Multiple gene targeting siRNAs for down regulation of Immediate Early-2 (Ie2) and DNA polymerase genes mediated inhibition of novel rat Cytomegalovirus (strain All-03)

Krishnan Nair Balakrishnan,Jamilu Abubakar Bala,Ashwaq Ahmed Abdullah,Che Azurahanim Che Abdullah,Mohd Lila Mohd-Azmi,Mustapha Mohamed Noordin,Faez Firdaus Abdullah Jesse

doi:10.1186/s12985-020-01436-5

Krishnan Nair Balakrishnan, Jamilu Abubakar Bala + Show 5 more

Open Access

https://doi.org/10.1186/s12985-020-01436-5

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Abstract

BackgroundCytomegalovirus (CMV) is an opportunistic pathogen that causes severe complications in congenitally infected newborns and non-immunocompetent individuals. Developing an effective vaccine is a major public health priority and current drugs are fronting resistance and side effects on recipients. In the present study, with the aim of exploring new strategies to counteract CMV replication, several anti-CMV siRNAs targeting IE2 and DNA polymerase gene regions were characterized and used as in combinations for antiviral therapy.MethodsThe rat embryo fibroblast (REF) cells were transfected with multi siRNA before infecting with CMV strain ALL-03. Viral growth inhibition was measured by tissue culture infectious dose (TCID50), cytopathic effect (CPE) and droplet digital PCR (ddPCR) while IE2 and DNA polymerase gene knockdown was determined by real-time PCR. Ganciclovir was deployed as a control to benchmark the efficacy of antiviral activities of respective individual siRNAs.ResultsThere was no significant cytotoxicity encountered for all the combinations of siRNAs on REF cells analyzed by MTT colorimetric assay (P > 0.05). Cytopathic effects (CPE) in cells infected by RCMV ALL-03 had developed significantly less and at much slower rate compared to control group. The expression of targeted genes was downregulated successfully resulted in significant reduction (P < 0.05) of viral mRNA and DNA copies (dpb + dpc: 79%, 68%; dpb + ie2b: 68%, 60%; dpb + dpc + ie2b: 48%, 42%). Flow cytometry analysis showed a greater percentage of viable and early apoptosis of combined siRNAs-treated cells compared to control group. Notably, the siRNAs targeting gene regions were sequenced and mutations were not encountered, thereby avoiding the formation of mutant with potential resistant viruses.ConclusionsIn conclusion. The study demonstrated a tremendous promise of innovative approach with the deployment of combined siRNAs targeting at several genes simultaneously with the aim to control CMV replication in host cells.

Highlights

CMV often considerate as silent public health burden usually does not produce any symptoms after the infection
Effects of combination Small interfering RNA (siRNA) on cell viability Combinations of siRNAs were subjected for cell viability assay using MTT cell proliferation method
Cytotoxicity analyses of tested siRNA combinations demonstrated that cell viability was almost unaffected at an optimized concentration of 300 pmol at different time points

Summary

Introduction

CMV often considerate as silent public health burden usually does not produce any symptoms after the infection. In other mono-therapies, sequence specific RNAi facing problem where the virus escapes due to the mutant in target region resulting in growth of viral mutant [18,19,20]. This statement validated by few studies such as polio, HIV and HCV where the viral activity of single siRNA reported to decrease in efficiency [19,20,21]. With the aim of exploring new strategies to counteract CMV replication, several anti-CMV siRNAs targeting IE2 and DNA polymerase gene regions were characterized and used as in combinations for antiviral therapy

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