Associations Between CagA, VacA, and the Clinical Outcomes of Helicobacter Pylori Infections in Okinawa, Japan.

Helicobacter pylori, which is involved in the pathogenesis of gastroduodenal disease, produces CagA and VacA as major virulence factors. CagA is classified into East Asian and Western types based on the number and sequences of its Glu-Pro-Ile-Tyr-Ala motifs. The vacA gene has three polymorphic regions: the signal (s), intermediate (i), and middle (m) regions. The lowest gastric cancer mortality rate is seen in Okinawa. On the Japanese mainland (Honshu), most H. pylori produce s1/m1-VacA, which exhibits strong toxicity, and East Asian-type CagA. However, the H. pylori detected in Okinawa produces s1/m2-VacA, which exhibits weak toxicity, or s2/m2-VacA, which is non-toxic, and Western-type CagA. Studies about the i-region of vacA have been performed around the world, but there have been few such studies in Japan. Therefore, the aim of this study was to assess the relationships between the clinical outcomes of H. pylori infections in Okinawa, vacA (especially the i-region genotype), and cagA. H. pylori strains that were collected from patients with gastric cancer or gastric ulcers in Okinawa only produced the i1-type VacA virulence factor. The vacuolating cytotoxin activity of i1-type VacA was stronger than that of i2-type VacA, suggesting that the i-region genotype of vacA is closely associated with vacuolating cytotoxin activity. These results indicate that the i-region genotype of vacA is a useful marker of both H. pylori virulence and the clinical outcomes of H. pylori infections in Okinawa, Japan.

Diversity of the cagA gene of Helicobacter pylori strains from patients with gastroduodenal diseases in the Philippines.

Helicobacter pylori CagA protein is considered a major virulence factor associated with gastric cancer. There are two major types of CagA proteins: the Western and East Asian CagA. The East Asian CagA-positive H. pylori infection is more closely associated with gastric cancer. The prevalence of gastric cancer is quite low in the Philippines, although Philippine populations are considered to originate from an East Asia source. This study investigates the characteristics of the cagA gene and CagA protein in Philippine H. pylori strains and compares them with previously characterized reference strains worldwide. The full-length cagA gene was sequenced from 19 Philippine isolates and phylogenetic relationships between the Philippine and 40 reference strains were analyzed. All Philippine strains examined were cagA positive, and 73.7% (14/19) strains were Western CagA-positive. The phylogenetic tree based on the deduced amino acid sequence of CagA indicated that the Philippine strains were classified into the two major groups of CagA protein: the Western and the East Asian group. These findings suggest that the modern Western influence may have resulted in more Western type H. pylori strains in the Philippines. Therefore, H. pylori-infected Filipinos can be considered to be at a low risk of developing gastric cancer.

The effects of Helicobacter pylori eradication on body mass index and dyspeptic symptoms.

BACKGROUND AND AIM: The relationship between Helicobacter pylori infection and body mass index (BMI) and dyspeptic symptoms is controversial. We investigated the changes in BMI and dyspeptic symptoms after H. pylori eradication among stages of atrophic gastritis classified according to the serum pepsinogen (PG) I/II ratio. METHODS: One hundred and sixty-three H. pylori-positive patients underwent eradication therapy for H. pylori. Serum PG I and II concentrations were measured before treatment, and the PG I/II ratio was classified into three groups: PG I/II ratio <2.0, PG I/II ratio >or=2.0 and <4.0, and PG I/II ratio >or=4.0 were considered to be low, middle, and high, respectively. Their BMI and abdominal symptoms were checked before, 1 and 5 years after treatment, and these changes were investigated among the three groups. RESULTS: The mean BMI changes 1 year after treatment in the low PG I/II ratio group were significantly higher than those in other groups. Most abdominal symptoms in the high PG I/II ratio group were most severe before eradication but improved significantly after eradication. CONCLUSIONS: The effects of H. pylori eradication on BMI and dyspeptic symptoms may be different according to the serum PG I/II ratio before eradication.

Relationship between the diversity of the cagA gene of Helicobacter pylori and gastric cancer in Okinawa, Japan.

