC in presence of GG genotype and G allele GBC (P = 0.048; OR = 1.74; 95% CI = 1.0-3.0) and (P = 0.027; OR = 1.39; 95% CI = 1.0-1.8) respectively. No association of CR1 A(3650)G RsaI polymorphism was observed when gallstone patients were compared with controls. CR1 Intron 27 HindIII polymorphism was not associated with GBC and gallstone susceptibility. Haplotype analysis showed increased risk of GBC in presence of G,L haplotype (P = 0.046; OR = 1.35: 95% CI = 1.0-1.8). Subgroup stratifications on basis of gender and gallstone status showed GG genotype of CR1 A(3650)G RsaI polymorphism imparted high risk for GBC in females (P = 0.043; OR = 1.99: 95% CI = 1.4-3.9). Also there was increased risk for GBC in presence as well as absence of gallstones (OR = 1.85 and 1.76 respectively), but it was not statistically significant. We conclude that CR1 A(3650)G RsaI polymorphism plays an important role in conferring genetic susceptibility to gallbladder cancer GBC in north Indian population.

Association of the BANK 1 R61H variant with systemic lupus erythematosus in Americans of European and African ancestry

Recently an association was demonstrated between the single nucleotide polymorphism (SNP), rs10516487, within the B-cell gene BANK1 and systemic lupus erythematosus (SLE) as a consequence of a genome wide association study of this disease in European and Argentinean populations. In a bid for replication, we examined the effects of the R61H non-synonymous variant with respect to SLE in our genotyped American cohorts of European and African ancestry. Utilizing data from our ongoing genome-wide association study in our cohort of 178 Caucasian SLE cases and 1808 Caucasian population-based controls plus 148 African American (AA) SLE cases and 1894 AA population-based controls we investigated the association of the previously described non-synonymous SNP at the BANK1 locus with the disease in the two ethnicities separately. Using a Fisher’s exact test, the minor allele frequency (MAF) of rs10516487 in the Caucasian cases was 22.6% while it was 31.2% in Caucasian controls, yielding a protective odds ratio (OR) of 0.64 (95% CI 0.49-0.85; one-sided p = 7.07 × 10⁻⁴). Furthermore, the MAF of rs10516487 in the AA cases was 18.7% while it was 23.3% in AA controls, yielding a protective OR of 0.75 (95% CI 0.55–1.034; one-sided p = 0.039). The OR of the BANK1 variant in our study cohorts is highly comparable with that reported previously in a South American/European SLE case-control cohort (OR = 0.72). As such, R61H in the BANK1 gene confers a similar magnitude of SLE protection, not only in European Americans, but also in African Americans.

Utilization of immunoglobulin G Fc receptors by human immunodeficiency virus type 1: a specific role for antibodies against the membrane-proximal external region of gp41

Receptors (FcgammaRs) for the constant region of immunoglobulin G (IgG) are an important link between humoral immunity and cellular immunity. To help define the role of FcgammaRs in determining the fate of human immunodeficiency virus type 1 (HIV-1) immune complexes, cDNAs for the four major human Fcgamma receptors (FcgammaRI, FcgammaRIIa, FcgammaRIIb, and FcgammaRIIIa) were stably expressed by lentiviral transduction in a cell line (TZM-bl) commonly used for standardized assessments of HIV-1 neutralization. Individual cell lines, each expressing a different FcgammaR, bound human IgG, as evidence that the physical properties of the receptors were preserved. In assays with a HIV-1 multisubtype panel, the neutralizing activities of two monoclonal antibodies (2F5 and 4E10) that target the membrane-proximal external region (MPER) of gp41 were potentiated by FcgammaRI and, to a lesser extent, by FcgammaRIIb. Moreover, the neutralizing activity of an HIV-1-positive plasma sample known to contain gp41 MPER-specific antibodies was potentiated by FcgammaRI. The neutralizing activities of monoclonal antibodies b12 and 2G12 and other HIV-1-positive plasma samples were rarely affected by any of the four FcgammaRs. Effects with gp41 MPER-specific antibodies were moderately stronger for IgG1 than for IgG3 and were ineffective for Fab. We conclude that FcgammaRI and FcgammaRIIb facilitate antibody-mediated neutralization of HIV-1 by a mechanism that is dependent on the Fc region, IgG subclass, and epitope specificity of antibody. The FcgammaR effects seen here suggests that the MPER of gp41 could have greater value for vaccines than previously recognized.

