Immune Defense Mechanisms of Culex quinquefasciatus (Diptera: Culicidae) against Candida albicans Infection

• Published in: Journal of invertebrate pathology Vol. 76; no. 4; pp. 257 - 262
• Main Authors: Da Silva, José B, De Albuquerque, Cleide M.R, De Araújo, Eva Cristina, Peixoto, Christina A, Hurd, Hilary
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-11-2000; Elsevier
• Subjects: Animals; Biological and medical sciences; Candida albicans; cellular defense; Culex - immunology; Culex - microbiology; Culex quinquefasciatus; Culicidae; Female; Fundamental and applied biological sciences. Psychology; hemocytes; Hemocytes - immunology; Hemocytes - microbiology; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; nodulation; Phagocytosis; Vectors. Intermediate hosts; Candida albicans; phagocytosis; nodulation; hemocytes; cellular defense; Culex quinquefasciatus; Animal microorganism relation; Candidiasis; Immune response; Mycosis; Insecta; Cellular immunity; Defense; Fungi; Infection; Experimental disease; Hemocyte; Arthropoda; Culicidae; Fungi Imperfecti; Invertebrata; Vector; Diptera; Phagocytosis; Thallophyta
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1006/jipa.2000.4980

Mosquitoes have an efficient defense system against infection. The cellular immune defense mechanism initiated by the mosquito Culex quinquefasciatus infected with the fungus Candida albicans was investigated in this study. Differences in the hemocyte counts in hemolymph perfused from uninoculated, saline-inoculated, and C. albicans-infected mosquitoes were compared using a light microscope. Phagocytosis was also investigated using electron microscopy. Four types of hemocytes were identified in control mosquitoes: prohemocytes (9.8%), plasmatocytes (38.8%), granular cells (44.2%), and oenocytoids (7.3%). Between 3 and 18 h postinoculation the total hemocyte count was significantly higher in infected, compared to uninfected, mosquitoes. Differential hemocyte counts from infected mosquitoes at 3, 6, and 18 h after inoculation showed that the relative proportion of plasmatocytes (48.6, 50.7, 45%) was higher and, concomitantly, the proportion of granular cells was lower (38, 36.8, 35%, respectively). Yeast cells were phagocytosed and limited growth was observed within the plasmatocytes. Melanized nodules were found attached to different insect tissues at 24 to 72 h following infection. These results suggest that phagocytosis, followed by nodule formation, was capable of clearing the hemolymph of yeast cells.