Sara Gómez

Bioadhesive properties of pegylated nanoparticles

The design of bioadhesive nanoparticles (NPs) for targeting specific sites within the gut remains a major challenge. One possible strategy to solve this problem may be the use of pegylated NPs. In general, these carriers display different bioadhesive properties to nondecorated NPs. Thus, pegylated NPs show a higher ability to interact with the small intestine mucosa rather than with the stomach. However, the type of surface conformation of polyethylene glycol chains appears to have a great influence on the behaviour of these NPs. Theoretically, the traditional ‘brush’ polyethylene glycol corona would facilitate the penetration of the pegylated particles through the mucus layer and the subsequent adhesive interaction with the mucosa, which would promote their absorption by intestinal enterocytes. On the contrary, pegylated NPs with a ‘loop’ conformation would increase the time of residence of the adhered fraction of particles in the mucosa.

Co-encapsulation of an antigen and CpG oligonucleotides into PLGA microparticles by TROMS technology

It seems well established that CpG oligonucleotide Th1-biased adjuvant activity can be improved when closely associated with a variety of antigens in, for example, microparticles. In this context, we prepared 1-micron near non-charged poly(lactic-co-glycolic) acid (PLGA) 502 and PLGA 756 microparticles that loaded with high-efficiency antigen (50% ovalbumin (OVA), approximately) into their matrix and CpG-chitosan complexes (near to 20%) onto their surface maintaining OVA and CpG integrity intact. In the intradermal immunization studies, whereas OVA microencapsulated into PLGA 756 alone induced a strong humoral immune response assisted by a very clear Th1 bias (IgG2a/IgG1=0.88) that was decreased by CpG co-delivery (IgG2a/IgG1=0.55), the co-encapsulation of CpG with OVA in PLGA 502 particles significantly improved the antibody response and isotype shifting (IgG2a/IgG1=0.73) in comparison with mice immunized with OVA-loaded PLGA 502 (IgG2a/IgG1=0). This improvement was not correlated with the cellular immune response where the effect of co-encapsulated CpG was rather negative (2030 and 335 pg/mL IFN-gamma for OVA PLGA 502 and OVA CpG PLGA 502, respectively). These results underscore the critical role of polymer nature and microparticle characteristics to show the benefits of co-encapsulating CpG motifs in close proximity with an antigen.

A novel nanoparticulate adjuvant for immunotherapy with Lolium perenne

Specific immunotherapy implies certain drawbacks which could be minimized by the use of appropriate adjuvants, capable of amplifying the right immune response with minimal side effects. In this context, previous studies of our group have demonstrated the adjuvant capacity of Gantrez AN nanoparticles, which can effectively enhance the immune response. In this work, two types of nanoparticles (with and without LPS of Brucella ovis as immunomodulator) with encapsulated Lolium perenne extract are tested in a model of sensitized mice to this allergenic mixture. The results we obtained showed that Lolium-Gantrez nanoparticles with LPS of B. ovis were able to induce significative Th1 responses, characterized by the IgG(2a) isotype. Furthermore, in the challenge experiment of the sensitized mice, differences in the mortality rate and in the mMCP-1 levels were found between the treated groups and the control. Under the experimental conditions of this model of pre-sensitized mice to L. perenne, Gantrez AN nanoparticles appeared to be a good strategy for immunotherapy.

Allergen immunotherapy with nanoparticles containing lipopolysaccharide from Brucella ovis.

The adjuvant and protective capacity against anaphylactic shock of the association between rough lipopolysaccharide of Brucella ovis (LPS) coencapsulated with ovalbumin (OVA), as a model allergen, in Gantrez AN nanoparticles was investigated. Several strategies were performed in order to study the adjuvant effect of the LPS either encapsulated or coating the nanoparticles. OVA, as well as LPS, was incorporated either during the manufacturing process (OVA-encapsulated or LPS-encapsulated nanoparticles, respectively) or after the preparation (OVA-coated or LPS-coated nanoparticles, respectively). After the administration of 10 microg of OVA incorporated in the different formulations, all the nanoparticles, with or without LPS, were capable of amplifying the immune response (IgG(1) and IgG(2a)). However, in a model of sensitized mice to OVA, the formulation with OVA and LPS-entrapped inside the nanoparticles administered intradermally in three doses of 3 microg of OVA each was the only treatment that totally protected the mice from death after a challenge with an intraperitoneal injection of OVA. In contrast, the control group administered with OVA adsorbed onto a commercial alhydrogel adjuvant showed 80% mortality. These results are highly suggestive for the valuable use of Gantrez nanoparticles combined with rough LPS of B. ovis in immunotherapy.

Co-Delivery of Ovalbumin and CpG Motifs into Microparticles Protected Sensitized Mice from Anaphylaxis

Background: Two major drawbacks of current subcutaneous specific immunotherapy are the risk to induce severe anaphylactic reactions and the need of multiple injections of the allergen to reduce IgE-mediated hypersensitivity. The sustained release of allergens over time provided by poly(lactide-co-glycolide) microparticles (MP) could mimic the current therapeutic schedule and decrease their allergenicity. Moreover, MP could also co-deliver Th1 immunoadjuvants, such as CpG motifs. Methods: Ovalbumin (OVA)-sensitized BALB/c mice were treated intradermally with OVA or OVA plus CpG containing MP. OVA-specific IgG1 and IgG2a as well as IgE total levels and cytokine production were assessed throughout the experiment. The protection exerted by the MP against allergen challenge was estimated with body temperature changes, mortality and other symptoms. Results: Microparticulated treatments, irrespective of the presence of CpG motifs, elicited a lower IgE/IgG2a ratio than those induced by the allergen in solution (free or with adjuvants). However, after induction of the anaphylactic shock, only mice treated with MP co-encapsulating OVA plus CpG showed a significant lower decrease in body temperature and were totally protected from death. Mice that were injected with OVA plus CpG in solution or with Alum displayed a marked fall of temperature accompanied by high mortality rates (70–100%). Conclusion: MP encapsulating both OVA, as an allergen model, and CpG sequences, as a pro-Th1 adjuvant, decreased the risk for OVA sensitization (IgE induction) and protected sensitized mice from anaphylactic shock after allergen provocation. Therefore, the combination of allergens and CpG sequences into MP could perform a safer alternative to current specific immunotherapy.

Intradermal immunization with ovalbumin-loaded poly-epsilon-caprolactone microparticles conferred protection in ovalbumin-sensitized allergic mice.

Background Although immunotherapy has been reported as the only treatment able to revert the T‐helper type 2 (Th2) response, its administration has some disadvantages such as the requirement of multiple doses, possible side‐effects provoked by conventional adjuvants and the risk of suffering an anaphylactic shock. For these reasons, drug‐delivery systems appear to be a promising strategy due to its ability to (i) transport the allergens, (ii) protect them from degradation, (iii) decrease the number of administrations and (iv) act as immuno‐adjuvants.