Abstracts - Deutsche Zoologische Gesellschaft

Physiology Posters 187P PH.1 - ENCorrelation of Listeria pathogenicity in mammals and Galleria mellonella representinga convenient and reliable model hostKrishnendu MukherjeeApplied Entomology, Justus-Liebig-Universität, GießenInnate immunity is a conserved defense mechanism in all Eukaryota and particularly insects haswidely been used as powerful model organisms to study host-pathogen interactions. Here, we representGalleria mellonella as a reliable, robust insect model host for studying infection mechanisms ofthe important bacterial pathogen Listeria monocytogenes. We tested different species, serotypes, andmutants of Listeria and found that L. monocytogenes causing significant high mortality of Galleriacaterpillars. Similar to mammals, the virulence gene cluster of L. monocytogenes was found to bethe main regulator of pathogenesis including polymerization of host actin. However, pre-immune activationof caterpillars resulted in the synthesis of antimicrobial peptides which provided resistanceagainst Listeria. Among the different antimicrobial peptides we found galiomycin, gallerimycin,IMPI and lysozyme to be strongly induced after infection. We performed RNAi knock-down of IMPIand found 30% and 50% reduction of IMPI mRNA level in insect fat body and hemocytes, respectively,with no significant effect on survival of infected larvae. Administration of different autophagyinducing therapeutics, such as rapamycin and AG 1478, resulted in higher survival rate, indicatingan important immune defense mechanism in Galleria which is similar to mechanisms known frommammals. In conclusion, we have developed the use of Galleria which can be reared at 37°C, asconvenient, low-cost, and ethically acceptable model host for examining infections of intracellularpathogens such as L. monocytogenes.P PH.2 - ENSporulation and excystation of the coccidian parasite Eimeria nieschulzi Dieben 1924(Apicomplexa, Coccidia) in rats (Rattus norvegicus L.)Michael Kurth 1 , Stefanie Wiedmer 2 , Rolf Entzeroth 21Molecular Biotechnolgy, Department of Biology, TU Dresden; 2 Institute of Zoology, TU DresdenEimeria species belong to the phylum Apicomplexa which includes several pathogenic unicellulareukaryotic parasites in humans and animals like malaria, toxoplasmosis or coccidosis. Eimeria specieshave a monoxenous life cycle with a stringent progression of stages. Sporulation of oocysts andexcystation processes in coccidian parasites Eimeria are not well understood and may be differentwithin the genus. The excystation of sporozoites of chicken Eimeria species occurs after breakingof the oocysts wall, caused by the gizzard, followed by a trypsin/bile induced opening of the sporocysts.The excystation of Eimeria nieschulzi in rats however includes two protease depending steps.The degradation of the oocysts wall takes place within three hours with pepsin. The excystationand activation of the sporozoites within 10 min this is followed by a trypsin/bile treatment. Furtherstudies into the mode of action of pepsin showed that unsporulated oocysts are resistant againstproteases in contrast to sporulated oocysts. Observations by SEM and TEM show that degradationof the oocyst wall begins by digestion of the inner wall and not by the outer wall. The entry side ofpepsin may the micropyle which is probably not completely differentiated in unsporulated oocyststo prevent protease digestion in the environment. In the bird Eimeria species we cannot find anyprotease sensitivity of oocysts. This reflects the differences within the genus Eimeria depending ontheir host adaption.