Amplification-Free Nanopore Sequencing for Herpesvirus DNA Detection in Intraocular Fluids.
PURPOSE: To evaluate the feasibility of amplification-free nanopore sequencing for detecting herpesvirus DNA in intraocular fluid using multiplex polymerase chain reaction (mPCR)-characterized herpesvirus-positive and herpesvirus-negative samples. DESIGN: Retrospective, single-center, cross-sectional study. PARTICIPANTS: This study included 42 patients with uveitis whose intraocular fluid samples were examined by mPCR, including 20 mPCR-positive samples (all positive for herpesviruses) and 22 mPCR-negative samples. METHODS INTERVENTION OR TESTING: DNA extracted from intraocular fluid samples underwent ligation-based library preparation without whole-genome amplification and was sequenced on the MinION platform with Flongle flow cells for untargeted analysis. Nanopore sequencing results were compared with mPCR findings, and associations between nanopore-derived virus-specific read counts and corresponding herpesvirus DNA copy numbers measured by mPCR were assessed. MAIN OUTCOME MEASURES: Primary outcome measure was concordance between nanopore sequencing and mPCR in herpesvirus species identification. Secondary outcome measures included nanopore sequencing detection rates stratified according to mPCR-measured herpesvirus DNA copy numbers and correlations between nanopore sequencing-derived virus-specific read counts and mPCR-measured herpesvirus DNA copy numbers. RESULTS: Among 20 mPCR-positive intraocular fluid samples, nanopore sequencing identified viral DNA from the same herpesvirus species detected by mPCR in 15 (75.0%), indicating species-level concordance. None of the 22 mPCR-negative samples contained virus-specific reads. Among the 22 herpesvirus targets identified in the 20 mPCR-positive samples, herpesvirus DNA copy numbers measured by mPCR were significantly higher in nanopore-positive than in nanopore-negative targets (P = 0.015). Nanopore detection rates increased with increasing herpesvirus DNA copy numbers measured by mPCR: 3 of 6 targets (50.0%) with <105 copies/mL, 2 of 4 (50.0%) with 105-106 copies/mL, and 12 of 12 (100%) with >106 copies/mL (P = 0.021). Nanopore sequencing-derived virus-specific read counts correlated positively with herpesvirus DNA copy numbers measured by mPCR (r = 0.76, P = 0.0004). CONCLUSIONS: Amplification-free nanopore sequencing demonstrated the feasibility of detecting herpesvirus DNA in intraocular fluid samples, with detection performance dependent on herpesvirus DNA load. This simplified workflow may provide complementary information regarding viral DNA burden in minute ocular samples. FINANCIAL DISCLOSURES: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.