Alpha-1-antitrypsin antagonizes COVID-19: a review of the epidemiology, molecular mechanisms, and clinical evidence.

Alpha-1-antitrypsin (AAT), a serine protease inhibitor (serpin), is increasingly recognized to inhibit SARS-CoV-2 infection and counter many of the pathogenic mechanisms of COVID-19. Herein, we reviewed the epidemiologic evidence, the molecular mechanisms, and the clinical evidence that support this paradigm. As background to our discussion, we first examined the basic mechanism of SARS-CoV-2 infection and contend that despite the availability of vaccines and anti-viral agents, COVID-19 remains problematic due to viral evolution. We next underscored that measures to prevent severe COVID-19 currently exists but teeters on a balance and that current treatment for severe COVID-19 remains grossly suboptimal. We then reviewed the epidemiologic and clinical evidence that AAT deficiency increases risk of COVID-19 infection and of more severe disease, and the experimental evidence that AAT inhibits cell surface transmembrane protease 2 (TMPRSS2) - a host serine protease required for SARS-CoV-2 entry into cells - and that this inhibition may be augmented by heparin. We also elaborated on the panoply of other activities of AAT (and heparin) that could mitigate severity of COVID-19. Finally, we evaluated the available clinical evidence for AAT treatment of COVID-19.

Curcumin as a potential multiple-target inhibitor against SARS-CoV-2 Infection: A detailed interaction study using quantum chemical calculations

Curcumin is one of the important naturally occurring compounds having several medicinal properties such as: antiviral, antioxidant, antifibrotic, antineoplastic as well as anti-inflammatory. SARS-CoV-2 has emerged as inf-ectious virus, which severely infected a large number of people all over the world. Many efforts have been made to prepare novel antiviral compound, but it is still challenging. Naturally occurring compound, curcumin, can be used as an alternative to antiviral compound against SARS-CoV-2. Its effect against SARS-CoV-2 is already highlighted in the literature. But the quantitative study of its interaction with various precursors of SARS-CoV-2 is not reported till date. This paper reports the interaction of curcumin with angiotensin-convert-ing enzyme2, transmembrane serine protease 2, 3-chymotrypsin-like protease and papain-like protease through molecular docking and quantum chemistry calculations to achieve quantitative understanding of underlying interactions. Here the conformational flexibility of curcumin is also highlighted, which helps it to accommodate in the four different docking sites. The study has been performed using calculations of geometrical parameter, atomic charge, electron density, Laplacian of electron density, dipole moment and the energy gap between highest occupied and lowest unoccupied molecular orbitals. The non--covalentinteraction (NCI) analysis is performed to visualize the weak inter-action present in the active sites. Combinedly molecular docking and detailed quantum chemistry calculations revealed that curcumin can be adopted as a potential multiple-target inhibitor against SARS-CoV-2.

Harnessing and bioprospecting botanical-based herbal medicines against potential drug targets for COVID-19: a review coupled molecular docking studies.

Since the end of February 2020, the world has come to a standstill due to the virus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2). Since then, the global scientific community has explored various remedies and treatments against this virus, including natural products that have always been a choice because of their many benefits. Various known phytochemicals are well documented for their antiviral properties. Research is being carried out to discover new natural plant products or existing ones as a treatment measure for this disease. The three important targets in this regard are-papain like protease (PLpro), spike protein, and 3 chymotrypsin like proteases (3CLpro). Various docking studies are also being elucidated to identify the phytochemicals that modulate crucial proteins of the virus. The paper is simultaneously a comprehensive review that covers recent advances in the domain of the effect of various botanically derived natural products as an alternative treatment approach against Coronavirus Disease 2019 (COVID-19). Furthermore, the docking analyses revealed that rutin (inhibitor of the major protease of SARS-CoV-2), gallocatechin (e.g., interacting with 03 hydrogen bonds with a spike-like protein), lycorine (showing the best binding affinity with amino acids GLN498, THR500 and GLY446 of the spike-like protein), and quercetrin (inhabiting at its residues ASP216, PHE219, and ILE259) are promising inhibitors of SARS­CoV­2.Communicated by Ramaswamy H. Sarma.

