ABSTRACT
Coronavirus disease (COVID-19) is a viral infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus. The infection was reported in Wuhan, China, in late December 2019 and has become a major global concern due to severe respiratory infections and high transmission rates. Evidence suggests that the strong interaction between SARS-CoV-2 and patients' immune systems leads to various clinical symptoms of COVID-19. Although the adaptive immune responses are essential for eliminating SARS-CoV-2, the innate immune system may, in some cases, cause the infection to progress. The cytotoxic CD8+ T cells in adaptive immune responses demonstrated functional exhaustion through upregulation of exhaustion markers. In this regard, humoral immune responses play an essential role in combat SARS-CoV-2 because SARS-CoV-2 restricts antigen presentation through downregulation of MHC class I and II molecules that lead to the inhibition of T cell-mediated immune response responses. This review summarizes the exact pathogenesis of SARS-CoV-2 and the alteration of the immune response during SARS-CoV-2 infection. In addition, we've explained the exhaustion of the immune system during SARS-CoV-2 and the potential immunomodulation approach to overcome this phenomenon. Video Abstract.
Subject(s)
COVID-19 , Immunity, Innate , CD8-Positive T-Lymphocytes , China , Humans , SARS-CoV-2ABSTRACT
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) firstly emerged in Wuhan, China at the end of 2019. After going through the experimental process, the virus was named the novel coronavirus (2019-nCoV) by the World Health Organization (WHO) in February 2020 which has created a global pandemic. The coronavirus disease 2019 (COVID-19) infection is challenging the people who are especially suffering from chronic health problems such as asthma, diabetes, and heart disease or immune system deteriorating disorders, including cancers, Alzheimer's, etc. Other predisposing/risk factors consist of smoking and age (elderly people are at higher risk). The 2019-nCoV attacks epithelial cells in all organs, particularly epithelial cells in the lungs, resulting in viral pneumonia. The 2019-nCoV starts its invasion with the attachment and entry into the respiratory tract epithelial cells via Angiotensin-Converting Enzyme 2 (ACE2) receptors on the epithelial cells. The critical problem with 2019-nCoV is its ability in human to human asymptomatic transmission which causes the rapid and hidden spread of the virus among the population. Also, there are several reports of highly variable and tightly case-dependent clinical manifestations caused by SARS-CoV2, which made the virus more enigmatic. The clinical symptoms are varied from common manifestations which occurred in flu and cold, such as cough, fever, body-ache, trembling, and runny nose to severe conditions, like the Acute Respiratory Distress Syndrome (ARDS) or even uncommon/unusual symptoms such as anosmia, skin color change, and stroke. In fact, besides serious injuries in the respiratory system, COVID-19 invades and damages various organs, including the kidney, liver, gastrointestinal, and nervous system. Accordingly, to cut the transmission chain of disease and control the infection spread. One of the major solutions seems to be early detection of the carriers, particularly the asymptomatic people, with sensitive and accurate diagnostic techniques. Moreover, developing novel and appropriate therapeutic approaches will contribute to the suitable management of the pandemic. Therefore, there is an urgent necessity to make comprehensive investigations and study reviews about COVID-19, offering the latest findings of novel therapies, drugs, epidemiology, and routes of virus transmission and pathogenesis. In this review, we discuss new therapeutic outcomes and cover and the most significant aspects of COVID-19, including the epidemiology, biological features, organs failure, and diagnostic techniques.