Serum antibody to retroviral gag proteins in systemic sclerosis

Antibody Response to HERV-K and HERV-W Envelope Epitopes in Patients with Myasthenia Gravis

Myasthenia gravis is an antibody-mediated autoimmune neurological disorder characterized by impaired neuromuscular junction transmission, resulting in muscle weakness. Recently, the involvement of Human Endogenous Retroviruses (HERVs) in the pathophysiology of different immune-mediated and neurodegenerative diseases, such as multiple sclerosis, has been demonstrated. We aimed to investigate potential immune system involvement related to humoral responses targeting specific epitopes of HERV-K and HERV-W envelope proteins in myasthenia gravis. Myasthenia gravis patients were recruited in the Neurology Unit, while healthy controls were selected from the Blood Transfusion Center, both affiliated with AOU Sassari. Highly immunogenic antigens of HERV-K and HERV-W envelope proteins were identified using the Immune Epitope Database (IEDB) online tool. These epitopes were utilized in enzyme-linked immunosorbent assays (ELISA) to detect autoantibodies in serum directed against these sequences. The study involved 39 Healthy Donors and 47 MG patients, further categorized into subgroups based on the presence of autoantibodies: MG-AchR Ab+ (n = 17), MG-MuSK Ab+ (n = 7), double seronegative patients (MG-DSN, n = 18), MG-LRP4 Ab + (n = 4), and one patient with no antibodies data (n = 1). Our findings revealed high levels of autoantibodies in myasthenia gravis patients directed against the HERV-K-env-su(19-37), HERV-K-env-su(109-126), HERV-K-env-su(164-186), HERV-W-env(93-108), HERV-W-env(129-14), and HERV-W-env(248-262) epitopes. Notably, these results remained highly significant even when patients were subdivided into MG-AchR Ab+ and MG-DSN subgroups. Correlation analysis further revealed significant positive associations between the antibody levels against HERV-K and HERV-W families in patients, suggesting a synergistic action of the two HERVs in the pathology context since this correlation is absent in the control group. This study marks the first identification of a specific humoral response directed against defined epitopes of HERV-K and HERV-W envelope proteins in myasthenia gravis patients. These findings lay the foundation for future investigations aimed at elucidating the molecular mechanisms driving this immune response. The detection of these autoantibodies suggests the potential for novel biomarkers, especially within the MG-DSN patient subgroup, addressing the need for new biomarkers in this population.

SARS-CoV-2 and human retroelements: a case for molecular mimicry?

Background

The factors driving the late phase of COVID-19 are still poorly understood. However, autoimmunity is an evolving theme in COVID-19’s pathogenesis. Additionally, deregulation of human retroelements (RE) is found in many viral infections, and has also been reported in COVID-19.

Results

Unexpectedly, coronaviruses (CoV) – including SARS-CoV-2 – harbour many RE-identical sequences (up to 35 base pairs), and some of these sequences are part of SARS-CoV-2 epitopes associated to COVID-19 severity. Furthermore, RE are expressed in healthy controls and human cells and become deregulated after SARS-CoV-2 infection, showing mainly changes in long interspersed nuclear element (LINE1) expression, but also in endogenous retroviruses.

Conclusion

CoV and human RE share coding sequences, which are targeted by antibodies in COVID-19 and thus could induce an autoimmune loop by molecular mimicry.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-022-01040-2.

Autoantibodies Against Unmodified and Citrullinated Human Endogenous Retrovirus K Envelope Protein in Patients With Rheumatoid Arthritis

OBJECTIVE

Autoantibodies against proteins encoded by human endogenous retrovirus K (HERV-K) have been reported in patients with rheumatoid arthritis (RA), but their relevance, if any, has remained unresolved. We revisited this question and tested if such autoantibodies may react with citrullinated epitopes on the envelope (Env) protein of HERV-K.

METHODS

Immunoblotting and ELISAs were conducted with unmodified Env protein and with Env citrullinated by protein arginine deiminase 4 (PAD4). Sera from 100 patients with RA, plasma from 32 patients with juvenile idiopathic arthritis (JIA), and healthy adult and pediatric controls were included. Antibody reactivity was evaluated for correlations with clinical and laboratory variables of the patients.

