AEDES-AEGYPTI - INDUCED ANTIBACTERIAL PROTEINS REDUCE THE ESTABLISHMENT AND DEVELOPMENT OF BRUGIA-MALAYI

The effect of host immune activation on the development of Brugia mala yi in one susceptible and four refractory strains of Aedes aegypti and in Armigeres subalbatus was assessed. A. aegypti that were immune act ivated by the injection of saline or bacteria 24 hr before feeding on a B. malayi-infected gerbil had significantly reduced prevalences and mean intensities of infection from those of naive controls when expose d to bloodmeals with low (105 mf/20 mu l) and medium (160 mf/20 mu l) microfilaremias. At a higher microfilaremia (237 mf/20 mu l) there wer e no significant differences in mean intensities, suggesting that the number of parasites ingested may affect the host's ability to mount an effective defense response. Because the major immune proteins in A. a egypti are defensins, we did Northern analyses of fat body RNA 8 hr af ter immune activation or bloodfeeding. All mosquitoes demonstrated rap id transcriptional activity for defensins following immune activation by intrathoracic inoculation with either saline or bacteria. However, no strain of A. aegypti, susceptible or refractory to B. malayi, nor A r. subalbatus produced defensin transcripts after bloodfeeding on an u ninfected or a B. malayi-infected gerbil. These data suggest that indu cible immune proteins of mosquitoes can reduce the prevalence and mean intensity of infections with ingested parasites, but these proteins a re not expressed routinely after parasite ingestion and midgut penetra tion and probably do not contribute to existing refractory mechanisms. Immune proteins such as defensins, however, represent potential candi dates to genetically engineer mosquitoes for resistance to filarial wo rms. (C) 1996 Academic Press, Inc.