Covid-19 and autoimmunity.

Abstract

Though the exact etiology of autoimmune diseases still remains unknown, there are various factors which are believed to contribute to the emergence of an autoimmune disease in a host including the genetic predisposition, the environmental triggers such as bacterial infections, including the gut microbiota, viral fungal and parasitic infections, as well as physical and environmental agents, hormonal factors and the hosts immune system dysregulation. All these factors interplay was coined by Shoenfeld et al., many years ago “The Mosaic of Autoimmunity” [[1], [2], [3], [4]]. The most prominent pathogenic viruses which have been proposed in the triggering and initiation of autoimmune diseases include: Parvovirus B19, Epstein-Barr-virus (EBV), Cytomegalovirus (CMV), Herpes virus-6, HTLV-1, Hepatitis A and C virus, and Rubella virus [[5], [6], [7], [8], [9], [10], [11]]. These viruses have been implicated in the initiation of chronic inflammatory or autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, Sjogren's syndrome, primary billiary cholangitis, multiple sclerosis, polymoysitis, uveitis, Henoch Schonlein Puprpura, Systemic Juvenile Idiopathic arthritis, systemic sclerosis, Hashimoto thyroiditis and autoimmune hepatitis [12,13]. Suggested mechanisms of induction of the autoimmunity include both molecular mimicry [14] as well as “bystander activation” whereby the infection may lead to activation of antigen presenting cells that may in turn activate pre-primed auto-reactive T-cells, thus leading to the production of pro-inflammatory mediators, which in turn may lead to tissue damage [15]. Alternative suggested mechanisms include epitope spreading as well as presentation of cryptic antigens [16]. Corona viruses represent a major group of viruses mostly affecting human beings through zoonotic transmission. In the past two decades, this is the third instance of the emergence of a novel coronavirus, after the severe acute respiratory syndrome (SARS) in 2003 and the Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012 [17,18]. In December 2019 a novel outbreak of a new strain of coronavirus infection emerged in Wuhan, China the SARS-CoV-2 or the Covid-19. The disease which was declared as a pandemic in early March 2020, is characterized by fever, dry cough, myalgia and or extreme fatigue, may be asymptomatic or with minimal flu-like constitutional symptoms leading to a favorable outcome in many instances. However, some of the patients encounter a severe pneumonia with sepsis leading to an acute respiratory distress syndrome (ARDS) with respiratory failure requiring mechanical ventilation, and at times accompanied by hyperferritinemia and multiple organ involvement including hematological, gastrointestinal, neurological and cardiovascular complications leading to death [[19], [20], [21], [22], [23]]. The ARDS described in up to 20% of Covid-19 cases, is reminiscent of the cytokine release syndrome-induced ARDS and secondary hemophagocytic lymphohistiocytosis (sHLH) observed in patients with SARS-CoV and MERS-CoV as well as in leukemia patients receiving engineered T cell therapy. These cases with Covid-19 are those who develop through the excessive cytokine release and the uncontrolled immune activation, the multiorgan failure with a grave prognosis [24,25].