Ferrocenoyl-substituted quinolinone and coumarin as organometallic inhibitors of SARS-CoV-2 3CLpro main protease.

The 3-chymotrypsin-like protease 3CLpro from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a potential target for antiviral drug development. In this work, three organometallic ferrocene-modified quinolinones and coumarins were compared to their benzoic acid ester analogues with regard to inhibition of 3CLpro using an HPLC-based assay with a 15mer model peptide as the substrate. In contrast to FRET-based assays, this allows direct identification of interference of buffer constituents with the inhibitors, as demonstrated by the complete abolishment of ebselen inhibitory activity in the presence of dithiothreitol as a redox protectant. The presence of the organometallic ferrocene moiety significantly increased the stability of the title compounds towards hydrolysis. Among the studied compounds, 4-ferrocenyloxy-1-methyl-quinol-2-one was identified as the most stable and potent inhibitor candidate. IC50 values determined for ebselen and this sandwich complex compound are (0.40 ± 0.07) and (2.32 ± 0.21) µM, respectively.

Inhibition of Listeria Monocytogenes HtrA Protease with Camostat, Gabexate and Nafamostat Mesylates and the Binding Mode of the Inhibitors.

In many bacteria, the High Temperature requirement A (HtrA) protein functions as a chaperone and protease. HtrA is an important factor in stress tolerance and plays a significant role in the virulence of several pathogenic bacteria. Camostat, gabexate and nafamostat mesylates are serine protease inhibitors and have recently shown a great impact in the inhibition studies of SARS-CoV2. In this study, the inhibition of Listeria monocytogenes HtrA (LmHtrA) protease activity was analysed using these three inhibitors. The cleavage assay, using human fibrinogen and casein as substrates, revealed that the three inhibitors effectively inhibit the protease activity of LmHtrA. The agar plate assay and spectrophotometric analysis concluded that the inhibition of nafamostat (IC50 value of 6.6 ± 0.4 µM) is more effective compared to the other two inhibitors. Previous studies revealed that at the active site of the protease, these inhibitors are hydrolysed and one of the hydrolysates is covalently bound to the active site serine. To understand the mode of binding of these inhibitors at the active site of LmHtrA, docking of the inhibitors followed by molecular dynamics simulations were carried out. Analysis of the LmHtrA-inhibitor complex structures revealed that the covalently bound inhibitor is unable to occupy the S1 pocket of the LmHtrA which is in contrast to the previously determined camostat and nafamostat complex structures. This observation provides the first glimpse of the substrate specificity of LmHtrA which is not known. The obtained results also suggest that the development of novel inhibitors of LmHtrA and its homologs with active site architecture similar to LmHtrA can be pursued with suitable modification of these inhibitors. To date, only a very few studies have been carried out on identifying the inhibitors of HtrA proteolytic activity.

COVID-19 and Diarylamidines: The Parasitic Connection.

As emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants (Omicron) continue to outpace and negate combinatorial vaccines and monoclonal antibody therapies targeting the spike protein (S) receptor binding domain (RBD), the appetite for developing similar COVID-19 treatments has significantly diminished, with the attention of the scientific community switching to long COVID treatments. However, treatments that reduce the risk of "post-COVID-19 syndrome" and associated sequelae remain in their infancy, particularly as no established criteria for diagnosis currently exist. Thus, alternative therapies that reduce infection and prevent the broad range of symptoms associated with 'post-COVID-19 syndrome' require investigation. This review begins with an overview of the parasitic-diarylamidine connection, followed by the renin-angiotensin system (RAS) and associated angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSSR2) involved in SARS-CoV-2 infection. Subsequently, the ability of diarylamidines to inhibit S-protein binding and various membrane serine proteases associated with SARS-CoV-2 and parasitic infections are discussed. Finally, the roles of diarylamidines (primarily DIZE) in vaccine efficacy, epigenetics, and the potential amelioration of long COVID sequelae are highlighted.

