Impact of -20 C° cryopreservation on serum factors from schistosomiasis patients at different storage durations: insights into serum bio-banking.

Abstract

It is indefinite for research applications if prolonged freeze-stored serum from Schistosoma-infected patients is useful. We assessed - 20 °C freezing as a rapid and inexpensive method. A longitudinal cohort study with staggered follow-up periods evaluated the impact of cryopreservation on serum residues from 24 Schistosoma-infected Egyptian patients. Fresh serums were collected in March 2022 and assessed by the indirect haemagglutination test for Schistosoma immunoglobulin titrations and calorimetric assays for ALT, AST, total serum protein, Na⁺, K⁺, Ca⁺⁺, and Mg⁺⁺ (baseline values). Sera were then frozen and categorized into 4 groups (6 patients each) according to freezing duration; 3 months (group-1), 6 months (group-2), 9 months (group-3), and 12 months (group-4). Re-evaluation was performed on the Schistosoma immunoglobulin recovery rates and all other serum chemical factors. Baseline assessment showed increased mean values of Schistosoma immunoglobulins, ALT, AST, and proteins; yet, Ca⁺⁺, Na⁺, and K⁺ were reduced. Mg⁺⁺ showed normal values. Compared with the baselines, - 20 °C freezing showed significant deviations and increased percentage change in Schistosoma immunoglobulin titers, ALT, AST, K⁺, and Na⁺ at different time intervals of archiving (p-value ≤ 0.05). Evaluating serum factors interactions post-thawing revealed that AST correlated positively with ALT and Mg⁺⁺ sera levels whereas Ca⁺⁺ negatively correlated with Na⁺ and Schistosoma antibody titer. Analyzing baselines revealed that the parasite alters levels of immunoglobulin, ALT, AST, proteins, Ca⁺⁺, Na⁺, and K⁺. - 20 °C cryopreservation did not guarantee the stability of all tK⁺hese serum parameters. In addition, some serum factors appeared to interact together. Assessing the efficacy of - 20 °C freezing on the next-generation sequencing is recommended.