Spatial Distribution of SARS-CoV-2 Receptors and Proteases in Testicular Cells.

Coronavirus disease (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). SARS-CoV-2 RNA has been found in the human testis on occasion, but subgenomic SARS-CoV-2 and infectious SARS-CoV-2 virions have not been found. There is no direct evidence of SARS-CoV-2 infection of testicular cells. To better understand this, it is necessary to determine whether SARS-CoV-2 receptors and proteases are present in testicular cells. To overcome this limitation, we focused on elucidating with immunohistochemistry the spatial distribution of the SARS-CoV-2 receptors angiotensin-converting enzyme 2 (ACE2) and cluster of differentiation 147 (CD147), as well as their viral spike protein priming proteases, transmembrane protease serine 2 (TMPRSS2) and cathepsin L (CTSL), required for viral fusion with host cells. At the protein level, human testicular tissue expressed both receptors and proteases studied. Both ACE2 and TMPRSS2 were found in interstitial cells (endothelium, Leydig, and myoid peritubular cells) and in the seminiferous epithelium (Sertoli cells, spermatogonia, spermatocytes, and spermatids). The presence of CD147 was observed in all cell types except endothelium and peritubular cells, while CTSL was exclusively observed in Leydig, peritubular, and Sertoli cells. These findings show that the ACE2 receptor and its protease TMPRSS2 are coexpressed in all testicular cells, as well as the CD147 receptor and its protease CTSL in Leydig and Sertoli cells, indicating that testicular SARS-CoV-2 infection cannot be ruled out without further investigation.

Development of a novel human CD147 knock-in NSG mouse model to test SARS-CoV-2 viral infection.

BACKGROUND: An animal model that can mimic the SARS-CoV-2 infection in humans is critical to understanding the rapidly evolving SARS-CoV-2 virus and for development of prophylactic and therapeutic strategies to combat emerging mutants. Studies show that the spike proteins of SARS-CoV and SARS-CoV-2 bind to human angiotensin-converting enzyme 2 (hACE2, a well-recognized, functional receptor for SARS-CoV and SARS-CoV-2) to mediate viral entry. Several hACE2 transgenic (hACE2Tg) mouse models are being widely used, which are clearly invaluable. However, the hACE2Tg mouse model cannot fully explain: (1) low expression of ACE2 observed in human lung and heart, but lung or heart failure occurs frequently in severe COVID-19 patients; (2) low expression of ACE2 on immune cells, but lymphocytopenia occurs frequently in COVID-19 patients; and (3) hACE2Tg mice do not mimic the natural course of SARS-CoV-2 infection in humans. Moreover, one of most outstanding features of coronavirus infection is the diversity of receptor usage, which includes the newly proposed human CD147 (hCD147) as a possible co-receptor for SARS-CoV-2 entry. It is still debatable whether CD147 can serve as a functional receptor for SARS-CoV-2 infection or entry. RESULTS: Here we successfully generated a hCD147 knock-in mouse model (hCD147KI) in the NOD-scid IL2Rgammanull (NSG) background. In this hCD147KI-NSG mouse model, the hCD147 genetic sequence was placed downstream of the endogenous mouse promoter for mouse CD147 (mCD147), which creates an in vivo model that may better recapitulate physiological expression of hCD147 proteins at the molecular level compared to the existing and well-studied K18-hACE2-B6 (JAX) model. In addition, the hCD147KI-NSG mouse model allows further study of SARS-CoV-2 in the immunodeficiency condition which may assist our understanding of this virus in the context of high-risk populations in immunosuppressed states. Our data show (1) the human CD147 protein is expressed in various organs (including bronchiolar epithelial cells) in hCD147KI-NSG mice by immunohistochemical staining and flow cytometry; (2) hCD147KI-NSG mice are marginally sensitive to SARS-CoV-2 infection compared to WT-NSG littermates characterized by increased viral copies by qRT-PCR and moderate body weight decline compared to baseline; (3) a significant increase in leukocytes in the lungs of hCD147KI-NSG mice, compared to infected WT-NSG mice. CONCLUSIONS: hCD147KI-NSG mice are more sensitive to COVID-19 infection compared to WT-NSG mice. The hCD147KI-NSG mouse model can serve as an additional animal model for further interrogation whether CD147 serve as an independent functional receptor or accessory receptor for SARS-CoV-2 entry and immune responses.

CRISPR/Cas9 genome editing reveals an essential role for basigin in maintaining a nonkeratinized squamous epithelium in cornea.

