Steven J. Czinn

Vaccinating against Helicobacter pylori infection

Helicobacter pylori infection of the gastric mucosa remains a cause of significant morbidity and mortality almost 30 years after its discovery. H. pylori infection can lead to several gastric maladies, including gastric cancer, and although antimicrobial therapies for the infection exist, the cost of treatment for gastric cancer and the prognosis of individuals who present with this disease make vaccine development a cost effective alternative to bacterial eradication. Experimental mucosal and systemic H. pylori vaccines in mice significantly reduce bacterial load and sometimes provide sterilizing immunity. Clinical trials of oral vaccines consisting of H. pylori proteins with bacterial exotoxin adjuvants or live attenuated bacterial vectors expressing H. pylori proteins induce adaptive immune mechanisms but fail to consistently reduce bacterial load. Clinical trials and murine studies demonstrate that where H. pylori is killed, either spontaneously or following vaccination, the host demonstrated cellular immunity. Improved efficacy of vaccines may be achieved in new trials of vaccine formulations that include multiple antigens and use methods to optimize cellular immunity. Unfortunately, the industrial sponsors that served as the primary engine for much of the previous animal and human research have withdrawn their support. A renewed or expanded commitment from the biotechnology or pharmaceutical industry that could exploit recent advances in our understanding of the host immune response to H. pylori is necessary for the advancement of an H. pylori vaccine.

Gastroesophageal Reflux Disease in Neonates and Infants

Gastroesophageal reflux (GER) is defined as the involuntary retrograde passage of gastric contents into the esophagus with or without regurgitation or vomiting. It is a frequently experienced physiologic condition occurring several times a day, mostly postprandial and causes no symptoms. These infants are also called ‘happy spitters’. GER disease (GERD) occurs when reflux of the gastric contents causes symptoms that affect the quality of life or pathologic complications, such as failure to thrive, feeding or sleeping problems, chronic respiratory disorders, esophagitis, hematemesis, apnea, and apparent life-threatening events.About 70–85xa0% of infants have regurgitation within the first 2xa0months of life, and this resolves without intervention in 95xa0% of infants by 1xa0year of age. The predominant mechanism causing GERD is transient lower esophageal sphincter (LES) relaxation, which is defined as an abrupt decrease in LES pressure to the level of intragastric pressure, unrelated to swallowing and of relatively longer duration than the relaxation triggered by a swallow.Regurgitation and vomiting are the most common symptoms of infant reflux. A thorough history and physical examination with attention to warning signals suggesting other causes is generally sufficient to establish a clinical diagnosis of uncomplicated infant GER. Choking, gagging, coughing with feedings or significant irritability can be warning signs for GERD or other diagnoses. If there is forceful vomiting, laboratory and radiographic investigation (upper gastrointestinal series) are warranted to exclude other causes of vomiting. Irritability coupled with back arching in infants is thought to be a non-verbal equivalent of heartburn in older children. Other causes of irritability, including cow’s milk protein allergy, neurologic disorders, constipation and infection, should be ruled out. The presentation of cow’s milk protein allergy overlaps with GERD, and both conditions may co-exist in 42–58xa0% of infants. In these infants, symptoms decrease significantly within 2–4xa0weeks after elimination of cow’s milk protein from the diet. For non-complicated reflux, no intervention is required for most infants.Effective parental reassurance and education regarding regurgitation and lifestyle changes are usually sufficient to manage infant reflux. Sandifer syndrome, apnea and apparent life-threatening events are the extraesophageal manifestations of GERD in infants.Pharmacotherapeutic agents used to treat GERD encompass antisecretory agents, antacids, surface barrier agents and prokinetics. Currently, North American Society for Pediatric Gasroenterology, Hepatology and Nutrition (NASPGHAN) and European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) practice guidelines concluded that there is insufficient evidence to justify the routine use of prokinetic agents. Esomeprazole (Nexium) is now approved in the US for short-term treatment of GERD with erosive esophagitis in infants aged from 1 to 12xa0months. Although Nissen fundoplication is now well established as a treatment option in selected cases of GERD in children, its role in neonates and young infants is unclear and is only reserved for selective infants who did not respond to medical therapy and have life-threatening complications of GERD.

