A PCR-based assay for detecting and quantifying RNase L-mediated RNA cleavage in biological samples

Background

RNase L is a critical enzyme in the innate immune response, responsible for degrading RNA in response to viral infections and other immune triggers. Its activation is tightly regulated and serves as a key biomarker for inflammation, infection, and immune system activity. Accurate measurement of RNase L activity is important for understanding disease mechanisms and for the diagnosis and monitoring of a variety of conditions, including viral infections, autoimmune disorders, and certain cancers. However, the field has long faced challenges in developing reliable, sensitive, and specific assays to detect RNase L activity directly in clinical samples, which is essential for translating basic immunological insights into practical diagnostic and therapeutic tools.

Existing approaches to measuring RNase L activity are hampered by significant limitations. The most common method relies on detecting the cleavage of 28S ribosomal RNA, but this assay is relatively insensitive, requires large sample volumes, and lacks specificity because other nucleases can also degrade rRNA, leading to potential false positives. Additionally, measuring RNase L gene expression or protein levels does not accurately reflect its enzymatic activity, as post-translational regulation and activation are not captured by transcript or protein abundance alone. These shortcomings make it difficult to reliably assess immune activation or disease state in patients, limiting the clinical utility of current assays and underscoring the need for more sensitive and specific methods to monitor RNase L activity.

Technology

This technology provides a sensitive and specific method for monitoring RNase L activity in biological samples by detecting unique RNA cleavage products. The process involves isolating RNA from samples such as blood or tissue, then ligating a synthetic adapter to the 3’ ends of RNA fragments that possess 2’,3’-cyclic phosphate or 3’-phosphate groups—chemical signatures left by RNase L cleavage. Using RtcB RNA ligase, the adapter is attached to these fragments, which are then reverse-transcribed into cDNA. The resulting cDNA is amplified using PCR or qPCR with primers designed to specifically recognize the junction between the adapter and the RNase L cleavage site, ensuring high specificity for the cleaved RNA products. Quantification of these products, particularly fragments of tRNAs and Y-RNAs, serves as a sensitive biomarker for inflammation, infection, and immune responses, and can be applied to a variety of clinical and research settings.

What differentiates this technology is its unprecedented sensitivity and specificity for detecting RNase L activity, overcoming the limitations of previous methods that relied on less specific or less sensitive assays such as rRNA degradation analysis. By leveraging the unique chemical ends produced by RNase L and the specificity of adapter ligation combined with junction-specific PCR amplification, the method ensures that only genuine RNase L cleavage events are measured, minimizing background noise from other ribonucleases. Additionally, the approach is highly versatile, compatible with small sample volumes and standard laboratory equipment, and adaptable to a wide range of biological fluids and tissue types. This enables accurate monitoring of immune activation and disease states, offering a valuable tool for diagnostics, therapeutic monitoring, and biomarker discovery in clinical practice.

Benefits

• High sensitivity for detecting RNase L activity in small clinical samples
• High specificity by targeting unique RNase L cleavage products using adapter ligation and junction-specific primers
• Quantitative measurement of immune activation and inflammation through PCR/qPCR amplification
• Applicable to diverse biological samples including blood, plasma, saliva, urine, and tissue biopsies
• Enables monitoring of disease progression and therapeutic efficacy in infections, autoimmune diseases, and other conditions
• Compatible with standard laboratory equipment and workflows
• Facilitates biomarker discovery and spatial mapping of RNase L activity in tissues

Applications

• Infection diagnostics and monitoring
• Autoimmune disease biomarker detection
• Therapeutic response monitoring
• Cancer immune activity profiling
• Inflammation status assessment

Additional info

This methodology quantifies RNase L activity by isolating RNA and ligating synthetic adapters to 3’ ends using RtcB RNA ligase. These fragments, featuring 2’,3’-cyclic or 3’-phosphate groups, are reverse-transcribed into cDNA. PCR amplification follows, utilizing primers specific to the cleavage site and adapter junction. By measuring specific tRNA or Y-RNA cleavage products, this technique provides sensitive biomarkers for monitoring immune responses, infections, and inflammatory diseases.