One of the primary functions of nonkeratinized stratified squamous epithelia is to protect underlying tissues against chemical, microbial, and mechanical insult. Basigin is a transmembrane matrix metalloproteinase inducer commonly overexpressed during epithelial wound repair and cancer but whose physiological significance in normal epithelial tissue has not been fully explored. Here we used a CRISPR/Cas9 system to study the effect of basigin loss in a human cornea model of squamous epithelial differentiation. We find that epithelial cell cultures lacking basigin change shape and fail to produce a flattened squamous layer on the apical surface. This process is associated with the abnormal expression of the transcription factor SPDEF and the decreased biosynthesis of MUC16 and involucrin necessary for maintaining apical barrier function and structural integrity, respectively. Expression analysis of genes encoding tight junction proteins identified a role for basigin in promoting physiological expression of occludin and members of the claudin family. Functionally, disruption of basigin expression led to increased epithelial cell permeability as evidenced by the decrease in transepithelial electrical resistance and increase in rose bengal flux. Overall, these results suggest that basigin plays a distinct role in maintaining the normal differentiation of stratified squamous human corneal epithelium and could have potential implications to therapies targeting basigin function.

Human Basigin (CD147) Does Not Directly Interact with SARS-CoV-2 Spike Glycoprotein.

Basigin, or CD147, has been reported as a coreceptor used by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to invade host cells. Basigin also has a well-established role in Plasmodium falciparum malaria infection of human erythrocytes, where it is bound by one of the parasite's invasion ligands, reticulocyte binding protein homolog 5 (RH5). Here, we sought to validate the claim that the receptor binding domain (RBD) of SARS-CoV-2 spike glycoprotein can form a complex with basigin, using RH5-basigin as a positive control. Using recombinantly expressed proteins, size exclusion chromatography and surface plasmon resonance, we show that neither RBD nor full-length spike glycoprotein bind to recombinant human basigin (expressed in either Escherichia coli or mammalian cells). Further, polyclonal anti-basigin IgG did not block SARS-CoV-2 infection of Vero E6 cells. Given the immense interest in SARS-CoV-2 therapeutic targets to improve treatment options for those who become seriously ill with coronavirus disease 2019 (COVID-19), we would caution the inclusion of basigin in this list on the basis of its reported direct interaction with SARS-CoV-2 spike glycoprotein. IMPORTANCE Reducing the mortality and morbidity associated with COVID-19 remains a global health priority. Vaccines have proven highly effective at preventing infection and hospitalization, but efforts must continue to improve treatment options for those who still become seriously ill. Critical to these efforts is the identification of host factors that are essential to viral entry and replication. Basigin, or CD147, was previously identified as a possible therapeutic target based on the observation that it may act as a coreceptor for SARS-CoV-2, binding to the receptor binding domain of the spike protein. Here, we show that there is no direct interaction between the RBD and basigin, casting doubt on its role as a coreceptor and plausibility as a therapeutic target.

Altered expression of SARS-CoV-2 entry and processing genes by Porphyromonas gingivalis-derived lipopolysaccharide, inflammatory cytokines and prostaglandin E2 in human gingival fibroblasts.

OBJECTIVE: The aim of this in vitro study was to investigate the expression of SARS-CoV-2 entry and processing genes in human gingival fibroblasts (HGnF) following treatment with Porphyromonas gingivalis-derived lipopolysaccharide (PgLPS) or inflammatory cytokines/mediators. DESIGN: We assessed the expression of SARS-CoV-2 entry and processing genes; angiotensin-converting enzyme 2 (ACE2), cellular serine proteases transmembrane serine protease 2 (TMPRSS2), Furin, and basigin (BSG) in HGnF by real-time PCR. To further asses the contribution of PgLPS and inflammatory cytokines/mediators to proliferation and SARS-CoV-2 entry and processing gene expression, HGnF were treated with PgLPS, IL1ß, TNFα, and PGE2. RESULTS: The expression for ACE2 in HGnF was significantly elevated after PgLPS or IL1ß, TNFα, PGE2 treatment. The expression of TMPRSS2 was increased by PgLPS, IL1ß, or PGE2 while BSG was elevated by PgLPS and IL1ß. The expression of BSG and FURIN decreased after TNFα treatment. CONCLUSION: SARS-CoV-2 entry and processing genes are expressed in human gingival fibroblasts and their expressions are altered by PgLPS, IL1ß, TNFα and PGE2 treatment.

SARS-CoV-2 Entry: At the Crossroads of CD147 and ACE2.

