Influence of the Structural Features of Carrageenans from Red Algae of the Far Eastern Seas on Their Antiviral Properties

The structural diversity and unique physicochemical properties of sulphated polysaccharides of red algae carrageenans (CRGs), to a great extent, determine the wide range of their antiviral properties. This work aimed to compare the antiviral activities of different structural types of CRGs: against herpes simplex virus type 1 (HSV-1) and enterovirus (ECHO-1). We found that CRGs significantly increased the resistance of Vero cells to virus infection (preventive effect), directly affected virus particles (virucidal effect), inhibited the attachment and penetration of virus to cells, and were more effective against HSV-1. CRG1 showed the highest virucidal effect on HSV-1 particles with a selective index (SI) of 100. CRG2 exhibited the highest antiviral activity by inhibiting HSV-1 and ECHO-1 plaque formation, with a SI of 110 and 59, respectively, when it was added before virus infection. CRG2 also significantly reduced the attachment of HSV-1 and ECHO-1 to cells compared to other CRGs. It was shown by molecular docking that tetrasaccharides—CRGs are able to bind with the HSV-1 surface glycoprotein, gD, to prevent virus–cell interactions. The revealed differences in the effect of CRGs on different stages of the lifecycle of the viruses are apparently related to the structural features of the investigated compounds.

Synthesis and Anti-Chikungunya Virus (CHIKV) Activity of Novel 1,4-Naphthoquinone Sulfonamide and Sulfonate Ester Derivatives

Chikungunya virus (CHIKV) is a re-emerging disease caused by an alphavirus of the Togaviridae family. Since its first description in 1952, the disease has spread worldwide, affecting populations in both tropical and temperate countries. To date, there is no licensed vaccine or specific pharmacological treatment. Therefore, there is an increasing urgency in developing new antiviral drugs capable of specifically inhibiting viral replication. In the present work, we report the synthesis and antiviral activity evaluation of nineteen naphthoquinone derivatives, containing a sulfonamide or sulfonate group. Cell viability assays indicated a low toxic potential for all tested compounds and inhibitory assays against CHIKV identified five compounds with potent activity. The compounds were also evaluated for their virucidal potential, and the results demonstrated that compound 11a exhibited a virucidal effect higher than 70% in the treatment with 20 µM. Furthermore, in silico studies were performed to predict the antiviral drug targets.

Virucidal effect of povidone-iodine against SARS-CoV-2 in vitro

Objective To evaluate the antiviral activity of the oral disinfectant povidone-iodine (PVP-I) against severe acute respiratory syndrome-coronavirus-2 (SARS-CoV2) in vitro. Methods The cytotoxic effects of PVP-I were determined in Vero and Calu-3 cell lines using that by Cell Counting Kit-8 assay. Viral load in the cell culture medium above infected cells was quantitated using real-time polymerase chain reaction. The cytopathic effect (CPE) and viral infective rate were observed by immunofluorescence microscopy. Results PVP-I at a concentration >0.5 mg/ml in contact with SARS-CoV-2 for 30 s, 1 min, 2 min and 5 min showed up to 99% viral inhibition. For in vitro testing, upon exposure for 1 min, PVP-I showed a virucidal effect. PVP-I had no cytotoxic effects at the range of concentrations tested (0.125–1 mg/ml; CC50 > 2.75 mM) in Vero and Calu-3 cells. Conclusion These results demonstrate that the ideal contact time was 1 min and the optimal concentration was 1 mg/ml, which provides an experimental basis for the use of oral disinfectants in dental hospitals.

Determination of alcohols in hand sanitisers: Are off-the-shelf hand sanitisers what they claim to be?

Transmission of SARS-CoV-2 – the causative agent of COVID-19 – can be prevented through non-pharmaceutical interventions such as observing proper hand hygiene using alcohol-based hand rubs/sanitisers (ABHRs) as recommended by the WHO and local health authorities. However, this recommendation has led to high demand for ABHRs and proliferation of sub-standard products, which do not contain the recommended amount of alcohol. Fifty products of different origins and formulations obtained off-the-shelf and in public places in and around Pretoria (South Africa) were analysed for their alcohol content using gas chromatography. Ethanol was the most common alcohol used in the products, followed by isopropanol. Only 21 (42%) of the products analysed contained at least 70% alcohol; of these only 14 (28%) met the WHO recommended 80±5% alcohol content to have a virucidal effect on SARS-CoV-2. Of the 41 commercial off-the-shelf products analysed, 27 (66%) contained less than 70% alcohol in comparison to 13% of homemade products. Only 18% of gel products contained 70% alcohol, compared with 47% for liquid-based products. Most of the products did not contain the appropriate or correct declaration as recommended by the South African National Standards (SANS 289 and 490). The proliferation of substandard ABHRs is of great public health concern and calls for stricter regulations and enforcement in order to protect consumers, their rights and well-being during and post the COVID-19 pandemic period. However, in the interim, formulation of ABHRs using the WHO guidelines should be mandatory, as such formulations, when made correctly, do have the required virucidal effect against SARS-CoV-2.

