Identification of diphenylurea derivatives as novel endocytosis inhibitors that demonstrate broad-spectrum activity against SARS-CoV-2 and influenza A virus both in vitro and in vivo.

Rapid evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A virus (IAV) poses enormous challenge in the development of broad-spectrum antivirals that are effective against the existing and emerging viral strains. Virus entry through endocytosis represents an attractive target for drug development, as inhibition of this early infection step should block downstream infection processes, and potentially inhibit viruses sharing the same entry route. In this study, we report the identification of 1,3-diphenylurea (DPU) derivatives (DPUDs) as a new class of endocytosis inhibitors, which broadly restricted entry and replication of several SARS-CoV-2 and IAV strains. Importantly, the DPUDs did not induce any significant cytotoxicity at concentrations effective against the viral infections. Examining the uptake of cargoes specific to different endocytic pathways, we found that DPUDs majorly affected clathrin-mediated endocytosis, which both SARS-CoV-2 and IAV utilize for cellular entry. In the DPUD-treated cells, although virus binding on the cell surface was unaffected, internalization of both the viruses was drastically reduced. Since compounds similar to the DPUDs were previously reported to transport anions including chloride (Cl-) across lipid membrane and since intracellular Cl- concentration plays a critical role in regulating vesicular trafficking, we hypothesized that the observed defect in endocytosis by the DPUDs could be due to altered Cl- gradient across the cell membrane. Using in vitro assays we demonstrated that the DPUDs transported Cl- into the cell and led to intracellular Cl- accumulation, which possibly affected the endocytic machinery by perturbing intracellular Cl- homeostasis. Finally, we tested the DPUDs in mice challenged with IAV and mouse-adapted SARS-CoV-2 (MA 10). Treatment of the infected mice with the DPUDs led to remarkable body weight recovery, improved survival and significantly reduced lung viral load, highlighting their potential for development as broad-spectrum antivirals.

Brevicillin, a novel lanthipeptide from the genus Brevibacillus with antimicrobial, antifungal, and antiviral activity.

AIM: This study was aimed to determine antimicrobial and antiviral activity of a novel lanthipeptide from a Brevibacillus sp. for disinfectant application. METHODS AND RESULTS: The antimicrobial peptide (AMP) was produced by a bacterial strain AF8 identified as a member of the genus Brevibacillus representing a novel species. Whole genome sequence analysis using BAGEL identified a putative complete biosynthetic gene cluster involved in lanthipeptide synthesis. The deduced amino acid sequence of lanthipeptide named as brevicillin, showed >30% similarity with epidermin. Mass determined by MALDI-MS and Q-TOF suggested posttranslational modifications like dehydration of all Ser and Thr amino acids to yield Dha and Dhb, respectively. Amino acid composition determined upon acid hydrolysis is in agreement with core peptide sequence deduced from the putative biosynthetic gene bvrAF8. Biochemical evidence along with stability features ascertained posttranslational modifications during formation of the core peptide. The peptide showed strong activity with 99% killing of pathogens at 12 µg ml-1 within 1 minute. Interestingly, it also showed potent anti-SARS-CoV-2 activity by inhibiting ∼99% virus growth at 10 µg ml-1 in cell culture-based assay. Brevicillin did not show dermal allergic reactions in BALB/c mice. CONCLUSION: This study provides detailed description of a novel lanthipeptide and demonstrates its effective antibacterial, antifungal and anti-SARS-CoV-2 activity.

SARS-CoV-2: Recent Variants and Clinical Efficacy of Antibody-Based Therapy.

