Soluble ACE2-mediated cell entry of SARS-CoV-2 via interaction with proteins related to the renin-angiotensin system.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause acute respiratory disease and multiorgan failure. Finding human host factors that are essential for SARS-CoV-2 infection could facilitate the formulation of treatment strategies. Using a human kidney cell line-HK-2-that is highly susceptible to SARS-CoV-2, we performed a genome-wide RNAi screen and identified virus dependency factors (VDFs), which play regulatory roles in biological pathways linked to clinical manifestations of SARS-CoV-2 infection. We found a role for a secretory form of SARS-CoV-2 receptor, soluble angiotensin converting enzyme 2 (sACE2), in SARS-CoV-2 infection. Further investigation revealed that SARS-CoV-2 exploits receptor-mediated endocytosis through interaction between its spike with sACE2 or sACE2-vasopressin via AT1 or AVPR1B, respectively. Our identification of VDFs and the regulatory effect of sACE2 on SARS-CoV-2 infection shed insight into pathogenesis and cell entry mechanisms of SARS-CoV-2 as well as potential treatment strategies for COVID-19.

Autoantibodies against angiotensin-converting enzyme 2 (ACE2) after COVID-19 infection or vaccination.

Autoantibodies against angiotensin-converting enzyme 2 (ACE2) are frequently reported in patients during coronavirus disease 2019 (COVID-19) with evidence for a pathogenic role in severe infection. However, little is known of the prevalence or clinical significance of ACE2 autoantibodies in late convalescence or following COVID-19 vaccination. In this study, we measured ACE2 autoantibodies in a cohort of 182 COVID-19 convalescent patients, 186 COVID-19 vaccine recipients, and 43 adolescents with post-mRNA vaccine myopericarditis using two ACE2 enzymatic immunoassays (EIAs). ACE2 IgM autoantibody EIA median optical densities (ODs) were lower in convalescent patients than pre-COVID-19 control samples with only 2/182 (1.1%) convalescents testing positive. Similarly, only 3/182 (1.6%) convalescent patients tested positive for ACE2 IgG, but patients with history of moderate-severe COVID-19 tended to have significantly higher median ODs than controls and mild COVID-19 patients. In contrast, ACE2 IgG antibodies were detected in 10/186 (5.4%) COVID-19 vaccine recipients after two doses of vaccination. Median ACE2 IgG EIA ODs of vaccine recipients were higher than controls irrespective of the vaccine platform used (inactivated or mRNA). ACE2 IgG ODs were not correlated with surrogate neutralizing antibody levels in vaccine recipients. ACE2 IgG levels peaked at day 56 post-first dose and declined within 12 months to baseline levels in vaccine recipients. Presence of ACE2 antibodies was not associated with adverse events following immunization including myopericarditis. One convalescent patient with ACE2 IgG developed Guillain-Barre syndrome, but causality was not established. ACE2 autoantibodies are observed in COVID-19 vaccine recipients and convalescent patients, but are likely innocuous.

Middle East Respiratory Syndrome Coronavirus ORF8b Accessory Protein Suppresses Type I IFN Expression by Impeding HSP70-Dependent Activation of IRF3 Kinase IKKε.

Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human coronavirus causing severe disease and mortality. MERS-CoV infection failed to elicit robust IFN response, suggesting that the virus might have evolved strategies to evade host innate immune surveillance. In this study, we identified and characterized type I IFN antagonism of MERS-CoV open reading frame (ORF) 8b accessory protein. ORF8b was abundantly expressed in MERS-CoV-infected Huh-7 cells. When ectopically expressed, ORF8b inhibited IRF3-mediated IFN-ß expression induced by Sendai virus and poly(I:C). ORF8b was found to act at a step upstream of IRF3 to impede the interaction between IRF3 kinase IKKε and chaperone protein HSP70, which is required for the activation of IKKε and IRF3. An infection study using recombinant wild-type and ORF8b-deficient MERS-CoV further confirmed the suppressive role of ORF8b in type I IFN induction and its disruption of the colocalization of HSP70 with IKKε. Ectopic expression of HSP70 relieved suppression of IFN-ß expression by ORF8b in an IKKε-dependent manner. Enhancement of IFN-ß induction in cells infected with ORF8b-deficient virus was erased when HSP70 was depleted. Taken together, HSP70 chaperone is important for IKKε activation, and MERS-CoV ORF8b suppresses type I IFN expression by competing with IKKε for interaction with HSP70.

