Selection and characterization of novel DNA aptamers specifically recognized by Singapore grouper iridovirus-infected fish cells

Singapore grouper iridovirus (SGIV) is a major viral pathogen of grouper aquaculture, and has caused heavy economic losses in China and South-east Asia. In this study, we generated four ssDNA aptamers against SGIV-infected grouper spleen (GS) cells using SELEX (systematic evolution of ligands by exponential enrichment) technology. Four aptamers exhibited high affinity to SGIV-infected GS cells, in particular the Q2 aptamer. Q2 had a binding affinity of 12.09 nM, the highest of the four aptamers. These aptamers also recognized SGIV-infected tissues with high levels of specificity. Protease treatment and flow cytometry analysis of SGIV-infected cells revealed that the target molecules of the Q3, Q4 and Q5 aptamers were trypsin-sensitive proteins, whilst the target molecules of Q2 might be membrane lipids or surface proteins that were not trypsin-sensitive. The generated aptamers appeared to inhibit SGIV infection in vitro. Aptamer Q2 conferred the highest levels of protection against SGIV and was able to inhibit SGIV infection in a dose-dependent manner. In addition, Q2 was efficiently internalized by SGIV-infected GS cells and localized at the viral assembly sites. Our results demonstrated that the four novel aptamers we generated were specific for SGIV-infected cells and could potentially be applied as rapid molecular diagnostic test reagents or therapeutic drugs targeting SGIV.