The impact of primary immunization route on the outcome of infection with SARS-CoV-2 in a hamster model of COVID-19.

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has resulted in over 6.7 million deaths worldwide. COVID-19 vaccines administered parenterally via intramuscular or subcutaneous (SC) routes have reduced the severity of respiratory infections, hospitalization rates, and overall mortality. However, there is a growing interest in developing mucosally delivered vaccines to further enhance the ease and durability of vaccination. This study compared the immune response in hamsters immunized with live SARS-CoV-2 virus via SC or intranasal (IN) routes and assessed the outcome of a subsequent IN SARS-CoV-2 challenge. Results showed that SC-immunized hamsters elicited a dose-dependent neutralizing antibody response but of a significantly lower magnitude than that observed in IN-immunized hamsters. The IN challenge with SARS-CoV-2 in SC-immunized hamsters resulted in body weight loss, increased viral load, and lung pathology than that observed in IN-immunized and IN-challenged counterparts. These results demonstrate that while SC immunization renders some degree of protection, IN immunization induces a stronger immune response and better protection against respiratory SARS-CoV-2 infection. Overall, this study provides evidence that the route of primary immunization plays a critical role in determining the severity of a subsequent respiratory infection caused by SARS-CoV-2. Furthermore, the findings suggest that IN route of immunization may be a more effective option for COVID-19 vaccines than the currently used parenteral routes. Understanding the immune response to SARS-CoV-2 elicited via different immunization routes may help guide more effective and long-lasting vaccination strategies.

Evaluation of Efficacy of the Amino Acid-Peptide Complex Administered Intragastrically to Golden Hamsters Experimentally Infected with Sars-Cov-2

The development of coronavirus infection outbreak into a pandemic, coupled with the lack of effective COVID-19 therapies, is a challenge for the entire pharmaceutical industry. This study aimed to assess the treatment and preventive efficacy of the amino acid-peptide complex (APC) in male Syrian hamsters infected with SARSCoV-2 (intranasal administration of 26 mul of the virus culture, titer of 4 x 104 TCD50/ml). In a modeled COVID-19 case, APC administered for treatment and preventive purposes reduced lung damage. Compared to the positive control group, test group had the lung weight factor 15.2% smaller (trend), which indicates a less pronounced edema. Microscopic examination revealed no alveolar edema, atypical hypertrophied forms of type II alveolocytes, pulmonary parenchyma fibrinization. The macrophage reaction intensified, which is probably a result of the APC-induced activation of regenerative processes in the lung tissues. Spleens of the animals that received APC for therapeutic and preventive purposes were less engorged and had fewer hemorrhages. The decrease of body weight of the test animals that received APC for treatment and prevention was insignificant (p < 0.05), which indicates a less severe course of COVID-19. Administered following a purely therapeutic protocol, APC proved ineffective against SARS-CoV-2 post-infection. Thus, APC-based drug used as a therapeutic and preventive agent reduces pulmonary edema and makes morphological signs of lung tissue damage less pronounced in male Syrian hamsters infected with SARS-CoV-2.Copyright © Extreme Medicine.All right reserved.

Omicron BA.1 and BA.2 sub-lineages show reduced pathogenicity and transmission potential than the early SARS-CoV-2 D614G variant in Syrian hamsters.

BACKGROUND: The epidemiological advantage of Omicron variant is evidenced by its rapid spread and the ability to outcompete prior variants. Among Omicron sub-lineages, early outbreaks were dominated by BA.1 while BA.2 has gained dominance since February 2022. The relative pathogenicity and transmissibility of BA.1 and BA.2 have not been fully defined. METHODS: We compared viral loads and clinical signs in Syrian hamsters after infection with BA.1, BA.2, or D614G variant. A competitive transmission model and next generation sequencing were used to compare the relative transmission potential of BA.1 and BA.2. RESULTS: BA.1 and BA.2 caused no apparent clinical signs while D614G caused more than 10% weight loss. Higher viral loads were detected from the nasal washes, nasal turbinate and lungs of BA.1 than BA.2 inoculated hamsters. No aerosol transmission was observed for BA.1 or BA.2 under the experimental condition that D614G transmitted efficiently. BA.1 and BA.2 were able to transmit among hamsters via direct contact; however, BA.1 transmitted more efficiently than BA.2 under the competitive transmission model. No recombination was detected from direct contacts exposed simultaneously to BA.1 and BA.2. CONCLUSIONS: Omicron BA.1 and BA.2 demonstrated attenuated pathogenicity and reduced transmission potential in hamsters when compared to early SARS-CoV-2 strains.