In late 2019, the betacoronavirus SARS-CoV-2 was identified as the viral agent responsible for the coronavirus disease 2019 (COVID-19) pandemic. Coronaviruses Spike proteins are responsible for their ability to interact with host membrane receptors and different proteins have been identified as SARS-CoV-2 interactors, among which Angiotensin-converting enzyme 2 (ACE2), and Basigin2/EMMPRIN/CD147 (CD147). CD147 plays an important role in human immunodeficiency virus type 1, hepatitis C virus, hepatitis B virus, Kaposi's sarcoma-associated herpesvirus, and severe acute respiratory syndrome coronavirus infections. In particular, SARS-CoV recognizes the CD147 receptor expressed on the surface of host cells by its nucleocapsid protein binding to cyclophilin A (CyPA), a ligand for CD147. However, the involvement of CD147 in SARS-CoV-2 infection is still debated. Interference with both the function (blocking antibody) and the expression (knock down) of CD147 showed that this receptor partakes in SARS-CoV-2 infection and provided additional clues on the underlying mechanism: CD147 binding to CyPA does not play a role; CD147 regulates ACE2 levels and both receptors are affected by virus infection. Altogether, these findings suggest that CD147 is involved in SARS-CoV-2 tropism and represents a possible therapeutic target to challenge COVID-19.

Cardiorenal Tissues Express SARS-CoV-2 Entry Genes and Basigin (BSG/CD147) Increases With Age in Endothelial Cells.

Vascular and cardiovascular inflammation and thrombosis occur in patients with severe coronavirus disease-2019 (COVID-19). Advancing age is the most significant risk factor for severe COVID-19. Using transcriptomic databases, the authors found that: 1) cardiovascular tissues and endothelial cells express putative genes for severe acute respiratory syndrome coronavirus-2 infection, including angiotensin-converting enzyme 2 (ACE2) and basigin (BSG); 2) severe acute respiratory syndrome coronavirus-2 receptor pathways ACE2/transmembrane serine protease 2 and BSG/peptidylprolyl isomerase B(A) polarize to lung/epithelium and vessel/endothelium, respectively; 3) expression of host genes is relatively stable with age; and 4) notable exceptions are ACE2, which decreases with age in some tissues, and BSG, which increases with age in endothelial cells, suggesting that BSG expression in the vasculature may explain the heightened risk for severe disease with age.

Tumor markers as an entry for SARS-CoV-2 infection?

Coronavirus disease 2019 (COVID-19), the highly contagious illness caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the globe, becoming one of the most challenging public health crisis of our times. SARS-CoV-2 can cause severe disease associated with multiple organ damage. Cancer patients have a higher risk of SARS-CoV-2 infection and death. While the virus uses angiotensin-converting enzyme 2 (ACE2) as the primary entry receptor, the recent experimental and clinical findings suggest that some tumor markers, including CD147 (basigin), can provide an additional entry for SARS-CoV-2 infection through binding to the viral spike (S) protein. In the absence of specific viral drugs, blocking of CD147 might be a way to prevent virus invasion. Identifying other target proteins is of high importance as targeting the alternative receptors for SARS-CoV-2 might open up a promising avenue for the treatment of COVID-19 patients, including those who have cancer.

COVID-19 Mediated by Basigin Can Affect Male and Female Fertility.

Coronavirus disease 2019 (COVID-19) prevalence has caused many problems in society and disrupted many regular aspects of life. COVID-19 contains major structural proteins that among them, S protein can promote fusion of the viral and cellular membranes and facilitate the entry of coronavirus into the host cells. Basigin (BSG) is one of the most important receptors for COVID-19 that mediates its entry to host cells. Also, Basigin has an important role in male and female reproduction. Basigin is expressed in the uterus and plays an important role during embryo implantation and needed for successful implantation. Therefore, disruption or inhibition of Basigin causes to a weakness in embryo implantation. Therefore, if a woman or a man is infected with COVID-19, it is recommended that they do not attempt to conception until their treatment is complete. It is also recommended tests for COVID-19 be performed on infertile couples before using assisted reproductive technology (ART).

Expression of SARS-CoV-2 entry receptors in the respiratory tract of healthy individuals, smokers and asthmatics.

