Elsevier

Vaccine

Volume 19, Issue 32, 14 September 2001, Pages 4732-4742
Vaccine

Microsphere translocation and immunopotentiation in systemic tissues following intranasal administration

https://doi.org/10.1016/S0264-410X(01)00220-1Get rights and content

Abstract

With a view to developing improved mucosal immunisation strategies, we have quantitatively investigated the uptake of fluorescent polystyrene carboxylate microspheres (1.1 μm diameter), using histology and fluorescence-activated 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 loaded poly(lactide) (PLA) microspheres (1.5 μm diameter) were assessed at 4, 7 and 11 days. Irrespective of administration vehicle volume (10 or 50 μl), appreciable numbers of fluorescent microspheres were detected within nasal associated lymphoid tissues (NALT) and draining cervical lymph nodes. Nasal administration of the particles suspended in 50 μl volumes of phosphate-buffered saline (PBS) served to deposit the fluorescent microspheres throughout the respiratory tract (P<0.05). In these animals, appreciable particle uptake into the mediastinal lymph node was noted (P<0.05). Also, spleens removed from mice 10 days after fluorescent particle application contained significantly more microspheres if the suspension had been nasally instilled using a 50 μl 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 μl volumes of microparticulated or soluble V antigen. Immunological 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 antigen: upon exposure to V in vitro, splenic T-cells from mice nasally immunised with 50 μl volumes of microspheres incorporated statistically greater (P<0.05) quantities of [3H]thymidine into newly synthesised DNA than did T-cells from cohorts nasally immunised with 50 μl volumes of V in solution. Similarly, significant numbers of anti-V IgG secreting cells were only detected in spleens from mice immunised intramuscularly or nasally with microparticles. 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.

Introduction

Investigations of intranasal (i.n.) immunisation have shown that antigen microencapsulation, or antigen adsorption onto microparticulates, confers a significant adjuvant effect [1], [2]. The exact reason for this immunopotentiating effect is not certain, and the extent to which microparticulates are absorbed across epithelial barriers in the respiratory tract is largely undelineated. It is feasible that M-cells in the nasopharyngeal duct, tonsils and bronchus associated lymphoid tissue (BALT) [3], [4], [5] may facilitate particle uptake across epithelial barriers at these locations. There is also good evidence to indicate that, following transepithelial absorption, microparticle translocation to local immunoresponsive tissues may occur following intranasal delivery [6]. This is strongly supported by the work of Carr et al. [7] and Ridley Lathers et al. [8]. These authors demonstrated the uptake of 1.0 μm fluorescent polystyrene latex and 1.7 μm poly(lactide-co-glycolide) microspheres into rodent nasal associated lymphoid tissues (NALT) and draining cervical lymph nodes after intranasal administration. Prior to these investigations, we demonstrated that nasally delivered 1.0 μm latex microspheres could rapidly enter the blood circulation of experimental animals [9]. To expand these data, we have investigated microparticle uptake and trafficking to systemic compartments of immunological significance, such as thoracic lymph nodes and spleen, following intranasal (i.n.) delivery. Concomitantly the kinetics of the immune response to a microencapsulated recombinant antigen, which is currently undergoing clinical evaluation as an improved vaccine for plague, after i.n. administration, was studied.

Section snippets

Animals

Experimentation strictly adhered to the 1986 Scientific Procedures Act. Female BALB/c mice (25 g, 6-week-old) were used for in vivo studies. Mice were lightly anaesthetised with an inhaled gaseous mixture of 3% (v/v) halothane (RMB Animal Health Ltd., UK) in oxygen (300 cm3 min−1) and nitrous oxide (100 cm3 min−1) for i.n. dosing procedures. Histology and a modification of a method described by Ebel [10] using fluorescence-activated cell sorting (FACS), were used to investigate the in vivo

Histological analysis following intranasal administration of FITC labelled microspheres

We observed a different pattern of particle uptake and distribution in mice nasally dosed with microspheres suspended in 10 and 50 μl volumes of PBS. Also, the tissular distribution of microspheres differed over the 10 day period. Irrespective of administration vehicle volume, many fluorescent particles were observed within excised NALT from 15 min of administration. Mice treated with 10 μl volumes of Fluoresbrite™ spheres showed little evidence of particle translocation to liver and spleen,

Discussion

The histological and cell sorting data gleaned in these experiments corroborate the observations of others [6], [7], [8] that a small percentage of nasally applied microspheres may be translocated into mucosal associated lymphoid tissues and draining lymph nodes. However, here we have identified that microspheres can also access sites that would be expected to result in the induction of systemic immunological responses (spleen). In our model, a prerequisite for significant particle transference

Acknowledgements

We gratefully acknowledge the contribution of Roger Bird (FACS analysis), Derek Stirling, Dr Alan Perris and Dr I.D. Spiers.

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