Longitudinal analyses using 18F-Fluorodeoxyglucose positron emission tomography with computed tomography as a measure of COVID-19 severity in the aged, young, and humanized ACE2 SARS-CoV-2 hamster models.

This study compared disease progression of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in three different models of golden hamsters: aged (≈60 weeks old) wild-type (WT), young (6 weeks old) WT, and adult (14-22 weeks old) hamsters expressing the human-angiotensin-converting enzyme 2 (hACE2) receptor. After intranasal (IN) exposure to the SARS-CoV-2 Washington isolate (WA01/2020), 2-deoxy-2-[fluorine-18]fluoro-D-glucose positron emission tomography with computed tomography (18F-FDG PET/CT) was used to monitor disease progression in near real time and animals were euthanized at pre-determined time points to directly compare imaging findings with other disease parameters associated with coronavirus disease 2019 (COVID-19). Consistent with histopathology, 18F-FDG-PET/CT demonstrated that aged WT hamsters exposed to 105 plaque forming units (PFU) developed more severe and protracted pneumonia than young WT hamsters exposed to the same (or lower) dose or hACE2 hamsters exposed to a uniformly lethal dose of virus. Specifically, aged WT hamsters presented with a severe interstitial pneumonia through 8 d post-exposure (PE), while pulmonary regeneration was observed in young WT hamsters at that time. hACE2 hamsters exposed to 100 or 10 PFU virus presented with a minimal to mild hemorrhagic pneumonia but succumbed to SARS-CoV-2-related meningoencephalitis by 6 d PE, suggesting that this model might allow assessment of SARS-CoV-2 infection on the central nervous system (CNS). Our group is the first to use (18F-FDG) PET/CT to differentiate respiratory disease severity ranging from mild to severe in three COVID-19 hamster models. The non-invasive, serial measure of disease progression provided by PET/CT makes it a valuable tool for animal model characterization.

Preclinical studies of antiviral activity of the RPH-137 fusion protein and molnupiravir against COVID-19.

Finding effective and safe medicines to fight SARS-CoV-2 infection is an urgent task. RPH-137 is an original trap fusion protein against SARS-CoV-2 virus. It comprises the angiotensin-converting enzyme type 2 extracellular domain and the human IgG1 Fc fragment. The aim of the study was to carry out a preclinical evaluation of the efficacy of RPH-137 and molnupiravir against SARS-CoV-2 infection. Material(s) and Method(s): the authors analysed RPH-137 expressed in a stable CHO cell line and molnupiravir used as an active pharmaceutical ingredient. Drug-mediated inhibition of virus-induced cytotoxicity was assessed in Vero cell culture. In vivo efficacy assessments were performed in Syrian hamsters. The animals were infected intranasally with SARS-CoV-2 (PIK35 clinical isolate) in the dose of 5 log TCID50. The authors evaluated body weight measurements, lung-body weight ratios, and lung histopathology findings and determined viral RNA levels in oropharyngeal swabs by RT-PCR using the amplification cycle threshold (Ct). The statistical analyses involved one- and two-way ANOVA, Student's t-test, and Mann-Whitney test. Result(s): RPH-137 and molnupiravir inhibited the cytopathic effect of SARS-CoV-2 in Vero cells;the EC50 values of RPH-137 amounted to 4.69 mug/mL (21.3 nM) and 16.24 mug/mL (73.8 nM) for 50 TCID50 and 200 TCID50, respectively, whereas the EC50 values of molnupiravir were 0.63 mug/mL (1900 nM) for both doses. Intramuscular RPH-137 (30 and 80 mg/kg) had no effect on the infection process in Syrian hamsters. The comparison with the challenge control group showed that intraperitoneal RPH-137 (100 mg/kg) had statistically significant effects on a number of parameters, including a 27% reduction in inflammation and a 30% reduction in the total lesion area of the lungs by Day 7. Intragastric molnupiravir (300 mg/kg twice daily) significantly inhibited SARS-CoV-2 infection. Conclusion(s): both RPH-137 and molnupiravir inhibited the cytopathic effect of SARS-CoV-2 in Vero cells. In Syrian hamsters, molnupiravir demonstrated a more pronounced inhibition of SARS-CoV-2 than RPH-137. However, RPH-137 had statistically significant effects on a range of parameters. This offers additional perspectives for further research.Copyright © 2023 Safety and Risk of Pharmacotherapy. All rights reserved.

