Functional plasticity in the type IV secretion system of Helicobacter pylori.

Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection

EPIDEMIOLOGY OF PARACOCCIDIOIDOMYCOSIS

SUMMARYThe epidemiological characteristics of paracoccidioidomycosis were reviewed and updated. The new endemic areas in Brazil were discussed in the section regarding the geographic distribution of the mycosis. Subclinical infection with Paracoccidioides brasiliensis was discussed on the basis of skin test surveys with antigens of the fungus, seroepidemiological studies, and disease cases outside Latin America. Large case series permitted a comparison of the prevalence of the mycosis in different regions, its estimated incidence and risk factors for the development of the disease. Aspects modulating the expression of the clinical forms of paracoccidioidomycosis are also presented. This review also deals with diseases associated with the mycosis, opportunistic paracoccidioidomycosis, lethality, mortality and infection and disease in animals

Maintenance of Type IV Secretion Function During Helicobacter pylori Infection in Mice.

The Helicobacter pylori type IV secretion system (T4SS) encoded on the cag pathogenicity island (cagPAI) secretes the CagA oncoprotein and other effectors into the gastric epithelium. During murine infection, T4SS function is lost in an immune-dependent manner, typically as a result of in-frame recombination in the middle repeat region of cagY, though single nucleotide polymorphisms (SNPs) in cagY or in other essential genes may also occur. Loss of T4SS function also occurs in gerbils, nonhuman primates, and humans, suggesting that it is biologically relevant and not simply an artifact of the murine model. Here, we sought to identify physiologically relevant conditions under which T4SS function is maintained in the murine model. We found that loss of H. pylori T4SS function in mice was blunted by systemic Salmonella coinfection and completely eliminated by dietary iron restriction. Both have epidemiologic parallels in humans, since H. pylori strains from individuals in developing countries, where iron deficiency and systemic infections are common, are also more often cagPAI+ than strains from developed countries. These results have implications for our fundamental understanding of the cagPAI and also provide experimental tools that permit the study of T4SS function in the murine model.IMPORTANCE The type IV secretion system (T4SS) is the major Helicobacter pylori virulence factor, though its function is lost during murine infection. Loss of function also occurs in gerbils and in humans, suggesting that it is biologically relevant, but the conditions under which T4SS regulation occurs are unknown. Here, we found that systemic coinfection with Salmonella and iron deprivation each promote retention of T4SS function. These results improve our understanding of the cag pathogenicity island (cagPAI) and provide experimental tools that permit the study of T4SS function in the murine model

Functional plasticity in the type IV secretion system of Helicobacter pylori.

Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection

Functional plasticity in the type IV secretion system of Helicobacter pylori.

Helicobacter pylori causes clinical disease primarily in those individuals infected with a strain that carries the cytotoxin associated gene pathogenicity island (cagPAI). The cagPAI encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into epithelial cells and is required for induction of the pro-inflammatory cytokine, interleukin-8 (IL-8). CagY is an essential component of the H. pylori T4SS that has an unusual sequence structure, in which an extraordinary number of direct DNA repeats is predicted to cause rearrangements that invariably yield in-frame insertions or deletions. Here we demonstrate in murine and non-human primate models that immune-driven host selection of rearrangements in CagY is sufficient to cause gain or loss of function in the H. pylori T4SS. We propose that CagY functions as a sort of molecular switch or perhaps a rheostat that alters the function of the T4SS and "tunes" the host inflammatory response so as to maximize persistent infection

CagY Is an Immune-Sensitive Regulator of the Helicobacter pylori Type IV Secretion System.

Background & aimsPeptic ulcer disease and gastric cancer are caused most often by Helicobacter pylori strains that harbor the cag pathogenicity island, which encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into host cells. cagY is an essential gene in the T4SS and has an unusual DNA repeat structure that predicts in-frame insertions and deletions. These cagY recombination events typically lead to a reduction in T4SS function in mouse and primate models. We examined the role of the immune response in cagY-dependent modulation of T4SS function.MethodsH pylori T4SS function was assessed by measuring CagA translocation and the capacity to induce interleukin (IL)8 in gastric epithelial cells. cagY recombination was determined by changes in polymerase chain reaction restriction fragment-length polymorphisms. T4SS function and cagY in H pylori from C57BL/6 mice were compared with strains recovered from Rag1-/- mice, T- and B-cell-deficient mice, mice with deletion of the interferon gamma receptor (IFNGR) or IL10, and Rag1-/- mice that received adoptive transfer of control or Ifng-/- CD4+ T cells. To assess relevance to human beings, T4SS function and cagY recombination were assessed in strains obtained sequentially from a patient after 7.4 years of infection.ResultsH pylori infection of T-cell-deficient and Ifngr1-/- mice, and transfer of CD4+ T cells to Rag1-/- mice, showed that cagY-mediated loss of T4SS function requires a T-helper 1-mediated immune response. Loss of T4SS function and cagY recombination were more pronounced in Il10-/- mice, and in control mice infected with H pylori that expressed a more inflammatory form of cagY. Complementation analysis of H pylori strains isolated from a patient over time showed changes in T4SS function that were dependent on recombination in cagY.ConclusionsAnalysis of H pylori strains from mice and from a chronically infected patient showed that CagY functions as an immune-sensitive regulator of T4SS function. We propose that this is a bacterial adaptation to maximize persistent infection and transmission to a new host under conditions of a robust inflammatory response