Deciphering the Potential Therapeutic Intervention Points of 2019-nCoV: A Pharmacological Perspective

The emerging and re-emergence of viral outbreaks in the history of mankind has always pose severe global intimidation to public health and economy. The debilitating effects of 2019-nCoV (2019 novel coronavirus) outbreak has swiftly spread worldwide due to its highly contagious nature with severe risk of respiratory tract infections and higher mortality rate, necessitating the urgent need for the production of effective vaccine and potential therapeutic agents. The active evolution of SARS-CoV-2 strain in different population and environment strive immense challenge against anti-viral therapeutic development based on viral pathogenicity. The potential FDA drugs are evaluated based on their known safety and efficacy with exceptional pharmacokinetic profiles for the treatment of nCoV-2019. Existing knowledge related to MERS-CoV and SARS-CoV epidemic has provided a better understanding to explore purposeful therapeutics strategies against novel coronavirus disease (COVID-19). To limited extend, the ongoing promising and hopeful treatments includes convalescent plasma therapy, remdesivir, lopinavir/ritonavir, ACE inhibitors, TMPRSS2 inhibitors, hydroxychloroquine, interferon, ribavirin, tocilizumab, and corticosteroids however clinical efficacy of some of them need to be validated in randomized clinical trials (RCTs). The global struggle to make a protected and successful Coronavirus immunization is finally proving to be fruitful. Although challenges such as strain variation resistant, possible side effects, adequate supply of vaccines to all countries and limited availability of second dose still diverting the option of possible efficacious therapeutics strategies to work alongside with vaccine development with improved efficacy and safety profile. This review is focused on the potential advancement in therapeutic approaches with possible repurposing of the available drugs and explores the current status of available vaccines with hope that these strategies found to be cogent in controlling SARS-CoV-2 outbreak. © 2022, The Running Line. All rights reserved.

SARS-CoV-2 infection and smoking: What is the association? A brief review.

Susceptibility to severe illness from COVID-19 is anticipated to be associated with cigarette smoking as it aggravates the risk of cardiovascular and respiratory illness, including infections. This is particularly important with the advent of a new strain of coronaviruses, the severe acute respiratory syndrome coronavirus (SARS-CoV-2) that has led to the present pandemic, coronavirus disease 2019 (COVID-19). Although, the effects of smoking on COVID-19 are less described and controversial, we presume a link between smoking and COVID-19. Smoking has been shown to enhance the expression of the angiotensin-converting enzyme-2 (ACE-2) and transmembrane serine protease 2 (TMPRSS2) key entry genes utilized by SARS-CoV-2 to infect cells and induce a 'cytokine storm', which further increases the severity of COVID-19 clinical course. Nevertheless, the impact of smoking on ACE-2 and TMPRSS2 receptors expression remains paradoxical. Thus, further research is necessary to unravel the association between smoking and COVID-19 and to pursue the development of potential novel therapies that are able to constrain the morbidity and mortality provoked by this infectious disease. Herein we present a brief overview of the current knowledge on the correlation between smoking and the expression of SARS-CoV-2 key entry genes, clinical manifestations, and disease progression.

TMPRSS2 Is Essential for SARS-CoV-2 Beta and Omicron Infection.

The COVID-19 pandemic remains a global health threat and novel antiviral strategies are urgently needed. SARS-CoV-2 employs the cellular serine protease TMPRSS2 for entry into lung cells, and TMPRSS2 inhibitors are being developed for COVID-19 therapy. However, the SARS-CoV-2 Omicron variant, which currently dominates the pandemic, prefers the endo/lysosomal cysteine protease cathepsin L over TMPRSS2 for cell entry, raising doubts as to whether TMPRSS2 inhibitors would be suitable for the treatment of patients infected with the Omicron variant. Nevertheless, the contribution of TMPRSS2 to the spread of SARS-CoV-2 in the infected host is largely unclear. In this study, we show that the loss of TMPRSS2 strongly reduced the replication of the Beta variant in the nose, trachea and lung of C57BL/6 mice, and protected the animals from weight loss and disease. The infection of mice with the Omicron variant did not cause disease, as expected, but again, TMPRSS2 was essential for efficient viral spread in the upper and lower respiratory tract. These results identify the key role of TMPRSS2 in SARS-CoV-2 Beta and Omicron infection, and highlight TMPRSS2 as an attractive target for antiviral intervention.

