A prospective pilot study of the T-lymphocyte response to fine particulate matter exposure.

Exposure to air pollution is associated with increased morbidity and mortality. Once the fine atmospheric particulate matter (FP) is inhaled, some of its compounds can pass through the lungs and reach the bloodstream where they can come into contact with immune cells. Exposure to FP particularly affects sensitive populations such as the elderly. Aging affects the immune system, making the elderly more vulnerable. The project aims to determine the effects of FP exposure on human T cells while looking for biomarkers associated with exposure. Blood samples from 95 healthy subjects in three different age groups (20-30, 45-55 and 70-85 years) were collected to determine a potential age effect. T lymphocytes were isolated to be exposed ex vivo for 72 hours to 45 µg/mL of FP collected in Dunkirk and chemically characterized. Overexpression of the CYP1A1, CYP1B1 and CYP2S1 genes was therefore measured after exposure of the T cells to FP. These genes code for enzymes known to be involved in the metabolic activation of organic compounds such as polycyclic aromatic hydrocarbons detected in the FP sample. T-cell profiling allowed us to suggest a mixed T-helper 1/2 profile caused by exposure to FP. With regard to the influence of age, we have observed differences in the expression of certain genes, as well as an increase in interleukin-4 and -13 concentrations in the elderly. These results showed that exposure of T lymphocytes to FP causes effects on both transcriptomic and cytokine secretion levels.

Cordylobia anthropophaga (Diptera: Calliphoridae) outside Africa: a case of furuncular myiasis in a child returning from Congo.

International travel to tropical countries accounts for an increasing incidence of imported diseases. An unusual case of furuncular myiasis due to Cordylobia anthropophaga (Blanchard) is reported in northern France in a 9-mo-old infant, after a 4-mo stay in Congo. A review has been made of the major cases of imported furuncular myiasis due to Cordylobia, as well as identification of second larval instars and management of the myiasis.

Cryptosporidium parvum, a potential cause of colic adenocarcinoma.

BACKGROUND: Cryptosporidiosis represents a major public health problem. This infection has been reported worldwide as a frequent cause of diarrhoea. Particularly, it remains a clinically significant opportunistic infection among immunocompromised patients, causing potentially life-threatening diarrhoea in HIV-infected persons. However, the understanding about different aspects of this infection such as invasion, transmission and pathogenesis is problematic. Additionally, it has been difficult to find suitable animal models for propagation of this parasite. Efforts are needed to develop reproducible animal models allowing both the routine passage of different species and approaching unclear aspects of Cryptosporidium infection, especially in the pathophysiology field. RESULTS: We developed a model using adult severe combined immunodeficiency (SCID) mice inoculated with Cryptosporidium parvum or Cryptosporidium muris while treated or not with Dexamethasone (Dex) in order to investigate divergences in prepatent period, oocyst shedding or clinical and histopathological manifestations. C. muris-infected mice showed high levels of oocysts excretion, whatever the chemical immunosuppression status. Pre-patent periods were 11 days and 9.7 days in average in Dex treated and untreated mice, respectively. Parasite infection was restricted to the stomach, and had a clear preferential colonization for fundic area in both groups. Among C. parvum-infected mice, Dex-treated SCID mice became chronic shedders with a prepatent period of 6.2 days in average. C. parvum-inoculated mice treated with Dex developed glandular cystic polyps with areas of intraepithelial neoplasia, and also with the presence of intramucosal adenocarcinoma. CONCLUSION: For the first time C. parvum is associated with the formation of polyps and adenocarcinoma lesions in the gut of Dex-treated SCID mice. Additionally, we have developed a model to compare chronic muris and parvum cryptosporidiosis using SCID mice treated with corticoids. This reproducible model has facilitated the evaluation of clinical signs, oocyst shedding, location of the infection, pathogenicity, and histopathological changes in the gastrointestinal tract, indicating divergent effects of Dex according to Cryptosporidium species causing infection.

Cloning and characterization of WMSU1, a Williopsis saturnus var. mrakii gene encoding a new yeast SUN protein involved in the cell wall structure.

