It is a pathogen, playing an important role in the aetiology of gastritis (especially active antral gastritis). Gastritis is a histopathologic term characterized by chronic inflammation of the stomach mucosa. It is classification based on the underlying cause (eg,
H. pylori infection is a major cause of gastric adenocarcinoma, specifically non-cardia gastric cancer. H. pylori infection also causes gastric mucosa-associated lymphoid tissue (MALT) lymphoma . Some
The prevalence of gastric cancers among
Gastric inflammation nearly always precedes the development of peptic ulceration, and is a critical component in initiating the multi-step progression towards gastric carcinogenesis due to this interaction between these three factors .
The pathogenesity of this bacterium depend on the production of several virulence factors. The most important ones are CagA (cytotoxic associated gene A) and VacA (vacuolizating cytotoxin A). The immunodominant CagA protein is encoded by genes called the cagA-PAI (pathogenicity island), a 40 kb genomic fragment containing ORFs (open reading frames) encoding approximately 31 genes that forms a type IV secretion system, which is found in 60–70% of
Regarding VacA, there is a significant polymorphism in this gene (vacA s, vacA i and vacA m). There are two types of the s (s1 and s2), i (i1 and i2), and m (m1 and m2) regions of
In most cases, the infection is asymptomatic and clinical manifestation appears in only 10-15% of infected individuals. This is due to virulence of
This will shed a light on the immune response to
2. Host immune response to
The immune response towards bacterial pathogens can be divided into an innate and an adaptive response.
2.1. Innate immune response to
Recognition of bacterial antigenic molecules is mediated by TLRs (Toll-like receptors) that are expressed by distinct cell types throughout the gastrointestinal tract, and play an important role in regulation of the innate immune response especially TLR4 It is expressed on antigen-presenting cells such as monocytes and dendritic cells. Bacterial contact with monocytes and other APCs leads to the secretion of proinflammatory cytokines such as TNF-
2.2. Adaptive immunity: cellular immune response and humoral response
2.2.1. Cellular immune response
Adaptive immune responses towards
Yuceyar etal 2002  found that there is no alteration in total T and B lymphocytes and CD4+ T, CD8+ T lymphocytes and natural killer cells of both duodenal ulcer and chronic antral gastritis patients compared to normal persons. Although there was a slight increase in the proportion of active T lymphocytes in duodenal ulcer and chronic antral gastritis groups comparing to healthy subjects the difference was not statistically significant. This indicate that there is no systemic alteration in the specific immune system in response to
2.2.2. Humoral immune response
184.108.40.206. Evasion of immune response by
Elimination of this key immunomodulatory cell may represent a
Vacuolating cytotoxin secreted by
In addition to that,
220.127.116.11. Vaccination against
H. pylori infection
There is a consent that vaccines are essential to limit the severity of this infection. Great development has been made since its detection 25 years ago the virulence factors and several aspects of the pathogenesis of the
Considering the side effects of oral adjuvants, researches have focused attention on making oral immunization safe and effective for human usage. Thus,
Although the intransal route of immunization seems the most efficient and effective route of mucosal immunization, it still has some disadvantages histologic inflammation in the olfactory bulb and cause paralysis of facial nerves . Intranasal route could also result in oral ingestion thus exposing the subject to various side effects and toxicities. Eriksson et al.  found that CTA1-DD adjuvant was to be safe for intranasal administration without any accumulation in the nervous tissue.
Other modalities of administering vaccines such as the intraperitoneal (i.p.) and subcutaneous (s.c.) routes are also being done. Mice were vaccinated i.p. using
Urease is important as a vaccine antigen has been confirmed by numerous studies in mice, ferrets, and non-human primates . Urease conferred protection against helicobacter infection when delivered either as a native protein or as an enzymatically inactive recombinant protein . Therapeutic immunisation with urease has recently been reported in ferrets naturally infected with
Other method of delivery of the antigen used in mice by immunisation with genetically engineered bacteria expressing
Zhang etal, 2013  used recombinant technology, Lactococcus lactis (L. lactis) could serve as an antigen-delivering vehicle for the development of edible
Altman etal, 2013  demonstrated that synthetic glycoconjugates based on delipidated lipopolysaccharide (LPS) of
An important consideration in the development of subunit
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