Lagenidium giganteum (Oomycetes: Lagenidiales), a facultative parasite of mosquito larva, is the only biological control agent (this category does not include the microbial insecticides produced by various Bacillus spp.) that is approaching operational use for mosquito control. This is significant because the use of chemicals commonly applied for mosquito control is being increasingly restricted due to regulatory action or development of resistance. The infective stage of the fungus is a motile zoospore, produced by either sexual or asexual reproduction, which specifically attaches to, encysts, and penetrates the cuticle of mosquito larvae. Use of L. giganteum is limited, therefore, to mosquito habitats in which sporulation, host recognition by the zoospore, and subsequent events in the infection process can occur. The long-term objective of the proposed research is to identify the molecular bases for host recognition by the fungus, so that selection for more virulent isolates can proceed systematically. This work will provide basic information (protoplast generation, proteins involved in host infection) for genetic engineering should this be necessary to develop more virulent strains or to modify host range. The project encompasses two main areas; 1) Elucidation of the chemical components on the cuticular surface of larvae and pupae of Culex tarsalis which trigger L. giganteum zoospore attachment, encystment and penetration; and 2) Identification of the putative proteins on the zoospore anterior flagellum and cyst cell wall which are involved in the recognition process. Investigations of cuticular chemistry will entail isolation and structural identification of lipids, (poly)phenols, chitin and its derivatives, and other components using high pressure liquid chromatography, gas chromatography - mass spectrometry, nuclear magnetic resonance and other standard spectroscopic techniques. Selective modification or removal of cuticular components will be followed by assaying the effects of these treatments on zoospore behavior. Zoospore and cyst proteins, and peroxidase isozymes will be purified and characterized. Monoclonal antibodies will be made to these proteins, and fluorescence microscopy used to confirm their spatial distribution on the zoospore/cyst surface. Documentation of zoospore/cyst behavior following incubation with the various monoclonals will confirm a role for the complementary proteins in host recognition.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Tropical Medicine and Parasitology Study Section (TMP)
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University of Washington
Schools of Arts and Sciences
United States
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Kerwin, J L; Whitney, D L; Sheikh, A (1999) Mass spectrometric profiling of glucosamine, glucosamine polymers and their catecholamine adducts. Model reactions and cuticular hydrolysates of Toxorhynchites amboinensis (Culicidae) pupae. Insect Biochem Mol Biol 29:599-607
Kerwin, J L; Turecek, F; Xu, R et al. (1999) Mass spectrometric analysis of catechol-histidine adducts from insect cuticle. Anal Biochem 268:229-37
Turecek, F; Kerwin, J L; Xu, R et al. (1998) Distinction of N-substituted histidines by electrospray ionization mass spectrometry. J Mass Spectrom 33:392-6
Gu, M; Kerwin, J L; Watts, J D et al. (1997) Ceramide profiling of complex lipid mixtures by electrospray ionization mass spectrometry. Anal Biochem 244:347-56
Kerwin, J L (1997) Profiling peptide adducts of oxidized N-acetyldopamine by electrospray mass spectrometry. Rapid Commun Mass Spectrom 11:557-66
Kerwin, J L (1996) Negative ion electrospray mass spectrometry of polyphenols, catecholamines and their oxidation products. J Mass Spectrom 31:1429-39
Kerwin, J L; MacKichan, J K; Semon, M J et al. (1996) Sterol and steryl ester regulation of phospholipase A2 from the mosquito parasite Lagenidium giganteum. Lipids 31:1179-88
Kerwin, J L; Torvik, J J (1996) Identification of monohydroxy fatty acids by electrospray mass spectrometry and tandem mass spectrometry. Anal Biochem 237:56-64
Kerwin, J L; Wiens, A M; Ericsson, L H (1996) Identification of fatty acids by electrospray mass spectrometry and tandem mass spectrometry. J Mass Spectrom 31:184-92