Drug Development for the Management of Corona Viruses: Insights from Natural Antiviral Agents

Abstract

Coronaviruses (CoVs) are enveloped viruses that cause multiple respiratory and intestinal infections in humans and animals. 1 The term 'coronavirus' refers to the crown-like appearance of CoVs under electron microscope due to spike projections from the membrane. 2 These viruses were first described in the 1960s from patients with respiratory infections like the common cold. 3 Since then, several human coronaviruses (HCoVs) have been identified including the HCoV-Hong Kong University 1 (HKU1), HCoV-NL63; severe acute respiratory syndrome (SARS)-CoV; and Middle East respiratory syndrome (MERS)-CoV. 3 CoVs belong to the subfamilies Coronavirinae and Torovirinae of the family Coronaviridae in the order Nidovirales. 4 Based on phylogeny, they are divided into four genera as α-CoV, β-CoV, γ-CoV and δ-CoV. 5 The beta-CoV genus is further subdivided into four lineages (A, B, C, and D) 1 (Figure 1). Mammalian coronavirus include HCoV-229E and HCoV-NL63 which belong to the α-coronavirus class as well as HCoV-HKU1, SARS-CoV, MERS-CoV and HCoV-OC43 which are β-coronaviruses; while avian coronavirus is the γ-coronavirus and δ-coronavirus. 3 The novel coronavirus, 2019-nCoV, that caused the current global COVID-19 pandemic was first identified in December 2019 in the Wuhan region (Hubei Province) of China. Since then, the Coronavirus Study Group (CSG) of the International Committee on Taxonomy of Viruses has formally designated the virus as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 6