RESULTS

We replicated and expanded upon published data suggesting that patients with RA or JIA have autoantibodies against HERV-K Env, some with high titers. Anti-HERV-K antibodies correlated with cigarette smoking and with circulating myeloperoxidase-DNA complexes indicative of nonapoptotic neutrophil cell death. Further, most of the patients with RA, but not those with JIA, had autoantibodies that reacted more strongly with Env that was citrullinated by PAD4. These anticitrullinated Env autoantibodies correlated with seropositivity and tended to be higher in patients with erosive disease.

CONCLUSION

Our data suggest that anti-HERV-K immunity is elevated in RA and JIA and may have a connection with pathogenic protein citrullination in RA.

How Retroviruses and Retrotransposons in Our Genome May Contribute to Autoimmunity in Rheumatological Conditions

More than 200 human disorders include various manifestations of autoimmunity. The molecular events that lead to these diseases are still incompletely understood and their causes remain largely unknown. Numerous potential triggers of autoimmunity have been proposed over the years, but very few of them have been conclusively confirmed or firmly refuted. Viruses have topped the lists of suspects for decades, and it seems that many viruses, including those of the Herpesviridae family, indeed can influence disease initiation and/or promote exacerbations by a number of mechanisms that include prolonged anti-viral immunity, immune subverting factors, and mechanisms, and perhaps “molecular mimicry”. However, no specific virus has yet been established as being truly causative. Here, we discuss a different, but perhaps mechanistically related possibility, namely that retrotransposons or retroviruses that infected us in the past and left a lasting copy of themselves in our genome still can provoke an escalating immune response that leads to autoimmune disease. Many of these loci still encode for retroviral proteins that have retained some, or all, of their original functions. Importantly, these endogenous proviruses cannot be eliminated by the immune system the way it can eliminate exogenous viruses. Hence, if not properly controlled, they may drive a frustrated and escalating chronic, or episodic, immune response to the point of a frank autoimmune disorder. Here, we discuss the evidence and the proposed mechanisms, and assess the therapeutic options that emerge from the current understanding of this field.

Toward Understanding of Environmental Risk Factors in Systemic Sclerosis [Formula: see text]

IMPORTANCE

Systemic sclerosis (SSc) is a severe, chronic, and incurable autoimmune fibrotic skin disease with significant extracutaneous involvement. Low concordance rate in twin studies and unequal geographic distribution of SSc argues for importance of environment in disease initiation and progression.

OBJECTIVE

In this manuscript we provide a summary of all investigated potential external risk factors for SSc.

DATA SOURCES

A literature search in PubMed and EMBASE database was performed for studies published until January 1, 2020 by 2 reviewers (EN and LO) independently.

FINDINGS

Occupational and/or environmental exposures to silica and organic solvents are associated with increased incidence and severity of SSc. Exposure to epoxy resins, asbestos, and particulate air pollution favors increased risk of SSc, but data are based on limited number of observational studies. There is insufficient evidence to conclude an association between SSc development and other occupational (eg, welding fumes) or personal exposures (eg, smoking, vitamin D deficiency). Association of SSc with silicone breast implants has been disproven. Infectious pathogens (eg, Helicobacter pylori and angiotropic viruses) and dysbiosis seem to play a role in SSc development and severity, but their role remains to be clarified.

CONCLUSIONS AND RELEVANCE

It may be prudent to counsel our patients with SSc (or those at risk of SSc) to avoid occupations with exposure to silica, organic solvents, asbestos and epoxy resins; restraint from smoking, using cocaine or drugs with pro-fibrotic potential. While the association between low vitamin D and SSc remains to be confirmed, we believe that SSc patients should be encouraged to maintain healthy vitamin D levels as benefits outweigh the risks.

