Nicola Bassi

Infections and autoimmunity: the multifaceted relationship

Multiple factors are thought to contribute to the development of immune response to self, including differences in genotypes, hormonal milieu, and environmental factors. This review focuses on the pivotal role of infection in the induction of autoimmune disorders. Although the development of autoimmune phenomena linked to infections is a common finding, the onset of autoimmune diseases is a rare event, arising from a combination of genetic susceptibility and environmental factors. There are several mechanisms through which pathogens can initiate or perpetuate autoimmunity. Some of them are antigen‐specific, including molecular mimicry, expression of modified, cryptic, or new antigenic determinants, and superantigens. Others are nonspecific and collectively known as “bystander activation.” They include enhanced processing and presentation of self‐antigens, immune cell activation, cytokine release, and cell apoptosis/necrosis. Infections may also trigger organ‐specific autoimmune diseases, but studies carried out until now have provided conflicting and inconclusive results regarding the role of viral and bacterial agents. Infections and autoimmune diseases have multifaceted and multidirectional relationships. It has been suggested recently that infections cannot only induce or precipitate autoimmune diseases, but they may also protect from autoimmunity or even abrogate an ongoing autoimmune process depending on the interaction between microorganisms and host. Therefore, we should look at microorganisms, not only as causes of infections but also as potential agents able to modulate the immune system. On the other hand, numerous evidences have emerged regarding the higher susceptibility of autoimmune patients to infections, possibly as a result of immunosuppressive therapy and treatment with biologic agents.

Infections as triggers and complications of systemic lupus erythematosus

A growing body of experimental and clinical evidence supports the pivotal role of infections in the induction or exacerbation of systemic lupus erythematosus (SLE). Infections can be responsible for aberrant immune response leading to a loss of tolerance towards native proteins. Molecular mimicry, especially between Sm or Ro autoantigens and EBV Nuclear Antigen-1 response, as well as the over-expression of type 1 INF genes are among the major contributors to SLE development. On the other hand infections are very common in SLE patients, where they are responsible for 30-50% of morbidity and mortality. Several factors, either genetic, including complement deficiencies or mannose-binding lectin deficiency or acquired such as severe disease manifestations or immunosuppressant use, predispose SLE patients to infections. All types of infections, including bacterial, viral and opportunistic infections, have been reported and the most frequently involved sites of infections are the same as those observed in the general population, including respiratory, skin, and urinary tract infections. Some preventive measures could be adopted in order to reduce the rate of infections in SLE patients: i.e. screening for Mycobacterium tuberculosis and for some chronic viral infections before immunosuppressive treatment; adequate prophylaxes or drug adjustments when indicated, and pneumococcal and influenza vaccinations in patients with stable disease.

SLE diagnosis and treatment: when early is early.

Around 1980 antinuclear antibody testing became widely used in routine laboratory practice leading to a tapering in the lag time between SLE onset and diagnosis. Since then nothing relevant has been introduced which could help us in making the diagnosis of SLE earlier than now. Notably, there is increasing evidence that early diagnosis and treatment could increase SLE remission rate and improve patient prognosis. Although it has been shown that autoantibodies appear before clinical manifestations in SLE patients, currently we cannot predict which autoantibody positive subjects will eventually develop the disease. Thus, great effort should be made in order to identify new biomarkers able to improve our diagnostic potential. B lymphocyte stimulator (BLyS), anti-ribosomal P protein and anti-C1q antibodies are among the most promising. In recent years, some therapeutic options have emerged as appropriate interventions for early SLE treatment, including antimalarials, vitamin D, statins and vaccination with self-derived peptides. All these immune modulators seem to be particularly useful when introduced in an early stage of the disease.

Emerging and critical issues in the pathogenesis of lupus.

Systemic lupus erythematosus (SLE) is a multisystemic, autoimmune disease, encompassing either mild or severe manifestations. SLE was originally labeled as being an immune complex-mediated disease, but further knowledge suggested its pathogenesis is motlier than that, involving complex interactions between predisposed individuals and their environment. People affected with SLE have their immune system skewed toward aberrant self-recognition usually after encountering a triggering agent. Defeats in early and late immune checkpoints contribute to tolerance breakdown and further generation and expansion of autoreactive cell-clones. B and T cells play a master role in SLE, however clues are emerging about other cell types and new light is being shed on SLE autoantibodies, since some of them display really harmful potential (pathogenic antibodies), while others are just connected with disease development (pathological antibodies) and may even be protective. Autoantibody generation is elicited by abnormal apoptosis and inefficient clearance of cellular debris causing intracellular autoantigens (e.g. nucleosomes) to persist in the extracellular environment, being further recognized by autoreactive cells. Here we explore the complexity of SLE pathogenesis through five core issues, i.e. genetic predisposition, B and T cell abnormalities, abnormal autoantigen availability, autoantibody generation and organ damage, relying on current knowledge and recent insights into SLE development.

