Zinc Hydroxide As A New Vaccine Adjuvant Enhance The Humoral Immune Response Of HAV Antigen

Zn is an essential trace element for all organisms.In human subjects,body growth and development is strictly dependent on Zn.The nervous,reproductive and immune systems are particularly influenced by Zn deficiency,as well as by increased levels of Zn.The relationship between Zn and the immune system is complex,since there are four different types of influence associated with Zn.(1) The dietary intake and the resorption of Zn depend on the composition of the diet and also on age and disease status.(2) Zn is a cofactor in more than 300 enzymes influencing various organ functions and having a secondary effect on the immune system.(3) Direct effects of Zn on the production,maturation and function of leucocytes.(4) Zn influences the function of immunostimulants used in the experimental systems.It was reported that the zinc not only participate in the redox of the organism,but also take part in the immune modulation.A better effect was observed after proper pharmacological Zn supplementation adding to normal therapy in several cases, which indicated satisfactory results.Besides,the beneficial therapeutic effects of zinc in on infectious diseases,autoimmune diseases and vaccination have already been confirmed now.The hotspot of vaccine development is to develop an ideal adjuvant which have the advantages over validity,targeting,safety and economy.At present,it is only aluminium salt as a vaccine adjuvant that has been approved in clinic.By the mechanisms of repository of antigen and immunostimulation,the aluminium salt is able to induce the immune response effectively,however,the defects in safety and targeting are still unsolved.For other potential candidates studied as this kind of adjuvant,their clinic application was not be approved for their problems in validity, safety,and economy.zinc hydroxide,which is not only similar with aluminium adjuvant in isoelectric point and water-solubility,but also easy to be prepared and low in costs.So that we also selected this agent as our research object.During the exploration on preparation for this kind of zinc salt,we found out the appropriate reactants and optimal reaction conditions.Finally,satisfactory tiny zinc hydroxide granules were made by the use of zinc acetate and the ammonia water.In this research,the inactivated HAV antigen and the Al(OH)₃-adjuvant group was used as the control group and the mixtures composing by different dosages of zinc hydroxide and inactivated HAV antigen to inject ICR mice.The anti-HAV IgG in mice serum was examined by ELISA at different time after inoculation and compared with no-adjuvant group and Al(OH)₃-adjuvant group.According to the data analysis,all the experimental groups produced the anti-HAV IgG in 4-week period,and the titers of specific IgG reached the peak point generally at the 8^th week. 1mg zinc hydroxide seems induced the optimal immune responds,which was from the two facts:1) the antibody-titer-level of 1mg Zn(OH)₂-group is obviously higher than the HAV- group within 28 weeks(P＜0.05).2)the relatively high level of antibody titer could be maintained continually during that time.Moreover,this group of mice produced higher level of antibody titer than the aluminum-adjuvant group.After 12^th week,other dose groups also showed significantly higher immune response than corresponding aluminium-group(P＜0.05).At the 4^th,24^th and 28^th week,majority of Zn-adjuvant groups' antibody titers were significantly higher than the Al-adjuvant group(P＜0.05).These results proved that the zine hydroxide can enhance the immunity of HAV antigen.It is clear that the acidophile cells can be recruited by the aluminum adjuvant to the injection site,which might increase the level of specificity antigen and total IgE, inducing the allergy reaction induced by IgE.To judging the sensitization of zinc hydroxide,we sensitized the BALB/c mice with the mixture of 1mg Zn(OH)₂(the most effective dosage)and 100μg the egg albumen.Compared with the aluminum-adjuvant group,the IgE level of that group was significantly lower on the 8^th and 14^th day after the primary immunity.We then found that some mice immunized with aluminium adjuvant appeared depilation phenomenon.The brain pathological results showed a microglia nodule which means the aluminium adjuvant may damage nervous system.However,there is no abnormality in the pathology results of zinc-hydroxide group,suggesting that the safety of Zn(OH)₂ is better than normal Al(OH)₃ adjuvant.Finally,it was proved in this research that the zinc hydroxide can stimulate immune response effectively while inducing weak allergic response and toxicity.The results showed a novel orientation for the developing and studying of new vaccine adjuvant.