The genetics and epigenetics of autoimmune diseases

Self tolerance loss is fundamental to autoimmunity. While understanding of immune regulation is expanding rapidly, the mechanisms causing loss of tolerance in most autoimmune diseases remain elusive. Autoimmunity is believed to develop when genetically predisposed individuals encounter environmental agents that trigger the disease. Recent advances in the genetic and environmental contributions to autoimmunity suggest that interactions between genetic elements and epigenetic changes caused by environmental agents may be responsible for inducing autoimmune disease. Genetic loci predisposing to autoimmunity are being identified through multi-center consortiums, and the number of validated genes is growing rapidly. Recent reports also indicate that the environment can contribute to autoimmunity by modifying gene expression through epigenetic mechanisms. This article will review current understanding of the genetics and epigenetics of lupus, rheumatoid arthritis, multiple sclerosis and type 1 diabetes, using systemic lupus erythematosus as the primary example. Other autoimmune diseases may have a similar foundation.

Mannose-binding lectin gene polymorphisms and the development of coal workers' pneumoconiosis in Japan

BACKGROUND

Infection, immunity and genetic factors play roles in the development of coal worker's pneumoconiosis (CWP) and progressive massive fibrosis (PMF). We investigate whether the genetic polymorphisms of mannose-binding lectin (MBL), one of the key molecules of innate immunity, is associated with the susceptibility to CWP.

METHOD

MBL2 polymorphisms (codon54, promoter -221, and -550) were assessed for 197 patients with CWP (119 with nodular CWP and 78 with PMF) and 153 unexposed regional controls. Serum MBL concentrations were measured in 119 CWP patients.

RESULTS

Three polymorphisms were in linkage disequilibrium for all study populations. The MBL2 genotype and haplotypes were associated with lower serum MBL levels. The frequency of such MBL2 genotype and haplotypes were significantly higher in patients with CWP compared to controls, whereas these distributions were not different between patients with nodular CWP and those with PMF.

CONCLUSION

MBL2 polymorphisms and haplotypes may be one of the genetic determinants for the susceptibility of CWP.

Meta analysis on the association between FcgammaRIIa-R/H131 polymorphisms and systemic lupus erythematosus

In order to study the association between FcgammaRIIa gene polymorphisms and the risk of systemic lupus erythematosus (SLE) and lupus nephritis, relevant studies were identified from electronic databases. A meta-analysis of relevant studies was performed for heterogeneity test and pooled OR calculation. When all groups were pooled, a significant association of FcgammaRIIa-R131 allele and increased SLE risk was found. But this association was not observed in lupus nephritis. In the subgroup analysis, a clear effect of R allele in SLE was shown in European and Asian subgroups. Similarly, RR homozygous genotype was found to be a risk factor of SLE and lupus nephritis. The association between RR genotype and SLE was shown in European and Asian descents. However, the association between RR genotype and lupus nephritis was not found in any ethnic subgroups. Taken together, our study suggests that the FcgammaRIIa-R/H131 polymorphism might contribute to the susceptibility to SLE and lupus nephritis.

