SARS-CoV-2 - SYNOPTIC CHART OF THE MAIN CHARACTERISTICS OF VIRUS, PATHOGENESIS, IMMUNE RESPONSE, IMMUNOPROPHYLAXIS

Abstract

Coronaviruses (CoVs) are viruses of zoonotic origin, transmitted from person to person mainly via the respiratory tract. Seven types of CoVs have succeeded in making the leap from animals to humans. Among them, four produce the common cold, while the other three, more recently emerged CoVs, cause the Severe Acute Respiratory Syndrome (SARS) and exhibit a high epidemic/pandemic potential: SARS-CoV, Middle East Respiratory Syndrome (MERS)-CoV, and SARS-CoV-2. The new SARS-CoV-2 is the etiological agent of the current and unprecedented pandemic, associated with a unique pathology named Corona-virus Disease 2019 (COVID-19). These viruses belong to the Coronaviridae family - classified by ICTV (International Committee for Taxonomy of Viruses) in the fourth Class, that of enveloped viruses with a positive-strand RNA genome, infectious for both birds and mammals. As an airborne pathogen, its high infectivity is intensified by the widespread expression of its specific entry receptors (ACE-2, TMPRSS2) in various human organs and tissues, SARS-CoV-2 has spread rapidly from China throughout the whole world, causing numerous infections (approximately 128 million), with a relatively high lethality (approximately 2.8 million). The particular feature of the severe evolution of the SARS-CoV-2 infection is its association with Respiratory Distress Syndrome (ARDS) and Systemic Inflammatory Response Syndrome (SIRS), mainly in older patients or those with comorbidities. In the absence of a standard therapeutic protocol, the medical systems worldwide have been challenged to continuously improve the COVID-19 treatment, based on emerging data from rapidly initiated clinical trials. At the same time, specialists in virology, immunology, and vaccinology have collaborated at an unprecedented pace to design and implement effective SARS-CoV-2 vaccines. In this review we highlight the most important advances made in understanding the characteristics of SARS-CoV-2, including the viral replication cycle, as well as COVID-19 pathogenesis, immune responses mounted by the host following natural infection (with various forms, from moderate to severe and lethal ones) and vaccines.