CagY Is an Immune-Sensitive Regulator of the Helicobacter pylori Type IV Secretion System

BACKGROUND & AIMS: Peptic ulcer disease and gastric cancer are most often caused by Helicobacter pylori strains that harbor the cag pathogenicity island (cagPAI), which encodes a type IV secretion system (T4SS) that injects the CagA oncoprotein into host cells. cagY is an essential gene in the T4SS and has an unusual DNA repeat structure that predicts in-frame insertions and deletions. These cagY recombination events typically lead to a reduction in T4SS function in mouse and primate models. We examined the role of the immune response in cagY-dependent modulation of T4SS function. METHODS: H pylori T4SS function was assessed by measuring CagA translocation and the capacity to induce interleukin-8 (IL8) in gastric epithelial cells. cagY recombination was determined by changes in PCR restriction fragment-length polymorphisms. T4SS function and cagY in H pylori from C57BL/6 mice were compared to strains recovered from Rag1−/− mice, T and B cell deficient mice, mice with deletion of IFNGR or IL10, and Rag1−/− mice that received adoptive transfer of control or Ifng−/− CD4+ T cells. To assess relevance to humans, T4SS function and cagY recombination were assessed in strains obtained sequentially from a patient after 7.4 years of infection. RESULTS: H pylori infection of T-cell deficient and Ifngr1−/− mice, and transfer of CD4+ T cells to Rag1−/− mice, demonstrated that cagY-mediated loss of T4SS function requires a T-helper 1-mediated immune response. Loss of T4SS function and cagY recombination were more pronounced in Il10−/− mice, and in control mice infected with H pylori that expressed a more inflammatory form of cagY. Complementation analysis of H pylori strains isolated from a patient over time demonstrated changes in T4SS function that were dependent on recombination in cagY. CONCLUSIONS: Analysis of H pylori strains from mice and from a chronically infected patient showed that CagY functions as an immune-sensitive regulator of T4SS function. We propose that this is a bacterial adaptation to maximize persistent infection and transmission to a new host under conditions of a robust inflammatory response

Recombination in <i>cagY</i> during infection of rhesus monkeys is sufficient to reduce the capacity of <i>H. pylori</i> to induce IL-8 and translocate CagA.

<p>Deletion of <i>cagY</i> (▵Y) from WT <i>H. pylori</i> J166 significantly reduced its capacity to induce IL-8 (mean ± SEM of 3 replicates), which was recovered when the chromosomal WT <i>cagY</i> allele was restored (▵Y [J166]) by complementation (black bars). Immunoblot showed that only the WT or ▵Y [J166] expressed CagY protein (α-CagY) and translocated CagA that was tyrosine phosphorylated (α-PY99). Two rhesus output strains with unique <i>cagY</i> alleles (rOut1, rOut2) lost the capacity to induce IL-8 (gray bars) and translocate CagA, although they expressed CagY. Replacement of ▵<i>cagY</i> with <i>cagY</i> from rOut1 (▵Y [rOut1]) or rOut2 (▵Y [rOut2]) recapitulated their failure to induce IL-8 induction (white bars) and translocate phosphorylated CagA. Similarly, complementation with <i>cagY</i> from an output strain (rOut3) that expressed a unique <i>cagY</i> but maintained the capacity to induce IL-8 (gray bar) and translocate CagA, also phenocopied its IL-8 induction and translocation of CagA. All strains expressed CagA (α-CagA), though only those that induced IL-8 had the capacity to translocate CagA that was tyrosine phosphorylated. Multiple bands in the CagY immunoblot could represent different transcription or translation products, or even protein fragments, but they are CagY-specific since they are absent in the <i>cagY</i> deletion mutant. **<i>P</i><0.01; ***<i>P</i><0.001.</p