FcgammaRIIa genotype predicts progression of HIV infection

Polymorphisms in FcgammaR genes are associated with susceptibility to or severity of a number of autoimmune and infectious diseases. We found that HIV-infected men in the Multicenter AIDS Cohort Study with the FcgammaRIIa RR genotype progressed to a CD4(+) cell count of <200/mm(3) at a faster rate than individuals with the RH or HH genotypes (relative hazard = 1.6; p = 0.0001). However, progression to AIDS (using the broad definition of either a CD4(+) cell count <200/mm(3) or development of an AIDS-defining illness) was less impacted by FcgammaRIIa genotype, largely because HH homozygotes had an increased risk of Pneumocystis jiroveci pneumonia as an AIDS-defining illness. We also showed that chronically infected subjects develop a substantial anti-gp120-specific IgG2 response. Moreover, HIV-1 immune complexes are more efficiently internalized by monocytes from HH subjects compared with RR subjects, likely because of the presence of IgG2 in the complexes. Finally, the FcgammaRIIIa F/V gene polymorphism was not associated with progression of HIV infection, but, as demonstrated previously, did predict the risk of Kaposi's sarcoma. These results demonstrate the importance of FcgammaRs in AIDS pathogenesis and point toward a critical role for interactions between FcgammaRs and immune complexes in disease progression.

The role of mannose-binding lectin in systemic lupus erythematosus

Susceptibility to systemic lupus erythematosus (SLE) is associated with genetic, hormonal, immunological, and environmental factors. Many genes have been related with the appearance of SLE, including several loci that code different complement components and their receptors. Some genetic deficiencies of complement molecules are strongly associated with SLE, probably because these deficiencies could cause decreased clearance of apoptotic cell material. As a consequence of the apoptotic material accumulation, high levels of autoantigens can be presented inappropriately to the immune system in an inflammatory context, resulting in an imbalance on the mechanisms of immunological tolerance, immune system activation, and autoantibody production. Recent studies proposed a role to the mannose-binding lectin (MBL) in the SLE physiopathogenesis. This protein activates the complement system, and the presence of several polymorphisms at the promoter and coding regions of the MBL-2 gene determines alterations at the plasma levels of MBL. Some of these polymorphisms have been associated with SLE susceptibility, as well as with clinical and laboratory typical features of this disease, cardiovascular events, and infections. Besides, it has been described that the presence of anti-MBL autoantibodies in sera of SLE patients can influence MBL plasma levels and its functional activity.

The sodium-dependent glucose cotransporter SLC5A11 as an autoimmune modifier gene in SLE

Genetic studies in several human autoimmune diseases suggest that the pericentromeric region of chromosome 16 might harbor an autoimmune modifier gene. We hypothesized that the sodium-dependent glucose cotransporter gene SLC5A11 is such a gene, and so might interact with immune-related genes. Herein, this hypothesis was tested in a genetic evaluation of the multiple gene effect in systemic lupus erythematosus (SLE). We used the case-control candidate gene association approach. Eight immune-related genes involved in inflammation and autoantibody generation and clear-up [interleukin 1 receptor antagonist (IL1RN), interleukin 1-beta (IL1-beta), tumor necrosis factor-alpha (TNF-alpha), lymphotoxin-alpha (LTA), tumor necrosis factor ligand superfamily, member 6 (TNFSF6), programmed cell death 1 (PDCD1), C2, and complement component 4 (C4)] were selected for study. Frequency of each candidate's genotype and allele between case and control were compared. Results were stratified by reanalyzing genotype data with relevant symptoms. Finally, improved computational data mining was used to analyze the phenotypes in a large data set. In the frequency analysis, only IL1-beta was significantly associated with SLE. Stratification analysis showed a significant association with SLE symptoms between SLC5A11 and the other immune-related genes, with the exceptions of TNFSF6 and C4. SLC5A11 was significantly associated with low C4 (as was TNF-alpha), anti-Smith antibody (anti-Sm) (as was C2), serositis, and alopecia. Finally, SLC5A11 interacted with PDCD1, TNF-alpha, LTA, and C4. After our study, we concluded that SLC5A11 is involved with some immune effects and interacts with immune-related gene(s), consistent with its function as an autoimmune modifier gene. Furthermore, SLC5A11 might induce apoptosis through the TNF-alpha, PDCD1 pathway. The present genotype-phenotype mapping approach should be applicable to genetic study of other complex diseases.

Evaluating the role of the genetic variations of PTPN22, NFKB1, and FcGRIIIA genes in inflammatory bowel disease: a meta-analysis

BACKGROUND

We tested several polymorphisms of genes involved in the mucosal immune system in a population of inflammatory bowel disease (IBD) patients to investigate their possible implication in disease predisposition.

