Pesti, A;Danics, K;Glasz, T;Várkonyi, T;Barbai, T;Reszegi, A;Kovalszky, I;Vályi-Nagy, I;Dobi, D;Lotz, G;Schaff, Z;Kiss, A;
PMID: 36527584 | DOI: 10.1007/s11357-022-00700-6
The most severe alterations in Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome Coronavirus-2 (SARS-CoV-2) infection are seen in the lung. However, other organs also are affected. Here, we report histopathologic findings in the liver and detection of viral proteins and RNA in COVID-19 autopsies performed at the Semmelweis University (Budapest, Hungary). Between March 2020 through March 2022, 150 autopsies on patients who died of COVID-19 were analyzed. Cause-of-death categories were formed based on the association with SARS-CoV-2 as strong, contributive, or weak. Samples for histopathologic study were obtained from all organs, fixed in formalin, and embedded in paraffin (FFPE). Immunohistochemical study (IHC) to detect SARS-CoV-2 spike protein and nucleocapsid protein (NP), CD31, claudin-5, factor VIII, macrosialin (CD68), and cytokeratin 7, with reverse transcriptase polymerase chain reaction (RT-PCR), and in situ hybridization (ISH, RNAscope ) for SARS-CoV-2 RNA were conducted using FFPE samples of livers taken from 20 autopsies performed ≤ 2 days postmortem. All glass slides were scanned; the digital images were evaluated by semiquantitative scoring and scores were analyzed statistically. Steatosis, single-cell and focal/zonal hepatocyte necrosis, portal fibrosis, and chronic inflammation were found in varying percentages. Sinusoidal ectasia, endothelial cell disruption, and fibrin-filled sinusoids were seen in all cases; these were assessed semiquantitatively for severity (SEF scored). SEF scores did not correlate with cause-of-death categories (p = 0.92) or with severity of lung alterations (p = 0.96). SARS-CoV-2 RNA was detected in 13/20 cases by PCR and in 9/20 by ISH, with IHC demonstration of spike protein in 4/20 cases and NP in 15/20. Viral RNA and proteins were located in endothelial and Kupffer cells, and in portal macrophages, but not in hepatocytes and cholangiocytes. In conclusion, endothelial damage (SEF scores) was the most common alteration in the liver and was a characteristic, but not specific alteration in COVID-19, suggesting an important role in the pathogenesis of COVID-19-associated liver disease. Detection of SARS-CoV-2 RNA and viral proteins in liver non-parenchymal cells suggests that while the most extended primary viral cytotoxic effect occurs in the lung, viral components are present in other organs too, as in the liver. The necrosis/apoptosis and endothelial damage associated with viral infection in COVID-19 suggest that those patients who survive more severe COVID-19 may face prolonged liver repair and accordingly should be followed regularly in the post-COVID period.
McMahan, K;Giffin, V;Tostanoski, LH;Chung, B;Siamatu, M;Suthar, MS;Halfmann, P;Kawaoka, Y;Piedra-Mora, C;Jain, N;Ducat, S;Kar, S;Andersen, H;Lewis, MG;Martinot, AJ;Barouch, DH;
PMID: 35313451 | DOI: 10.1016/j.medj.2022.03.004
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.Hamsters were inoculated with either SARS-CoV-2 Omicron or other SARS-CoV-2 variants. Animals were followed for weight loss, and upper and lower respiratory tract tissues were assessed for viral loads and histopathology.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. 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 led to substantial viral replication in both the upper and lower respiratory tracts but demonstrated lower viral loads in lung parenchyma and reduced pulmonary pathology compared with WA1/2020 infection.These data suggest that the SARS-CoV-2 Omicron variant may result in robust upper respiratory tract infection but less severe lower respiratory tract clinical disease compared with prior SARS-CoV-2 variants.Funding for this study was provided by NIH grant CA260476, the Massachusetts Consortium for Pathogen Readiness, the Ragon Institute, and the Musk Foundation.