A randomized, placebo-controlled pilot study of upamostat, a host-directed serine protease inhibitor, for outpatient treatment of COVID-19.

OBJECTIVES: We performed a pilot study of upamostat, a serine protease inhibitor, in outpatients with symptomatic COVID-19 before a pivotal trial. METHODS: SARS-CoV-2 patients with ≥2 moderate-severe symptoms onset within 5 days were randomized to oral upamostat 200 or 400 mg or placebo daily for 14 days. Patients completed COVID-19 symptom questionnaires daily for 28 days, then thrice weekly for 4 weeks, and underwent physical and laboratory examinations periodically. RESULTS: A total of 61 patients enrolled of which 20 received a placebo or upamostat 200 mg daily; 21 received upamostat 400 mg daily. Treatment was well tolerated; only one patient (upamostat 400) reported a drug-related adverse event, mild skin rash; no patient discontinued owing to a drug-related adverse event. The median time to a sustained recovery from severe symptoms was 8, 4, and 3 days for the three treatment groups, respectively. New severe symptoms developed in 20% of the placebo group vs 2.4% in the combined upamostat groups, (P = 0.036). Three placebo patients (15%) versus no upamostat patients were hospitalized for worsening COVID (P= 0.03). The mean d-dimer level remained constant in placebo patients but decreased by 38% and 48% in upamostat 200 and 400 patients, respectively. CONCLUSION: Upamostat was well tolerated, shortened recovery time, and decreased new severe symptoms and hospitalization.

Autoimmunity, COVID-19 Omicron Variant, and Olfactory Dysfunction: A Literature Review.

Smelling is a critical sense utilized daily. Consequently, smelling impairment or anosmia may lead to a reduction in life quality. Systemic diseases and particular autoimmune conditions can impair olfactory function; among others are Systemic Lupus Erythematosus, Sjögren Syndrome, and Rheumatoid Arthritis. Interactions between the olfactory process and the immune systems cause this phenomenon. Alongside autoimmune conditions, in the recent COVID-19 pandemic, anosmia was also described as a prevalent infection symptom. Nevertheless, the occurrence of anosmia is significantly less common in Omicron-infected patients. Several theories have been proposed to explain this phenomenon. One possibility is that the Omicron variant preferentially enters host cells via endocytosis, rather than plasma cell membrane fusion. This endosomal pathway is less dependent on the activation of Transmembrane serine protease 2 (TMPRSS2), expressed at the olfactory epithelium. As a result, the Omicron variant may have reduced efficiency in penetrating the olfactory epithelium, leading to a lower prevalence of anosmia. Furthermore, olfactory changes are known to be associated with inflammatory conditions. The Omicron variant elicits a less robust autoimmune and inflammatory response, believed to reduce the probability of anosmia. This review elaborates on the commonalities and differences in autoimmune and COVID-19 omicron-associated anosmia.

Liver injury in COVID-19: A minireview.

Coronavirus disease 2019 (COVID-19), caused by infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has escalated into a global tragedy afflicting human health, life, and social governance. Through the increasing depth of research and a better understanding of this disease, it has been ascertained that, in addition to the lungs, SARS-CoV-2 can also induce injuries to other organs including the liver. Liver injury is a common clinical manifestation of COVID-19, particularly in severe cases, and is often associated with a poorer prognosis and higher severity of COVID-19. This review focuses on the general existing information on liver injury caused by COVID-19, including risk factors and subpopulations of liver injury in COVID-19, the association between preexisting liver diseases and the severity of COVID-19, and the potential mechanisms by which SARS-CoV-2 affects the liver. This review may provide some useful information for the development of therapeutic and preventive strategies for COVID-19-associated liver injury.

