NOVEL CORONAVIRUS (SARS-COV-2): MOLECULAR BIOLOGY, PATHOGENESIS, PATHOBIOLOGY AND ADVANCES IN TREATMENT OF COVID-19 PATIENTS– AN UPDATE

Abstract

The novel coronavirus (CoV), earlier named 2019-nCoV, and later as severe acute respiratory syndrome coronavirus - 2 (SARS-CoV-2) has now created havoc and panic across the globe by its severe ongoing pandemic. This virus has to date as of 23rd November 2020, killed nearly 1.4 million persons out of more than 59 million confirmed positive cases, while spreading rapidly in more than 215 countries and territories. Taxonomically, SARS-CoV-2 has been characterized in genus Betacoronavirus, which contains non-segmented positive-sense, single-stranded (ss) RNA genome of 30 kb. The first two open reading frames (ORFs), ORF1a and ORF1b, of SARS-CoV-2, encode 16 non-structural proteins (nsp1-nsp16), whereas other ORFs encodes four main structural proteins (sp) [spike (s) by ORF2, envelope (E) by ORF4, membrane (M) by ORF5, nucleoprotein (N) by ORF9], and accessory proteins essential for the virus fitness, pathogenesis and host immunity evasion. Sequence alignments of SARS-CoV-2 with genomes of various coronaviruses showed 58% identity in the non-structural protein (nsp)-coding region, 43% with the structural protein (sp)-coding region and 54% with the whole genome. The full-length genome sequence of the 2019-nCoV sample showed only up to 79.60% similarity with SARS CoV, but up to 96% similarity with bat coronavirus (bat coronavirus RaTG13). This gives strong evidence that 2019-nCoV has originated from the bat. The genomic and evolutionary evidence of another coronavirus species from pangolins also show higher similarity to SARS-CoV at the whole-genome level. Apart from RaTG13, Pangolin-CoV is the most closely related CoV to SARS-CoV-2. During infection, the viral S protein interacts with the receptor protein of the human cell membrane, known as angiotensin-converting enzyme II (ACE2). Presently, SARS-CoV-2 vaccines and drugs are not available, for which researchers are trying hard to develop to tackle rising tide of COVID-19- pandemic. Early diagnosis, contact tracing, strict prevention and control measures, biosecurity, personal biosafety, disinfection and sanitization practices, social distancing are aiding in prevention with SARS-CoV-2 infection. Boosting immunity by intaking the balanced and nutritious food, nutraceuticals, herbs, and following physical exercises along with avoiding stress conditions enhance the fighting power of the body against SARS-CoV-2 infection and limiting the severity of COVID-19. The present article describes salient knowledge on SARS-CoV-2 structure, genomic organization, pathogenesis, pathobiology, and advances and progress being made to treat COVID-19 patients.