Laboratory investigation; a journal of technical methods and pathology
Granai, M;Warm, V;Vogelsberg, A;Milla, J;Greif, K;Vogel, U;Bakchoul, T;Rosenberger, P;Quintanilla-Martinez, L;Schürch, C;Klingel, K;Fend, F;Bösmüller, H;
PMID: 37224922 | DOI: 10.1016/j.labinv.2023.100179
In critically ill SARS-CoV-2 infected patients, early leukocyte recruitment to the respiratory system was found to be orchestrated by leukocyte trafficking molecules accompanied by massive secretion of pro-inflammatory cytokines and hypercoagulability. Our study aimed to explore the interplay between leukocyte activation and pulmonary endothelium in different disease stages of fatal COVID-19. Our study comprised 10 COVID-19 post-mortem lung specimens and 20 control lung samples (5 ARDS, 2 viral pneumonia, 3 bacterial pneumonia, and 10 normal) which were stained for antigens representing the different steps of leucocyte migration: E-selectin, P-selectin, PSGL-1, ICAM1, VCAM1, and CD11b. Image analysis software QuPath was used for quantification of positive leukocytes (PSGL-1 and CD11b) and endothelium (E-selectin, P-selectin, ICAM1, VCAM1). Expression of IL-6 and IL-1ß was quantified by qRT-PCR. Expression of P-selectin and PSGL-1 was strongly increased in the COVID-19 cohort compared to all control groups (ratio =17,23, p<0,0001; ratio=2,75, p<0,0001 respectively). Importantly, P-selectin was found in endothelial cells and associated with aggregates of activated platelets adherent to the endothelial surface in COVID-19 cases. In addition, PSGL-1 staining disclosed positive perivascular leucocyte cuffs, reflecting capillaritis. Moreover, CD11b showed a strongly increased positivity in COVID-19 compared to all controls (ratio=2,89; p=0,0002), indicating a proinflammatory immune microenvironment. Of note, CD11b exhibited distinct staining patterns at different stages of COVID-19 disease. Only in cases with very short disease course, high levels of IL-1ß and IL-6 mRNA were observed in lung tissue. The striking upregulation of PSGL-1 and P-selectin reflects the activation of this receptor-ligand pair in COVID-19, increasing the efficiency of initial leucocyte recruitment, thus promoting tissue damage and immunothrombosis. Our results show that endothelial activation and unbalanced leukocyte migration play a central role in COVID-19 involving the P-selectin-PSGL-1 axis.
Kaewborisuth, C;Wanitchang, A;Koonpaew, S;Srisutthisamphan, K;Saenboonrueng, J;Im-Erbsin, R;Inthawong, M;Sunyakumthorn, P;Thaweerattanasinp, T;Tanwattana, N;Jantraphakorn, Y;Reed, MC;Lugo-Roman, LA;Hunsawong, T;Klungthong, C;Jones, AR;Fernandez, S;Teeravechyan, S;Lombardini, ED;Jongkaewwattana, A;
PMID: 35632541 | DOI: 10.3390/vaccines10050786
Virus-like particles (VLPs) are highly immunogenic and versatile subunit vaccines composed of multimeric viral proteins that mimic the whole virus but lack genetic material. Due to the lack of infectivity, VLPs are being developed as safe and effective vaccines against various infectious diseases. In this study, we generated a chimeric VLP-based COVID-19 vaccine stably produced by HEK293T cells. The chimeric VLPs contain the influenza virus A matrix (M1) proteins and the SARS-CoV-2 Wuhan strain spike (S) proteins with a deletion of the polybasic furin cleavage motif and a replacement of the transmembrane and cytoplasmic tail with that of the influenza virus hemagglutinin (HA). These resulting chimeric S-M1 VLPs, displaying S and M1, were observed to be enveloped particles that are heterogeneous in shape and size. The intramuscular vaccination of BALB/c mice in a prime-boost regimen elicited high titers of S-specific IgG and neutralizing antibodies. After immunization and a challenge with SARS-CoV-2 in K18-hACE2 mice, the S-M1 VLP vaccination resulted in a drastic reduction in viremia, as well as a decreased viral load in the lungs and improved survival rates compared to the control mice. Balanced Th1 and Th2 responses of activated S-specific T-cells were observed. Moderate degrees of inflammation and viral RNA in the lungs and brains were observed in the vaccinated group; however, brain lesion scores were less than in the PBS control. Overall, we demonstrate the immunogenicity of a chimeric VLP-based COVID-19 vaccine which confers strong protection against SARS-CoV-2 viremia in mice.
