Targeting lung macrophages for fungal and parasitic pulmonary infections with innovative amphotericin B dry powder inhalers

The incidence of fungal pulmonary infections is known to be on the increase, and yet there is an alarming gap in terms of marketed antifungal therapies that are available for pulmonary administration. Amphotericin B (AmB) is a highly efficient broad-spectrum antifungal only marketed as an intravenous formulation. Based on the lack of effective antifungal and antiparasitic pulmonary treatments, the aim of this study was to develop a carbohydrate-based AmB dry powder inhaler (DPI) formulation, prepared by spray drying. Amorphous AmB microparticles were developed by combining 39.7 % AmB with 39.7 % γ-cyclodextrin, 8.1 % mannose and 12.5 % leucine. An increase in the mannose concentration from 8.1 to 29.8 %, led to partial drug crystallisation. Both formulations showed good in vitro lung deposition characteristics (80 % FPF < 5 µm and MMAD < 3 µm) at different air flow rates (60 and 30 L/min) when used with a DPI, but also during nebulisation upon reconstitution in water.

Influence of the vehicle on the properties and efficacy of microparticles containing amphotericin B

New microparticles containing amphotericin B (AMB) have been developed and manufactured by spray drying. To this end albumin, polylactic-co-glycolic acids (PLGA) and poly(sebacic anhydride) have been employed as drug carriers. The selection of the solvent used to disperse the drug and the vehicle before spray drying was critical on production yields and physical properties of the microparticles. Once particle size, morphology and dispersability in some aqueous media were shown to be acceptable for an intravenous administration, in vivo efficacy was evaluated and compared with the reference medicine Fungizone. Microparticles prepared with albumin, albumin heated at a high temperature, some kinds of PLGA or polyanhydride, as well as Fungizone, were tested in an experimental hamster model of infection with Leishmania infantum, by evaluating the evolution of parasitic burdens in spleen, liver and antibody responses. After the injection of three doses corresponding to 2 mg of AMB per kilogram each, diverse reactions were reported depending on the vehicle. The best dispersability, reduction of parasites and antibody response were achieved when the treatment was performed with AMB in albumin microspheres.

Amphotericin B molecular organization as an essential factor to improve activity/toxicity ratio in the treatment of visceral leishmaniasis

An in vivo study has been performed in order to determine the influence of amphotericin B (AMB) molecular organization on the toxicity and activity of this drug in the treatment of experimental visceral leishmaniasis. Three formulations with similar composition but different drug molecular self-association in aqueous media were prepared. Acute toxicity was evaluated by injecting them in healthy hamsters. Sub-acute toxicity and efficacy were studied administering them to animals previously infected with Leishmania infantum. The preparation with drug molecules completely dissolved into monomers (formulation "C") and produced the highest acute toxicity. The formulation whose AMB molecules were disposed as non-water-soluble multi-aggregates (formulation "B") proved to provide the lowest acute toxicity. This formula also showed an improved activity, mainly in the liver, if compared with the third tested formulation containing AMB molecules disposed as smaller dimerical "water-soluble" aggregates (formulation "A"). As a conclusion, molecular aggregation in biological media should be an important factor to consider when researching or optimizing medicines containing AMB. The liberation of molecules as large dispersed non-water-soluble multi-aggregates seems to improve the narrow therapeutic margin attached to the use of this drug.

Treatment of experimental visceral leishmaniasis with amphotericin B in stable albumin microspheres

Hydrophilic albumin microspheres are proposed as a new delivery system for amphotericin B (AMB; AMB microspheres). The acute toxicity of AMB microspheres was lower than that of the AMB-deoxycholate (AMB-Doc) reference formulation in hamsters. Lethal doses in healthy and infected animals were improved at least eight times. Intravenous bolus administration of doses of AMB microspheres up to 40 mg/kg of body weight did not produce acute symptoms of toxicity. The efficacy of this new formulation was tested against Leishmania infantum-infected hamsters at doses of 2, 10, 20, and 40 mg/kg. With the 2-mg/kg dose, the activity of AMB, as assessed through the parasite load reductions in the liver and spleen and the evolution of antibody levels, was also improved (P < 0.05) by use of the AMB microsphere system. At the higher doses of 10, 20, and 40 mg/kg, reductions in parasite levels of more than 99% were achieved in the liver and spleen after the administration of AMB microspheres. A pharmacokinetic study was performed to study the serum, liver, and spleen AMB concentrations after administration of AMB microspheres and the reference formulation. Interestingly, a significant accumulation of AMB in the spleen and liver was observed after AMB microsphere administration. Our results suggest that this new formulation is a promising alternative to the conventional AMB-Doc formulation for the treatment of visceral leishmaniasis.