Seasonality and autoimmune diseases: The contribution of the four seasons to the mosaic of autoimmunity

Autoimmune diseases (ADs) are a heterogeneous groups of diseases that occur as a results of loss of tolerance to self antigens. While the etiopathogeneis remain obscure, different environmental factors were suggested to have a role in the development of autoimmunity, including infections, low vitamin D levels, UV radiation, and melatonin. Interestingly, such factors possess seasonal variation patterns that could influence disease development, severity and progression. Vitamin D levels which reach a nadir during late winter and early spring is correlated with increased disease activity, clinical severity as well as relapse rates in several disease entities including multiple sclerosis (MS), non-cutaneous flares of systemic lupus erythematosus (SLE), psoriasis, and rheumatoid arthritis (RA). Additionally, immunomodulatory actions of melatonin secretion ameliorate the severity of several ADs including MS and SLE. Melatonin levels are lowest during spring, a finding that correlates with the highest exacerbation rates of MS. Further, melatonin is postulated to be involved in the etiopathogenesis of inflammatory bowel diseases (IBD) through it influence on adhesion molecule and therefore transcription factor expression. Moreover, infections can mount to ADs through pro-inflammatory cytokine release and human antigen mimicry. Seasonal patterns of infectious diseases are correlated with the onset and exacerbation of ADs. During the winter, increased incidence of Epstein-Barr virus (EBV) infectious are associated with MS and SLE flares/onset respectively. In addition, higher Rotavirus infections during the winter precedes type 1 diabetes mellitus onset (T1DM). Moreover, Escherichia coli (E. coli) infection prior to primary biliary cirrhosis (PBC) and T1DM disease onset subsequent to Coxachievirus infections are seen to occur during late summer, a finding that correlate with infectious agents' pattern of seasonality. In this review, the effects of seasonality on the onset, relapses and activity of various ADs were discussed. Consideration of seasonal variation patterns of ADs can possibly provide clues to diseases pathogenesis and lead to development of new approaches in treatment and preventative care.

Do infections facilitate the emergence of systemic sclerosis?

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular obliteration, excessive extracellular matrix deposition, and fibrosis of the connective tissues of the skin, lungs, gastrointestinal tract, heart, and kidneys. Infections are believed to play a role in the immunopathogenesis of SSc. A number of infectious agents have been proposed as possible triggering factors in SSc. Homology between viruses and autoantibody targets suggests that molecular mimicry may play a role in the initiation of antibody response in disorders characterized by diffuse vascular disease, mainly SSc. Four pathogenic hypotheses have been proposed: molecular mimicry, endothelial cell damage, super-antigens, and microchimerism. Although several studies have provided important information linking infectious agents to SSc, a clear, direct association is still missing. It is very likely that the infectious agents are cofactors in a specific hormonal and environmental setting that mounts an immune reaction, which leads to the emergence of the disorder.

The role of infections in the immunopathogensis of systemic sclerosis--evidence from serological studies

Infections are believed to often play a role in the immunopathogenesis of autoimmune disorders; such is the case in systemic sclerosis (SSc). In order to evaluate the potential role infections may have on the pathogenesis of SSc, we assessed serological reactivity against various infectious agents in patients with SSc and compared them with healthy controls. Serological samples obtained from 80 patients with SSc were compared with 296 compatible healthy controls. Both groups were of European origin. All samples were tested for the presence of antibodies directed against hepatitis B virus, hepatitis C virus, toxoplasmosis, rubella, CMV, EBV, and Treponema pallidum. We applied Bio-Rad commercial and experimental kits to assess most antigens and ELISA assays to complete the panel. Patients with SSc had elevated IgM and IgG against Toxoplasma gondii and against CMV. Higher titers were also detected against the hepatitis B virus core protein (recombinant HBc antigen) using MONOLISA anti-HBc Plus commercial kit (Bio-Rad). A significantly higher rate of IgM antibodies against the capsid antigen of the EBV was detected in SSc patients compared with healthy controls, as well. These data demonstrate that antibodies against CMV, HBV, and toxoplasmosis were detected more often in patients with SSc. This association implies that infectious agents may have a role in disease pathogenesis and expression.

