NK cells are critical for in vivo control of SARS-CoV-2 replication and suppression of lung damage (preprint)

Natural killer (NK) cells play a critical role in virus control. However, it has remained largely unclear whether NK cell mobilization in SARS-CoV-2 infections is beneficial or pathologic. To address this deficit, we employed a validated experimental NK cell depletion non-human primate (NHP) model with SARS-CoV-2 Delta variant B.1.617.2 challenge. Viral loads (VL), NK cell numbers, activation, proliferation, and functional measures were evaluated in blood and tissues. In non-depleted (control) animals, infection rapidly induced NK cell expansion, activation, and increased tissue trafficking associated with VL. Strikingly, we report that experimental NK cell depletion leads to higher VL, longer duration of viremia, significantly increased levels of pro-inflammatory cytokines in the lungs, and overt lung damage. Overall, we find the first significant and conclusive evidence for NK cell-mediated control of SARS-CoV-2 virus replication and disease pathology. These data indicate that adjunct therapies for infection could largely benefit from NK cell-targeted approaches.

Reduced Pathogenicity of the SARS-CoV-2 Omicron Variant in Hamsters (preprint)

The SARS-CoV-2 Omicron (B.1.1.529) variant has proven highly transmissible and has outcompeted the Delta variant in many regions of the world. Early reports have also suggested that Omicron may result in less severe clinical disease in humans. Here we show that Omicron is less pathogenic than prior SARS-CoV-2 variants in Syrian golden hamsters. Infection of hamsters with the SARS-CoV-2 WA1/2020, Alpha, Beta, or Delta strains led to 4-10% weight loss by day 4 and 10-17% weight loss by day 6, as expected. In contrast, infection of hamsters with two different Omicron challenge stocks did not result in any detectable weight loss, even at high challenge doses. Omicron infection still led to substantial viral replication in both the upper and lower respiratory tracts and pulmonary pathology, but with a trend towards higher viral loads in nasal turbinates and lower viral loads in lung parenchyma compared with WA1/2020 infection. These data suggest that the SARS-CoV-2 Omicron variant may result in more robust upper respiratory tract infection but less severe lower respiratory tract clinical disease compared with prior SARS-CoV-2 variants.

Ad26.COV2.S Prevents SARS-CoV-2 Induced Pathways of Inflammation and Thrombosis in Hamsters (preprint)

Syrian golden hamsters exhibit features of severe disease after SARS-CoV-2 challenge and are therefore useful models of COVID-19 pathogenesis and prevention with vaccines. Recent studies have shown that SARS-CoV-2 infection stimulates type I interferon, myeloid, and inflammatory signatures similar to human disease, and that weight loss can be prevented with vaccines. However, the impact of vaccination on transcriptional programs associated with COVID-19 pathogenesis and protective adaptive immune responses is unknown. Here we show that SARS-CoV-2 challenge in hamsters stimulates antiviral, myeloid, and inflammatory programs as well as signatures of complement and thrombosis associated with human COVID-19. Notably, single dose immunization with Ad26.COV2.S, an adenovirus serotype 26 vector (Ad26)-based vaccine expressing a stabilized SARS-CoV-2 spike protein, prevents the upregulation of these pathways such that the gene expression profiles of vaccinated hamsters are comparable to uninfected animals. Finally, we show that Ad26.COV2.S vaccination induces T and B cell signatures that correlate with binding and neutralizing antibody responses. These data provide further insights into the mechanisms of Ad26.COV2.S based protection against severe COVID-19 in hamsters. Author SummaryIn this study, we show that vaccination with Ad26.COV2.S protected SARS-CoV-2 challenged hamsters from developing severe COVID-19 disease by attenuating excessive proinflammatory responses, such as IL-6 and IL-1, macrophages and neutrophils signaling. Ad26 vaccination also prevented the upregulation of pathways associated with thrombosis such coagulation and clotting cascades associated with infection, and the transcriptomic profiles of vaccinated animals were largely comparable to control uninfected hamsters. In contrast, SARS-CoV-2 challenged unvaccinated hamsters showed significant increase of these proinflammatory and prothrombotic pathways and significant weight loss compared to vaccinated hamsters.

