Anne Mueller

Persistent bacterial infections: the interface of the pathogen and the host immune system

Persistent bacterial infections involving Mycobacterium tuberculosis, Salmonella enterica serovar Typhi (S. typhi) and Helicobacter pylori pose significant public-health problems. Multidrug-resistant strains of M. tuberculosis and S. typhi are on the increase, and M. tuberculosis and S. typhi infections are often associated with HIV infection. This review discusses the strategies used by these bacteria during persistent infections that allow them to colonize specific sites in the host and evade immune surveillance. The nature of the host immune response to this type of infection and the balance between clearance of the pathogen and avoidance of damage to host tissues are also discussed.

Distinct gene expression profiles characterize the histopathological stages of disease in Helicobacter-induced mucosa-associated lymphoid tissue lymphoma.

Long-term colonization of humans with Helicobacter pylori can cause the development of gastric B cell mucosa-associated lymphoid tissue lymphoma, yet little is known about the sequence of molecular steps that accompany disease progression. We used microarray analysis and laser microdissection to identify gene expression profiles characteristic and predictive of the various histopathological stages in a mouse model of the disease. The initial step in lymphoma development is marked by infiltration of reactive lymphocytes into the stomach and the launching of a mucosal immune response. Our analysis uncovered molecular markers of both of these processes, including genes coding for the immunoglobulins and the small proline-rich protein Sprr 2A. The subsequent step is characterized histologically by the antigen-driven proliferation and aggregation of B cells and the gradual appearance of lymphoepithelial lesions. In tissues of this stage, we observed increased expression of genes previously associated with malignancy, including the laminin receptor-1 and the multidrug-resistance channel MDR-1. Finally, we found that the transition to destructive lymphoepithelial lesions and malignant lymphoma is marked by an increase in transcription of a single gene encoding calgranulin A/Mrp-8.

Phosphorylation-Independent Effects of CagA during Interaction between Helicobacter pylori and T84 Polarized Monolayers

To extend our knowledge of host-cell targets of Helicobacter pylori, we characterized the interaction between H. pylori and human T84 epithelial cell polarized monolayers. Transcriptional analysis by use of human microarrays and a panel of isogenic H. pylori mutants revealed distinct responses to infection. Of the 670 genes whose expression changed, most (92%) required the cag pathogenicity island (PAI). Although altered expression of many genes was dependent on CagA (80% of the PAI-dependent genes), expression of >30% of these host genes occurred independent of the phosphorylation state of the CagA protein. Similarly, we found that injected CagA localized to the apical surface of cells and showed preferential accumulation at the apical junctions in a phosphorylation-independent manner. These data suggest the presence of distinct functional domains within the CagA protein that play essential roles in protein targeting and alteration of host-cell signaling pathways.

Protective immunity against Helicobacter is characterized by a unique transcriptional signature

Immunization with a whole-cell sonicate vaccine of Helicobacter felis in conjunction with cholera toxin as a mucosal adjuvant induces long-term protective immunity in a majority of laboratory mice. We have combined gene expression profiling and immunohistochemical analysis on a set of immunized animals to better understand the mechanism of protection. The stomachs of protected animals exhibited a strikingly different transcriptional profile compared with those of nonprotected or control mice, indicating that vaccination targets the appropriate site and leaves a molecular signature. Among the genes whose up-regulation is significantly correlated with protection are a number of adipocyte-specific factors. These include the fat-cell-specific cytokines adipsin, resistin, and adiponectin and the adipocyte surface marker CD36. Interestingly, potentially protective T and B lymphocytes can be found embedded in the adipose tissue surrounding protected stomachs but never in control or unprotected stomachs. Adipsin-specific immunohistochemical staining of protected stomach sections further revealed molecular cross-talk between adjacent lymphoid and adipose cell populations. We propose a mechanism of protection that involves the effector responses of either or both lymphocyte subclasses as well as the previously unappreciated paracrine functions of adipose tissue surrounding the resident lymphocytes.

Prostaglandin E2 Prevents Helicobacter-Induced Gastric Preneoplasia and Facilitates Persistent Infection in a Mouse Model

BACKGROUND & AIMS Persistent infection with the human pathogen Helicobacter pylori increases the risk of gastric cancer. In this study, we investigated the role of cyclooxygenase-2 (COX-2) and its main product, prostaglandin E(2) (PGE(2)), in the development of Helicobacter-induced gastritis and gastric cancer precursor lesions. METHODS We utilized mouse models of Helicobacter-induced gastric preneoplasia and vaccine-induced protection to study the effects of COX-2 inhibition and PGE(2) treatment on the induction of Helicobacter-specific immune responses and gastric premalignant immunopathology. RESULTS COX-2 and PGE(2) are up-regulated upon Helicobacter infection in cultured epithelial cells and in the gastric mucosa of infected mice. Inhibition of COX-2 activity with celecoxib significantly accelerated early preneoplasia; conversely, systemic administration of synthetic PGE(2) prevented development of premalignant pathology and completely reversed preexisting lesions by suppressing interferon-gamma production in the infected stomachs. The protective effect of PGE(2) was accompanied by increased Helicobacter colonization in all models. All in vivo effects were attributed to immunosuppressive effects of PGE(2) on CD4(+) T-helper 1 cells, which fail to migrate, proliferate, and secrete cytokines when exposed to PGE(2) in vitro and in vivo. T-cell inhibition was found to be due to silencing of interleukin-2 gene transcription, and could be overcome by supplementation with recombinant interleukin-2 in vitro and in vivo. CONCLUSIONS COX-2-dependent production of PGE(2) has an important immunomodulatory role during Helicobacter infection, preventing excessive local immune responses and the associated immunopathology by inhibiting the effector functions of pathogenic T-helper 1 cells.

