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Abstract??In theAnophelesmidgut,Plasmodium falciparumproduces a specific chitinase able to penetrate the blood meal surrounding the chitin-containing peritrophic membrane (PM). High levels of an analogous chitinase, chitotriosidase (CHIT), may be found in human blood, being the markers of macrophage activation. To verify the hypothesis that CHIT present in malaria patient blood could help parasite to overcome PM, we carried out a bioassay by feedingAnopheles stephensifemales on an artificial apparatus that contained human blood from four different sources and with different chitinase concentrations: (1) healthy donors, as negative controls; (2) patients with malaria; (3) patients with Gaucher disease; and (4) whole blood enriched with commercialP. falciparumchitinase, as positive controls. After 16, 20 and 24?h of bloodfeeding, mosquitoes were dissected to extract the midgut and assess the effect of the different chitinases on membrane structure. Optical microscopy showed that formation of PM was clearly complete after 16?h in the posterior midgut fromAnophelesalready fed with healthy donor bloods. By contrast, PM formation was visible after 16?h in the posterior midgut of mosquitoes fed with malaria and Gaucher patient bloods but appeared clearly damaged at 20 and 24?h. At the same time, the PM formation was almost completely inhibited in the midgut ofAnophelesfed withP. falciparumchitinase-enriched bloods. These alterations were clearly confirmed by transmission electronic microscopy. In the present paper, we demonstrate that human CHIT from different sources is active on anophelines? PM. [ABSTRACT FROM AUTHOR]