METHODS

Polymorphisms of 3 candidate genes (PTPN22, NFkB1, and FcGRIIIA) were investigated in 649 IBD patients (343 with Crohn's disease [CD] and 306 with ulcerative colitis [UC]), 176 unaffected relatives, and 256 healthy controls. Allele and genotype frequencies were correlated with clinical characteristics and major variants of the CARD15 gene. Our findings were pooled in a meta-analysis with the available studies in the literature.

RESULTS

No significant difference for the PTPN22 and NFkB1 variants was found. In contrast, allele and genotype frequencies of the G559T allele of the FcGRIIIA gene were significantly different in CD patients compared to controls (allele T 12% versus 8%, odds ratio [OR] = 1.58, 95% confidence interval [CI] 1.06-2.35; GT genotype 23% versus 16%, OR = 1.64, 95% CI = 1.08-2.5). However, no significant overtransmission of the T allele was confirmed at the family-based analysis. For all genes, neither an interaction with CARD15 gene, nor a significant difference at genotype/phenotype analysis was demonstrated, included response to medical therapy.

CONCLUSIONS

Although involved in autoimmune diseases, the PTPN22 and NFkB1 genes do not seem involved in the IBD predisposition, also according to meta-analysis results. The association with the G559T polymorphism of the FcGRIIIA gene in CD patients deserves further investigation.

Structural basis for PRYSPRY-mediated tripartite motif (TRIM) protein function

The human tripartite motif (TRIM) family comprises 70 members, including HIV restriction factor TRIM5alpha and disease-associated proteins TRIM20 (pyrin) and TRIM21. TRIM proteins have conserved domain architecture but diverse cellular roles. Here, we describe how the C-terminal PRYSPRY domain mediates diverse TRIM functions. The crystal structure of TRIM21 PRYSPRY in complex with its target IgG Fc reveals a canonical binding interface comprised of two discrete pockets formed by antibody-like variable loops. Alanine scanning of this interface has identified the hot-spot residues that control TRIM21 binding to Fc; the same hot-spots control HIV/murine leukemia virus restriction by TRIM5alpha and mediate severe familial Mediterranean fever in TRIM20/pyrin. Characterization of the IgG binding site for TRIM21 PRYSPRY reveals TRIM21 as a superantigen analogous to bacterial protein A and suggests that an antibody bipolar bridging mechanism may contribute to the pathogenic accumulation of anti-TRIM21 autoantibody immune complex in autoimmune disease.

Phenotype and prognosis in African-Americans with multiple sclerosis: a retrospective chart review

CONTEXT

There is an emerging body of literature regarding multiple sclerosis (MS) in African-Americans (AA) that suggests more rapid progression and a worse prognosis in this group. A phenotype of opticospinal MS has been proposed by some publications.

OBJECTIVE

To determine whether AA with MS have a different clinical phenotype, different distribution of clinical subtypes, and/or different levels of disability than Caucasians (CA) with MS. Specifically, is the disability attributable to severe cerebellar disease, which limits ambulation and function?

DESIGN

Retrospective chart analyses of a patient cohort from an academic MS center.

PATIENTS

A total of 86 AA were identified with MS, 79 were followed for > or = 5 years. The control group consisted of 80 randomly-selected CA with MS and similar follow-up.

OUTCOME MEASURES

EDSS at diagnosis, five-year follow-up, and last follow-up; time to walking assistance device; disease subtype; involved functional systems.

RESULTS

AA MS patients displayed more cerebellar dysfunction, and worse EDSS scores at diagnosis, at four to six years follow-up from diagnosis, and at last follow-up compared to the CA MS patients with similar length of follow-up. AA MS patients had earlier and more frequent gait difficulty requiring use of a cane or wheelchair. AA MS patients had a higher prevalence of primary progressive (PP) MS (22 versus 9%) and a lower rate of relapsing-remitting (RR) MS (30 versus 52%) compared to CA.

