Redefining post-xenotransplantation surveillance: leveraging metagenomic next-generation sequencing to discriminate true pathogen replication from microchimerism-induced false positives.

Infection-related risks remain a major concern in xenotransplantation and require continued vigilance as the field progresses toward clinical application. Xenozoonosis is of particular concern, especially in relation to donor-derived porcine viruses such as porcine endogenous retroviruses, porcine cytomegalovirus, porcine lymphotropic herpesviruses, and porcine circoviruses, which are considered significant targets for donor screening and recipient surveillance in clinical xenotransplantation trials. With advances in diagnostic technologies, metagenomic next-generation sequencing may facilitate the detection of unexpected or previously unrecognized pathogens. However, positive molecular findings for donor-derived pathogens should be interpreted cautiously to distinguish microchimerism from true infection in the recipient. Addressing this diagnostic challenge will require complementary assays capable of demonstrating viral integration and replication in recipient-derived human cells, together with expert interpretation by clinicians in the appropriate clinical context. Detailed and tailored surveillance protocols incorporating these advanced methodologies should be developed and validated through well-designed clinical trials, with the resulting evidence guiding their standardization by relevant professional societies and regulatory authorities. These efforts will be essential for the safe and responsible clinical implementation of xenotransplantation.