Secreted subtilisin Sub3 from Microsporum canis is required for adherence to but not for invasion of the epidermis.

BACKGROUND: Microsporum canis is a pathogenic dermatophyte that causes a superficial cutaneous mycosis, mainly in cats and humans. Proteolytic enzymes, including subtilisins, have been postulated to be key factors involved in adherence and invasion of the stratum corneum and keratinized epidermal structures. OBJECTIVES: To evaluate the importance of Sub3 as a M. canis virulence factor using a SUB3 RNA-silenced strain. MATERIALS AND METHODS: The stability of a previously constructed RNA-silenced strain IHEM 22957 was tested in three different ways. The involvement of Sub3 in the adherence process was evaluated using a new ex vivo adherence model of M. canis arthroconidia to feline epidermis. In order to investigate the contribution of Sub3 in epidermal invasion, the pathogenicity of the SUB3 silenced strain was compared with that of the control strain in a guinea pig model of experimental M. canis dermatophytosis. RESULTS: The silenced strain was shown to be stable after four in vitro transfers and after the in vivo experimental infection. This strain has dramatic loss of adherence capacity to feline corneocytes when compared with the parental strain. In contrast, no significant differences were observed at any time during the infection between the control strain and the SUB3 silenced strain, indicating that Sub3 secretion is not required for invasion of epidermal structures. CONCLUSIONS: RNA interference is a useful tool to evaluate pathogenic mechanisms of M. canis. For the first time, a role in pathogenicity could be attributed to a protease of a dermatophyte, namely Sub3 from M. canis, which is required for adherence to but not for invasion of the epidermis.

[Management in pollinosis and false pollinosis]. / Conduite à tenir face aux pollinoses et aux fausses pollinoses.

Typical cases of pollen allergen (hayfever, allergic asthma), together with isolated non-respiratory "equivalent" manifestations (urticaria, eye conditions, headache, etc.), are easy to detect on the basis of skin tests and the clinical history. Such manifestations may also occur in "false pollen allergy", related in most instances by atmospheric moulds (Dematiaceae), sometimes by house dust or dermatophytes (Candida Albicans, Trichophyton sp), by food or by a bacterial infection or allergy. A combination of pollen allergy and false pollen allergy is common. In cases of false pollen allergy the proportion of negative skin reactions would appear to worsen with the repeated use of prolonged action corticosteroid injections, given on a preventive basis. Similarly, these disorders, initially seasonal, change to more chronic manifestations throughout the year. Desensitization with aqueous extracts of allergens ensured the most complete protection against the causes of pollen allergy and false pollen allergy. Allergen extracts percipitated with alun (semi-retard extracts), more effective than tyrosine adsorbates (Pollinex) have the advantage of offering more rapid treatment without the risk of dangerous reactions. The best therapeutic results have obtained over the course of the last ten years, by the authors, combining on each occasion a semi-retard allergen with an aqueous allergen, thereby acquiring the benefit of the adjuvant effect of the first, in a course of ten to fifteen injections per year. Non specific therapy (antihistamines, cromoglycate, theophylline, etc.) retains all of its symptomatic indications. Oral corticosteroid therapy is better metabolized in the organism and has less of a disturbing effect on the circadian rhythm of cortisol, and is hence to be preferred to injections of delyaed action corticosteroid suspensions.

Inhibition of the keratinolytic subtilisin protease Sub3 from Microsporum canis by its propeptide (proSub3) and evaluation of the capacity of proSub3 to inhibit fungal adherence to feline epidermis.

Microsporum canis is a pathogenic fungus that causes a superficial cutaneous infection called dermatophytosis, mainly in cats, dogs and humans. Proteolytic enzymes have been postulated to be key factors involved in the invasion of the stratum corneum and keratinized epidermal structures. Among these proteases, the secreted subtilisin protease Sub3 was found to be required for adherence of M. canis arthroconidia to feline epidermis. This protease is synthetized as a preproenzyme consisting of a signal peptide followed by the propeptide and the protease domain. In order to assess whether the enzymatic activity of Sub3 could be responsible for the role of the protease in the adherence process, we expressed and characterized the propeptide of Sub3 and demonstrated that this propeptide is a strong inhibitor of its mature enzyme. This propeptide acts as a noncompetitive inhibitor with dissociation constants, K(I) and [Formula: see text] of 170 and 130 nM respectively. When tested for its capacity to inhibit adherence of M. canis to feline epidermis using an ex vivo adherence model made of feline epidermis, the propeptide does not prevent adherence of M. canis arthroconidia because it loses its capacity to inhibit rSub3 following a direct contact with living arthroconidia, presumably through inactivation by fungal membrane-bound proteases.

Effect of phenotypic variation in Xenorhabdus nematophila on its mutualistic relationship with the entomopathogenic nematode Steinernema carpocapsae.

The entomopathogenic nematode Steinernema carpocapsae is mutualistically associated with the bacterium Xenorhabdus nematophila. Infective Juveniles (IJs) transport X. nematophila cells that provide them with good conditions to reproduce within the insect. In the laboratory, long term stationary-phase culture conditions sometimes lead X. nematophila's variant 1 cells, which were previously isolated from the worms, to spontaneously and irreversibly change into a new phenotypic variant (variant 2). In this paper, we tested the ability of each phenotypic variant to (i) be transmitted by IJs, (ii) to optimize the worm's fitness within the insect, and (iii) to counteract the effect of closely related antagonistic bacteria previously shown as being able to totally prevent S. carpocapsae's reproduction within the insect. We found that IJs did associate with cells of both phenotypes but that the variant 2 cells were preferentially retained by the nematodes when both variants were present in the insect. Both phenotypic variants led to the same fitness of S. carpocapsae in insects not infected by antagonistic bacteria. In insects infected by antagonistic bacteria, both variants were able to provide protection to S. carpocapsae. Nevertheless, this protection depended on the phenotypic variant and the antagonistic bacteria that were co-injected into the insect. Further analysis conduced in vitro showed that this variability could be partly linked to the sensitivity of each antagonistic bacterium to xenorhabdicin, produced by X. nematophila.

[High-risk factors in anesthesiology and methods of detection]. / Facteurs de haut risque en anesthésiologie et moyens de dépistage

This study demonstrates the importance of allergies to drugs used in premedication and enables one to realize the practical difficulty in picking out the causal drug allergies in anaesthetic accidents. From the practical point of view, it is evidently impossible to carry out L.T.T.s in all patients, considered as being exposed to an allergic risk in anaesthesia. It could however be envisaged carrying out ingestion tests such as are used in order to demonstrate intolerance to iodine, by the administration of small doses of Lugol's iodine or tablets containing iodine, and which lead to benign digestive intolerance reactions.

[Mushroom grower's lung. Apropos of 3 cases]. / Le poumon du champignonniste. A propos de trois cas.

Three cases of mushroom growers lung, responding to the criteria for an extrinsic allergic alveolitis, have been observed in the Hôpital Bichat, Paris. In the first case, a "semi-delayed" hypersensitivity phenomenon of type III was evoked, an "immediate" type I phenomenon in case 2, and an association of the two in the third case. Clinical manifestations may develop very rapidly in subjects working in areas where they are exposed to a high inoculum of fungal products. Multiple antigens are involved: Psalliota, actinomycetes of different varieties, manure substrate, fungal spores, bacteria, cereal dust, etc. A recognized occupational disease, it leads to a change in activity and the right to compensation.