MVA-based vaccines are protective against lethal eastern equine encephalitis virus aerosol challenge in cynomolgus macaques.

MVA-based monovalent eastern equine encephalitis virus (MVA-BN-EEEV) and multivalent western, eastern, and Venezuelan equine encephalitis virus (MVA-BN-WEV) vaccines were evaluated in the cynomolgus macaque aerosol model of EEEV infection. Macaques vaccinated with two doses of 5 × 108 infectious units of the MVA-BN-EEEV or MVA-BN-WEV vaccine by the intramuscular route rapidly developed robust levels of neutralizing antibodies to EEEV that persisted at high levels until challenge at day 84 via small particle aerosol delivery with a target inhaled dose of 107 PFU of EEEV FL93-939. Robust protection was observed, with 7/8 animals receiving MVA-BN-EEEV and 100% (8/8) animals receiving MVA-BN-WEV surviving while only 2/8 mock vaccinated controls survived lethal challenge. Complete protection from viremia was afforded by both vaccines, with near complete protection from vRNA loads in tissues and any pathologic evidence of central nervous system damage. Overall, the results indicate both vaccines are effective in eliciting an immune response that is consistent with protection from aerosolized EEEV-induced disease.

COVID-19 and influenza infections mediate distinct pulmonary cellular and transcriptomic changes.

SARS-CoV-2 infection can cause persistent respiratory sequelae. However, the underlying mechanisms remain unclear. Here we report that sub-lethally infected K18-human ACE2 mice show patchy pneumonia associated with histiocytic inflammation and collagen deposition at 21 and 45 days post infection (DPI). Transcriptomic analyses revealed that compared to influenza-infected mice, SARS-CoV-2-infected mice had reduced interferon-gamma/alpha responses at 4 DPI and failed to induce keratin 5 (Krt5) at 6 DPI in lung, a marker of nascent pulmonary progenitor cells. Histologically, influenza- but not SARS-CoV-2-infected mice showed extensive Krt5+ "pods" structure co-stained with stem cell markers Trp63/NGFR proliferated in the pulmonary consolidation area at both 7 and 14 DPI, with regression at 21 DPI. These Krt5+ "pods" structures were not observed in the lungs of SARS-CoV-2-infected humans or nonhuman primates. These results suggest that SARS-CoV-2 infection fails to induce nascent Krt5+ cell proliferation in consolidated regions, leading to incomplete repair of the injured lung.

The Impact of SIV-Induced Immunodeficiency on Clinical Manifestation, Immune Response, and Viral Dynamics in SARS-CoV-2 Coinfection.

Persistent and uncontrolled SARS-CoV-2 replication in immunocompromised individuals has been observed and may be a contributing source of novel viral variants that continue to drive the pandemic. Importantly, the effects of immunodeficiency associated with chronic HIV infection on COVID-19 disease and viral persistence have not been directly addressed in a controlled setting. Here we conducted a pilot study wherein two pigtail macaques (PTM) chronically infected with SIVmac239 were exposed to SARS-CoV-2 and monitored for six weeks for clinical disease, viral replication, and viral evolution, and compared to our previously published cohort of SIV-naïve PTM infected with SARS-CoV-2. At the time of SARS-CoV-2 infection, one PTM had minimal to no detectable CD4+ T cells in gut, blood, or bronchoalveolar lavage (BAL), while the other PTM harbored a small population of CD4+ T cells in all compartments. Clinical signs were not observed in either PTM; however, the more immunocompromised PTM exhibited a progressive increase in pulmonary infiltrating monocytes throughout SARS-CoV-2 infection. Single-cell RNA sequencing (scRNAseq) of the infiltrating monocytes revealed a less activated/inert phenotype. Neither SIV-infected PTM mounted detectable anti-SARS-CoV-2 T cell responses in blood or BAL, nor anti-SARS-CoV-2 neutralizing antibodies. Interestingly, despite the diminished cellular and humoral immune responses, SARS-CoV-2 viral kinetics and evolution were indistinguishable from SIV-naïve PTM in all sampled mucosal sites (nasal, oral, and rectal), with clearance of virus by 3-4 weeks post infection. SIV-induced immunodeficiency significantly impacted immune responses to SARS-CoV-2 but did not alter disease progression, viral kinetics or evolution in the PTM model. SIV-induced immunodeficiency alone may not be sufficient to drive the emergence of novel viral variants.