Pathology of animal models of COVID-19

This paper describes the pathogenesis and immunology of Macaca mulatta, Macaca fascicularis, ferrets, Syrian golden hamsters (Mesocricetus auratus), mice, cats, mink, pigs and rabbits used as models for SARS-CoV-2 infection.

[Comparative study of Wuhan-like and omicron-like variants of SARS-CoV-2 in experimental animal models].

INTRODUCTION: The variability of SARS-CoV-2 appeared to be higher than expected, the emergence of new variants raises concerns. The aim of the work was to compare the pathogenicity of the Wuhan and BA.1.1/Omicron variants in BALB/c mice and Syrian hamsters. MATERIALS AND METHODS: The study used strains of SARS-CoV-2: Dubrovka phylogenetically close to Wuhan-Hu-1, and LIA phylogenetically close to Omicron, BALB/c mice, transgenic mice B6.Cg-Tg(K18-ACE2)2Prlmn/HEMI Hemizygous for Tg(K18-ACE2)2Prlmn, Syrian golden hamsters. Animals were infected intranasally, pathogenicity was estimated by a complex of clinical, pathomorphological and virological methods. RESULTS: Comparative studies of SARS-CoV-2 Dubrovka and LIA strains on animal models demonstrated their heterogeneous pathogenicity. In parallel infection of BALB/c mice with Dubrovka and LIA variants, the infection proceeded without serious clinical signs and lung damage. Infection with the LIA strain resulted to a systemic disease with a high concentration of viral RNA in the lungs and brain tissues of animals. The presence of viral RNA in mice infected with the Dubrovka strain was transient and undetectable in the lungs by day 7 post-infection. Unlike the mouse model, in hamsters, the Dubrovka strain had a greater pathogenicity than the LIA strain. In hamsters infected with the Dubrovka strain lung lesions were more significant, and the virus spread through organs, in particular in brain tissue, was observed. In hamsters infected with the LIA strain virus was not detected in brain tissue. CONCLUSION: The study of various variants of SARS-CoV-2 in species initially unsusceptible to SARS-CoV-2 infection is important for monitoring zoonotic reservoirs that increase the risk of spread of new variants in humans.

Severe Acute Respiratory Syndrome Coronavirus-2 Delta Variant Study In Vitro and Vivo.

At the end of 2019, an outbreak of a new severe acute respiratory syndrome caused by a coronavirus occurred in Wuhan, China, after which the virus spread around the world. Here, we have described the adaptive capacity and pathogenesis of the SARS-CoV-2 Delta variant, which is widespread in Armenia, in vitro and vivo on Syrian hamsters. We have studied the changes in the SARS-CoV-2genome using viral RNA sequencing during virus adaptation in vitro and in vivo. Our findings revealed that SARS-CoV-2 in Syrian hamsters causes a short-term pulmonary form of the disease, the first symptoms appear within 48 h after infection, reach 5-7 days after infection, and begin to disappear by 7-9 days after infection. The virus induces pathogenesis in the blood and bone marrow, which generally corresponds to the manifestation of the inflammatory process. The pulmonary form of the disease passes faster than changes in blood cells and bone marrow. Our data show that hamster organs do not undergo significant pathological changes in the Delta variant of SARS-CoV-2 infection.

Intranasal delivery of a chimpanzee adenovirus vector expressing a pre-fusion spike (BV-AdCoV-1) protects golden Syrian hamsters against SARS-CoV-2 infection.

