Biochemical pathway of melanotic encapsulation of Brugia malayi in the mosquito, Armigeres subalbatus

The mosquito, Armigeres subalbatus, is naturally resistant to the filarial worm, Brugia malayi, and microfilariae (mf) penetrating the midgut are killed by melanotic encapsulation reactions in the hemocoel within 48 h following ingestion. This vector-parasite system was used to assess changes in hem...

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Bibliographic Details
Published in:Developmental and comparative immunology 1995-05, Vol.19 (3), p.205-215
Main Authors: Zhao, Xueling, Ferdig, Michael T., Li, Jianyong, Christensen, Bruce M.
Format: Article
Language:English
Subjects:
Animals
Armigeres subalbatus
Arylamine N-Acetyltransferase - metabolism
Brugia malayi
Brugia malayi - metabolism
Culicidae
Culicidae - immunology
Culicidae - parasitology
Diptera
Dopa
Dopa decarboxylase
Female
Gerbillinae
Hemolymph - chemistry
Immunity, Innate
Insect immunity
Melanins - metabolism
Melanization
Monophenol Monooxygenase - metabolism
Phenol oxidase
Tyrosine
Tyrosine - analysis
Tyrosine derivatives
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Summary:The mosquito, Armigeres subalbatus, is naturally resistant to the filarial worm, Brugia malayi, and microfilariae (mf) penetrating the midgut are killed by melanotic encapsulation reactions in the hemocoel within 48 h following ingestion. This vector-parasite system was used to assess changes in hemolymph tyrosine, tyrosine derivatives, and catecholamine-metabolizing enzyme activities using high pressure liquid chromatography with electrochemical detection (HPLC-ED) during melanotic encapsulation reactions against mf. Tyrosine and dopa were detected in the hemolymph of both control and immune-activated (mf-exposed) mosquitoes, but not dopamine or N-acetyl dopamine (NADA). Tyrosine was significantly increased in immune-activated mosquitoes at 6 and 12 h post blood feeding, but was depleted following intrathoracic inoculation of mf in the absence of a blood meal. Dopa also was elevated in immune-activated mosquitoes at 6, 12, and 24 h post-exposure to mf. There were significant increases in phenol oxidase (PO) and dopa decarboxylase (DDC) activities in immune-activated mosquitoes as compared to controls, and these elevated activities were correlated with changes in tyrosine and dopa levels in the hemolymph. No significant differences in N-acetyl transferase (NAT) and dopachrome conversion enzyme (DCE) activities between control and immune-activated mosquitoes were observed. The possible roles these molecules play in melanotic encapsulation reactions of A. subalbatus against mf are discussed.
ISSN:0145-305X
1879-0089
DOI:10.1016/0145-305X(95)00005-E