Abstract
Some coronaviruses are zoonotic viruses of human and veterinary medical importance. The novel coronavirus, severe acute respiratory symptoms coronavirus 2 (SARS-CoV-2), associated with the current global pandemic, is characterized by pneumonia, lymphopenia, and a cytokine storm in humans that has caused catastrophic impacts on public health worldwide. Coronaviruses are known for their ability to evade innate immune surveillance exerted by the host during the early phase of infection. It is important to comprehensively investigate the interaction between highly pathogenic coronaviruses and their hosts. In this review, we summarize the existing knowledge about coronaviruses with a focus on antiviral immune responses in the respiratory and intestinal tracts to infection with severe coronaviruses that have caused epidemic diseases in humans and domestic animals. We emphasize, in particular, the strategies used by these coronaviruses to circumvent host immune surveillance, mainly including the hijack of antigen-presenting cells, shielding RNA intermediates in replication organelles, 2′-O-methylation modification for the evasion of RNA sensors, and blocking of interferon signaling cascades. We also provide information about the potential development of coronavirus vaccines and antiviral drugs.
Highlights
Coronaviruses cause highly contagious diseases in both humans and animals and have led to severe epidemics that have caused major public health threats, such as the severe acute respiratory symptom (SARS) outbreak in 2002−2003 [1], and Middle East respiratory syndrome coronavirus (MERS), which emerged in 2012 [2]
The results indicated that COVID-19 patients display robust innate immune responses with chemokine-dominated hypercytokinemia, such as elevated expression of chemokine (CXC motif) ligand 17 (CXCL17), CXCL8, CXCL1, CXCL2, and chemokine (CXC motif) receptor 2 (CXCR2), suggesting the importance of the recruitment of neutrophils and monocytes in controlling viral infection [68]
The mentioned coronaviruses bind to the antigen-presenting cells, such as dendritic cells (DCs), using the unique glycoproteins on their envelope, which facilitate the virus in breaking through the mucosal barrier and avoiding detection by the pattern-recognition receptors (PRRs) on the cellular membrane of the epithelium
Summary
Coronaviruses cause highly contagious diseases in both humans and animals and have led to severe epidemics that have caused major public health threats, such as the severe acute respiratory symptom (SARS) outbreak in 2002−2003 [1], and Middle East respiratory syndrome coronavirus (MERS), which emerged in 2012 [2]. At the very beginning of this new decade, a novel coronavirus, severe acute respiratory symptoms coronavirus 2 (SARS-CoV-2), emerged and caused a catastrophic pandemic of respiratory illness worldwide. During the period from December 2019 to 30 August 2020, the pandemic caused by the new coronavirus SARS-CoV-2 spread to 216 countries worldwide, infecting more than 24 million individuals, leading to 838,360 deaths, and severely crippling the worldwide economy [3]. Interferon (IFN) production is a fundamental process involved in the innate immune response to viral infection. These soluble antiviral cytokines can induce upregulation of an array of intracellular effectors of interferon-stimulated genes (ISGs) through the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signal pathways, such as Mx proteins, protein kinase PKR, and ISG15, Viruses 2020, 12, 1039; doi:10.3390/v12091039 www.mdpi.com/journal/viruses. We highlight how these different coronaviruses exploit multiple strategies to evade immune surveillance exerted by the host
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