H. O. Alpar

Immune Response to Nasal Delivery of Antigenically Intact Tetanus Toxoid Associated with Poly(l-lactic acid) Microspheres in Rats, Rabbits and Guinea-pigs

Abstract— Tetanus toxoid was adsorbed onto poly(l‐lactic acid) microspheres. Analyses by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis and Western blotting suggest that the formulation procedure does not affect the stability or the antigenic properties of the protein. After nasal administration to guinea‐pigs, the resulting preparation enhanced the immune response to the tetanus toxoid when compared with the free antigen. The increase in systemic immunoglobulin G titre was almost immediate in the group treated with the adsorbed tetanus toxoid (time zero, 140; week 2, 1550; week 4, 2760), reaching 36000 two weeks after the booster (week 7), whereas the free antigen produced an immune response similar to that found in non‐treated animals. In a parallel experiment, latex particles of a similar size to poly(l‐lactic acid) microspheres, administered to both rats and rabbits, were detected in the blood stream. These findings with tetanus toxoid demonstrate the use of microsphere delivery systems for nasal application of antigens. These had a profound effect on the immune response, and indicate possibilities for overcoming some of the barriers to drug absorption in general.

Nasal Delivery of Vaccines

Only relatively recently the significance of inducing not only systemic immunity but also significant local immunity at susceptible mucosal surfaces has become appreciated. A new field of mucosal immunity has been established as information accumulates on mucosal-associated lymphoid tissue (MALT) and on its role in both local and systemic immune responses. This review describes the formation of vaccines to be delivered to one of MALT components, i.e. the nasal-associated lymphoid tissue (NALT), which bears some similarities with the Peyers patches of the intestine. The association of antigens with adjuvants and particulate carriers such as microparticles, nanoparticles and liposomes is emphasised.

The transport of microspheres from the gastro-intestinal tract to inflammatory air pouches in the rat

Abstract— The distribution of latex microspheres (1·1 μ diam) has been investigated in‐vivo, as a potential passive targeted system for the treatment of inflammation. Microspheres administered orally were found in the circulation and in inflamed tissues and exudates of inflammatory air pouches in rats. Oral absorption was also found in a rabbit. Particles administered directly into the circulation also penetrated into the air pouch tissues and fluids. The possibility of using microspheres as a passive targeted system for the treatment of inflammation is discussed.

Drug-Delivery by Ion-Exchange: Part IIII: Interaction of Ester Pro-Drugs of Propranolol with Cationic Exchange Resins

AbstractThe interaction of a series of O-n-acyl propranolol prodrugs with strong cation exchange resins is reported and various variables which control loading and release profiles have been investigated. pH has little practical effect on the loading efficiency under the conditions used but standardisation of experimental details for the measurement of in vitro liberation profiles must be undertaken. In particular, stirring speeds of 200-300 rpm were necessary to ensure the independence of release profile and agitation. Additionally, the dissolution medium may not provide sink conditions throughout the full dissolution process if pH variation does not take into account solubility differences between analogues. Ionic strength also influences release rates and attempts to examine the effects of pH must also control this variable. The proportion of cross-linking agent in the resin plays an important role. Increasing the cross-linking delays considerably the release of drug from the matrix and is a useful par...

A comparative study on the pulmonary delivery of tobramycin encapsulated into liposomes and PLA microspheres following intravenous and endotracheal delivery

The use of carriers to deliver tritiated tobramycin via intravenous and endotracheal routes to the lungs was investigated. Pulmonary, renal and vascular distribution were monitored at 6 and 24 h. The results indicated a significant difference (p < 0.05) between free drug, which is rapidly disseminated to other organs, specifically kidney, and liposomal and microcapsular tobramycin which was primarily retained in the lungs. Renal drug levels of intravenously delivered microcapsular tobramycin were significantly higher than those produced by liposomal administration at 6 (p ? 0.025) and 24 h (p ? 0.05). Liposomes however, produced pulmonary levels three times higher than those of the free drug both at 6 (p ? 0.025) and 24 h (p ? 0.025). At 24 h renal drug levels following endotracheal delivery were lower for both encapsulated forms than for the free drug (p ? 0.005). Conversely, pulmonary drug levels were higher following encapsulated drug administration compared to those following free drug delivery at 24 h (p ? 0.005). These results demonstrate that tobramycin can be retained in the lung by means of liposomal and microencapsulated delivery systems after endotracheal delivery.