Severe acute respiratory syndrome coronavirus ORF3a protein activates the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of ASC.

Severe acute respiratory syndrome coronavirus (SARS-CoV) is capable of inducing a storm of proinflammatory cytokines. In this study, we show that the SARS-CoV open reading frame 3a (ORF3a) accessory protein activates the NLRP3 inflammasome by promoting TNF receptor-associated factor 3 (TRAF3)-mediated ubiquitination of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC). SARS-CoV and its ORF3a protein were found to be potent activators of pro-IL-1ß gene transcription and protein maturation, the 2 signals required for activation of the NLRP3 inflammasome. ORF3a induced pro-IL-1ß transcription through activation of NF-κB, which was mediated by TRAF3-dependent ubiquitination and processing of p105. ORF3a-induced elevation of IL-1ß secretion was independent of its ion channel activity or absent in melanoma 2 but required NLRP3, ASC, and TRAF3. ORF3a interacted with TRAF3 and ASC, colocalized with them in discrete punctate structures in the cytoplasm, and facilitated ASC speck formation. TRAF3-dependent K63-linked ubiquitination of ASC was more pronounced in SARS-CoV-infected cells or when ORF3a was expressed. Taken together, our findings reveal a new mechanism by which SARS-CoV ORF3a protein activates NF-κB and the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of p105 and ASC.-Siu, K.-L., Yuen, K.-S., Castaño-Rodriguez, C., Ye, Z.-W., Yeung, M.-L., Fung, S.-Y., Yuan, S., Chan, C.-P., Yuen, K.-Y., Enjuanes, L., Jin, D.-Y. Severe acute respiratory syndrome coronavirus ORF3a protein activates the NLRP3 inflammasome by promoting TRAF3-dependent ubiquitination of ASC.

Middle East respiratory syndrome coronavirus and bat coronavirus HKU9 both can utilize GRP78 for attachment onto host cells.

Coronavirus tropism is predominantly determined by the interaction between coronavirus spikes and the host receptors. In this regard, coronaviruses have evolved a complicated receptor-recognition system through their spike proteins. Spikes from highly related coronaviruses can recognize distinct receptors, whereas spikes of distant coronaviruses can employ the same cell-surface molecule for entry. Moreover, coronavirus spikes can recognize a broad range of cell-surface molecules in addition to the receptors and thereby can augment coronavirus attachment or entry. The receptor of Middle East respiratory syndrome coronavirus (MERS-CoV) is dipeptidyl peptidase 4 (DPP4). In this study, we identified membrane-associated 78-kDa glucose-regulated protein (GRP78) as an additional binding target of the MERS-CoV spike. Further analyses indicated that GRP78 could not independently render nonpermissive cells susceptible to MERS-CoV infection but could facilitate MERS-CoV entry into permissive cells by augmenting virus attachment. More importantly, by exploring potential interactions between GRP78 and spikes of other coronaviruses, we discovered that the highly conserved human GRP78 could interact with the spike protein of bat coronavirus HKU9 (bCoV-HKU9) and facilitate its attachment to the host cell surface. Taken together, our study has identified GRP78 as a host factor that can interact with the spike proteins of two Betacoronaviruses, the lineage C MERS-CoV and the lineage D bCoV-HKU9. The capacity of GRP78 to facilitate surface attachment of both a human coronavirus and a phylogenetically related bat coronavirus exemplifies the need for continuous surveillance of the evolution of animal coronaviruses to monitor their potential for human adaptations.

Integrated analysis of mRNA-seq and miRNA-seq for host susceptibilities to influenza A (H7N9) infection in inbred mouse lines.