Chiba, S;Kiso, M;Nakajima, N;Iida, S;Maemura, T;Kuroda, M;Sato, Y;Ito, M;Okuda, M;Yamada, S;Iwatsuki-Horimoto, K;Watanabe, T;Imai, M;Armbrust, T;Baric, RS;Halfmann, PJ;Suzuki, T;Kawaoka, Y;
PMID: 35100870 | DOI: 10.1128/mbio.03044-21
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide since December 2019, causing coronavirus disease 2019 (COVID-19). Although vaccines for this virus have been developed rapidly, repurposing drugs approved to treat other diseases remains an invaluable treatment strategy. Here, we evaluated the inhibitory effects of drugs on SARS-CoV-2 replication in a hamster infection model and in in vitro assays. Favipiravir significantly suppressed virus replication in hamster lungs. Remdesivir inhibited virus replication in vitro, but was not effective in the hamster model. However, GS-441524, a metabolite of remdesivir, effectively suppressed virus replication in hamsters. Co-administration of favipiravir and GS-441524 more efficiently reduced virus load in hamster lungs than did single administration of either drug for both the prophylactic and therapeutic regimens; prophylactic co-administration also efficiently inhibited lung inflammation in the infected animals. Furthermore, pretreatment of hamsters with favipiravir and GS-441524 effectively protected them from virus transmission via respiratory droplets upon exposure to infected hamsters. Repurposing and co-administration of antiviral drugs may help combat COVID-19. IMPORTANCE During a pandemic, repurposing drugs that are approved for other diseases is a quick and realistic treatment option. In this study, we found that co-administration of favipiravir and the remdesivir metabolite GS-441524 more effectively blocked SARS-CoV-2 replication in the lungs of Syrian hamsters than either favipiravir or GS-441524 alone as part of a prophylactic or therapeutic regimen. Prophylactic co-administration also reduced the severity of lung inflammation. Moreover, co-administration of these drugs to naive hamsters efficiently protected them from airborne transmission of the virus from infected animals. Since both drugs are nucleotide analogs that interfere with the RNA-dependent RNA polymerases of many RNA viruses, these findings may also help encourage co-administration of antivirals to combat future pandemics.
Kawaoka, Y;Uraki, R;Kiso, M;Iida, S;Imai, M;Takashita, E;Kuroda, M;Halfmann, P;Loeber, S;Maemura, T;Yamayoshi, S;Fujisaki, S;Wang, Z;Ito, M;Ujie, M;Iwatsuki-Horimoto, K;Furusawa, Y;Wright, R;Chong, Z;Ozono, S;Yasuhara, A;Ueki, H;Sakai, Y;Li, R;Liu, Y;Larson, D;Koga, M;Tsutsumi, T;Adachi, E;Saito, M;Yamamoto, S;Matsubara, S;Hagihara, M;Mitamura, K;Sato, T;Hojo, M;Hattori, SI;Maeda, K;Okuda, M;Murakami, J;Duong, C;Godbole, S;Douek, D;Watanabe, S;Ohmagari, N;Yotsuyanagi, H;Diamond, M;Hasegawa, H;Mitsuya, H;Suzuki, T;
PMID: 35233565 | DOI: 10.21203/rs.3.rs-1375091/v1
The recent emergence of SARS-CoV-2 Omicron variants possessing large numbers of mutations has raised concerns of decreased effectiveness of current vaccines, therapeutic monoclonal antibodies, and antiviral drugs for COVID-19 against these variants1,2. While the original Omicron lineage, BA.1, has become dominant in many countries, BA.2 has been detected in at least 67 countries and has become dominant in the Philippines, India, and Denmark. Here, we evaluated the replicative ability and pathogenicity of an authentic infectious BA.2 isolate in immunocompetent and human ACE2 (hACE2)-expressing mice and hamsters. In contrast to recent data with chimeric, recombinant SARS-CoV-2 strains expressing the spike proteins of BA.1 and BA.2 on an ancestral WK-521 backbone3, we observed similar infectivity and pathogenicity in mice and hamsters between BA.2 and BA.1, and less pathogenicity compared to early SARS-CoV-2 strains. We also observed a marked and significant reduction in the neutralizing activity of plasma from COVID-19 convalescent individuals and vaccine recipients against BA.2 compared to ancestral and Delta variant strains. In addition, we found that some therapeutic monoclonal antibodies (REGN10987/REGN10933, COV2-2196/COV2-2130, and S309) and antiviral drugs (molnupiravir, nirmatrelvir, and S-217622) can restrict viral infection in the respiratory organs of hamsters infected with BA.2. These findings suggest that the replication and pathogenicity of BA.2 is comparable to that of BA.1 in rodents and that several therapeutic monoclonal antibodies and antiviral compounds are effective against Omicron/BA.2 variants.