We evaluated the immunogenicity and protective ability of a chimpanzee replication-deficient adenovirus vectored COVID-19 vaccine (BV-AdCoV-1) expressing a stabilized pre-fusion SARS-CoV-2 spike glycoprotein in golden Syrian hamsters. Intranasal administration of BV-AdCoV-1 elicited strong humoral and cellular immunity in the animals. Furthermore, vaccination prevented weight loss, reduced SARS-CoV-2 infectious virus titers in the lungs as well as lung pathology and provided protection against SARS-CoV-2 live challenge. In addition, there was no vaccine-induced enhanced disease nor immunopathological exacerbation in BV-AdCoV-1-vaccinated animals. Furthermore, the vaccine induced cross-neutralizing antibody responses against the ancestral strain and the B.1.617.2, Omicron(BA.1), Omicron(BA.2.75) and Omicron(BA.4/5) variants of concern. These results demonstrate that BV-AdCoV-1 is potentially a promising candidate vaccine to prevent SARS-CoV-2 infection, and to curtail pandemic spread in humans.

Increased pathogenicity and aerosol transmission for one SARS-CoV-2 B.1.617.2 Delta variant over the wild-type strain in hamsters.

During the two-year pandemic of coronavirus disease 2019 (COVID-19), its causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been evolving. SARS-CoV-2 Delta, a variant of concern, has become the dominant circulating strain worldwide within just a few months. Here, we performed a comprehensive analysis of a new B.1.617.2 Delta strain (Delta630) compared with the early WIV04 strain (WIV04) in vitro and in vivo, in terms of replication, infectivity, pathogenicity, and transmission in hamsters. When inoculated intranasally, Delta630 led to more pronounced weight loss and more severe disease in hamsters. Moreover, 40% mortality occurred about one week after infection with 104 PFU of Delta630, whereas no deaths occurred even after infection with 105 PFU of WIV04 or other strains belonging to the Delta variant. Moreover, Delta630 outgrew over WIV04 in the competitive aerosol transmission experiment. Taken together, the Delta630 strain showed increased replication ability, pathogenicity, and transmissibility over WIV04 in hamsters. To our knowledge, this is the first SARS-CoV-2 strain that causes death in a hamster model, which could be an asset for the efficacy evaluation of vaccines and antivirals against infections of SARS-CoV-2 Delta strains. The underlying molecular mechanisms of increased virulence and transmission await further analysis.

Analysis of intermediate hosts and susceptible animals of SARS-CoV-2 by computational methods

COVID-19, a disease caused by SARS-CoV-2 that produces major symptoms of pneumonia, has been a disaster worldwide. The traceability of SARSCoV- 2 and the discovery of susceptible animal species is crucial to halt viral transmission and explore the mechanism of cross-species transmission. We selected 82 representative ACE2 sequences from the 1000 sequences with the closest homology to the hACE2 protein. All selected ACE2 proteins were subjected to homology modeling. Potential natural and intermediate hosts, as well as animal species susceptible to SARS-CoV-2, were analyzed systematically by calculation of the binding free energy of ACE2 protein to the RBD of SARSCoV- 2. Primates, some wild Felidae, civets, goats, spotted hyenas and golden hamsters are susceptible to SARS-CoV-2 and may be potential intermediate hosts, whereas pangolins, birds and reptiles are unlikely to be intermediate hosts. Mice, rats and guinea pig are not susceptible to SARS-CoV-2. Given their possible susceptibility, non-human primates, goats and golden hamsters could potentially be used as experimental models to examine SARS-CoV-2 infection without transgenesis. Herein, possible candidates for the natural and intermediate hosts of SARS-CoV-2 are suggested, to provide guidance for subsequent studies.

SARS-CoV-2 Virus Culture, Genomic and Subgenomic RNA Load, and Rapid Antigen Test in Experimentally Infected Syrian Hamsters.

The duration of SARS-CoV-2 genomic RNA shedding is much longer than that of infectious SARS-CoV-2 in most COVID-19 patients. It is very important to determine the relationship between test results and infectivity for efficient isolation, contact tracing, and post-isolation. We characterized the duration of viable SARS-CoV-2, viral genomic and subgenomic RNA (gRNA and sgRNA), and rapid antigen test positivity in nasal washes, oropharyngeal swabs, and feces of experimentally infected Syrian hamsters. The duration of viral genomic RNA shedding is longer than that of viral subgenomic RNA, and far longer than those of rapid antigen test (RAgT) and viral culture positivity. The rapid antigen test results were strongly correlated with the viral culture results. The trend of subgenomic RNA is similar to that of genomic RNA, and furthermore, the subgenomic RNA load is highly correlated with the genomic RNA load. IMPORTANCE Our findings highlight the high correlation between rapid antigen test and virus culture results. The rapid antigen test would be an important supplement to real-time reverse transcription-RCR (RT-PCR) in early COVID-19 screening and in shortening the isolation period of COVID-19 patients. Because the subgenomic RNA load can be predicted from the genomic RNA load, measuring sgRNA does not add more benefit to determining infectivity than a threshold determined for gRNA based on viral culture.

