Development and evaluation of a ligation-free sequence-independent, single-primer amplification (LF-SISPA) assay for whole genome characterization of viruses

Molecular identification and characterization of novel or re-emerging infectious pathogens is critical for disease surveillance and outbreak investigations. Next generation sequencing (NGS) using Sequence-Independent, Single-Primer Amplification (SISPA) is being used extensively in sequencing of viral genomes but it requires an expensive library preparation step. We developed a simple, low-cost method that enriches nucleic acids followed by a ligation-free (LF) 2-step Polymerase Chain Reaction (PCR) procedure for library preparation. A pan-chimeric universal primer (JS15N14) containing 15 nucleotides with a random tetradecamer (14N) attached to the 3'-end was designed. The complimentary primer (JS15) was used for nucleic acid enrichment in a first round PCR. A second PCR was designed to create Illumina sequencer-compatible sequencing-ready libraries for NGS. The new LF-SISPA protocol was tested using six RNA and DNA viral genomes (10.8-229.4 kilobases, kb) from an ATCC virome nucleic acid mix (ATCC® MSA-1008™) followed by analysis using One Codex, an online identification tool. In addition, a human stool sample known to be positive for norovirus GII was sequenced, and de novo assembly was performed using the Genome Detective Virus Tool allowing for near complete genome identification in less than 24 h. The LF-SISPA method does not require prior knowledge of target sequences and does not require an expensive enzymatic library preparation kit, thereby providing a simple, fast, low-cost alternative for the identification of unknown viral pathogens.