Mucosal-Associated Invariant T Cells in the Human Gastric Mucosa and Blood: Role in Helicobacter pylori Infection

Mucosal-associated invariant T (MAIT) cells represent a class of antimicrobial innate-like T cells that have been characterized in human blood, liver, lungs, and intestine. Here, we investigated, for the first time, the presence of MAIT cells in the stomach of children, adults, and the elderly undergoing routine endoscopy and assessed their reactivity to Helicobacter pylori (H. pyloriu2009–u2009Hp), a major gastric pathogen. We observed that MAIT cells are present in the lamina propria compartment of the stomach and display a similar memory phenotype to blood MAIT cells. We then demonstrated that gastric and blood MAIT cells are able to recognize H. pylori. We found that CD8+ and CD4−CD8− (double negative) MAIT cell subsets respond to H. pylori-infected macrophages stimulation in a MR-1 restrictive manner by producing cytokines (IFN-γ, TNF-α, IL-17A) and exhibiting cytotoxic activity. Interestingly, we observed that blood MAIT cell frequency in Hp+ve individuals was significantly lower than in Hp−ve individuals. However, gastric MAIT cell frequency was not significantly different between Hp+ve and Hp−ve individuals, demonstrating a dichotomy between blood and gastric tissues. Further, we observed that the majority of gastric MAIT cells (>80%) expressed tissue-resident markers (CD69+ CD103+), which were only marginally present on PBMC MAIT cells (<3%), suggesting that gastric MAIT cells are readily available to respond quickly to pathogens. These results contribute important new information to the understanding of MAIT cells function on peripheral and mucosal tissues and its possible implications in the host response to H. pylori.

Immunity, inflammation, and vaccines for Helicobacter pylori.

Helicobacter pylori colonizes mucosa, activates Toll‐like and Nod‐like receptors, and usually elicits a gastric T‐helper 1/17 (Th1/Th17) type of immune response. Among several bacterial factors, the secreted peptidyl prolyl cis, trans‐isomerase of H. pylori represents a key factor driving Th17 inflammation. A complex and fascinating balance between H. pylori and host factors takes part in the gastric niche and is responsible for the chronicity of the infection. Novel insights into the innate and adaptive responses against H. pylori, dealing with gastric epithelial cells, cytokines, and immune evasion have been elucidated over the past year and are discussed for the development of an effective vaccine.

Vaccine-induced immunity against Helicobacter pylori in the absence of IL-17A

Background:u2002 Helicobacter pylori (H. pylori) is a gram negative bacterium that can cause diseases such as peptic ulcers and gastric cancer. IL‐17A, a proinflammatory cytokine that can induce the production of CXC chemokines for neutrophil recruitment, has recently been shown to be elevated in both H. pylori‐infected patients and mice. Furthermore, studies in mouse models of vaccination have reported levels significantly increased over infected, unimmunized mice and blocking of IL‐17A during the challenge phase in immunized mice reduces protective immunity. Because many aspects of immunity had redundant or compensatory mechanisms, we investigated whether mice could be protectively immunized when IL‐17A function is absent during the entire immune response using IL‐17A and IL‐17A receptor knockout (KO) mice immunized against H. pylori.

Th1-Mediated Immunity against Helicobacter pylori Can Compensate for Lack of Th17 Cells and Can Protect Mice in the Absence of Immunization

Helicobacter pylori (H. pylori) infection can be significantly reduced by immunization in mice. Th17 cells play an essential role in the protective immune response. Th1 immunity has also been demonstrated to play a role in the protective immune response and can compensate in the absence of IL-17. To further address the potential of Th1 immunity, we investigated the efficacy of immunization in mice deficient in IL-23p19, a cytokine that promotes Th17 cell development. We also examined the course of Helicobacter infection in unimmunized mice treated with Th1 promoting cytokine IL-12. C57BL/6, IL-12 p35 KO, and IL-23 p19 KO mice were immunized and challenged with H. pylori. Protective immunity was evaluated by CFU determination and QPCR on gastric biopsies. Gastric and splenic IL-17 and IFNγ levels were determined by PCR or by ELISA. Balb/c mice were infected with H. felis and treated with IL-12 therapy and the resulting gastric bacterial load and inflammatory response were assessed by histologic evaluation. Vaccine induced reductions in bacterial load that were comparable to wild type mice were observed in both IL-12 p35 and IL-23 p19 KO mice. In the absence of IL-23 p19, IL-17 levels remained low but IFNγ levels increased significantly in both immunized challenged and unimmunized/challenged mice. Additionally, treatment of H. felis-infected Balb/c mice with IL-12 resulted in increased gastric inflammation and the eradication of bacteria in most mice. These data suggest that Th1 immunity can compensate for the lack of IL-23 mediated Th17 responses, and that protective Th1 immunity can be induced in the absence of immunization through cytokine therapy of the infected host.

