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Inhibition of SARS-CoV replication cycle by small interference RNAs silencing specific SARS proteins, 7a/7b, 3a/3b

Sara Akerström1, Ali Mirazimi, Yee-Joo Tan

  • 1Center for Microbiological Preparedness, Swedish Institute for Infectious Disease Control, SE-171 82 Solna, Sweden.

Antiviral Research
|November 23, 2006
PubMed

Insights

Small interference RNAs (siRNAs) targeting specific subgenomic RNAs (sgRNAs) of SARS-CoV effectively silenced viral proteins. This approach reduced progeny virus yield and highlighted the role of accessory proteins in viral replication.

Area of Science:

  • Virology
  • Molecular Biology
  • RNA Interference

Background:

  • The severe acute respiratory syndrome coronavirus (SARS-CoV) genome contains 14 open reading frames (ORFs).
  • Viral proteins are translated from full-length genomic mRNA and eight subgenomic RNAs (sgRNAs).
  • Understanding the function of individual viral proteins is crucial for combating SARS-CoV infection.

Purpose of the Study:

  • To design and test small interference RNAs (siRNAs) for specific silencing of SARS-CoV sgRNAs.
  • To evaluate the efficiency and specificity of siRNAs in inhibiting viral protein expression.
  • To investigate the role of SARS-CoV accessory proteins in viral replication.

Main Methods:

  • Design of siRNAs targeting sgRNA 2, 3, and 7 of SARS-CoV.
  • Testing siRNA efficiency and specificity against viral mRNAs using nucleotide matching criteria.
  • Infection of Vero E6 cells with SARS-CoV in the presence of designed siRNAs.
  • Quantification of progeny virus yield and analysis of viral protein expression using indirect immunofluorescence assays.

Main Results:

  • siRNA 7 specifically inhibited sgRNA 7 (19/19 nt match) and sgRNA 8 (18/19 nt match) without affecting full-length genomic mRNA (17/19 nt match).
  • All tested siRNAs effectively inhibited their targeted sgRNAs without affecting other sgRNAs with two or more nucleotide mismatches.
  • Infection of Vero E6 cells with SARS-CoV and siRNAs resulted in a significant reduction in progeny virus yield.
  • Specific silencing of S, 3a, and 7a proteins was observed, while nucleocapsid protein expression remained unaffected.

Conclusions:

  • siRNAs can be effectively designed to knockdown specific viral protein expression from targeted sgRNAs during SARS-CoV infection.
  • Accessory proteins 3a and 7a play a significant role in the SARS-CoV replication cycle.
  • This study provides a method for delineating the contribution of individual viral proteins to viral infection.

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