Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) enhances the immune responses against Helicobacter pylori in BALB/c mice
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 administration. 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 response to H. pylori antigens and cGAMP immunization were significantly higher than those in the corresponding 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 antigens 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. 
 
 
Key words: 
cGAMP; Adjuvant; Helicobacter pylori; Vaccine