Intestinal Host Response to SARS-CoV-2 Infection and COVID-19 Outcomes in Patients With Gastrointestinal Symptoms

Innate immunity, cytokine storm, and inflammatory cell death in COVID-19

The innate immune system serves as the first line of defense against invading pathogens; however, dysregulated innate immune responses can induce aberrant inflammation that is detrimental to the host. Therefore, careful innate immune regulation is critical during infections. The coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has resulted in global morbidity and mortality as well as socio-economic stresses. Innate immune sensing of SARS-CoV-2 by multiple host cell pattern recognition receptors leads to the production of various pro-inflammatory cytokines and the induction of inflammatory cell death. These processes can contribute to cytokine storm, tissue damage, and acute respiratory distress syndrome. Here, we discuss the sensing of SARS-CoV-2 to induce innate immune activation and the contribution of this innate immune signaling in the development and severity of COVID-19. In addition, we provide a conceptual framework for innate immunity driving cytokine storm and organ damage in patients with severe COVID-19. A better understanding of the molecular mechanisms regulated by innate immunity is needed for the development of targeted modalities that can improve patient outcomes by mitigating severe disease.

Gastrointestinal symptoms in COVID-19: the long and the short of it

PURPOSE OF REVIEW

A large and growing number of patients have persistent gastrointestinal symptoms that they attribute to COVID-19. SARS-CoV-2, the virus that causes COVID-19, replicates within the gut and acute COVID-19 is associated with alteration of the gut microbiome. This article reviews recent observational data related to gastrointestinal symptoms in 'long COVID' and discusses pathophysiologic mechanisms that might explain persistent post-COVID gastrointestinal symptoms.

RECENT FINDINGS

Gastrointestinal symptoms are present in half of the patients with acute COVID-19, persist 6 months after COVID-19 in 10-25% of patients, and are rated as the most bothersome symptom in 11% of all patients. These symptoms include heartburn, constipation, diarrhoea and abdominal pain and decline in prevalence with the passage of time. Long COVID gastrointestinal symptoms are associated with mental health symptoms (anxiety and depression) that predate COVID-19 and also with mental health symptoms that are concurrent, after recovery from COVID-19. The cause of long COVID gastrointestinal symptoms is unknown and hypotheses include the SARS-CoV-2 virus itself, which infects the gastrointestinal tract; COVID-19, which can be accompanied by gut microbiome changes, a profound systemic inflammatory response and critical illness; and/or effects of pandemic stress on gastrointestinal function and symptom perception, which may be unrelated to either SARS-CoV-2 or to COVID-19.

SUMMARY

New, persistent gastrointestinal symptoms are commonly reported after recovery from COVID-19. The pathophysiology of these symptoms is unknown but likely to be multifactorial.

Characteristic patterns of SARS-CoV-2 on chest CT suggests a hematologic pathway for viral entry into the lung

Many SARS-CoV-2 studies have supported the theory that the Type II alveolar epithelial cells (AEC-2) are the primary portal of entry of the virus into the lung following its brief nasal occupation. However, the theory of inhalational transmission of the virus from the ciliated and goblet nasal cells to the lung parenchyma is not supported by the imaging findings on chest computerized tomography (CT), leading the authors to consider an alternative pathway from the nose to the lung parenchyma that could explain the peripheral, basilar predominant pattern of early disease. Imaging supports that the pulmonary capillaries may be an important vehicle for transmission of the virus and/or associated inflammatory mediators to the lung epithelium.

Ischemic and hemorrhagic abdominal complications in COVID-19 patients: experience from the first Italian wave

PURPOSE

To report ischemic and haemorrhagic abdominal complications in a series of COVID-19 patients. To correlate these complications with lung involvement, laboratory tests, comorbidities, and anticoagulant treatment.

METHODS

We retrospectively included 30 COVID-19 patients who undergone abdomen CECT for abdominal pain, between March 16 and May 19, 2020. Ischemic and haemorrhagic complications were compared with lung involvement (early, progressive, peak or absorption stage), blood coagulation values, anticoagulant therapy, comorbidities, and presence of pulmonary embolism (PE).

RESULTS

Ischemic complications were documented in 10 patients (7 receiving anticoagulant therapy, 70%): 6/10 small bowel ischemia (1 concomitant obstruction, 1 perforation) and 4/10 ischemic colitis. Main mesenteric vessels were patent except for 1 superior mesenteric vein thrombosis. Two ischemia cases also presented splenic infarctions. Bleeding complications were found in 20 patients (all receiving anticoagulant treatments), half with active bleeding: hematomas in soft tissues (15) and retroperitoneum (2) and gastro-intestinal bleeding (3). Platelet and lymphocyte were within the normal range. D-Dimer was significantly higher in ischemic cases (p < 0.001). Most of the patients had severe lung disease (45% peak, 29% absorption), two patients PE.

CONCLUSIONS

Ischemic and haemorrhagic abdominal complications may occur in COVID-19 patients, particularly associated to extended lung disease. CT plays a key role in the diagnosis of these potentially life- threatening conditions.

Mucosal immunity: The missing link in comprehending SARS-CoV-2 infection and transmission

SARS-CoV-2 is primarily an airborne infection of the upper respiratory tract, which on reaching the lungs causes the severe acute respiratory disease, COVID-19. Its first contact with the immune system, likely through the nasal passages and Waldeyer's ring of tonsils and adenoids, induces mucosal immune responses revealed by the production of secretory IgA (SIgA) antibodies in saliva, nasal fluid, tears, and other secretions within 4 days of infection. Evidence is accumulating that these responses might limit the virus to the upper respiratory tract resulting in asymptomatic infection or only mild disease. The injectable systemic vaccines that have been successfully developed to prevent serious disease and its consequences do not induce antibodies in mucosal secretions of naïve subjects, but they may recall SIgA antibody responses in secretions of previously infected subjects, thereby helping to explain enhanced resistance to repeated (breakthrough) infection. While many intranasally administered COVID vaccines have been found to induce potentially protective immune responses in experimental animals such as mice, few have demonstrated similar success in humans. Intranasal vaccines should have advantage over injectable vaccines in inducing SIgA antibodies in upper respiratory and oral secretions that would not only prevent initial acquisition of the virus, but also suppress community spread via aerosols and droplets generated from these secretions.

I've looked at gut from both sides now: Gastrointestinal tract involvement in the pathogenesis of SARS-CoV-2 and HIV/SIV infections

The lumen of the gastrointestinal (GI) tract contains an incredibly diverse and extensive collection of microorganisms that can directly stimulate the immune system. There are significant data to demonstrate that the spatial localization of the microbiome can impact viral disease pathogenesis. Here we discuss recent studies that have investigated causes and consequences of GI tract pathologies in HIV, SIV, and SARS-CoV-2 infections with HIV and SIV initiating GI pathology from the basal side and SARS-CoV-2 from the luminal side. Both these infections result in alterations of the intestinal barrier, leading to microbial translocation, persistent inflammation, and T-cell immune activation. GI tract damage is one of the major contributors to multisystem inflammatory syndrome in SARS-CoV-2-infected individuals and to the incomplete immune restoration in HIV-infected subjects, even in those with robust viral control with antiretroviral therapy. While the causes of GI tract pathologies differ between these virus families, therapeutic interventions to reduce microbial translocation-induced inflammation and improve the integrity of the GI tract may improve the prognoses of infected individuals.