CONCLUSIONS

Compared to CA patients, MS in AA is characterized by a higher incidence of cerebellar dysfunction and a more rapid accumulation of disabilities. In this cohort, AA patients had a relatively higher rate of the PPMS subtype. These data suggest the presence of fundamental differences in the clinical phenotype and the natural history of MS in AA.

Genetics of Human Lupus Nephritis

Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease in which glomerulonephritis represents one of the most severe clinical presentations. Numerous linkage and association studies, as well as the analysis of murine models, have provided ample evidence for a genetic basis for SLE. Genetic susceptibility to SLE results from the combined actions of multiple alleles, each of them conferring a modest incremental risk. SLE susceptibility genes have been identified in 3 major pathways: apoptosis, lymphocyte activation, and clearance of immune complexes and/or apoptotic debris. There also now is evidence that, within SLE patients, renal end-organ targeting also has a genetic basis, which can be divided into 2 branches. There is evidence that susceptibility alleles that are associated with a greater disease severity also are associated with lupus nephritis. There also is evidence for a set of kidney-specific genes that are likely to amplify or to sensitize to the autoimmune pathology.

Autoimmunity to protective molecules: is it the perpetuum mobile (vicious cycle) of autoimmune rheumatic diseases?

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload and might be involved in the initiation of an autoimmune response. The C1q protein and mannose-binding lectin are activators of the complement system. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein and serum amyloid P, and the long pentraxin family member, pentraxin 3, all of which are involved in innate immunity and in acute-phase responses. In addition to their role in innate immunity and inflammation, each of these proteins participates in the removal of damaged and apoptotic cells. In this article, we discuss the clinical significance of different levels of these proteins, their role in the induction of or protection against autoimmunity, and the presence of specific autoantibodies against them in various autoimmune diseases.

Current topics in human SLE genetics

Susceptibility to systemic lupus erythematosus (SLE) depends on genetic and environmental factors. Genome scan studies have identified eight chromosomal regions with significant linkage to SLE that are confirmed by individual cohorts, suggesting that susceptibility genes may be identified within each of these loci. Linkage studies and single nucleotide polymorphisms (SNPs) have led to the identification of positional candidate genes, and their functional allelic variants have demonstrated molecular pathogenesis of the disease. The discovery of positional candidate genes that are associated with various autoimmune diseases signifies a common pathway in the mechanism of these diseases. Copy polymorphisms in susceptibility genes provide evidence in how genetic plasticity affects complex phenotypes as seen in SLE.

New therapies for systemic lupus erythematosus: cellular targets

Antilymphocyte antibodies have been widely used in oncology and transplantation and are now being tested in autoimmune diseases. For systemic lupus erythematosus, anti-B-cell antibodies are furthest along in development. This article discusses the B-cell abnormalities found in systemic lupus erythematosus and the clinical and immunologic effects of anti-B-cell therapies.

The mannose-binding lectin gene polymorphisms and systemic lupus erythematosus: two case-control studies and a meta-analysis

OBJECTIVE

Mannose-binding lectin (MBL) enhances opsonization and activates complement. Dysfunctional alleles of MBL have been associated with low plasma concentrations of MBL and increased risk of systemic lupus erythematosus (SLE), but genotyping studies have shown inconsistent results. We performed case-control studies of the MBL polymorphisms in 2 Caucasian cohorts and a meta-analysis incorporating all published results of MBL genotyping in SLE to explore whether the MBL functional variants are associated with SLE.

METHODS

MBL genotypes at 7 single-nucleotide polymorphisms were sequenced in 96 European American patients with SLE and 96 age-, race-, and sex-matched controls. MBL codons 52, 54, and 57 were genotyped in 285 German patients with SLE and 200 race-matched controls. Allele frequencies of all known variants were tallied for meta-analysis.

