Preparation and evaluation of chitosan nanoparticles containing CtxB antigen against Vibrio cholera

Nanoparticles-based technologies for cholera detection and therapy

Cholera is a waterborne disease caused by Vibrio cholerae bacteria generally transmitted through contaminated food or water sources. Although it has been eradicated in most Western countries, cholera continues to be a highly transmitted and lethal disease in several African and Southeast Asian countries. Unfortunately, current diagnostic methods for cholera have challenges including high cost or delayed diagnoses that can lead to increased disease transmission during pandemics, while current treatments such as therapeutic drugs and vaccines have limited efficacy against drug-resistant serogroups of Vibrio cholerae. As such, new solutions that can treat cholera in an efficient manner that avoids Vibrio cholerae's adaptive immunity are needed. Nanoparticles (NPs) are a suitable platform for enhancing current theranostic tools because of their biocompatibility and ability to improve drug circulation and targeting. Nanoparticle surfaces can also be modified with various protein receptors targeting cholera toxins produced by Vibrio cholerae. This review will address recent developments in diagnostics, therapeutics, and prevention against cholera particularly focusing on the use of metal-based nanoparticles and organic nanoparticles. We will then discuss future directions regarding nanoparticle research for cholera.

Adenovirus vector-mediated single chain variable fragments target the nucleocapsid protein of porcine epidemic diarrhea virus and protect against viral infection in piglets

Porcine epidemic diarrhea virus (PEDV) mainly infects the intestinal epithelial cells of pigs, causing porcine epidemic diarrhea (PED). In particular, the virus causes severe diarrhea, dehydration, and death in neonatal piglets. Maternal immunity effectively protects neonatal piglets from PEDV infection; however, maternal antibodies can only prevent PEDV attachment and entry into target cells, but have no effects on intracellular viruses. Intracellular antibodies targeting virus-encoded proteins are effective in preventing viral infection. We previously identified four single chain variable fragments (scFvs), ZW1-16, ZW3-21, ZW1-41, and ZW4-16, which specifically targeted the PEDV N protein and significantly inhibited PEDV replication and up-regulated interferon-λ1 (IFN-λ1) expression in host cells. In our current study, the four scFvs were subcloned into replication-defective adenovirus vectors to generate recombinant adenoviruses rAdV-ZW1-16, rAdV-ZW3-21, rAdV-ZW1-41, and rAdV-ZW4-16. ScFvs were successfully expressed in Human Embryonic Kidney 293 (HEK293) cells and intestinal porcine epithelial cell line J2 (IPEC-J2) and were biosafe for piglets as indicated by body temperature and weight, scFv excretion in feces, IFN-γ and interleukin-4 (IL-4) expression in jejunum, and pathological changes in porcine tissue after oral administration. Western blotting, immunofluorescence, and immunohistochemical analyses showed that scFvs were expressed in porcine jejunum. The prophylactic effects of rAdV-ZW, a cocktail of the four rAdV-scFvs, on piglet diarrhea caused by PEDV was investigated. Clinical symptoms in piglets orally challenged with PEDV, following a two-time treatment with rAdV-ZW, were significantly reduced when compared with PEDV-infected piglets treated with phosphate buffered saline (PBS) or rAdV-wild-type. Also, no death and jejunal lesions were observed. ScFv co-localization with the PEDV N protein in vivo was also observed. Next, the expression of pro-inflammatory serum cytokines such as tumor necrosis factor-α (TNF-α), IL-6, IL-8, IL-12, and IFN-λ was assessed by enzyme-linked immunosorbent assay (ELISA), which showed that scFvs significantly suppressed PEDV-induced pro-inflammatory cytokine expression and restored PEDV-inhibited IFN-λ expression. Therefore, our study supported a promising role for intracellular scFvs targeting the PEDV N protein to prevent and treat diarrhea in PEDV-infected piglets.

