Les ennemis naturels d'insectes du cotonnier au Tchad : premières données sur les champignons de l'ordre des Entomophthorales

En 1986 et en 1987, des épizooties à entomophthorales (zygomicètes) ont été observées dans des populations du puceron #Aphis gossypii et dans des populations adultes de l'aleurode #Bemisia tabaci évoluant sur cotonnier dans le sud du Tchad. C'est la première fois que la présence d'entomophthorales est signalée dans ce pays. Les auteurs présentent tout d'abord le cycle biologique de ces champignons entomopathogènes et les différents éléments morphologiques qui y sont impliqués. Etant donné qu'il est indispensable de récolter et de préparer correctement les insectes tués par une entomophthorale afin de pouvoir identifier celle-ci, les techniques utilisées sont ensuite détaillées. Les symptômes de la mycose d'#Aphis gossypii sont alors décrits et la morphologie respective des spores de résistance, des conidies primaires et des capilloconidies de l'agent responsable, #Neozygites fresenii, est illustrée. L'entomophthorose des adultes de #Bemisia tabaci est due à une espèce inédite de zoophthora, dont la description sera présentée par ailleurs. Les auteurs précisent, cependant, les symptômes de la mycose et illustrent à l'aide d'une autre espèce la morphologie caractéristique des conidies primaires et des capilloconidies au sein du genre Zoophthora. Jusqu'aux observations effectuées au Tchad en 1986 et en 1987, aucun cas d'entomophthorose n'était connu sur #Bemisia tabaci. (Résumé d'auteur

Occurrence of entomopathogenic fungi in soils in Southern Italy

The natural occurrence of entomopathogenic fungi was investigated in Southern Italian soils using larvae of Galleria mellonella L. (Lepidoptera: Galleriidae) as “bait insect”. Since September (1996) to March (1997) 188 samples of soil were collected from different habitats (woodland, orchard, field, seacoast, grassland, uncultivated land and salt pan). Parasitic fungi were obtained from 14.9% of the soil samples. There were 3 entomopathogenic species: Metarhizium anisopliae (Metchnikoff) Sorokin, Paecilomyces lilacinus (Thom) Samson and Beauveria bassiana (Balsamo) Vuillemin. The most common fungal pathogen was B. bassiana. Both M. anisopliae and P. lilaci- nus were isolated only once. The occurrence of B. bassiana seems to be affected by the soil type and the habitat. Key words: survey, Beauveria bassiana, Metarhizium anisopliae, Paecilomyces lilacinus. FUNGHI ENTOMOPATOGENI NEI TERRENI DELL’ITALIA MERIDIONALE È stata effettuata un’indagine per valutare la presenza e la distribuzione di funghi entomopatogeni nei terreni dell’Italia meridionale utilizzando larve di Galleria mellonella L. (Lepidoptera: Galleriidae) come insetto esca. Da settembre 1996 a marzo 1997, sono stati esaminati 188 cam- pioni di terreno provenienti da diversi biotopi. Sono state rinvenute larve infettate da funghi in 28 campioni (14,9%) e sono state identificate 10 specie di funghi parassiti di cui 3 propriamente entomopatogeni: Metarhizium anisopliae (Metchnikoff) Sorokin, Paecilomyces lilacinus (Thom) Samson e Beauveria bassiana (Balsamo) Vuillemin. Il fungo patogeno rinvenuto con maggior frequenza è risultato essere B. bassiana. La sua presenza sembra correlata alle caratteristiche del suolo e dell’habitat. Parole chiave: indagine, Beauveria bassiana, Metarhizium anisopliae, Paecilomyces lilacinus

In Vitro Evaluation of a Soluble Leishmania Promastigote Surface Antigen as a Potential Vaccine Candidate against Human Leishmaniasis

International audiencePSA (Promastigote Surface Antigen) belongs to a family of membrane-bound and secreted proteins present in severalLeishmania (L.) species. PSA is recognized by human Th1 cells and provides a high degree of protection in vaccinated mice.We evaluated humoral and cellular immune responses induced by a L. amazonensis PSA protein (LaPSA-38S) produced in aL. tarentolae expression system. This was done in individuals cured of cutaneous leishmaniasis due to L. major (CCLm) or L.braziliensis (CCLb) or visceral leishmaniasis due to L. donovani (CVLd) and in healthy individuals. Healthy individuals weresubdivided into immune (HHR-Lm and HHR-Li: Healthy High Responders living in an endemic area for L. major or L. infantuminfection) or non immune/naive individuals (HLR: Healthy Low Responders), depending on whether they produce high orlow levels of IFN-c in response to Leishmania soluble antigen. Low levels of total IgG antibodies to LaPSA-38S were detectedin sera from the studied groups. Interestingly, LaPSA-38S induced specific and significant levels of IFN-c, granzyme B and IL-10 in CCLm, HHR-Lm and HHR-Li groups, with HHR-Li group producing TNF-a in more. No significant cytokine response wasobserved in individuals immune to L. braziliensis or L. donovani infection. Phenotypic analysis showed a significant increasein CD4+ T cells producing IFN-c after LaPSA-38S stimulation, in CCLm. A high positive correlation was observed between thepercentage of IFN-c-producing CD4+ T cells and the released IFN-c. We showed that the LaPSA-38S protein was able toinduce a mixed Th1 and Th2/Treg cytokine response in individuals with immunity to L. major or L. infantum infectionindicating that it may be exploited as a vaccine candidate. We also showed, to our knowledge for the first time, the capacityof Leishmania PSA protein to induce granzyme B production in humans with immunity to L. major and L. infantum infectio