Broadly neutralizing antibodies against sarbecoviruses generated by immunization of macaques with an AS03-adjuvanted COVID-19 vaccine

Abstract

The rapid emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants that evade immunity elicited by vaccination has placed an imperative on the development of countermeasures that provide broad protection against SARS-CoV-2 and related sarbecoviruses. Here, we identified extremely potent monoclonal antibodies (mAbs) that neutralized multiple sarbecoviruses from macaques vaccinated with AS03-adjuvanted monovalent subunit vaccines. Longitudinal analysis revealed progressive accumulation of somatic mutation in the immunoglobulin genes of antigen-specific memory B cells (MBCs) for at least 1 year after primary vaccination. Antibodies generated from these antigen-specific MBCs at 5 to 12 months after vaccination displayed greater potency and breadth relative to those identified at 1.4 months. Fifteen of the 338 (about 4.4%) antibodies isolated at 1.4 to 6 months after the primary vaccination showed potency against SARS-CoV-2 BA.1, despite the absence of serum BA.1 neutralization. 25F9 and 20A7 neutralized authentic clade 1 sarbecoviruses (SARS-CoV, WIV-1, SHC014, SARS-CoV-2 D614G, BA.1, and Pangolin-GD) and vesicular stomatitis virus–pseudotyped clade 3 sarbecoviruses (BtKY72 and PRD-0038). 20A7 and 27A12 showed potent neutralization against all SARS-CoV-2 variants and multiple Omicron sublineages, including BA.1, BA.2, BA.3, BA.4/5, BQ.1, BQ.1.1, and XBB. Crystallography studies revealed the molecular basis of broad and potent neutralization through targeting conserved sites within the RBD. Prophylactic protection of 25F9, 20A7, and 27A12 was confirmed in mice, and administration of 25F9 particularly provided complete protection against SARS-CoV-2, BA.1, SARS-CoV, and SHC014 challenge. These data underscore the extremely potent and broad activity of these mAbs against sarbecoviruses.

Potent neutralization by a receptor binding domain monoclonal antibody with broad specificity for SARS-CoV-2 JN.1 and other variants

“…The functional activity of 1301B7 was tested in pseudovirus ( Figure 2C ) and live virus ( Figure 2D ) -based neutralization assays. Previously described RBD mAbs 25F9 6 , C68.61 7 , and S309 8 were included as controls. 1301B7 neutralized all SARS-CoV-2 isolates tested, in addition to exhibiting neutralizing activity against SARS-CoV pseudovirus.…”

“…Paired heavy and light chain genes were cloned into IgG1 expression vectors and were transfected into HEK293T cells and culture supernatant was concentrated using 100,000 MWCO Amicon Ultra centrifugal filters (Millipore-Sigma, Cork, Ireland), and IgG captured and eluted from Magne Protein A beads (Promega, Madison, WI) as previously described 18,19 . 25F9 and C68.61 were previously described 6,7 and heavy and light chain variable regions synthesized by Twist Biosciences on reported sequences and cloned into IgG1 expression vector for production in HEK293T cell.…”

“…hmAbs were diluted from an initial concentration of 20 µg/ml by a factor of five in 96-well plates, in triplicates. Subsequently, 50 µL of each dilution of mAb was incubated with 50 µL of diluted pseudovirus for 1 h at 37 °C, followed by the addition of 100 µL of resuspended Vero-E6 cells at a density of 3_×_10 6 cells/ml. Wells without mAbs (serving as ’virus alone’ controls) were included in all plates.…”

Hybrid immunity to SARS-CoV-2 arises from serological recall of IgG antibodies distinctly imprinted by infection or vaccination

“…Based upon our observations of IgG anti-S repertoires in vaccinated BT donors, our results suggest that deploying diverse RBDs in next-generation vaccine strategies (to emulate hybrid immunological S scenarios) should elicit SC27-like class 1/4 antibodies that have lengthy CDR-H3 loops juxtaposed with the RBD β-sheet backbone to confer broad reactivity while the orientation of their light chains should contribute to steric blockade of the ACE2 binding site. Hence, vaccines capable of triggering these antibodies 69,74,75 might offer protection against SARS-CoV-2, its variants, and newly emerging zoonotic sarbecoviruses, eliminating the necessity for frequent updates in response to new outbreaks.…”

Protective non-neutralizing mAbs Ab94 and Ab81 retain high-affinity and potent Fc-mediated function against SARS-CoV-2 variants from Omicron to XBB1.5

“…Although many neutralizing mAbs generated initially against the Wuhan strain lost binding and function, researchers have successfully developed mAbs that neutralize the variants currently circulating [7][8] . However, when testing these nAbs against emerging variants, several studies have shown a reduced neutralizing effect (IC50) compared to the Wuhan strain in the newer variants [7][8][21][22] . It appears likely that the trend will continue and that these nAbs will also eventually lose neutralizing capacity.…”