Natural Transmission and Experimental Models of SARS-CoV-2 Infection in Animals

Since the World Health Organization declared COVID-19 a pandemic in March 2020, millions of people have contracted SARS-CoV-2 and died from the infection. Several domestic and wild species have contracted the disease as well. From the beginning, scientists have been working to develop vaccines and establish therapies that can prevent disease development and improve the clinical outcome in infected people. To understand various aspects of viral pathogenesis and infection dynamics and to support preclinical evaluation of vaccines and therapeutics, a diverse number of animal species have been evaluated for use as models of the disease and infection in humans. Here, we discuss natural SARS-CoV-2 infection of domestic and captive wild animals, as well as the susceptibility of several species to experimental infection with this virus.

In December 2019, several health facilities in China reported cases of patients with pneumonia of unknown cause. Epidemiologic studies linked the majority of the affected patients with a seafood and wet-animal wholesale market in Wuhan, China.⁹⁴ The patients presented with fever, cough, and chest discomfort; 2 of the first 3 patients recovered, whereas the remaining one died. RNA extracted from the bronchoalveolar-lavage fluid of one patient was sequenced, and a viral sequence that had 85% identity with a SARS-related coronavirus isolated from a bat was identified. The same specimen was used for viral isolation, and the isolate was originally named 2019-nCoV. Genomic and phylogenetic analysis revealed similarities of the newly identified virus with bat coronaviruses and differences from severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV). The newly isolated virus belongs to a clade within the subgenus Sarbecovirus and differs from SARS-CoV and other SARS-related virus strains. Because the sequence identity in the 1ab open reading frame (conserved replicase domain) was less than 90% between 2019-nCoV and other betacoronaviruses, the virus was classified as a novel betacoronavirus, subgenus Sarbecovirus, family Coronaviridae.⁸⁴ The virus has since been officially renamed by the International Committee on Taxonomy of Viruses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with the disease caused by SARS-CoV-2 called COVID-19.¹⁷ As of 13 September 2021, more than 330 million cases of COVID-19 have occurred, and the disease has claimed more than 4.6 million human lives worldwide.⁸⁶SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as the cellular receptor for virus binding.³⁴ The interaction between the virus spike protein and the host-cell ACE2 protein is mediated by the receptor binding domain (RBD) present in the spike protein. The RBD of the spike protein is highly variable among coronaviruses, and is under constant selection pressure. The affinity of the RBD of the spike protein with the cellular receptor determines the host range of coronaviruses.²⁵ Unlike the spike protein of SARS-CoV, the spike protein of SARS-CoV-2 is preactivated by the proprotein convertase furin prior to cell entry; the cell-surface protease transmembrane serine protease 2 and lysosomal cathepsin protease also participate in cell entry. The SARS-CoV-2 RBD binds to human ACE2 (hACE2) with higher affinity than does SARS-CoV. In contrast, the spike protein as a whole has lower affinity for hACE2, suggesting that the SARS-CoV-2 RBD provides a way to evade the immune system while still allowing efficient cell entry.^66,67The current coronavirus outbreak represents the third transmission of coronaviruses from animals to humans in the last 2 decades. In 2002, an outbreak of SARS-CoV in China caused 916 deaths (case fatality rate of 11%).^12,21 In 2012, another related coronavirus, Middle East Respiratory Syndrome coronavirus (MERS-CoV), emerged in Middle Eastern countries, with a mortality rate of 34%.^86,88 Several studies on the evolution of these viruses^18,25,26 and more recently on SARS-CoV-2¹ point to bats as the origin of infection for all 3 viruses.As for SARS-CoV and MERS-CoV, SARS-CoV-2 likely moved from bat reservoirs to a yet-unknown intermediate host and then to humans.^1,92 Masked civet cats and dromedary camels have been identified as the intermediate host for SARS-CoV and MERS-CoV, respectively.^73,89 Notably, several animal species seem to be naturally susceptible to SARS-CoV-2 infection, mainly due to the highly conserved nature of the ACE2 protein among diverse animal species, especially mammals. Pangolins,⁴⁴ dogs⁵⁸ and snakes⁴⁶ were under investigation as potential intermediate hosts for SARS-CoV-2. However, the animal species that enabled transmission to humans has yet to be determined. Natural infections have been reported in dogs, domestic cats, wild felids, gorillas, minks, ferrets, and white-tailed deer.^{3,14,22,28,50,54,55,72} (One source, Chandler JC and colleagues has not been peer reviewed). Several studies have been conducted to establish animal models for SARS-CoV-2 infection, including hACE2 mice, hamsters, NHP, cats, and ferrets.In this review, we discuss the natural occurrence of SARS-CoV-2 in animals and available animal models of SARS-CoV-2 infection and pathogenesis.     

