Viral Biomarker Detection and Validation Using MALDI Mass Spectrometry Imaging (MSI)

Area of Science:

• Biomarker discovery
• Mass spectrometry imaging
• Virology

Background:

• Matrix-assisted laser desorption/ionization (MALDI) imaging, often reliant on Time of Flight (TOF) instruments, typically cannot perform fragmentation during tissue imaging.
• This limitation necessitates using MS1 values for peptide identification, hindering detailed analysis.
• A new hybrid bioinformatic/image-based method was developed to overcome these limitations.

Purpose of the Study:

• To develop and validate a novel method for identifying and validating viral biomarkers using MALDI TOF mass spectrometry imaging.
• To enable confident viral peptide identification without tandem mass spectrometry (MS/MS).
• To leverage existing MALDI TOF instrumentation for viral diagnostics.

Main Methods:

• Formalin-Fixed Paraffin-Embedded (FFPE) mouse samples were analyzed using MALDI mass spectrometry imaging.
• Viral peptide identification involved extracting ion images, performing Peptide Mass Fingerprint (PMF) searches against viral and mouse databases.
• Correlational analysis confirmed pixel-by-pixel colocalization and intensity of identified viral peptides.

Main Results:

• Fourteen viral peptides were successfully identified with significant PMF scores.
• A high correlational result (>0.79) confirmed viral presence and distinguished viral peptides from background mouse proteins.
• The method demonstrated effective viral biomarker identification and validation.

Conclusions:

• The developed hybrid approach enables confident identification of viral proteins using MALDI TOF/TOF instrumentation.
• This method overcomes the inability of TOF-based MALDI imaging to perform fragmentation during tissue analysis.
• It offers a powerful tool for viral diagnostics and biomarker discovery without requiring advanced MS/MS capabilities.