In summary, orally administered probiotic strains can reduce the incidence and severity of viral RTIs. At a time when doctors are using drugs with little anti- COVID-19 data, probiotic strains documented for anti-viral and respiratory activities (not low-quality undocumented imitations) should become part of the armamentarium to reduce the burden and severity of this pandemic. Government funding is being used to test numerous drugs but just as important, they should fund probiotic trials. In addition, use of recognized prebiotics (e.g., fructans, galactans) to enhance propagation of probiotic strains and indigenous beneficial microbes should be recommended as part of the overall strategy to flatten the curve (11, 50).

https://serval.unil.ch/resource/serval:BIB_09F527C230AF.P001/REF.pdf

Using Probiotics to Flatten the Curve of Coronavirus Disease COVID-2019 Pandemic

COVID-19 is an infectious disease caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), and according to the World Health Organization (WHO), to date, SARS-CoV-2 has already infected more than 91.8 million people worldwide with 1,986,871 deaths. This virus affects mainly the respiratory system, but the gastrointestinal tract (GIT) is also a target, meanwhile SARS-CoV-2 was already detected in oesophagus, stomach, duodenum, rectum, and in fecal samples from COVID-19 patients. Prolonged GIT manifestations in COVID-19, mainly the diarrhea, were correlated with decreased richness and diversity of the gut microbiota, immune deregulation and delayed SARS-CoV-2 clearance. So, the bidirectional interactions between the respiratory mucosa and the gut microbiota, known as gut-lung axis, are supposed to be involved in the healthy or pathologic immune responses to SARS-CoV-2. In accordance, the intestinal dysbiosis is associated with increased mortality in other respiratory infections, due to an exacerbated inflammation and decreased regulatory or anti-inflammatory mechanisms in the lungs and in the gut, pointing to this important relationship between both mucosal compartments. Therefore, since the mucous membranes from the respiratory and gastrointestinal tracts are affected, in addition to dysbiosis and inflammation, it is plausible to assume that adjunctive therapies based on the modulation of the gut microbiota and re-establishment of eubiosis conditions could be an important therapeutic approach for constraining the harmful consequences of COVID-19. Then, in this review, we summarized studies showing the persistence of SARS-CoV-2 in the gastrointestinal system and the related digestive COVID-19 manifestations, in addition to the literature demonstrating nasopharyngeal, pulmonary and intestinal dysbiosis in COVID-19 patients. Lastly, we showed the potential beneficial role of probiotic administration in other respiratory infections, and discuss the possible role of probiotics as an adjunctive therapy in SARS-CoV-2 infection.

/pdf/microbiota-modulation-of-the-gut-lung-axis-in-covid-19-4exculik89.pdf

Microbiota Modulation of the Gut-Lung Axis in COVID-19.

The recent outbreak of the coronavirus disease-2019 (COVID-19) caused serious challenges to the human society in China and across the world. COVID-19 induced pneumonia in human hosts and carried a highly inter-person contagiousness. The COVID-19 patients may carry severe symptoms, and some of them may even die of major organ failures. This study utilized the machine learning algorithms to build the COVID-19 severeness detection model. Support vector machine (SVM) demonstrated a promising detection accuracy after 32 features were detected to be significantly associated with the COVID-19 severeness. These 32 features were further screened for inter-feature redundancies. The final SVM model was trained using 28 features and achieved the overall accuracy 0.8148. This work may facilitate the risk estimation of whether the COVID-19 patients would develop the severe symptoms. The 28 COVID-19 severeness associated biomarkers may also be investigated for their underlining mechanisms how they were involved in the COVID-19 infections.

Severity Detection for the Coronavirus Disease 2019 (COVID-19) Patients Using a Machine Learning Model Based on the Blood and Urine Tests