Deregulated Expression of SRC,LYN and CKB Kinases by DNA Methylation and Its Potential Role in Gastric Cancer Invasiveness and Metastasis

Kinases are downstream modulators and effectors of several cellular signaling cascades and play key roles in the development of neoplastic disease. In this study, we aimed to evaluate SRC, LYN and CKB protein and mRNA expression, as well as their promoter methylation, in gastric cancer. We found elevated expression of SRC and LYN kinase mRNA and protein but decreased levels of CKB kinase, alterations that may have a role in the invasiveness and metastasis of gastric tumors. Expression of the three studied kinases was also associated with MYC oncogene expression, a possible biomarker for gastric cancer. To understand the mechanisms that regulate the expression of these genes, we evaluated the DNA promoter methylation of the three kinases. We found that reduced SRC and LYN methylation and increased CKB methylation was associated with gastric cancer. The reduced SRC and LYN methylation was associated with increased levels of mRNA and protein expression, suggesting that DNA methylation is involved in regulating the expression of these kinases. Conversely, reduced CKB methylation was observed in samples with reduced mRNA and protein expression, suggesting CKB expression was found to be only partly regulated by DNA methylation. Additionally, we found that alterations in the DNA methylation pattern of the three studied kinases were also associated with the gastric cancer onset, advanced gastric cancer, deeper tumor invasion and the presence of metastasis. Therefore, SRC, LYN and CKB expression or DNA methylation could be useful markers for predicting tumor progression and targeting in anti-cancer strategies.     

Plastome sequences of the subgenus Passiflora reveal highly divergent genes and specific evolutionary features

Plant Molecular Biology - Phylogenetic aspects, hotspots of nucleotide divergence, highly divergent genes, and specific RNA editing sites have been identified and characterized in the plastomes of...     

Synthesis, cytotoxicity, and DNA-topoisomerase inhibitory activity of new asymmetric ureas and thioureas

A new series of N-3,3-diphenylpropyl-N-(p-X-benzyl)-N'-phenylureas (5a-g) and thioureas (6a-g) were synthesized by the reaction of secondary amines and phenyl isocyanate or isothiocyanate. The cytotoxic effects of the urea and thiourea derivatives were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay against Ehrlich carcinoma and K562 human leukemia cells. Moreover, the activity of compounds in the inhibition of DNA topoisomerases I and II-alpha was tested. The results indicated that the compounds presented important and promising antiproliferative action.     

High resolution localization of cruzipain and Ssp4 in Trypanosoma cruzi by replica staining label fracture

Summary— The replica staining label fracture technique was used to analyse the distribution of cruzipain and Ssp4 in Trypanosoma cruzi. Intense labeling for the two proteins was seen on the E fracture face of amastigote forms. Gold particles did not co-localize with the intramembranous particles. Labeling was abolished by previous treatment of the parasites with phospholipase C from Trypanosoma brucei, which removes glycosylphosphatidyl inositol (GPI) anchored proteins. These observations suggest that cruzipain and Ssp4 are attached to the parasite surface via a GPI anchor.     

Impact of game hunting by the Kayapó of south-eastern Amazonia: implications for wildlife conservation in tropical forest indigenous reserves

Indigenous forest reserves represent approximately one fifth of Brazilian Amazonia and pose enormous challenges for sustainable natural resource management by native Amazonians. In collaboration with the Kayapó Indians of A’Ukre of southeastern Amazonia, we obtained a game harvest profile of over 1360 forest vertebrates consumed at this village over a 20-month period, including 743 mammals, 361 forest tortoises and 256 birds from a minimum of 42 game species. This amounted to a total of 13,775 kg of game animals harvested over the entire study (mean = 26.2 kg d⁻¹). We also obtained some 450 km of line transect census data of midsized to large-bodied vertebrates within the core hunting catchment of this village and in an unhunted but otherwise comparable site upriver of A’Ukre. Population density estimates of 16 of the 18 species censused were significantly depressed by hunting by central place foragers within the village catchment, and a number of harvest-sensitive prey species showed clear evidence of local depletion. For the time being, however, we can conclude that hunting was sustainable at the landscape scale largely because source-sink dynamics in the context of low village catchment density is made possible by large surrounding tracts of primary forest that remain unharvested or underharvested.     

Studies on rat liver mitochondria. 6. The effect of contaminating particles in mitochondria stored at 0-4 degrees C

Rat liver mitochondria were stored at 0-4 degrees C for several days using an appropriate medium and energy source. The elimination of the majority of microsomes and lysosomes, that normally contaminate isolated mitochondria, had a positive effect in preservation of respiratory control, P:O ratio, and monoamine oxidase activity during long term storage.     

Effect of monosodium glutamate treatment during neonatal development on lipogenesis rate and lipoprotein lipase activity in adult rats.

Monosodium glutamate (MSG) has been shown to alter several neuroendocrine functions in neonatally treated rats. To evaluate possible alterations in lipogenesis rate and lipoprotein lipase (LPL) activity, male and female rats were injected during the neonatal period with MSG or saline (controls). In male MSG rats, an increase in lipogenesis of liver and retroperitoneal adipose tissues was observed. Triton WR 1339 (an LPL inhibitor) administration decreased retroperitoneal lipogenesis in these animals. In female rats, MSG-treatment increased lipogenesis only in gonadal and retroperitoneal adipose tissues. No change was observed in hepatic lipogenesis and the Triton administration did not change retroperitoneal lipogenesis. LPL activity was increased in the gonadal and retroperitoneal adipose tissues in male and female MSG-treated rats. These data suggest that there is a specific sex-dependent response in the development of MSG-induced obesity.