Association of androgenetic alopecia with a more severe form of COVID-19 infection.

BACKGROUND: Individual susceptibility to develop acute respiratory distress syndrome is related to age and most frequent comorbidities. So far, it is known that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) primarily infects the type II pneumocytes in humans, with the help of transmembrane serine protease type 2 (TMPRSS2). Up to now, the only known transcriptional promoters of genes coding TMPRSS2 are androgenic. Theoretically, the elevated level of androgens or androgen receptors would lead to a higher expression of TMPRSS2 and a higher level of viremia as a consequence. AIM: The aim of our research was to indirectly investigate if the severity of SARS-CoV-2 infection is dependent on the expression of androgen receptors. METHODS: This observational study analysed male patients hospitalized for SARS-CoV-2 infection with respect to the length of hospitalisation, the outcome of the disease, the type of necessary oxygen support and the presence of comorbidities and hairiness. In hairiness estimation, we used an adapted version of the Hamilton-Norwood scale and the presence of the Gabrin sign. RESULTS: In total, 208 patients were enrolled in the study. There were statistically significant differences comparing the average age of patients with the different types of alopecia when groups were divided according to the presence of the Gabrin sign (t = 4.958, p > 0.01). The outcomes and the type of needed minimal oxygen support, compared with the type of alopecia in the case of Gabrin + / - classification showed a statistically significant difference in the outcome of the disease (p = 0.027). There were no statistically significant differences in the distribution of comorbidities among alopecia groups, but hypertension was related to poor COVID-19 prognosis. CONCLUSION: Our findings suggest that the Gabrin sign and hypertension are related to a poor COVID-19 prognosis.

Digestive system infection by SARS­CoV­2: Entry mechanism, clinical symptoms and expression of major receptors (Review).

Besides causing severe acute respiratory syndrome (SARS), SARS­coronavirus 2 (SARS­CoV­2) also harms the digestive system. Given the appearance of numerous cases of SARS­CoV­2, it has been demonstrated that SARS­CoV­2 is able to harm target organs such as the gastrointestinal tract, liver and pancreas, and either worsen the condition of patients with basic digestive illnesses or make their prognosis poor. According to several previously published studies, angiotensin­converting enzyme II (ACE2) and transmembrane serine protease II (TMPRSS2) are expressed either singly or in combination in the digestive system and in other regions of the human body. In order to change the viral conformation, create a fusion hole and release viral RNA into the host cell for replication and transcription, SARS­CoV­2 is capable of binding to these two proteins through the spike protein on its surface. As a result, the body experiences an immune reaction and an inflammatory reaction, which may lead to nausea, diarrhea, abdominal pain and even gastrointestinal bleeding, elevated levels of liver enzymes, acute liver injury, pancreatitis and other serious lesions. In order to provide possible strategies for the clinical diagnosis and treatment of digestive system diseases during the COVID­19 pandemic, the molecular structure of SARS­CoV­2 and the mechanism via which SARS­CoV­2 enters the human body through ACE2 and TMPRSS2 were discussed in the present review, and the clinical manifestations of SARS­CoV­2 infection in the digestive system were also summarized. Finally, the expression characteristics of ACE2 and TMPRSS2 in the main target organs of the digestive system were described.

Thymus vulgaris, a natural pharmacy against COVID-19: A molecular review.