New evidence for aerosol transmission of SARS-CoV-2

Since the outbreak of COVID-19, the opinion that the aerosol plays a key role in the transmission of SARS-CoV-2 has been controversial. The COVID-19 pandemic has continued interpersonal transmission for more than two years, especially after the emergence of Delta and Omicron variants, making the situation of COVID-19 pandemic more severe. The transmission of SARS-COV-2 variants was significantly accelerated and the time of transmission between generations was significantly shortened. Therefore, it has been questioned to attribute the close-range infection to droplet transmission. The point that the aerosol can also has a close-range transmission and may play a dominant role is neglected under the influence of traditional transmission mode of respiratory infectious diseases. A large number of studies have shown that normal breath, talk and cough could release a large number of respiratory aerosol particles, and the virus particles were mainly tiny particles(=5.0 micro m). The biological activity and infectivity of the droplet nuclei have been questioned in the studies on their physicochemical properties. Animal models of ferrets and hamsters showed that SARS-COV-2 could transmit via aerosol. Therefore, the new evidence for the aerosol transmission of SARS-COV-2 was reviewed in the article so as to provide latest evidence-based evidence for prevention and control of COVID-19.

Pathogenicity of SARS-CoV-2 Omicron (R346K) variant in Syrian hamsters and its cross-neutralization with different variants of concern.

BACKGROUND: SARS-CoV-2 Omicron variant is rampantly spreading across the globe. We assessed the pathogenicity and immune response generated by BA.1.1 sub-lineage of SARS-CoV-2 [Omicron (R346K) variant] in 5 to 6-week old Syrian hamsters and compared the observations with that of Delta variant infection. METHODS: Virus shedding, organ viral load, lung disease and immune response generated in hamsters were sequentially assessed. FINDINGS: The disease characteristics of the Omicron (R346K) variant were found to be similar to that of the Delta variant infection in hamsters like viral replication in the respiratory tract and interstitial pneumonia. The Omicron (R346K) infected hamsters demonstrated lesser body weight reduction and viral RNA load in the throat swab and nasal wash samples in comparison to the Delta variant infection. The viral load in the lungs and nasal turbinate samples and the lung disease severity of the Omicron (R346K) infected hamsters were found comparable with that of the Delta variant infected hamsters. Neutralizing antibody response against Omicron (R346K) variant was detected from day 5 and the cross-neutralization titre of the sera against other variants showed severe reduction ie., 7 fold reduction against Alpha and no titers against B.1, Beta and Delta. INTERPRETATION: This preliminary data shows that Omicron (R346K) variant infection can produce moderate to severe lung disease similar to that of the Delta variant and the neutralizing antibodies produced in response to Omicron (R346K) variant infection shows poor neutralizing ability against other co-circulating SARS-CoV-2 variants like Delta which necessitates caution as it may lead to increased cases of reinfection. FUNDING: This study was supported by Indian Council of Medical Research as an intramural grant (COVID-19) to ICMR-National Institute of Virology, Pune.

Nasal Mucosa Exploited by SARS-CoV-2 for Replicating and Shedding during Reinfection.

Reinfection risk is a great concern with regard to the COVID-19 pandemic because a large proportion of the population has recovered from an initial infection, and previous reports found that primary exposure to SARS-CoV-2 protects against reinfection in rhesus macaques without viral presence and pathological injury; however, a high possibility for reinfection at the current stage of the pandemic has been proven. We found the reinfection of SARS-CoV-2 in Syrian hamsters with continuous viral shedding in the upper respiratory tracts and few injuries in the lung, and nasal mucosa was exploited by SARS-CoV-2 for replication and shedding during reinfection; meanwhile, no viral replication or enhanced damage was observed in the lower respiratory tracts. Consistent with the mild phenotype in the reinfection, increases in mRNA levels in cytokines and chemokines in the nasal mucosa but only slight increases in the lung were found. Notably, the high levels of neutralizing antibodies in serum could not prevent reinfection in hamsters but may play roles in benefitting the lung recovery and symptom relief of COVID-19. In summary, Syrian hamsters could be reinfected by SARS-CoV-2 with mild symptoms but with obvious viral shedding and replication, and both convalescent and vaccinated patients should be wary of the transmission and reinfection of SARS-CoV-2.

