RESUMO
SARS-CoV-2 variants of concern (VOCs) represent an alarming threat as they show altered biological behavior and may escape vaccination effectiveness. Broad-spectrum antivirals could play an important role to control infections. The activity of Echinacea purpurea (Echinaforce® extract, EF) against (i) VOCs B1.1.7 (alpha), B.1.351.1 (beta), P.1 (gamma), B1.617.2 (delta), AV.1 (Scottish), B1.525 (eta), and B.1.1.529.BA1 (omicron); (ii) SARS-CoV-2 spike (S) protein-pseudotyped viral particles and reference strain OC43 as well as (iii) wild type SARS-CoV-2 (Hu-1) was analyzed. Molecular dynamics (MD) were applied to study the interaction of Echinacea's phytochemical markers with known pharmacological viral and host cell targets. EF extract broadly inhibited the propagation of all investigated SARS-CoV-2 VOCs as well as the entry of SARS-CoV-2 pseudoparticles at EC50's ranging from 3.62 to 12.03 µg/mL. The preventive addition of 25 µg/mL EF to epithelial cells significantly reduced sequential infection with SARS-CoV-2 (Hu-1) and OC43. MD analyses showed constant binding affinities to VOC-typical S protein variants for alkylamides, caftaric acid, and feruloyl-tartaric acid in EF extract and interactions with serine protease TMPRSS-2. EF extract demonstrated stable virucidal activity across seven tested VOCs, likely due to the constant affinity of the contained phytochemical substances to all spike variants. A possible interaction of EF with TMPRSS-2 partially would explain the cell protective benefits of the extract by the inhibition of membrane fusion and cell entry. EF may therefore offer a supportive addition to vaccination endeavors in the control of existing and future SARS-CoV-2 virus mutations.
RESUMO
Naive CD4+ T cells differentiate into effector (Th1, Th2, Th17) cells and immunosuppressive (Treg) cells upon antigenic stimulation in the presence of a specific cytokine milieu. The T cell in vitro culture system provides a very efficient model to study compounds' therapeutic activity and mechanism of action. Tinospora cordifolia (Willd.) Hook.f. & Thomson (Family. Menispermaceae) is one of the widely used drugs in Ayurveda (ancient Indian system of medicine) for various ailments such as inflammatory conditions, autoimmune disorders, and cancer as well as for promoting general health. In vitro and in vivo studies on immune cells comprising dendritic cells, macrophages, and B cells suggest its immune-modulating abilities. However, to date, the effect of T. cordifolia on individual purified and polarized T cell subsets has not been studied. Studying drug effects on T cell subsets is needed to understand their immunomodulatory mechanism and to develop treatments for diseases linked with T cell abnormalities. In this study, we examined the immunomodulatory activity of T. cordifolia on primary CD4+ T cells, i.e., Th1, Th17, and iTreg cells. An aqueous extract of T. cordifolia was non-cytotoxic at concentrations below 1500 µg/ml and moderately inhibited the proliferation of naive CD4+ T cells stimulated with anti-CD3ε and anti-CD28 for 96 h. T. cordifolia treatment of naive CD4+ T cells differentiated under Th17-polarizing conditions exhibited reduced frequency of IL-17 producing cells with inhibition of differentiation and proliferation. For the first time, in-depth genome-wide expression profiling of T. cordifolia treated naive CD4+ T cells, polarized to Th17 cells, suggests the broad-spectrum activity of T. cordifolia. It shows inhibition of the cytokine-receptor signaling pathway, majorly via the JAK-STAT signaling pathway, subsequently causing inhibition of Th17 cell differentiation, proliferation, and effector function. Additionally, the molecular docking studies of the 69 metabolites of T. cordifolia further substantiate the inhibitory activity of T. cordifolia via the cytokine-receptor signaling pathway. Furthermore, in vitro polarized Th1 and iTreg cells treated with T. cordifolia extract also showed reduced IFN-γ production and FoxP3 expression, respectively. This study provides insight into the plausible mechanism/s of anti-inflammatory activity of T. cordifolia involving T cells, mainly effective in Th17-associated autoimmune and inflammatory diseases.