Abstract
Since dogs play a central role in the contamination of humans and livestock with Echinococcus granulosus, the development of an effective vaccine for dogs is essential to control the disease caused by this parasite. For this purpose, a formulation based on biodegradable polymeric nanoparticles (NPs) as delivery system of recombinant Echinococcus granulosus antigen (tropomyosin EgTrp) adjuved with monophosphoryl lipid A (MPLA) has been developed. The obtained nanoparticles had a size of approximately 200 nm in diameter into which the antigen was correctly preserved and encapsulated. The efficiency of this system to deliver the antigen was evaluated in vitro on canine monocyte-derived dendritic cells (cMoDCs) generated from peripheral blood monocytes. After 48 h of contact between the formulations and cMoDCs, we observed no toxic effect on the cells but a strong internalization of the NPs, probably through different pathways depending on the presence or not of MPLA. An evaluation of cMoDCs activation by flow cytometry showed a stronger expression of CD80, CD86, CD40 and MHCII by cells treated with any of the tested formulations or with LPS (positive control) in comparison to cells treated with PBS (negative control). A higher activation was observed for cells challenged with EgTrp-NPs-MPLA compared to EgTrp alone. Formulations with MPLA, even at low ratio of MPLA, give better results than formulations without MPLA, proving the importance of the adjuvant in the nanoparticles structure. Moreover, autologous T CD4+ cell proliferation observed in presence of cMoDCs challenged with EgTrp-NPs-MPLA was higher than those observed after challenged with EgTrp alone (p<0.05). These first results suggest that our formulation could be used as an antigen delivery system to targeting canine dendritic cells in the course of Echinococcus granulosus vaccine development.
Highlights
Echinococcal hydatidosis is a parasitic disease caused by the larvae of the dog tapeworm Echinococcus granulosus
To optimize the quantity of monophosphoryl lipid A (MPLA) used in the final formulation, we evaluated the expression of the activation markers 24 h after challenging the canine monocyte-derived dendritic cells (cMoDCs) with nanoparticles containing four different MPLA loading ratios: 0.025%, 0.05%, 0.1% and 0.2%
We evaluated the expression of the activation markers on cMoDCs 24 h after being challenged with one of the following formulations: blank-NPs, EgTrp alone, EgTrp-NPs, NPs-MPLA and EgTrp-NPsMPLA, using the best MPLA loading ratio previously selected
Summary
Echinococcal hydatidosis is a parasitic disease caused by the larvae of the dog tapeworm Echinococcus granulosus. This parasite requires two successive hosts for its complete life cycle [1]. The definitive hosts) are domestic carnivores, such as dogs, in which adult tapeworms inhabit the small intestine and deliver eggs excreted with the feces. The intermediate hosts are herbivorous animals, such as sheep, goats, bovines or pigs. Humans are accidental intermediate hosts, infected by contaminated food or water with the parasite eggs. In human and herbivorous disease, larvae localized in the liver (75% of cases) or lungs (5–15% of cases) develop in cysts, which can lead to allergic reactions or even death [1,2]. Dog’s vaccination against the parasite appears to be an effective means of decreasing this disease [3]
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