The emergence of SARS-CoV in 2003 and SARS-CoV-2 in 2019 highlights the need to develop universal vaccination strategies against the broader Sarbecovirus subgenus. Using chimeric spike designs, we demonstrate protection against challenge from SARS-CoV, SARS-CoV-2, SARS-CoV-2 B.1.351, bat CoV (Bt-CoV) RsSHC014, and a heterologous Bt-CoV WIV-1 in vulnerable aged mice. Chimeric spike mRNAs induced high levels of broadly protective neutralizing antibodies against high-risk Sarbecoviruses. In contrast, SARS-CoV-2 mRNA vaccination not only showed a marked reduction in neutralizing titers against heterologous Sarbecoviruses, but SARS-CoV and WIV-1 challenge in mice resulted in breakthrough infections. Chimeric spike mRNA vaccines efficiently neutralized D614G, mink cluster five, and the UK B.1.1.7., and South African B.1.351 variants of concern. Thus, multiplexed-chimeric spikes can prevent SARS-like zoonotic coronavirus infections with pandemic potential.

Severe acute respiratory syndrome coronaviruses 1 (SARS-CoV) and 2 (SARS-CoV-2), including SARS-CoV-2 variants of concern, can cause deadly infections. The mortality associated with sarbecovirus infection underscores the importance of developing broadly effective countermeasures against them, which could be key in the prevention and mitigation of current and future zoonotic events. Here, we demonstrate the neutralization of SARS-CoV; bat coronaviruses WIV-1 and RsSHC014; and SARS-CoV-2 variants D614G, B.1.1.7, B.1.351, P.1, B.1.429, B.1.526, B.1.617.1, and B.1.617.2 by a receptor binding domain (RBD)–specific human antibody, DH1047. Prophylactic and therapeutic treatment with DH1047 was protective against SARS-CoV, WIV-1, RsSHC014, and SARS-CoV-2 B.1.351 infection in mice. Binding and structural analysis showed high affinity binding of DH1047 to an epitope that is highly conserved among sarbecoviruses. Thus, DH1047 is a broadly protective antibody that can prevent infection and mitigate outbreaks caused by SARS-related strains and SARS-CoV-2 variants. Our results also suggest that the conserved RBD epitope bound by DH1047 is a rational target for a universal sarbecovirus vaccine.

A subset of individuals who recover from coronavirus disease 2019 (COVID-19) develop post-acute sequelae of SARS-CoV-2 (PASC), but the mechanistic basis of PASC-associated lung abnormalities suffers from a lack of longitudinal tissue samples. The mouse-adapted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strain MA10 produces an acute respiratory distress syndrome (ARDS) in mice similar to humans. To investigate PASC pathogenesis, studies of MA10-infected mice were extended from acute to clinical recovery phases. At 15 to 120 days post-virus clearance, pulmonary histologic findings included subpleural lesions composed of collagen, proliferative fibroblasts, and chronic inflammation, including tertiary lymphoid structures. Longitudinal spatial transcriptional profiling identified global reparative and fibrotic pathways dysregulated in diseased regions, similar to human COVID-19. Populations of alveolar intermediate cells, coupled with focal up-regulation of pro-fibrotic markers, were identified in persistently diseased regions. Early intervention with antiviral EIDD-2801 reduced chronic disease, and early anti-fibrotic agent (nintedanib) intervention modified early disease severity. This murine model provides opportunities to identify pathways associated with persistent SARS-CoV-2 pulmonary disease and test countermeasures to ameliorate PASC.

The transplantation of rodent Schwann cells (SCs) provides anatomical and functional restitution in a variety of spinal cord injury (SCI) models, supporting the recent translation of SCs to phase 1 clinical trials for human SCI. Whereas human (Hu)SCs have been examined experimentally in a complete SCI transection paradigm, to date the reported behavior of SCs when transplanted after a clinically relevant contusive SCI has been restricted to the use of rodent SCs. Here, in a xenotransplant, contusive SCI paradigm, the survival, biodistribution, proliferation and tumorgenicity as well as host responses to HuSCs, cultured according to a protocol analogous to that developed for clinical application, were investigated. HuSCs persisted within the contused nude rat spinal cord through 6 months after transplantation (longest time examined), exhibited low cell proliferation, displayed no evidence of tumorigenicity and showed a restricted biodistribution to the lesion. Neuropathological examination of the CNS revealed no adverse effects of HuSCs. Animals exhibiting higher numbers of surviving HuSCs within the lesion showed greater volumes of preserved white matter and host rat SC and astrocyte ingress as well as axon ingrowth and myelination. These results demonstrate the safety of HuSCs when employed in a clinically relevant experimental SCI paradigm. Further, signs of a potentially positive influence of HuSC transplants on host tissue pathology were observed. These findings show that HuSCs exhibit a favorable toxicity profile for up to 6 months after transplantation into the contused rat spinal cord, an important outcome for FDA consideration of their use in human clinical trials.

Animal models and dose selectionThis analysis utilized three preclinical models from two species of humanized mice: stem cell hemopoietic/RAG 2-(hu-HSC-Rag, n=36) and bone marrow-liver-thymus (BLT, n=13) and one species of nonhuman primate (NHP): rhesus macaques (n=18).Humanization of the mice was by protocols that have been previously described (Melkus et al. 2006; Berges et al. 2006). The extent of humanization for the mouse models was assessed by quantifying the human T-cell populations using flow cytometry. All the humanized mice were female, while six (33.3%) NHPs were female. Half of the animals were left uninfected while the other half were infected with 200 μL of 2.1 x 10 6 IU/mL of HIVBal D7 intraperitoneally (hu-HSC-RAG) or 200 μL of 90,000 tissue culture infectious units (TCIU) of HIVJRcsf intravenously (BLT) or 10 4.5 median tissue culture infective dose (TCID50) RT-SHIV intravenously (NHPs) (North et al. 2005; North et al. 2010) for four weeks. The hu-HSC-RAG and BLT mice underwent humanization when aged three to six months and were then dosed with various ARV regimens for a period of ten days. Hu-HSC-RAG mice were dosed with EFV 10 mg/kg only (six uninfected and six infected animals) or atazanavir (ATZ) 140 mg/kg only (six uninfected and six infected animals) or a combination of tenofovir (TFV) 208 mg/kg, emtricitabine (FTC) 240 mg/kg, raltegravir (RAL) 56 mg/kg and maraviroc (MVC) 62 mg/kg (six uninfected and six infected animals). BLT mice were dosed with a combination of TFV, FTC, RAL, MVC and ATZ at equivalent doses but not EFV due to toxicity concerns. All drugs were administered by oral gavage. Dosing regimens for each of the animal models are summarized in Supplementary Table 1. Dosage selection for all drugs in the animal