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Chitosan as adjuvant for vaccines

Adjuvants in vaccines are potent enhancers, which ensure that even small amounts of pathogens induce a permanent immune response. They are particularly necessary for inactivated vaccines and vaccines with antigen subunits. Several studies investigated chitosan as an adjuvant or antigen delivery system in various formulations (gels, aqueous dispersion, micro- and nanoparticles).

There are two different approaches in developing adjuvants. One way is to develop drug delivery systems that improve the uptake and presentation of the antigen. The other is the development of immunopotentiators, which help to activate the innate immune system. In the past few years, the combination of the two ways has also shown promising results. The first study is about such a combination of Salmonella Typhi and Chitosan.

Development and in vitro evaluation of a new adjuvant system containing Salmonella Typhi and chitosan

Yüksel S. et al. International Journal of Pharmaceutics, 2020, doi:

Adjuvants are added to improve the immunogenicity of high-purity vaccine antigens without compromising the safety of the vaccine. In recent years, adjuvants that consist of a delivery system and immunopotentiators have been preferred.

In the presented study, a new adjuvant / delivery system consisting of Salmonella Typhi porins and chitosan was developed for stimulation of immune response. For this purpose, cationic chitosan-based gels, micro- and nanoparticles with a high loading efficiency for porins were produced. Water-soluble chitosan HCl with a 70-90% degree of deacetylation was used. The porins, pore-forming transmembrane proteins of the outer bacterial membrane, were purified from Salmonella Typhi ATCC 9993. Gels with a chitosan concentration of 0.5% (w / v), microparticles with 0.1% (w / v) chitosan and nanoparticles with 0.2% (w / v) chitosan were produced. All three formulations were made with and without porin. The uptake of the formulations was examined by confocal laser scanning microscopy. Macrophage activation was tested in vitro by measuring the surface marker and the cytokine release in J774A.1 macrophage murine cells.


  • Significant uptake of the chitosan-porin combination by the macrophage cells
  • no intake of Porin alone
  • Induction of CD80, CD86 and MHC-II expression depending on the particle size of the formulation
  • Increase in TNF-α and IL-6 levels through the chitosan-porin combination

Conclusion: The porin-chitosan combination is a promising adjuvant system with an immunostimulant effect to improve vaccines.


Reproductive and Behavioral Evaluation of a New Immunocastration Dog Vaccine

Siel, D.; Ubilla, M.J.; Vidal, S.; Loaiza, A.; Quiroga, J.; Cifuentes, F.; Hardman, T.; Lapierre, L.; Paredes, R.; Sáenz, L., Animals 2020, 10, 226. doi:10.3390/ani10020226

In many countries, the increasing number of stray dogs is a serious problem demanding for alternative methods to surgical castration as a method for population control. An alternative is Immunocastration, where the formation of sex hormones is prevented by injecting an analogue of the gonadotropin-releasing hormone (GnRH). In this study in Chile, the effectiveness of an immunocastration vaccine for dogs with regard to reproduction and behavior was investigated in two experiments. In the first trial, the immune response was investigated in 9 male beagle dogs over a period of nine months under controlled conditions. Seven animals were vaccinated with 500 µg GnRXG/Q (recombinant protein) and 500 µg low molecular weight chitosan as adjuvants. The control group received a placebo. In the second trial, 32 dogs that were in the care of owners, were vaccinated. It was examined if certain unwanted behaviors that are triggered by sex hormones change positively.

Results Trial 1

  • Production of specific antigens that remained until end of study (9 month)
  • Reduced testosterone levels and changes in the spermiogram

Results Trial 2

  • Specific immunity until end of trial (5 Month)
  • Reduced sexual agonistic (threatening behavior, biting, offensive barking) and marking behavior

Conclusion: The study shows that the new developed vaccine for immunocastration of dogs is safe and effective. The gonadal functionality and sexual, agonistic behavior were reduced. The developed vaccine could be an alternative to control reproduction of stray dogs.


drug delivery, nanoparticles, adjuvant, Vaccines, Chitosan HCl

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