Real-Time Analysis of SARS-CoV-2-Induced Cytolysis Reveals Distinct Variant-Specific Replication Profiles.

The ability of each new SARS-CoV-2 variant to evade host humoral immunity is the focus of intense research. Each variant may also harbor unique replication capabilities relevant for disease and transmission. Here, we demonstrate a new approach to assessing viral replication kinetics using real-time cell analysis (RTCA). Virus-induced cell death is measured in real time as changes in electrical impedance through cell monolayers while images are acquired at defined intervals via an onboard microscope and camera. Using this system, we quantified replication kinetics of five clinically important viral variants: WA1/2020 (ancestral), Delta, and Omicron subvariants BA.1, BA.4, and BA.5. Multiple measures proved useful in variant replication comparisons, including the elapsed time to, and the slope at, the maximum rate of cell death. Important findings include significantly weaker replication kinetics of BA.1 by all measures, while BA.5 harbored replication kinetics at or near ancestral levels, suggesting evolution to regain replicative capacity, and both an altered profile of cell killing and enhanced fusogenicity of the Delta variant. Together, these data show that RTCA is a robust method to assess replicative capacity of any given SARS-CoV-2 variant rapidly and quantitatively, which may be useful in assessment of newly emerging variants.

Effect of acetic acid inactivation of SARS-CoV-2.

Effective measures are needed to prevent the spread and infectivity of SARS-CoV-2 that causes COVID-19. Chemical inactivation may help to prevent the spread and transmission of this and other viruses. Hence, we tested the SARS-CoV-2 antiviral activity of acetic acid, the main component of vinegar, in vitro. Inactivation and binding assays suggest that acetic acid is virucidal. We found that 6% acetic acid, a concentration typically found in white distilled vinegar, effectively inactivated SARS-CoV-2 after 15-min incubation with a complete loss of replication of competent virus as measured by TCID50. Transmission electron microscopy further demonstrated that 6% acetic acid disrupts SARS-CoV-2 virion structure. In addition, 6% acetic acid significantly inhibits and disrupts the binding of SARS-CoV-2 spike protein binding to ACE2, the primary SARS-CoV-2 cell receptor, after contact with spike protein for 5, 10, 30 and 60 minutes incubation. Taken together, our findings demonstrate that acetic acid possesses inactivating activity against SARS-CoV-2 and may represent a safe alternative to commonly used chemical disinfectants to effectively control the spread of SARS-CoV-2.

Mid-titer human convalescent plasma administration results in suboptimal prophylaxis against SARS-CoV-2 infection in rhesus macaques.

Introduction: ARS-CoV-2 is a respiratory pathogen currently causing a worldwide pandemic, with resulting pathology of differing severity in humans, from mild illness to severe disease and death. The rhesus macaque model of COVID-19 was utilized to evaluate the added benefit of prophylactic administration of human post-SARS-CoV-2 infection convalescent plasma (CP) on disease progression and severity. Methods: A pharmacokinetic (PK) study using CP in rhesus monkeys preceded the challenge study and revealed the optimal time of tissue distribution for maximal effect. Thereafter, CP was administered prophylactically three days prior to mucosal SARS-CoV-2 viral challenge. Results: Results show similar viral kinetics in mucosal sites over the course of infection independent of administration of CP or normal plasma, or historic controls with no plasma. No changes were noted upon necropsy via histopathology, although there were differences in levels of vRNA in tissues, with both normal and CP seemingly blunting viral loads. Discussion: Results indicate that prophylactic administration with mid-titer CP is not effective in reducing disease severity of SARS-CoV-2 infection in the rhesus COVID-19 disease model.

The dynamics of γδ T cell responses in nonhuman primates during SARS-CoV-2 infection.

Although most SARS-CoV-2 infections are mild, some patients develop systemic inflammation and progress to acute respiratory distress syndrome (ARDS). However, the cellular mechanisms underlying this spectrum of disease remain unclear. γδT cells are T lymphocyte subsets that have key roles in systemic and mucosal immune responses during infection and inflammation. Here we show that peripheral γδT cells are rapidly activated following aerosol or intra-tracheal/intra-nasal (IT/IN) SARS-CoV-2 infection in nonhuman primates. Our results demonstrate a rapid expansion of Vδ1 γδT cells at day1 that correlate significantly with lung viral loads during the first week of infection. Furthermore, increase in levels of CCR6 and Granzyme B expression in Vδ1 T cells during viral clearance imply a role in innate-like epithelial barrier-protective and cytotoxic functions. Importantly, the early activation and mobilization of circulating HLA-DR+CXCR3+ γδT cells along with significant correlations of Vδ1 T cells with IL-1Ra and SCF levels in bronchoalveolar lavage suggest a novel role for Vδ1 T cells in regulating lung inflammation during aerosol SARS-CoV-2 infection. A deeper understanding of the immunoregulatory functions of MHC-unrestricted Vδ1 T cells in lungs during early SARS-CoV-2 infection is particularly important in the wake of emerging new variants with increased transmissibility and immune evasion potential.