Because membrane fusion is a crucial step in the process by which enveloped viruses invade host cells, membrane fusion inhibitors can be effective drugs against enveloped viruses. We found that surfactin from Bacillus subtilis can suppress the proliferation of porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) in epithelial cells at a relatively low concentration range (15 to 50 μg/ml), without cytotoxicity or viral membrane disruption. Membrane fusion inhibition experiments demonstrate that surfactin treatment significantly reduces the rate at which the virus fuses to the cell membrane. Thermodynamic experiments show that the incorporation of small amounts of surfactin hinders the formation of negative curvature by lamellar-phase lipids, suggesting that surfactin acts a membrane fusion inhibitor. A fluorescent lipopeptide similar to surfactin was synthesized, and its ability to insert into the viral membrane was confirmed by spectroscopy. In vivo experiments have shown that oral administration of surfactin to piglets protects against PEDV infection. In conclusion, our study indicates that surfactin is a membrane fusion inhibitor with activity against enveloped viruses. As the first reported naturally occurring wedge lipid membrane fusion inhibitor, surfactin is likely to be a prototype for the development of a broad range of novel antiviral drugs.IMPORTANCE Membrane fusion inhibitors are a rapidly emerging class of antiviral drugs that inhibit the infection process of enveloped viruses. They can be classified, on the basis of the viral components targeted, as fusion protein targeting or membrane lipid targeting. Lipid-targeting membrane fusion inhibitors have a broader antiviral spectrum and are less likely to select for drug-resistant mutations. Here we show that surfactin is a membrane fusion inhibitor and has a strong antiviral effect. The insertion of surfactin into the viral envelope lipids reduces the probability of viral fusion. We also demonstrate that oral administration of surfactin protects piglets from PEDV infection. Surfactin is the first naturally occurring wedge lipid membrane fusion inhibitor that has been identified and may be effective against many viruses beyond the scope of this study. Understanding its mechanism of action provides a foundation for the development of novel antiviral agents.

Surfactin Inhibits Membrane Fusion during Invasion of Epithelial Cells by Enveloped Viruses.

Emerging viral diseases are a major threat to global health, and nearly two-thirds of emerging human infectious diseases are zoonotic. Most of the human epidemics and pandemics were caused by the spillover of viruses from wild mammals. Viruses that infect humans and a wide range of animals have historically caused devastating epidemics and pandemics. An in-depth understanding of the mechanisms of viral emergence and zoonotic spillover is still lacking. Receptors are major determinants of host susceptibility to viruses. Animal species sharing host cell receptors that support the binding of multiple viruses can play a key role in virus spillover and the emergence of novel viruses and their variants. Sialic acids (SAs), which are linked to glycoproteins and ganglioside serve as receptors for several human and animal viruses. In particular, influenza and coronaviruses, which represent two of the most important zoonotic threats, use SAs as cellular entry receptors. This is a comprehensive review of our current knowledge of SA receptor distribution among animal species and the range of viruses that use SAs as receptors. SA receptor tropism and the predicted natural susceptibility to viruses can inform targeted surveillance of domestic and wild animals to prevent the future emergence of zoonotic viruses.

https://www.mdpi.com/1999-4915/13/2/262/pdf

Sialic Acid Receptors: The Key to Solving the Enigma of Zoonotic Virus Spillover.

Transmissible gastroenteritis (TGE), caused by transmissible gastroenteritis virus (TGEV), is one many gastrointestinal inflections in piglets, characterized by diarrhea, and high mortality. Probiotics are ubiquitous bacteria in animal intestines, which have many functions, such as promoting intestinal peristalsis and maintaining the intestinal balance. We found that the supernatant of the Lp-1 strain of Lactobacillus plantarum, isolated in our laboratory, and named Lp-1s had marked anti-TGEV effect on IPEC-J2 cells. Lp-1s could induce large amounts of interferon-β in IPEC-J2 cells in the early stage (6 h) of infection with TGEV, and increased the level of phosphorylated signal transducer and activator of transcription and its nuclear translocation in the late stage (24-48 h) of infection. This resulted in upregulated expression of interferon-stimulated genes, and increased the transcription and protein expression of antiviral proteins, resulting in an anti-TGEV effect.

/pdf/anti-tgev-miller-strain-infection-effect-of-lactobacillus-2c6ng2c3rb.pdf

Anti-TGEV Miller Strain Infection Effect of Lactobacillus plantarum Supernatant Based on the JAK-STAT1 Signaling Pathway.

Transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhea virus (PEDV) are similar coronaviruses, causing diseases characterized by vomiting, diarrhea, and death from severe dehydration in piglets. Thus, they have caused huge losses to the swine-breeding industry worldwide. Nowadays, they are easily transmitted among the continents via vehicles, equipment, and cargo. Both viruses establish an infection in porcine enterocytes in the small intestine, and their spike (S) proteins play a key role in the virus-cell binding process under unfavorable conditions when the intestine with a low pH is filled with a thick layer of mucus and proteases. Sialic acid, proteases, and low pH are three main inducers of coronavirus infection. However, the details of how sialic acid and low pH affect virus binding to the host cell are not determined, and the functions of the proteases are unknown. This review emphasizes the role of three factors in the invasion of TGEV and PEDV into porcine enterocytes and offers more insights into Alphacoronavirus infection in the intestinal environment.