What Do We Know Today about Long COVID? Nursing Care for a New Clinical Syndrome

Persistent COVID, long COVID, long-effects, long-term effects or chronic COVID are all names of a new syndrome caused by a set of multi-organ symptoms that appear after having been infected with SARS-CoV-2 [...].

SARS-CoV-2 induces barrier damage and inflammatory responses in the human iPSC-derived intestinal epithelium

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread and led to global health crises. COVID-19 causes well-known respiratory failure and gastrointestinal symptoms, such as diarrhea, nausea, and vomiting. Thus, human gastrointestinal cell models are urgently needed for COVID-19 research; however, it is difficult to obtain primary human intestinal cells. In this study, we examined whether human induced pluripotent stem cell (iPSC)-derived small intestinal epithelial cells (iPSC-SIECs) could be used as a SARS-CoV-2 infection model. We observed that iPSC-SIECs, such as absorptive and Paneth cells, were infected with SARS-CoV-2, and remdesivir treatment decreased intracellular SARS-CoV-2 replication in iPSC-SIECs. SARS-CoV-2 infection decreased expression levels of tight junction markers, ZO-3 and CLDN1, and transepithelial electrical resistance (TEER), which evaluates the integrity of tight junction dynamics. In addition, SARS-CoV-2 infection increased expression levels of proinflammatory genes, which are elevated in patients with COVID-19. These findings suggest iPSC-SIECs as a useful in vitro model for elucidating COVID-19 pathology and drug development.

Severe Acute Respiratory Syndrome Coronavirus 2 Is Detected in the Gastrointestinal Tract of Asymptomatic Endoscopy Patients but Is Unlikely to Pose a Significant Risk to Healthcare Personnel

Background and Aims

Recent evidence suggests that the gut is an additional target for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, whether SARS-CoV-2 spreads via gastrointestinal secretions remains unclear. To determine the prevalence of gastrointestinal SARS-CoV-2 infection in asymptomatic subjects, we analyzed gastrointestinal biopsy and liquid samples from endoscopy patients for the presence of SARS-CoV-2.

Methods

We enrolled 100 endoscopic patients without known SARS-CoV-2 infection (cohort A) and 12 patients with a previous COVID-19 diagnosis (cohort B) in a cohort study performed at a regional hospital. Gastrointestinal biopsies and fluids were screened for SARS-CoV-2 by polymerase chain reaction (PCR), immunohistochemistry, and virus isolation assay, and the stability of SARS-CoV-2 in gastrointestinal liquids in vitro was analyzed.

Results

SARS-CoV-2 ribonucleic acid was detected by PCR in the colonic tissue of 1/100 patients in cohort A. In cohort B, 3 colonic liquid samples tested positive for SARS-CoV-2 by PCR and viral nucleocapsid protein was detected in the epithelium of the respective biopsy samples. However, no infectious virions were recovered from any samples. In vitro exposure of SARS-CoV-2 to colonic liquid led to a 4-log-fold reduction of infectious SARS-CoV-2 within 1 hour (P ≤ .05).

Conclusion

Overall, the persistent detection of SARS-CoV-2 in endoscopy samples after resolution of COVID-19 points to the gut as a long-term reservoir for SARS-CoV-2. Since no infectious virions were recovered and SARS-CoV-2 was rapidly inactivated in the presence of colon liquids, it is unlikely that performing endoscopic procedures is associated with a significant infection risk due to undiagnosed asymptomatic or persistent gastrointestinal SARS-CoV-2 infections.

ACE2, B0AT1, and SARS-CoV-2 spike protein: Structural and functional implications

The coronavirus disease 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has emerged as a public health crisis and led to tremendous economic devastation. The spike protein (S) of SARS-CoV-2 hijacks the angiotensin converting enzyme 2 (ACE2) as a receptor for virus entry, representing the initial step of viral infection. S is one of the major targets for development of the antiviral drugs, antibodies, and vaccines. ACE2 is a peptidase that plays a physiologically important role in the renin-angiotensin system. Concurrently, it also forms dimer of heterodimer with the neutral amino acid transporter B⁰AT1 to regulate intestinal amino acid metabolism. The symptoms of COVID-19 are closely correlated with the physiological functions of ACE2. In this review, we summarize the functional and structural studies on ACE2, B⁰AT1, and their complex with S of SARS-CoV-2, providing insights into the various symptoms caused by viral infection and the development of therapeutic strategies.

Gastrointestinal Involvement in SARS-CoV-2 Infection

SARS-CoV-2 has evolved into a virus that primarily results in mild or asymptomatic disease, making its transmission more challenging to control. In addition to the respiratory tract, SARS-CoV-2 also infects the digestive tract. Some gastrointestinal symptoms occur with or before respiratory symptoms in patients with COVID-19. Respiratory infections are known to cause intestinal immune impairment and gastrointestinal symptoms. When the intestine is inflamed, cytokines affect the lung immune response and inflammation through blood circulation. The gastrointestinal microbiome may be a modifiable factor in determining the risk of SARS-CoV-2 infection and disease severity. The development of oral SARS-CoV-2 vaccine candidates and the maintenance of gut microbiota profiles may contribute to the early control of COVID-19 outbreaks. To this end, this review summarizes information on the gastrointestinal complications caused by SARS-CoV-2, SARS-CoV-2 infection, the gastrointestinal–lung axis immune response, potential control strategies for oral vaccine candidates and maintaining intestinal microbiota homeostasis.

SARS CoV-2-Induced Viral Sepsis: The Role of Gut Barrier Dysfunction

A considerable proportion of patients with severe COVID-19 meet Sepsis-3 criteria and share common pathophysiological mechanisms of multiorgan injury with bacterial sepsis, in absence of secondary bacterial infections, a process characterized as “viral sepsis”. The intestinal barrier exerts a central role in the pathophysiological sequence of events that lead from SARS-CoV-2 infection to severe systemic complications. Accumulating evidence suggests that SARS-CoV-2 disrupts the integrity of the biological, mechanical and immunological gut barrier. Specifically, microbiota diversity and beneficial bacteria population are reduced, concurrently with overgrowth of pathogenic bacteria (dysbiosis). Enterocytes’ tight junctions (TJs) are disrupted, and the apoptotic death of intestinal epithelial cells is increased leading to increased gut permeability. In addition, mucosal CD4(+) and CD8(+) T cells, Th17 cells, neutrophils, dendritic cells and macrophages are activated, and T-regulatory cells are decreased, thus promoting an overactivated immune response, which further injures the intestinal epithelium. This dysfunctional gut barrier in SARS-CoV-2 infection permits the escape of luminal bacteria, fungi and endotoxin to normally sterile extraintestinal sites and the systemic circulation. Pre-existing gut barrier dysfunction and endotoxemia in patients with comorbidities including cardiovascular disease, obesity, diabetes and immunosuppression predisposes to aggravated endotoxemia. Bacterial and endotoxin translocation promote the systemic inflammation and immune activation, which characterize the SARS-CoV-2 induced “viral sepsis” syndrome associated with multisystemic complications of severe COVID-19.

Duodenal Mucosal Expression of COVID-19-Related Genes in Health, Diabetic Gastroenteropathy, and Functional Dyspepsia

CONTEXT

SARS-CoV-2 infects the gastrointestinal tract and may be associated with symptoms that resemble diabetic gastroparesis. Why patients with diabetes who contract COVID-19 are more likely to have severe disease is unknown.

OBJECTIVE

We aimed to compare the duodenal mucosal expression of SARS-CoV-2 and inflammation-related genes in diabetes gastroenteropathy (DGE), functional dyspepsia (FD), and healthy controls.

