Microsphere translocation and immunopotentiation in systemic tissues following intranasal administration

With a view to developing improved mucosal immunisation strategies, we have quantitatively investigated the uptake of fluorescent polystyrene carboxyl ate microspheres (1.1 mum diameter), using histology and fluorescence-activ ated cell sorting, following intranasal delivery to BALB/c mice. To-qualify these biodistribution data, antigen specific memory and effector responses in the spleens of mice immunised nasally with Yersinia pestis V antigen lo aded poly(lactide) (PLA) microspheres (1.5 mum diameter) were assessed at 4 , 7 and 11 days. Irrespective of administration vehicle volume (10 or 50 mu l), appreciable numbers of fluorescent microspheres were detected within na sal associated lymphoid tissues (NALT) and draining cervical lymph nodes. N asal administration of the particles suspended in 50 mul volumes of phospha te-buffered saline (PBS) served to deposit the fluorescent microspheres thr oughout the respiratory tract (P < 0.05). In these animals, appreciable par ticle uptake into the mediastinal lymph node was noted (P < 0.05). Also, sp leens removed from mice 10 days after fluorescent particle application cont ained significantly more microspheres if the suspension had been nasally in stilled using a 50 mul volume (P < 0.05). Appreciable memory (and effector from day 7) responses were detected in mediastinal lymph nodes removed from mice immunised nasally with 50 mul volumes of microparticulated or soluble V antigen. Immuno logical responses in splenic tissue removed 7 days after intranasal immunisation corroborated the thesis that the spleen can act as an inductive site following bronchopulmonary deposition of particulated an tigen: upon exposure to V in vitro, splenic T-cells from mice nasally immun ised with 50 mul volumes of microspheres incorporated statistically greater (P < 0.05) quantities of [H-3]thymidine into newly synthesised DNA than di d T-cells from cohorts nasally immunised with 50 mul volumes of V in soluti on. Similarly, significant numbers of anti-V IgG secreting cells were only detected in spleens from mice immunised intramuscularly or nasally with mic roparticles. These immunological and biodistribution data support the tenet that, following an appropriate method of mucosal delivery. microparticles can translocate to tissues in the systemic compartment of the immune system and thence provoke immunological reactions therein. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.