Gordian Knot: Gastrointestinal lesions caused by three highly pathogenic coronaviruses from SARS-CoV and MERS-CoV to SARS-CoV-2

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen of 2019 novel coronavirus disease (COVID-19), is currently spreading around the world. The WHO declared on January 31 that the outbreak of SARS-CoV-2 was a public health emergency. SARS-Cov-2 is a member of highly pathogenic coronavirus group that also consists of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV). Although respiratory tract lesions were regarded as main manifestation of SARS-Cov-2 infection, gastrointestinal lesions were also reported. Similarly, patients with SARS-CoV and MERS-CoV were also observed. Common gastrointestinal symptoms of patients mainly included diarrhea, vomiting and abdominal pain. Gastrointestinal lesions could be used as basis for early diagnosis of patients, and at the same time, controlling gastrointestinal lesions better facilitated to cut off the route of fecal-oral transmission. Hence, this review summarizes the characteristics and mechanism of gastrointestinal lesions caused by three highly pathogenic human coronavirus infections including SARS-CoV, MERS-CoV, as well as SARS-CoV-2. Furthermore, it is expected to gain experience from gastrointestinal lesions caused by SARS-CoV and MERS-CoV infections in order to be able to better relieve SARS-CoV-2 epidemic. Targetin gut microbiota to regulate the process of SARS-CoV-2 infection should be a concern. Especially, the application of nanotechnology may provide help for further controlling COVID-19.

Keywords: COVID-19; Gastrointestinal lesions; Gut microbiota; MERS; SARS; SARS-CoV-2.

Graphical abstract

Fig. 1

The timeline of coronaviruses outbreak in human history. In human history, coronaviruses have formed seven major outbreaks worldwide. In terms of time, coronaviruses outbreak cycle is showing a shortening trend. The threat of coronavirus to humans needs to be relocated, and enough vigilance and attention should be given. This epidemic of SARS-CoV-2 has given us enough implications.

Fig. 2

5′ and 3′ terminal sequences of SARS-CoV-2, SARS-CoV and MERS-CoV genomes. At the genomic level, the three coronaviruses have homology. SARS-CoV-2 and SARS-CoV have 82% structural similarity, however, it is 50% between SARS-CoV-2 and MERS-CoV. This suggests that experience can be gained from SARS-CoV and MERS-CoV outbreaks, which is very meaningful for better control of SARS-CoV-2 epidemic.

Fig. 3

The Schematic diagram of coronavirus virion structure. The virion is mostly round. The cell membrane is composed of several proteins, including spike (S) glycoprotein, the membrane (M) protein, envelope protein (E), and hemagglutinin esterase (HE). The genetic information is wrapped in the center.

Fig. 4

The target organs attacked by SARS-CoV-2 and its infection mechanism. The whole-body organs of the human body may become the target of SARS-CoV-2 attack. Additionally, SARS-CoV-2 enters the target cell with the help of the ACE2 and TMPRSS2, and completes its own replication, eventually destroying the cell.

Fig. 5

Nanoparticles are used to strengthen the intestinal barrier against SARS-CoV-2 invasions. SARS-CoV-2 can interact with intestinal microbes, resulting in decreased microbial diversity. At the same time, intestinal microbes can regulate the expression level of ACE2 and affect the virus's ability to invade. Moreover, the expression levels of inflammatory cytokines also increase accordingly. However, targeted nanoparticles can block these pathways, and then restore intestinal microbial diversity, reduce inflammation levels, and improve intestinal barrier capabilities.