In vitroandin vivoevaluations of PLGA microsphere vaccine formulations containing pDNA coexpressing Hepatitis B surface antigen and Interleukin-2

DNA vaccine incorporated poly (lactic-co-glycolic) acid (PLGA) microspheres offer enhanced protection against Aeromonas hydrophila infection

Encapsulation of DNA vaccines onto carriers enhances the immunogenicity of an antigen. Specifically, biodegradable polymers offer sustained release of vaccines which is crucial for any targeted delivery approach. Poly (lactic-co-glycolic) acid (PLGA) microspheres were used to load a DNA vaccine having a targeted gene of outer membrane protein (OMP) of Aeromonas hydrophila to clone and construct a DNA vaccine using a eukaryotic expression vector system (pVAX1-OMP DNA) and delivery in Carassius auratus against A. hydrophila infection. PLGA microspheres were prepared by emulsion technique oil-in-water and characterized by a High-Resolution Scanning Electron Microscope (HR-SEM). The results of PLGA-pVAX1-OMP DNA microspheres shows that average of 100-150 μm particle size and a loading efficiency (LE) of 68.8 %. Results indicate that C. auratus fed with PLGA-pVAX1-OMP DNA microspheres revealed a significant improvement in innate immune response, which includes, myeloperoxidase activity, respiratory burst and total immunoglobulin level compared with control group fish. The immune-related gene, IL1β, IL10, TGF, c-type, and g-type lysozyme also showed significantly higher expression after immunization. Furthermore, dietary supplementation of the PLGA-pVAX1-OMP DNA (G III) group exhibited a significantly higher survival rate (78 %) than the control group of fish. These results help us to understand the of mechanism of DNA vaccine administrated feed through PLGA nanoparticles resistance to infection by regulating systemic and innate immunity in Carassius auratus.

Micro- and nanoparticulates for DNA vaccine delivery

DNA vaccination has emerged as a promising alternative to traditional protein-based vaccines for the induction of protective immune responses. DNA vaccines offer several advantages over traditional vaccines, including increased stability, rapid and inexpensive production, and flexibility to produce vaccines for a wide variety of infectious diseases. However, the immunogenicity of DNA vaccines delivered as naked plasmid DNA is often weak due to degradation of the DNA by nucleases and inefficient delivery to immune cells. Therefore, biomaterial-based delivery systems based on micro- and nanoparticles that encapsulate plasmid DNA represent the most promising strategy for DNA vaccine delivery. Microparticulate delivery systems allow for passive targeting to antigen presenting cells through size exclusion and can allow for sustained presentation of DNA to cells through degradation and release of encapsulated vaccines. In contrast, nanoparticle encapsulation leads to increased internalization, overall greater transfection efficiency, and the ability to increase uptake across mucosal surfaces. Moreover, selection of the appropriate biomaterial can lead to increased immune stimulation and activation through triggering innate immune response receptors and target DNA to professional antigen presenting cells. Finally, the selection of materials with the appropriate properties to achieve efficient delivery through administration routes conducive to high patient compliance and capable of generating systemic and local (i.e. mucosal) immunity can lead to more effective humoral and cellular protective immune responses. In this review, we discuss the development of novel biomaterial-based delivery systems to enhance the delivery of DNA vaccines through various routes of administration and their implications for generating immune responses.

Cyclosporine combined with nonlytic interleukin 2/Fc fusion protein improves immune response to hepatitis B vaccination in a mouse skin transplantation model

BACKGROUND

Improving immune responses to vaccination in immunosuppressed patients is extremely important. Previously, we observed that cyclosporine (CsA) combined with a nonlytic interleukin (IL)-2/fragment crystallizable (Fc) fusion protein induces immune tolerance to mouse skin transplantations. In the present study, we asked whether this combination improved hepatitis B (HBV) vaccine efficacy in immunosuppressed mice while also prolonging skin graft survival.

