The Role of Helicobacter pylori Proinflammatory Outer Membrane Protein and Propolis in Immunomodulation on U937 Macrophage Cell Model

Identification of serologically active Helicobacter pylori antigens related to alterations in serum pepsinogen levels

Gastric adenocarcinoma is associated with Helicobacter pylori infection. The transition to a carcinogenic process is preceded by glandular atrophy and serum levels of pepsinogen I and II (PGI and PGII) correlate with this type of gastric lesions. Possible associations of serum PG levels in relation to the frequency of serological activity against H. pylori antigens were studied. Serum samples from patients with gastric pathology associated with H. pylori (n=26) and asymptomatic individuals as controls (n=37) were used. Seroactive antigens were identified by immunoblot using a protein extract of H. pylori. The antibody titers anti-H. pylori and the concentration of PGs in serum was determined by ELISA. Thirty-one seroactive antigens were identified, nine of which exhibited a differential frequency between both groups (116.7, 68.8, 61.9, 54.9, 45.6, 38.3, 36.5, 33.8 and 30.1kDa) and only 3 were related to altered levels of PGs in serum. In the control group, the seropositivity of the 33.8kDa antigen was related to an increase in PGII, while the 68.8kDa antigen was related to normal PG values (decreased PGII and elevated PGI/PGII levels) indicating that seropositivity to this antigen could be a protective factor to gastric pathology. The seropositivity of the 54.9kDa antigen was related to altered values of PGs indicative of inflammation and gastric atrophy (increased in PGII and decreased in PGI/PGII). The identification of serum alterations in pepsinogen levels related to seropositivity to H. pylori 33.8, 54.9 and 68.8kDa antigens sets a precedent for further study as possible prognostic serological biomarkers.

Extracellular vesicle-mediated regulation of macrophage polarization in bacterial infections

Extracellular vesicles (EVs) are nanoscale membrane-enveloped vesicles secreted by prokaryotic and eukaryotic cells, which are commonly defined as membrane vesicles (MVs) and exosomes, respectively. They play critical roles in the bacteria-bacteria and bacteria-host interactions. In infectious diseases caused by bacteria, as the first line of defense against pathogens, the macrophage polarization mode commonly determines the success or failure of the host's response to pathogen aggression. M1-type macrophages secrete pro-inflammatory factors that support microbicidal activity, while alternative M2-type macrophages secrete anti-inflammatory factors that perform an antimicrobial immune response but partially allow pathogens to replicate and survive intracellularly. Membrane vesicles (MVs) released from bacteria as a distinctive secretion system can carry various components, including bacterial effectors, nucleic acids, or lipids to modulate macrophage polarization in host-pathogen interaction. Similar to MVs, bacteria-infected macrophages can secrete exosomes containing a variety of components to manipulate the phenotypic polarization of "bystander" macrophages nearby or long distance to differentiate into type M1 or M2 to regulate the course of inflammation. Exosomes can also repair tissue damage associated with the infection by upregulating the levels of anti-inflammatory factors, downregulating the pro-inflammatory factors, and regulating cellular biological behaviors. The study of the mechanisms by which EVs modulate macrophage polarization has opened new frontiers in delineating the molecular machinery involved in bacterial pathogenesis and challenges in providing new strategies for diagnosis and therapy.

Evaluation of Helicobacter pylori OipA protein as a vaccine candidate and propolis as an adjuvant in C57BL/6 mice

OBJECTIVES

Outer inflammatory protein A (OipA) is an essential adhesin of Helicobacter pylori. We aimed to evaluate the effects of a recombinant OipA in the induction of crucial cytokines as a vaccine candidate and propolis as an adjuvant in C57BL/6 mice.

MATERIALS AND METHODS

C57BL/6 mice were divided into nine groups according to the disposition of antigen and adjuvant and route of administration: subcutaneous (sc) or gavage. The administrated recombinant purified OipA and propolis concentrations were 10 μg/ml and 40 μg/ml, respectively. After vaccination, we measured expression levels of IFN-γ and IL-4 cytokine genes in the spleen cells of mice by real-time PCR.

RESULTS

All results were contrasted with the negative sample. By sc injection, the expression of INF-γ was increased 3.5 and 2.9-fold for OipA and OipA plus propolis, respectively. By gavage 4.4 and 11-fold increase was found for OipA and OipA plus propolis, respectively. The administration of propolis by gavage showed more increase than Sc injection concerning the production of INF-γ. The 11-fold increase for injection of OipA plus propolis by gavage was comparable OipA plus Freund's adjuvant injected subcutaneously. This result suggested an excellent immunological response toward OipA concerning the production of INF-γ in mice. In all cases there were no notable IL-4 production increases.

CONCLUSION

The results confirm the efficiency of OipA in induction of IFN-γ production, and thereby the cellular immune response. Propolis could be a suitable adjuvant.