Durable protection against the SARS-CoV-2 Omicron variant is induced by an adjuvanted subunit vaccine.

Despite the remarkable efficacy of COVID-19 vaccines, waning immunity and the emergence of SARS-CoV-2 variants such as Omicron represents a global health challenge. Here, we present data from a study in nonhuman primates demonstrating durable protection against the Omicron BA.1 variant induced by a subunit SARS-CoV-2 vaccine comprising the receptor binding domain of the ancestral strain (RBD-Wu) on the I53-50 nanoparticle adjuvanted with AS03, which was recently authorized for use in individuals 18 years or older. Vaccination induced neutralizing antibody (nAb) titers that were maintained at high concentrations for at least 1 year after two doses, with a pseudovirus nAb geometric mean titer (GMT) of 1978 and a live virus nAb GMT of 1331 against the ancestral strain but not against the Omicron BA.1 variant. However, a booster dose at 6 to 12 months with RBD-Wu or RBD-ß (RBD from the Beta variant) displayed on I53-50 elicited high neutralizing titers against the ancestral and Omicron variants. In addition, we observed persistent neutralization titers against a panel of sarbecoviruses, including SARS-CoV. Furthermore, there were substantial and persistent memory T and B cell responses reactive to Beta and Omicron variants. Vaccination resulted in protection against Omicron infection in the lung and suppression of viral burden in the nares at 6 weeks after the final booster immunization. Even at 6 months after vaccination, we observed protection in the lung and rapid control of virus in the nares. These results highlight the durable and cross-protective immunity elicited by the AS03-adjuvanted RBD-I53-50 nanoparticle vaccine.

Zika virus persistence in the male macaque reproductive tract.

Zika virus (ZIKV) is unique among mosquito-borne flaviviruses in that it is also vertically and sexually transmitted by humans. The male reproductive tract is thought to be a ZIKV reservoir; however, the reported magnitude and duration of viral persistence in male genital tissues vary widely in humans and non-human primate models. ZIKV tissue and cellular tropism and potential effects on male fertility also remain unclear. The objective of this study was to resolve these questions by analyzing archived genital tissues from 51 ZIKV-inoculated male macaques and correlating data on plasma viral kinetics, tissue tropism, and ZIKV-induced pathological changes in the reproductive tract. We hypothesized that ZIKV would persist in the male macaque genital tract for longer than there was detectable viremia, where it would localize to germ and epithelial cells and associate with lesions. We detected ZIKV RNA and infectious virus in testis, epididymis, seminal vesicle, and prostate gland. In contrast to prepubertal males, sexually mature macaques were significantly more likely to harbor persistent ZIKV RNA or infectious virus somewhere in the genital tract, with detection as late as 60 days post-inoculation. ZIKV RNA localized primarily to testicular stem cells/sperm precursors and epithelial cells, including Sertoli cells, epididymal duct epithelium, and glandular epithelia of the seminal vesicle and prostate gland. ZIKV infection was associated with microscopic evidence of inflammation in the epididymis and prostate gland of sexually mature males, pathologies that were absent in uninfected controls, which could have significant effects on male fertility. The findings from this study increase our understanding of persistent ZIKV infection which can inform risk of sexual transmission during assisted reproductive therapies as well as potential impacts on male fertility.

Exposure modality influences viral kinetics but not respiratory outcome of COVID-19 in multiple nonhuman primate species.

