SARS-CoV-2 Mutations and Variants: what do we know so far?

Abstract

With the circulation of the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOC), there is a worry that an increase in transmission, hospitalisations, and deaths may occur efficacy of some vaccines may be compromised. Recently the WHO has recommended the use of labels with letters of the Greek alphabet. Then, the variants of concern are now called Alpha, Beta, Gamma, and Delta. So that the classification of the variants is more accessible and more practical when they are discussed in non-scientific audiences. In addition, the variants can be classified into three large groups according to their clinical capacity to affect global public health: variants of interest (VOI), variants of concern (VOC), and High consequence variant (VOHC). This review aims to explore the molecular and epidemiological characteristics of SARS-CoV-2 mutations and variants.

Comparison of the Characteristics and Outcomes of COVID-19 Patients Treated by a Hospital-at-Home Service in Japan during the Alpha and Delta Waves

“…Since the coronavirus disease (COVID-19) pandemic began in December 2019 [ 1 ], most countries have experienced repeated waves caused by different strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with the number of patients increasing during each wave [ 2 , 3 ]. This led to hospital bed shortages, and many patients could not be admitted to hospitals for oxygen therapy or to receive immediate inpatient care [ 4 ].…”

Raman Fingerprints of the SARS-CoV-2 Delta Variant and Mechanisms of Its Instantaneous Inactivation by Silicon Nitride Bioceramics

“…Among the reported mutations, the E484Q one foresees the change from glutamic acid into glutamine, while the L452R one relates to the replacement of leucine by arginine. 6 An additional mutation, referred to as P681R, transforms a proline residue in the furin cleavage site of the spike protein into an arginine one. 9 According to the above notions, we looked first into specific spectral fingerprints of the arginine residue to replace those from the leucine one in the spectrum of the TY11-927 Delta variant as compared to that of the JPN/TY/WK-521 original isolate.…”

“…mutations reported for the spike protein of the TY11-927 (B.1.617.2) variant in Table ). Among the reported mutations, the E484Q one foresees the change from glutamic acid into glutamine, while the L452R one relates to the replacement of leucine by arginine . An additional mutation, referred to as P681R, transforms a proline residue in the furin cleavage site of the spike protein into an arginine one .…”

“… 95 In particular, the L452R spike receptor-binding motif substitution observed in the Delta variant confers on it increased infectivity by strengthening the interaction between the spike protein and the host-cell ACE2. 96 This mutation, which replaces leucine by arginine, 6 switches the charge from neutral to strongly positive at a key location in the reception binding subunit of the spike protein. Since the ACE2 receptor charge is negative, the L452R mutation makes the spike protein of the Delta variant extremely efficient in binding.…”

“…Studies from Japan and other countries , have shown a 2-fold infectious capacity of the Delta variant with respect to that of the Japanese isolate, with people infected with the Delta variant possessing a viral load more than 1200 times higher than that of people with the original SARS-CoV-2 isolate . Among the numerous (at least 15) mutations of the Delta variant, those creating the most concerns are the two simultaneous ones referred to as E484Q and L452R; the former contributes a significantly enhanced potential for binding to ACE2 and a better ability to evade the immune system, while the latter is instrumental in providing a higher affinity for the so-called “S” protein (prS) to ACE2 and in lowering the recognition capacity of the immune system . Notably, the appearance of both mutations in the same variant is unique so far .…”