RESULTS

Although there was a trend toward association with MBL polymorphisms in both patient cohorts evaluated, none of them was significantly associated with SLE on its own. Seventeen comparisons from 15 studies were included in the meta-analysis. Publication bias was excluded by Egger's regression test (P = 0.14). The overall odds ratio for MBL codon 54 variant B was 1.406 (95% confidence interval 1.221-1.608; P < 0.001). Stratification by ethnicity showed significantly increased odds ratios for association of the MBL codon 54 B variant with SLE in African, Asian, and Caucasian cohorts.

CONCLUSION

Meta-analysis of all available studies on MBL polymorphisms and SLE shows that MBL variant alleles such as MBL exon 1 codon 54 B, promoter -550 L, and promoter -221 X are SLE risk factors. This association is robust and persists after incorporation of data from our 2 cohorts in which the association failed to reach significance.

Apoptotic cells, autoantibodies, and the role of HMGB1 in the subcellular localization of an autoantigen

A current model for the evolution of systemic lupus erythematosus hypothesizes that there is a genetic predisposition coupled with an environmental or infectious trigger. This study investigated whether apoptotic cells given with a proinflammatory signal could induce features of lupus. Balb/c mice were injected with an apoptotic Balb/c-derived myeloid cell line, J774.1, either with or without the DNA-binding protein HMGB1 for five injections over 16 days in an IACUC approved study. Mice were sacrificed at 6 weeks and 12 weeks after treatment. Renal disease was assessed by immunofluorescence and autoantibodies were defined by ELISA. Western blotting was performed to characterize autoantigens. Mice injected with apoptotic cells developed antibodies to histones, SSA, ssDNA, and phospholipids. Antibodies to SSA and ssDNA persisted; however, antibodies to histones, and phospholipid declined at 12 weeks. IgG deposits in the kidney were detected at 6 weeks and persisted through 12 weeks primarily in animals that received both apoptotic cells and HMGB1. Autoantibodies in mice were diverse but the mice that received apoptotic cells developed particularly high titer antibodies to an unknown 78kDa protein. This protein became externalized on the surface of J774.1 cells in the presence of HMGB1. Mice that received apoptotic J774.1 cells with HMGB1 developed more extensive renal IgG deposition. While the mechanism is uncertain, an important effect of HMGB1 was to alter the subcellular distribution of a major autoantigen, making the autoantigen accessible for immune responses. This is the first description of an inflammatory stimulus altering the immunologic availability of a potential autoantigen.

Polymorphisms of complement receptor 1 and interleukin-10 genes and systemic lupus erythematosus: a meta-analysis

A number of studies have tested the association of the complement receptor 1 (CR1) and Interleukin-10 (IL10) polymorphisms with systemic lupus erythematosus (SLE), but reported conflicting results. The aim of the study is to explore whether the CR1 and IL10 genes are associated with SLE susceptibility. We surveyed studies on the CR1 and IL10 polymorphisms and SLE using comprehensive Medline search and review of the references. A meta-analysis was conducted in a fixed effects model or random effects model based on between-study heterogeneity. Eighteen comparisons from 13 studies were included in the CR1 meta-analysis and a total of 16 separate comparisons were used for the IL10 meta-analysis. The CR1 meta-analysis showed no significant association of the CR1 functional polymorphisms with SLE. In contrast, the S structural variant of the CR1 showed a significant association (OR=1.544, 95% CI, 1.217-1.959, P<0.001). Stratification by ethnicity indicated that the CR1 S variant was associated with SLE in Caucasians (OR=1.667, 95% CI, 1.193-2.357, P=0.003). The IL10 meta-analysis showed a significant association between SLE and the G11 allele of IL10.G (OR=1.279, 95% CI; 1.027-1.593, P=0.028) in whole populations, and IL10 promoter -1082G allele was associated with SLE in Asians (OR=1.358, 95% CI; 1.015-1.816, P=0.039). In conclusion, the CR1 meta-analysis revealed the association of the S structural variant of the CR1 with SLE and the IL10 meta-analysis showed the association of IL10.G11 allele and SLE in whole populations and the association between promoter -A1082G polymorphism and SLE in Asians.