The novel coronavirus SARS-CoV-2 emerged in late 2019, rapidly reached pandemic status, and has maintained global ubiquity through the emergence of variants of concern. Efforts to develop animal models have mostly fallen short of recapitulating severe disease, diminishing their utility for research focusing on severe disease pathogenesis and life-saving medical countermeasures. We tested whether route of experimental infection substantially changes COVID-19 disease characteristics in two species of nonhuman primates (Macaca mulatta; rhesus macaques; RM, Chlorocebus atheiops; African green monkeys; AGM). Species-specific cohorts were experimentally infected with SARS-CoV-2 by either direct mucosal (intratracheal + intranasal) instillation or small particle aerosol in route-discrete subcohorts. Both species demonstrated analogous viral loads in all compartments by either exposure route although the magnitude and duration of viral loading was marginally greater in AGMs than RMs. Clinical onset was nearly immediate (+1dpi) in the mucosal exposure cohort whereas clinical signs and cytokine responses in aerosol exposure animals began +7dpi. Pathologies conserved in both species and both exposure modalities include pulmonary myeloid cell influx, development of pleuritis, and extended lack of regenerative capacity in the pulmonary compartment. Demonstration of conserved pulmonary pathology regardless of species and exposure route expands our understanding of how SARS-CoV-2 infection may lead to ARDS and/or functional lung damage and demonstrates the near clinical response of the nonhuman primate model for anti-fibrotic therapeutic evaluation studies.

A cellular trafficking signal in the SIV envelope protein cytoplasmic domain is strongly selected for in pathogenic infection.

The HIV/SIV envelope glycoprotein (Env) cytoplasmic domain contains a highly conserved Tyr-based trafficking signal that mediates both clathrin-dependent endocytosis and polarized sorting. Despite extensive analysis, the role of these functions in viral infection and pathogenesis is unclear. An SIV molecular clone (SIVmac239) in which this signal is inactivated by deletion of Gly-720 and Tyr-721 (SIVmac239ΔGY), replicates acutely to high levels in pigtail macaques (PTM) but is rapidly controlled. However, we previously reported that rhesus macaques and PTM can progress to AIDS following SIVmac239ΔGY infection in association with novel amino acid changes in the Env cytoplasmic domain. These included an R722G flanking the ΔGY deletion and a nine nucleotide deletion encoding amino acids 734-736 (ΔQTH) that overlaps the rev and tat open reading frames. We show that molecular clones containing these mutations reconstitute signals for both endocytosis and polarized sorting. In one PTM, a novel genotype was selected that generated a new signal for polarized sorting but not endocytosis. This genotype, together with the ΔGY mutation, was conserved in association with high viral loads for several months when introduced into naïve PTMs. For the first time, our findings reveal strong selection pressure for Env endocytosis and particularly for polarized sorting during pathogenic SIV infection in vivo.

C57BL/6J Mice Are Not Suitable for Modeling Severe SARS-CoV-2 Beta and Gamma Variant Infection.

SARS-CoV-2 variants, including B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta) variants, have displayed increased transmissibility and, therefore, have been categorized as variants of concern (VOCs). The pervasiveness of VOCs suggests a high probability of future mutations that may lead to increased virulence. Prior reports have shown that VOC infection without expression of human angiotensin converting enzyme-2 receptor (hACE2) in mice is possible. We sought to understand if the increased transmissibility of VOCs can infect C57BL/6 mice without expression of hACE2 receptor required for entry of SARS-CoV-2 normally. We examined the ability of infection with Beta and Gamma variants to infect and cause both pathological and clinical changes consistent with severe COVID-19, including body weight changes, survival, subgenomic viral titer, lung histology on Hematoxylin and Eosin (H&E) staining, and viral protein expression as measured by immunohistochemistry staining of viral antigen (IHC). These methods were used to examine three groups of mice: C57BL6, Rag2-/-, and Ccr2-/- mice. We observed that these mice, infected with Beta and Gamma variants of SARS-CoV-2, did not show pathological changes as indicated by weight loss, altered survival, or significant lung pathology on H&E staining. Subgenomic qPCR and IHC staining for viral protein indicated that there was some evidence of infection but far below ACE2 transgenic mice, which showed clinical disease and pathologic changes consistent with ARDS. These data suggest that these variants replicate poorly even in the setting of profound immune deficiency.

Breakthrough Gastrointestinal COVID-19 and Intrahost Evolution Consequent to Combination Monoclonal Antibody Prophylaxis.

Breakthrough gastrointestinal COVID-19 was observed after experimental SARS-CoV-2 upper mucosal infection in a rhesus macaque undergoing low-dose monoclonal antibody prophylaxis. High levels of viral RNA were detected in intestinal sites contrasting with minimal viral replication in upper respiratory mucosa. Sequencing of virus recovered from tissue in 3 gastrointestinal sites and rectal swab revealed loss of furin cleavage site deletions present in the inoculating virus stock and 2 amino acid changes in spike that were detected in 2 colon sites but not elsewhere, suggesting compartmentalized replication and intestinal viral evolution. This suggests suboptimal antiviral therapies promote viral sequestration in these anatomies.