Characterization and Functional Properties of Gastric Tissue-Resident Memory T Cells from Children, Adults, and the Elderly

T cells are the main orchestrators of protective immunity in the stomach; however, limited information on the presence and function of the gastric T subsets is available mainly due to the difficulty in recovering high numbers of viable cells from human gastric biopsies. To overcome this shortcoming we optimized a cell isolation method that yielded high numbers of viable lamina propria mononuclear cells (LPMC) from gastric biopsies. Classic memory T subsets were identified in gastric LPMC and compared to peripheral blood mononuclear cells (PBMC) obtained from children, adults, and the elderly using an optimized 14 color flow cytometry panel. A dominant effector memory T (TEM) phenotype was observed in gastric LPMC CD4+ and CD8+ T cells in all age groups. We then evaluated whether these cells represented a population of gastric tissue-resident memory T (TRM) cells by assessing expression of CD103 and CD69. The vast majority of gastric LPMC CD8+ T cells either co-expressed CD103/CD69 (>70%) or expressed CD103 alone (~20%). Gastric LPMC CD4+ T cells also either co-expressed CD103/CD69 (>35%) or expressed at least one of these markers. Thus, gastric LPMC CD8+ and CD4+ T cells had the characteristics of TRM cells. Gastric CD8+ and CD4+ TRM cells produced multiple cytokines (IFN-γ, IL-2, TNF-α, IL-17A, MIP-1β) and up-regulated CD107a upon stimulation. However, marked differences were observed in their cytokine and multi-cytokine profiles when compared to their PBMC TEM counterparts. Furthermore, gastric CD8+ TRM and CD4+ TRM cells demonstrated differences in the frequency, susceptibility to activation, and cytokine/multi-cytokine production profiles among the age groups. Most notably, children’s gastric TRM cells responded differently to stimuli than gastric TRM cells from adults or the elderly. In conclusion, we demonstrate the presence of gastric TRM, which exhibit diverse functional characteristics in children, adults, and the elderly.

Partial Protection against Helicobacter pylori in the Absence of Mast Cells in Mice

ABSTRACT The goal of this study is to evaluate the contribution of mast cells to Helicobacter pylori immunity in a model of vaccine-induced protection. Mast cell-deficient KitlSl/KitlSl-d and control mice were immunized with H. pylori sonicate plus cholera toxin and challenged with H. pylori, and the bacterial loads, inflammatory infiltrates, and cytokine responses were evaluated and compared at 1, 2, and 4 weeks postchallenge. In vitro stimulation assays were performed using bone marrow-derived mast cells, and recall assays were performed with spleen cells of immunized mast cell-deficient and wild-type mice. Bacterial clearance was observed by 2 weeks postchallenge in mast cell-deficient mice. The bacterial load was reduced by 4.0 log CFU in wild-type mice and by 1.5 log CFU in mast cell-deficient mice. Neutrophil numbers in the gastric mucosa of immune KitlSl/KitlSl-d mice were lower than those for immune wild-type mice (P < 0.05). Levels of gastric interleukin-17 (IL-17) and tumor necrosis factor alpha (TNF-α) were also significantly lower in immune KitlSl/KitlSl-d mice than in wild-type mice (P < 0.001). Immunized mast cell-deficient and wild-type mouse spleen cells produced IFN-γ and IL-17 in response to H. pylori antigen stimulation. TNF-α and CXC chemokines were detected in mast cell supernatants after 24 h of stimulation with H. pylori antigen. The results indicate that mast cells are not essential for but do contribute to vaccine-induced immunity and that mast cells contribute to neutrophil recruitment and inflammation in response to H. pylori.

Genome Sequences of 65 Helicobacter pylori Strains Isolated from Asymptomatic Individuals and Patients with Gastric Cancer, Peptic Ulcer Disease, or Gastritis

Helicobacter pylori, inhabitant of the gastric mucosa of over half of the world population, with decreasing prevalence in the U.S., has been associated with a variety of gastric pathologies. However, the majority of H. pylori-infected individuals remain asymptomatic, and negative correlations between H. pylori and allergic diseases have been reported. Comprehensive genome characterization of H. pylori populations from different human host backgrounds including healthy individuals provides the exciting potential to generate new insights into the open question whether human health outcome is associated with specific H. pylori genotypes or dependent on other environmental factors. We report the genome sequences of 65 H. pylori isolates from individuals with gastric cancer, preneoplastic lesions, peptic ulcer disease, gastritis, and from asymptomatic adults. Isolates were collected from multiple locations in North America (USA and Canada) as well as from Columbia and Japan. The availability of these H. pylori genome sequences from individuals with distinct clinical presentations provides the research community with a resource for detailed investigations into genetic elements that correlate either positively or negatively with the epidemiology, human host adaptation, and gastric pathogenesis and will aid in the characterization of strains that may favor the development of specific pathology, including gastric cancer.

Current Status and Prospects for a Helicobacter pylori Vaccine

Helicobacter pylori infection contributes to a variety of gastric diseases. H pylori-associated gastric cancer is diagnosed in advanced stages, and a vaccine against H pylori is desirable in parts of the world where gastric cancer remains a common form of cancer. Some of the strategies of vaccine development used in animals have been tested in several phase 3 clinical trials; these trials have been largely unsuccessful, although H pylori-specific immune responses have been induced. New insights into promoting immunity and overcoming the immunosuppressive nature of H pylori infection are required to improve the efficacy of an H pylori vaccine.