Development of a T Cell-Based COVID-19 Vaccine Using a Live Attenuated Influenza Vaccine Viral Vector.

The COVID-19 pandemic emerged in 2020 and has caused an unprecedented burden to all countries in the world. SARS-CoV-2 continues to circulate and antigenically evolve, enabling multiple reinfections. To address the issue of the virus antigenic variability, T cell-based vaccines are being developed, which are directed to more conserved viral epitopes. We used live attenuated influenza vaccine (LAIV) virus vector to generate recombinant influenza viruses expressing various T-cell epitopes of SARS-CoV-2 from either neuraminidase (NA) or non-structural (NS1) genes, via the P2A self-cleavage site. Intranasal immunization of human leukocyte antigen-A*0201 (HLA-A2.1) transgenic mice with these recombinant viruses did not result in significant SARS-CoV-2-specific T-cell responses, due to the immunodominance of NP366 influenza T-cell epitope. However, side-by-side stimulation of peripheral blood mononuclear cells (PBMCs) of COVID-19 convalescents with recombinant viruses and LAIV vector demonstrated activation of memory T cells in samples stimulated with LAIV/SARS-CoV-2, but not LAIV alone. Hamsters immunized with a selected LAIV/SARS-CoV-2 prototype were protected against challenge with influenza virus and a high dose of SARS-CoV-2 of Wuhan and Delta lineages, which was confirmed by reduced weight loss, milder clinical symptoms and less pronounced histopathological signs of SARS-CoV-2 infection in the lungs, compared to LAIV- and mock-immunized animals. Overall, LAIV is a promising platform for the development of a bivalent vaccine against influenza and SARS-CoV-2.

Alteration of the gut microbiota's composition and metabolic output correlates with COVID-19-like severity in obese NASH hamsters.

Obese patientss with nonalcoholic steatohepatitis (NASH) are particularly prone to developing severe forms of coronavirus disease 19 (COVID-19). The gut-to-lung axis is critical during viral infections of the respiratory tract, and a change in the gut microbiota's composition might have a critical role in disease severity. Here, we investigated the consequences of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the gut microbiota in the context of obesity and NASH. To this end, we set up a nutritional model of obesity with dyslipidemia and NASH in the golden hamster, a relevant preclinical model of COVID-19. Relative to lean non-NASH controls, obese NASH hamsters develop severe inflammation of the lungs and liver. 16S rRNA gene profiling showed that depending on the diet, SARS-CoV-2 infection induced various changes in the gut microbiota's composition. Changes were more prominent and transient at day 4 post-infection in lean animals, alterations still persisted at day 10 in obese NASH animals. A targeted, quantitative metabolomic analysis revealed changes in the gut microbiota's metabolic output, some of which were diet-specific and regulated over time. Our results showed that specifically diet-associated taxa are correlated with disease parameters. Correlations between infection variables and diet-associated taxa highlighted a number of potentially protective or harmful bacteria in SARS-CoV-2-infected hamsters. In particular, some taxa in obese NASH hamsters (e.g. Blautia and Peptococcus) were associated with pro-inflammatory parameters in both the lungs and the liver. These taxon profiles and their association with specific disease markers suggest that microbial patterns might influence COVID-19 outcomes.