Host genetic factors play an important role in diverse host outcomes after influenza A (H7N9) infection. Studying differential responses of inbred mouse lines with distinct genetic backgrounds to influenza virus infection could substantially increase our understanding of the contributory roles of host genetic factors to disease severity. Here, we utilized an integrated approach of mRNA-seq and miRNA-seq to investigate the transcriptome expression and regulation of host genes in C57BL/6J and DBA/2J mouse strains during influenza virus infection. The differential pathogenicity of influenza virus in C57BL/6J and DBA/2J has been fully demonstrated through immunohistochemical staining, histopathological analyses, and viral replication assessment. A transcriptional molecular signature correlates to differential host response to infection has been uncovered. With the introduction of temporal expression pattern analysis, we demonstrated that host factors responsible for influenza virus replication and host-virus interaction were significantly enriched in genes exhibiting distinct temporal dynamics between different inbred mouse lines. A combination of time-series expression analysis and temporal expression pattern analysis has provided a list of promising candidate genes for future studies. An integrated miRNA regulatory network from both mRNA-seq and miRNA-seq revealed several regulatory modules responsible for regulating host susceptibilities and disease severity. Overall, a comprehensive framework for analyzing host susceptibilities to influenza infection was established by integrating mRNA-seq and miRNA-seq data of inbred mouse lines. This work suggests novel putative molecular targets for therapeutic interventions in seasonal and pandemic influenza.

Carcinoembryonic Antigen-Related Cell Adhesion Molecule 5 Is an Important Surface Attachment Factor That Facilitates Entry of Middle East Respiratory Syndrome Coronavirus.

UNLABELLED: The spike proteins of coronaviruses are capable of binding to a wide range of cellular targets, which contributes to the broad species tropism of coronaviruses. Previous reports have demonstrated that Middle East respiratory syndrome coronavirus (MERS-CoV) predominantly utilizes dipeptidyl peptidase 4 (DPP4) for cell entry. However, additional cellular binding targets of the MERS-CoV spike protein that may augment MERS-CoV infection have not been further explored. In the current study, using the virus overlay protein binding assay (VOPBA), we identified carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) as a novel cell surface binding target of MERS-CoV. CEACAM5 coimmunoprecipitated with the spike protein of MERS-CoV in both overexpressed and endogenous settings. Disrupting the interaction between CEACAM5 and MERS-CoV spike with anti-CEACAM5 antibody, recombinant CEACAM5 protein, or small interfering RNA (siRNA) knockdown of CEACAM5 significantly inhibited the entry of MERS-CoV. Recombinant expression of CEACAM5 did not render nonpermissive baby hamster kidney (BHK21) cells susceptible to MERS-CoV infection. Instead, CEACAM5 overexpression significantly enhanced the attachment of MERS-CoV to the BHK21 cells. More importantly, the entry of MERS-CoV was increased when CEACAM5 was overexpressed in permissive cells, which suggested that CEACAM5 could facilitate MERS-CoV entry in conjunction with DPP4 despite not being able to support MERS-CoV entry independently. Taken together, the results of our study identified CEACAM5 as a novel cell surface binding target of MERS-CoV that facilitates MERS-CoV infection by augmenting the attachment of the virus to the host cell surface. IMPORTANCE: Infection with the Middle East respiratory syndrome coronavirus (MERS-CoV) is associated with the highest mortality rate among all known human-pathogenic coronaviruses. Currently, there are no approved vaccines or therapeutics against MERS-CoV infection. The identification of carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) as a novel cell surface binding target of MERS-CoV advanced our knowledge on the cell binding biology of MERS-CoV. Importantly, CEACAM5 could potentiate the entry of MERS-CoV by functioning as an attachment factor. In this regard, CEACAM5 could serve as a novel target, in addition to dipeptidyl peptidase-4 (DPP4), in the development of antiviral strategies for MERS-CoV.

Middle East Respiratory Syndrome Coronavirus Efficiently Infects Human Primary T Lymphocytes and Activates the Extrinsic and Intrinsic Apoptosis Pathways.

Middle East respiratory syndrome (MERS) is associated with a mortality rate of >35%. We previously showed that MERS coronavirus (MERS-CoV) could infect human macrophages and dendritic cells and induce cytokine dysregulation. Here, we further investigated the interplay between human primary T cells and MERS-CoV in disease pathogenesis. Importantly, our results suggested that MERS-CoV efficiently infected T cells from the peripheral blood and from human lymphoid organs, including the spleen and the tonsil. We further demonstrated that MERS-CoV infection induced apoptosis in T cells, which involved the activation of both the extrinsic and intrinsic apoptosis pathways. Remarkably, immunostaining of spleen sections from MERS-CoV-infected common marmosets demonstrated the presence of viral nucleoprotein in their CD3(+) T cells. Overall, our results suggested that the unusual capacity of MERS-CoV to infect T cells and induce apoptosis might partly contribute to the high pathogenicity of the virus.

Treatment With Lopinavir/Ritonavir or Interferon-ß1b Improves Outcome of MERS-CoV Infection in a Nonhuman Primate Model of Common Marmoset.

Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe disease in human with an overall case-fatality rate of >35%. Effective antivirals are crucial for improving the clinical outcome of MERS. Although a number of repurposed drugs, convalescent-phase plasma, antiviral peptides, and neutralizing antibodies exhibit anti-MERS-CoV activity in vitro, most are not readily available or have not been evaluated in nonhuman primates. We assessed 3 repurposed drugs with potent in vitro anti-MERS-CoV activity (mycophenolate mofetil [MMF], lopinavir/ritonavir, and interferon-ß1b) in common marmosets with severe disease resembling MERS in humans. The lopinavir/ritonavir-treated and interferon-ß1b-treated animals had better outcome than the untreated animals, with improved clinical (mean clinical scores ↓50.9%-95.0% and ↓weight loss than the untreated animals), radiological (minimal pulmonary infiltrates), and pathological (mild bronchointerstitial pneumonia) findings, and lower mean viral loads in necropsied lung (↓0.59-1.06 log10 copies/glyceraldehyde 3-phosphate dehydrogenase [GAPDH]; P < .050) and extrapulmonary (↓0.11-1.29 log10 copies/GAPDH; P < .050 in kidney) tissues. In contrast, all MMF-treated animals developed severe and/or fatal disease with higher mean viral loads (↑0.15-0.54 log10 copies/GAPDH) than the untreated animals. The mortality rate at 36 hours postinoculation was 67% (untreated and MMF-treated) versus 0-33% (lopinavir/ritonavir-treated and interferon-ß1b-treated). Lopinavir/ritonavir and interferon-ß1b alone or in combination should be evaluated in clinical trials. MMF alone may worsen MERS and should not be used.

Development and Evaluation of Novel Real-Time Reverse Transcription-PCR Assays with Locked Nucleic Acid Probes Targeting Leader Sequences of Human-Pathogenic Coronaviruses.

Based on findings in small RNA-sequencing (Seq) data analysis, we developed highly sensitive and specific real-time reverse transcription (RT)-PCR assays with locked nucleic acid probes targeting the abundantly expressed leader sequences of Middle East respiratory syndrome coronavirus (MERS-CoV) and other human coronaviruses. Analytical and clinical evaluations showed their noninferiority to a commercial multiplex PCR test for the detection of these coronaviruses.

Middle east respiratory syndrome coronavirus 4a protein is a double-stranded RNA-binding protein that suppresses PACT-induced activation of RIG-I and MDA5 in the innate antiviral response.

UNLABELLED: Middle East respiratory syndrome coronavirus (MERS-CoV) is an emerging pathogen that causes severe disease in human. MERS-CoV is closely related to bat coronaviruses HKU4 and HKU5. Evasion of the innate antiviral response might contribute significantly to MERS-CoV pathogenesis, but the mechanism is poorly understood. In this study, we characterized MERS-CoV 4a protein as a novel immunosuppressive factor that antagonizes type I interferon production. MERS-CoV 4a protein contains a double-stranded RNA-binding domain capable of interacting with poly(I · C). Expression of MERS-CoV 4a protein suppressed the interferon production induced by poly(I · C) or Sendai virus. RNA binding of MERS-CoV 4a protein was required for IFN antagonism, a property shared by 4a protein of bat coronavirus HKU5 but not by the counterpart in bat coronavirus HKU4. MERS-CoV 4a protein interacted with PACT in an RNA-dependent manner but not with RIG-I or MDA5. It inhibited PACT-induced activation of RIG-I and MDA5 but did not affect the activity of downstream effectors such as RIG-I, MDA5, MAVS, TBK1, and IRF3. Taken together, our findings suggest a new mechanism through which MERS-CoV employs a viral double-stranded RNA-binding protein to circumvent the innate antiviral response by perturbing the function of cellular double-stranded RNA-binding protein PACT. PACT targeting might be a common strategy used by different viruses, including Ebola virus and herpes simplex virus 1, to counteract innate immunity. IMPORTANCE: Middle East respiratory syndrome coronavirus (MERS-CoV) is an emerging and highly lethal human pathogen. Why MERS-CoV causes severe disease in human is unclear, and one possibility is that MERS-CoV is particularly efficient in counteracting host immunity, including the sensing of virus invasion. It will therefore be critical to clarify how MERS-CoV cripples the host proteins that sense viruses and to compare MERS-CoV with its ancestral viruses in bats in the counteraction of virus sensing. This work not only provides a new understanding of the abilities of MERS-CoV and closely related bat viruses to subvert virus sensing but also might prove useful in revealing new strategies for the development of vaccines and antivirals.