METHODS

Gastrointestinal transit, and duodenal mucosal mRNA expression of selected genes were compared in 21 controls, 39 DGE patients, and 37 FD patients from a tertiary referral center. Pathway analyses were performed.

RESULTS

Patients had normal, delayed (5 FD [13%] and 13 DGE patients [33%]; P = 0.03 vs controls), or rapid (5 FD [12%] and 5 DGE [12%]) gastric emptying (GE). Compared with control participants, 100 SARS-CoV-2-related genes were increased in DGE (FDR < 0.05) vs 13 genes in FD; 71 of these 100 genes were differentially expressed in DGE vs FD but only 3 between DGE patients with normal vs delayed GE. Upregulated genes in DGE include the SARS-CoV2 viral entry genes CTSL (|Fold change [FC]|=1.16; FDR < 0.05) and CTSB (|FC|=1.24; FDR < 0.05) and selected genes involved in viral replication (eg, EIF2 pathways) and inflammation (CCR2, CXCL2, and LCN2, but not other inflammation-related pathways eg, IL-2 and IL-6 signaling).

CONCLUSION

Several SARS-CoV-2-related genes were differentially expressed between DGE vs healthy controls and vs FD but not between DGE patients with normal vs delayed GE, suggesting that the differential expression is related to diabetes per se. The upregulation of CTSL and CTSB and replication genes may predispose to SARS-CoV2 infection of the gastrointestinal tract in diabetes.

SARS-CoV-2: Reinfection after 18 Months of a Previous Case with Multiple Negative Nasopharyngeal Swab Tests and Positive Fecal Molecular Test

This short communication describes the reinfection after nearly 18 months of the same patient who was previously infected with coronavirus disease 2019 (COVID-19) and who showed multiple negative real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) results by nasal swabs for severe acute respiratory syndrome coronavirus (SARS-CoV-2) but positive results on a fecal sample. We previously noted how, in the presence of symptoms suggestive of pneumonia, visible on a chest computed tomography (CT) scan and confirmed by fecal molecular testing, it was possible to draw the diagnosis of SARS-CoV-2 infection. One year later, the same patient was again affected by SARS-CoV-2. This time, the first antigenic nasal swab showed readily positive results. However, the patient’s clinical course appeared to be more attenuated, showing no signs of pulmonary involvement in the radiographic examinations performed. This case shows a novelty in the pulmonary radiological evaluation of new SARS-CoV-2 infection.

Asymptomatic SARS-CoV-2 Infection Is Associated With Higher Levels of Serum IL-17C, Matrix Metalloproteinase 10 and Fibroblast Growth Factors Than Mild Symptomatic COVID-19

Young adults infected with SARS-CoV-2 are frequently asymptomatic or develop only mild disease. Because capturing representative mild and asymptomatic cases require active surveillance, they are less characterized than moderate or severe cases of COVID-19. However, a better understanding of SARS-CoV-2 asymptomatic infections might shed light into the immune mechanisms associated with the control of symptoms and protection. To this aim, we have determined the temporal dynamics of the humoral immune response, as well as the serum inflammatory profile, of mild and asymptomatic SARS-CoV-2 infections in a cohort of 172 initially seronegative prospectively studied United States Marine recruits, 149 of whom were subsequently found to be SARS-CoV-2 infected. The participants had blood samples taken, symptoms surveyed and PCR tests for SARS-CoV-2 performed periodically for up to 105 days. We found similar dynamics in the profiles of viral load and in the generation of specific antibody responses in asymptomatic and mild symptomatic participants. A proteomic analysis using an inflammatory panel including 92 analytes revealed a pattern of three temporal waves of inflammatory and immunoregulatory mediators, and a return to baseline for most of the inflammatory markers by 35 days post-infection. We found that 23 analytes were significantly higher in those participants that reported symptoms at the time of the first positive SARS-CoV-2 PCR compared with asymptomatic participants, including mostly chemokines and cytokines associated with inflammatory response or immune activation (i.e., TNF-α, TNF-β, CXCL10, IL-8). Notably, we detected 7 analytes (IL-17C, MMP-10, FGF-19, FGF-21, FGF-23, CXCL5 and CCL23) that were higher in asymptomatic participants than in participants with symptoms; these are known to be involved in tissue repair and may be related to the control of symptoms. Overall, we found a serum proteomic signature that differentiates asymptomatic and mild symptomatic infections in young adults, including potential targets for developing new therapies and prognostic tests.

Presence of diarrhea associated with better outcomes in patients with COVID-19 - A prospective evaluation

Purpose

Gastrointestinal (GI) manifestations have been well documented in patients with coronavirus disease 2019 (COVID-19), but its clinical impact on the course of the disease is debatable. Majority of the available data is retrospective, and hence this prospective study was planned to study the impact of GI symptoms on COVID-19 outcome.

Methods

All COVID-19 patients admitted in a tertiary care centre from August–October 2020 were screened and patients without pre-existing GI diseases were included. A detailed history of the various symptoms including duration was documented. Various baseline laboratory investigations and inflammatory markers were conducted as per the protocol. Patients with and without diarrhea were compared for the various disease outcome parameters.

Results

Of the 244 patients screened, 203 patients (128 males; 63.1%) were included. Respiratory symptoms alone were present in 49 (24.1%), GI symptoms alone in 20 (9.9%) and 117 (57.6%) had both. Overall GI symptoms was noted in 137 (67.5%) cases with the commonest being diarrhea (61; 30.0%). Patients with both respiratory and any GI symptoms showed a lower trend towards need for mechanical ventilation (12.2% vs 7.7%; p ​= ​0.35) and mortality (10.2% vs 4.3%; p ​= ​0.14) compared to respiratory symptoms alone, although not statistically significant. Patients with diarrhea (n ​= ​61) had no mortality (0% vs 7.7%; p ​= ​0.036) or need for mechanical ventilation and shorter hospital stay compared to those who did not have diarrhea.

Conclusion

GI symptoms are frequent in patients with SARS-CoV-2 infection and the commonest is diarrhea. Diarrhea is a harbinger of better outcome with lower mortality among COVID-19 positive patients.

Effective Regulation of Gut Microbiota With Probiotics and Prebiotics May Prevent or Alleviate COVID-19 Through the Gut-Lung Axis

Coronavirus disease 2019 (COVID-19) can disrupt the gut microbiota balance, and patients usually have intestinal disorders. The intestine is the largest immune organ of the human body, and gut microbes can affect the immune function of the lungs through the gut-lung axis. Many lines of evidence support the role of beneficial bacteria in enhancing human immunity, preventing pathogen colonization, and thereby reducing the incidence and severity of infection. In this article, we review the possible approach of modulating microbiota to help prevent and treat respiratory tract infections, including COVID-19, and discuss the possibility of using probiotics and prebiotics for this purpose. We also discuss the mechanism by which intestinal micro-flora regulate immunity and the effects of probiotics on the intestinal micro-ecological balance. Based on this understanding, we propose the use of probiotics and prebiotics to modulate gut microbiota for the prevention or alleviation of COVID-19 through the gut-lung axis.

