Investigation on the preparation and application of chitosan/alginate microcapsules

Oral Probiotic Vaccine Expressing Koi Herpesvirus (KHV) ORF81 Protein Delivered by Chitosan-Alginate Capsules Is a Promising Strategy for Mass Oral Vaccination of Carps against KHV Infection

Koi herpesvirus (KHV) is highly contagious and lethal to cyprinid fish, causing significant economic losses to the carp aquaculture industry, particularly to koi carp breeders. Vaccines delivered through intramuscular needle injection or gene gun are not suitable for mass vaccination of carp. So, the development of cost-effective oral vaccines that are easily applicable at a farm level is highly desirable. In this study, we utilized chitosan-alginate capsules as an oral delivery system for a live probiotic (Lactobacillus rhamnosus) vaccine, pYG-KHV-ORF81/LR CIQ249, expressing KHV ORF81 protein. The tolerance of the encapsulated recombinant Lactobacillus to various digestive environments and the ability of the probiotic strain to colonize the intestine of carp was tested. The immunogenicity and the protective efficacy of the encapsulated probiotic vaccine was evaluated by determining IgM levels, lymphocyte proliferation, expression of immune-related genes, and viral challenge to vaccinated fish. It was clear that the chitosan-alginate capsules protected the probiotic vaccine effectively against extreme digestive environments, and a significant level (P < 0.01) of antigen-specific IgM with KHV-neutralizing activity was detected, which provided a protection rate of ca. 85% for koi carp against KHV challenge. The strategy of using chitosan-alginate capsules to deliver probiotic vaccines is easily applicable for mass oral vaccination of fish.IMPORTANCE An oral probiotic vaccine, pYG-KHV-ORF81/LR CIQ249, encapsulated by chitosan-alginate capsules as an oral delivery system was developed for koi carp against koi herpesvirus (KHV) infection. This encapsulated probiotic vaccine can be protected from various digestive environments and maintain effectively high viability, showing a good tolerance to digestive environments. This encapsulated probiotic vaccine has a good immunogenicity in koi carp via oral vaccination, and a significant level of antigen-specific IgM was effectively induced after oral vaccination, displaying effective KHV-neutralizing activity. This encapsulated probiotic vaccine can provide effective protection for koi carp against KHV challenge, which is handling-stress free for the fish, cost effective, and suitable for the mass oral vaccination of koi carp at a farm level, suggesting a promising vaccine strategy for fish.

Recent progress in preparation and agricultural application of microcapsules

Recent advances in life science technology have prompted the need to develop microcapsule delivery systems that can encapsulate many different functional or active materials such as drugs, peptides, and live cells, etc. The encapsulation technology is now commonly used in medicine, agriculture, food, and other many fields. The application of biodegradable microcapsule systems can not only effectively prevent the degradation of core materials in the body or the biological environment, but also improve the bioavailability, control the release and prolong the halftime or storage of core active materials. Various wall materials, preparation methods, encapsulation processes, and release mechanisms are covered in this review, as well as several main factors including pH values, temperatures, particle sizes, and additives, which can strongly influence the encapsulation efficiency, the strength, and release of microcapsules. The improvement of coating materials, preparation techniques, and challenges are also highlighted, as well as application prospects.

Historical Perspectives and Current Challenges in Cell Microencapsulation

The principle of immunoisolation of cells is based on encapsulation of cells in immunoprotective but semipermeable membranes that protect cells from hazardous effects of the host immune system but allows ingress of nutrients and outgress of therapeutic molecules. The technology was introduced in 1933 but has only received its deserved attention for its therapeutic application for three decades now.In the past decade important advances have been made in creating capsules that provoke minimal or no inflammatory responses. There are however new emerging challenges. These challenges relate to optimal nutrition and oxygen supply as well as standardization and documentation of capsule properties.It is concluded that the proof of principle of applicability of encapsulated grafts for treatment of human disease has been demonstrated and merits optimism about its clinical potential. Further innovation requires a much more systematic approach in identifying crucial properties of capsules and cellular grafts to allow sound interpretations of the results.