Neuropathology and virus in brain of SARS-CoV-2 infected non-human primates.

Neurological manifestations are a significant complication of coronavirus disease (COVID-19), but underlying mechanisms aren't well understood. The development of animal models that recapitulate the neuropathological findings of autopsied brain tissue from patients who died from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are critical for elucidating the neuropathogenesis of infection and disease. Here, we show neuroinflammation, microhemorrhages, brain hypoxia, and neuropathology that is consistent with hypoxic-ischemic injury in SARS-CoV-2 infected non-human primates (NHPs), including evidence of neuron degeneration and apoptosis. Importantly, this is seen among infected animals that do not develop severe respiratory disease, which may provide insight into neurological symptoms associated with "long COVID". Sparse virus is detected in brain endothelial cells but does not associate with the severity of central nervous system (CNS) injury. We anticipate our findings will advance our current understanding of the neuropathogenesis of SARS-CoV-2 infection and demonstrate SARS-CoV-2 infected NHPs are a highly relevant animal model for investigating COVID-19 neuropathogenesis among human subjects.

Imaging of surface microdomains on individual extracellular vesicles in 3-D.

Extracellular vesicles (EVs) are secreted from all cell types and are intimately involved in tissue homeostasis. They are being explored as vaccine and gene therapy platforms, as well as potential biomarkers. As their size is below the diffraction limit of light microscopy, direct visualizations have been daunting and single-particle studies under physiological conditions have been hampered. Here, direct stochastic optical reconstruction microscopy (dSTORM) was employed to visualize EVs in three-dimensions and to localize molecule clusters such as the tetraspanins CD81 and CD9 on the surface of individual EVs. These studies demonstrate the existence of membrane microdomains on EVs. These were confirmed by Cryo-EM. Individual particle visualization provided insights into the heterogeneity, structure, and complexity of EVs not previously appreciated.

Rapid detection of multiple SARS-CoV-2 variants of concern by PAM-targeting mutations.

SARS-CoV-2 variants of concern (VOCs) that increase transmission or disease severity or reduce diagnostic or vaccine efficacy continue to emerge across the world. Current methods available to rapidly detect these can be resource intensive and thus sub-optimal for large-scale deployment needed during a pandemic response. Here, we describe a CRISPR-based assay that detects mutations in spike gene CRISPR PAM motif or seed regions to identify a pan-specific VOC single-nucleotide polymorphism (SNP)) ((D614G) and Alpha- and Delta-specific (S982A and D950N) SNPs. This assay exhibits good diagnostic sensitivity and strain specificity with nasal swabs and is designed for use in laboratory and point-of-care settings. This should enable rapid, high-throughput VOC identification required for surveillance and characterization efforts to inform clinical and public health decisions. Furthermore, the assay can be adapted to target similar SNPs associated with emerging SARS-CoV-2 VOCs, or other rapidly evolving viruses.

CRISPR-based assay reveals SARS-CoV-2 RNA dynamic changes and redistribution patterns in non-human primate model.

Mounting evidence indicates that SARS-CoV-2 can infect multiple systemic tissues, but few studies have evaluated SARS-CoV-2 RNA dynamics in multiple specimen types due to their reduced accessibility and diminished performance of RT-qPCR with non-respiratory specimens. Here, we employed an ultrasensitive CRISPR-RT-PCR assay to analyze longitudinal mucosal (nasal, buccal, pharyngeal, and rectal), plasma, and breath samples from SARS-CoV-2-infected non-human primates (NHPs) to detect dynamic changes in SARS-CoV-2 RNA level and distribution among these specimens. We observed that CRISPR-RT-PCR results consistently detected SARS-CoV-2 RNA in all sample types at most time points post-infection, and that SARS-CoV-2 infection dose and administration route did not markedly affect the CRISPR-RT-PCR signal detected in most specimen types. However, consistent RT-qPCR positive results were restricted to nasal, pharyngeal, and rectal swab samples, and tended to decrease earlier than CRISPR-RT-PCR results, reflecting lower assay sensitivity. SARS-CoV-2 RNA was detectable in both pulmonary and extrapulmonary specimens from early to late infection by CRISPR-RT-PCR, albeit with different abundance and kinetics, with SARS-CoV-2 RNA increases detected in plasma and rectal samples trailing those detected in upper respiratory tract samples. CRISPR-RT-PCR assays for SARS-CoV-2 RNA in non-respiratory specimens may thus permit direct diagnosis of suspected COVID-19 cases missed by RT-PCR, while tracking SARS-CoV-2 RNA in minimally invasive alternate specimens may better evaluate the progression and resolution of SARS-CoV-2 infections.