Preparation of Chitosan Nanoparticles as a Capable Carrier for Antigen Delivery and Antibody Production

Background

Chitosan (CS) nanoparticles have attracted considerable attention as a non-viral and cationic carrier for delivery of therapeutic proteins and antigens and offer non-invasive routes of administration such as oral, nasal and ocular routes, and also show adjuvant characteristics for vaccines.

Objectives

Preparation and formulation of CS nanoparticles as a capable carrier with immunoadjuvant properties to enhance the bioavailability of antigen and produce antibody with high affinity.

Materials and Methods

CS nanoparticles were produced by ionic gelation process of sodium tripolyphosphate (TPP) with CS. Particle size and morphology of nanoparticles were determined using Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) and also direct observation under light microscope. The influence of the initial BSA concentration and CS concentration on loading efficiency and release behavior was evaluated. The ε-toxin (derived from Clostridium perfringens type D) was loaded on CS nanoparticles and the complex was injected hypodermically into the rabbits for once. The anti ε-toxin antibody level in blood serum was evaluated using Dot Blot and ELISA methods.

Results

The CS nanoparticles in different groups have a particle diameter (Z-average) in approximate ranges of 200-400, 300-600, 450-800 nm and a positive Zeta potential (32.4 - 48.6 mv). Optimum loading efficiency was achieved for CS at a concentration of 0.5 mg.mL^-1 and TPP of 1.0 mg.mL^-1. The results showed that the toxin-CS complex produces antitoxin at levels more than twice as high the control.

Conclusion

The CS nanoparticles can be used as a good biodegradable carrier for protein and antigen delivery.

Demystifying particle-based oral vaccines

Introduction: The oral route of vaccination is pain- and needle-free and can induce systemic and mucosal immunity. However, gastrointestinal barriers and antigen degradation impose significant hurdles in the development of oral vaccines. Live attenuated viruses and bacteria can overcome these barriers but at the risk of introducing safety concerns. As an alternative, particles have been investigated for antigen protection and delivery, yet there are no FDA-approved oral vaccines based on particle-based delivery systems. Our objective was to discover underlying determinants that can explain the current inadequacies and identify paradigms that can be implemented in future for successful development of oral vaccines relying on particle-based delivery systems.Areas covered: We reviewed literature related to the use of particles for oral vaccination and placed special emphasis on formulation characteristics and administration schedules to gain an insight into how these parameters impact production of antigen-specific antibodies in systemic and mucosal compartments.Expert opinion: Despite the long history of vaccines, particle-based oral vaccination is a relative new field with the first study published in 1989. Substantial variability exists between different studies with respect to dosing schedules, number of doses, and the amount of vaccine per dose. Most studies have not used adjuvants in the formulations. Better standardization in vaccination parameters is required to improve comparison between experiments, and adjuvants should be used to enhance the systemic and mucosal immune responses and to reduce the number of doses, which will make oral vaccines more attractive.

Chitosan Nanoparticles Loaded with Truncated ORF2 Protein as an Oral Vaccine Candidate against Hepatitis E

In a continuous effort to develop effective vaccines against hepatitis E (HE), oral vaccine nanoparticles using the truncated capsid protein p146 (aa460-605) are formulated and characterized. To improve the immunogenicity of p146, chitosan nanoparticles (CSNPs) are used as a mucosal delivery system. Next, the physical-chemical properties, cytotoxic effects in vitro, and immunogenicity in mice of the produced NPs are analyzed. The results show that the produced CS/p146 NPs are stable and well dispersive and display a near-spherical shape with a mean size of 200-300 nm. The findings also demonstrate high encapsulation efficiency (65-73.9%) and loading capacity (27.7-67.5%) of the formulated nanoparticles. Further, the CS/p146 NPs exhibit low cytotoxicity and an obvious sustained-release effect in vitro. Immunogenicity experiments in mice indicate that CS/p146 NPs can induce antigen-specific systemic and mucosal immune responses higher than the purified p146 do. Besides, the expression levels and mRNA transcription of Interleukin (IL)-4 in spleen cells of CS/p146 NPs-immunized mice are higher than those of p146, indicating that a Th2-mediated cellular immune response is activated by the CS/p146 NPs. Overall, the synthesized CS/p146 NPs display promising properties as a potential HE oral vaccine candidate.

