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Alpha-B.1.1.7, Beta-B.1.351, Gamma-P.1 and Delta-B.1.617.2 variants of SARS-CoV-2 express multiple mutations in the spike protein (S). These may alter the antigenic structure of S, causing escape from natural or vaccine-induced immunity. Beta is particularly difficult to neutralize using serum induced by early pandemic SARS-CoV-2 strains and is most antigenically separated from Delta. To understand this, we generated 674 mAbs from Beta infected individuals and performed a detailed structure-function analysis of the 27 most potent mAbs: one binding the spike N-terminal domain (NTD), the rest the receptor binding domain (RBD). Two of these RBD-binding mAbs recognise a neutralizing epitope conserved between SARS-CoV-1 and -2, whilst 18 target mutated residues in Beta: K417N, E484K, and N501Y. There is a major response to N501Y including a public IgVH4-39 sequence, with E484K and K417N also targeted. Recognition of these key residues underscores why serum from Beta cases poorly neutralizes early pandemic and Delta viruses., Graphical Abstract, Liu et al. generated 674 antibodies from patients infected with the SARS-CoV-2 Beta variant. 18 out of 27 most potent neutralizing antibodies isolated target the 3 mutations present in the receptor binding domain of this variant. This underscores the poor neutralization by Beta serum of early pandemic and Delta viruses.

Terminating the SARS-CoV-2 pandemic relies upon pan-global vaccination. Current vaccines elicit neutralizing antibody responses to the virus spike derived from early isolates. However, new strains have emerged with multiple mutations: P.1 from Brazil, B.1.351 from South Africa and B.1.1.7 from the UK (12, 10 and 9 changes in the spike respectively). All have mutations in the ACE2 binding site with P.1 and B.1.351 having a virtually identical triplet: E484K, K417N/T and N501Y, which we show confer similar increased affinity for ACE2. We show that, surprisingly, P.1 is significantly less resistant to naturally acquired or vaccine induced antibody responses than B.1.351 suggesting that changes outside the RBD impact neutralisation. Monoclonal antibody 222 neutralises all three variants despite interacting with two of the ACE2 binding site mutations, we explain this through structural analysis and use the 222 light chain to largely restore neutralization potency to a major class of public antibodies., Structural and functional analysis of the P.1 variant of SARS-CoV-2 from Brazil reveals less resistance to antibodies generated from natural infection or vaccination compared to another similar variant, B.1.351. A monoclonal antibody mAb 222 is able to neutralize all three variants (P.1, B.1.351 and B.1.1.7), with its light chain able to restore neutralization potency to broad group of antibodies.

SARS-CoV-2 has undergone progressive change with variants conferring advantage rapidly becoming dominant lineages e.g. B.1.617. With apparent increased transmissibility variant B.1.617.2 has contributed to the current wave of infection ravaging the Indian subcontinent and has been designated a variant of concern in the UK. Here we study the ability of monoclonal antibodies, convalescent and vaccine sera to neutralize B.1.617.1 and B.1.617.2 and complement this with structural analyses of Fab/RBD complexes and map the antigenic space of current variants. Neutralization of both viruses is reduced when compared with ancestral Wuhan related strains but there is no evidence of widespread antibody escape as seen with B.1.351. However, B.1.351 and P.1 sera showed markedly more reduction in neutralization of B.1.617.2 suggesting that individuals previously infected by these variants may be more susceptible to reinfection by B.1.617.2. This observation provides important new insight for immunisation policy with future variant vaccines in non-immune populations., The B.1.617 lineage of SARS-CoV-2, especially the delta strain that is B.1.617.2 has contributed to the wave of infection in the Indian subcontinent. Structural and serological analyses show no evidence of antibody escape but individuals previously infected with either the B.1.351 (beta) and P.1 (gamma) variants are likely more susceptible to reinfection by the delta strain. Vaccines based on B.1.1.7 (alpha) are likely to provide the broadest protection against current variants.

SummaryTerminating the SARS-CoV-2 pandemic relies upon pan-global vaccination. Current vaccines elicit neutralizing antibody responses to the virus spike derived from early isolates. However, new strains have emerged with multiple mutations: P.1 from Brazil, B.1.351 from South Africa and B.1.1.7 from the UK (12, 10 and 9 changes in the spike respectively). All have mutations in the ACE2 binding site with P.1 and B.1.351 having a virtually identical triplet: E484K, K417N/T and N501Y, which we show confer similar increased affinity for ACE2. We show that, surprisingly, P.1 is significantly less resistant to naturally acquired or vaccine induced antibody responses than B.1.351 suggesting that changes outside the RBD impact neutralisation. Monoclonal antibody 222 neutralises all three variants despite interacting with two of the ACE2 binding site mutations, we explain this through structural analysis and use the 222 light chain to largely restore neutralization potency to a major class of public antibodies.

The race to produce vaccines against SARS-CoV-2 began when the first sequence was published, and this forms the basis for vaccines currently deployed globally. Independent lineages of SARS-CoV-2 have recently been reported: UK–B.1.1.7, South Africa–B.1.351 and Brazil–P.1. These variants have multiple changes in the immunodominant spike protein which facilitates viral cell entry via the Angiotensin converting enzyme-2 (ACE2) receptor. Mutations in the receptor recognition site on the spike are of great concern for their potential for immune escape. Here we describe a structure-function analysis of B.1.351 using a large cohort of convalescent and vaccinee serum samples. The receptor binding domain mutations provide tighter ACE2 binding and widespread escape from monoclonal antibody neutralization largely driven by E484K although K417N and N501Y act together against some important antibody classes. In a number of cases it would appear that convalescent and some vaccine serum offers limited protection against this variant., Structure-function analysis of the SARS-CoV-2 variant B.1.351 using serum samples from convalescent and vaccinated individuals reveals how mutations in the viral spike protein result in tighter binding to the receptor ACE2 and allow escape from monoclonal antibody neutralization.

SARS-CoV-2 has caused over 2M deaths in little over a year. Vaccines are being deployed at scale, aiming to generate responses against the virus spike. The scale of the pandemic and error-prone virus replication is leading to the appearance of mutant viruses and potentially escape from antibody responses. Variant B.1.1.7, now dominant in the UK, with increased transmission, harbours 9 amino-acid changes in the spike, including N501Y in the ACE2 interacting-surface. We examine the ability of B.1.1.7 to evade antibody responses elicited by natural SARS-CoV-2 infection or vaccination. We map the impact of N501Y by structure/function analysis of a large panel of well-characterised monoclonal antibodies. B.1.1.7 is harder to neutralize than parental virus, compromising neutralization by some members of a major class of public antibodies through light chain contacts with residue 501. However, widespread escape from monoclonal antibodies or antibody responses generated by natural infection or vaccination was not observed., The SARS-CoV-2 B.1.1.7 variant is not neutralized as easily as the original form of the virus. Some public antibodies cannot neutralize B.1.1.7, due to altered light chain contacts with residue 501. However, B.1.1.7 does not show widespread escape from monoclonal antibodies, natural antibody responses, or vaccines.