Scorpine is an antimicrobial peptide whose structure resembles a hybrid between a defensin and a cecropin. It exhibits antibacterial activity and inhibits the sporogonic development of parasites responsible for murine malaria. In this communication we report the production of scorpine in a heterelogous system, using a specific vector containing its cloned gene. The recombinantly expressed scorpine (RScp) in (Anopheles gambie) cells showed antibacterial activity against (Bacillus subtilis) and (Klebsiella pneumoniae), at 5 and 10 microM, respectively. It also produced 98% mortality in sexual stages of (Plasmodium berghei) at 15 microM and 100% reduction in (Plasmodium falciparum) parasitemia at 5 microM. RScp also inhibited virus dengue-2 replication in C6/36 mosquito cells. In addition, we generated viable and fertile transgenic (Drosophila) that overexpresses and correctly secretes RScp into the insect hemolymph, suggesting that the generation of transgenic mosquitoes resistant to different pathogens may be viable.

SummaryThe Entamoeba histolytica EhCPADH complex, formed by a cysteine proteinase (EhCP112) and an adhesin (EhADH112), is involved in adherence, phagocytosis and cytolysis. This makes this complex an attractive candidate as a vaccine against amoebiasis. Here, we produced the recombinant polypeptide EhADH243, which includes the adherence epitope detected by a monoclonal antibody against the EhCPADH complex. EhADH243 was purified, and the effect of the polypeptide on in vitro and in vivo virulence was studied. Antibodies against EhADH243 reacted with the EhCPADH complex and with the recombinant polypeptide. EhADH243 and antibodies against this polypeptide inhibited adherence, phagocytosis and destruction of cell monolayers by live trophozoites, but had little effect on cell monolayer destruction by trophozoite extracts. EhADH243 recognized a 97 kDa protein in the MDCK membrane fraction that could be a putative receptor for E. histolytica trophozoites. Hamsters immunized with EhADH243 developed humoral response against EhCPADH, and animals were partially protected from amoebic liver abscess.

The interaction of Rhodnius prolixus digestive enzymes with Trypanosoma cruzi could be important for parasite survival. We report herein the complete sequence of the messenger of a cathepsin L-like molecule (RpCat). The cDNA has 5'- and 3'- end UTRs and a methionine codon that corresponds likely to a translation initiation codon. In the deduced amino acid sequence, a region corresponding to an ERFININ domain, diagnostic of L-cathepsins, and a possible pro-peptide cleavage site were observed. At the C-terminus, a nine-amino acid sequence, almost identical to a secretion signal of human cathepsin L was found. RpCat messenger was expressed in intestines of R. prolixus adults, and from 1st to 4th but not in 5th instar nymph stages. In a similarity analysis, RpCat was grouped with L cathepsins forming a clear group separate of the B cathepsins.

