Cellular immune response of the mosquito Culex quinquefasciatus (Diptera-Culicidae) to Candida albicans infection

J. S. Bento 1 , E. C. de Araújo 1 , C. M. R. de Albuquerque 1 , C. A. Peixoto 2 & H. Hurd 3

1 Mest. em Biologia Animal, Dept. de Zoologia Univ. Federal de Pernambuco-Recife PE, Brazil, 2 Centro de Pesquisas Aggeu Magalhães, Dept. de Patologia e Biologia Celular - Recife PE, Brazil; 3 Centre for Applied Entomology and Parasitology School of Life Sciences Huxley Building, Keele Univ., Staffordshire, ST5 5BG, UK.

Insects have an efficient defense system against infection. The cellular immune defense mechanism initiated by the mosquito Culex quinquefasciatus infected with the fungi Candida albicans was investigate in this study. Differences in haemocyte counts in the haemolymph perfused from uninoculated, saline-inoculated and C. albicans infected mosquitoes were compared using an optical microscopic. This showed that the relative proportion of plasmatocytes (48.6%; 50.7%; 45%) was higher and the proportion of cells granular was concomitantly lower (38%; 36.8%; 35%) in infected mosquitoes respectively at 3, 6 and 18h after inoculation. Electron microscopy demonstrated that yeast cells were phagocytized. Melanized nodules were found attached to different insect tissues at 24 to 72h following infection. Treatment of adults with the phospholipase A2, inihibitor of dexametasose, significantly inhibit nodulation in vivo. These results suggested that phagocytosis followed by nodule formation were capable of clearing the C. albicans from the haemolymph and that eicosanoids may mediate cellular immune reactions of the mosquito C.quinquefasciatus.

Index terms:Culex quinquefasciatus, Candida albicans, cellular immune response

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