Protective Molecules–C-Reactive Protein (CRP), Serum Amyloid P (SAP), Pentraxin3 (PTX3), Mannose-Binding Lectin (MBL), and Apolipoprotein A1 (Apo A1), and Their Autoantibodies: Prevalence and Clinical Significance in Autoimmunity

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload, and may initiate an autoimmune response. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein (CRP) and serum amyloid-P (SAP), and the long pentraxin-3 (PTX3), which are all involved in innate immunity and in acute-phase responses. Mannan-binding lectin (MBL) is an activator of the complement system, and Apolipoprotein A-1 (Apo A-1) is pivotal in the cholesterol homeostasis and has anti-inflammatory properties. In addition to their role in innate immunity and inflammation, each of these five proteins participates in the removal of damaged and apoptotic cells. In this review, we discuss the clinical significance of different levels of these proteins, their role in the induction or protection from autoimmunity, and the presence of specific autoantibodies against them in the different autoimmune diseases.

Flow cytometric assay for determination of FcgammaRIIIA-158 V/F polymorphism

A single nucleotide polymorphism (SNP) of the FCGR3A gene results in two allotypes of Fcgamma receptor IIIA (FcgammaRIIIA) with valine (V) or phenylalanine (F) at amino acid 158. Since the FcgammaRIIIA-158 V/F polymorphism is associated with the efficacy of monoclonal antibody (mAb) treatment and a risk factor for autoimmune disease, widely applicable methods to assess the SNP are needed. We developed a novel flow cytometric test for this polymorphism using a mAb that recognized only the FcgammaRIIIA-158 V allele (MEM-154) together with a mAb that detected both FcgammaRIIIA-158 alleles (3G8). The expression of both FcgammaRIIIA epitopes on natural killer (NK) cells from 37 healthy donors were measured and compared to the FCGR3A genotype determined by a 5' nuclease assay. FcgammaRIIIA expression levels in individuals with identical FCGR3A genotypes varied considerably, resulting in overlapping immunofluorescences by both 3G8 and MEM-154 between FcgammaRIIIA-158 V/F allotypes. However, the ratio between fluorescences measured using those mAbs in a single individual predicted the FCGR3A genotype with 100% sensitivity and specificity. The novel flow cytometric assay for the FcgammaRIIIA-158 V/F polymorphism that is based on the MEM-154/3G8 fluorescence ratio requires commercially available reagents and a three-color flow cytometer only.

Update on human systemic lupus erythematosus genetics

PURPOSE OF REVIEW

Susceptibility to systemic lupus erythematosus (SLE) has a genetic component. In recent years, nine complete genome scans using family collections that differ greatly in ethnic compositions and geographic locations have identified several strong, confirmed SLE susceptibility loci. Evidence implicating individual gene polymorphisms (or haplotypes) within some of the linked intervals has been reported. This review highlights recent findings that may lead to the identification of putative genes and new insights in the pathogenesis of SLE.

RECENT FINDINGS

Eight of the best-supported SLE susceptibility loci are 1q23, 1q25-31, 1q41-42, 2q35-37, 4p16-15.2, 6p11-21, 12p24, and 16q12. These are chromosomal regions exhibiting genome-wide significance for linkage in single studies and suggestive evidence for linkage in other samples. Linkage analyses conditioning on pedigrees in which one affected member manifesting a particular clinical condition have also yielded many chromosomal regions linked to SLE. The linked interval on chromosome 6p has been narrowed to 0.5 approximately 1.0 Mb (million basepairs) of 3 MHC class II containing risk haplotypes in white subjects. Cumulative results have shown that hereditary deficiencies of complement component C4A (a MHC class III gene) confer risk for SLE in almost all ethnic groups studied. The FcgammaR genes (located at 1q23) have been convincingly demonstrated to play an important role in susceptibility to SLE (and/or lupus nephritis). The evidence for the intronic single nucleotide polymorphism of program cell death gene 1 (PDCD1 at 2q37) to confer susceptibility is promising but not yet compelling. Within several established susceptibility loci, evidence for association of positional candidate genes is emerging.

