Helicobacter pylori Recombinant CagA Regulates Th1/Th2 Balance in a BALB/c Murine Model

Helicobacter pylori is recognized as one of the prevalent causes of human gastric infection. In the present study, the role of mixed immunization with H. pylori lipopolysaccharide (LPS) and recombinant cytotoxin-associated gene A (rCagA) as a stimulator of host immune responses was determined.

BALB/c mice were immunized with different formulations by the systemic administration at 14-day intervals. The effects of the formulations plus CpG adjuvants were assessed before and post-immunization in separated studies. Moreover, the expression of Th1/Th2 cytokines was quantified in sera of immunized mice using reverse transcription polymerase chain reaction (RTPCR) test and the protein levels confirmed with enzyme linked immunosorbent assay (ELISA). Finally, the specific antibody levels in sera were studied by ELISA and the tendency of cellular response was examined by IgG1/IgG2a ratio.

Data of Western blotting verified the presence of constructed protein. Analysis of lymphocyte proliferation showed that CpG-conjugated rCagA increases lymphocytes proliferation compared to the control group. Also, it was shown that formulations containing LPS and rCagA promote a Th1 response indicated by interferon-gamma expression and induced Th1/ Th2 balance. Additionally, the specific IgG1, total IgG and IgG2a levels elevated in response to all treatments. Ultimately, the IgG2a/IgG1 ratio in the mice immunized with rCagA-containing formulations increased.

These results indicated that rCagA protein carried with CpG adjuvant not only maintained its antigenicity throughout the experiment but also induced robust Th1-biased immune responses. Therefore, it holds promise for the production of an efficient vaccine against H. pylori infection.