Heterogeneity and immunogenicity of the Trichinella TSL-1 antigen gp53

This study investigates the heterogeneity and immunogenicity of the Trichinella TSL-1 antigen gp53. Western blotting analysis of several Trichinella isolates with the gp53-specific monoclonal antibodies (mAbs) US5 and US9, produced in Btkxid mice, revealed that gp53 from the species T. britovi, T. murrelli and genotype T8 had higher MW (60 kDa) than gp53 from T. spiralis, T. nelsoni and genotype T6 (53 kDa) and from T. nativa (55 kDa). mAb US5 reacted only with gp53 from T. spiralis. Experiments including immunoassays of gp53 binding by sera from T. spiralis-infected mice, in the presence of different potential inhibitors (recombinant gp53, US5, T. britovi-crude larval extract (CLE), and CLE N- and O-glycans), indicate (i) that gp53 from T. spiralis bears specific epitopes that induce antibody formation during infection; (ii) that the protein epitopes of gp53 are much more important (76 or 68% of total antibody reactivity in BALB/c and Swiss CD-1 mice, respectively) than the corresponding glycan epitopes including tyvelose (11 or 32% of total reactivity) for the induction of anti-gp53 circulating antibodies; and (iii) that the species-specific epitopes present on gp53 are differentially recognized in different mouse strains. Whereas in BALB/c mice US5- and non-US5-recognized species-specific epitopes on gp53 bind about 84% of circulating antibodies on day 80 post-infection, this percentage was only 38% in Swiss CD-1 mice. These data on the antigenicity of gp53 contrast with data for Trichinella CLE antigens, in that most circulating antibodies reactive with CLE antigens recognized tyvelose-containing epitopes (57% and 58% of circulating antibodies in BALB/c and Swiss CD-1 mice, respectively). Together these results demonstrate that gp53 is recognized during infection but is antigenically different from other Trichinella TSL-1 antigens.

Improving bioavailability and anthelmintic activity of albendazole by preparing albendazole-cyclodextrin complexes

The bioavailability and anthelmintic activity of albendazole-cyclodextrin complexes (ABZ-CDC) compared to albendazole suspensions in carboxymethylcellulose (ABZ-CMC) was assessed in a mouse model for Trichinella infections. Swiss CD-1 mice experimentally infected with T. spiralis were treated with both formulations against enteral (adult worms) and parenteral (migrating and encysted larvae). Oral bioavailability was assessed in age matched mice treated with 50 mg/kg of both formulations. The anthelmintic effects and plasma concentration of the active metabolite albendazole-sulphoxide (ABZSO) enantiomer (-) were significantly increased following administration of ABZ-CDC in relation to ABZ-CMC.

A comparison of antigenic peptides in muscle larvae of several Trichinella species by two-dimensional western-blot analysis with monoclonal antibodies

The antigens recognised by mAb US5 specific to 53 kDa glycoprotein (gp 53) in T. spiralis L-1 muscle larvae (TSL1) antigens, mAb US9 specific to gp 53 in TSL1 from all encapsulated species and mAb US4 specific to a tyvelose containing tetrasaccharide present in TSL1, were investigated in crude extracts from muscle larvae of T. spiralis, T. nativa and T. britovi by 2D-electrophoresis and western-blot. At least four proteins of different p1 were recognised by mAb US5 on T. spiralis antigens. Recognition profile of mAb US9 on T. spiralis antigens exhibited some variation with regard to that of the US5. Polymorphism was apparent in gp 53. High reactivity was shown by the mAb US4 with the three species.