Introduction: A worldwide pandemic infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of a deadly disease called COVID-19. Interaction of the virus and the Angiotensin converting-enzyme 2 (ACE2) receptor leads to an inflammatory-induced tissue damage. Thymus vulgaris L. (TvL) is a plant with a long history in traditional medicine that has antimicrobial, antiseptic, and antiviral properties. Thymol and Carvacrol are two important biological components in Thyme that have anti-inflammatory, antioxidant, and immunomodulatory properties. This study is a molecular review on the potential effects of TvL and its active compounds on SARS-COV2 infection. Method: This is a narrative review in which using PubMed, Scopus, ISI, Cochrane, ScienceDirect, Google scholar, and Arxiv preprint databases, the molecular mechanisms of therapeutic and protective effects of TvL and its active compounds have been discussed regarding the molecular pathogenesis in COVID-19. Results: Thyme could suppress TNF-alpha, IL-6, and other inflammatory cytokines. It also enhances the anti-inflammatory cytokines like TGF-beta and IL-10. Thyme extract acts also as an inhibitor of cytokines IL-1-beta and IL-8, at both mRNA and protein levels. Thymol may also control the progression of neuro-inflammation toward neurological disease by reducing some factors. Thyme and its active ingredients, especially Thymol and Carvacrol, have also positive effects on the renin-angiotensin system (RAS) and intestinal microbiota. Conclusions: Accordingly, TvL and its bioactive components may prevent COVID-19 complications and has a potential protective role against the deleterious consequences of the disease.

Potential of green tea EGCG in neutralizing SARS-CoV-2 Omicron variant with greater tropism toward the upper respiratory tract.

Background: COVID-19 due to SARS-CoV-2 infection has had an enormous adverse impact on global public health. As the COVID-19 pandemic evolves, the WHO declared several variants of concern (VOCs), including Alpha, Beta, Gamma, Delta, and Omicron. Compared with earlier variants, Omicron, now a dominant lineage, exhibits characteristics of enhanced transmissibility, tropism shift toward the upper respiratory tract, and attenuated disease severity. The robust transmission of Omicron despite attenuated disease severity still poses a great challenge for pandemic control. Under this circumstance, its tropism shift may be utilized for discovering effective preventive approaches. Scope and approach: This review aims to estimate the potential of green tea epigallocatechin gallate (EGCG), the most potent antiviral catechin, in neutralizing SARS-CoV-2 Omicron variant, based on current knowledge concerning EGCG distribution in tissues and Omicron tropism. Key findings and conclusions: EGCG has a low bioavailability. Plasma EGCG levels are in the range of submicromolar concentrations following green tea drinking, or reach at most low µM concentrations after pharmacological intervention. Nonetheless, its levels in the upper respiratory tract could reach concentrations as high as tens or even hundreds of µM following green tea consumption or pharmacological intervention. An approach for delivering sufficiently high concentrations of EGCG in the pharynx has been developed. Convincing data have demonstrated that EGCG at tens to hundreds of µM can dramatically neutralize SARS-CoV-2 and effectively eliminate SARS-CoV-2-induced cytopathic effects and plaque formation. Thus, EGCG, which exhibits hyperaccumulation in the upper respiratory tract, deserves closer investigation as an antiviral in the current global battle against COVID-19, given Omicron's greater tropism toward the upper respiratory tract.

Clinical Trial Subgroup Analyses to Investigate Clinical and Immunological Outcomes of Convalescent Plasma Therapy in Severe COVID-19.

Objective: To assess the clinical and immunological benefits of passive immunization using convalescent plasma therapy (CPT). Materials and Methods: A series of subclass analyses were performed on the previously published outcome data and accompanying clinical metadata from a completed randomized controlled trial (RCT) (Clinical Trial Registry of India, number CTRI/2020/05/025209). The subclass analyses were performed on the outcome data and accompanying clinical metadata from a completed RCT (patient recruitment between May 15, 2020 and October 31, 2020). Data on the plasma abundance of a large panel of cytokines from the same cohort of patients were also used to characterize the heterogeneity of the putative anti-inflammatory function of convalescent plasma (CP) in addition to passively providing neutralizing antibodies. Results: Although the primary clinical outcomes were not significantly different in the RCT across all age groups, significant immediate mitigation of hypoxia, reduction in hospital stay, and significant survival benefit were registered in younger (<67 years in our cohort) patients with severe coronavirus disease 2019 and acute respiratory distress syndrome on receiving CPT. In addition to neutralizing the antibody content of CP, its anti-inflammatory proteome, by attenuation of the systemic cytokine deluge, significantly contributed to the clinical benefits of CPT. Conclusion: Subgroup analyses revealed that clinical benefits of CPT in severe coronavirus disease 2019 are linked to the anti-inflammatory protein content of CP apart from the anti-severe acute respiratory syndrome coronavirus 2 neutralizing antibody content.