BACKGROUND: Helicobacter pylori CagA protein is considered to be one of the virulence factors associated with gastric cancer. CagA is injected into gastric epithelial cells, undergoes tyrosine phosphorylation, and binds to Src homology 2 domain-containing protein-tyrosine phosphatase (SHP-2). Two major subtypes of CagA have been observed in the SHP-2-binding site, the Western and East Asian types. The East Asian-type CagA binds to SHP-2 more strongly than the Western-type CagA. The diversity of CagA, which collectively determines the binding affinity of CagA to SHP-2, may be an important variable in determining the clinical outcome of infection by different H. pylori strains. METHODS: We investigated the relationship between the diversity of CagA and clinical outcome in Okinawa, Japan. A total 24 strains, 13 gastric cancer strains and 11 duodenal ulcer strains, were studied. We sequenced full-length cagA genes and analyzed the phylogenetic relationships between Okinawa isolates and previously characterized Western H. pylori strains. RESULTS: All isolates examined were cagA positive. The prevalence of East Asian CagA-positive strains was significantly higher in patients with gastric cancer (84.6%) than in patients with duodenal ulcer (27.3%) (chi-squared = 8.06, P = 0.011). The phylogenetic analysis showed that all gastric cancer strains with East Asian-type CagA were in the East Asian cluster, and that most duodenal ulcer strains were in the Western cluster. CONCLUSIONS: The origins of H. pylori isolates are different between gastric cancer strains and duodenal ulcer strains, and East Asian CagA-positive H. pylori infection is associated with gastric cancer. The strain diversity observed in Okinawa may affect the difference in the prevalence of disease associated with H. pylori infection in Japan.

Distinct diversity of vacA, cagA, and cagE genes of Helicobacter pylori associated with peptic ulcer in Japan.

Colonization of the stomach mucosa by Helicobacter pylori is a major cause of acute and chronic gastric pathologies in humans. Several H. pylori virulence genes that may play a role in its pathogenicity have been identified. The most important determinants are vacA and cagA in the cag pathogenicity island (cagPAI) genes. In the present study, to consider the association of molecular genetics between vacA and the cagPAI regarding clinical outcome, we selected H. pylori strains with various genotypes of vacA in Japan and sequenced full-length vacA, cagA, and cagE genes. Sequencing of vacA and cagA genes revealed variable size, whereas the cagE gene was well conserved among strains. Each of the phylogenetic trees based on the deduced amino acid sequences of VacA, CagA, and CagE indicated that all three proteins were divided into two major groups, a Western group and an East Asian group, and the distributions of isolates exhibited similar patterns among the three proteins. The strains with s2 and s1a/m1a vacA genotypes and the Western-type 3' region cagA genotype were classified into the Western group, and the strains with the s1c/m1b vacA genotype and the East Asian-type 3' cagA genotype were included in the East Asian group. In addition, the prevalence of infection with the Western group strain was significantly higher in patients with peptic ulcer (90.0%, 9/10) than in patients with chronic gastritis (22.7%, 5/22) (chi2 = 12.64, P = 0.00057). These data suggest that the molecular genetics of vacA and cagPAI are associated and that the Western group with vacA and cagPAI genes is associated with peptic ulcer disease.

Identification of Helicobacter pylori and the cagA genotype in gastric biopsies using highly sensitive real-time PCR as a new diagnostic tool.

The CagA protein is one of the virulence factors of Helicobacter pylori, and two major subtypes of CagA have been observed, the Western and East Asian type. CagA is injected from the bacteria into gastric epithelial cells, undergoes tyrosine phosphorylation, and binds to Src homology 2 domain-containing protein-tyrosine phosphatase SHP-2. The East Asian type CagA binds to SHP-2 more strongly than the Western type CagA. Here, we tried to distinguish the CagA type by highly sensitive real-time PCR with the objective of establishing a system to detect H. pylori and CagA subtypes from gastric biopsies. We designed primers and probe sets for Western or East Asian-cagA at Western-specific or East Asian-specific sequence regions, respectively, and H. pylori 16S rRNA. We could detect the H. pylori 16S rRNA gene, Western and East Asian-cagA gene from DNA of gastric biopsies. The sensitivity and specificity for H. pylori infection was 100% in this system. In Thai patients, 87.8% (36/41) were cagA-positive; 26.8% (11/41) were Western-cagA positive and 53.7% (22/41) were East Asian-cagA positive, while 7.3% (3/41) reacted with both types of cagA. These results suggest that this real-time PCR system provides a highly sensitive assessment of CagA type as a new diagnostic tool for the pathogenicity of H. pylori infection.

Distinct diversity of the cag pathogenicity island among Helicobacter pylori strains in Japan.

The severity of Helicobacter pylori-related disease is correlated with the presence of a cag pathogenicity island (PAI). Genetic diversity within the cag PAI may have a modifying effect on the pathogenic potential of the infecting strain. We analyzed the complete cag PAI sequences of 11 representative Japanese strains according to their vacA genotypes and clinical effects and examined the relationship between the diversity of the cag PAI and clinical features. The cag PAI genes were divided into two major groups, a Western and a Japanese group, by phylogenetic analysis based on the entire cag PAI sequences. The predominant Japanese strains formed a Japanese cluster which was different from the cluster formed by Western strains. The diversity of the cag PAI was associated with the vacA and cagA genotypes. All strains with the s1c vacA genotype were in the Japanese cluster. In addition, all strains with the East Asian-type cagA genotype were also in the Japanese cluster. Patients infected with the Japanese-cluster strain had high-grade gastric mucosal atrophy. These results suggest that a distinct diversity of the cag PAI of H. pylori is present among Japanese strains and that this diversity may be involved in the development of atrophic gastritis and may increase the risk for gastric cancer.

