Serum Exosomal miRNA Signatures Enable Early Diagnosis of Feline Infectious Peritonitis

Researchers at Ganzhou Vocational and Technical College have identified a specific blood-borne microRNA signature inside serum exosomes that distinguishes cats with feline infectious peritonitis (FIP) from healthy animals, offering a non-invasive route to earlier diagnosis.

In Plain English: The Clinical Takeaway

• What was found: Scientists discovered that tiny membrane-bound vesicles in the blood, called exosomes, carry a distinct cargo of microRNAs in cats suffering from FIP compared to healthy felines.
• Why it matters: Traditional diagnostics struggle to differentiate between harmless feline coronavirus infections and the lethal virus that causes FIP, particularly in non-exudative cases where no fluid accumulates.
• How it works: A simple five-milliliter blood draw isolates these exosomes, allowing a three-biomarker panel to screen for the disease.

Molecular Cargo Shift Replaces Quantity Counts

Feline infectious peritonitis emerges when a common, benign gut coronavirus mutates inside a host cat, transforming into a pathogen that sparks runaway inflammation, fluid accumulation, and progressive organ failure. Because early signs mirror numerous other conditions, veterinarians often confirm the disease only at advanced stages. Investigating whether a reliable indicator circulates in peripheral blood, researchers led by Hongxia Gu and Huisheng Wu enrolled 32 cats with confirmed FIP—evenly split between exudative and non-exudative forms—alongside 20 age- and breed-matched healthy controls verified free of coronavirus infection.

The research team isolated nanoscale vesicles known as exosomes from five-milliliter blood samples using differential ultracentrifugation, adhering to protocols set by the International Society for the Study of Extracellular Vesicles. Transmission electron microscopy and nanoparticle tracking analysis revealed particle concentrations of roughly 3.1 by 10¹⁰ per milliliter in the FIP cohort and 2.8 by 10¹⁰ in controls, a difference that proved statistically insignificant. Western blotting confirmed strong expression of exosome marker proteins CD63 and TSG101. The data demonstrated that FIP does not alter the total quantity of circulating exosomes, but rather reshapes the specific microRNA molecules encapsulated within them.

High-Throughput Sequencing Isolates Five Core Regulators

High-throughput sequencing on the Illumina HiSeq 4000 platform screened 489 microRNAs across the collected samples, flagging 23 that showed statistically significant differential expression between diseased and healthy cats. Five particular biomarkers emerged from the data. Three molecules were upregulated in FIP cases: miR-21-5p, miR-155-5p, and miR-486-5p. Two molecules were downregulated: miR-423-5p and miR-200c-3p. Quantitative reverse transcription PCR validated these sequencing results with a correlation coefficient of 0.92, showing miR-21-5p elevated roughly 14.3-fold while miR-423-5p dropped to about 22 percent of control levels.

Bioinformatic pathway analysis connected the upregulated microRNAs to NF-kappa-B and toll-like receptor signaling pathways, which drive the inflammatory cascades characteristic of FIP pathology. Conversely, the downregulated miR-423-5p tied into the PI3K-Akt pathway, reflecting the immunosuppressive state often observed during late-stage disease progression. Crucially, these expression patterns remained consistent across both exudative and non-exudative clinical forms of FIP, showing coefficients of variation below 15 percent across all five markers.

MicroRNA Marker	Expression Trend	Associated Pathway	Diagnostic Performance (AUC)
miR-21-5p	Upregulated (~14.3x)	NF-kappa-B / TLR Signaling	0.82
miR-423-5p	Downregulated (~22% of control)	PI3K-Akt Pathway	0.75
Combined Panel	Multi-Marker Model	Logistic Regression	0.93

Logistic Regression Model Surpasses Traditional Markers

To convert the sequencing data into a practical clinical tool, the investigators constructed a logistic regression model combining miR-21-5p, miR-155-5p, and miR-423-5p. Receiver operating characteristic (ROC) analysis yielded an area under the curve (AUC) of 0.93, with a 95 percent confidence interval spanning from 0.86 to 0.98. The combined panel achieved 88.6 percent sensitivity and 91.2 percent specificity, delivering positive and negative predictive values of 89.4 percent and 90.7 percent respectively.

This multi-marker approach significantly outperformed individual microRNAs, which registered AUC values between 0.75 and 0.82. Furthermore, the exosomal panel outpaced alpha-1-acid glycoprotein—a conventional FIP biomarker with an AUC of 0.75—improving overall diagnostic accuracy by roughly 24 percent. Subgroup evaluations confirmed reliable performance across clinical presentations, yielding an AUC of 0.91 for exudative disease and 0.89 for non-exudative disease. These findings, published in Experimental Biology and Medicine, point toward potential liquid biopsy applications that could widen the therapeutic window for nucleoside analogue antiviral treatments like GS-441524.

Contraindications & When to Consult a Doctor

While this liquid biopsy framework promises screening, veterinary clinicians must note current technical limitations. The diagnostic model has not yet been validated against cats carrying asymptomatic feline enteric coronavirus (FECV) infections, which represents a primary challenge in routine practice. Practitioners should not rely solely on serum microRNA signatures when kittens present with maternal antibody interference. Veterinary consultation and comprehensive clinical staging remain essential whenever systemic inflammatory symptoms arise.

References

• Gu, H., & Wu, H. (2026). The value of serum exosomal miRNA signature profiles for the early diagnosis of feline infectious peritonitis. Experimental Biology and Medicine, 251, Article 10915. https://doi.org/10.3389/ebm.2026.10915