Potential Application of Tea Polyphenols to the Prevention of COVID-19 Infection: Based on the Gut-Lung Axis

Coronavirus disease 2019 (COVID-19) disrupts the intestinal micro-ecological balance, and patients often develop the intestinal disease. The gut is the largest immune organ in the human body; intestinal microbes can affect the immune function of the lungs through the gut-lung axis. It has been reported that tea polyphenols (TPs) have antiviral and prebiotic activity. In this review, we discussed TPs reduced lung-related diseases through gut-lung axis by inhibiting dysbiosis. In addition, we also highlighted the preventive and therapeutic effects of TPs on COVID-19 complications, further demonstrating the importance of research on TPs for the prevention and treatment of COVID-19 in humans. Based on this understanding, we recommend using TPs to regulate the gut microbiota to prevent or alleviate COVID-19 through the gut-lung axis.

Increased Sensitivity of SARS-CoV-2 to Type III Interferon in Human Intestinal Epithelial Cells

The coronavirus SARS-CoV-2 caused the COVID-19 global pandemic leading to 5.3 million deaths worldwide as of December 2021. The human intestine was found to be a major viral target which could have a strong impact on virus spread and pathogenesis since it is one of the largest organs. While type I interferons (IFNs) are key cytokines acting against systemic virus spread, in the human intestine type III IFNs play a major role by restricting virus infection and dissemination without disturbing homeostasis. Recent studies showed that both type I and III IFNs can inhibit SARS-CoV-2 infection, but it is not clear whether one IFN controls SARS-CoV-2 infection of the human intestine better or with a faster kinetics. In this study, we could show that type I and III IFNs both possess antiviral activity against SARS-CoV-2 in human intestinal epithelial cells (hIECs); however, type III IFN is more potent. Shorter type III IFN pretreatment times and lower concentrations were required to efficiently reduce virus load compared to type I IFNs. Moreover, type III IFNs significantly inhibited SARS-CoV-2 even 4 h postinfection and induced a long-lasting antiviral effect in hIECs. Importantly, the sensitivity of SARS-CoV-2 to type III IFNs was virus specific since type III IFN did not control VSV infection as efficiently. Together, these results suggest that type III IFNs have a higher potential for IFN-based treatment of SARS-CoV-2 intestinal infection compared to type I IFNs. IMPORTANCE SARS-CoV-2 infection is not restricted to the respiratory tract and a large number of COVID-19 patients experience gastrointestinal distress. Interferons are key molecules produced by the cell to combat virus infection. Here, we evaluated how two types of interferons (type I and III) can combat SARS-CoV-2 infection of human gut cells. We found that type III interferons were crucial to control SARS-CoV-2 infection when added both before and after infection. Importantly, type III interferons were also able to produce a long-lasting effect, as cells were protected from SARS-CoV-2 infection up to 72 h posttreatment. This study suggested an alternative treatment possibility for SARS-CoV-2 infection.

Colonization of the live biotherapeutic product VE303 and modulation of the microbiota and metabolites in healthy volunteers

Manipulation of the gut microbiota via fecal microbiota transplantation (FMT) has shown clinical promise in diseases such as recurrent Clostridioides difficile infection (rCDI). However, the variable nature of this approach makes it challenging to describe the relationship between fecal strain colonization, corresponding microbiota changes, and clinical efficacy. Live biotherapeutic products (LBPs) consisting of defined consortia of clonal bacterial isolates have been proposed as an alternative therapeutic class because of their promising preclinical results and safety profile. We describe VE303, an LBP comprising 8 commensal Clostridia strains under development for rCDI, and its early clinical development in healthy volunteers (HVs). In a phase 1a/b study in HVs, VE303 is determined to be safe and well-tolerated at all doses tested. VE303 strains optimally colonize HVs if dosed over multiple days after vancomycin pretreatment. VE303 promotes the establishment of a microbiota community known to provide colonization resistance.

Intestinal Damage in COVID-19: SARS-CoV-2 Infection and Intestinal Thrombosis

The intestinal tract, with high expression of angiotensin-converting enzyme 2 (ACE2), is a major site of extrapulmonary infection in COVID-19. During pulmonary infection, the virus enters the bloodstream forming viremia, which infects and damages extrapulmonary organs. Uncontrolled viral infection induces cytokine storm and promotes a hypercoagulable state, leading to systemic microthrombi. Both viral infection and microthrombi can damage the gut–blood barrier, resulting in malabsorption, malnutrition, and intestinal flora entering the blood, ultimately increasing disease severity and mortality. Early prophylactic antithrombotic therapy can prevent these damages, thereby reducing mortality. In this review, we discuss the effects of SARS-CoV-2 infection and intestinal thrombosis on intestinal injury and disease severity, as well as corresponding treatment strategies.

Understanding on the possible routes for SARS CoV-2 invasion via ACE2 in the host linked with multiple organs damage

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), accountable for causing the coronavirus diseases 2019 (COVID-19), is already declared as a pandemic disease globally. Like previously reported SARS-CoV strain, the novel SARS-CoV-2 also initiates the viral pathogenesis via docking viral spike-protein with the membranal angiotensin-converting enzyme 2 (ACE2) - a receptor on variety of cells in the human body. Therefore, COVID-19 is broadly characterized as a disease that targets multiple organs, particularly causing acute complications via organ-specific pathogenesis accompanied by destruction of ACE2+ cells, including alveolus, cardiac microvasculature, endothelium, and glomerulus. Under such circumstances, the high expression of ACE2 in predisposing individuals associated with anomalous production of the renin-angiotensin system (RAS) may promote enhanced viral load in COVID-19, which comparatively triggers excessive apoptosis. Furthermore, multi-organ injuries were found linked to altered ACE2 expression and inequality between the ACE2/angiotensin-(1-7)/mitochondrial Ang system (MAS) and renin-angiotensin-system (RAS) in COVID-19 patients. However, the exact pathogenesis of multi-organ damage in COVID-19 is still obscure, but several perspectives have been postulated, involving altered ACE2 expression linked with direct/indirect damages by the virus-induced immune responses, such as cytokinin storm. Thus, insights into the invasion of a virus with respect to ACE2 expression site can be helpful to simulate or understand the possible complications in the targeted organ during viral infection. Hence, this review summarizes the multiple organs invasion by SARS CoV-2 linked with ACE2 expression and their consequences, which can be helpful in the management of the COVID-19 pathogenesis under life-threatening conditions.

Dealing with a mucosal viral pandemic: lessons from COVID-19 vaccines

The development and deployment of vaccines against COVID-19 demonstrated major successes in providing immunity and preventing severe disease and death. Yet SARS-CoV-2 evolves and vaccine-induced protection wanes, meaning progress in vaccination strategies is of upmost importance. New vaccines directed at emerging viral strains are being developed while vaccination schemes with booster doses and combinations of different platform-based vaccines are being tested in trials and real-world settings. Despite these diverse approaches, COVID-19 vaccines are only delivered intramuscularly, whereas the nasal mucosa is the primary site of infection with SARS-CoV-2. Preclinical mucosal vaccines with intranasal or oral administration demonstrate promising results regarding mucosal IgA generation and tissue-resident lymphocyte responses against SARS-CoV-2. By mounting an improved local humoral and cell-mediated response, mucosal vaccination could be a safe and effective way to prevent infection, block transmission and contribute to reduce SARS-CoV-2 spread. However, questions and limitations remain: how effectively and reproducibly will vaccines penetrate mucosal barriers? Will vaccine-induced mucosal IgA responses provide sustained protection against infection?