Evaluation of the Antimicrobial and Antibiofilm Effect of Chitosan Nanoparticles as Carrier for Supernatant of Mesenchymal Stem Cells on Multidrug-Resistant Vibrio cholerae

AIM

The aim of the present study was to evaluate the in vitro antimicrobial and antibiofilm activity of chitosan nanoparticles (CS NPs) incorporated with mesenchymal stem cells-derived conditioned media (MSCs CM) on MDR Vibrio cholerae strains.

MATERIALS AND METHODS

Chitosan NPs were prepared and characterized by dynamic light scattering (DLS), scanning electron microscope (SEM) and zeta potential measurement. MSCs CM were prepared and entrapped into MSCs CM-CS NPs composite and its release efficiency was measured. Antibacterial efficacy of nano structures was determined by disk diffusion and broth microdilution methods. Antibiofilm activity was assessed by crystal violet assay.

RESULTS

BM-MSCs were characterized to be negative for CD34 and CD45 markers, positive for CD73 and CD44 markers, and able to differentiate into osteoblast and adipocyte cells. The mean particle size of 96.6% of chitosan NPs was 414.9 nm with a suitable zeta potential and SEM morphology. Entrapment efficiency of MSCs CM-CS NPs was 76.9%. Unstimulated MSCs CM-CS NPs composite as a novel and proficient therapeutic nanostructure against MDR V. cholerae strains showed the synergistic activity of the two components of MSCs CM and CS NPs, leading to greater bacterial killing compared to control groups. MSCs CM more efficiently inhibited biofilm formation, although MSCs CM-CS NPs was also appeared to be effective in inhibiting biofilm formation compared to CS NPs and control group.

CONCLUSION

The designed nanodrug composite showed the best release in conditions mimicking the physiological conditions of the intestinal lumen. Given the fact that no overuse or genetic event would cause the emergence of antimicrobial resistance against the MSCs CM-CS NPs nanodrug, it could be considered as a promising alternative for the treatment of MDR V. cholerae infections in clinical settings.

Immunization against Vibrio cholerae, ETEC, and EHEC with chitosan nanoparticle containing LSC chimeric protein

INTRODUCTION

Severe intestinal infections caused by V. cholerae, ETEC and EHEC have contributed to the mortality rate in developing countries. Vibrio Cholera, ETEC and EHEC bacterium with the production of CT, LT and Stx2 toxins respectively lead to severe watery and bloody diarrhea. This study aimed to investigate a trimeric vaccine candidate containing recombinant chimeric protein, encapsulate the protein in chitosan nanoparticles and assess its immunogenicity.

METHODS

The LSC recombinant gene was used. It is composed of LTB (L), STXB (S) and CTXB (C) subunits respectively. The LSC recombinant protein was expressed and purified and confirmed by western blotting. The purified protein was encapsulated in chitosan nanoparticles, and its size was measured. BalB/c mice were immunized in four groups through oral and injection methods by LSC protein. The antibody titer was then evaluated by ELISA, and finally, the challenge test of the toxins from all three bacteria was done on the immunized mouse.

RESULTS

After expression and purification LSC protein size of nanoparticles containing protein was measured at 104.6 nm. Nanoparticles were able to induce systemic and mucosal immune responses by generating a useful titer of IgG and IgA. The challenge results with LT, CT and Stx toxins showed that the LSC protein might partially neutralize the effect of toxins.

CONCLUSION

LSC chimeric protein with the simultaneous three essential antigens have a protective effect against the toxins produced by ETEC, EHEC and Vibrio cholera bacteria and it can be used in vaccines to prevent Diarrhea caused by these three bacteria.