Multiple variants of SARS-CoV-2 have emerged and are now prevalent at the global level. Currently designated variants of concern (VOCs) are B.1.1.7, B1.351, P.1, B.1.617.2 variants and B.1.1.529. Possible options for VOC are urgently required as they carry mutations in the virus spike protein that allow them to spread more easily and cause more serious illness. The primary targets for most therapeutic methods against SARS-CoV-2 are the S (Spike) protein and RBD (Receptor-Binding Domain), which alter the binding to ACE2 (Angiotensin-Converting Enzyme 2). The most popular of these strategies involves the use of drug development targeting the RBD and the NTD (N-terminal domain) of the spike protein and multiple epitopes of the S protein. Various types of mutations have been observed in the RBDs of B.1.1.7, B1.351, P. and B.1.620. The incidence of RBD mutations increases the binding affinity to the ACE2 receptor. The high binding affinity of RBD and ACE2 has provided a structural basis for future evaluation of antibodies and drug development. Here we discuss the variants of SARS-CoV-2 and recent updates on the clinical evaluation of antibody-based treatment options. Presently, most of the antibody-based treatments have been effective in patients with SARS-CoV-2. However, there are still significant challenges in verifying independence, and the need for further clinical evaluation.

A novel plant lectin, NTL-125, interferes with SARS-CoV-2 interaction with hACE2.

COVID-19 caused by SARS-CoV-2 virus has had profound impact on the world in the past two years. Intense research is going on to find effective drugs to combat the disease. Over the past year several vaccines were approved for immunization. But SARS-CoV-2 being an RNA virus is continuously mutating to generate new variants, some of which develop features of immune escape. This raised serious doubts over the long-term efficacy of the vaccines. We have identified a unique mannose binding plant lectin from Narcissus tazetta bulb, NTL-125, which effectively inhibits SARS-CoV-2 replication in Vero-E6 cell line. In silico docking studies revealed that NTL-125 has strong affinity to viral Spike RBD protein, preventing it from attaching to hACE2 receptor, the gateway to cellular entry. Binding analyses revealed that all the mutant variants of Spike protein also have stronger affinity for NTL-125 than hACE2. The unique α-helical tail of NTL-125 plays most important role in binding to RBD of Spike. NTL-125 also interacts effectively with some glycan moieties of S-protein in addition to amino acid residues adding to the binding strength. Thus, NTL-125 is a highly potential antiviral compound of natural origin against SARS-CoV-2 and may serve as an important therapeutic for management of COVID-19.

Chlorhexidine: An effective anticovid mouth rinse.

CONTEXT: Dentists across the globe are witnessing a completely unforeseen and uncertain professional situation during these times of COVID-19 pandemic. There is conflicting evidence regarding the effectiveness of routinely used mouthwashes and especially Chlorhexidine, to reduce the viral load in oral cavity and the aerosols during oral procedures. AIMS: Comparative evaluation of the effectiveness of the current 'gold standard' chlorhexidine and povidone iodine as a control agent, through an in-vitro analysis. SETTINGS AND DESIGN: In-vitro laboratory analysis. METHODS AND MATERIAL: All the experiments for analysis of antiviral efficacy of chlorhexidine digluconate (2%)and povidone iodine(1%), against SARS-CoV-2 virus were performed in the BSL3 facility at the Council of Scientific and Industrial Research-Institute of Microbial Technology, using the VeroE6 cell lines. The analysis of the virus inactivation was based on quantification of viral RNA (Cycle threshold (Ct) profile) present in the culture supernatant using Real-Time Quantitative Reverse Transcription PCR (qRT-PCR). STATISTICAL ANALYSIS USED: Descriptive analysis (Statistical package for social sciences (SPSS Inc., Chicago, IL, version 15.0 for Windows). RESULTS: Chlorhexidine digluconate in 0.2% concentration inactivated more than 99.9% of SARS CoV 2 virus, in minimal contact time of 30 seconds, which was considered better efficacy than povidone-iodine utilized for 30 and 60 seconds. Subtle differences were observed in the activity of both the compounds in terms of percent inactivation of virus, though a greater relative change in Ct values was observed for chlorhexidine. CONCLUSIONS: Within the limitations of the present study, it can be concluded that Chlorhexidine digluconate in 0.2% concentration inactivated SARS CoV 2 in minimal contact time i.e 30 secs, however both compounds tested i.e Chlorhexidine and povidone-iodine were found to have antiviral activity against SARS CoV2 virus.