The immunology and immunopathology of COVID-19

Considerable research effort has been made worldwide to decipher the immune response triggered upon severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, identify the drivers of severe and fatal COVID-19, and understand what leads to the prolongation of symptoms after disease resolution. We review the results of almost 2 years of COVID-19 immunology research and discuss definitive findings and remaining questions regarding our understanding of COVID-19 pathophysiology. We discuss emerging understanding of differences in immune responses seen in those with and without Long Covid syndrome, also known as post-acute sequelae of SARS-CoV-2. We hope that the knowledge gained from this COVID-19 research will be applied in studies of inflammatory processes involved in critical and chronic illnesses, which remain a major unmet need.

Are gastrointestinal symptoms associated with higher risk of Mortality in COVID-19 patients? A systematic review and meta-analysis

BACKGROUND

Gastrointestinal symptoms have been reported in patients with COVID-19. Several clinical investigations suggested that gastrointestinal symptoms were associated with disease severity of COVID-19. However, the relevance of gastrointestinal symptoms and mortality of COVID-19 remains largely unknown. We aim to investigate the relationship between gastrointestinal symptoms and COVID-19 mortality.

METHODS

We searched the PubMed, Embase, Web of science and Cochrane for studies published between Dec 1, 2019 and May 1, 2021, that had data on gastrointestinal symptoms in COVID-19 patients. Additional literatures were obtained by screening the citations of included studies and recent reviews. Only studies that reported the mortality of COVID-19 patients with/without gastrointestinal symptoms were included. Raw data were pooled to calculate OR (Odds Ratio). The mortality was compared between patients with and without gastrointestinal symptoms, as well as between patients with and without individual symptoms (diarrhea, nausea/vomiting, abdominal pain).

RESULTS

Fifty-three literatures with 55,245 COVID-19 patients (4955 non-survivors and 50,290 survivors) were included. The presence of GI symptoms was not associated with the mortality of COVID-19 patients (OR=0.88; 95% CI 0.71-1.09; P=0.23). As for individual symptoms, diarrhea (OR=1.01; 95% CI 0.72-1.41; P=0.96), nausea/vomiting (OR=1.16; 95% CI 0.78-1.71; P=0.46) and abdominal pain (OR=1.55; 95% CI 0.68-3.54; P=0.3) also showed non-relevance with the death of COVID-19 patients.

CONCLUSIONS

Gastrointestinal symptoms are not associated with higher mortality of COVID-19 patients. The prognostic value of gastrointestinal symptoms in COVID-19 requires further investigation.

Gustatory and Saliva Secretory Dysfunctions in COVID-19 Patients with Zinc Deficiency

Given the ever-progressing studies on coronavirus disease 2019 (COVID-19), it is critical to update our knowledge about COVID-19 symptomatology and pathophysiology. In the present narrative review, oral symptoms were overviewed using the latest data and their pathogenesis was hypothetically speculated. PubMed, LitCovid, ProQuest, and Google Scholar were searched for relevant studies from 1 April 2021 with a cutoff date of 31 January 2022. The literature search indicated that gustatory dysfunction and saliva secretory dysfunction are prevalent in COVID-19 patients and both dysfunctions persist after recovery from the disease, suggesting the pathogenic mechanism common to these cooccurring symptoms. COVID-19 patients are characterized by hypozincemia, in which zinc is possibly redistributed from blood to the liver at the expense of zinc in other tissues. If COVID-19 induces intracellular zinc deficiency, the activity of zinc-metalloenzyme carbonic anhydrase localized in taste buds and salivary glands may be influenced to adversely affect gustatory and saliva secretory functions. Zinc-binding metallothioneins and zinc transporters, which cooperatively control cellular zinc homeostasis, are expressed in oral tissues participating in taste and saliva secretion. Their expression dysregulation associated with COVID-19-induced zinc deficiency may have some effect on oral functions. Zinc supplementation is expected to improve oral symptoms in COVID-19 patients.

Functional gastrointestinal and somatoform symptoms five months after SARS-CoV-2 infection: A controlled cohort study

BACKGROUND

Gastrointestinal infections represent a risk factor for functional gastrointestinal and somatoform extraintestinal disorders. We investigated the prevalence and relative risk (RR) of gastrointestinal and somatoform symptoms 5 months after SARS-CoV-2 infection compared with a control cohort.

METHODS

One hundred and sixty-four SARS-CoV-2 infected patients and 183 controls responded to an online questionnaire about symptoms and signs during the acute phase of the infection and after 4.8 ± 0.3 months. Presence and severity of gastrointestinal symptoms, somatization, anxiety, and depression were recorded with standardized questionnaires. Stool form and presence of irritable bowel syndrome (IBS) were also recorded. Any association between exposure to infection and symptoms was evaluated by calculating crude and adjusted RR values and score differences with 95% confidence intervals (CI).

KEY RESULTS

Fever, dyspnea, loss of smell/taste/weight, diarrhea, myalgia, arthralgia, and asthenia were reported by more than 40% of patients during the acute phase. Compared with controls, adjusted RRs for loose stools, chronic fatigue, and somatization were increased after infection: 1.88 (95% CI 0.99-3.54), 2.24 (95% CI 1.48-3.37), and 3.62 (95% CI 1.01-6.23), respectively. Gastrointestinal sequelae were greater in patients with diarrhea during the acute phase.

CONCLUSIONS & INFERENCES

Mild gastroenterological symptoms persist 5 months after SARS-CoV-2 infection, in particular in patients reporting diarrhea in the acute phase. Infected patients are at increased risk of chronic fatigue and somatoform disorders, thus supporting the hypothesis that both functional gastrointestinal and somatoform disorders may have a common biological origin.

Pathological sequelae of long-haul COVID

The world continues to contend with successive waves of coronavirus disease 2019 (COVID-19), fueled by the emergence of viral variants. At the same time, persistent, prolonged and often debilitating sequelae are increasingly recognized in convalescent individuals, named 'post-COVID-19 syndrome' or 'long-haul COVID'. Clinical symptomatology includes fatigue, malaise, dyspnea, defects in memory and concentration and a variety of neuropsychiatric syndromes as the major manifestations, and several organ systems can be involved. The underlying pathophysiological mechanisms are poorly understood at present. This Review details organ-specific sequelae of post-COVID-19 syndromes and examines the underlying pathophysiological mechanisms available so far, elaborating on persistent inflammation, induced autoimmunity and putative viral reservoirs. Finally, we propose diagnostic strategies to better understand this heterogeneous disorder that continues to afflict millions of people worldwide.

Opposing roles for sMAdCAM and IL‐15 in COVID‐19 associated cellular immune pathology

Immune cell dysregulation and lymphopenia characterize COVID‐19 pathology in moderate to severe disease. While underlying inflammatory factors have been extensively studied, homeostatic and mucosal migratory signatures remain largely unexplored as causative factors. In this study, we evaluated the association of circulating IL‐6, soluble mucosal addressin cell adhesion molecule (sMAdCAM), and IL‐15 with cellular dysfunction characterizing mild and hypoxemic stages of COVID‐19. A cohort of SARS‐CoV‐2 infected individuals (n = 130) at various stages of disease progression together with healthy controls (n = 16) were recruited from COVID Care Centres (CCCs) across Mumbai, India. Multiparametric flow cytometry was used to perform in‐depth immune subset characterization and to measure plasma IL‐6 levels. sMAdCAM, IL‐15 levels were quantified using ELISA. Distinct depletion profiles, with relative sparing of CD8 effector memory and CD4+ regulatory T cells, were observed in hypoxemic disease within the lymphocyte compartment. An apparent increase in the frequency of intermediate monocytes characterized both mild as well as hypoxemic disease. IL‐6 levels inversely correlated with those of sMAdCAM and both markers showed converse associations with observed lympho‐depletion suggesting opposing roles in pathogenesis. Interestingly, IL‐15, a key cytokine involved in lymphocyte activation and homeostasis, was detected in symptomatic individuals but not in healthy controls or asymptomatic cases. Further, plasma IL‐15 levels negatively correlated with T, B, and NK count suggesting a compensatory production of this cytokine in response to the profound lymphopenia. Finally, higher levels of plasma IL‐15 and IL‐6, but not sMAdCAM, were associated with a longer duration of hospitalization.