Single domain antibodies derived from ancient animals as broadly neutralizing agents for SARS-CoV-2 and other coronaviruses.

With severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as an emergent human virus since December 2019, the world population is susceptible to coronavirus disease 2019 (COVID-19). SARS-CoV-2 has higher transmissibility than the previous coronaviruses, associated by the ribonucleic acid (RNA) virus nature with high mutation rate, caused SARS-CoV-2 variants to arise while circulating worldwide. Neutralizing antibodies are identified as immediate and direct-acting therapeutic against COVID-19. Single-domain antibodies (sdAbs), as small biomolecules with non-complex structure and intrinsic stability, can acquire antigen-binding capabilities comparable to conventional antibodies, which serve as an attractive neutralizing solution. SARS-CoV-2 spike protein attaches to human angiotensin-converting enzyme 2 (ACE2) receptor on lung epithelial cells to initiate viral infection, serves as potential therapeutic target. sdAbs have shown broad neutralization towards SARS-CoV-2 with various mutations, effectively stop and prevent infection while efficiently block mutational escape. In addition, sdAbs can be developed into multivalent antibodies or inhaled biotherapeutics against COVID-19.

TMPRSS13 zymogen activation, surface localization, and shedding is regulated by proteolytic cleavage within the non-catalytic stem region.

TMPRSS13 is a member of the type II transmembrane serine protease (TTSP) family. Here we characterize a novel post-translational mechanism important for TMPRSS13 function: proteolytic cleavage within the extracellular TMPRSS13 stem region located between the transmembrane domain and the first site of N-linked glycosylation at asparagine (N)-250 in the scavenger receptor cysteine rich (SRCR) domain. Importantly, the catalytic competence of TMPRSS13 is essential for stem region cleavage, suggesting an autonomous mechanism of action. Site-directed mutagenesis of the 10 basic amino acids (four arginine and six lysine residues) in this region abrogated zymogen activation and catalytic activity of TMPRSS13, as well as phosphorylation, cell surface expression, and shedding. Mutation analysis of individual arginine residues identified R223, a residue located between the low-density lipoprotein receptor class A domain and the SRCR domain, as important for stem region cleavage. Mutation of R223 causes a reduction in the aforementioned functional processing steps of TMPRSS13. These data provide further insight into the roles of different post-translational modifications as regulators of the function and localization of TMPRSS13. Additionally, the data suggest the presence of complex interconnected regulatory mechanisms that may serve to ensure the proper levels of cell-surface and pericellular TMPRSS13-mediated proteolysis under homeostatic conditions.

Association of alcohol intake and female gender with high expression of TMPRSS2 in tongue as potential risk for SARS-CoV-2 infection.

COVID-19 is pandemic since 2020 and further information is necessary on the risk factors associated with the infection of SARS-CoV-2. As an entry mechanism, SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as receptor and transmembrane serine protease 2 (TMPRSS2) to activate fusion with host plasma membrane. Because dysgeusia is an early symptom of COVID-19, we here studied the expression of ACE2 and TMPRSS2 in the tongue and the associated tissues of mice and humans with immunohistochemistry and immunoblot analysis. ACE2 expression was low in the human tongue but was observed in the squamous epithelium, perineurium, arterial wall, salivary glands as well as taste buds. In contrast, mice showed high expression. In sharp contrast, TMPRSS2 expression was high in all the cells mentioned above in humans but relatively low in mice except for salivary glands. We then performed semi-quantitation of immunohistochemistry data of human ACE2 and TMPRSS2 and analyzed for age, sex, alcohol intake, and smoking habit with logistic regression analysis. We found that alcohol intake and female gender were the significant risk factors for increasing TMPRSS2 expression. In conclusion, TMPRSS2 is an important factor to be considered regarding SARS-CoV-2 entry and amplification in the oral cavity, which is promoted through drinking habit.