Whole genome sequence analysis shows that SARS-CoV-2 is highly homologous to SARS-related coronaviruses identified in Chinese chrysanthemum manta rays. There is a limitation in studying bat coronaviruses: the lack of laboratory models that can be used to study bat viruses. The hku-Hkta team has created the world’s first bat intestinal organ to fill the gap, according to new research. The study found that these bat intestinal organs are completely susceptible to SARS-CoV-2 and maintain a strong ability to replicate the virus.
In the lab, the researchers created a small, simple version of the intestinal organ, which originated from rhinolophus sinicus, which summarizes the bat’s intestinal epithelial. The study provides evidence that SARS-CoV-2 can infect bat intestinal cells. The study further demonstrates that SARS-CoV-2 can replicate actively in human intestinal organs, while isolating infectious new coronaviruses from the feces of new coronary patients with diarrhea. The human gut may be a route of transmission of SARS-CoV-2.
On 13 May local time, Nature-Medicine published a study from the University of Hong Kong: Infection of the bat and humanal organoids by SARS-CoV-2, demonstrating this progress. The study’s correspondent was Zhou Wei, Department of Microbiology, Li Ka-shing School of Medicine, University of Hong Kong.
The study of intestinal susceptibility to neo-coronaviruses is that some COVID-19 patients with gastrointestinal symptoms and viral RNA tests in fecal samples have shown that SARS-CoV-2 may also infect the intestines in addition to the respiratory tract.
Common symptoms of COVID-19 include fever, cough, shortness of breath, muscle aches and fatigue. Some patients have gastrointestinal symptoms such as nausea, vomiting and diarrhea. Viral RNA was detected in the patient’s respiratory tract and fecal specimens. Genome-wide sequence analysis showed that SARS-CoV-2 virus clusters with severe respiratory syndrome-related coronaviruses (SARSr-CoVs) were found in bats, 96% of the homologous nature of SARS-CoV-CoV13 with bat coronavirus BatCoV RaTG13, and 88% sarSr-CoVin of the other bats (Bat-SL-CoVZ45 and Bat-CoVZ45 and Bat-CoV-CoV45 and Bat-CoV-CoV-CoV-CoV-CoV-CoV-CoV45 and Bat-CoV-CoV45 and Bat-CoV-CoV45 and Bat-CoV-CoV-CoV-CoV45 and Bat-CoV-CoV-CoV-CoV45 and Bat-CoV-CoV-CoV-CoV45 and Bat-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-CoV-Co-C-Co-C-Co-C45 and Bat-CoV-CoV-CoV-CoV-CoV-CoV45 and Bat This suggests that SARS-CoV-2 may have originated in bats.
Bats are natural “water reservoirs” for viruses, especially RNA viruses, which can cause serious zoonotic diseases. SARS-CoV caused the SARS outbreak in 2003, and scientists began a extensive search for the ancestors of the SARS-CoV virus, eventually finding a large number of related coronaviruses in fecal specimens or swabs of Chinese chrysanthemum bats. However, these findings often depend on the use of molecular methods to detect viral genomes or genomic fragments. To date, most identified bats have not been successfully isolated and cultured, with the exception of three viruses isolated from the defective Vero E6 or Vero cells and one genetic synthesis virus. The use of bat cell lines to isolate SARSr-CoV is not currently documented.
Chinese chrysanthemum manta rays are considered to be the natural host of SARS-CoV. However, there is no direct evidence of severe respiratory syndrome-related coronavirus (SARSr-CoV) infection in these bats, either because of the acute and self-limiting nature of the epidemic, or because of the seasonal fluctuations of these viruses and difficulties in accessing these animals in the wild. Therefore, the absence of readily available in vitro models that truthfully represent natural bat cells is currently a major obstacle for the scientific community to isolate and study bat viruses, including bat SARSr-CoV, which have high zoonotic disease potential.
In the past decade, manhasion has made a major breakthrough in the establishment of organ-like organs. Stem cell-based (ASC)-based organ culture systems have been able to build most human organs, including human intestinal and lung organs. Induced intestinal organs can faithfully simulate the multicellular composition and functional complexity of the upper skin of the human intestine. Because the human gastrointestinal tract is one of the most common ways of microbial invasion, human intestinal organs have become an important in vitro tool to simulate intestinal infections. For the study, the researchers attempted to build a stem cell-based organ culture of the epithelial skin of bats. Researchers believe bat organs may help experimentally detect potential sources of new coronaviruses. In addition, the researchers investigated the possibility of SARS-CoV-2 passing through the human gut.
Taking into account the high homologous nature of SARS-CoV-2 and bat SARSr-CoV, as well as the discovery of SARSr-CoV in fecal specimens of chrysanthemum bats, the researchers attempted to use the faint nest speuled from the intestines of chrysanthemum bats, as shown in the following image:
Used to build intestinal organ cultures.
The researchers successfully built small intestine organs in bats using an experimental process to build human intestinal organs. Undifferentiated bat intestinal solutes reproduce in the medium, and in order to induce differentiation, the researchers replaced the dilated medium with a differentiated medium in which the organ was incubated for 4 days. Differentiated bat intestinal samples mimic the multicellular composition of the natural bat small intestine epithelial, as shown in the following image:
Using a transmissive electron microscope, the researchers identified cells with four main intestinal cell type characteristics in differentiated bat intestinal samples, including intestinal epithelial cells (E), cup cells (G), pan cells (P) and intestinal endocrine cells (EE), as shown in the following image:
Although one bat small intestine organ has been amplified for 12 weeks, the other four bat small intestine organs cease to proliferate after 4 or 5 weeks, and it can be considered that the human intestinal organs can be continuously expanded for at least one year. Still, the researchers created the first bat intestinal organ to simulate the formation of bat intestinal cells.
The authors then assessed whether the organs were susceptible to SARS-CoV-2 and found that they maintained viral replication.
It is worth noting that over time, viral loads have been observed in the medium of bats and human intestines, as shown in the following figure:
The cultured mediums collected by the researchers from infected bat organs were then inoculated into human organs, rather than in bat organs, because the researchers intended to inoculate fresh cultures into the earliest available organ stodgies to maximize the isolation of the virus. After inoculating the media from the first round of isolation, it was observed that the viral load in the medium had increased significantly, to more than 3 log units, as shown in the following figure:
Immunofluorescent staining verified the presence of viral nucleoid protein (NP)-positive cells in human small intestine organs:
This suggests that SARS-CoV-2 can infect bat intestinal cells, thus reproducing natural infections in the bat intestine.
Zhou and others also investigated whether human intestinal organs are susceptible to SARS-CoV-2, and the results were also observed in the intestines of the virus replication. The researchers also tried to isolate the virus from stool samples from patients with coVID-19 diarrhea. A 68-year-old female patient developed fever, sore throat and cough and diarrhea after being admitted to Princess Margaret Hospital in Hong Kong. Her faeces sample sofe sample sat positive for SARS-CoV-2 and a Ct value of 33.6. The study isolated the infectious virus from her fecal specimens. The isolated infectious virus from the patient’s faeces indicates the outbreak of SARS-CoV-2 intestinal infection.
The authors say the exact route of intestinal infections in humans is unclear, but this may represent a new route of transmission.