Gastrointestinal Manifestations of Coronavirus Disease 2019 Across the United States: A Multicenter Cohort Study

Background and Aims

Gastrointestinal (GI) symptoms occur among patients diagnosed with coronavirus disease 2019 (COVID-19), and there is clear evidence that SARS-CoV-2, the causative pathogen, infects the GI tract. In this large, multicenter cohort study, we evaluated variations in gastrointestinal and hepatic manifestations of COVID-19 throughout the United States (US).

Methods

Patients hospitalized with a positive COVID-19 test prior to October 2020 were identified at 7 US academic centers. Demographics, presenting symptoms, laboratory data, and hospitalization outcomes were abstracted. Descriptive and regression analyses were used to evaluate GI manifestations and their potential predictors.

Results

Among 2031 hospitalized patients with COVID-19, GI symptoms were present in 18.9%; diarrhea was the most common (15.2%), followed by nausea and/or vomiting (12.6%) and abdominal pain (6.0%). GI symptoms were less common in the Western cohort (16.0%) than the Northeastern (25.6%) and Midwestern (26.7%) cohorts. Compared to nonintensive care unit (ICU) patients, ICU patients had a higher prevalence of abnormal aspartate aminotransferase (58.1% vs 37.3%; P < .01), alanine aminotransferase (37.5% vs 29.3%; P = .01), and total bilirubin (12.7% vs 9.0%; P < .01). ICU patients also had a higher mortality rate (22.7% vs 4.7%; P < .01). Chronic liver disease was associated with the development of GI symptoms. Abnormal aspartate aminotransferase or alanine aminotransferase was associated with an increased risk of ICU admission.

Conclusion

We present the largest multicenter cohort of patients with COVID-19 across the United States. GI manifestations were common among patients hospitalized with COVID-19, although there was significant variability in prevalence and predictors across the United States.

A bird's eye view on the role of dendritic cells in SARS-CoV-2 infection: Perspectives for immune-based vaccines

Coronavirus disease-19 (COVID-19) is a complex disorder caused by the pandemic diffusion of a novel coronavirus named SARS-CoV-2. Clinical manifestations vary from silent infection to severe pneumonia, disseminated thrombosis, multi-organ failure, and death. COVID-19 pathogenesis is still not fully elucidated, while increasing evidence suggests that disease phenotypes are strongly related to the virus-induced immune system's dysregulation. Indeed, when the virus-host cross talk is out of control, the occurrence of an aberrant systemic inflammatory reaction, named "cytokine storm," leads to a detrimental impairment of the adaptive immune response. Dendritic cells (DCs) are the most potent antigen-presenting cells able to support innate immune and promote adaptive responses. Besides, DCs play a key role in the anti-viral defense. The aim of this review is to focus on DC involvement in SARS-CoV-2 infection to better understand pathogenesis and clinical behavior of COVID-19 and explore potential implications for immune-based therapy strategies.

Can SARS-CoV-2 be transmitted via faeces?

PURPOSE OF REVIEW

COVID-19 patients can present gastrointestinal symptoms, being diarrhoea one of the most frequent, suggesting intestinal health can be impacted by COVID-19. Here, we will discuss whether there is a correlation between the presence of SARS-CoV-2 RNA in faeces and diarrhoea, the relevance of gastrointestinal symptoms in disease diagnosis and transmission, and how COVID-19 can impact the gut microbial balance.

RECENT FINDINGS

SARS-CoV-2 RNA has been reported in faeces or rectal swabs of COVID-19 patients with and without diarrhoea, suggesting faecal shedding can occur independently of gastrointestinal symptoms. However, the presence of the virus in the intestine can persist beyond its presence in the respiratory tract, with some reports suggesting that SARS-CoV-2 in the faeces can be infectious.COVID-19 can impact the gut microbiota causing an enhancement of biosynthesis pathways that favour the expansion of bacterial pathogens in the inflamed gut, and causing a decline in commensals involved in the human immune response.

SUMMARY

Gastrointestinal symptoms may be the first indication of COVID-19. SARS-CoV-2 in faeces can potentiate routes of disease transmission, particularly as the high viral loads reported in patients with severe illness suggest virus replication in the intestine may be possible.

Relationship Between Body Composition and Death in Patients with COVID-19 Differs Based on the Presence of Gastrointestinal Symptoms

BACKGROUND

Patients with SARS-CoV-2 who present with gastrointestinal symptoms have a milder clinical course than those who do not. Risk factors for severe COVID-19 disease include increased adiposity and sarcopenia.

AIMS

To determine whether body composition risk factors are associated with worse outcomes among patients with gastrointestinal symptoms.

METHODS

This was a retrospective study of hospitalized patients with COVID-19 who underwent abdominal CT scan for clinical indications. Abdominal body composition measures including skeletal muscle index (SMI), intramuscular adipose tissue index (IMATI), visceral adipose tissue index (VATI), subcutaneous adipose tissue index (SATI), visceral-to-subcutaneous adipose tissue ratio (VAT/SAT ratio), and liver and spleen attenuation were collected. The association between body composition measurements and 30-day mortality was evaluated in patients with and without gastrointestinal symptoms at the time of positive SARS-CoV-2 test.

RESULTS

Abdominal CT scans of 190 patients with COVID-19 were evaluated. Gastrointestinal symptoms including nausea, vomiting, diarrhea, or abdominal pain were present in 117 (62%). Among patients without gastrointestinal symptoms, those who died had greater IMATI (p = 0.049), less SMI (p = 0.010), and a trend toward a greater VAT/SAT ratio. Among patients with gastrointestinal symptoms, those who died had significantly greater IMATI (p = 0.025) but no differences in other measures.

CONCLUSIONS

Among patients with COVID-19, those without gastrointestinal symptoms showed the expected associations between mortality and low SMI, high IMATI, and trend toward higher VAT/SAT ratio, but those with gastrointestinal symptoms did not. Future studies should explore the mechanisms for the altered disease course in patients with COVID-19 who present with gastrointestinal symptoms.