Probable Animal-to-Human Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Delta Variant AY.127 Causing a Pet Shop-Related Coronavirus Disease 2019 (COVID-19) Outbreak in Hong Kong.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect human and other mammals, including hamsters. Syrian (Mesocricetus auratus) and dwarf (Phodopus sp.) hamsters are susceptible to SARS-CoV-2 infection in the laboratory setting. However, pet shop-related Coronavirus Disease 2019 (COVID-19) outbreaks have not been reported. METHODS: We conducted an investigation of a pet shop-related COVID-19 outbreak due to Delta variant AY.127 involving at least 3 patients in Hong Kong. We tested samples collected from the patients, environment, and hamsters linked to this outbreak and performed whole genome sequencing analysis of the reverse transcription polymerase chain reaction (RT-PCR)-positive samples. RESULTS: The patients included a pet shop keeper (Patient 1), a female customer of the pet shop (Patient 2), and the husband of Patient 2 (Patient 3). Investigation showed that 17.2% (5/29) and 25.5% (13/51) environmental specimens collected from the pet shop and its related warehouse, respectively, tested positive for SARS-CoV-2 RNA by RT-PCR. Among euthanized hamsters randomly collected from the storehouse, 3% (3/100) tested positive for SARS-CoV-2 RNA by RT-PCR and seropositive for anti-SARS-CoV-2 antibody by enzyme immunoassay. Whole genome analysis showed that although all genomes from the outbreak belonged to the Delta variant AY.127, there were at least 3 nucleotide differences among the genomes from different patients and the hamster cages. Genomic analysis suggests that multiple strains have emerged within the hamster population, and these different strains have likely transmitted to human either via direct contact or via the environment. CONCLUSIONS: Our study demonstrated probable hamster-to-human transmission of SARS-CoV-2. As pet trading is common around the world, this can represent a route of international spread of this pandemic virus.

Susceptibility of cell lines from different animal species to Porcine Deltacoronavirus

[Objective] To explore whether porcine deltacoronavirus (PDCoV) can infect and proliferate in different animal species-derived cell lines. [Methods] The Sichuan isolate CHN-SC2015of PDCoV was inoculated in twelve cell lines derived from hamster,poultry,monkey, human and swine. After at least five blindly passages in each cell line, the virus was identified by RT-PCR,RT-q PCR, indirect immunofluorescence assay (IFA), and sequencing. [Results] PDCoV caused distinct cytopathic effect (CPE) in Vero,PAM,PK15,ST, and LLC-PK1 cells at the 1st passage (P1) and proliferated to various degrees in PAM,PK15,ST, and LLC-PK1 cells, while the CPE gradually disappeared during subsequent passages in Vero and PAM cells. Except that in the three susceptible cell lines (PK15,LLC-PK1, and ST), the viral copies of the infected cell lines gradually decreased with the increase in passages, and PDCoV could not be detected at P4 or P5 of DEF,Marc-145,HEK-293,ZYM-SIEC02, and PAM cells. PCR results showed that PDCoV could be detected only in CEF and Vero cells at P5. The IFA results showed that PDCoV could infect other cell lines except BHK-21 and ZYM-SIEC02, and specific immunofluorescence was observed in PK15,LLC-PK1, and ST cells at P1,P3, and P9. Therefore, only three cell lines (PK15,LLC-PK1, and ST) were suitable for serial passage, with the virus titers up to 107.11,107.00, and 107.37 TCID50/mL at P9,respectively. After passage in different cell lines,CHN-SC2015 accumulated 14 nucleotide mutations corresponding to 12 amino acid mutations. [Conclusion] This study indicates that PDCoV can infect a variety of cells in vitro, suggesting that it may have the potential of cross-species transmission.

Animal role in the COVID-19 pandemic

The first cases of human disease from COVID-19 were recorded in December 2019 in China, from where it spread rapidly around the world. COVID-19, the third emerging coronavirus infection in humans, is caused by the new SARS-CoV-2 virus, which can cause a severe acute respiratory syndrome in some infected individuals. Previous research has revealed the possible animal origin of SARS-CoV-2, with bats considered as natural reservoirs and pangolins as intermediate hosts. To better understand COVID-19 and more successfully control the spread, domestic and wild animals have been infected in experimental conditions. On the other hand, in some species, infections have been recorded in field conditions. Natural infections have been reported in dogs, cats, tigers, lions, and minks, who have been in contact with SARS-CoV-2 positive humans. The reverse transmission of the pathogen, from infected animals to humans, has only been recorded on intensive mink farms. To better understand the pathogenesis of this disease's causative agent, drugs and vaccine trials, some experimental infections were performed on animal models, of which ferrets, rhesus macaques, and hamsters proved to be the most suitable. This article aimed to consolidate known data on the potential origin of SARS-CoV-2, its transmission to humans, infections in animals, and their significance in the epidemiology of COVID-19.