METHODS

After C57BL/6 mice received DBA/2 skin grafts, they were administered a 14-day course of CsA (30 mg/kg intraperitoneal) combined with IL-2/Fc (1 μg, intraperitoneal). HBV vaccine (2 μg) was injected intramuscularly on the day of skin transplantation. On day 14, the serum levels of hepatitis B surface antibody (HBsAb), IL-4, IL-10, interferon (IFN-γ), and IL-2 were measured by enzyme-linked immunosorbent assay. We assessed the percentages of CD4(+)CXCR5(+) follicular T helper cells, CD4(+)FoxP3(+) regulatory T cells (Treg) and expressions of IL-17, IL-21, FoxP3, Bcl-6 in the spleen. Animals were divided into four groups: control, vaccine-treated, CsA + vaccine-treated, CsA + IL-2/Fc + vaccine-treated hosts.

RESULTS

Combination therapy significantly increased HBsAb levels and also prolonged skin graft survival. Serum levels of Th1 cytokines IL-2 and IFN-γ were significantly higher in the combination group, while Th2 cytokines, IL-4 and IL-10 were lower. Combined treatment increased the percentage of Treg and the expression of Foxp3 and IL-21, meanwhile inhibiting the expression of Bcl-6. But the percentage of Tfh did not significantly change among the groups.

CONCLUSIONS

These observations suggested that a combination of CsA and IL-2/Fc fusion protein enhanced immune responses after HBV vaccination and prolonged skin graft survival.

Sustained-release delivery of octreotide from biodegradable polymeric microspheres

The study reports on the drug release behavior of a potent synthetic somatostatin analogue, octreotide acetate, from biocompatible and biodegradable microspheres composed of poly-lactic-co-glycolic acid (PLGA) following a single intramuscular depot injection. The serum octreotide levels of three Oakwood Laboratories formulations and one Sandostatin LAR(®) formulation were compared. Three formulations of octreotide acetate-loaded PLGA microspheres were prepared by a solvent extraction and evaporation procedure using PLGA polymers with different molecular weights. The in vivo drug release study was conducted in male Sprague-Dawley rats. Blood samples were taken at predetermined time points for up to 70 days. Drug serum concentrations were quantified using a radioimmunoassay procedure consisting of radiolabeled octreotide. The three octreotide PLGA microsphere formulations and Sandostatin LAR(®) all showed a two-phase drug release profile (i.e., bimodal). The peak serum drug concentration of octreotide was reached in 30 min for all formulations followed by a decline after 6 h. Following this initial burst and decline, a second-release phase occurred after 3 days. This second-release phase exhibited sustained-release behavior, as the drug serum levels were discernible between days 7 and 42. Using pharmacokinetic computer simulations, it was estimated that the steady-state octreotide serum drug levels would be predicted to fall in the range of 40-130 pg/10 μL and 20-100 pg/10 μL following repeat dosing of the Oakwood formulations and Sandostatin LAR(®) every 28 days and every 42 days at a dose of 3 mg/rat, respectively.

Formulation of chitosan-TPP-pDNA nanocapsules for gene therapy applications

The encapsulation of DNA inside nanoparticles meant for gene delivery applications is a challenging process where several parameters need to be modulated in order to design nanocapsules with specific tailored characteristics. The purpose of this study was to investigate and improve the formulation parameters of plasmid DNA (pDNA) loaded in chitosan nanocapsules using tripolyphosphate (TPP) as polyanionic crosslinker. Nanocapsule morphology and encapsulation efficiency were analyzed as a function of chitosan degree of deacetylation and chitosan-TPP ratio. The manipulation of these parameters influenced not only the particle size but also the encapsulation and release of pDNA. Consequently the transfection efficiency of the nanoparticulated systems was also enhanced with the optimization of the particle characteristics. Overall, the differently formulated nanoparticulated systems possess singular properties that can be employed according to the desired gene delivery application.