Prevalence, Heterogeneity Of CagA/CagA Of Helicobacterpylori And Relationship To Gastroduodenal Diseases In China

Numerous previous studies in Western countries have highlighted some Helicobacter pylon (H pylon) strains are more pathogenic than others, and that CagA-positive If pylon strains are associated with severe gastroduodenal diseases. However, this is not the case in Asian countries where there are high prevalence of cagA-positive strains infection. Those studies conducted in China had revealed conflicting results.The paradox that CagA-positive H. pylon infection correlates to two mutually exclusive diseases: gastric cancer and duodenal ulcer, and results in various clinical outcomes in different populations, may be due to the heterogeneity of cagA/CagA, which had been suggested by studies conducted in Japan, Germany and South Africa. Discriminatory techniques detecting cagA or CagA employed in different studies may be another contributory factor. Recent data have suggested that the tyrosine phosphorylation of CagA may also play a role.cagA/CagA is highly divergent, either at gene level or protein level, which is most marked in the 3?region where there are variable number of repeat sequences. Previous studies showed that CagA protein in larger size and with stronger antigen are more likely to correlate to gastric adenocarcinoma.Therefore, we made an attempt to examine the heterogeneity of cagA/CagA of Chinese H. pylon isolates, and determine whether there are distinct cagA/CagA types circulating in different areas in China, so as to character gastroduodenal diseases-specific cagAlCagA types.The prevalence of cagAlCagA of Chinese H. pylon strains was firstdetermined by detecting the cagA gene using polymerase chain reaction andCagA protein using SDS-PAGE simu1taneously, Which revealed very high. Sothe anigenic heterogeneity of CagA of 38 strains was then deterrnined byaligning and comparing their reactivity to thIee different rabbit sera immunizedby H Pylori strains CAPM N62, NCTCl1637 and CAPM Z-2 respectivelyusing western blots. To examine whether distinct cagA alleles may circulate indifferent areas and correlate to different clinical outcomes, the variablesegment of 3' region of cagA gene of different clinical origin were amplifiedby PCR, and the length of PCR products were compared. In order to fullyunderstand the relationship between heterogeneity of CagA and clinicalpresents, the full-length cagA genes of two gastric cancer-associated and oneduodena1 ulcer-associated H PylOri strains and strain SSl were cloned andsequenced, and the homology of their nucleotide and deduced amino acidsequences as wel1 as phosphorylation motifS preseni in CagA were analyzed.Considering it is difficult to get 1ots of CagA from H Pylori culture for studiesof the function and pathogenesis of CagA, cagA of these fOur strains werecloned inio PinPointTM Xa-l T-vector to constructed recombinant plasmidsexpressing CagA fused to PinPointTM biotinylation segment.Our resu1ts showed: (l) There is a high prevalence of cagAjCagA ofChinese H Pylori isolates irrelevant geograPhic or clinical origin, Which agreeswell with those of other Asian couniTies, and suggests that cagA/CagA is notthe virulent mark of H Pylori strains in China. (2) None of the threeimmunized sera cou1d recognize CagA of all isolates, howeveT, each CagAcould be recognized by at least one serum. The antigenic heterogeneity ofCagA was grouPed as I -V, group II which reacted most strong1y withserum immunized by NCTC11637 was more likely but not significantlycorrelated to peptic ulcer' (3) cagA genes were designed to three types I, II,and III according to the amplified PCR product length of variable segment of3' region, of which was about 825bp, 900bp or 950bp respectively. Type IcagA gene predominates in China, both the rare two tyPes II and Ill cagAgene present in only two iso1ates respectively. (4) The complete sequences ofIVcagA genes of strain SS1, CAPM N62, CAPM N93 and CAPM Nih have been deposited in GenBank under accession number AF247651, AF249275, AF36...