Systemic sclerosis and infections

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular obliteration, excessive extracellular matrix deposition and fibrosis of the connective tissues of the skin, lungs, gastrointestinal tract, heart, and kidneys. Numerous infectious agents (bacterial and viral) have been proposed as possible triggering factors (Parvovirus B19, Cytomegalovirus, Epstein-Barr virus, Retroviruses). Homology between viruses and autoantibody targets suggests that molecular mimicry may have a role in initiating antibody response in different disorders characterized by diffuse vascular disease, including SSc. Endothelial cell may be infected bacteria or viruses that play a particular role in inducing vasculitis. The pathogenic hypothesis include: a mechanism of molecular mimicry, the role played by endothelial cell damage, the presence of superantigens and the role of microchimeric cells. Although several studies provide important information linking infectious agents to SSc, a direct casual association between infections and SSc is still missing. In SSc viral products could synergize with other factors in the microenvironment predisposing to SSc development.

Systemic sclerosis: current views of its pathogenesis

Systemic sclerosis (SSc) is an autoimmune disorder of unknown etiology characterized by severe and often progressive cutaneous and visceral fibrosis, pronounced alterations in the microvasculature, and numerous cellular and humoral immune abnormalities. Clinically, SSc is very heterogeneous, encompassing a spectrum ranging from mild limited forms of skin sclerosis with minimal internal organ involvement to severe skin and multiple internal organ fibrosis. Mortality and morbidity in SSc are very high and are directly related to the extent of the fibrotic and microvascular alterations. A better understanding of the pathogenesis of this incurable disorder will help to better target and design effective therapy in the future.

Endogenous retroviruses in systemic lupus erythematosus: candidate lupus viruses

Although the etiology of systemic lupus erythematosus (SLE) remains unclear, there is substantial circumstantial evidence that the development of SLE is dependent on environmental, genetic, and retroviral factors. SLE patients produce high titer antibodies to various retroviral proteins, including Gag, Env, and Nef of HIV and HTLV, in the absence of overt retroviral infection. We review the factors linking HERVs to SLE and consider the various processes utilized by endogenous retroviruses in the etiopathogenesis of SLE. In particular, we consider the role of HTLV-1-related endogenous sequence (HRES-1) in SLE. We propose that molecular mimicry between HRES-1 and the small ribonucleoprotein complex initiates the production of autoantibodies, leading to immune complex formation, complement fixation, and pathological tissue deposition.

Human retroviral sequences associated with extracellular particles in autoimmune diseases: epiphenomenon or possible role in aetiopathogenesis?

Publications describing retroviral sequences associated with extracellular particles in Sjögren's syndrome or systemic lupus erythematosus, multiple sclerosis, and type I diabetes present novel arguments and raise complex questions about eventual relationships between retroviruses and autoimmunity. They are presented and discussed in the present review, preceded by an overview of the biology of retroviral elements.

Antiretroviral antibodies: implications for schizophrenia, schizophrenia spectrum disorders, and bipolar disorder

BACKGROUND

Some retroviral antigens share structural homology within a group of related retroviruses. It is possible that antibodies directed against one virus may cross-react with antigens from a different virus in the group.

METHODS

Using this principle, the human immunodeficiency virus 1 (HIV-1) Western blot assay was used as an available source of human retroviral antigens to screen serum samples from an archived collection to ascertain whether there was an association between serum antiretroviral antibodies and mental illnesses.

RESULTS

A statistically significant proportion (28/54, 52%) of patients suffering from psychiatric disorders had serum antibodies that recognized at least one antigen present on the blot, culminating in indeterminate HIV-1 tests. The majority of the reactive samples were directed against the HIV-1 group antigens p24 and p17. These findings contrast with those of nonpsychiatric patients, who had 4/16 (25%) indeterminate blots.

CONCLUSIONS

The results suggest exposure to retroviral antigens related to those of HIV-1 in subpopulations of schizophrenic, schizophrenic spectrum disorder, and bipolar disorder patients.