Meseda, CA;Stauft, CB;Selvaraj, P;Lien, CZ;Pedro, C;Nuñez, IA;Woerner, AM;Wang, TT;Weir, JP;
PMID: 34862398 | DOI: 10.1038/s41541-021-00410-8
Numerous vaccine candidates against SARS-CoV-2, the causative agent of the COVID-19 pandemic, are under development. The majority of vaccine candidates to date are designed to induce immune responses against the viral spike (S) protein, although different forms of S antigen have been incorporated. To evaluate the yield and immunogenicity of different forms of S, we constructed modified vaccinia virus Ankara (MVA) vectors expressing full-length S (MVA-S), the RBD, and soluble S ectodomain and tested their immunogenicity in dose-ranging studies in mice. All three MVA vectors induced spike-specific immunoglobulin G after one subcutaneous immunization and serum titers were boosted following a second immunization. The MVA-S and MVA-ssM elicited the strongest neutralizing antibody responses. In assessing protective efficacy, MVA-S-immunized adult Syrian hamsters were challenged with SARS-CoV-2 (USA/WA1/2020). MVA-S-vaccinated hamsters exhibited less severe manifestations of atypical pneumocyte hyperplasia, hemorrhage, vasculitis, and especially consolidation, compared to control animals. They also displayed significant reductions in gross pathology scores and weight loss, and a moderate reduction in virus shedding was observed post challenge in nasal washes. There was evidence of reduced viral replication by in situ hybridization, although the reduction in viral RNA levels in lungs and nasal turbinates did not reach significance. Taken together, the data indicate that immunization with two doses of an MVA vector expressing SARS-CoV-2 S provides protection against a stringent SARS-CoV-2 challenge of adult Syrian hamsters, reaffirm the utility of this animal model for evaluating candidate SARS-CoV-2 vaccines, and demonstrate the value of an MVA platform in facilitating vaccine development against SARS-CoV-2.
Diamond, M;Halfmann, P;Maemura, T;Iwatsuki-Horimoto, K;Iida, S;Kiso, M;Scheaffer, S;Darling, T;Joshi, A;Loeber, S;Foster, S;Ying, B;Whitener, B;Floyd, K;Ujie, M;Nakajima, N;Ito, M;Wright, R;Uraki, R;Li, R;Sakai, Y;Liu, Y;Larson, D;Osorio, J;Hernandez-Ortiz, J;ÄŒiuoderis, K;Florek, K;Patel, M;Bateman, A;Odle, A;Wong, LY;Wang, Z;Edara, VV;Chong, Z;Thackray, L;Ueki, H;Yamayoshi, S;Imai, M;Perlman, S;Webby, R;Seder, R;Suthar, M;Garcia-Sastre, A;Schotsaert, M;Suzuki, T;Boon, A;Kawaoka, Y;Douek, D;Moliva, J;Sullivan, N;Gagne, M;Ransier, A;Case, J;Jeevan, T;Franks, J;Fabrizio, T;DeBeauchamp, J;Kercher, L;Seiler, P;Singh, G;Warang, P;Gonzalez-Reiche, AS;Sordillo, E;van Bakel, H;Simon, V;
PMID: 34981044 | DOI: 10.21203/rs.3.rs-1211792/v1
Despite the development and deployment of antibody and vaccine countermeasures, rapidly-spreading SARS-CoV-2 variants with mutations at key antigenic sites in the spike protein jeopardize their efficacy. The recent emergence of B.1.1.529, the Omicron variant1,2, which has more than 30 mutations in the spike protein, has raised concerns for escape from protection by vaccines and therapeutic antibodies. A key test for potential countermeasures against B.1.1.529 is their activity in pre-clinical rodent models of respiratory tract disease. Here, using the collaborative network of the SARS-CoV-2 Assessment of Viral Evolution (SAVE) program of the National Institute of Allergy and Infectious Diseases (NIAID), we evaluated the ability of multiple B.1.1.529 Omicron isolates to cause infection and disease in immunocompetent and human ACE2 (hACE2) expressing mice and hamsters. Despite modeling and binding data suggesting that B.1.1.529 spike can bind more avidly to murine ACE2, we observed attenuation of infection in 129, C57BL/6, and BALB/c mice as compared with previous SARS-CoV-2 variants, with limited weight loss and lower viral burden in the upper and lower respiratory tracts. Although K18-hACE2 transgenic mice sustained infection in the lungs, these animals did not lose weight. In wild-type and hACE2 transgenic hamsters, lung infection, clinical disease, and pathology with B.1.1.529 also were milder compared to historical isolates or other SARS-CoV-2 variants of concern. Overall, experiments from multiple independent laboratories of the SAVE/NIAID network with several different B.1.1.529 isolates demonstrate attenuated lung disease in rodents, which parallels preliminary human clinical data.