Intra-Host SARS-CoV-2 Evolution in the Gut of Mucosally-Infected Chlorocebus aethiops (African Green Monkeys).

In recent months, several SARS-CoV-2 variants have emerged that enhance transmissibility and escape host humoral immunity. Hence, the tracking of viral evolutionary trajectories is clearly of great importance. Little is known about SARS-CoV-2 evolution in nonhuman primate models used to test vaccines and therapies and to model human disease. Viral RNA was sequenced from rectal swabs from Chlorocebus aethiops (African green monkeys) after experimental respiratory SARS-CoV-2 infection. Two distinct patterns of viral evolution were identified that were shared between all collected samples. First, mutations in the furin cleavage site that were initially present in the virus as a consequence of VeroE6 cell culture adaptation were not detected in viral RNA recovered in rectal swabs, confirming the necessity of this motif for viral infection in vivo. Three amino acid changes were also identified; ORF 1a S2103F, and spike D215G and H655Y, which were detected in rectal swabs from all sampled animals. These findings are demonstrative of intra-host SARS-CoV-2 evolution and may identify a host-adapted variant of SARS-CoV-2 that would be useful in future primate models involving SARS-CoV-2 infection.

Mouse Adapted SARS-CoV-2 (MA10) Viral Infection Induces Neuroinflammation in Standard Laboratory Mice.

Increasing evidence suggests that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection impacts neurological function both acutely and chronically, even in the absence of pronounced respiratory distress. Developing clinically relevant laboratory mouse models of the neuropathogenesis of SARS-CoV-2 infection is an important step toward elucidating the underlying mechanisms of SARS-CoV-2-induced neurological dysfunction. Although various transgenic models and viral delivery methods have been used to study the infection potential of SARS-CoV-2 in mice, the use of commonly available laboratory mice would facilitate the study of SARS-CoV-2 neuropathology. Herein we show neuroinflammatory profiles of immunologically intact mice, C57BL/6J and BALB/c, as well as immunodeficient (Rag2-/-) mice, to a mouse-adapted strain of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2 (MA10)). Our findings indicate that brain IL-6 levels are significantly higher in BALB/c male mice infected with SARS-CoV-2 MA10. Additionally, blood-brain barrier integrity, as measured by the vascular tight junction protein claudin-5, was reduced by SARS-CoV-2 MA10 infection in all three strains. Brain glial fibrillary acidic protein (GFAP) mRNA was also elevated in male C57BL/6J infected mice compared with the mock group. Lastly, immune-vascular effects of SARS-CoV-2 (MA10), as measured by H&E scores, demonstrate an increase in perivascular lymphocyte cuffing (PLC) at 30 days post-infection among infected female BALB/c mice with a significant increase in PLC over time only in SARS-CoV-2 MA10) infected mice. Our study is the first to demonstrate that SARS-CoV-2 (MA10) infection induces neuroinflammation in laboratory mice and could be used as a novel model to study SARS-CoV-2-mediated cerebrovascular pathology.

ACE2-IgG1 fusions with improved in vitro and in vivo activity against SARS-CoV-2.

SARS-CoV-2, the etiologic agent of COVID-19, uses ACE2 as a cell entry receptor. Soluble ACE2 has been shown to have neutralizing antiviral activity but has a short half-life and no active transport mechanism from the circulation into the alveolar spaces of the lung. To overcome this, we constructed an ACE2-human IgG1 fusion protein with mutations in the catalytic domain of ACE2. A mutation in the catalytic domain of ACE2, MDR504, significantly increased binding to SARS-CoV-2 spike protein, as well as to a spike variant, in vitro with more potent viral neutralization in plaque assays. Parental administration of the protein showed stable serum concentrations with excellent bioavailability in the epithelial lining fluid of the lung, and ameliorated lung SARS-CoV-2 infection in vivo. These data support that the MDR504 hACE2-Fc is an excellent candidate for treatment or prophylaxis of COVID-19 and potentially emerging variants.