Evaluation of ISCOM matrices clearance from rabbit nasal cavity by gamma scintigraphy

Immune stimulating complexes and/or ISCOM matrices (adjuvant nanoparticles without antigen as a structural component) found potential applications as nasal vaccine adjuvant/delivery system owing to virus like particulate structure and saponin as potent Th1 adjuvant. One of important limiting factor for nasal vaccine delivery is the limited time available for absorption within the nasal cavity due to mucociliary clearance. In this report the clearance rate of ISCOM matrices from nasal cavity of rabbit was determined by gamma scintigraphy. ISCOM matrices were radiolabelled with 99mTc by direct labelling method using stannous chloride as a reducing agent. 99mTc labelled ISCOM matrices were administered into the nostril of female New Zealand rabbits and 1 min static views were repeated each 15 min until 4 h. Clearance rate of ISCOM matrices from nasal cavity was calculated after applying the physical decay corrections. The mean labelling efficiency for ISCOM matrices were calculated as ∼58.4%. ISCOM matrices showed slower clearance rate compared to sodium pertechnetate control solution (p < 0.005) from nasal cavity that may be due to particulate and hydrophobic characters of ISCOM particles even though it was also cleared within 4 h from nasal cavity. Mucoadhesive ISCOM formulations that retain in nasal cavity for longer duration of time may reduce the dose/frequency of vaccine for nasal immunization.