Optimised murine model of influenza-induced respiratory sepsis for studying acute kidney injury

BACKGROUND: Viral respiratory sepsis, driven by influenza and COVID-19, is increasingly prominent clinically. However, there is a lack of preclinical models that reliably replicate its associated acute kidney injury (AKI), a major contributor to morbidity and mortality. To address this gap, we refined an established model of influenza-induced respiratory sepsis by administering graded intranasal H1N1 A/PR/8/34 doses (3.7 × 10¹, 3.7 × 10³, and 3.7 × 10⁴ TCID₅₀) in male BALB/c mice. We defined humane endpoints at ≥ 30% body weight loss, monitored clinical severity, weight, and glycaemia daily for 14 days, and assessed multi-organ dysfunction via serum biochemistry, histopathology, renal qPCR, and longitudinal serum neutrophil gelatinase-associated lipocalin (NGAL) ELISA. RESULTS: The 3.7 × 10⁴ TCID₅₀ dose yielded 66.7% mortality by day 8, with a peak clinical score (MSS) of 10, > 30% weight loss, and hypoglycaemia (blood glucose < 70 mg/dL). Infected mice exhibited dose-dependent multi-organ dysfunction, with substantial elevations in serum creatinine (median: 204 [IQR: 142-600] µmol/L), bilirubin (40.62 [IQR: 29.3-124.9] µmol/L), and creatine phosphokinase (CPK) (9822 [IQR: 1,272-11,352] U/L). Renal NGAL expression increased up to 7-fold, aligning with rising serum creatinine levels and histopathological evidence of glomerular enlargement and tubular degeneration. Serum NGAL showed early elevation (up to 4,990 ng/mL on day 2) in severely affected mice, with levels remaining 5.7-7.6-fold higher than sham controls through days 4-8. CONCLUSIONS: This exploratory study describes an optimised murine model of influenza-induced respiratory sepsis that develops biochemical and histopathological evidence of AKI. Early elevation of serum NGAL was observed in severely affected animals, supporting its potential as a candidate early biomarker. The model provides a useful platform for further mechanistic and therapeutic investigation in viral respiratory infection-associated AKI.