A Paradigmatic Interplay between Human Cytomegalovirus and Host Immune System: Possible Involvement of Viral Antigen-Driven CD8+ T Cell Responses in Systemic Sclerosis

Virus-Induced MicroRNA Modulation and Systemic Sclerosis Disease

MicroRNAs (miRNAs) are short noncoding RNA sequences that regulate gene expression at the post-transcriptional level. They are involved in the regulation of multiple pathways, related to both physiological and pathological conditions, including autoimmune diseases, such as Systemic Sclerosis (SSc). Specifically, SSc is recognized as a complex and multifactorial disease, characterized by vascular abnormalities, immune dysfunction, and progressive fibrosis, affecting skin and internal organs. Among predisposing environmental triggers, evidence supports the roles of oxidative stress, chemical agents, and viral infections, mostly related to those sustained by beta-herpesviruses such as HCMV and HHV-6. Dysregulated levels of miRNA expression have been found in SSc patients compared to healthy controls, at both the intra- and extracellular levels, providing a sort of miRNA signature of the SSc disease. Notably, HCMV/HHV-6 viral infections were shown to modulate the miRNA profile, often superposing that observed in SSc, potentially promoting pathological pathways associated with SSc development. This review summarizes the main data regarding miRNA alterations in SSc disease, highlighting their potential as prognostic or diagnostic markers for SSc disease, and the impact of the putative SSc etiological agents on miRNA modulation.

Coinfection of Dermal Fibroblasts by Human Cytomegalovirus and Human Herpesvirus 6 Can Boost the Expression of Fibrosis-Associated MicroRNAs

Tissue fibrosis can affect every type of tissue or organ, often leading to organ malfunction; however, the mechanisms involved in this process are not yet clarified. A role has been hypothesized for Human Cytomegalovirus (HCMV) and Human Herpesvirus 6 (HHV-6) infections as triggers of systemic sclerosis (SSc), a severe autoimmune disease causing progressive tissue fibrosis, since both viruses and antiviral immune responses toward them have been detected in patients. Moreover, HCMV or HHV-6A infection was reported to increase the expression of fibrosis-associated transcriptional factors and miRNAs in human dermal fibroblasts. However, it is unlikely that they have separate effects in the infected host, as both viruses are highly prevalent in the human population. Thus, our study aimed to investigate, by quantitative real-time PCR microarray, the impact of HCMV/HHV-6A coinfection on the expression of pro-fibrotic miRNAs in coinfected cells, compared to the effect of single viruses. The results showed a possible synergistic effect of the two viruses on pro-fibrotic miRNA expression, thus suggesting that HCMV and HHV-6 may enhance each other and cooperate at inducing enhanced miRNA-driven fibrosis. These data may also suggest a possible use of virus-induced miRNAs as novel diagnostic or prognostic biomarkers for SSc and its clinical treatment.

Human Cytomegalovirus and Human Herpesvirus 6 Coinfection of Dermal Fibroblasts Enhances the Pro-Inflammatory Pathway Predisposing to Fibrosis: The Possible Impact on Systemic Sclerosis

Systemic sclerosis (SSc) is a severe autoimmune disease likely triggered by genetic and environmental factors, including viral infections. Human cytomegalovirus (HCMV) and human herpesvirus 6A species (HHV-6A) have been associated with SSc, based on in vivo and in vitro evidence, but the data are still inconclusive. Furthermore, despite both viruses being highly prevalent in humans and able to exacerbate each other’s effects, no data are available on their joint effects. Hence, we aimed to study their simultaneous impact on the expression of cell factors correlated with fibrosis and apoptosis in in vitro coinfected fibroblasts, representing the main target cell type in SSc. The results, obtained by a microarray detecting 84 fibrosis/apoptosis-associated factors, indicated that coinfected cells underwent higher and more sustained expression of fibrosis-associated parameters compared with single-infected cells. Thus, the data, for the first time, suggest that HCMV and HHV-6A may cooperate in inducing alterations potentially leading to cell fibrosis, thus further supporting their joint role in SSc. However, further work is required to definitively answer whether β-herpesviruses are causally linked to the disease and to enable the possible use of targeted antiviral treatments to improve clinical outcomes.