Shanmugaraj, B;Khorattanakulchai, N;Panapitakkul, C;Malla, A;Im-Erbsin, R;Inthawong, M;Sunyakumthorn, P;Hunsawong, T;Klungthong, C;Reed, MC;Kemthong, T;Suttisan, N;Malaivijitnond, S;Srimangkornkaew, P;Klinkhamhom, A;Manopwisedjaroen, S;Thitithanyanont, A;Taychakhoonavudh, S;Phoolcharoen, W;
PMID: 35697573 | DOI: 10.1016/j.vaccine.2022.05.087
Coronavirus disease 2019 (COVID-19) is an acute respiratory illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The prevention of SARS-CoV-2 transmission has become a global priority. Previously, we showed that a protein subunit vaccine that was developed based on the fusion of the SARS-CoV-2 receptor-binding domain (RBD) to the Fc portion of human IgG1 (RBD-Fc), produced in Nicotiana benthamiana, and adjuvanted with alum, namely, Baiya SARS-CoV-2 Vax 1, induced potent immunological responses in both mice and cynomolgus monkeys. Hence, this study evaluated the protective efficacy, safety, and toxicity of Baiya SARS-CoV-2 Vax 1 in K18-hACE2 mice, monkeys and Wistar rats. Two doses of vaccine were administered three weeks apart on Days 0 and 21. The administration of the vaccine to K18-hACE2 mice reduced viral loads in the lungs and brains of the vaccinated animals and protected the mice against challenge with SARS-CoV-2. In monkeys, the results of safety pharmacology tests, general clinical observations, and a core battery of studies of three vital systems, namely, the central nervous, cardiovascular, and respiratory systems, did not reveal any safety concerns. The toxicology study of the vaccine in rats showed no vaccine-related pathological changes, and all the animals remained healthy under the conditions of this study. Furthermore, the vaccine did not cause any abnormal toxicity in rats and was clinically tolerated even at the highest tested concentration. In addition, general health status, body temperature, local toxicity at the administration site, hematology, and blood chemistry parameters were also monitored. Overall, this work presents the results of the first systematic study of the safety profile of a plant-derived vaccine, Baiya SARS-CoV-2 Vax 1; this approach can be considered a viable strategy for the development of vaccines against COVID-19.
The American journal of pathology
Ball, EE;Weiss, CM;Liu, H;Jackson, K;Keel, MK;Miller, CJ;Van Rompay, KKA;Coffey, LL;Pesavento, PA;
PMID: 36906263 | DOI: 10.1016/j.ajpath.2023.02.013
Clinical evidence of vascular dysfunction and hypercoagulability as well as pulmonary vascular damage and microthrombosis are frequently reported in severe cases of human coronavirus disease 2019 (COVID-19). Syrian golden hamsters recapitulate histopathologic pulmonary vascular lesions reported in patients with COVID-19. Here, special staining techniques and transmission electron microscopy further define vascular pathologies in a Syrian golden hamster model of human COVID-19. The results show that regions of active pulmonary inflammation in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are characterized by ultrastructural evidence of endothelial damage with platelet marginalization and both perivascular and subendothelial macrophage infiltration. SARS-CoV-2 antigen/RNA was not detectable within affected blood vessels. Taken together, these findings suggest that the prominent microscopic vascular lesions in SARS-CoV-2-inoculated hamsters are likely due to endothelial damage followed by platelet and macrophage infiltration.