Association between diversity in the Src homology 2 domain--containing tyrosine phosphatase binding site of Helicobacter pylori CagA protein and gastric atrophy and cancer.

We investigated the relationship between the diversity of Helicobacter pylori CagA protein and clinical outcome. The cagA gene was sequenced in 115 clinical isolates. The binding affinity of CagA to Src homology 2 domain-containing tyrosine phosphatase (SHP-2) was examined by in vitro infection. Two major CagA subtypes were observed--the East Asian and the Western type. The grades of inflammation, activity of gastritis, and atrophy were significantly higher in patients with gastritis infected with the East Asian CagA-positive strain than in patients with gastritis infected with cagA-negative or Western CagA-positive strains. All strains isolated from patients with gastric cancer were East Asian CagA positive. East Asian CagA exhibited stronger SHP-2-binding activity than did Western CagA. These findings suggest that infection with East Asian CagA-positive H. pylori is associated with atrophic gastritis and gastric cancer and that persistent active inflammation induced by the East Asian CagA-positive strain may play a role in the pathogenesis of disease.

The diversity of vacA and cagA genes of Helicobacter pylori in East Asia.

It has been reported that Helicobacter pylori infection with the type I strain, which expresses the VacA and CagA antigens, is associated with duodenal ulcer. We examined the diversity of vacA and cagA genes in 143 isolates obtained from patients with duodenal ulcer or chronic gastritis in East Asia (two different areas of Japan, Fukui and Okinawa, and also in Hangzhou, China) by polymerase chain reaction (PCR) and sequence analysis. Diversities of cagA and vacA genes were detected in East Asia. The prevalence of cagA-positive H. pylori was significantly different between Fukui and Okinawa (P=0.0032). The prevalence of Western type CagA was significantly higher in Okinawa than in Fukui (P<0.0001). However, there was no significant association between the genotype of cagA and clinical outcome. In Japan, the predominant vacA genotype was s1c/m1b. In contrast, in Hangzhou, the predominant vacA genotype was s1c/m2, and they were all East Asian CagA-positive. These findings suggest that a distinct distribution of the vacA and cagA genotypes is present in East Asia, regardless of clinical outcome.

The CagA protein of Helicobacter pylori is translocated into epithelial cells and binds to SHP-2 in human gastric mucosa.

Recent experiments have indicated that CagA of Helicobacter pylori is injected into epithelial cells via the type IV secretion system and undergoes tyrosine phosphorylation in cells and that translocated CagA binds the SRC homology 2 domain-containing tyrosine phosphatase (SHP-2). We investigated these phenomena in in vivo human gastric mucosa. Tyrosine-phosphorylated CagA and CagA-coimmunoprecipitated SHP-2 were detected in gastric mucosa from H. pylori-positive patients with atrophic gastritis and in noncancerous tissues from H. pylori-positive patients with early gastric cancer. In contrast, CagA was not detected in gastric mucosa with either intestinal metaplasia or cancer. Our results provide the first evidence that CagA is translocated into the gastric epithelial cells, receives tyrosine phosphorylation, and binds SHP-2 in in vivo human gastric mucosa. Deregulation of SHP-2 by CagA may play a role in the acquisition of a cellular-transformed phenotype at a relatively early stage of multistep gastric carcinogenesis.

Correlation between variation of the 3' region of the cagA gene in Helicobacter pylori and disease outcome in Japan.

Genetic diversity within the cag pathogenicity island (PAI) of Helicobacter pylori may have a modifying effect on the pathogenic potential of the infecting strain. The genetic structure of the cag PAI was examined in Japanese isolates. The composition and nucleotide sequences of the cag PAI were quite similar among strains; however, diversity between 2 cag genes (virB10 and cagA) was observed. The variety in the number of repetition of the 5-amino acid sequence R1 (EPIYA) in the 3' region of the cagA gene was identified. The frequencies of the genotypes that contained >4 R1 sequences were significantly higher in atrophic gastritis-causing strains than in duodenal ulcer-causing strains. One-third of strains with >4 R1 sequences were gastric cancer-causing strains. Although the cag PAI is conserved in H. pylori isolates in Japan, H. pylori infection with the cagA genotype with >4 R1 sequences may correlate with the pathogenesis of atrophic gastritis and gastric cancer.