Evidence of SARS-CoV-2 infection in gallbladder and aggravating cholecystitis to septic shock: a case report

Coronavirus disease 2019 (COVID-19) has threatened human health worldwide and could lead to multiple organs injury. However, the impact on the virus infecting the biliary system, especially the gallbladder, has remained unclear and no pathological evidence has been reported yet. A case of SARS-CoV-2 infection in a gallbladder with cholecystitis, which progressed rapidly to sepsis and required an emergency operation was investigated and reported. Clinical specimens of the COVID-19 patient including serum, oropharyngeal swabs, sputum, bile, abdominal drainage fluid, urine, stool, and gallbladder tissue were collected and tested for SARS-CoV-2 RNA using a quantitative polymerase chain reaction (qPCR) assay. Fresh normal gallbladder tissue and gangrenous gallbladder tissue were also collected for further research including hematoxylin and eosin (HE), immunohistochemistry (IHC), and immunofluorescent (IF) staining, and compared with the gallbladder from the COVID-19 patient. The bile, as well as the serum, oropharyngeal swabs, sputum, abdominal drainage fluid, urine, and rectal swabs were consecutively negative for SARS-CoV-2 RNA. The viral host receptor angiotensin-converting enzyme 2 (ACE2) was highly expressed in gallbladder epithelial cells, and viral nucleocapsid protein (NP) was visualized in the cytoplasm of gallbladder epithelial cells. Immune cells including CD2, CD3, CD4, CD8, CD20, CD38, CD68, and MPO were positive in gangrenous gallbladder tissues without SARS-CoV-2 infection, and were relatively downregulated in SARS-CoV-2 infective gallbladder tissue. This study provided evidence of SARS-CoV-2 infection in the gallbladder and verified that the gallbladder was one of the target organs that SARS-CoV-2 could attack and damage using ACE2 as a cell receptor. Due to the immune dysregulation involved, more vigilant management and early assessment is needed for COVID-19 patients with the comorbidity of cholecystitis.

Digestive system involvement and clinical outcomes among COVID-19 patients: A retrospective cohort study from Qatar

BACKGROUND

Coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 virus most commonly presents with respiratory symptoms. While gastrointestinal (GI) manifestations either at presentation or during hospitalization are also common, their impact on clinical outcomes is controversial. Some studies have described worse outcomes in COVID-19 patients with GI symptoms, while others have shown either no association or a protective effect. There is a need for consistent standards to describe GI symptoms in COVID-19 patients and to assess their effect on clinical outcomes, including mortality and disease severity.

AIM

To investigate the prevalence of GI symptoms in hospitalized COVID-19 patients and their correlation with disease severity and clinical outcomes.

METHODS

We retrospectively reviewed 601 consecutive adult COVID-19 patients requiring hospitalization between May 1-15, 2020. GI symptoms were recorded at admission and during hospitalization. Demographic, clinical, laboratory, and treatment data were retrieved. Clinical outcomes included all-cause mortality, disease severity at presentation, need for intensive care unit (ICU) admission, development of acute respiratory distress syndrome, and need for mechanical ventilation. Multivariate logistic regression model was used to identify independent predictors of the adverse outcomes.

RESULTS

The prevalence of any GI symptom at admission was 27.1% and during hospitalization was 19.8%. The most common symptoms were nausea (98 patients), diarrhea (76 patients), vomiting (73 patients), and epigastric pain or discomfort (69 patients). There was no difference in the mortality between the two groups (6.21% vs 5.5%, P = 0.7). Patients with GI symptoms were more likely to have severe disease at presentation (33.13% vs 22.5%, P < 0.001) and prolonged hospital stay (15 d vs 14 d, P = 0.04). There was no difference in other clinical outcomes, including ICU admission, development of acute respiratory distress syndrome, or need for mechanical ventilation. Drugs associated with the development of GI symptoms during hospitalization were ribavirin (diarrhea 26.37% P < 0.001, anorexia 17.58%, P = 0.02), hydroxychloroquine (vomiting 28.52%, P = 0.009) and lopinavir/ritonavir (nausea 32.65% P = 0.049, vomiting 31.47% P = 0.004, and epigastric pain 12.65% P = 0.048). In the multivariate regression analysis, age > 65 years was associated with increased mortality risk [odds ratio (OR) 7.53, confidence interval (CI): 3.09-18.29, P < 0.001], ICU admission (OR: 1.79, CI: 1.13-2.83, P = 0.012), and need for mechanical ventilation (OR: 1.89, CI:1.94-2.99, P = 0.007). Hypertension was an independent risk factor for ICU admission (OR: 1.82, CI:1.17-2.84, P = 0.008) and need for mechanical ventilation (OR: 1.66, CI: 1.05-2.62, P = 0.028).

CONCLUSION

Patients with GI symptoms are more likely to have severe disease at presentation; however, mortality and disease progression is not different between the two groups.

Gastrointestinal manifestations and SARS-CoV-2 infection

Since COVID-19 occurrence in late 2019, intense research efforts on an unprecedented scale have focused on the study of named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry mechanisms and clinical presentations. As for other coronaviruses, SARS-CoV-2 presents with extrarespiratory clinical manifestations such as diarrhea, nausea, vomiting, and abdominal pain which highlight that the gastrointestinal (GI) system as another viral target along with the typical presentations of COVID-19 which is characterized primarily by respiratory symptoms. The digestive system is involved in many systemic functions through the gut-brain axis and systemic immunity modulation. Therefore, the GI system plays an important role in the presentation of the disease, pathogenesis, and possibly treatment outcomes. This minireview summarizes recent work to study SARS-CoV-2 infection as it relates to comorbidities, GI symptoms. This will help to strategize the priorities in understanding the impact of the virus on outcomes in various aspects.

Does Fecal-Oral Transmission of SARS-CoV-2 Due to Low Sanitation Conditions Contribute to Low Mortality Rates From COVID-19

BACKGROUND

 The novel coronavirus disease 2019 (COVID-19) is a global pandemic generated by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The primary infection site is mucosal surfaces, mainly the lungs and the intestine, where epithelial cells can be infected. COVID-19 has spread throughout the world, causing millions of deaths and hundreds of millions of confirmed infections. Despite the global spread of SARS-CoV-2, there are extreme differences between countries in mortality rates and confirmed infections.

METHODS

 Pearson correlations and a t-test were performed on data from 137 countries in order to test the correlation between number of deaths from diarrheal diseases (pre-COVID-19 pandemic data) as a marker for countries' sanitation level, and the number of confirmed COVID-19 cases and deaths per million.

RESULTS

 It was found that countries' prevalence of confirmed COVID-19 cases and deaths per million are statistically correlated with their sanitation level.

CONCLUSIONS

 The hypothesis proposed in this article is that the low mortality rates from COVID-19 in countries where the level of sanitation is low are due to fecal-oral infection of the population by SARS-CoV-2, rather than infection of the respiratory system. This hypothesis is supported by the protective effect of the low sanitation level presented in this work and the fact that lung infection by SARS-CoV-2 can cause severe pathology, while infection in the intestine generally causes minor or no symptoms.

ACE2 and Innate Immunity in the Regulation of SARS-CoV-2-Induced Acute Lung Injury: A Review

Despite the protracted battle against coronavirus acute respiratory infection (COVID-19) and the rapid evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), no specific and effective drugs have to date been reported. Angiotensin-converting enzyme 2 (ACE2) is a zinc metalloproteinase and a critical modulator of the renin-angiotensin system (RAS). In addition, ACE2 has anti-inflammatory and antifibrosis functions. ACE has become widely known in the past decade as it has been identified as the primary receptor for SARS-CoV and SARS-CoV-2, being closely associated with their infection. SARS-CoV-2 primarily targets the lung, which induces a cytokine storm by infecting alveolar cells, resulting in tissue damage and eventually severe acute respiratory syndrome. In the lung, innate immunity acts as a critical line of defense against pathogens, including SARS-CoV-2. This review aims to summarize the regulation of ACE2, and lung host cells resist SARS-CoV-2 invasion by activating innate immunity response. Finally, we discuss ACE2 as a therapeutic target, providing reference and enlightenment for the clinical treatment of COVID-19.

