Tissue Cytomegalovirus Viral Load and Associated Factors in Pediatric Patients Undergoing Colonoscopy

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Introduction and Objectives Patients diagnosed with Inflammatory Bowel Disease (IBD) carry a significantly elevated risk for opportunistic infections and the reactivation of latent pathogens, most notably Cytomegalovirus (CMV). CMV reactivation in the colonic mucosa can exacerbate underlying IBD, leading to poor clinical outcomes and resistance to standard immunosuppressive therapies. This prospective study was designed with a multi-faceted objective: To evaluate and quantify the CMV viral load within the intestinal tissues of a pediatric cohort, comprising both IBD and non-IBD control groups. To identify specific clinical and biological factors associated with increased CMV detection. To establish potential diagnostic threshold values for CMV viral load in the colonic mucosa, with a primary focus on Ulcerative Colitis (UC) patients-where CMV colitis is most prevalent-as well as patients with other intestinal pathologies. To perform a comparative analysis of diagnostic modalities, specifically evaluating the diagnostic value of histopathology, serum Cytomegalovirus-Polymerase Chain Reaction (CMV-PCR), and tissue CMV-PCR. 2\. Methodology and Procedural Framework The research was conducted at the Pediatric Gastroenterology Endoscopy Unit between May 2022 and March 2024. The study population consisted of pediatric patients undergoing scheduled colonoscopies. Biopsy Protocol: During the endoscopic procedure, two biopsy samples were systematically obtained from the rectal mucosa. For patients presenting with mucosal ulcers, samples were extracted directly from the ulcerated site; in patients with macroscopically normal mucosa, samples were taken from standard rectal tissue. Contamination Prevention: To ensure molecular integrity and prevent cross-contamination, separate forceps were utilized for samples intended for PCR analysis versus those intended for histopathology. Laboratory Analysis: Concurrently, venous blood samples were collected to analyze CMV serology (anti-CMV Immunoglobulin G \[IgG\] / Immunoglobulin M \[IgM\]) and serum CMV-PCR. In cases of IgM positivity, CMV IgG avidity tests were performed to distinguish between primary infection and reactivation. Diagnostic Criteria: A diagnosis of CMV colitis was established based on clinical symptoms, histopathological evidence (Hematoxylin and Eosin \[HE\] staining and Immunohistochemistry \[IHC\]), and a serum CMV-PCR threshold of ≥1000 copies/mL. 3\. Molecular and Histopathological Techniques Deoxyribonucleic Acid (DNA) Extraction: Tissue DNA was extracted using the QIAamp DNA Mini Kit, involving overnight incubation at 56°C for complete tissue digestion. Plasma DNA extraction was automated via the QIAsymphony SP platform. Internal controls were used in every run to validate extraction efficiency. Real-Time Polymerase Chain Reaction (Real-Time PCR): Amplification targeted a 105-bp region of the CMV genome using the Artus CMV QS-RGQ Kit. The assay provided a wide linear range (79.4 to 1×10⁸ copies/mL) with a high analytical sensitivity of 42.5 copies/mL. Results were reported as copies/mL for blood and copies/mg for tissue. Immunohistochemistry (IHC): Four-micrometer tissue sections were analyzed for CMV expression using the Ventana Benchmark XT platform. Nuclear staining was the primary indicator for CMV positivity, with known positive colon mucosa serving as the control. 4\. Statistical Analysis Data were analyzed using IBM SPSS Statistics Version 20.0. The normality of the data was verified using Shapiro-Wilk tests and visualization tools (histograms and Q-Q plots). Comparative Statistics: Categorical variables were assessed via Chi-square tests. Continuous variables were analyzed using Student's t-test (parametric) or the Mann-Whitney U test (non-parametric). Correlations: Relationships between viral loads and clinical variables were evaluated using Spearman's correlation and point-biserial correlation. A p-value of \<0.05 was maintained as the threshold of statistical significance.

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