Viral fragments in the urine proteome: New clues to the cause of fever

[Background]Fever of unknown origin refers to a medical condition where the cause of the fever is not yet clear. This condition is common in various potential diseases and usually requires detailed examination and testing to determine the specific cause. No one has ever looked for the cause of fever in urine proteomics, and this study provides clues and diagnostic evidence for patients with fever of unknown origin through urine proteomics analysis. [Methods]We attempted virus-wide database searching for the first time in urine samples, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze urine proteins from febrile patients. Virus protein fragments were identified and retrieved. [Results]In urine samples, we detected specific peptide segments from various viruses including monkeypox virus, saliva virus A, human herpesvirus 8 type P, Middle East respiratory syndrome-related coronavirus, rotavirus A, foot-and-mouth disease virus (strain NZ2), human herpesvirus 2 (strain HG52), human adenovirus E serotype 4, influenza A virus, human coronavirus NL63, influenza B virus (strain W3), Nipah virus, and hepatitis C virus genotype 2k (isolate VAT96), among others. Several viruses showed significantly higher detection levels in febrile patients compared to controls, with saliva virus A showing an increase by over 4200-fold, and multiple virus proteins increased by more than 20-fold. It is noteworthy that the overall protein retrieval error rate was less than 1%, and the individual protein retrieval error rate for each sample was less than 5%, ensuring highly reliable protein retrieval results with a probability of error across all proteins of only 1.2xe-17. [Conclusion]Reliable virus protein fragments can be retrieved from urine proteomics, providing clues for febrile patient investigation and potentially applicable to the exploration of any unknown diseases. By adopting our method, there is no need to know in advance what specific viruses are contained in the sample, as long as the information of these viruses has been stored in the virus database, comprehensive and extensive virus retrieval can be achieved. This method significantly expands the coverage of virus detection and improves the flexibility and efficiency of detection.