The extent of sequence complementarity correlates with the potency of cellular miRNA-mediated restriction of HIV-1.

MicroRNAs (miRNAs) are 22-nt non-coding RNAs involved in the regulation of cellular gene expression and potential cellular defense against viral infection. Using in silico analyses, we predicted target sites for 22 human miRNAs in the HIV genome. Transfection experiments using synthetic miRNAs showed that five of these miRNAs capably decreased HIV replication. Using one of these five miRNAs, human miR-326 as an example, we demonstrated that the degree of complementarity between the predicted viral sequence and cellular miR-326 correlates, in a Dicer-dependent manner, with the potency of miRNA-mediated restriction of viral replication. Antagomirs to miR-326 that knocked down this cell endogenous miRNA increased HIV-1 replication in cells, suggesting that miR-326 is physiologically functional in moderating HIV-1 replication in human cells.

Differential cell line susceptibility to the emerging novel human betacoronavirus 2c EMC/2012: implications for disease pathogenesis and clinical manifestation.

The emerging novel human betacoronavirus 2c EMC/2012 (HCoV-EMC) was recently isolated from patients with severe pneumonia and renal failure and was associated with an unexplained high crude fatality rate of 56%. We performed a cell line susceptibility study with 28 cell lines. HCoV-EMC was found to infect the human respiratory tract (polarized airway epithelium cell line Calu-3, embryonic fibroblast cell line HFL, and lung adenocarcinoma cell line A549), kidney (embryonic kidney cell line HEK), intestinal tract (colorectal adenocarcinoma cell line Caco-2), liver cells (hepatocellular carcinoma cell line Huh-7), and histiocytes (malignant histiocytoma cell line His-1), as evident by detection of high or increasing viral load in culture supernatants, detection of viral nucleoprotein expression by immunostaining, and/or detection of cytopathic effects. Although an infected human neuronal cell line (NT2) and infected monocyte and T lymphocyte cell lines (THP-1, U937, and H9) had increased viral loads, their relatively lower viral production corroborated with absent nucleoprotein expression and cytopathic effects. This range of human tissue tropism is broader than that for all other HCoVs, including SARS coronavirus, HCoV-OC43, HCoV-HKU1, HCoV-229E, and HCoV-NL63, which may explain the high mortality associated with this disease. A recent cell line susceptibility study showed that HCoV-EMC can infect primate, porcine, and bat cells and therefore may jump interspecies barriers. We found that HCoV-EMC can also infect civet lung fibroblast and rabbit kidney cell lines. These findings have important implications for the diagnosis, pathogenesis, and transmission of HCoV-EMC.

Mycolyltransferase is important for biofilm formation and pathogenesis of Tsukamurella keratitis.

Tsukamurella, a group of multi-drug resistant, Gram-positive, aerobic, and partially acid-fast bacteria, are emerging causes of bacterial conjunctivitis and keratitis. However, the pathogenesis of Tsukamurella keratitis is largely unknown. To address this, we used New Zealand White rabbits to develop the first eye infection model and conducted in vitro tests to study the pathogenesis mechanisms of Tsukamurella. There is increasing evidence that biofilms play a significant role in ocular infections, leading us to hypothesize that biofilm formation is crucial for effective Tsukamurella infection. In order to look for potential candidate genes which are important in biofilm formation and Tsukamurella keratitis. We performed genome sequencing of two ocular isolates, T. pulmonis-PW1004 and T. tyrosinosolvens-PW899, to identify potential virulence factors. Through in vitro and in vivo studies, we characterized their biological roles in mediating Tsukamurella keratitis. Our findings confirmed that Tsukamurella is an ocular pathogen by fulfilling Koch's postulates, and using genome sequence data, we identified tmytC, encoding a mycolyltransferase, as a crucial gene in biofilm formation and causing Tsukamurella keratitis in the rabbit model. This is the first report demonstrating the novel role of mycolyltransferase in causing ocular infections. Overall, our findings contribute to a better understanding of Tsukamurella pathogenesis and provide a potential target for treatment. Specific inhibitors targeting TmytC could serve as an effective treatment option for Tsukamurella infections.

