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Helicobacter Pylori in RF

#2752


Helicobacter Pylori Genetic Diversity and Genome Evolution in Countries of the Russian Federation

Tech Area / Field

  • MED-DIS/Disease Surveillance/Medicine
  • BIO-MIB/Microbiology/Biotechnology
  • BIO-CGM/Cytology, Genetics and Molecular Biology/Biotechnology

Status
3 Approved without Funding

Registration date
09.04.2003

Leading Institute
State Research Center for Applied Microbiology, Russia, Moscow reg., Obolensk

Project summary

Helicobacter pylori (Hp) is a main cause of the stomach and duodenum-associated diseases. Its current contribution to pathology of these diseases is beyond of doubt. Hp infection in people develops often acute asymptomic gastritis, and in 60-95% of cases, atrophic gastritis is accompanied by developing peptic ulcer disease. The involvement of Hp in generating ulcer disease is confirmed by the fact that ulcer cicatrizes after therapeutic eradication of the pathogen. H. pylori-associated chronic gastritis may an early risk factor for gastric cancer.

Hp chronically infects more than half of all people worldwide, with infections often lasting for years or decades, and is an important cause of peptic ulcer disease an early risk factor for gastric cancer. It is one of the most genetically perse of bacterial pathogens. Emerging evidence suggests different Hp genotypes predominate in different human populations, although this has been based on only a relatively few strain collections (none involving isolates from the immense Russian Federation), and that some of Hp's genetic persity affects the specificity of human colonization, persistence of infection once established, and the nature or severity of disease.

The research collaboration proposed here is based on the expertise of the SRCAM group in microbiologic and genotyping analyses of perse bacterial pathogens including microaerobes such as Hp, and their special access to Hp strains from many different parts of Russia, and the strong program of the American collaborator, Dr. Douglas Berg, in areas of Hp population genetics and evolution and bacterial-host interactions, and his considerable experience in productive collaborations with researchers from Russia and other countries of the Former Soviet Union. Our aims are based strongly on his published and preliminary findings, which will be reviewed in detail in following sections.

The proposed experiments will (i) contribute importantly to the global understanding of Hp biology and disease, (ii) examine Hp in the context of the great ethnic and life style persity of the peoples of the Russian federation, and (iii) contribute to the further development of modern molecular genetics for human advancement of a dedicated and motivated team of researchers at a former bioweapons research unit, and their integration into the world scientific community. Our three main Specific Aims are as follows.

AIM 1. To better understand population genetic structure and genome evolution in Hp in perse peoples of Russia. We will culture and carry out DNA sequence based analyses of Hp from ethnic Russians, and from ethnic minorities living in their own relatively isolated communities, and also in cosmopolitan centers such as Moscow. This is based on Berg's findings (i) that predominant genotypes of strains from East Asia are easily distinguished from those Europe; (ii) of significant differences in the distributions of genotypes even within Asia (Japan vs. Korea vs. coastal China vs. India) or within Europe (Spain vs. Lithuania); (iii) that strains of Alaska Natives are extremely heterogeneous, include genotypes that seem East Asian-like, but are distinct from any seen to date in Japanese, Korean or Coastal Chinese strains. These findings are intriguing evolutionarily, may give clues to the origins of Hp as a human pathogen, and may also be important medically, because patterns of Hp-associated disease differ markedly among peoples or geographic regions. The peoples of the Russian Federation are distinct from any other peoples whose strains have been studied to date, and it is our working hypothesis that their strains are similarly distinct.

AIM 2. To better understand mechanism and control of susceptibility of Hp to the anti-Hp drug Mtz, and the functional importance of this in the context of ethnicity, geography and human disease. We will study patterns of resistance and susceptibility to Mtz in strains from various Russian peoples, using simple reverse genetic and phenotype analyses, and examine effects of susceptibility or resistance on bacterial fitness. These experiments will provide a means of examining the hypothesis that "quantitative trait loci" (here involving metabolic functions) can be important in terms of colonization or disease. This plan is based on Berg's findings that (i) Mtz susceptibility results from expression of the rdxA and frxA genes, which encode distinct nitroreductases that each convert Mtz from harmless prodrug to bactericidal hydroxylamine-type agents; (ii) that frxA is relatively quiescent in most MtzS strains (designated type I), but expressed in others (type II); (iii) that the frequency of type I vs II strains differs regionally; (iv) that the two mouse colonizing strains studied to date (SS1 and X47) are each type II; rdxA is essential for, and frxA contributes quantitatively to the vigor of, colonization; (v) rdxA inactivation in these two strains causes loss motility (a trait considered important for infection), whereas frxA inactivation does not; and (vi) rdxA inactivation in half of the other 20 MtzS strains studied does not result in loss of motility, and suppressor mutations that restore motility to SS1 can be isolated in culture.

AIM 3. To further examine the functional persity among Hp strains, using a simple rodent model. This will entail selecting those Hp isolates from perse Russian peoples that can infect mice, selecting better adapted variants by sequential animal passage, examining patterns of colonization in different regions of the gastric mucosa, and phenotype, PCR and sequence-based analyses of the genotypes of these special strains. This plan is based (A) on the rarity of Hp strains that persistently colonize mice, and the focus of most researchers on just one strain, SS1 (the "Sydney Strain" of Adrian Lee), which is unlikely to adequately represent Hp populations worldwide, and (B) Berg's finding of (i) four new Hp strains that colonize mice, among 50 Hp strains, in pools of ten strains per set of experimentally inoculated mice; (ii) each of these four strains is also type II as defined by Mtz susceptibility (Aim 2, above; frxA highly expressed); (iii) strains SS1 (cag+ vacAs2) and X47 (cag+ vacAs1) tend to occupy different regions of the mouse stomach (antrum and corpus, respectively), and to form persistent mixed infections after co-inoculation, which implies that there are at least two gastric "niches" potentially available to Hp.

Data from gene typing of Hp is very important for practical medicine, especially from the standpoint of diagnostics and developing measures to control and treat Hp infections. Not less important are data from gene typing of Hp, for basic studies. For example, they allow us to understand better mechanisms underlying evolution of the pathogen, to monitor its spread among countries and ethnic communities worldwide, to find explanation for emerging recombinant genotypes and their role in pathology of disease in different human groups.

All tasks under this project proposal will be solved in conjunction with Dr. Berg, project collaborator, and his colleagues. Our research will be based on great experience of our American colleagues, so we plan to send our specialists to Dr.Berg’s laboratory for training. It is also planned to transfer some Russian strains of Hp to Dr. Berg’s laboratory.


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