Nature biomedical engineering
Wang, Z;Popowski, KD;Zhu, D;de Juan Abad, BL;Wang, X;Liu, M;Lutz, H;De Naeyer, N;DeMarco, CT;Denny, TN;Dinh, PC;Li, Z;Cheng, K;
PMID: 35788687 | DOI: 10.1038/s41551-022-00902-5
The first two mRNA vaccines against infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that were approved by regulators require a cold chain and were designed to elicit systemic immunity via intramuscular injection. Here we report the design and preclinical testing of an inhalable virus-like-particle as a COVID-19 vaccine that, after lyophilisation, is stable at room temperature for over three months. The vaccine consists of a recombinant SARS-CoV-2 receptor-binding domain (RBD) conjugated to lung-derived exosomes which, with respect to liposomes, enhance the retention of the RBD in both the mucus-lined respiratory airway and in lung parenchyma. In mice, the vaccine elicited RBD-specific IgG antibodies, mucosal IgA responses and CD4+ and CD8+ T cells with a Th1-like cytokine expression profile in the animals' lungs, and cleared them of SARS-CoV-2 pseudovirus after a challenge. In hamsters, two doses of the vaccine attenuated severe pneumonia and reduced inflammatory infiltrates after a challenge with live SARS-CoV-2. Inhalable and room-temperature-stable virus-like particles may become promising vaccine candidates.
Halfmann, PJ;Iida, S;Iwatsuki-Horimoto, K;Maemura, T;Kiso, M;Scheaffer, SM;Darling, TL;Joshi, A;Loeber, S;Singh, G;Foster, SL;Ying, B;Case, JB;Chong, Z;Whitener, B;Moliva, J;Floyd, K;Ujie, M;Nakajima, N;Ito, M;Wright, R;Uraki, R;Warang, P;Gagne, M;Li, R;Sakai-Tagawa, Y;Liu, Y;Larson, D;Osorio, JE;Hernandez-Ortiz, JP;Henry, AR;Ciouderis, K;Florek, KR;Patel, M;Odle, A;Wong, LR;Bateman, AC;Wang, Z;Edara, VV;Chong, Z;Franks, J;Jeevan, T;Fabrizio, T;DeBeauchamp, J;Kercher, L;Seiler, P;Gonzalez-Reiche, AS;Sordillo, EM;Chang, LA;van Bakel, H;Simon, V;Consortium Mount Sinai Pathogen Surveillance (PSP) study group, ;Douek, DC;Sullivan, NJ;Thackray, LB;Ueki, H;Yamayoshi, S;Imai, M;Perlman, S;Webby, RJ;Seder, RA;Suthar, MS;García-Sastre, A;Schotsaert, M;Suzuki, T;Boon, ACM;Diamond, MS;Kawaoka, Y;
PMID: 35062015 | DOI: 10.1038/s41586-022-04441-6
The recent emergence of B.1.1.529, the Omicron variant1,2 has raised concerns for escape from protection by vaccines and therapeutic antibodies. A key test for potential countermeasures against B.1.1.529 is their activity in pre-clinical rodent models of respiratory tract disease. Here, using the collaborative network of the SARS-CoV-2 Assessment of Viral Evolution (SAVE) program of the National Institute of Allergy and Infectious Diseases (NIAID), we evaluated the ability of multiple B.1.1.529 Omicron isolates to cause infection and disease in immunocompetent and human ACE2 (hACE2) expressing mice and hamsters. Despite modeling data suggesting that B.1.1.529 spike can bind more avidly to murine ACE23,4, we observed less infection in 129, C57BL/6, BALB/c, and K18-hACE2 transgenic mice as compared with previous SARS-CoV-2 variants, with limited weight loss and lower viral burden in the upper and lower respiratory tracts. In wild-type and hACE2 transgenic hamsters, lung infection, clinical disease, and pathology with B.1.1.529 also were milder compared to historical isolates or other SARS-CoV-2 variants of concern. Overall, experiments from the SAVE/NIAID network with several B.1.1.529 isolates demonstrate attenuated lung disease in rodents, which parallels preliminary human clinical data.
