Subclass-switched anti-spike IgG3 oligoclonal cocktails strongly enhance Fc-mediated opsonization.

Antibodies play a central role in the immune defense against SARS-CoV-2. Emerging evidence has shown that nonneutralizing antibodies are important for immune defense through Fc-mediated effector functions. Antibody subclass is known to affect downstream Fc function. However, whether the antibody subclass plays a role in anti-SARS-CoV-2 immunity remains unclear. Here, we subclass-switched eight human IgG1 anti-spike monoclonal antibodies (mAbs) to the IgG3 subclass by exchanging their constant domains. The IgG3 mAbs exhibited altered avidities to the spike protein and more potent Fc-mediated phagocytosis and complement activation than their IgG1 counterparts. Moreover, combining mAbs into oligoclonal cocktails led to enhanced Fc- and complement receptor-mediated phagocytosis, superior to even the most potent single IgG3 mAb when compared at equivalent concentrations. Finally, in an in vivo model, we show that opsonic mAbs of both subclasses can be protective against a SARS-CoV-2 infection, despite the antibodies being nonneutralizing. Our results suggest that opsonic IgG3 oligoclonal cocktails are a promising idea to explore for therapy against SARS-CoV-2, its emerging variants, and potentially other viruses.

A universal SARS-CoV DNA vaccine inducing highly cross-reactive neutralizing antibodies and T cells.

New variants in the SARS-CoV-2 pandemic are more contagious (Alpha/Delta), evade neutralizing antibodies (Beta), or both (Omicron). This poses a challenge in vaccine development according to WHO. We designed a more universal SARS-CoV-2 DNA vaccine containing receptor-binding domain loops from the huCoV-19/WH01, the Alpha, and the Beta variants, combined with the membrane and nucleoproteins. The vaccine induced spike antibodies crossreactive between huCoV-19/WH01, Beta, and Delta spike proteins that neutralized huCoV-19/WH01, Beta, Delta, and Omicron virus in vitro. The vaccine primed nucleoprotein-specific T cells, unlike spike-specific T cells, recognized Bat-CoV sequences. The vaccine protected mice carrying the human ACE2 receptor against lethal infection with the SARS-CoV-2 Beta variant. Interestingly, priming of cross-reactive nucleoprotein-specific T cells alone was 60% protective, verifying observations from humans that T cells protect against lethal disease. This SARS-CoV vaccine induces a uniquely broad and functional immunity that adds to currently used vaccines.

Macromolecular Viral Entry Inhibitors as Broad-Spectrum First-Line Antivirals with Activity against SARS-CoV-2.

Inhibitors of viral cell entry based on poly(styrene sulfonate) and its core-shell nanoformulations based on gold nanoparticles are investigated against a panel of viruses, including clinical isolates of SARS-CoV-2. Macromolecular inhibitors are shown to exhibit the highly sought-after broad-spectrum antiviral activity, which covers most analyzed enveloped viruses and all of the variants of concern for SARS-CoV-2 tested. The inhibitory activity is quantified in vitro in appropriate cell culture models and for respiratory viral pathogens (respiratory syncytial virus and SARS-CoV-2) in mice. Results of this study comprise a significant step along the translational path of macromolecular inhibitors of virus cell entry, specifically against enveloped respiratory viruses.

Spike-Dependent Opsonization Indicates Both Dose-Dependent Inhibition of Phagocytosis and That Non-Neutralizing Antibodies Can Confer Protection to SARS-CoV-2.

Spike-specific antibodies are central to effective COVID19 immunity. Research efforts have focused on antibodies that neutralize the ACE2-Spike interaction but not on non-neutralizing antibodies. Antibody-dependent phagocytosis is an immune mechanism enhanced by opsonization, where typically, more bound antibodies trigger a stronger phagocyte response. Here, we show that Spike-specific antibodies, dependent on concentration, can either enhance or reduce Spike-bead phagocytosis by monocytes independently of the antibody neutralization potential. Surprisingly, we find that both convalescent patient plasma and patient-derived monoclonal antibodies lead to maximum opsonization already at low levels of bound antibodies and is reduced as antibody binding to Spike protein increases. Moreover, we show that this Spike-dependent modulation of opsonization correlate with the outcome in an experimental SARS-CoV-2 infection model. These results suggest that the levels of anti-Spike antibodies could influence monocyte-mediated immune functions and propose that non-neutralizing antibodies could confer protection to SARS-CoV-2 infection by mediating phagocytosis.