Reactivity of sera from systemic lupus erythematosus and Sjögren's syndrome patients with peptides derived from human immunodeficiency virus p24 capsid antigen

We have previously demonstrated that about one-third of patients with either Sjögren's syndrome (SS) or systemic lupus erythematosus (SLE) react to human immunodeficiency virus (HIV) p24 core protein antigen without any evidence of exposure to, or infection with, HIV itself. Herein, we further characterize the specificity of this reaction using enzyme-linked immunosorbent assay to peptides representing fragments of p24. Characteristic epitope-specific profiles were seen for SS and SLE patients. SS patients had significantly increased responses to peptides F (p24 amino acids 69 to 86) and H (amino acids 101 to 111) and diminished reactivity to peptides A (amino acids 1 to 16) and P (amino acids 214 to 228). SLE patients had increased reactivity to peptides E (amino acids 61 to 76), H, and P. Utilization of peptide P hyporeactivity as the criterion to select for SS patients results in a screen that is moderately sensitive (64%) and specific (79.3%). Adding hyperreactivity to one other peptide (F or H) as an additional criterion yields an expected decrease in sensitivity (to 41%) while increasing specificity (to 93.1%). All sera-reactive peptides from regions of known structure of HIV p24 were located in the apex of the p24 molecule. Thus, the specificity of the peptide reactivities described here indicates a specific pattern of a nonrandom cross-reactivity between HIV type 1 p24 and autoimmune sera which may be partially syndrome specific. The future focus of our work will be to optimize assays of the peptide as diagnostic tools.

Antiribonucleoprotein antibodies in children with HIV infection: a comparative study with childhood-onset systemic lupus erythematosus

A number of clinical and laboratory features of HIV infection are found in systemic lupus erythematosus (SLE). The objective of this study was to analyze the presence of circulating antibodies to small nuclear ribonucleoproteins (snRNP) in both diseases. Sera from 44 HIV-infected children, from 22 patients with childhood-onset SLE, and from 50 healthy children were studied. Anti-snRNP antibodies were detected by ELISA using recombinant and affinity-purified nuclear antigens, by counterimmunoelectrophoresis (CIE), and by immunoblotting using extractable nuclear antigens. Results included the detection of anti-snRNP antibodies by ELISA in 30 HIV-infected patients (68.1%) and 19 SLE patients (86.3%). These antibodies were directed against U1-RNP (61.3% and 77.2%, respectively), Sm (29.5% and 54.5%, respectively), 60 kDa Ro/SS-A (47.7% and 50%, respectively), and La/SS-B proteins (18.1% and 9%, respectively). None of the HIV-infected children and 11 SLE patients (50%) showed anti-snRNP antibodies by CIE. None of the HIV-infected patients showed anti-70 kDa U1-RNP or anti-D-Sm antibodies by immunoblotting. No differences between the two groups were noted on the presence of nonprecipitating anti-snRNP antibodies. No such reactivities were observed among the normal sera tested. The authors concluded that nonprecipitating anti-snRNP antibodies in HIV-infected children are as frequent as in childhood-onset SLE. The significance of these antibodies is not clear at present. Although polyreactive and low-affinity antibodies and a mechanism of molecular mimicry may explain these results, a specific stimulation of B cells by nuclear antigens could not be excluded.