Possible presence of common tyvelose-containing glycans in Trichinella L1 larvae and embryonated eggs of several nematodes

A monoclonal antibody (mAb US4) recognising an epitope containing tyvelose within the T. spiralis L-1 muscle larvae (TSL-1) antigens was tested in western-blot against various antigenic preparations from different stages of the following nematodes: T. spiralis (L1, adult), T. muris (egg, L1, L3, adult), Ascaris suum (egg, adult), Toxocara canis (egg, adult), Anisakis simplex (L3) and Haemochus contortus (egg). Positive reaction was present in antigen preparations from L1 larvae of T. spiralis and T. muris and from embryonated eggs of T. muris, A. seum, T. canis and H. contortus.

Methimazole-mediated enhancement of albendazole oral bioavailability and anthelmintic effects against parenteral stages of Trichinella spiralis in mice: the influence of the dose-regime

The influence of methimazole (MTZ) inhibitor of the microsomal oxidases on the systemic availability of the albendazole sulpho-metabolites (ABZS-MT) albendazole-sulphoxide (ABZSO) and albendazole-sulphone (ABZSO2) and on its anthelmintic effects was investigated in a mouse model for helminthic infections. Plasma concentrations of the ABZS-MT were measured by high performance liquid chromatography (HPLC) following treatment of Swiss CD-1 mice with albendazole (ABZ) alone or ABZ plus MTZ, at both single and repeated doses. The anthelmintic effects were assessed in age-matched mice similarly treated following infection with Trichinella spiralis. MTZ significantly (p < 0.01) increased the ABZS-MT plasma concentrations although the pharmacokinetic profile varied greatly according to the dose of ABZ administered. When ABZ was given at a single dose of 50 mg/kg followed by MTZ at 3 mg/kg, a cumulative effect was observed in the ABZS-MT plasma levels with pharmacokinetic parameters (Tmax = 24 h, Cmax= 30.88 microg/ml and AUC = 1120.80 microg h/ml) significantly ( p < 0.01) higher than those following administration of ABZ alone (Tmax = 3 h, Cmax = 11.00 microg/ml and AUC = 268.03 microg h/ml). This cumulative effect was absent following administration of ABZ at 100 mg/kg where, after reaching a maximum (Cmax = 27.23 microg/ml) at 3 h post-administration (Tmax), the ABZS-MTplasma levels felt down quickly to values under those obtained after administration of ABZ at the same dose, but alone (AUC = 362.15 microg h/ml vs. 340.15 microg h/ml, respectively). When ABZ was given at 50 mg/kg together with MTZ three times every 24 h, a rapid decrease was observed in the ABZS-MT plasma levels following administration of both the second and third doses, respectively. The pharmacokinetic profile of ABZS-MT following administration of each of the three doses of ABZ at 100 mg/kg plus MTZ was the same as that obtained after the single treatment. The rapid decrease of the ABZS-MT plasma levels observed after the sustained treatment or after the single treatment at 100 mg/kg could be due to a microsomal oxidase inductive effect (probably the cytochrome P-450) caused by ABZSO. The co-administration of MTZ significantly (p < 0.01) increased the anthelmintic effects of ABZ against both migrating and encysted larvae of T. spiralis. Repeated treatment did not improve the anthelmintic effects of the single treatment as the efficacies against both stages of the parasite were always lower or identical to those of the single treatment at the corresponding doses.

Improvement of albendazole efficacy against enteral, but not against parenteral stages of Trichinella spiralis by preparing solid dispersions in polyvinylpyrrolidone

A comparison was made, in the Trichinella/mouse model, of the anthelmintic effects of albendazole (ABZ) and ricobendazole (RBZ) formulated as solid dispersions in polyvinylpyrrolidone with regard to ABZ formulated as a suspension in carboxymethylcellulose. A solid dispersion significantly increased (p < 0.01) the efficacy of the drugs against intestinal preadult but not against migrating and muscle stages of the parasite. The anthelmintic efficacy of RBZ given as a solid dispersion was equivalent to (against preadult and encysted larvae) or significantly lower than (against migrating larvae) that of ABZ with the same formulation. The pharmacokinetic profiles of ABZSO as measured by HPLC showed no significant differences in the Cmax and AUC following administration of ABZ formulated as a suspension or solid dispersion although the Tmax was significantly lower for the dispersion.