In our previous studies, the use of cationic solid–lipid nanoparticle (cSLN) formulation as a delivery system has revealed comparable efficiency: cytotoxicity ratio with linear PEI-25 kDa–pDNA polyplexes, protected CPA, CPB and CPB−CTE genes from extracellular enzymatic degradation and also exhibited considerable low cytotoxicity [22]. Hence, cSLNs can be considered as suitable adjuvant and/or delivery system for designing third-generation cocktail vaccines. Also, these characterized formulations of cocktail vaccine candidates could immunize BALB/c

mice against cutaneous leishmaniasis [23]. In this study, we evaluated the potency of the BI 2536 order A2–CPA–CPB−CTE trifusion gene delivered using either a physical method (electroporation) or a chemical delivery system (cSLN) as a candidate vaccine against L. infantum infection and assessed its immune induction potential in BALB/c mice. The A2 gene (with Kozak sequence) was subcloned from pUC57 vector (synthesized by ShineGene Molecular Biotech, Inc., Shanghai, China‎‏) into pGEM7zf(+)vector (Promega, Madison, WI, USA). Both pGEM-cpa and pGEM-cpb were available from our previous studies [11], and CPA and CPB−CTE fragments were subcloned

into pAT153 vector (Boca Scientific, Boca Raton, FL, USA), respectively. Then CPA–CPB−CTE was cloned downstream of the A2 gene in pGEM7zf(+) vector. The A2–CPA–CPB−CTE fragment was subcloned into pcDNA3·1(−) (Invitrogen, Grand Island, NY, USA) vector to generate pcDNA–A2–CPA–CPB−CTE as a DNA vaccine. pcDNA–A2–CPA–CPB−CTE plasmids were purified by ion exchange chromatography with QIAGEN (Hilden, Germany) Endofree Mega C646 molecular weight kit and then confirmed by PCR and digestion (data not shown). The cSLN suspension was manufactured by a validated technique previously Suplatast tosilate described by Doroud et al. [22]. cSLN–pDNA complexes were prepared by adding volumes corresponding to 1200 μg of purified pDNA (pcDNA–A2–CPA–CPB−CTE) to cSLN suspension at DOTAP: pDNA ratio of 6 : 1 (w/w) and at 60 min incubation at room temperature separately [22, 24]. Complete condensation and complexation

of pDNAs with cSLN were analysed by agarose gel electrophoresis, as previously demonstrated [22, 24]. Size and zeta potential measurements, gel retardation analysis and DNase I protection study were all performed according to the conditions demonstrated in our previous study [22, 24]. The physicochemical stability of the formulations was assessed during 1 month and reported previously [22]. In this study, the characteristics of the formulations, that is, the mean diameter, polydispersity index, zeta potential and retardation ability, were assessed according the ICH guidelines. For this purpose, nanoparticles containing pDNAs were stored at high temperatures and relative humidity (25 ± 2°C/60% RH) in a qualified stability analysis chamber (accuracy: ±0·2°C; humidity uniformity: ±3% RH) over a period of 12 months, at dark and regular time intervals.