Moléculas coestimulatórias na leishmaniose visceral

Visceral leishmaniasis (VL) is endemic in many countries, including Brazil. The protozoan Leishmania infantum, is the etiological agent of VL, and is transmitted by the bite of female sandflies during the blood meal. The majority of subjects when exposed to the parasite do not develop the disease, because of development of Th1 cellular responses. Those who have develop signs of VL such as fever, weight loss, hepatosplenomegaly, have impairment of the cellular immune response, specific to the Leishmania antigens. We evaluated whether the specififc anergy during symptomatic VL, may be associated with changes in T cells costimulatory molecules or their ligands in CD14+ monocytes. There is an increase in CTLA-4 porcentage on CD4+ T lymphocytes (p=0.001) and ICOS on CD4+ and CD8+ T cells (p=0.002 to CD4+ and p=0.003 to CD8+), after stimulation by soluble Leishmania antigen (SLA) during active visceral leishmaniasis, and that there is a higher percentage of these molecules ex vivo, when comparing symptomatic to recovered individuals (p=0.04 to CTLA-4 in CD4+, and p=0.001 to ICOS in CD4+ and p=0.026 to CD8+). Moreover, we found a high gene expression of CTLA-4, OX-40 and ICOS during active VL. CD40, CD80, CD86, HLA-DR and ICOSL molecules do not suffer changes during disease. There is IFN-γ production by the peripheral blood cells, after SLA stimulation, by peripheral blood cells in symptomatic subjects; however, there is a decrease of the ratio IFN-γ/IL-10, which is reversed after clinical recovery. The impairment of some costimulatory molecules pathways during symptomatic VL could inhibit the ability of phagocytes to kill Leishmania and could facilitate their survival and the proliferation inside macrophages.

Nanotechnological delivery systems for the oral administration of active molecules: Polymeric microparticles and microemulsions applied to anti-inflammatory and anti-infectious drugs

This thesis was devoted to the development of innovative oral delivery systems for two different molecules. In the first part, microparticles (MPs) based on xylan and Eudragit® S- 100 were produced and used to encapsulate 5-aminosalicylic acid for colon delivery. Xylan was extracted from corn cobs and characterized in terms of its physicochemical, rheological and toxicological properties. The polymeric MPs were prepared by interfacial cross-linking polymerization and spray-drying and characterized for their morphology, mean size and distribution, thermal stability, crystallinity, entrapment efficiency and in vitro drug release. MPs with suitable physical characteristics and satisfactory yields were prepared by both methods, although the spray-dried systems showed higher thermal stability. In general, spraydried MPs would be preferable systems due to their thermal stability and absence of toxic agents used in their preparation. However, drug loading and release need to be optimized. In the second part of this thesis, oil-in-water microemulsions (O/W MEs) based on mediumchain triglycerides were formulated as drug carriers and solubility enhancers for amphotericin B (AmB). Phase diagrams were constructed using surfactant blends with hydrophiliclipophilic balance values between 9.7 and 14.4. The drug-free and drug-loaded MEs presented spherical non-aggregated droplets around 80 and 120 nm, respectively, and a low polydispersity index. The incorporation of AmB was high and depended on the volume fraction of the disperse phase. These MEs did not reduce the viability of J774.A1 macrophage-like cells for concentrations up to 25 μg/mL of AmB. Therefore, O/W MEs based on propylene glycol esters of caprylic acid may be considered as suitable delivery systems for AmB