An explanation of the pathogenesis of several autoimmune diseases in immuno-compromised individuals

Pathogen regulatory RNA usage enables chronic infections, T-cell exhaustion and accelerated T-cell exhaustion

Pathogens evade or disable cellular immune defenses using regulatory ribonucleic acids (RNAs), including microRNAs and long non-coding RNAs. Pathogenic usage of regulatory RNA enables chronic infections. Chronic infections, using host regulatory RNAs and/or creating pathogenic regulatory RNAs against cellular defenses, can cause T-cell exhaustion and latent pathogen reactivations. Concurrent pathogen infections of cells enable several possibilities. A first pathogen can cause an accelerated T-cell exhaustion for a second pathogen cellular infection. Accelerated T-cell exhaustion for the second pathogen weakens T-cell targeting of the second pathogen and enables a first-time infection by the second pathogen to replicate quickly and extensively. This can induce a large antibody population, which may be inadequately targeted against the second pathogen. Accelerated T-cell exhaustion can explain the relatively short median and average times from diagnosis to mortality in some viral epidemics, e.g., COVID-19, where the second pathogen can lethally overwhelm individuals' immune defenses. Alternatively, if an individual survives, the second pathogen could induce a very high titer of antigen-antibody immune complexes. If the antigen-antibody immune complex titer quickly becomes very high, it can exceed the immune system's phagocytic capability in immuno-deficient individuals, resulting in a Type III hypersensitivity immune reaction. Accelerated T-cell exhaustion in immuno-deficient individuals can be a fundamental cause of several hyperinflammatory diseases and autoimmune diseases. This would be possible when impaired follicular helper CD4+ T-cell assistance to germinal center B-cell somatic hypermutation, affinity maturation and isotype switching of antibodies results in high titers of inadequate antibodies, and this initiates a Type III hypersensitivity immune reaction with proteinase releases which express or expose autoantigens.

Therapeutic potential of tolerance-based peptide vaccines in autoimmune diseases

Autoimmune diseases are caused by the dysfunction of the body's immune regulatory system, which leads to the recognition of self-antigens and the destruction of self-tissues and is mediated by immune cells such as T and B cells, and affects 5-10% of the population worldwide. Current treatments such as non-steroidal anti-inflammatory drugs and glucocorticoids can only relieve symptoms of the disease and are accompanied by serious side effects that affect patient quality of life. The recent rise in antigen-specific therapies, especially vaccines carrying autoantigenic peptides, promises to change this disadvantage, where research has increased dramatically in the last decade. This therapy established specific immune tolerance by delivering peptide fragments containing disease-specific self-antigen epitopes to suppress excessive immune responses, thereby exerting a therapeutic effect, with high safety and specificity. This article presents the latest progress on the treatment of autoimmune diseases with autoantigen peptide vaccines. It includes the construction of peptide vaccine delivery system, the mechanism of inducing immune tolerance and its application.

Can Antinuclear Antibodies Have a Pathogenic Role in Systemic Sclerosis?

Systemic sclerosis (SSc) is a connective tissue disease characterized by extensive fibrosis of the skin and internal organs, associated with vasculopathy and autoimmune features. Antinuclear antibodies (ANA) are found in almost all SSc patients and constitute strong diagnosis and prognosis biomarkers. However, it remains unclear whether ANA are simple bystanders or if they can have a role in the pathophysiology of the disease. One might think that the nuclear nature of their targets prevents any accessibility to autoantibodies. Nevertheless, recent data suggest that ANA could be pathogenic or at least contribute to the perennation of the disease. We review here first the indirect clues of the contribution of ANA to SSc: they are associated to the disease subtypes, they may precede disease onset, their titer correlates with disease activity and severity, there is an association between molecular subsets, and some patients can respond to B-cell targeting therapy. Then, we describe in a second part the mechanisms of ANA production in SSc from individual genetic background to post-transcriptional modifications of neoantigens. Finally, we elaborate on the potential mechanisms of pathogenicity: ANA could be pathogenic through immune-complex-mediated mechanisms; other processes potentially involve molecular mimicry and ANA penetration into the target cell, with a focus on anti-topoisomerase-I antibodies, which are the most probable candidate to play a role in the pathophysiology of SSc. Finally, we outline some technical and conceptual ways to improve our understanding in this field.

Suppression of Aspergillus fumigatus Germination by Neutrophils Is Enhanced by Endothelial-Derived CSF3 Production

Infection with Aspergillus fumigatus can cause life-threatening diseases in immunocompromised patients with an unacceptable mortality rate. Angioinvasion is one of the features of severe invasive aspergillosis. Neutrophils are short-lived immune cells regulated by colony-stimulating factor 3 (CSF3) that play a key role in anti-fungal immune responses. To investigate the interactions between A. fumigatus and the host immune cells, such as neutrophils, we stimulated human umbilical vein endothelial cells (HUVECs) with the conidia of A. fumigatus, and co-cultured them with human neutrophils. Apoptosis and functions of neutrophils were analyzed. Our results showed that HUVECs upregulate the expression of CSF3, which could reduce the apoptosis of neutrophils while enhancing their functions. Lack of CSF3 was associated with enhanced apoptosis of neutrophils with impaired function. This work indicated that the CSF3 is required for neutrophil survival and function, at least in the early stages of A. fumigatus infection.

How major fungal infections can initiate severe autoimmune diseases

Several autoimmune diseases have long been linked to viral and bacterial infections. In contrast, the possibility of fungal infections causing autoimmune diseases has received almost no attention. However, major fungal infections can cause severe autoimmune diseases, by decreasing T_REG cells and increasing production of interleukin-23, CD4 T_H17 T-cells, interleukin-17 and other cytokines, including interleukin-22. Several factors can cause fungal infections, including antibiotic usage. Bacterial and fungal populations compete in mammalian oropharyngeal, respiratory, gastrointestinal, and genitourinary tracts. Antibiotic usage decreases bacteria and thereby favors fungal populations over bacterial populations. This leads to an explanatory hypothesis for the pathogenesis of severe autoimmune diseases by major fungal infections. The increase in fungal populations in individuals susceptible to major fungal infections can also explain the higher incidence of autoimmune diseases. CD4 T_H17 T-cells and certain interleukins can be one path of pathogenesis between major fungal infections and increased incidences of major autoimmune diseases, including type 1 diabetes, multiple sclerosis, and various types of arthritis.

Potential New Treatments for Kawasaki Disease, Its Variations, and Multisystem Inflammatory Syndrome

The causation of Kawasaki disease has been a medical mystery for over 54 years. However, the causations of Kawasaki disease, its variations, and COVID-19-associated Multisystem Inflammatory Syndrome have been recently explained to involve high replication rate viral infections. In a subset of patients, the extensive antigen-antibody immune complexes that are not quickly cleared by phagocytosis will create a type III hypersensitivity immune reaction. The subsequent release of proteases and other enzymes and the expression or exposure of new immunogenic antigens due to protease attacks on basement membranes of epithelial cells or endothelial cells in blood vessels will induce new autoantibodies and cause Kawasaki disease, its variations, and COVID-19-related Multisystem Inflammatory Syndrome. There is now increasing evidence that a viral infection of a large surface area of tissue, such as the respiratory tract, gastrointestinal tract or blood vessels, and a resultant type III hypersensitivity immune reaction is the most plausible explanation for the causations of Kawasaki disease, its variations, and COVID-19-related Multisystem Inflammatory Syndrome. Furthermore, an improved understanding of these causations also suggests several potential new treatments which can be more effective.