Systemic sclerosis cutaneous expression: Management of skin fibrosis and digital ulcers

Systemic sclerosis is a connective tissue disease with cutaneous involvement. Clinical manifestations result from the balance of inflammations/autoimmunity process and fibrogenesis. Patients suffer from skin ulcers, non-ulcerative lesions including digital pitting scars, telangiectasias, subungual hyperkeratosis, abrasions, fissures, and subcutaneous calcinosis. A review about the pathophysiology of the disease, the physical examination of the patients, the instrumental assessment, and possible treatments is performed.

Insights into the knowledge of complex diseases: Environmental infectious/toxic agents as potential etiopathogenetic factors of systemic sclerosis

Systemic sclerosis (SSc) is a connective tissue disease secondary to three cardinal pathological features: immune-system alterations, diffuse microangiopathy, and fibrosis involving the skin and internal organs. The etiology of SSc remains quite obscure; it may encompass multiple host genetic and environmental -infectious/chemical-factors. The present review focused on the potential role of environmental agents in the etiopathogenesis of SSc based on epidemiological, clinical, and laboratory investigations previously published in the world literature. Among infectious agents, some viruses that may persist and reactivate in infected individuals, namely human cytomegalovirus (HCMV), human herpesvirus-6 (HHV-6), and parvovirus B19 (B19V), and retroviruses have been proposed as potential causative agents of SSc. These viruses share a number of biological activities and consequent pathological alterations, such as endothelial dysfunction and/or fibroblast activation. Moreover, the acute worsening of pre-existing interstitial lung involvement observed in SSc patients with symptomatic SARS-CoV-2 infection might suggest a potential role of this virus in the overall disease outcome. A variety of chemical/occupational agents might be regarded as putative etiological factors of SSc. In this setting, the SSc complicating silica dust exposure represents one of the most promising models of study. Considering the complexity of SSc pathogenesis, none of suggested causative factors may explain the appearance of the whole SSc; it is likely that the disease is the result of a multifactorial and multistep pathogenetic process. A variable combination of potential etiological factors may modulate the appearance of different clinical phenotypes detectable in individual scleroderma patients. The in-deep investigations on the SSc etiopathogenesis may provide useful insights in the broad field of human diseases characterized by diffuse microangiopathy or altered fibrogenesis.

Similarities between COVID-19 and systemic sclerosis early vasculopathy: A "viral" challenge for future research in scleroderma

OBJECTIVE

To review similarities between COVID-19 and systemic sclerosis (SSc) early vasculopathy to provide novel insights into both diseases.

METHODS

A narrative review of the literature supplemented with expert opinion.

RESULTS

There is clear evidence that the endothelium is at the centre stage in SSc and COVID-19, with endothelial cell activation/injury and dysfunction creating the crucial evolving step in the pathogenesis of both diseases. The angiotensin system has also been implicated in the early stages of both COVID-19 and SSc. Autoptic studies provide novel insights into the effects of SARS-CoV-2 on the endothelium. Normal endothelium and endothelial dysfunction in COVID-19 and SSc are discussed. It is debated whether SARS-CoV-2 infection triggers autoimmunity with production of autoantibodies which is of mechanistic interest because other viral illnesses are potentially involved in endothelial dysfunction and in SSc pathogenesis.

CONCLUSION

COVID-19 is due to a direct assault of SARS-CoV-2 on the vascular system as an acute infection, whereas SSc remains a chronic/sub-acute autoimmune disease of largely unknown etiology Further study and exploration of the SARS-CoV-2 pathogenic mechanisms might provide further useful milestones in the understanding of the early SSc pathogenesis.

