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Abstract: Ancylostoma ceylanicum belongs to the group of parasites commonly known as hookworms, blood-sucking nematodes which infect around 576 million people and hundreds of millions of animals. The interactions between these parasites and host immune systems are complicated and yet to be determined. Hookworm infections are usually long lasting and recurrent, due in part to their ability to synthesize macromolecules capable of modulating the host immune response. The interaction of parasite proteins with host immune systems has been proven, but so far there is no data describing the influence of astacin-like metalloproteases (expressed among different parasitic nematodes) on the human immune system. The cDNA encoding A. ceylanicum metalloprotease 2 (Ace-mtp-2) was cloned using RACE-PCR. Computational analysis was used to examine the immunogenicity and recombinant Ace-MTP-2 was used to investigate its influence on human THP-1 monocytes and macrophages. The Ace-mtp-2 gene encodes an astascin-like metalloprotease, with a theoretical molecular mass of 26.7kDa. The protease has a putative signal peptide, 11 potential phosphorylation sites, and two disulfide bridges revealed by computational analysis. Maximal expression of Ace-mtp-2 by A. ceylanicum occurs in the adult stage of the parasite, and Western blot indicates the secretory nature of the protease. This suggests the protease is working at the host–parasite interface and would likely be exposed to the hosts immune response. Recombinant protein were expressed in Escherichia coli and Pichia pastoris. Recombinant Ace-MTP-2 amplified the in vitro release of TNFα and induced release of IFNγ by lipopolysaccharide activated THP-1 macrophages. The presence of Ace-MTP-2 in secretory products of the adult parasite and the induction of IFNγ release may suggest an important role for Ace-MTP-2 in host–parasite interactions since IFNγ is suggested to be responsible for the protective immune response against adult hookworms. [Copyright &y& Elsevier]

Hookworms are intestinal nematodes that infect up to 740 million people, mostly in tropical and subtropical regions. Adult worms suck blood from damaged vessels in the gut mucosa, digesting hemoglobin using aspartic-, cysteine- and metalloproteases. Targeting aspartic hemoglobinases using drugs or vaccines is therefore a promising approach to ancylostomiasis control. Based on homology to metalloproteases from other hookworm species, we cloned the Ancylostoma ceylanicum metalloprotease 7 cDNA ( Ace-mep-7 ). The corresponding Ace-MEP-7 protein has a predicted molecular mass of 98.8 kDa. The homology to metallopeptidases from other hookworm species and its predicted transmembrane region support the hypothesis that Ace -MEP-7 may be involved in hemoglobin digestion in the hookworm gastrointestinal tract, especially that our analyses show expression of Ace-mep-7 in the adult stage of the parasite. Immunization of Syrian golden hamsters with Ace-mep-7 cDNA resulted in 50% (p < 0.01) intestinal worm burden reduction. Additionally 78% (p < 0.05) egg count reduction in both sexes was observed. These results suggest that immunization with Ace-mep-7 may contribute to reduction in egg count released into the environment during the A. ceylanicum infection. [ABSTRACT FROM AUTHOR]

Glutamate–cysteine ligase (GCL) is a heterodimer enzyme composed of a catalytic subunit (GCLC) and a modifier subunit (GCLM). This enzyme catalyses the synthesis of γ-glutamylcysteine, a precursor of glutathione. cDNAs of the putative glutamate–cysteine ligase catalytic ( Ace -GCLC) and modifier subunits ( Ace -GCLM) of Ancylostoma ceylanicum were cloned using the RACE-PCR amplification method. The Ace-gclc and Ace - gclm cDNAs encode proteins with 655 and 254 amino acids and calculated molecular masses of 74.76 and 28.51 kDa, respectively. The Ace -GCLC amino acid sequence shares about 70% identity and 80% sequence similarity with orthologs in Loa loa , Onchocerca volvulus , Brugia malayi , and Ascaris suum , whereas the Ace -GCLM amino acid sequence has only about 30% sequence identity and 50% similarity to homologous proteins in those species. Real-time PCR analysis of mRNA expression in L3, serum stimulated L3 and adult stages of A. ceylanicum showed the highest level of Ace -GCLC and Ace -GCLM expression occurred in adult worms. No differences were detected among adult hookworms harvested 21 and 35 dpi indicating expression of Ace-gclc and Ace-gclm in adult worms is constant during the course of infection. Positive interaction between two subunits of glutamate–cysteine ligase was detected using the yeast two-hybrid system, and by specific enzymatic reaction. Ace -GCL is an intracellular enzyme and is not exposed to the host immune system. Thus, as expected, we did not detect IgG antibodies against Ace -GCLC or Ace -GCLM on days 21, 60 and 120 of A. ceylanicum infection in hamsters. Furthermore, vaccination with one or both antigens did not reduce worm burdens, and resulted in no improvement of clinical parameters (hematocrit and hemoglobin) of infected hamsters. Therefore, due to the significant role of the enzyme in parasite metabolism, our analyses raises hope for the development of a successful new drug against ancylostomiasis based on the specific GCL inhibitor. [ABSTRACT FROM AUTHOR]