Cloning and preliminary characterization of a novel cuticular antigen from the filarial parasite Dirofilaria immitis

Ultrastructural analysis of Wuchereria bancrofti (Nematoda: Filarioidea) body wall

Bancroftian filariasis constitutes the principal mosquito-borne nematode infection of humans and the surface of adult of Wuchereria bancrofti seems to be especially important in the intricate interplay between host and parasite. The study of the parasite's surface structure might help to understand the localization and function of various organelles. W. bancrofti adult worms were recovered from untreated patients during hydrocele repair surgery and studied by transmission electron microscopy. The body wall of adult parasite is composed of cuticle, hypodermis and muscular layer. Cuticle is the external layer and shows transverse cuticular striation. It is composed by an epicuticle, cortical layers, median layer, fibrous layers and basal layer. The epicuticle is the most external cuticular layer and appears as a single laminar electron-dense layer. The cortical external region is more electron-dense and granular in appearance than the inner cortical layer. Electron-dense structures, called bosses are randomly distributed filling the cuticular striation. The median layer is formed by an electron-dense and continuous thick line. The fibrous layer is subdivided in inner and external layers connected by projections. The basal layer includes a large quantity of membranous projections directed toward the hypodermis. The hypodermis is a syncytium where some cellular organelles are observed. The somatic musculature is meromyarian. The muscle fibers consist of contractile and non-contractile regions and the contractile region is composed of myofilaments separated by dense body. This is the first study of W. bancrofti adult worms obtained from untreated patients and studied by transmission electron microscopy.

Identification and cloning of a novel tetraspanin (TSP) homologue from Brugia malayi

This is the first report of a tetraspanin (TSP)-like molecule in the lymphatic filarial parasites. Expressed sequence tag (EST) database search for TSP like molecules in the filarial genome resulted in three significant EST hits (two partial ESTs from Brugia malayi and one full length EST from Wuchereria bancrofti). The full length gene cloned from B. malayi showed significant similarity to Caenorhabditis elegans TSP and human TSP and hence the gene was named B. malayi TSP (BmTSP). Subsequent Genbank analysis with the predicted ORF of BmTSP showed additional homologous genes reported from Schistosoma mansoni and Taenia solium parasites. Structural analyses showed that BmTSP has four transmembrane domains and other conserved domains such as CCG and two other critical cysteine residues present within the large extracellular loop similar to other reported TSPs. In addition, putative post-translational modifications such as N-glycosylation, protein kinase c phosphorylation, casein kinase II phosphorylation and N-myristoylation sites have been found in BmTSP sequence. Further, PCR analyses showed that BmTSP is differentially transcribed, with highest level of expression being present in the adult stages followed by L3 and mf stages. This study thus describes a novel TSP cloned from B. malayi, its putative functions in cuticle biogenesis and role in protective immunity.

Effect of piperazine (diethylenediamine) on the moulting, proteome expression and pyrophosphatase activity of Ascaris suum lung-stage larvae

Piperazine (diethylenediamine) is an anthelmintic widely used against animal and bird ascariasis. In this study, we show that treatment with piperazine blocks Ascaris suum larval moulting and development processes and affects larval proteome expression profiles. A. suum lung-stage L3 (LL3) obtained from an infected rabbit's lungs were cultured in RPMI medium in the presence of increasing concentrations of piperazine sulfate (Pzes). Our results showed that Pzes potently inhibited moulting of A. suum LL3 in a dose-dependent manner and that moulting was completely blocked (100%) at 50mM concentrations. We then examined the changes in A. suum LL3 proteome expression patterns following Pzes exposure using two-dimensional (2D) electrophoresis. Pzes exposure inhibited expression of at least 16 major protein spots in unmoulted LL3 out of more than 200 visible protein spots resolved on 2D gels prepared from moulted larvae (i.e., lung-stage L4). Pzes exposure also inhibited expression of 13 immunogenic protein spots in unmoulted LL3. More importantly, Pzes exposure inhibited activity of a moulting-specific enzyme, inorganic pyrophosphatase of A. suum (AsPPase), by 26%. Expression of native AsPPase was also reduced following Pzes exposure as detected by immunoblotting and immunofluorescent staining. Transmission electron microscopy showed that Pzes interfered with growth and ecdysis of the cuticle and caused damage to gut tissues of the larvae. Our results suggest that A. suum LL3 may become a suitable model to screening new-class anthelmintics with antimoulting functions and that A. suum LL3-Pzes may serve as a useful tool for identification of moulting-specific potential proteins in Ascaris roundworms.

Fluoride exposure inhibits protein expression and enzyme activity in the lung-stage larvae ofAscaris suum

Sodium fluoride (NaF) is an anion that has been previously shown to block the moulting process ofAscaris suumlarvae. This study describes moulting and development-specific protein expression profiles ofA. suumlung-stage L3 (AsLL3) following NaF exposure. AsLL3s cultured in the presence or absence of NaF were prepared for protein analysis using two-dimensional (2D) electrophoresis. NaF exposure inhibited at least 22 proteins in AsLL3 compared with moulted larvae (i.e. AsLL4). A further comparison of AsLL4 with those of pre-cultured AsLL3 and NaF-exposed AsLL3 revealed 8 stage-specifically and 4 over-expressed proteins. Immunoblot analysis revealed an inhibition by NaF of 19 immunoreactive proteins. Enzyme assay and immunochemical data showed an inhibition of the moulting-specific inorganic pyrophosphatase activity by 41% and a decreased expression in NaF-treated larvae, indicating its significance in the moulting process. A protein spot associated with NaF inhibition was isolated and identified by peptide mass spectrometry and bioinformatics approaches to be a member of 3–hydroxyacyl–CoA dehydrogenase/short-chain dehydrogenase enzyme families. These results have implications for the identification of proteins specific to the moulting process as potential chemotherapeutic targets.

Pyrophosphatase of the roundworm Ascaris suum plays an essential role in the worm's molting and development

Previous studies indicated that inorganic pyrophosphatase of Ascaris suum (AsPPase) plays an important role in larval survival in the host. Here we describe a precise role for AsPPase in larval molting and development and also describe the potential role of recombinant AsPPase (rAsPPase) in protective immunity to A. suum infection. Using reverse transcriptase PCR analysis, we found that disruption of AsPPase gene function by RNA interference resulted in suppression of AsPPase mRNA levels. RNA interference also caused inhibition of molting of third-stage larvae (31%) and suppression of native protein expression, as demonstrated by a 56% reduction in enzyme activity and quantified by immunoblot and immunofluorescence analyses, suggesting that AsPPase has a role in the molting process. The anatomic location of the AsPPase native enzyme in the hypodermis of larvae along with its elevated expression prior to and during the molting process supports such a role. Anti-rAsPPase immunoglobulin G (IgG) also resulted in 57% inhibition of molting of A. suum lung-stage third-stage larvae to fourth-stage larvae in vitro with developmental arrest. Antigenic epitopes of AsPPase overlapped the enzyme active sites. Mice immunized with rAsPPase exhibited high antigen-specific IgG antibody responses and were protected (>70%) against a challenge A. suum migratory-phase infection. Splenic T cells from rAsPPase-immunized mice produced low levels of T helper 1-type cytokines (gamma interferon and interleukin-2) in vitro but exhibited an elevated interleukin-10 response. A significantly high level of IgG1 subclass antibodies was found in immunized mice. Our results establish that AsPPase has a critical role in the molting and development of Ascaris roundworms and suggest the potential of AsPPase for use as a candidate vaccine against ascariasis.