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Activities of an aqueous plant extract against herpes simplex virus type2 (HSV 2): role in virus replication and progeny yield

Publication . Mota Mendes, Ana Rita; Caeiro, Maria Filomena; Lopo, Sílvia

Herpes simplex virus type 2 (HSV-2) is widely distributed through the human population, infecting more than 500 million people globally. Although causing generally mild infections this virus may cause severe symptoms occasionally, mainly in immunocompromised patients. Presently, there are a number of systemic antiviral agents against herpesvirus, the most commonly used being acyclovir (ACV) and its prodrugs. However, long term treatments with these drugs may result in the development of resistance, especially in immunocompromised patients, which leads to a continuous search for new and better therapeutic alternatives. According to the World Health Organization (WHO) plants would be the best sources for obtaining a wide variety of drugs. In fact, in the last decades many pharmacological and chemical studies have focused on medicinal plants and the discovery of new natural therapeutic compounds. In this study the anti-herpetic action of an aqueous extract was evaluated. The product was obtained by decoction of stem and leaves from Solidago virgaurea, a perennial herb member of the Asteraceae family. The study of the aqueous extract activity included a preliminary evaluation of its cytotoxicity in Vero cells – by the MTT assay - in the same conditions that are applied for viral production. Extract direct effect on viral particles – virucidal effect – was also assessed, having proved null. Anti-herpetic activity was investigated through two kinds of experiments: treatment of infected cells during virus production that revealed a mean yield reduction of 94 % in treated relatively to non-treated cells and an IC50 of 35.1 μg/mL; and treatment of infected cells during virus titration, which revealed slighter inhibition but significant size differences between virus plaques formed in treated and control conditions (smaller in treatment conditions). To further evaluate the mechanisms that mediate the aqueous extract inhibitory effect, infected cells – treated and non-treated - and virus particles – produced in treated and non-treated cells - were visualized through Transmission Electron Microscopy (TEM), revealing less damage due to infection in treated cells and a reduced amount of viral particles in HSV-2 suspensions produced in treated cells, relatively to controls. A kinetic of the first hours of the infection was performed with and without treatment, to assess possible differences in DNA production. Extracted samples were subjected to qPCR and results showed that the amount of viral DNA raises significantly slower in treated versus non-treated infected cells, throughout the infection. This is consistent with the effective reduction of the extract when added at later infection times - 4-6 h p.i. - when DNA replication is already in an advanced stage. Our results suggest that the aqueous extract inhibits HSV-2 replication, when present at the beginning of the infection, possibly by interfering with the viral DNA synthesis.

2015Master thesis

Open access

Evaluation of the antiviral activity of an aqueous extract from Solidago virgaurea against Herpes simplex virus type 2

Publication . Mendes, Ana Rita; Lopo, Sílvia; Ascensão, Lia; Falé, Pedro; Serralheiro, Luisa; Caeiro, Maria Filomena

Herpes simplex virus type 2 (HSV-2) is widely distributed through the human population, infecting more than 500 million people globally [1]. Although typically causing mild diseases this virus may be responsible for severe infections, mainly in immunocompromised patients. Currently, there is a number of systemic antiviral agents against herpesvirus, the most commonly used being acyclovir and related drugs. However, long term treatments with these drugs may result in the development of resistance, especially in immunocompromised patients, which leads to a continuous search for new and better therapeutic alternatives [2]. According to the World Health Organization plants are the best sources for obtaining a wide variety of drugs [3]. So, in the last decades many pharmacological and chemical studies have focused on medicinal plants to the discovery of new natural antiviral compounds.

2016-09Conference object

Restricted access

Sugar-based bactericides targeting phosphatidylethanolamine-enriched membranes

Publication . Dias, Catarina; Pais, João P.; Nunes, Rafael; Blázquez-Sánchez, Maria-Teresa; Marquês, Joaquim T.; Almeida, Andreia F.; Serra, Patrícia; Xavier, Nuno M.; Vila-Viçosa, Diogo; Machuqueiro, Miguel; Viana, Ana S.; Martins, Alice; Santos, Maria S.; Pelerito, Ana; Dias, Ricardo; Tenreiro, Rogério; Oliveira, Maria C.; Contino, Marialessandra; Colabufo, Nicola A.; de Almeida, Rodrigo F.M.; Rauter, Amélia P.

Anthrax is an infectious disease caused by Bacillus anthracis, a bioterrorism agent that develops resistance to clinically used antibiotics. Therefore, alternative mechanisms of action remain a challenge. Herein, we disclose deoxy glycosides responsible for specific carbohydrate-phospholipid interactions, causing phosphatidylethanolamine lamellar-to-inverted hexagonal phase transition and acting over B. anthracis and Bacillus cereus as potent and selective bactericides. Biological studies of the synthesized compound series differing in the anomeric atom, glycone configuration and deoxygenation pattern show that the latter is indeed a key modulator of efficacy and selectivity. Biomolecular simulations show no tendency to pore formation, whereas differential metabolomics and genomics rule out proteins as targets. Complete bacteria cell death in 10 min and cellular envelope disruption corroborate an effect over lipid polymorphism. Biophysical approaches show monolayer and bilayer reorganization with fast and high permeabilizing activity toward phosphatidylethanolamine membranes. Absence of bacterial resistance further supports this mechanism, triggering innovation on membrane-targeting antimicrobials.

2018-11-19Journal article

Open access