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. 2021 Feb 15:324:114734.
doi: 10.1016/j.molliq.2020.114734. Epub 2020 Nov 10.

A computational study to disclose potential drugs and vaccine ensemble for COVID-19 conundrum

Affiliations

A computational study to disclose potential drugs and vaccine ensemble for COVID-19 conundrum

Sajjad Ahmad et al. J Mol Liq. .

Abstract

The nucleocapsid (N) protein of SARS-COV-2, a virus responsible for the current COVID-19 pandemic, is considered a potential candidate for the design of new drugs and vaccines. The protein is central to several critical events in virus production, with its highly druggable nature and rich antigenic determinants making it an excellent anti-viral biomolecule. Docking-based virtual screening using the Asinex anti-viral library identified binding of drug molecules at three specific positions: loop 1 region, loop 2 region and β-sheet core pockets, the loop 2 region being the most common binding and stable site for the bulk of the molecules. In parallel, the protein was characterized by vaccine design perspective and harboured three potential B cell-derived T cell epitopes: PINTNSSPD, GVPINTNSS, and DHIGTRNPA. The epitopes are highly antigenic, virulent, non-allergic, non-toxic, bind with good affinity to the highly prevalent DRB*0101 allele and show an average population coverage of 95.04%. A multi-epitope vaccine ensemble which was 83 amino acids long was created. This was highly immunogenic, robust in generating both humoral and cellular immune responses, thermally stable, and had good physicochemical properties that could be easily analyzed in in vivo and in vitro studies. Conformational dynamics of both drug and vaccine ensemble with respect to the receptors are energetically stable, shedding light on favourable conformation and chemical interactions. These facts were validated by subjecting the complexes to relative and absolute binding free energy methods of MMGB/PBSA and WaterSwap. A strong agreement on the system stability was disclosed that supported ligand high affinity potential for the receptors. Collectively, this work sought to provide preliminary experimental data of existing anti-viral drugs as a possible therapy for COVID-19 infections and a new peptide-based vaccine for protection against this pandemic virus.

Keywords: COVID-1; Drugs; Nucleocapsid (N) protein; SARS-COV-2; Vaccine.

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Conflict of interest statement

The authors in this study have no conflict of interest.

Figures

Unlabelled Image
Graphical abstract
Fig. 1
Fig. 1
Flow of steps used in the current study.
Fig. 2
Fig. 2
Waterbox presentation of drug (top) and vaccine ensemble complex with respective receptors (colored by yellow cartoon). The drug and vaccine construct is shown by in green sphere.
Fig. 3
Fig. 3
Docked pose of different classes of anti-viral inhibitors at different pockets of the SARS-COV-2 N protein. The color order of the top 5 ligands is in the following order: top 1 (tan), top 2 (cyan), top 3 (pink), top 4 (aquamarine), and top 5 (deep pink).(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 4
Fig. 4
Chemical network of interaction of the compounds at respective docked sites. From A to E tags represents compound 1 to 5, respectively. The different color of discs can be interpreted as residues of the N protein and can be understand as: dark green discs (hydrogen bonding residues), light green discs (van der Waals residues), pink discs (pi-pi stacked residues), purple discs (pi-sigma residues), and cream discs (alky and pi-alkyl residues).(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 5
Fig. 5
Surface analysis of final set of T cell epitopes localized at the surface of N protein. A (PINTNSSPD), B (GVPINTNSS) and C (DHIGTRNPA). The amino acids are presented by single letter code.
Fig. 6
Fig. 6
A. Schematic representation of the vaccine, B. 3D structure of the vaccine, C. Ramachandran plot of the vaccine, D. Secondary structure elements of the vaccine, E. Disulfide engineering of the vaccine; both original and mutated strucutures are presented, F. In silico cloning of the vaccine (shown as red) into pET-28a(+) vector. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
Fig. 7
Fig. 7
Host immune system simulation in response to the vaccine ensemble antigen; production of different immunoglobulin response (top) and cytokines and interleukins with Simpson index (bottom).
Fig. 8
Fig. 8
The top figure presents docked conformation of the vaccine ensemble (shown in dark maroon) at the active pocket of TLR3 (yellow cartoon surface as dot). The bottom figure illustrates closed view of the vaccine interacting with TLR3 residues (shown in red bubbles) via hydrogen bonding. The rest of red highlighted regions in sticks are those involved in van der Waals interactions with the TLR3 residues.
Fig. 9
Fig. 9
Different MD based analysis: protein rmsd (top left), ligand rmsd (top right), protein ROG (bottom left) and hydrogen bonds plotting (bottom right).
Fig. 10
Fig. 10
A. Binding conformation adjustments of drug molecule (shown in different color sticks) at the binding pocket of SARS-COV2 N protein (shown by gray surface), B. Binding conformation adjustments of vaccine (shown in different color cartoons) at the binding pocket of TLR3. The colouring pattern can be interpreted as: 0-ns (tan), 10-ns (cyan), 20-ns (orchid), 30-ns (light green), 40-ns (salmon), and 50-ns (gray).(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

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