Multiomics: unraveling the panoramic landscapes of SARS-CoV-2 infection

In response to emerging infectious diseases, such as the recent pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), it is critical to quickly identify and understand responsible pathogens, risk factors, host immune responses, and pathogenic mechanisms at both the molecular and cellular levels. The recent development of multiomic technologies, including genomics, proteomics, metabolomics, and single-cell transcriptomics, has enabled a fast and panoramic grasp of the pathogen and the disease. Here, we systematically reviewed the major advances in the virology, immunology, and pathogenic mechanisms of SARS-CoV-2 infection that have been achieved via multiomic technologies. Based on well-established cohorts, omics-based methods can greatly enhance the mechanistic understanding of diseases, contributing to the development of new diagnostics, drugs, and vaccines for emerging infectious diseases, such as COVID-19.

Molecular Insights into SARS-CoV2-Induced Alterations of the Gut/Brain Axis

For a yet unknown reason, a substantial share of patients suffering from COVID-19 develop long-lasting neuropsychiatric symptoms ranging from cognitive deficits to mood disorders and/or an extreme fatigue. We previously reported that in non-neural cells, angiotensin-1 converting enzyme 2 (ACE2), the gene coding for the SARS-CoV2 host receptor, harbors tight co-expression links with dopa-decarboxylase (DDC), an enzyme involved in the metabolism of dopamine. Here, we mined and integrated data from distinct human expression atlases and found that, among a wide range of tissues and cells, enterocytes of the small intestine express the highest expression levels of ACE2, DDC and several key genes supporting the metabolism of neurotransmitters. Based on these results, we performed co-expression analyses on a recently published set of RNA-seq data obtained from SARS-CoV2-infected human intestinal organoids. We observed that in SARS-CoV2-infected enterocytes, ACE2 co-regulates not only with DDC but also with a specific group of genes involved in (i) the dopamine/trace amines metabolic pathway, (ii) the absorption of microbiota-derived L-DOPA and (iii) the absorption of neutral amino acids serving as precursors to neurotransmitters. We conclude that in patients with long COVID, a chronic infection and inflammation of small intestine enterocytes might be indirectly responsible for prolonged brain alterations.

Temporal Associations of the SARS-CoV-2 NP Antigen and Anti-Spike Total Ig Levels with Laboratory Parameters in a Greek Cohort of Hospitalized COVID-19 Patients

Background

The direct effect of SARS-CoV-2 on the lungs results in increased hospitalization rates of patients with pneumonia. Severe COVID-19 patients often develop ARDS which is associated with poor prognosis. Assessing risk factors for COVID-19 severity is indispensable for implementing and evaluating therapeutic interventions. We investigated the temporal associations between the SARS-CoV-2 antigen (Ag), total Immunoglobulin (Ig) levels, and several laboratory parameters in hospitalized patients with varying degrees of COVID-19 severity.

Methods

The SARS-CoV-2 nucleocapsid protein (NP) and total Ig Spike (S) protein-specific antibodies were determined for each patient with lateral flow assays through repeated sampling every two days. Hematological and biochemical parameters were evaluated at the same time points.

Results

40 Greek COVID-19 patients (31 males, 9 females) with a median age of 59.50 ± 16.21 years were enrolled in the study. The median time from symptom onset to hospitalization was 8.0 ± 4.19 days. A significant negative correlation was observed between the SARS-CoV-2 Ag and total Ig levels. The temporal correlation patterns of the SARS-CoV-2 NP Ag and anti-S total Ig levels with laboratory markers varied among patients with differing degrees of COVID-19 severity. Severe-critical cases had lower SARS-CoV-2 Ag and increased total Ig levels as compared to mild-moderate cases.

Conclusions

Distinct temporal profiles of the SARS-CoV-2 NP Ag and anti-S total Ig levels may distinguish different groups of COVID-19 severity.

Gastrointestinal Manifestations, Clinical Characteristics and Outcomes of COVID-19 in Adult and Pediatric Patients

BACKGROUND

Italy was the first country in Europe to report a SARS-CoV-2 case. Since then, the country has suffered a large number of COVID-19 infections both in adults and children. This disease has been shown to lead to different outcomes in these two groups, which often present varying symptoms and comorbidities.

AIM

Therefore, we aimed to evaluate the symptoms, comorbidities and laboratory values in adults and children.

METHODS

We present the characteristics of 1,324 adults and 563 pediatric COVID-19 Italian patients. The data was retrieved from studies published in Italy and found via PubMed and Google Scholar.

RESULTS

The virus appeared to affect adults more than children and men more than women, and to result in more severe outcomes in patients with abnormal laboratory values and a higher number of comorbidities. Adults are at higher risk for complications and death, and they usually present with fever, respiratory symptoms, cough, fatigue, diarrhea, myalgia, and/or loss of taste, smell, or appetite. Children usually have a milder disease progression and usually present with fever, cough, rhinorrhea, pharyngitis, sore throat, pneumonia, GI symptoms (diarrhea, vomiting, abdominal pain), fatigue, and dyspnea.

CONCLUSION

Our findings support early reports that showed that SARS-CoV-2 is associated with more common asymptomatic cases and milder clinical outcome in children than in adults. Acute respiratory distress syndrome and Multisystem inflammatory syndrome in children (systemic vasculitis) are the most severe disease progressions for adults and children, respectively.

COVID-19 in Liver Transplant Recipients: A Systematic Review

Liver transplant (LT) recipients are considered a vulnerable population amidst the COVID-19 pandemic. To date, available data have been heterogeneous and scarce. Therefore, we conducted a systematic literature review identifying English-language articles published in PubMed between November 2019 and 30 May 2021. We aimed to explore three areas: (1) outcome and clinical course; (2) immunological response after COVID-19 in LT recipients; and (3) vaccination response. After systematic selection, 35, 4, and 5 articles, respectively, were considered suitable for each area of analysis. Despite the heterogeneity of the reports included in this study, we found that gastrointestinal symptoms were common in LT recipients. The outcome of the LT population was not per se worse compared to the general population, although careful management of immunosuppressive therapy is required. While a complete therapy discontinuation is not encouraged, caution needs to be taken with use of mycophenolate mofetil (MMF), favoring tacrolimus (TAC) use. Although data conflicted about acquired immunity after SARS-CoV-2 infection, vaccine immunogenicity appeared to be low, suggesting that the level of surveillance should be kept high in this population.

COVID-19: a fatal case of acute liver failure associated with SARS-CoV-2 infection in pre-existing liver cirrhosis

BACKGROUND

The detection of severe acute respiratory syndrome coronavirus (SARS-CoV-2) is challenging, particularly in post-mortem human tissues. However, there is increasing evidence for viral SARS-CoV-2 manifestation in non-respiratory tissues. In this context, it is a current matter of debate, whether SARS-CoV-2 shows hepatotropism.

CASE PRESENTATION

Here, we report a case of an 88-year-old women with massive SARS-CoV-2 viremia, severe jaundice and clinical signs of an acute hepatitis, who died within a few days from an acute liver failure without showing any clinical signs of pneumonia. Autopsy revealed a severe chronic and acute liver damage with bile duct infestation by SARS-CoV-2 that was accompanied by higher expressions of angiotensin-converting enzyme-2 (ACE2), Cathepsin L and transmembrane serine protease 2 (TMPRSS2).

CONCLUSION

Our findings indicate an enhanced biliary susceptibility to viral infection with SARS-CoV-2, that might have resulted from pre-existing severe liver damage. Furthermore, our findings emphasize the differential diagnosis of coronavirus disease 2019 (COVID-19)-associated liver failure in the clinical setting of an inexplicable jaundice.