Abstracts of the papers presented in the international conference of Indian virological society, ‘‘Global viral epidemics: a challenging threat”, during 12–14 November, 2018, at PGIMER, Chandigarh, India

Abstract

Chikungunya virus (CHIKV), a mosquito born pathogenic virus, causes fever, arthritis and encephalitis in humans. Presently, there is no specific drug/antiviral available for CHIKV treatment. Upon entry into host cell, ssRNA of CHIKV is directly translated into nonstructural polyprotein precursor P1234 which is processed by virus specific nsP2pro. This nsP2pro mediated processing is an essential function in viral life cycle and thus nsP2pro constitutes an attractive target for antiviral drug development. In this study, we have elucidated the 3D structure of CHIKV nsP2pro which revealed the presence of two subdomains; N-terminal protease subdomain and a C-terminal MTase-like subdomain. Active site of the protein consists of a catalytic dyad made up of cysteine and histidine and is located at the interface of the two subdomains. Detail structural analysis and comparison revealed the presence of a flexible loop gating the active site. This loop possesses conserved residues Asn547 and Trp549. Furthermore, by mimicking the intermolecular interaction between substrate peptide and the active site residues of nsP2pro, a series of peptidomimetic compounds were identified. The conformational stability of these compounds was assessed by molecular docking and MD simulation. We developed a FRET based nsP2 protease activity assay to assess the inhibitory potential of identified compounds. Interestingly, two of the identified peptidomimetic compounds were found to possess inhibitory effect on the nsP2pro enzymatic activity. Inhibition of CHIKV nsP2pro by the tested compounds Pep-I & Pep-II was observed with IC50 values of 34 lM and 42 lM, respectively. The inhibition kinetic studies revealed the inhibition constant (Ki) to be 33.34 ± 2.53 lM for Pep-I and 45.89 ± 4.38 lM for Pep-II. Additionally, these two compounds were also validated by cell culture based plaque reduction assay and found to be significantly inhibiting CHIKV replication in BHK-21 cells at concentrations in nM range, which is much lower than their cytotoxic concentrations.