SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

Abstract

The SARS-CoV-2 B.1.617.2 (Delta) variant was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha) 1 . In vitro, B.1.617.2 is 6-fold less sensitive to serum neutralising antibodies from recovered individuals, and 8-fold less sensitive to vaccine-elicited antibodies as compared to wild type (WT) Wuhan-1 bearing D614G. Serum neutralising titres against B.1.617.2 were lower in ChAdOx-1 versus BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies against the receptor binding domain (RBD) and N-terminal domain (NTD). B.1.617.2 demonstrated higher replication efficiency in both airway organoid and human airway epithelial systems compared to B.1.1.7, associated with B.1.617.2 spike in a predominantly cleaved state compared to B.1.1.7. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralising antibody as compared to WT spike. Additionally we observed that B.1.617.2 had higher replication and spike mediated entry as compared to B.1.617.1, potentially explaining B.1.617.2 dominance. In an analysis of over 130 SARS-CoV-2 infected healthcare workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx-1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era. India's first wave of SARS-CoV-2 infections in mid-2020 was relatively mild and was controlled by a nationwide lockdown. Since easing of restrictions, India has seen expansion in cases of COVID-19 since March

A Single Dose of a Hybrid hAdV5-Based Anti-COVID-19 Vaccine Induces a Long-Lasting Immune Response and Broad Coverage against VOC

“…Moreover, studies with pseudoviruses and the authentic SARS-CoV-2-containing variant substitutions suggested that the neutralizing ability of the antibodies in sera raised after CoroVaxG.3 vaccination is only slightly reduced but overall largely preserved against the B.1.1.7, P.1 and B.1.617.2 lineages that are VOC-prevalent in Latin America [64]. This mild reduction in neutralization by a single dose of CoroVax.G3 vaccine-raised sera against the VOC is in the same range as that observed for sera of patients who received mRNA or adenoviral vector vaccines [65][66][67]; interestingly, one dose of the Pfizer or the Astra Zeneca vaccines induced almost undetectable levels of neutralizing antibodies against Delta [68].…”

Characterisation of vaccine breakthrough infections of SARS-CoV-2 Delta and Alpha variants and within-host viral load dynamics in the community, France, June to July 2021

“…* sublineages) variant. Delta was shown to spread faster than Alpha [1][2][3] and may be associated with higher virulence [4][5][6] and lower vaccine effectiveness [6,7] against symptomatic disease, especially with incomplete vaccination.…”

Rapid inactivation of SARS-CoV-2 by titanium dioxide surface coating

“…The coatings would need only periodic re-application depending on the amount of wear, for example 6-12 monthly, and would be widely available in the future. Such interventions are increasingly critical in conditions where viral variants with increased transmissibility are the new norm 14,[17][18][19] .…”