(T1330-08-49) Biodistribution and Prolonged Respiratory Retention of Fluorescently Labeled IgM Antibody Intranasally Administered in Mice

Purpose: This study investigates whether intranasal administration of a fluorescently labeled pan-influenza neutralizing IgM antibody (F045-092-AF750) achieves targeted biodistribution in the respiratory tract of mice, with prolonged retention in nasal cavities and lungs compared to non-respiratory tissues, to enhance localized antiviral protection against influenza A virus (IAV).

Methods: F045-092 IgM was conjugated with Alexa Fluor 750 (AF750), purified via dialysis, gel filtration, and Amicon centrifugation (MWCO 10 kDa). Female CD-1 mice (n=4, 6-8 weeks old) received 1.2 mg/kg of F045-092-AF750 intranasally under 2% isoflurane anesthesia. Biodistribution was assessed using in vivo near-infrared fluorescence imaging (IVIS Spectrum CT) with 2D fluorescence and 3D computed tomography-fluorescence tomography (CT-FLT) at time points from 5 minutes to 168 hours post-administration (Ex=740 nm, Em=800 nm, auto-exposure). Ex vivo organ imaging was performed at 24, 48, 96, and 168 hours to quantify fluorescence in blood, brain, heart, lung, liver, spleen, kidney, and nasal cavity.

Results: In vivo imaging showed enriched fluorescence in nasal cavities (~8×10^8 [p/s/cm²/sr]/[µW/cm²]) and lungs (~4×10^7 [p/s/cm²/sr]/[µW/cm²]) at 24-96 hours, persisting up to 168 hours. Ex vivo imaging confirmed predominant antibody localization in the nasal cavity (up to 5×10^8 [p/s/cm²/sr]/[µW/cm²]) and lungs (up to 2×10^7 [p/s/cm²/sr]/[µW/cm²]) at 24-96 hours, with minimal signals in blood and non-respiratory organs ( < 5×10^6 [p/s/cm²/sr]/[µW/cm²]). 3D CT-FLT imaging validated precise respiratory tract targeting.

Conclusion: Intranasal administration of F045-092-AF750 IgM achieves targeted biodistribution with prolonged nasal cavity and lungs retention, with minimal systemic exposure, supporting its potential for localized antiviral protection against IAV. Future studies will focus on quantitative pharmacokinetic and biodistribution for human translation.

References: Ramesh AK, Sivaccumar JP, Ye X, Yang L, Guo H, Chin CN, Ha S, Shiver JW, Strohl WR, Xu Y, Du H, Zhou T, Zhang N, Xu K, Liu X, Fu TM, An Z. An intranasally administered IgM protects against antigenically distinct subtypes of influenza A viruses. Nat Commun. 2025 Apr 29;16(1):4025. doi: 10.1038/s41467-025-59294-0. PMID: 40301359; PMCID: PMC12041195.