Preparation of Poly-Lactic-Co-Glycolic Acid Nanoparticles in a Dry Powder Formulation for Pulmonary Antigen Delivery

One of the key requirements for successful vaccination via the mucosa is particulate antigen uptake. Poly-lactic-co-glycolic acid (PLGA) particles were chosen as well-known model carriers and ovalbumin (OVA) as the model antigen. Aiming at application to the respiratory tract, which allows direct interaction of the formulation with the mucosal immune system, this work focuses on the feasibility of delivering the antigen in a nanoparticulate carrier within a powder capable of pulmonary delivery. Further requirements were adequate antigen encapsulation in order to use the characteristics of the particulate carrier for (tunable) antigen release, and capability of the production process for industrialisation (realisation in industry). For an effective particulate antigen uptake, nanoparticles with a size of around 300 nm were prepared. For this, two production methods for nanoparticles, solvent change precipitation and the double emulsion method, were evaluated with respect to antigen incorporation, transfer to a dry powder formulation, redispersion and antigen release characteristics. A spray drying step was included in the production procedure in order to obtain a respirable powder with an aerodynamic particle size of between 0.5 and 5 μm. The dried products were characterised for particle size, dispersibility and aerodynamic behaviour, as well as for immune response and cytotoxicity in cell culture models. It could be shown that the double emulsion method is suitable to prepare nanoparticles (270 nm) and to incorporate the antigen. By modifying the production method to prepare porous particles, it was possible to obtain an acceptable antigen release while maintaining an antigen load of about 10%. By the choice of polyvinyl alcohol as a stabiliser, nanoparticles could be dried and redispersed without further excipients and the production steps were capable of realisation in industry. Aerodynamic characteristics were good with a mass median aerodynamic diameter of 3.3 µm upon dispersion from a capsule-based inhaler.

Technological Approaches for Improving Vaccination Compliance and Coverage

Vaccination has been well recognised as a critically important tool in preventing infectious disease, yet incomplete immunisation coverage remains a major obstacle to achieving disease control and eradication. As medical products for global access, vaccines need to be safe, effective and inexpensive. In line with these goals, continuous improvements of vaccine delivery strategies are necessary to achieve the full potential of immunisation. Novel technologies related to vaccine delivery and route of administration, use of advanced adjuvants and controlled antigen release (single-dose immunisation) approaches are expected to contribute to improved coverage and patient compliance. This review discusses the application of micro- and nano-technologies in the alternative routes of vaccine administration (mucosal and cutaneous vaccination), oral vaccine delivery as well as vaccine encapsulation with the aim of controlled antigen release for single-dose vaccination.

Studies on Tissue Factor Pathway Inhibitor Antigen Release by Bovine, Ovine and Porcine Heparins Following Intravenous Administration to Non-Human Primates

Unfractionated heparin (UFH) is a sulfated glycosaminoglycan that consists of repeating disaccharides, containing iduronic acid (or glucuronic acid) and glucosamine, exhibiting variable degrees of sulfation. UFHs release tissue factor pathway inhibitor (TFPI) which inhibits the extrinsic pathway of coagulation by inactivating factor Xa and the factor VIIa/TF complex. Most heparins used clinically are derived from porcine intestinal mucosa however, heparins can also be derived from tissues of bovine and ovine origin. Currently there are some concerns about the shortage of the porcine heparins as they are widely used in the manufacturing of the low molecular weight heparins (LMWHs). Moreover, due to cultural and religious reasons in some countries, alternative sources of heparins are needed. Bovine mucosal heparins (BMH) are currently being developed for re-introduction to the US market for both medical and surgical indications. Compared to porcine mucosal heparin (PMH), BMH exhibits a somewhat weaker anti-coagulant activity. In this study, we determined the TFPI antigen level following administration of various dosages of UFHs from different origins. These studies demonstrated that IV administration of equigravemetric dosages of PMH and ovine mucosal heparin (OMH) to non-human primates resulted in comparable TFPI antigen release from endothelial cells. In addition, the levels of TFPI were significantly higher than TFPI antigen levels observed after BMH administration. Potency adjusted dosing resulted in comparable TFPI release profiles for all 3 heparins. Therefore, such dosing may provide uniform levels of anticoagulation for the parenteral indications for UFHs. These observations warrant further clinical validation in specific indications.