Cross-protection of influenza A virus infection by a DNA aptamer targeting the PA endonuclease domain.
Amino acid residues in the N-terminal of the PA subunit (PAN) of the influenza A virus polymerase play critical roles in endonuclease activity, protein stability, and viral RNA (vRNA) promoter binding. In addition, PAN is highly conserved among different subtypes of influenza virus, which suggests PAN to be a desired target in the development of anti-influenza agents. We selected DNA aptamers targeting the intact PA protein or the PAN domain of an H5N1 virus strain using systematic evolution of ligands by exponential enrichment (SELEX). The binding affinities of selected aptamers were measured, followed by an evaluation of in vitro endonuclease inhibitory activity. Next, the antiviral effects of enriched aptamers against influenza A virus infections were examined. A total of three aptamers targeting PA and six aptamers targeting PAN were selected. Our data demonstrated that all three PA-selected aptamers neither inhibited endonuclease activity nor exhibited antiviral efficacy, whereas four of the six PAN-selected aptamers inhibited both endonuclease activity and H5N1 virus infection. Among the four effective aptamers, one exhibited cross-protection against infections of H1N1, H5N1, H7N7, and H7N9 influenza viruses, with a 50% inhibitory concentration (IC50) of around 10 nM. Notably, this aptamer was identified at the 5th round but disappeared after the 10th round of selection, suggesting that the identification and evaluation of aptamers at early rounds of selection may be highly helpful for screening effective aptamers. Overall, our study provides novel insights for screening and developing effective aptamers for use as anti-influenza drugs.
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Shuofeng
S
Yuan
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Naru
N
Zhang
School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, China.
Kailash
K
Singh
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Huiping
H
Shuai
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Hin
H
Chu
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Jie
J
Zhou
School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, China.
Billy K C
BK
Chow
Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China bzheng@hkucc.hku.hk.
Bo-Jian
BJ
Zheng
D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use*; D052157:Aptamers, Nucleotide / Q000627:therapeutic use*; D002151:Calorimetry; D002460:Cell Line; D056738:Cross Protection; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000737:chemistry; D004285:Dogs; D004720:Endonucleases / Q000187:drug effects*; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000187:drug effects / Q000201:enzymology*; D007251:Influenza, Human / Q000517:prevention & control*; D007313:Insecta; D061985:Madin Darby Canine Kidney Cells; D009841:Oligonucleotides / Q000494:pharmacology; D017433:Protein Structure, Secondary; D052156:SELEX Aptamer Technique; D013045:Species Specificity
D000998:Antiviral Agents; D052157:Aptamers, Nucleotide; D009841:Oligonucleotides; D004720:Endonucleases; D003850:Deoxyribonuclease I