Pathogenesis of scleroderma. Collagen

It is now evident that persistent overproduction of collagen and other connective tissue macromolecules results in excessive tissue deposition, and is responsible for the progressive nature of fibrosis in SSc. Up-regulation of collagen gene expression in SSc fibroblasts appears to be a critical event in the development of tissue fibrosis. The coordinate transcriptional activation of a number of extracellular matrix genes suggests a fundamental alteration in the regulatory control of gene expression in SSc fibroblasts. Trans-acting nuclear factors that bind to cis-acting elements in enhancer and promoter regions of the genes modulate the basal and inducible transcriptional activity of the collagen genes. The identity of the nuclear transcriptional factors that regulate normal collagen gene expression remains to be firmly established, and to date, no alterations in the level or in the activity of such DNA binding factors has been demonstrated in SSc fibroblasts. In addition to important interactions between fibroblasts and the extracellular matrix, cytokines and other cellular mediators can positively and negatively influence fibroblast collagen synthesis. Some of these signaling molecules may have physiologic roles, and their aberrant expression, or altered responsiveness of SSc fibroblasts to them, may result in the acquisition of the activated phenotype. The rapid expansion of knowledge regarding the effects of cytokines on extracellular matrix synthesis has led to an appreciation of the enormous complexity of regulatory networks that operate in the physiologic maintenance of connective tissue and which may be responsible for the occurrence of pathologic fibrosis. The ubiquitous growth factor TGF beta is the most potent inducer of collagen gene expression and connective tissue accumulation yet discovered. The expression of TGF beta in activated infiltrating mononuclear cells suggests a role for this cytokine as a mediator of fibroblast activation in SSc. Furthermore, the recognition that TGF beta is capable of inducing its own expression in a variety of cell types, coupled with the demonstration that a subpopulation of SSc dermal fibroblasts produces TGF beta, indicates the existence of a possible autocrine loop whereby lymphocyte-derived TGF beta in early SSc not only signals biosynthetic activation of fibroblasts in a paracrine manner, but autoinduces endogenous TGF beta production by the target fibroblasts themselves. Such an autocrine loop involving TGF beta may explain the persistent activation of collagen gene expression in SSc fibroblasts, and could be responsible for the progressive nature of fibrosis in SSc. Numerous other cytokines, as well as cell-matrix interactions, also modify collagen gene expression and can significantly influence the effects of TGF beta. Although their physiologic function in tissue remodeling or their involvement in abnormal fibrogenesis has not yet been conclusively demonstrated, the study of the biologic effects of these cytokines may provide important clues to understanding the pathogenesis of SSc, and to the development of rational drug therapy aimed at interrupting the abnormal fibrogenic process in this disease.

Biochemical characterization of the reverse transcriptase of a human intracisternal A-type particle (HIAP)

The discovery of novel human intracisternal A-type particle (HIAP) that may be associated with the autoimmune disease Sjŏgren's syndrome has been previously reported. Although the HIAP retrovirus has been shown to be antigenically related to HIV-1, the viruses were distinguishable by different hydrodynamic mobilities through a sucrose gradient by morphology and intracellular location, and by differing divalent cation requirements for their in vitro reverse transcriptase (RT) reactions. In this report, additional biochemical characteristics are provide that further differentiate the HIAP RT from HIV-1 RT. Data are also presented that distinguish the HIAP RT from the known cellular DNA polymerases.

Retroviruses and systemic lupus erythematosus

In some animal models of autoimmune diseases the roles of exogenous and endogenous retroviruses are clearly defined. In ungulates caprine arthritis encephalitis virus, equine infectious anemia virus or Maedi-Visna virus infections cause a well-defined autoimmune disease and the appearance of seropositivity of the animals is of diagnostic value. Likewise, in MRL lpr/lpr mice insertion of a retrotransposon into the fas gene could clearly be shown to cause survival of autoreactive lymphocytes. Despite intensive research in this field over a long period of time, molecular data on retroviral involvement in either etiology or pathology of human SLE and other autoimmune rheumatic diseases remain rather scarce. However, the analysis of retroviral antibodies and antigens in human autoimmune disease is undoubtedly important with regard to the search for retroviruses as disease-causing agents.

Epitope specificity of anti-HIV antibodies in human and murine autoimmune diseases

This article reports the HIV epitope specificity of antibodies present in the sera of HIV-negative patients with autoimmune diseases. Recombinant gp120 and a panel of synthetic peptides derived from the amino acid consensus sequences of either related (gp120, gp41, and p24) or unrelated (Mage-1, necdin, heat shock protein [65 kDa], and amyloid) HIV proteins were tested by a specific ELISA. The first set of experiments performed on four patients with Sjögren's syndrome (SjS) and four patients with systemic lupus erythematosus (SLE) revealed a significant anti-gp120 antibody reactivity in autoimmune patients when compared to healthy HIV-negative controls. Moreover, such binding could be almost completely inhibited by preincubation with free gp120. A significant anti-p24 reactivity was observed in 18 of 29 sera from SjS patients and in 13 of 25 sera from SLE patients, while anti-gp41 was observed only in 3 of 14 SjS and in 2 of 20 SLE-affected patients. Similar analyses were performed in the murine model of autoimmunity, showing that sera from MRL/lpr mice were able to bind all HIV-related peptides in an age-dependent manner. The analysis of a panel of HIV-unrelated peptides showed that SLE as well as MRL/lpr sera bind both HIV-related and unrelated peptides, while SjS sera failed to do so, revealing the polyclonal nature of the SLE and MRL/lpr repertoire and the oligoclonal reactivity of SjS sera. This is also supported by inhibition experiments, which showed that SLE, but not SjS, sera competitively inhibited the binding to HIV gp120 peptide of sera from autoimmune MRL/lpr mice. These results indicate that an overlapping polyclonal repertoire is present in both SLE and MRL/lpr sera, while the oligoclonal specificity of SjS antibodies may be related to a specific, nonpolyclonal, activation against putative retroviral antigens.