SUN proteins of Saccharomyces cerevisiae have been defined on the basis of high homologies in their C-terminal domain. Recently, two of these four proteins were shown to be involved in cell wall morphogenesis (Mouassite et al., 2000a). In the present study, we have isolated WMSU1 (Accession No. AF418983), a new SUN-related gene, from W. saturnus var. mrakii MUCL 41968. Sequencing of the gene revealed an open reading frame coding for 402 amino acids. The predicted amino acid sequence of WMSU1 is closely related to the S. cerevisiae SUN proteins and to other yeast proteins involved in cell wall metabolism. WMSU1 is proposed to encode a cell wall protein since its predicted product contains a signal sequence, a Kex2p cleavage site and a serine/threonine-rich N-terminal domain. Southern blot analysis of the W. saturnus var. mrakii MUCL 41968 genome using the highly conserved domain of WMSU1 as a probe suggested that the isolated gene belongs to a multigenic family. Expression of WMSU1 in E. coli led to a 45 kDa protein, which appeared to be toxic to this host. Scanning electron microscopy analysis of a recombinant S. cerevisiae producing Wmsu1p showed that this strain exhibited an altered cell wall, thus pointing to a probable role of this protein in the cell wall structure.

Involvement of [beta]-glucans in the wide-spectrum antimicrobial activity of Williopsis saturnus var. mrakii MUCL 41968 killer toxin.

BACKGROUND: Williopsis saturnus var. mrakii MUCL 41968 secretes a 85-kDa glycoprotein killer toxin (WmKT) that displays a cytocidal activity against a wide range of microorganisms, making WmKT a promising candidate for the development of new antimicrobial molecules. Although the killing mechanism of WmKT is still unknown, the toxin was recently proposed to bind to the surface of sensitive microorganisms through the recognition of beta-glucans. Indeed, Saccharomyces cerevisiae strains sensitive to the toxin become resistant when mutated in their beta-glucan synthesis pathway. MATERIALS AND METHODS: To investigate the interaction of WmKT with beta-glucans, we examined in agar diffusion assays the WmKT activity in the presence of enzymes displaying beta-glucanase activity. The toxin activity was also investigated using spheroplasts derived from sensitive yeast cells. The hydrolytic activity of WmKT was studied using specific glucosidase inhibitors as well as various sugar molecules covalently linked to p-nitrophenyl as potential substrates. Finally, the ultrastructural modifications induced by WmKT activity on sensitive yeasts were assessed by scanning electron microscopy. RESULTS: The data reported here support the hypothesis that WmKT binds to sensitive cells using surface-exposed beta-glucans. Indeed beta-glucanase exerts an antagonistic effect on WmKT activity and spheroplasts derived from WmKT-sensitive yeast cells are shown to be resistant to WmKT, suggesting that cell wall beta-glucans are required for WmKT lethal effect. Because WmKT exhibits amino acid sequence similarities with proteins suspected to be glucanase, we also investigated the effect of castanospermine, a potent glucosidase inhibitor, on WmKT activity. Castanospermine completely abolished WmKT killer activity as well as its hydrolytic enzymatic activity against p-nitrophenyl beta-D-glucopyranoside. The scanning electron microscopy analysis of sensitive yeast cells treated with the toxin reveals that WmKT causes cell wall modifications similar to those observed with zymolyase. CONCLUSION: The results reported in this study show that WmKT activity requires an interaction between the mycocin and the cell wall beta-glucans. Moreover, they indicate that WmKT acts on sensitive yeast cells through a hydrolytic activity directed against cell wall beta-glucans that disrupts the yeast cell wall integrity leading to death.

Characterization of a Williopsis saturnus var. mrakii high molecular weight secreted killer toxin with broad-spectrum antimicrobial activity.

Williopsis saturnus var. mrakii MUCL 41968 secretes a killer toxin (WmKT), which is active against a wide range of pathogens. From the W. saturnus var. mrakii MUCL 41968 culture supernatant a protein of 85 kDa with killer activity was purified to homogeneity. The purified protein was demonstrated to be a killer toxin since it displays the toxin activity and cross-reacts with mAbKT4, a monoclonal antibody that blocks WmKT activity. Its partial amino acid sequencing revealed that WmKT might be related to yeast SUN proteins, but not to other killer toxins described. Immunofluorescence studies using polyclonal antibodies raised against purified WmKT revealed that it acts by binding to the cell surface of sensitive strains. We showed that WmKT is inactive against mutant strains of Saccharomyces cerevisiae deficient in the synthesis of beta-glucans, indicating that these polysaccharides constitute the target of the toxin. WmKT was demonstrated to induce rapid lethal cell permeation, since strong propidium iodide labelling was shown for sensitive strains treated with the killer toxin. These findings indicate that WmKT is a novel killer toxin whose molecular characterization may lead to the development of new wide-spectrum antimicrobial compounds.