Autoantibodies in Polymyositis and Dermatomyositis

Inflammatory myopathies are a group of acquired diseases, characterized by immunoflogistic processes primarily involving the skeletal muscle. According to recent classification criteria, four major diseases have been identified: polymyositis (PM), dermatomyositis (DM), sporadic inclusion body myositis (IBM), and necrotizing autoimmune myositis (NAM). Autoantibodies can be found in the sera of most patients with myositis. Myositis-specific autoantibodies (MSAs) are markers of very specific disease entities within the spectrum of myositis, and target proteins involved in key processes of protein synthesis. Myositis autoantigens comprise the well-defined aminoacyl-tRNA synthetases, the Mi-2 helicase/histone deacetylase protein complex, and the signal recognition particle (SRP) ribonucleoprotein, together with novel targets such as TIF1-γ, MDA5, NXP2, SAE, and HMGCR. Recent studies suggest that autoantigens drive a B cell antigen-specific immune response in muscles. Interestingly, an increased expression of Jo-1 and Mi-2 in regenerating fibers in muscle biopsies from PM and DM patients compared to normal was demonstrated. Myositis autoantigen up-regulation was observed in neoplastic tissues, thus representing a potential link between cancer and autoimmunity in myositis. Non-immunological mechanisms seem to participate to the pathogenesis of inflammatory myopathies; induction of endoplasmic reticulum stress response in response to abnormal muscle regeneration and inflammation has recently been reported in patients with myositis. This review article provides an update of new emerging insights about the clinical and pathophysiologic role of principal autoantibodies in myositis.

Neurolupus is associated with anti-ribosomal P protein antibodies: An inception cohort study

OBJECTIVE Serum IgG antibodies (Abs) to phosphorylated ribosomal (P ribosomal) proteins have been inconsistently associated with neuropsychiatric manifestations in systemic lupus erythematosus (SLE). Our aim was to assess whether serum IgG Abs to ribosomal P proteins are associated with neuropsychiatric SLE. PATIENTS AND METHODS We examined an inception cohort of 219 SLE patients. Neuropsychiatric SLE manifestations were characterized using the American College of Rheumatology (ACR) definition. Serum Abs to P ribosomal proteins were searched for by immunoblotting. In a subgroup of patients, Abs were investigated also in cerebrospinal fluid (CSF). RESULTS Abs to P ribosomal proteins were detected in 45 (21%) patients, 23 of whom (51%) with neuropsychiatric involvement. Abs to P ribosomal protein were present both in serum and CSF. Abs to P ribosomal proteins significantly correlated with psychosis (p=0.017), mononeuropathy multiplex (p=0.040), malar rash (p=0.004), serum anti-Sm Abs (p=0.042), and lupus anticoagulant (p=0.036). SLE onset age was significantly younger in patients with Abs to P ribosomal proteins. Logistic regression analysis confirmed the relationship between Abs to P ribosomal proteins and psychosis, malar rash, SLE onset age and lupus anticoagulant. CONCLUSIONS Abs to ribosomal P proteins are associated with psychosis and might be associated with peripheral nervous system complications.

Serpins, Immunity and Autoimmunity: Old Molecules, New Functions

Serine protease inhibitors (serpins) are evolutionary old, structurally conserved molecules which encompass nearly all branches of life. More than 1,000 serpins were characterized to date which are subdivided into 16 subgroups (A–P) according to their common ancestry; among them, 37 are found in humans. Serpins were termed after their capability to inhibit serine proteases, but mounting evidence suggests that they may achieve a greater deal of functions, ranging from embryological growth to synaptic plasticity, development of both myeloid and lymphoid immune cells, and modulation of apoptosis. Serpins are mainly extracellular molecules, although some of them (namely, ov-serpins or clade B serpins) mostly act inside the cells, being either ubiquitously or tissue-specifically expressed. Among newly characterized serpin functions, regulation of cellular proliferation through apoptosis modulation and proteasome disturbance seems to play a major role. Accordingly, several serpins were found to be hyperexpressed in tumor cells. Indeed, apoptosis dysregulation is likely to be a cornerstone in both tumorigenesis and autoimmunity, since uncontrolled cellular viability results in tumor proliferation, while inefficient disposal of apoptotic debris may favor the rescue of autoreactive immune cells. Such a process was widely documented in systemic lupus erythematosus (SLE). Interestingly, alterations in the expression of some serpins, e.g., the ov-serpin SERPINB3, are being unraveled in patients affected with SLE and other autoimmune disorders, suggesting that a failure in serpin function might affect immune homeostasis and self-tolerance, thereby contributing to autoimmunity. Here, we provide an overview of serpin origin, function, and dysfunction, focusing on human serpins and ov-serpins, with a hub on SERPINB3.

