Validation of chemical inactivation methods for Select Agent compliance using HPAIV and low-pathogenicity influenza A virus in tissues and cultured cells

The US Federal Select Agent program requires that inactivation procedures be validated before treated materials can be removed from biocontainment for downstream use. Although H5 avian influenza viruses are subject to temporary exemption from the Select Agent regulatory requirements, validated inactivation workflows remain critical for safe downstream handling of HPAIV-containing materials. Common treatments, including TRIzol, TRIzol LS, formalin, and ice-cold methanol, are frequently used to facilitate virus inactivation and downstream processing. However, facility-specific inactivation validation is required for Select Agent workflows and for safe handling of HPAIV-containing materials. In this study, HPAIV (H5N1)-infected samples were used to validate inactivation of material generated in cell culture, and low-pathogenicity (H1N1)-infected lung homogenates were used to validate inactivation of animal-derived tissues. Following inactivation, column-based buffer exchange was used to remove cytotoxic inactivants before viability testing. This step did not significantly reduce recovery of infectious virus, supporting the sensitivity of this approach. In inactivation tests, residual infectious virus was assessed by plaque assay and serial blind passages. No infectious virus was detected following any of the tested conditions. These data validate several procedures for inactivating influenza A virus-containing cell cultures, fluids, and tissue samples and provide a framework for facility-specific validation of similar workflows.