SUMMARY

Further replications of linkage and association are the immediate task. The respective contribution of each susceptibility gene, relationships between genotypes and phenotypes, and potential interactions between susceptibility gene products need to be elucidated. This line of investigation is now well poised to provide novel insights into how genetic variants can affect functional pathways leading to the development of SLE.

Current advances in the human lupus genetics

Genetic predisposition has been firmly established as a key element in susceptibility to systemic lupus erythematosus (SLE). During the past three decades, association studies have assessed many genes for potential roles in predisposing to SLE. These studies have identified a few risk factors including hereditary deficiency of complement components, major histocompatibility complex class II alleles, and allelic variants for the Fc portion of IgG (FCGR) genes. In recent years, a few groups have completed linkage analyses in data sets from families containing multiple members affected with SLE. Results from these initial genome scans are encouraging; approximately eight chromosomal regions have been identified exhibiting evidence for significant linkage to SLE and have been confirmed using independent cohorts (1q23, 1q25-31, 1q41-42, 2q35-37, 4p16-15.2, 6p11-21, 12q24, and 16q12), suggesting the high likelihood of the presence of one or multiple SLE susceptibility genes at each locus. Another approach of linkage analyses conditioned on pedigrees where one affected member manifesting a particular clinical condition has also identified many chromosomal regions linked to SLE. Within several established susceptibility loci, evidence for association of positional candidate genes is emerging. Within 2q35-37, an intronic single nucleotide polymorphism (SNP) of the positional candidate gene program cell death 1 gene has been associated with SLE susceptibility. The SLE-associated SNP affects a transcription factor, RUNX1, binding site. Recently, SNPs of novel positional candidate genes that influence RUNX1 binding motifs have also been associated with other autoimmune diseases, suggesting the possibility of a common theme shared among susceptibility genes for autoimmune diseases. In the coming years, susceptibility genes responsible for the observed linkage will be identified, and will lead to further delineating genetic pathways involved in susceptibility to SLE.

The potential role of mannan-binding lectin in the clearance of self-components including immune complexes

Mannan-binding lectin (MBL) is a pattern recognition receptor in the innate immune system. It recognizes certain sugar residues arranged in a pattern that enables MBL to bind with sufficient strength. Such sugar patterns are common on the surface of many microorganisms, and MBL has therefore been considered to be an agent that can discriminate between self and nonself. There is, however, increasing evidence supporting that MBL, like many membrane-bound C-type lectin-like receptors, also helps to dispose of various outworn or abnormal body components. Most self-components are protected with sialic acid or galactose that disrupt the pattern of the sugars that MBL can bind, but MBL may be significantly involved in the elimination of self-components that have lost these protective terminal residues. The role of MBL in the clearance of invading pathogens has previously been thoroughly reviewed. Here, we review some findings that support the notion that MBL may contribute to noninflammatory removal of immune complexes and abnormal cells by the reticuloendothelial system. Defects in this clearance mechanism may cause an accumulation of potentially dangerous self-components, thereby increasing the likelihood of chronic inflammation and autoimmunity.

Fcgamma receptors in the initiation and progression of systemic lupus erythematosus

Systemic lupus erythematosus, a systemic autoimmune disorder, is characterized by the production of autoantibodies to nuclear constituents and inflammatory lesions in multiple organ systems. Although the pathogenesis of the disease is largely unknown, recent studies have suggested that disturbances in apoptosis and/or clearance of apoptotic cells may play an important role in the induction and perpetuation of autoantibody production. When autoantibodies subsequently complex to autoantigens present on apoptotic cells, ligation of Fcgamma receptor will result in inflammation and disease development. Indeed, mice deficient in activating Fcgamma receptors were protected against inflammation in models of immune complex-mediated autoimmune disease, whereas deletion of the inhibitory Fcgamma receptors increased autoantibody production and susceptibility to immune complex-induced inflammation. Additionally, functional polymorphisms in Fcgamma receptors were shown to be associated with development of human systemic lupus erythematosus. This review focuses on the role of Fcgamma receptors in the initiation of autoantibody production, inflammatory handling of immune complexes, and disease development in systemic lupus erythematosus.