An insight into the simulation directed understanding of the mechanism in SARS CoV-2 N-CTD, dimer integrity, and RNA-binding: Identifying potential antiviral inhibitors

Bitter taste receptors establish a stable binding affinity with the SARS-CoV-2-spike 1 protein akin to ACE2

COVID-19 is caused by the highly contagious SARS-CoV-2 virus, which originated in Wuhan, China, resulting in the highest worldwide mortality rate. Gustatory dysfunction is common among individuals infected with the Wild-type Wuhan strain. However, there are no reported cases of gustatory dysfunction among patients infected with the mutant delta variant. The reason behind this remains elusive to date. This in-silico-based study aims to unravel this clinical factor by evaluating the overall binding affinity of predominant bitter taste receptors associated with gustatory function (T2R-4, 10, 14, 19, 31, 38, 43, and 46) with the Receptor Binding Domain (RBD) of spike 1 (S1) protein of Wuhan (Wild)/delta-SARS-CoV-2 (mut1-T478K; mut2-E484K) variants. Based on docking and MM/PBSA free binding energy scores, the Wild RBD showed a stronger interaction with T2R-46 compared to the ACE2 protein. However, both delta variant mutants (mut1 and mut2) could not establish a stronger binding affinity with bitter taste receptor proteins, except for T2R-43 against mut1. In conclusion, the delta variants could not establish a better binding affinity with bitter taste receptors, contradicting the Wild variant that determines the severity of gustatory dysfunction among patients exposed to the delta and Wild SARS-CoV-2 variants. The study's inference also proposes T2R-46 as an alternate binding receptor target for RBD-S1 of Wild SARS-CoV-2, augmenting its virulence in all functional organs with compromised α-gustducin interaction and bitter sensitization. This in-silico-based study needs further wet-lab-based validation for a better understanding of the role of T2R-46-based viral entry in the human host.Communicated by Ramaswamy H. Sarma.

Suramin inhibits SARS-CoV-2 nucleocapsid phosphoprotein genome packaging function

The coronavirus disease 2019 (COVID-19) pandemic is fading, however its etiologic agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues posing - despite the availability of licensed vaccines - a global health threat, due to the potential emergence of vaccine-resistant SARS-CoV-2 variants. This makes the development of new drugs against COVID-19 a persistent urgency and sets as research priority the validation of novel therapeutic targets within the SARS-CoV-2 proteome. Among these, a promising one is the SARS-CoV-2 nucleocapsid (N) phosphoprotein, a major structural component of the virion with indispensable role in packaging the viral genome into a ribonucleoprotein (RNP) complex, which also contributes to SARS-CoV-2 innate immune evasion by inhibiting the host cell type-I interferon (IFN-I) response. By combining miniaturized differential scanning fluorimetry with microscale thermophoresis, we found that the 100-year-old drug Suramin interacts with SARS-CoV-2 N-terminal domain (NTD) and C-terminal domain (CTD), thereby inhibiting their single-stranded RNA (ssRNA) binding function with low-micromolar Kd and IC50 values. Molecular docking suggests that Suramin interacts with basic NTD cleft and CTD dimer interface groove, highlighting three potentially druggable ssRNA binding sites. Electron microscopy shows that Suramin inhibits the formation in vitro of RNP complex-like condensates by SARS-CoV-2 N with a synthetic ssRNA. In a dose-dependent manner, Suramin also reduced SARS-CoV-2-induced cytopathic effect on Vero E6 and Calu-3 cells, partially reverting the SARS-CoV-2 N-inhibited IFN-I production in 293T cells. Our findings indicate that Suramin inhibits SARS-CoV-2 replication by hampering viral genome packaging, thereby representing a starting model for design of new COVID-19 antivirals.

COVID-19–associated rhino-orbital-cerebral mucormycosis: A systematic review, meta-analysis, and meta-regression analysis

BACKGROUND:

Till now, no meta-analysis is available to address the clinical profile, risk factors, different interventions, and outcomes among COVID-19–associated rhino-orbito-cerebral mucormycosis (C-ROCM) cases.

MATERIALS AND METHODS:

Eight literature databases were screened using appropriate keywords from November 1, 2019, to June 30, 2021. The objectives were to analyze the clinical and microbiological profile, risk factor/comorbidity, intervention, and outcome. “R-metafor package” was used for analysis.

RESULTS:

A total of 23 studies were included. The mean age of presentation of C-ROCM was 54.6 years. The most common presentation was ptosis (72.7%), lid edema (60.6%), proptosis (60.6%), ophthalmoplegia (57.3%), loss of vision (53.7%), facial edema (34.7%), and nasal-blockage (11.8%). Evidence of intracranial spread was seen in 42.8% of cases. Rhizopus was the most common fungus (57.1%) isolated in fungal culture. Among C-ROCM patients, diabetes was the commonest comorbid condition, and the use of corticosteroids related to COVID-19 treatment was the most common risk factor (85.75%). Compared to controlled diabetics, C-ROCM was significantly higher among uncontrolled diabetics (odds ratio [OR] 0.15, 95% confidence interval [C.I.] 0.041–0.544, P = 0.0010). However, no significant association was seen between C-ROCM and COVID-19 severity (OR 0.930, 95% C.I. 0.212–4.087, P = 0.923). For treatment, amphotericin-B was the most common antifungal drug used which was followed by surgical options. However, mortality was high (prevalence 0.344, 95% C.I. 0.205–0.403) despite treatment.

CONCLUSION:

Although local rhino-orbito symptoms were the first to appear, rapid intracranial extension was seen in a significant number of C-ROCM cases. Uncontrolled diabetes and excessive use of corticosteroid were the most common risk factors present among the C-ROCM cases. High index clinical suspicion is imperative (specifically among COVID-19 patients with diabetes), and routine screening may be helpful.