Modulation of microRNome by Human Cytomegalovirus and Human Herpesvirus 6 Infection in Human Dermal Fibroblasts: Possible Significance in the Induction of Fibrosis in Systemic Sclerosis

Human cytomegalovirus (HCMV) and Human herpesvirus 6 (HHV-6) have been reportedly suggested as triggers of the onset and/or progression of systemic sclerosis (SSc), a severe autoimmune disorder characterized by multi-organ fibrosis. The etiology and pathogenesis of SSc are still largely unknown but virological and immunological observations support a role for these beta-herpesviruses, and we recently observed a direct impact of HCMV and HHV-6 infection on the expression of cell factors associated with fibrosis at the cell level. Since miRNA expression has been found profoundly deregulated at the tissue level, here we aimed to investigate the impact on cell microRNome (miRNome) of HCMV and HHV-6 infection in in vitro infected primary human dermal fibroblasts, which represent one of the main SSc target cells. The analysis, performed by Taqman arrays detecting and quantifying 754 microRNAs (miRNAs), showed that both herpesviruses significantly modulated miRNA expression in infected cells, with evident early and late effects and deep modulation (>10 fold) of >40 miRNAs at each time post infection, including those previously recognized for their key function in fibrosis. The correlation between these in vitro results with in vivo observations is strongly suggestive of a role of HCMV and/or HHV-6 in the multistep pathogenesis of fibrosis in SSc and in the induction of fibrosis-signaling pathways finally leading to tissue fibrosis. The identification of specific miRNAs may open the way to their use as biomarkers for SSc diagnosis, assessment of disease progression and possible antifibrotic therapies.

Apoptosis Disorder, a Key Pathogenesis of HCMV-Related Diseases

Human cytomegalovirus (HCMV) belongs to the β-herpesvirus family, which is transmitted in almost every part of the world and is carried by more than 90% of the general population. Increasing evidence indicates that HCMV infection triggers numerous diseases by disrupting the normal physiological activity of host cells, particularly apoptosis. Apoptosis disorder plays a key role in the initiation and development of multiple diseases. However, the relationship and molecular mechanism of HCMV-related diseases and apoptosis have not yet been systematically summarized. This review aims to summarize the role of apoptosis in HCMV-related diseases and provide an insight into the molecular mechanism of apoptosis induced by HCMV infection. We summarize the literature on HCMV-related diseases and suggest novel strategies for HCMV treatment by regulating apoptosis.

First report of HHV-8 viral load and seroprevalence of major blood-borne viruses in Iranian patients with systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is characterized by autoimmune manifestations, and viral infections may have a key role in the development and progression of it. This study aimed to investigate the seroprevalence of major blood-borne viruses and HHV-8 viral load in Iranian SSc patients.

METHODS

In this cross-sectional study, 90 patients with a confirmed history of SSc and 90 healthy blood donors were enrolled. The frequency of HHV-8, CMV, EBV, HIV, HBV, and HCV antibodies and HHV-8 viral load were evaluated by enzyme-linked immunosorbent assay and real-time PCR assay, respectively.

RESULTS

HHV-8 IgG antibody was diagnosed in 61 (67.8%) patients and 3 (3.3%) healthy individuals (p<0.0001), but its genomic DNA was not detected in the patients or healthy blood donors. CMV and EBV antibodies were detected in 100% and 88.9% of SSc patients without any significant difference with healthy population (p>0.05). None of the patients or healthy population was positive for HBsAg and HIVAb; however, HCVAb was detected in two patients.

CONCLUSION

According to the results, HHV-8 antibody was uniquely increased in SSc population while its frequency in healthy population was very low. Since none of the SSc patients were positive for HHV-8 genomic DNA, the high prevalence of HHV-8 antibody in this group was not related to the real history of infection. Therefore, antibody-mediated epitope mimicry can play a role to get the high rate of seropositivity and lead to pathogeneses of SSc. Besides, CMV and EBV viral load monitoring in SSc patients can help the physician to prescribe the viral drugs to suppress the viral replication and avoid the crucial effect of reactivation.

Human Cytomegalovirus and Autoimmune Diseases: Where Are We?