/pdf/three-main-inducers-of-alphacoronavirus-infection-of-mwwg4z642i.pdf

Three Main Inducers of Alphacoronavirus Infection of Enterocytes: Sialic Acid, Proteases, and Low pH.

Inhibitory effects of Lactobacillus plantarum metabolites on porcine epidemic diarrhea virus replication.

Transmissible gastroenteritis (TGE) has caused devastating economic losses to the swine industry worldwide, despite extensive research focusing on the pathogenesis of virus infection. The molecular pathogenic mechanism of TGEV-induced diarrhea in piglets is unknown. Intestinal diarrhea is closely related to the function of the Na+/H+ exchanger protein NHE3 in the brush border membrane of small intestine epithelial cells. The epidermal growth factor receptor (EGFR) may act to regulate NHE3 expression. In addition, EGFR may promote viral invasion of host cells. The present study aimed to determine whether NHE3 activity is regulated by altering EGFR expression to affect Na+ absorption in TGEV-infected intestinal epithelial cells. Porcine intestinal epithelial cells were used as models for TGEV infection. The results showed that Na+ absorption and NHE3 expression levels decreased in TGEV-infected cells. Proliferation of TGEV within IPEC-J2 cells could be inhibited by treatment with the EGFR inhibitor AG1478 and knockdown; resulting in recovery of Na+ absorption in TGEV infected cells and increasing the activity and expression of NHE3. Moreover, we demonstrated that NHE3 activity was regulated through the EGFR/ERK pathway. Importantly, NHE3 mobility on the plasma membrane of TGEV infected cells was significantly weaker than that in normal cells, and EGFR inhibition and knockdown recovered this mobility. Our research indicated that NHE3 activity was negatively regulated by EGFR in TGEV-infected intestinal epithelial cells.

/pdf/egfr-as-a-negative-regulatory-protein-adjusts-the-activity-1oydghb6l9.pdf

EGFR as a Negative Regulatory Protein Adjusts the Activity and Mobility of NHE3 in the Cell Membrane of IPEC-J2 Cells With TGEV Infection

Transmissible gastroenteritis coronavirus (TGEV) is an enteropathogenic coronavirus that causes diarrhea in pigs and is associated with high morbidity and mortality in sucking piglets. S1 is one of two protein domains in the spike (S) glycoprotein and is responsible for enteric tropism, sialic acid recognition, and host receptor binding. Although there has been extensive research on the S1 protein of TGEV, little is known about the intracellular role of TGEV-S1. In the present study, we used yeast two-hybrid screening of a cDNA library from porcine intestinal cells to identify proteins that interact with TGEV-S1. Among 120 positive clones from the library, 12 intracellular proteins were identified after sequencing and a BLAST search. These intracellular proteins are involved in protein synthesis and degradation, biological signal transduction, and negative control of signaling pathways. Using a glutathione-S-transferase (GST) pulldown assay and Co-IP, we found that UBXN1 interacts with the S1 protein. Here, we observed that TGEV infection led to increased UBXN1 expression levels during the late phase of infection in IPEC-J2 cells. Inhibition of UBXN1 in IPEC-J2 cells via siRNA interference significantly decreased the viral titer and downregulated the expression of S1. UBXN1 overexpression significantly increased the viral copy number. Additionally, we provided data suggesting that UBXN1 negatively regulates IFN-β expression after TGEV infection. Finally, our research indicated that UBXN1 plays a vital role in the process of TGEV infection, making it a candidate target for the development of a novel antiviral method.

/pdf/ubxn1-interacts-with-the-s1-protein-of-transmissible-17sczl2hmq.pdf

Luyi Xie

Papers

Anti-TGEV Miller Strain Infection Effect of Lactobacillus plantarum Supernatant Based on the JAK-STAT1 Signaling Pathway.

Three Main Inducers of Alphacoronavirus Infection of Enterocytes: Sialic Acid, Proteases, and Low pH.

Inhibitory effects of Lactobacillus plantarum metabolites on porcine epidemic diarrhea virus replication.

EGFR as a Negative Regulatory Protein Adjusts the Activity and Mobility of NHE3 in the Cell Membrane of IPEC-J2 Cells With TGEV Infection

UBXN1 interacts with the S1 protein of transmissible gastroenteritis coronavirus and plays a role in viral replication.