Seed-Region-Focused Validation of a Sindbis Virus-Specific siRNA: Insights into Off-Target Minimization and Host-Specific RNAi Constraints

Abstract

RNA interference (RNAi) using small interfering RNAs (siRNAs) is a promising antiviral strategy, but its efficacy in mammalian cells against alphaviruses like Sindbis virus (SINV) remains limited. A 21-nucleotide siRNA targeting the conserved 5' untranslated region of SINV was computationally designed and rigorously validated for specificity using full-sequence BLASTN against the human RefSeq RNA database and exhaustive seed-region k-mer searches (6–8 nt from guide positions 2–9). These tests revealed no significant similarity to human transcripts, indicating minimal off-target risk. siDirect 2.0 analysis further confirmed high target selectivity with no predicted effective off-target candidates. However, experimental testing showed silencing activity only with a 7-nt seed fragment, rather than with the full-length siRNA, consistent with evidence that classical RNAi antiviral responses are weak in most mammalian somatic cells due to dominant immune pathways and limited production of virus-derived siRNAs (Donaszi-Ivanov et al. 2013). Some studies report virus-derived siRNAs in mammalian central nervous system cells, suggesting RNAi activity specific to the cell type (Donaszi-Ivanov 2013). Additionally, interactions between Dicer and antiviral proteins such as PKR indicate that RNAi components may modulate immune responses without the input of RNA silencing pathways in mammalian cells (Montavon et al. 2020). Overall, these findings highlight that while computational seed-focused validation can minimize off-target effects, biological constraints in mammalian hosts limit classical siRNA antiviral efficacy against SINV, emphasizing the need for host and context awareness in therapeutic design.

Keywords

Natural Science - Biology

Citation

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Conflict of interest statement: No conflict of interest statement is attached to this public record unless stated in the manuscript.

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