Curcumin Inhibits In Vitro SARS-CoV-2 Infection In Vero E6 Cells through Multiple Antiviral Mechanisms

Due to the scarcity of therapeutic approaches for COVID-19, we investigated the antiviral and anti-inflammatory properties of curcumin against SARS-CoV-2 using in vitro models. The cytotoxicity of curcumin was evaluated using MTT assay in Vero E6 cells. The antiviral activity of this compound against SARS-CoV-2 was evaluated using four treatment strategies (i. pre–post infection treatment, ii. co-treatment, iii. pre-infection, and iv. post-infection). The D614G strain and Delta variant of SARS-CoV-2 were used, and the viral titer was quantified by plaque assay. The anti-inflammatory effect was evaluated in peripheral blood mononuclear cells (PBMCs) using qPCR and ELISA. By pre–post infection treatment, Curcumin (10 µg/mL) exhibited antiviral effect of 99% and 99.8% against DG614 strain and Delta variant, respectively. Curcumin also inhibited D614G strain by pre-infection and post-infection treatment. In addition, curcumin showed a virucidal effect against D614G strain and Delta variant. Finally, the pro-inflammatory cytokines (IL-1β, IL-6, and IL-8) released by PBMCs triggered by SARS-CoV-2 were decreased after treatment with curcumin. Our results suggest that curcumin affects the SARS-CoV-2 replicative cycle and exhibits virucidal effect with a variant/strain independent antiviral effect and immune-modulatory properties. This is the first study that showed a combined (antiviral/anti-inflammatory) effect of curcumin during SARS-CoV-2 infection. However, additional studies are required to define its use as a treatment for the COVID-19.

Virucidal Activity of Plant Extracts against African Swine Fever Virus

African swine fever is one of the most dangerous and fatal swine diseases, described for the first time roughly a hundred years ago. Even now, there is neither a commercially approved vaccine nor treatment available. The only way to hinder further spread of the disease is by culling the affected herds and applying prevention based mainly on proper biosecurity. Due togrowing awareness of the potential ASF threat among pig producers, disinfection processes are considered as one of the most important preventive measures. Currently, a variety of chemical compounds are applied for the disinfection of pig farms. Meanwhile, these chemicals may pose a potential risk, due to their toxic, irritant or corrosive effect. The aim of this study was to determine whether any plant-based natural compounds may show a virucidal effect against ASFV, and simultaneously be depleted of some of the side-effects typical for chemical compounds. Ideally, natural virucidal compounds should be safe for both humans and animals, biodegradable, easily available and inexpensive. Fourteen plant extracts were selected and screened for their virucidal effect against ASFV, using the suspension test inspired by the PN-EN 14675:2015 European Standard procedure. The results of our study showed that most of the tested plant extracts were ineffective against ASFV. Some extracts suspended in a hydroglycolic medium exhibited high virus titre reduction, but it was confirmed that the effect resulted from medium composition. However, a 1.05% peppermint extract showed high effectiveness against ASFV, reducing the virus titre by ≥4 log10, thus demonstrating that natural compounds used as virucidal agents could potentially be used in disinfection procedures, being both effective and harmless to humans and animals.

Virucidal Effect of the Mesoscopic Structure of CAC-717 on Severe Acute Respiratory Syndrome Coronavirus-2

Here, the virucidal effect of calcium bicarbonate with a mesoscopic structure (CAC-717) on severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was determined. Assays showed that CAC-717 had a strong virucidal effect on all examined SARS-CoV-2 isolates, including variant strains. The viral infectivity decreased within 15 s, and the virucidal activity of CAC-717 at a 1:49 ratio was similar to that of ethanol disinfectant. CAC-717 neutralization eliminated this virucidal effect, indicating that the alkaline condition of CAC-717 is important for virus inactivation and is an indicator of its mesoscopic structure and virucidal activity. The virucidal effect was observed in the presence of organic matter (bovine serum albumin). CAC-717 is a non-invasive and non-flammable substance with a low environmental burden, and its usefulness as a novel disinfectant has been confirmed.

Direct virucidal effect of a throat lozenge with fixed combination of cetylpyridinium chloride and benzydamine hydrochloride on SARS-CoV-2 – in vitro study

Objectives. To evaluate the in vitro virucidal effect of the combination of cetylpyridinium chloride (CPC) and benzydamine hydrochloride (BH) as a throat lozenge against the novel SARS-CoV-2. Material and methods. The study evaluated the viral presence and titre in cell cultures by using SARS-CoV-2 virus incubated for 1, 5, 15 minutes, with three different concentrations of three different active substances (CPC, free BH/ CPC, BH/CPC lozenge). The titre of the virus was expressed as TCID50/ml calculated with the Spearman-Kärber method. Outcomes. The faster virucidal effect in high concentration was seen in the combination BH/CPC as throat lozenge when compared to CPC as free active substance. A reduction of the virus concentration was seen, at 15 minutes contact, in all three concentrations. Conclusions. There is a strong virucidal effect a throat lozenge with fixed combination of cetylpyridinium chloride and benzydamine hydrochloride on the novel coronavirus.