Autoimmunity, apoptosis defects and retroviruses

Autoimmunity and AIDS both share the common feature of increased expression of retroviral protein products and abnormal apoptosis of immune cells (81). This leads to a more global immunomodulatory defect (82-84). The challenge in the future will be to devise compounds that can either regulate the effect of the retroviral products on apoptosis, or that can inhibit apoptosis pathways in order to restore normal immune system function.

Polymerase chain reaction fails to incriminate exogenous retroviruses HTLV-I and HIV-1 in rheumatological diseases although a minority of sera cross react with retroviral antigens

OBJECTIVES

To investigate the presence of antibodies to HTLV and HIV retroviral antigens in the rheumatological diseases rheumatoid arthritis (RA), polymyositis/dermatomyositis (PM/DM), primary Sjögren's syndrome (pSS), and systemic lupus erythematosus (SLE), and to use polymerase chain reaction (PCR) to seek these exogenous retroviruses in proviral form in cellular DNA from these patients.

METHODS

Thirty patients with active RA, 13 with PM, 14 with pSS and five with SLE were recruited and their sera tested for antibodies to HTLV-I in enzyme linked immunosorbent assay (ELISA) and Western blot analysis. Seropositivity to HIV-1 was also sought. DNA was extracted from peripheral blood lymphocytes, synovial tissue and muscle biopsies and tested by polymerase chain reaction using consensus primers for HTLV-I and HIV-1.

RESULTS

In HTLV-I ELISA, nine rheumatological sera (4/30 RA, 3/13 PM/DM and 2/5 SLE patients) were considered positive; 14 from pSS patients and 30 from normal subjects were negative. In a control group which included osteoarthritis, Crohn's disease and bacterial endocarditis patients, only two of 80 proved positive in this system. Validation of these sera by Western blotting generally revealed weak reactivity against a variety of HTLV-I antigens. PCR of genomic DNA derived from patients' peripheral blood mononuclear cells did not reveal the presence of HTLV-I and HIV-1 target sequences.

CONCLUSIONS

This study shows that PCR precludes HTLV-I and HIV-1 infection as causative agents in these rheumatological diseases although a minority of patients possess antibodies that are weakly cross-reactive with retroviral antigens.

Retroviruses and autoimmune rheumatic diseases

In autoimmune rheumatic diseases, retroviruses have been repeatedly discussed as important etiologic factors. However, despite a considerable amount of indirect evidence that retroviruses might indeed be involved in triggering or perpetuating autoimmune rheumatic diseases, clear cut direct evidence is still missing. Studies on arthropathies associated with HIV-1 or HTLV-1 infection as well as new experimental animal models like the Tax transgene mice and new data from the MLR/lpr mouse model might help to answer the questions how and by what mechanisms retroviral infection may lead to autoimmune rheumatic diseases. From data obtained in the MLR/lpr mouse it seems obvious that a potential link of retroviruses, apoptosis and autogenes to autoimmune diseases opens exciting new approaches to the study of rheumatic disease pathogenesis.

Antibodies to retroviral proteins in autoimmune connective tissue disease. Relation to clinical manifestations and ribonucleoprotein autoantibodies

OBJECTIVE

To study the relationship between antibodies that recognize human retroviral proteins and the presence of clinical features and ribonucleoprotein antibodies in patients with autoimmune connective tissue diseases (CTDs).

