EDP-420

Infectious-disease experiments test how pathogens interact with host barriers, innate immune receptors, inflammatory signaling, pathogen replication, and tissue injury; pattern-recognition receptors such as TLRs, RIG-I-like receptors, NOD-like receptors, and inflammasomes detect microbial molecules and activate NF-κB, interferon, and cytokine responses. The central hypothesis is that infection severity reflects the balance between pathogen burden and host response: protective inflammation restricts pathogen growth, whereas excessive or mislocalized inflammation contributes to tissue damage and disease phenotype. Unresolved questions include which host pathways are protective versus pathogenic, why some infection models fail to translate to human disease, and which combined readouts best predict clinically relevant infection outcomes.

Selecting a suitable non-mouse animal model is a structured decision based on the research question, required anatomy or physiology, disease mechanism, endpoint feasibility, translational relevance, and ethical justification. Non-mouse models are preferred when mice cannot reproduce key human-relevant features, such as organ size, surgical anatomy, cardiovascular physiology, neuroanatomy, immune features, pharmacology, toxicology, or long-term clinical procedures. Candidate species may include rats, rabbits, guinea pigs, ferrets, zebrafish, pigs, sheep, goats, dogs, cats, horses, and non-human primates, but each species must be justified by its specific scientific advantage rather than convenience or tradition. Unresolved questions include how to quantify translational superiority across species, how to balance increased biological relevance against higher ethical burden, and when human-derived systems or new approach methodologies should replace animal use.

Choosing the right model animal is a validity-driven decision in which the species, strain, sex, age, genetic background, disease-induction method, outcome measures, and welfare burden must match the scientific question rather than laboratory tradition or convenience. A model should be selected by judging face validity, construct validity, and predictive validity: whether it resembles the human phenotype, whether it reproduces relevant mechanisms, and whether results are likely to predict human biology or treatment response. Animal studies often fail to translate because of species differences, weak disease resemblance, poor experimental design, inadequate reporting, publication bias, and underuse of randomization, blinding, and sample-size justification. Unresolved questions include how to rank competing models objectively, how much human-disease complexity must be reproduced for a given objective, and when non-animal systems such as organoids, ex vivo tissue, or computational models