The delicate balance in genetically engineering live vaccines

Contemporary vaccine development relies less on empirical methods of vaccine construction, and now employs a powerful array of precise engineering strategies to construct immunogenic live vaccines. In this review, we will survey various engineering techniques used to create attenuated vaccines, with an emphasis on recent advances and insights. We will further explore the adaptation of attenuated strains to create multivalent vaccine platforms for immunization against multiple unrelated pathogens. These carrier vaccines are engineered to deliver sufficient levels of protective antigens to appropriate lymphoid inductive sites to elicit both carrier-specific and foreign antigen-specific immunity. Although many of these technologies were originally developed for use in Salmonella vaccines, application of the essential logic of these approaches will be extended to development of other enteric vaccines where possible. A central theme driving our discussion will stress that the ultimate success of an engineered vaccine rests on achieving the proper balance between attenuation and immunogenicity. Achieving this balance will avoid over-activation of inflammatory responses, which results in unacceptable reactogenicity, but will retain sufficient metabolic fitness to enable the live vaccine to reach deep tissue inductive sites and trigger protective immunity. The breadth of examples presented herein will clearly demonstrate that genetic engineering offers the potential for rapidly propelling vaccine development forward into novel applications and therapies which will significantly expand the role of vaccines in public health.     

Molecular and Insecticidal Characterization of a Novel Cry-Related Protein from Bacillus Thuringiensis Toxic against Myzus persicae

This study describes the insecticidal activity of a novel Bacillus thuringiensis Cry-related protein with a deduced 799 amino acid sequence (~89 kDa) and ~19% pairwise identity to the 95-kDa-aphidicidal protein (sequence number 204) from patent US 8318900 and ~40% pairwise identity to the cancer cell killing Cry proteins (parasporins Cry41Ab1 and Cry41Aa1), respectively. This novel Cry-related protein contained the five conserved amino acid blocks and the three conserved domains commonly found in 3-domain Cry proteins. The protein exhibited toxic activity against the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae) with the lowest mean lethal concentration (LC₅₀ = 32.7 μg/mL) reported to date for a given Cry protein and this insect species, whereas it had no lethal toxicity against the Lepidoptera of the family Noctuidae Helicoverpa armigera (Hübner), Mamestra brassicae (L.), Spodoptera exigua (Hübner), S. frugiperda (J.E. Smith) and S. littoralis (Boisduval), at concentrations as high as ~3.5 μg/cm². This novel Cry-related protein may become a promising environmentally friendly tool for the biological control of M. persicae and possibly also for other sap sucking insect pests.     

Application of near-infrared fluorescent cholangiography using indocyanine green in laparoscopic cholecystectomy

ObjectiveNear-infrared fluorescence cholangiography (NIRF-C) can help to identify the bile duct during laparoscopic cholecystectomy. This retrospective study was performed to investigate the effect of NIRF-C in laparoscopic cholecystectomy.MethodsConsecutive patients who underwent NIRF-C-assisted laparoscopic cholecystectomy (n = 34) or conventional laparoscopic cholecystectomy (n = 36) were enrolled in this study. Identification of biliary structures, the operation time, intraoperative blood loss, and postoperative complications were analyzed.ResultsLaparoscopic cholecystectomy was completed in all patients without conversion to laparotomy. The median operation time and intraoperative blood loss were not significantly different between the two groups. No intraoperative injuries or postoperative complications occurred in either group. In the NIRF-C group, the visualization rate of the cystic duct, common bile duct, and common hepatic duct prior to dissection was 91%, 79%, and 53%, respectively. The success rate of cholangiography was 100% in the NIRF-C group. NIRF-C was more effective for visualizing biliary structures in patients with a BMI of <25 than >25 kg/m².ConclusionsNIRF-C is a safe and effective technique that enables real-time identification of the biliary anatomy during laparoscopic cholecystectomy. NIRF-C helps to improve the efficiency of dissection.     

The anti-tumor efficacy of curcumin when delivered by size/charge-changing multistage polymeric micelles based on amphiphilic poly(β-amino ester) derivates

Modifying positive surface charge and reducing bulk size of nanoparticles has been proven beneficial to cancer cellular delivery, but meanwhile results in fast clearance and unspecific distribution in body after intravenous injection. How to balance these problems is still a challenge to construct an ideal nano-scaled drug delivery system in cancer treatment. Herein, we developed a multistage drug delivery system to enhance anticancer efficacy of curcumin (CUR), which could intelligently alter its size and surface charge after long-circulation and extravasation from leaky blood vessels at tumor sites. This micellar system was constructed by amphiphilic and pH-sensitive methoxy poly(ethylene glycol)-poly(lactide)-poly(β-amino ester) (MPEG-PLA-PAE) copolymers. As compared with MPEG-PLA micelles, MPEG-PLA-PAE micelles displayed several advantageous characteristics for drug delivery and treatment. We found that CUR-loaded MPEG-PLA-PAE micelles remained stable in murine plasma at 37 °C even with high drug loading. More interestingly, when the media pH decreased from 7.4 to 5.5, the micelles shrank from 171.0 nm to 22.6 nm and their surface charge increased to 24.8 mV meanwhile, which resulted in the significantly improved cell uptake of CUR by human breast cancer MCF-7 cells. Using indocyanine green (ICG) as a fluorescence probe, it was observed that MPEG-PLA-PAE micelles experienced longer circulation than MPEG-PLA micelles followed by accumulation at tumors with stronger fluorescence intensity. Consequently, MPEG-PLA-PAE micelles achieved enhanced cancer growth inhibition of 65.6% in vivo. All these findings demonstrated the potential of size/charge–changing MPEG-PLA-PAE micelles as a promising drug delivery system for tumor-targeted therapy.     

Improving drug accumulation and photothermal efficacy in tumor depending on size of ICG loaded lipid-polymer nanoparticles

A key challenge to strengthen anti-tumor efficacy is to improve drug accumulation in tumors through size control. To explore the biodistribution and tumor accumulation of nanoparticles, we developed indocyanine green (ICG) loaded poly (lactic-co-glycolic acid) (PLGA) -lecithin-polyethylene glycol (PEG) core-shell nanoparticles (INPs) with 39 nm, 68 nm and 116 nm via single-step nanoprecipitation. These INPs exhibited good monodispersity, excellent fluorescence and size stability, and enhanced temperature response after laser irradiation. Through cell uptake and photothermal efficiency in vitro, we demonstrated that 39 nm INPs were more easily be absorbed by pancreatic carcinoma tumor cells (BxPC-3) and showed better photothermal damage than that of 68 nm and 116 nm size of INPs. Simultaneously, the fluorescence of INPs offered a real-time imaging monitor for subcellular locating and in vivo metabolic distribution. Near-infrared imaging in vivo and photothermal therapy illustrated that 68 nm INPs showed the strongest efficiency to suppress tumor growth due to abundant accumulation in BxPC-3 xenograft tumor model. The findings revealed that a nontoxic, size-dependent, theranostic INPs model was built for in vivo cancer imaging and photothermal therapy without adverse effect.