SARS-CoV-2 is causing a pandemic with currently > 29 million confirmed cases and > 900,000 deaths worldwide. The locations and mechanisms of virus entry into the human respiratory tract are incompletely characterized. We analyzed publicly available RNA microarray datasets for SARS-CoV-2 entry receptors and cofactors ACE2, TMPRSS2, BSG (CD147) and FURIN. We found that ACE2 and TMPRSS2 are upregulated in the airways of smokers. In asthmatics, ACE2 tended to be downregulated in nasal epithelium, and TMPRSS2 was upregulated in the bronchi. Furthermore, respiratory epithelia were negative for ACE-2 and TMPRSS2 protein expression while positive for BSG and furin, suggesting a possible alternative entry route for SARS-CoV-2.

Putative Natural History of CoViD-19.

The Severe Acute Respiratory Syndrome Corona Virus2 (SARS-CoV2) is responsible for Corona Virus Disease 2019 (CoViD-19), the pandemic that has afflicted close to two million people worldwide, and has taken the lives of over 120,000 patients since its first report in late December 2019. Per million people globally, the infection rate is close to 250 with a death rate of close to 14 (death rate average global death rate: 6.06%; for comparison, revised estimate of the 1918 influenza pandemic had an average global death rate of 5.4% [1]). About 400,000 SARS-CoV2-positive patients have been declared 'recovered', although it is not clear to date what exactly that entails. To be clear, the natural history of SARS-CoV2 infection and of the patho-physiology of CoViD-19 remains shrouded in relative confusion, in part due to the exceedingly virulent nature of the virus, as manifest by its elevated morbidity and mortality, and the fast accumulation of clinical observations and research evidence. Many pieces of a complex puzzle are emerging all at once and their organization into a coherent and cogent picture of the natural history of CoViD-19 is arduous and still wanting. Here, we discuss the recent findings in the context of the available evidence. We propose a putative prediction model of the natural history of CoViD-19. We highlight putative loci and modes of therapeutic intervention that may become beneficial preventive and treatment modalities for individuals at risk of SARS-CoV2 infection and CoViD-19 patients.

EMMPRIN/BASIGIN as a biological modulator of oral cancer and COVID-19 interaction: Novel propositions.

Extracellular matrix metalloproteinase inducer (EMMPRIN), which is also called BASIGIN/CD147, is a cell surface glycoprotein that belongs to the immunoglobulin superfamily and plays a significant role in intercellular recognition in immunology, cellular differentiation and development. Apart from ACE-2, recently EMMPRIN, has been regarded as a target for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) attachment and entry into the host cell. Since one of the routes of entry for the virus is the oral cavity, it becomes imperative to percept oral comorbidities such oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMDs) in terms of EMMPRIN as a target for SARS-CoV-2. In the present paper, it is proposed that OSCC, by the virtue of upregulation of EMMPRIN expression, increases the susceptibility to coronavirus disease (COVID-19). In turn, COVID-19 in OSCC patients causes exhaustion of EMMPRIN receptor due to binding with 'S' receptor leading to a downregulation of related carcinogenesis events. We proposed that in the ACE-2 depleted situation in OSCC, EMMPRIN receptor might get high jacked by the COVID-19 virus for the entry into the host cells. Apart from the anti-monoclonal antibody, it is recommended to explore the use of grape seed and skin containing mouthwash as an adjunct, which could also have anti EMMPRIN effects in patients with OSCC and OPMDs.

CD147 as a Target for COVID-19 Treatment: Suggested Effects of Azithromycin and Stem Cell Engagement.

The expressive number of deaths and confirmed cases of SARS-CoV-2 call for an urgent demand of effective and available drugs for COVID-19 treatment. CD147, a receptor on host cells, is a novel route for SARS-CoV-2 invasion. Thus, drugs that interfere in the spike protein/CD147 interaction or CD147 expression may inhibit viral invasion and dissemination among other cells, including in progenitor/stem cells. Studies suggest beneficial effects of azithromycin in reducing viral load of hospitalized patients, possibly interfering with ligand/CD147 receptor interactions; however, its possible effects on SARS-CoV-2 invasion has not yet been evaluated. In addition to the possible effect in invasion, azithromycin decreases the expression of some metalloproteinases (downstream to CD147), induces anti-viral responses in primary human bronchial epithelial infected with rhinovirus, decreasing viral replication and release. Moreover, resident lung progenitor/stem are extensively differentiated into myofibroblasts during pulmonary fibrosis, a complication observed in COVID-19 patients. This process, and the possible direct viral invasion of progenitor/stem cells via CD147 or ACE2, could result in the decline of these cellular stocks and failing lung repair. Clinical tests with allogeneic MSCs from healthy individuals are underway to enhance endogenous lung repair and suppress inflammation.