Human cytomegalovirus (HCMV) is a ubiquitous double-stranded DNA virus belonging to the β-subgroup of the herpesvirus family. After the initial infection, the virus establishes latency in poorly differentiated myeloid precursors from where it can reactivate at later times to cause recurrences. In immunocompetent subjects, primary HCMV infection is usually asymptomatic, while in immunocompromised patients, HCMV infection can lead to severe, life-threatening diseases, whose clinical severity parallels the degree of immunosuppression. The existence of a strict interplay between HCMV and the immune system has led many to hypothesize that HCMV could also be involved in autoimmune diseases (ADs). Indeed, signs of active viral infection were later found in a variety of different ADs, such as rheumatological, neurological, enteric disorders, and metabolic diseases. In addition, HCMV infection has been frequently linked to increased production of autoantibodies, which play a driving role in AD progression, as observed in systemic lupus erythematosus (SLE) patients. Documented mechanisms of HCMV-associated autoimmunity include molecular mimicry, inflammation, and nonspecific B-cell activation. In this review, we summarize the available literature on the various ADs arising from or exacerbating upon HCMV infection, focusing on the potential role of HCMV-mediated immune activation at disease onset.

Impact of Human Cytomegalovirus and Human Herpesvirus 6 Infection on the Expression of Factors Associated with Cell Fibrosis and Apoptosis: Clues for Implication in Systemic Sclerosis Development

Systemic sclerosis (SSc) is a severe autoimmune disorder characterized by vasculopathy and multi-organ fibrosis; its etiology and pathogenesis are still largely unknown. Herpesvirus infections, particularly by human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6), have been suggested among triggers of the disease based on virological and immunological observations. However, the direct impact of HCMV and/or HHV-6 infection on cell fibrosis and apoptosis at the cell microenvironment level has not yet been clarified. Thus, this study aimed to investigate the effects of HCMV and HHV-6 infection on the induction of pro-fibrosis or pro-apoptosis conditions in primary human dermal fibroblasts, one of the relevant SSc target cells. The analysis, performed by microarray in in vitro HCMV- or HHV-6-infected vs. uninfected cells, using specific panels for the detection of the main cellular factors associated with fibrosis or apoptosis, showed that both viruses significantly modified the expression of at least 30 pro-fibrotic and 20 pro-apoptotic factors. Notably, several recognized pro-fibrotic factors were highly induced, and most of them were reported to be involved in vivo in the multifactorial and multistep pathogenic process of SSc, thus suggesting a potential role of both HCMV and HHV-6.

Betaherpesvirus assembly and egress: Recent advances illuminate the path

The human betaherpesviruses, human cytomegalovirus (HCMV; species Human betaherpesvirus 5) and human herpesviruses 6A, 6B, and 7 (HHV-6A, -6B, and -7; species Human betaherpesviruses 6A, 6B, and 7) are highly prevalent and can cause severe disease in immune-compromised and immune-naive populations in well- and under-developed communities. Herpesvirus virion assembly is an intricate process that requires viral orchestration of host systems. In this review, we describe recent advances in some of the many cellular events relevant to assembly and egress of betaherpesvirus virions. These include modifications of host metabolic, immune, and autophagic/recycling systems. In addition, we discuss unique aspects of betaherpesvirus virion structure, virion assembly, and the cellular pathways employed during virion egress.

Functional Profile of Human Cytomegalovirus Genes and Their Associated Diseases: A Review

The human cytomegalovirus (HCMV), whose genome is 235 ± 1.9 kbp long, is a common herpesvirus. However, the functions of many of its genes are still unknown. HCMV is closely associated with various human diseases and infects 60-90% of the global population. It can infect various human cells, including fibroblasts, epithelial cells, endothelial cells, smooth muscle cells, and monocytes. Although HCMV infection is generally asymptomatic and causes subtle clinical symptoms, it can generate a robust immune response and establish a latent infection in immunocompromised individuals, including those with AIDS, transplant recipients, and developing fetuses. Currently available antivirals approved for the treatment of HCMV-associated diseases are limited by dose-limiting toxicity and the emergence of resistance; however, vaccines and immunoglobulins are unavailable. In this review, we have summarized the recent literature on 43 newly identified HCMV genes. We have described their novel functions on the viral replication cycle, latency, and host immune evasion. Further, we have discussed HCMV-associated diseases and current therapeutic targets. Our review may provide a foundational basis for studies aiming to prevent and develop targeted therapies for HCMV-associated diseases.

