Oral immunization of BALB/c mice with recombinant Helicobacter pylori antigens and double mutant heat-labile toxin (dmLT) induces prophylactic protective immunity against H. pylori infection.

Helicobacter pylori infection and associated diseases remain a major public health problem worldwide. Much effort has been made over the last several decades in vaccine development, but there is no licensed vaccine on the market. We have previously reported that oral immunization with H. pylori lysates and double mutant heat-labile toxin (dmLT) affords prophylactic protection against H. pylori infection in mice. In the present study, we investigated the effects of oral immunization with recombinant H. pylori protein antigens (NAP/UreA/UreB) and dmLT on H. pylori challenge in BALB/c mice. We found that oral immunization with candidate antigens and dmLT significantly reduced the gastric colonization of H. pylori 6 weeks after challenge, as compared to unimmunized mice. Moreover, the subunit vaccine appeared to provide a better protection than the bacterial lysate vaccine. The immunized mice showed enhanced antigen-specific lymphocyte proliferation, and serum IgG and mucosal IgA responses. Furthermore, the immunization increased the proportion of CD4+ IL-17+ lymphocytes in spleen and mesenteric lymph nodes, and enhanced the production of IL-17, IL-16, IL-6 and TNF-α in lymphocyte culture supernatants. Taken together, our results suggest that oral vaccination with recombinant H. pylori antigens (NAP/UreA/UreB) and dmLT confers more effective prophylactic protection against H. pylori infection than whole bacterial lysates in BALB/c mice. The reduction of H. pylori colonization was associated with the induction of antigen-specific Th17 and local mucosal IgA immune responses.

Primary ectocervical epithelial cells display lower permissivity to Chlamydia trachomatis than HeLa cells and a globally higher pro-inflammatory profile.

The tumoral origin and extensive passaging of HeLa cells, a most commonly used cervical epithelial cell line, raise concerns on their suitability to study the cell responses to infection. The present study was designed to isolate primary epithelial cells from human ectocervix explants and characterize their susceptibility to C. trachomatis infection. We achieved a high purity of isolation, assessed by the expression of E-cadherin and cytokeratin 14. The infectious progeny in these primary epithelial cells was lower than in HeLa cells. We showed that the difference in culture medium, and the addition of serum in HeLa cultures, accounted for a large part of these differences. However, all things considered the primary ectocervical epithelial cells remained less permissive than HeLa cells to C. trachomatis serovar L2 or D development. Finally, the basal level of transcription of genes coding for pro-inflammatory cytokines was globally higher in primary epithelial cells than in HeLa cells. Transcription of several pro-inflammatory genes was further induced by infection with C. trachomatis serovar L2 or serovar D. In conclusion, primary epithelial cells have a strong capacity to mount an inflammatory response to Chlamydia infection. Our simplified purification protocol from human explants should facilitate future studies to understand the contribution of this response to limiting the spread of the pathogen to the upper female genital tract.

Parenteral immunization with a cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) adjuvanted Helicobacter pylori vaccine induces protective immunity against H. pylori infection in mice.

Under the trend of antibiotic resistance of H. pylori leading to the decrease of eradication rate, the development of a vaccine is the best choice to fight against H. pylori. In this study, we attempted to reduce the amounts of required antigens by using three different parenteral routes of immunization and an adjuvant cGAMP (cyclic guanosine monophosphate-adenosine monophosphate) to enhance the immunogenicity of the vaccine candidate. The immune protection and post-challenge immune responses were assessed and compared in mice immunized with recombinant Helicobacter pylori urease A, urease B, and neutrophil-activating protein adjuvanted with cGAMP. The gastric mucosal colonization by H. pylori was significantly reduced in mice immunized by intranasal and, to a less degree, subcutaneous route, but not by intramuscular route. All immunized mice, regardless of the route of immunization, displayed significant, but comparable, increases in antigen-specific serum IgG and mucosal IgA responses 5 weeks post-challenge. The magnitude of the vaccine-induced protection appeared to be associated with the level of antigen-specific Th1 and particularly Th17 responses, as IL-17 responses were only detected in intranasally immunized mice. Taken together, we explored and confirmed the possibility of using a novel adjuvant (cGAMP) to induce significant protective immunity with 10% of oral vaccine antigen dosage through parenteral immunization, especially intranasal immunization. This may provide an alternative approach to oral immunization for the development of effective H. pylori vaccines.

Oral immunization of mice with a multivalent therapeutic subunit vaccine protects against Helicobacter pylori infection.

Helicobacter pylori is a human class I carcinogen and no effective prophylactic or therapeutic H. pylori vaccine has yet been marketed. H. pylori can escape the host immune response, but the precise immune protection mechanisms in humans remain unknown. In this study, we developed a multivalent, subunit H. pylori vaccine candidate by formulating three commonly used H. pylori antigens, neutrophil-activating protein (NAP), urease subunit A (UreA) and subunit B (UreB) with the mucosal adjuvant, a double-mutant heat-labile toxin (dmLT) from Escherichia coli, and evaluated its immunogenicity and therapeutic efficacy in a mouse model of H. pylori infection. We found that oral immunization of H. pylori-infected mice significantly reduced gastric bacterial colonization at both 2 and 8 weeks after immunization. The reduction in bacterial burdens was accompanied with significantly increased serum antigen-specific IgG responses and mucosal IgA responses. Moreover, oral immunization also induced Th1/Th17 immune responses, which may play a synergistic role with the specific antibodies in the elimination of H. pylori. Thus, our vaccine candidate appears able to overcome the immune evasion mechanism of H. pylori, restore the suppression of Th2 immune responses with the induction of a strong humoral immune response. These results lay the foundation for the development of an optimized oral therapeutic H. pylori vaccine with increased immunogenicity of UreA and UreB, as well as providing long-term immunity.