CASP9 and infection: Caspase overexpression revealed distinct rescue patterns: caspase 3 enhanced WT survival by 13.34% and zfhnf4α−/−-2IS survival by 43.33%, highlighting its critical role in dual-pathogen defense; caspase 9 improved zfhnf4α−/−-2IS survival by 61.67% (from 0% to 61.67%) but had no effect in WT, suggesting a specialized role in compensating for Hnf4α loss during complex infections.