HHV-6A Infection and Systemic Sclerosis: Clues of a Possible Association

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, excessive extracellular matrix deposition, and fibrosis of the skin and internal organs. Several infectious agents, including human herpesvirus-6 (HHV-6), have been suggested as possible triggering factors, but a direct association is still missing. We characterized 26 SSc patients for the presence of HHV-6 in tissues and blood, the anti-HHV-6 response, HLA-G plasma levels, and KIR typing. Given the prominent role of endothelial cells (EC) in SSc pathogenesis, along with HHV-6 tropism for EC, we also investigated the expression of pro-fibrosis factors in HHV-6 infected EC. Results showed the presence of HHV-6A in skin biopsies, and an increased virus load was associated with disease severity and poor natural killer (NK) response against the virus, particularly in subjects exhibiting a KIR2 phenotype. HLA-G plasma levels were significantly higher in HHV-6A/B-KIR2 positive SSc patients and in vitro HHV-6A infection-induced pro-fibrosis factors expression in EC, supporting its role in the development of the fibrosing process. Our data suggest an association between virus infection/reactivation and disease, opening the way to future studies to understand the mechanisms by which HHV-6A might contribute to the multifactorial pathogenesis of SSc.

Retrotransposons shuttling genetic and epigenetic information from the nuclear to the mitochondrial compartment: Do they play a pathogenetic role in scleroderma?

Endogenous retroelements are a class of ancient defective viral insertions contained in the genome of host cells, where they account for up to 40% of all DNA. Centuries of co-existence in host genome have led to the development of immunotolerance to endogenous retroelements, most of which are defective and unable to replicate or transcribe functional proteins. However, given their capacity to move across the nuclear and mitochondrial genome and recombine, they could mix phenotypes and give rise to infections that may trigger innate and adaptive immune responses by sensing receptors capable of recognising foreign nucleic acids and proteins. It has recently been suggested that they play a role in the pathogenesis of autoimmune diseases on the grounds of their partial reactivation or the epigenetic control of host gene transcription. A number of studies have confirmed their contribution to the development of rheumatoid arthritis, multiple sclerosis and systemic lupus erythematosus, but there is still a lack of data concerning systemic sclerosis (SSc). Their role in the pathogenesis of SSc can be hypothesised on the basis of mitochondrial and nuclear chromatinic damage, and hyper-activation of the immune pathway involved in antiviral defense. SSc is characterised by genetic and immunological evidence of a viral infection but, as no viral agent has yet been isolated from SSc patients, the hypothesis that partial reactivation of endogenous retroviruses may trigger the disease cannot be excluded and deserves further investigation.

Catch me if you can: the arms race between human cytomegalovirus and the innate immune system

Human cytomegalovirus (HCMV), a common opportunistic pathogen of significant clinical importance, targets immunocompromised individuals of the human population worldwide. The absence of a licensed vaccine and the low efficacy of currently available drugs remain a barrier to combating the global infection. The HCMV's ability to modulate and escape innate immune responses remains a critical step in the ongoing search for potential drug targets. Here, we describe the complex interplay between HCMV and the host immune system, focusing on different evasion strategies that the virus has employed to subvert innate immune responses. We especially highlight the mechanisms and role of host antiviral restriction factors and provide insights into viral modulation of pro-inflammatory NF-κB and interferon signaling pathways.

Anti-Jo-1 Antibody-positive Interstitial Pneumonia in an Elderly Patient with Congenital Rubella Syndrome

A 71-year-old woman with congenital rubella syndrome (CRS) presented with prolonged cough. No physical findings suggested the presence of any connective tissue diseases. Chest computed tomography showed ground-glass opacities and consolidations in the bilateral lower lobes. She had elevated serum Krebs von den Lungen-6, hypoxemia and positive serum anti-Jo-1 antibody. Bronchoalveolar lavage fluid revealed lymphocytosis with a decreased CD4/CD8 ratio. A transbronchial lung biopsy specimen revealed organizing pneumonia. Based on a diagnosis of interstitial pneumonia with autoimmune features (IPAF), systemic corticosteroids were administered, and a good outcome was obtained. A possible relationship between CRS and IPAF is herein discussed.