Optimization of Non-Coding Regions Improves Protective Efficacy of an mRNA SARS-CoV-2 Vaccine in Nonhuman Primates (preprint)

The CVnCoV (CureVac) mRNA vaccine for SARS-CoV-2 has recently been evaluated in a phase 2b/3 efficacy trial in humans. CV2CoV is a second-generation mRNA vaccine with optimized non-coding regions and enhanced antigen expression. Here we report a head-to-head study of the immunogenicity and protective efficacy of CVnCoV and CV2CoV in nonhuman primates. We immunized 18 cynomolgus macaques with two doses of 12 ug of lipid nanoparticle formulated CVnCoV, CV2CoV, or sham (N=6/group). CV2CoV induced substantially higher binding and neutralizing antibodies, memory B cell responses, and T cell responses as compared with CVnCoV. CV2CoV also induced more potent neutralizing antibody responses against SARS-CoV-2 variants, including B.1.351 (beta), B.1.617.2 (delta), and C.37 (lambda). While CVnCoV provided partial protection against SARS-CoV-2 challenge, CV2CoV afforded robust protection with markedly lower viral loads in the upper and lower respiratory tract. Antibody responses correlated with protective efficacy. These data demonstrate that optimization of non-coding regions can greatly improve the immunogenicity and protective efficacy of an mRNA SARS-CoV-2 vaccine in nonhuman primates.

Plasma Proteomics of COVID-19 Associated Cardiovascular Complications: Implications for Pathophysiology and Therapeutics (preprint)

Cardiovascular complications are common in COVID-19 and strongly associated with disease severity and mortality. However, the mechanisms driving cardiac injury and failure in COVID-19 are largely unknown. We performed plasma proteomics on 80 COVID-19 patients and controls, grouped according to disease severity and cardiac involvement. Findings were validated in 305 independent COVID-19 patients and investigated in an animal model. Here we show that senescence-associated secretory proteins, markers of biological aging, strongly associate with disease severity and cardiac involvement even in age-matched cohorts. FSTL3, an indicator of Activin/TGFβ signaling, was the most significantly upregulated protein associated with the heart failure biomarker, NTproBNP (β = 0.4;padj=4.6x10− 7), while ADAMTS13, a vWF-cleaving protease whose loss-of-function causes microvascular thrombosis, was the most downregulated protein associated with myocardial injury (β=-0.4;padj=8x10− 7). Mendelian randomization supported a causal role for ADAMTS13 in myocardial injury. These data provide important new insights into the pathophysiology of COVID-19 cardiovascular complications with therapeutic implications.

Low-Dose Ad26.COV2.S Protection Against SARS-CoV-2 Challenge in Rhesus Macaques (preprint)

We previously reported that a single immunization with an adenovirus serotype 26 (Ad26) vector-based vaccine expressing an optimized SARS-CoV-2 spike (Ad26.COV2.S) protected rhesus macaques against SARS-CoV-2 challenge. In this study, we evaluated the immunogenicity and protective efficacy of reduced doses of Ad26.COV2.S. 30 rhesus macaques were immunized once with 1×10 11 , 5×10 10 , 1.125×10 10 , or 2×10 9 vp Ad26.COV2.S or sham and were challenged with SARS-CoV-2 by the intranasal and intratracheal routes. Vaccine doses as low as 2×10 9 vp provided robust protection in bronchoalveolar lavage, whereas doses of 1.125×10 10 vp were required for protection in nasal swabs. Activated memory B cells as well as binding and neutralizing antibody titers following vaccination correlated with protective efficacy. At suboptimal vaccine doses, viral breakthrough was observed but did not show evidence of virologic, immunologic, histopathologic, or clinical enhancement of disease compared with sham controls. These data demonstrate that a single immunization with a relatively low dose of Ad26.COV2.S effectively protected against SARS-CoV-2 challenge in rhesus macaques. Moreover, our findings show that a higher vaccine dose may be required for protection in the upper respiratory tract compared with the lower respiratory tract.