Skin and soft tissue infections in intercontinental travellers and the import of multi-resistant Staphylococcus aureus to Europe

Staphylococcus aureus is emerging globally. Treatment of infections is complicated by increasing antibiotic resistance. We collected clinical data and swabs of returnees with skin and soft tissue infections (SSTI) at 13 travel-clinics in Europe (www.staphtrav.eu). Sixty-two percent (196/318) SSTI patients had S. aureus-positive lesions, of which almost two-thirds (122/196) were Panton-Valentine leukocidin (PVL) positive. PVL was associated with disease severity, including hospitalization for SSTI (OR 5.2, 95% CI 1.5-18.2). In returnees with SSTI, longer travel and more intense population contact were risk factors for nasal colonization with PVL-positive S. aureus. Imported S. aureus frequently proved resistant to trimethoprim-sulfamethoxazole (21%), erythromycin (21%), tetracycline (20%), ciprofloxacin (13%), methicillin (12%) and clindamycin (8%). Place of exposure was significantly (p < 0.05) associated with predominant resistance phenotypes and spa genotypes: Latin America (methicillin; t008/CC24/304), Africa (tetracycline, trimethoprim-sulfamethoxazole; t084/CC84, t314/singleton, t355/CC355), South Asia (trimethoprim-sulfamethoxazole, ciprofloxacin; t021/CC21/318), South-East Asia (clindamycin; t159/CC272). USA300-like isolates accounted for 30% of all methicillin-resistant S. aureus imported to Europe and were predominantly (71%) acquired in Latin America. Multi-resistance to non-β-lactams were present in 24% of imports and associated with travel to South Asia (ORcrude 5.3, 95% CI 2.4-11.8), even after adjusting for confounding by genotype (ORadjusted 3.8, 95% 1.5-9.5). Choosing randomly from compounds recommended for the empiric treatment of severe S. aureus SSTI, 15% of cases would have received ineffective antimicrobial therapy. These findings call for the development of regionally stratified guidance on the antibiotic management of severe imported S. aureus disease and put the infected and colonized traveller at the centre of interventions against the global spread of multi-resistant S. aureus.

Helicobacter pylori and Gastric Cancer: What can be Learned by Studying the Response of Gastric Epithelial Cells to the Infection?

The development of gastric adenocarcinoma is closely linked to chronic infection with the bacterial pathogen Helicobacter pylori. One Helicobacter-specific virulence factor in particular, the CagA protein, has emerged as a main effector molecule in the interaction of H. pylori with gastric epithelial cells and has been implicated in gastric carcinogenesis. This review highlights the latest insights that have been gained into the pathogenesis of the disease by transcriptional profiling approaches studying gene expression in normal gastric tissue and gastric cancer tissue from human biopsy material as well as animal models of Helicobacter infection. The potential role of CagA as a bacterial oncoprotein is also discussed.

Feasibility and safety of conservative surgery for the treatment of spermatic cord leiomyosarcoma

OBJECTIVES To assess the feasibility and the safety of conservative surgery to treat spermatic cord leiomyosarcoma. METHODS Patients undergoing inguinoscrotal exploration in 10 different Urological Centers with diagnosis of leiomyosarcoma were enrolled. Preoperative evaluation included physical examination, Scrotal US, Abdominal CT and Scrotal MRI in selected cases. Patients underwent organ sparing surgery or orchiectomy in case of intraoperative FSE was positive for a local infiltration. Data collected were: age, presence of infiltration, length of the lesion, number of lesions, definitive histological outcome, pre and postoperative testosterone level. Follow up was performed with abdomen CT scan and scrotal US. RESULTS From January 2007 to December 2013, 23 patients (mean age: 64.7 yrs) were diagnosed with spermatic cord leiomyosarcoma. Each patients underwent scrotal US. 10 patients underwent radical orchiectomy and 13 patients underwent conservative surgery. Mean follow up was 36.5 months. 5 patients (21.7%) developed a recurrent disease, 18 patients (78.3%) had a negative follow up (mean time: 40.8 months). Statistical analysis reveals that there is a significant correlation between number of lesions, length of the lesions and recurrent disease. CONCLUSIONS Spermatic cord leiomyosarcoma is a rare disease. Conservative surgical treatment of spermatic cord leiomyosarcoma is a feasible therapeutic option for small, single and not infiltrating lesion.