Abstract
The human population is currently facing the third and possibly the worst pandemic caused by human coronaviruses (CoVs). The virus was first reported in Wuhan, China, on 31 December 2019 and spread within a short time to almost all countries of the world. Genome analysis of the early virus isolates has revealed high similarity with SARS-CoV and hence the new virus was officially named SARS-CoV-2. Since CoVs have the largest genome among all RNA viruses, they can adapt to many point mutation and recombination events; particularly in the spike gene, which enable these viruses to rapidly change and evolve in nature. CoVs are known to cross the species boundaries by using different cellular receptors. Both animal reservoir and intermediate host for SARS-CoV-2 are still unresolved and necessitate further investigation. In the current review, different aspects of SARS-CoV-2 biology and pathogenicity are discussed, including virus genetics and evolution, spike protein and its role in evolution and adaptation to novel hosts, and virus transmission and persistence in nature. In addition, the immune response developed during SARS-CoV-2 infection is demonstrated with special reference to the interplay between immune cells and their role in disease progression. We believe that the SARS-CoV-2 outbreak will not be the last and spillover of CoVs from bats will continue. Therefore, establishing intervention approaches to reduce the likelihood of future CoVs spillover from natural reservoirs is a priority.
Highlights
The outbreak was caused by SARS-CoV-2, which is highly antigenically and genetically similar to SARS-CoV-1 [3]
Little knowledge is currently available on the host immune response against SARSCoV-2 and the immunopathogenesis during COVID-19
The cascade of host response against SARS-CoV-2 is initiated by tissue resident alveolar epithelial cells and macrophages by activation of host pattern-recognition receptors (PRRs) that detect the released virus-associated molecular patterns (PAMPs)
Summary
Coronaviruses (CoVs) have long been known to infect human and animals causing a variety of diseases that affect the respiratory airways, intestine, liver, heart, kidneys, and nervous system [1]. According to the World Health Organization (WHO), the outbreak that was caused by SARS-CoV-1 affected 8096 cases in 29 countries and costed 774 (9.56%) lives. The outbreak was caused by SARS-CoV-2, which is highly antigenically and genetically similar to SARS-CoV-1 [3]. Both SARS-CoV-1 and SARS-CoV2 share some features; (i) they use the same cellular receptor ACE2, (ii) their internal fusion peptides of the S protein are identical, (iii) they have the same genomic organization with. (ii) S protein and its role in virus evolution and adaptation through receptor usage, (iii) possible ways of virus transmission, (iv) the immune response and its role in SARS-CoV-2 pathogenicity
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