Objective To evaluate the immunopotentiating effect of cyclic guanosine monophos-phate-adenosine monophosphate (cGAMP) as an adjuvant on norovirus (GⅡ. 4) virus like particles (VLPs) in the development of norovirus vaccine. Methods BALB/c mice were intramuscularly immunized with norovirus (GⅡ.4) VLPs composed of capsid protein VP1 in combination with cGAMP or Al(OH)3. Norovirus VLPs-specific antibodies in serum were detected by ELISA. A synthetic histo-blood group antigen (HBGA)-VLPs blocking assay was used to analyze neutralizing antibodies against norovirus VLPs in serum samples. Results Immunization with norovirus VLPs in the presence of cGAMP induced a strong humoral immune response in BALB/c mice. Levels of specific IgG antibodies in serum induced by using cGAMP as the adjuvant were significantly higher than those induced by using Al(OH)3adjuvant when immunization of BALB/c mice with the same dosage of VLPs. The antibody level induced by 1 μg of VLPs in combination with cGAMP was equivalent to that elicited by 10 μg of VLPs combined with Al(OH)3adjuvant. Results of the synthetic HBGA-VLPs blocking assay showed that the blocking rate in cGAMP+VLPs immunization group were significantly higher than that in Al(OH)3+VLPs immunization group when using the same dosage of VLPs. No significant difference in blocking rate was observed between cGAMP+VLPs(1 μg) and Al(OH)3+VLPs (10 μg) immunization groups. Conclusion cGAMP significantly enhanced the specific humoral immune response induced by norovirus (GⅡ.4) VLPs in mice as compared with Al(OH)3adjuvant. It might be used as a novel adjuvant to replace the traditional aluminum adjuvant in the development of norovir-us vaccine.

Objective To evaluate the adjuvant activities of cyclic guanosine monophosphate-adenosine monophosphate ( cGAMP) in enhancing humoral and cellular responses against Helicobacter pylori ( H. pylori) . Methods BALB/c mice were immunized with the protein antigens including UreA, UreB and NapA of H. pylori in combination with cGAMP as the adjuvant on 0 d and 14 d by subcutaneous administra-tion. Then, the serum-specific antibody responses were evaluated by ELISA. Flow cytometry ( FCM) and enzyme-linked immunospot assay ( ELISpot) were used to detect the cellular immune responses occurred in spleen and mesenteric lymph nodes (MLN). Results Subcutaneous administration of protein antigens of H. pylori together with cGAMP induced strong humoral and cellular immune responses in BALB/c mice. The levels of serum-specific IgG antibodies induced by adding cGAMP as the adjuvant were significantly higher than those by immunizing with antigens alone. The levels of splenic IFN-γ-producing lymphocytes in re-sponse to H. pylori antigens and cGAMP immunization were significantly higher than those in the correspond-ing groups without using cGAMP. Conclusion By using cGAMP as an adjuvant, H. pylori antigens could elicit significantly stronger humoral and cellular immune responses in mice than those induced by the anti-gens only. As a stable small molecular compound with strong adjuvant activity, cGAMP has the potential to be used for the development of H. pylori vaccine.

Objective To observe the protective effects of oral immunization with Helicobacter pylori (Hp) lysates in combination with mucosal adjuvant dmLT (double mutant heat-labile toxin) against Hp infection in a BALB/ c mouse model and to analyze the features of induced immune responses. Methods BALB/ c mice were orally immunized with Hp lysate (Sydney strain 1, SS1 strain) and dmLT adjuvant, and then innoculated with live Hp strains through oral gavage. A control group was set up by oral administration of normal saline (200 μl/ mouse). The colonization of Hp strains in the stomachs of mice was measured six weeks after bacterial inoculation. Samples of serum, spleen, mesenteric lymph node (MLN), small intes-tine, cecum and feces were collected from mice to analyze the features of induced immune responses. Re-sults The colonization of Hp strains in the stomachs of the immunized mice was significantly decreased as compared with that of the control group. Increased specific IgG antibody responses which were predominantly of IgG1 subtype were detected in the serum samples of the immunized mice and the IgG1 / IgG2a ratio was significantly higher than that of the control group. Elevated secretory IgA (sIgA) was detected in the samples of small intestine, cecum and feces in the immunization group, especially in the small intestine samples, while no significant change in sIgA secretion was observed in the control group. The percentages of IL-17+CD4+ T cells in spleen and mesenteric lymph nodes of the immunization group were significantly higher than those of the control group. Conclusions Oral immunization with Hp lysates in combination with adjuvant dmLT induced mucosal and systemic immune responses and enhanced the resistance to Hp colonization in BALB/ c mice, which was associated with the significantly increased Th17 immune responses and Th2 polari-zation. This study provided reference for further evaluation of dmLT as a mucosal adjuvant in the develop-ment of recombinant protein vaccines against Hp infection.