Atividade antiviral de novos análogos de benzotiazóis contra o vírus Chikungunya in vitro

Abstract

Chikungunya virus (CHIKV) is the causative agent of Chikungunya fever (FCHIKV) transmitted by arthropod vectors of the genus Aedes sp. Patients affected by FCHIKV present symptoms such as fever, headache, intense myalgia and arthralgia that can last for months to years after infection. FCHIKV can lead to chronic complications that can affect the quality of life of patients, who suffer from the lack of specific treatment. Considering this context, the objective of the present study was to evaluate the antiviral activity of new, previously synthesized benzothiazole analogues against CHIKV in vitro. Initially, a cytotoxicity test was carried out with the 19 compounds for initial screening and determination of oncentrations for use in Vero E6 cells using the MTT methodology, in which it was found that 8 compounds wee cytotoxic at 50 µM. Thus, the remaining compounds were subjected to serial cytotoxicity testing concentrations 200, 100 and 50 µM, in which only 3 compounds did not show cytotoxicity at all concentrations tested. Based on these results, the 11 compounds were tested in a post-treatment assay on Vero E6 cells inoculated with CHIKV (MOI 0.01) at concentrations from 50 to 6.25 µM for 48h and cell viability and viral inhibition were determined by MTT. All tested compounds had a significant viral effect at the highest concentration tested, then selectivity indices (SI) were evaluated to select the most promising compounds, obtaining IS >20.55 for EdCHIK10; >30.58 for EdCHIK39 and >20.87 for EdCHIK82.To confirm the antiviral activity, an intracellular flow cytometry assay was carried out in order to detect a reduction in the percentage of cells positive for CHIKV post-treatment with the compounds, an average reduction from 40.97 ± 9.84% of virus-infected cells detected in the untreated viral control to 8.40 ± 1.81 % in EdCHIK10, 11.13 ± 0.35 % in EdCHIK39 and 21.86 ± 12.04 % in EdCHIK82. To understand the possible mechanisms of action, a time of drug addition test was then carried out, where activity was evaluated pre, during and post-treatment, in which a slight inhibition was observed in the pre-treatment test for EdCHIK10 and 39, no inhibition during adsorption and significant inhibition in post-treatment was observed to all 3 compounds. The structure-activity relationship study of the compounds showed substituents at position 6 of the benzothiazole with the most promising antiviral activity and SI. Thus, it is concluded that the compounds demonstrated promising antiviral activity against CHIKV in vitro, contributing to the future design of new bioactive molecules against this arbovirus.