METHODS

Antibodies against native human immunodeficiency virus type 1 (HIV-1) and human T cell leukemia/lymphoma virus type I, recombinant HIV-1 Nef protein, and ribonucleoprotein antigens were determined by immunoblot of sera from 65 prospectively studied patients with definite or suspected CTDs of autoimmune type.

RESULTS

Antibodies to retroviral proteins (ARP), most frequently to HIV Gag proteins p55 and p24, were found in 64% of 22 patients with systemic lupus erythematosus (SLE), in 63% of 8 patients with discoid LE (DLE), in 75% of 8 patients with mixed connective tissue disease (MCTD), and in 26% of 19 individuals with chronic biologically false-positive (CBFP) seroreactions, but not in 8 patients with subacute cutaneous lupus erythematosus. No clear correlation of ARP with antibodies to any specific small nuclear RNP antigen was observed. The most striking finding was that recurrent infections, both in LE patients and in those with CBFP reactions and widespread, acral discoid skin lesions, occurred significantly more often in ARP-positive patients.

CONCLUSION

The occurrence of antibodies reacting with human retroviral proteins is associated with severe skin lesions and recurrent infections in SLE, DLE, and MCTD patients, and with a disposition toward developing systemic disease in CBFP reactors.

Heterogeneous expression and coordinate regulation of endogenous retroviral sequences in human peripheral blood mononuclear cells

This study examines the expression of human endogenous retroviral or retroviral-like (ERV) sequences in peripheral blood mononuclear cells (PBMC). Probes to 12 human ERV were used in Northern analyses of 38 patients with autoimmune muscle diseases and 31 blood donor controls. All patients and controls expressed multiple classes of ERV RNA. This expression was quite heterogenous: for each of the nine ERV classes for which expression was detected, some individuals showed high RNA levels whereas others showed low levels. ERV expression was independent of disease and autoantibody production. Statistical analysis of densitometric data indicated that expression of several classes of ERV was coordinately regulated. ERV expression in individual patients showed coordinate fluctuations with time. These studies demonstrate the heterogeneity and coordinate regulation of human ERV expression. To evaluate whether ERV expression might be affected by lymphocyte activation, PBMC were cultured with or without lymphocyte mitogens before RNA extraction. These studies demonstrated complex changes in ERV expression after lymphocyte activation. Murine ERV have several immunoregulatory activities. If human ERV have analogous effects, their heterogeneous expression and association with lymphocyte activation may have important biologic consequences.

Southwestern Internal Medicine Conference: The Many Faces of Scleroderma

This review integrates the clinical aspects of systemic sclerosis (SSc; scleroderma) and scleroderma-like conditions with new knowledge of the control of blood vessel tone and the role of anoxia in the activation of connective tissues leading to fibrosis. Serologic tests, high resolution computed tomographic scanning, bronchoalveolar lavage, and physiologic assessment of pulmonary gas diffusion are compared as diagnostic tools and as means of quantitating internal organ involvement. Treatment of Raynaud's disease and phenomenon, management of scleroderma renal crisis, and new means for improving gastrointestinal function with octreotide, the somatostatin analogue, also are discussed. The relationship between idiopathic forms of SSc and eosinophilic fasciitis/eosinophilia-myalgia syndrome caused by L-tryptophan ingestion and the scleroderma-like disease associated with silicone breast implants also is discussed.

A flexible, efficient, checkerboard immunoblot system for the detection and semiquantitation of specific antinuclear antibodies

In this paper an uncomplicated method for the simultaneous detection and semiquantitation of 11 of the 12 commonly studied antinuclear antibodies (ANA) in a single run is described. This new application of checkerboard immunoblotting (CBIB) is based upon available technology and employs purified antigens which can be either purchased or produced in-house. CBIB requires no electronic instrument, can be formatted to meet the needs of the user, is rapidly performed, and has acceptable labor and materials costs. Data on the use of the method to examine available reference antisera is presented. CBIB has also proven practical for the clinical study of 18 sera, at two dilutions per membrane, for each set of specific antinuclear antibodies, also at two or more dilutions.