OxLDL/β2GPI–anti-oxLDL/β2GPI complex and atherosclerosis in SLE patients

It has been demonstrated that atherosclerosis (ATS) is enhanced in autoimmune rheumatic diseases, such as systemic lupus erythematosus (SLE). The reason for this accelerated process is still debatable and, although traditional risk factors are more prevalent in SLE patients than in general population, they do not seem to fully explain the enhanced risk. ATS has the characteristics of an autoimmune chronic disease, involving both the innate and the adaptive immunity. Moreover, it satisfies the four criteria defining an autoimmune disease, proposed by Witebsky and Rose. It has been shown that some autoantibodies, including anti-oxLDL, anti-beta(2)GPI, anti-HSP60/65, and more recently anti-oxLDL/beta(2)GPI, play a key role in the pathogenesis of ATS. However the role of these autoantibodies in accelerated ATS in SLE patients is still controversial. In fact, some of them seem to be proatherogenic and other protective; moreover, it has been demonstrated that induced oral tolerance has a protective role against ATS. We have recently observed that the levels of oxLDL/beta(2)GPI antigenic complexes and their antibodies were higher in patients with SLE than in healthy subjects, but we did not find a clear association between oxLDL/beta(2)GPI complexes and IgG or IgM anti-oxLDL/beta(2)GPI autoantibodies and subclinical ATS in SLE patients. Many other studies are required to explain the role of autoantibodies in the pathogenesis of ATS in SLE patients, because the characteristics of SLE seem to mask their effects for atherogenesis.

Anti-SAE antibodies in autoimmune myositis: Identification by unlabelled protein immunoprecipitation in an Italian patient cohort.

INTRODUCTION Myositis specific autoantibodies (MSAs) are useful in the diagnosis of idiopathic inflammatory myopathies and in the definition of disease subsets. The aim of this study was to set up an unlabelled protein immunoprecipitation technique for MSA identification in the sera of myositis patients, in order to identify and investigate new antibody reactivity, undetectable by currently used methods. METHODS Sera of 183 patients with connective tissue diseases (75 adult dermatomyositis, 12 juvenile dermatomyositis, 43 polymyositis, 53 other connective tissue diseases) and 30 healthy controls were screened by an in-house procedure of unlabelled protein immunoprecipitation. In the same sera MSAs and myositis associated antibodies were determined by immunoblotting and immunoprecipitation for RNA. RESULTS The analytical specificity of unlabelled protein immunoprecipitation was demonstrated by testing reference sera with known antibody reactivity. Sera from five patients, affected with dermatomyositis (5/75=7%), immunoprecipitated two proteins of 40 and 90 kDa apparent molecular weights respectively, consistent with the subunits of the small ubiquitin like modifier activating enzyme heterodimer (SAE1/SAE2). The identity of putative SAE immunoprecipitated proteins was confirmed by immunoblotting on immunoprecipitates using commercial monospecific antibodies to SAE1 and SAE2. Major clinical features were compared between anti-SAE positive and negative patients. Interestingly, anti-SAE positive patients had mainly skin and muscle manifestations while dysphagia, interstitial lung disease, arthritis and constitutional symptoms were absent. CONCLUSIONS Unlabelled protein immunoprecipitation is a specific analytical approach, appropriate for the identification of the recently described anti-SAE autoantibody. We confirmed the role of anti-SAE antibody as marker of dermatomyositis.

IgG anti-pentraxin 3 antibodies in systemic lupus erythematosus

Objective To evaluate the prevalence and correlates of anti-pentraxin 3 (PTX3) antibodies in systemic lupus erythematosus (SLE). Methods Serum samples from 130 patients with SLE, 130 age- and sex-matched healthy subjects and 130 patients with other autoimmune rheumatic diseases (oARD) were analysed by home-made ELISAs using as substrate human recombinant PTX3 and two peptides, PTX3_1 and PTX3_2, obtained from the complete protein, identified as potential antigenic sites using the Lasergene DNA program (DNA Star). Inhibition tests were performed to evaluate potential interferences between bovine serum albumin or C-reactive protein and anti-PTX3 or anti-PTX3 peptides, and between antigens and antibodies. Statistical analysis was performed using receiving operating characteristics curves, the Fisher exact test, two-tailed t test and Pearson correlations. Results Patients with SLE had higher levels and prevalence of anti-PTX3, anti-PTX3_1 and anti-PTX3_2 antibodies than patients with oARD or healthy controls (p<0.001 for all). No differences were observed between patients with oARD and healthy controls. A correlation was found between anti-PTX3 and anti-PTX3_2 antibodies (r=0.615, p<0.001). No association was observed between these antibodies and disease activity. Univariate and multivariate analyses showed that anti-PTX3 and anti-PTX3_2 antibody levels and prevalence were higher in patients without glomerulonephritis and in patients positive for antiphospholipid antibody. All inhibition tests were negative apart from PTX3 against anti-PTX3 antibody or, to a lesser extent, against anti-PTX3_2 antibody, and PTX3_2 against anti-PTX3_2 antibody, all in a dose-dependent manner. Conclusions Anti-PTX3 antibodies are significantly prevalent in patients with SLE where they might provide protection from renal involvement. The antigenic properties of PTX3_2 peptide are similar to those of PTX3, suggesting its potential use in further analyses.