Prostaglandins (PGs) participate in the regulation of vertebrate and in at least six insect orders' immune responses. We identified PGE 2 in midgut, fat body, Malpighian tubules, and ovarioles of Anopheles albimanus (Aa) mosquitoes. Our data indicate that PGE 2 synthesis in cultured midguts responds to the presence of two bacterial species, Micrococcus luteus and Klebsiella pneumoniae. The production of mRNA coding for antimicrobial peptides Aa-Attacin, Aa-Cecropin, and Aa-Gambicin was observed in cultured fat bodies and midguts. The production of these messengers was reduced in the presence of dexamethasone, and this effect was reversed by arachidonic acid. Adding PGE 2 to cultures resulted in increased Aa-cecropin mRNA and decreased Aa-attacin and Aa-gambicin mRNAs. Arch. Insect Biochem. Physiol. 68:14-25, 2008 KEYWORDS: insect immunity; arachidonic acid; dexamethasone; Anopheles albimanus; antimicrobial peptides INTRODUCTIONInsects resist the constant threat of invasion by microorganisms with integumental barriers and the presence of peritrophic matrix in their digestive tracts. When microbes overcome these first-line defenses, they encounter well-organized immune reactions that resemble mammalian innate immunity. Circulating hemocytes phagocytose microbial invaders and respond by forming microaggregates and nodules. Hemocytes also encapsulate those invaders, such as parasitoid eggs, too big to phagocytose (Stanley, 2006;Stanley and Miller, 2006). These cellular defense mechanisms are practically immediate upon microbial invasion, but complex humoral responses, including hemolymph clotting (Blandin and Levashina, 2004), melanization, and the production of antimicrobial peptides (Yu and Kanost, 2003;Lemaitre and Hoffmann, 2007) are deployed later.Eicosanoids including prostaglandins (PGs) are fatty acid metabolites that in mammals are produced by many cell types, including epithelial and immune cells, and play key roles in hemostasis and immune regulation, among many other functions (Harris et al., 2002). The biosynthesis of PGs in insects is initiated by a phospholipase A 2 (PLA 2 ) that cleaves membrane phospholipids (C20 polyunsaturated fatty acids including arachidonic acid [AA]), and the resulting products are converted to PGs' bioactive forms by cyclooxygenases (COX) (Stanley, 2000(Stanley, , 2006, but products of the lipoxygenase pathway (LOX) have been also documented (Galdelhak et al., 1995). The induction of eicosanoid biosynthesis by bacteria has been observed in several insect species (Stanley, 2006 and Miller, 2006). The information on the participation of eicosanoids in insect humoral immune responses is limited; PGs mediate the expression of genes encoding the antibacterial peptide cecropine and lysozime in the silkworm Bombyx mori (Morishima et al., 1997) and regulate the activation of prophenoloxidase (PPO) in two insect species, Galleria mellonella (Downer et al., 1997) and Rhodnius prolixus (García et al., 2004). However, they do not activate PPO in other insects (Lord et al., 2002;Goldswor...

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Malaria is one of the most important parasitic diseases in the world and a major public health problem because of emerging drug-resistant strains of Plasmodium. A number of synthetic and natural compounds are now being analysed to develop more effective antimalarial drugs. We investigated the effect of homeopathic preparations of Eupatorium perfoliatum and Arsenicum album on parasitemia using a rodent malaria model. We found significant inhibitory effect on parasite multiplication with both medications with a level of 60% for Eupatorium perfoliatum at a 30 CH potency. Arsenicum album 0/6 gave 70% inhibition but this was less stable than Eupatorium perfoliatum. The number of schizonts was higher in animals treated with homeopathic medications. Although the mechanism of action is unknown, these agents would be good candidates as alternative or complementary medications in the treatment of malaria.

The scavenger receptor family comprises transmembrane proteins involved in the recognition of polyanionic ligands. Several studies have established that members of this family are involved both in immunity and in developmental processes. In Drosophila melanogaster, one of the best characterized scavenger receptors is Croquemort, which participates in the recognition of apoptotic cells in the embryo. Although comparative genomic studies have revealed the presence of four orthologs of this receptor in the malaria vector Anopheles gambiae, little is known about their function. We have investigated the expression pattern of the four Croquemort orthologs during the mosquito life cycle. Croquemort transcripts SCRBQ2 and SCRBQ4 are expressed at all the developmental stages, while expression of Croquemort transcripts SCRBQ1 and SCRBQ3 is more restricted. We have also investigated the expression of the four Croquemort orthologs in the different organs of the adult female. Croquemort transcript SCRBQ2 is highly expressed in the A. gambiae female midgut. SCRBQ2 midgut gene expression was up-regulated after a non-infected or a Plasmodium berghei-infected blood meal, compared to its expression in midguts of sugar-fed females. Interestingly, knockdown of SCRBQ2 expression by dsRNA injection resulted in a 62.5% inhibition of oocyst formation, suggesting that SCRBQ2 plays a role in Plasmodium–mosquito interactions.

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