Effectiveness of liposomes as adjuvants of orally and nasally administered tetanus toxoid

Abstract Tetanus toxoid was incorporated into liposomes of equimolar concentrations of distearoyl phosphadylcholine (DSPC) and cholesterol. We investigated the non-parenteral delivery of free or liposome entrapped tetanus toxoid to guinea pigs and measured the subsequent IgG anti-tetanus-antibody response, using an ELISA. Liposome formulation significantly improved the immune response when compared to the free antigen when delivered via the nasal, oral and i.m. routes. However, 10 × concentration of tetanus toxoid entrapped in DSPC introduced mucosally (nasally and orally) was necessary to produce an IgG antibody titre similar to those obtained via the i.m. delivery. This study suggests that liposomes, administered through the oral and nasal routes, have considerable potential as mucosal adjuvants and warrant further investigation.

Generation of protective immune responses to plague by mucosal administration of microsphere coencapsulated recombinant subunits

We have investigated noninvasive immunization to plague. Recombinant subunit antigens, F1 and V from Yersinia pestis, were coencapsulated in biodegradable poly(L100 LD(50s) inhalational challenge with virulent Y. pestis. These data expand on previous findings from our laboratories, providing further insight into the mechanics of safeguarding mice from plague through nasal immunization. Further, these results demonstrate that in a murine model, solid protection from pneumonic plague can be engendered by two intranasal administrations of appropriately formulated recombinant proteins.

Tissue distribution of radioactivity following intranasal administration of radioactive microspheres

The aim of this study was to increase understanding of the kinetics of microparticle distribution and elimination following intranasal application. To do this we investigated the in‐vivo distribution of radioactivity following intranasal instillation of scandium‐46 labelled styrene‐divinyl benzene 7‐μm‐diameter microspheres. Groups of BALB/c mice received 0.250 mg (47.5 kBq) particles suspended in either 50‐μl or 10‐μl volumes of phosphate buffered saline. The in‐vivo distribution of radioactivity was influenced by the volume of liquid that was used to instil the microsphere suspension. Comparatively large (50 μl) administration vehicle volumes resulted in substantial bronchopulmonary deposition (∼ 50% of administered dose). Intranasal instillation of microspheres suspended in 10‐μl volumes tended to restrict particle deposition initially to the nasal cavity. For both administration vehicle volumes tested, the radioactivity per unit mass of excised nasal‐associated lymphoid tissue (NALT) was found to be consistently elevated relative to other tissues. This corroborates the findings of other workers who have previously identified NALT as an active site of microparticle accumulation following intranasal application. Elimination via the alimentary canal was the principal fate of intranasally applied radiolabeled material. No significant concentration of radioactivity within excised gut‐associated lymphoid tissue (GALT) (Peyers patches) was noted. At latter time points we observed, in mice that received the 50‐μl volume particle suspension nasally, accumulation of potentially relevant quantities of radioactivity in the liver (0.3% after 576 h) and spleen (0.04% after 576 h). Thus, our data corroborate the notion that epithelial membranes in the lung are probably less exclusive to the entry of microparticulates into systemic compartments than are those mucosae in the gastrointestinal tract or nasopharynx. This effect may contribute to the effectiveness of pulmonary delivered antigen‐loaded microparticles as humoral immunogens.

Biodegradable microparticles with different release profiles: effect on the immune response after a single administration via intranasal and intramuscular routes.

In the development of single‐dose microparticulate vaccines, identification of the type of protein release profile required to elicit high and sustainable immune responses is important. Microparticles exhibiting different protein release profiles (continuous, pulsatile and plateau) were made by solvent evaporation or solvent extraction methods from biodegradable polymers encapsulating the model antigen, bovine serum albumin (BSA). The immune responses obtained after a single intranasal or intramuscular administration of microparticles were determined, and also after a subcutaneous boost after 11 months.

Immunological aspects of polymer microsphere vaccine delivery systems.

In vitro studies using dendritic cells have identified that microencapsulated antigens are taken up and processed differently as compared with soluble proteins, and these findings have been reviewed. Similarly, in vivo, it is evident that microencapsulated materials have different properties in terms of uptake and trafficking. Intranasal (IN) instillation of encapsulated protective antigen resulted in a significant increase in the percentage of activated CD4+ and B-cells in the spleens of immunised mice, whereas IN instillation of soluble antigen failed to do so. This corroborates earlier findings concerning the uptake and trafficking of microparticles following bronchopulmonary administration. These data support the tenet that microencapsulation serves to modify the uptake, trafficking and processing of antigens.