Natural occurrence and characterization of two internal ribosome entry site elements in a novel virus, canine picodicistrovirus, in the picornavirus-like superfamily.

Dicistroviridae and Picornaviridae are two phylogenetically related families of positive-sense single-stranded RNA viruses in the picornavirus-like superfamily with similar gene contents but different genome organizations and hosts. In a surveillance study involving 1,472 samples from 368 dogs over a 22-month period, we identified a novel picornavirus-like virus from 47 fecal and urine samples by the use of reverse transcription-PCR (RT-PCR). Sequencing and phylogenetic analysis of three complete genomes revealed that, although it seemed that the virus was most closely related to other picornaviruses, P1, P2, and P3 of the virus possessed very low amino acid identities of <30% to those of all other known picornaviruses and that the amino acid identities between the 3D(pol) and 2C of the virus and the RNA-dependent RNA polymerases and helicases of all other picornaviruses were <35%. Distinct from other picornaviruses, the genomes of the virus contain two putative internal ribosome entry sites (IRESs) and two open reading frames, encoding two polyprotein precursors (844 and 1,406 amino acids), separated by an intergenic region (IGR) of 588 bases. A dual-luciferase activity assay using DNA and RNA transfection revealed that both IRESs were functional. Quantitative RT-PCR showed that numbers of viral RNAs ranged from 7.55 × 10(6) to 1.26 × 10(9) copies/ml of urine and 1.82 × 10(6) to 4.97 × 10(10) copies/ml of fecal sample. This is the first report of the natural occurrence of two functional IRESs in nondicistroviruses. Based on our results, we have proposed a novel species, canine picodicistrovirus (CPDV), to describe this novel member of the picornavirus-like superfamily, which could represent a novel family of viruses.

Usefulness of Next-Generation Sequencing in Excluding Bovine Leukemia Virus as a Cause of Adult Camel Leukosis in Dromedaries.

Adult camel leukosis is an emerging hematological and neoplastic disease in dromedaries. It has been hypothesized that bovine leukemia virus (BLV) or its genetic variants may be associated with adult camel leukosis. In this study, we used next-generation sequencing (NGS) to detect all possible viruses in five lung samples from five dromedaries with histopathological evidence of adult camel leukosis and four tissue samples from two control dromedaries. A total throughput of 114.7 Gb was achieved, with an average of 12.7 Gb/sample. For each sample, all the pair-end 151-bp reads were filtered to remove rRNA sequences, bacterial genomes and redundant sequences, resulting in 1-7 Gb clean reads, of which <3% matched to viruses. The largest portion of these viral sequences was composed of bacterial phages. About 100-300 reads in each sample matched "multiple sclerosis-associated retrovirus", but manual analysis showed that they were only repetitive sequences commonly present in mammalian genomes. All viral reads were also extracted for analysis, confirming that no BLV or its genetic variants or any other virus was detected in the nine tissue samples. NGS is not only useful for detecting microorganisms associated with infectious diseases, but also important for excluding an infective cause in scenarios where such a possibility is suspected.

An IgM-like inhalable ACE2 fusion protein broadly neutralizes SARS-CoV-2 variants.

Many of the currently available COVID-19 vaccines and therapeutics are not effective against newly emerged SARS-CoV-2 variants. Here, we developed the metallo-enzyme domain of angiotensin converting enzyme 2 (ACE2)-the cellular receptor of SARS-CoV-2-into an IgM-like inhalable molecule (HH-120). HH-120 binds to the SARS-CoV-2 Spike (S) protein with high avidity and confers potent and broad-spectrum neutralization activity against all known SARS-CoV-2 variants of concern. HH-120 was developed as an inhaled formulation that achieves appropriate aerodynamic properties for rodent and monkey respiratory system delivery, and we found that early administration of HH-120 by aerosol inhalation significantly reduced viral loads and lung pathology scores in male golden Syrian hamsters infected by the SARS-CoV-2 ancestral strain (GDPCC-nCoV27) and the Delta variant. Our study presents a meaningful advancement in the inhalation delivery of large biologics like HH-120 (molecular weight (MW) ~ 1000 kDa) and demonstrates that HH-120 can serve as an efficacious, safe, and convenient agent against SARS-CoV-2 variants. Finally, given the known role of ACE2 in viral reception, it is conceivable that HH-120 has the potential to be efficacious against additional emergent coronaviruses.