Ultrastructural localization of antigenic substances in Trichinella spiralis

TSL-1 antigens of Trichinella: An overview of their potential role in parasite invasion, survival and serodiagnosis of trichinellosis

The majority of studies on the immunobiology of Trichinella species have centred on the larval muscular phase (L1) with a view to identifying immunodominant antigens located on the surface of the cuticle and in the larval secretions; the nucleus of the parasite-host interaction. These antigens have been classified as eight groups (TSL-1-TSL-8), of which those belonging to the group TSL-1 have been most intensely studied. The principal constituents are glycoproteins, glycan carriers that contain a unusual sugar, the tyvelose (3,6-dideoxy-d-arabinohexose). Studies aimed at improving serodiagnostic techniques to detect trichinellosis indicate that these antigens are ideal candidates. They are capable of inducing a strong humoral response involving the generation of specific antibodies against beta-tyvelose, a sugar that seems to be exclusive to the Trichuroidea. Furthermore, these glycoproteins appear to fulfil an important function in the development and maintenance of the parasite in the muscular niche, and they appear to be fundamental for the invasion of the intestinal epithelium. It has also been demonstrated that specific monoclonal antibodies against tyvelose can mediate a degree of immunoprotection in the rat through the phenomenon known as rapid expulsion.

Antigens of trichinella spiralis

Following infection with Trichinella spiralis, the host elicits a strong immune response that causes rapid expulsion of parasites, a reduction in reproductive capacity of the remaining parasites a reduction in the number of larvae recovered from host muscles, and impairment of the mobility of worms in the intestines. The need to identify the antigens that evoke such responses is twofold: (1) to develop immunodiagnostic tools; and (2) to understand the basis of protective immunity. In this review, Yuzo Takahashi describes the antigenic profiles of T. spiralis, emphasizing immunocytochemical findings.

Molecular expression and characterization of a homologue of host cytokine macrophage migration inhibitory factor from Trichinella spp

A homologue of cytokine macrophage migration inhibitory factor (MIF) from complementary DNA (cDNA) of Trichinella spiralis and Trichinella pseudospiralis was expressed in Escherichia coli and characterized. The sequence analysis indicated that the predicted amino acid sequence has an identity of 57 and 44% with the MIF of nematodes Trichuris trichiura and Brugia malayi respectively, and 41 and 40% with that of a human and a mouse, respectively. The identity in sequences of cDNA and amino acids between T. spiralis and T. pseudospiralis was 91 and 86%, respectively. Western blot analysis showed that anti-MIF antibodies positively stained proteins from the extracts of adult worms or muscle larvae migrating at about 12.5 kDa (3 isoforms with isoelectric point 5.23, 5.72, and 6.29). Semiquantitative reverse transcriptase-polymerase chain reaction revealed that the gene was expressed in various developmental stages, including in adult worms, newborn larvae, precyst muscle larvae, and postcyst muscle larvae, although there was difference in the expression level among these stages. The immunohistochemical analysis showed the MIF exists in the muscle cells of the body wall and some stichocytes of larvae. Histopathology of T. spiralis-infected muscles revealed an accumulation of mononuclear cells around the worms, and immunocytochemical staining showed these cells were not macrophages. Mononuclear cells, including macrophages, were, however, observed in cardiac muscles where the parasite did not encyst. Macrophages accumulated around the Sephadex beads transplanted in mice subcutaneously, but this accumulation was profoundly inhibited when the beads were pretreated with MIF recombinant protein.

Trichinella spiralis: ultrastructural localization of a target antigen recognized by a monoclonal antibody

The localization of a 160-kDa molecule recognized by a monoclonal antibody of the IgG1-class (TS32D12) to Trichinella spirilis was demonstrated at the subcellular level. Mature muscle larvae recovered from infected mice were fixed with Zamboni solution, and embedded in LR white resin. Ultrathin sections were incubated with TS32D12 and subsequently stained using a secondary antibody-coated colloidal gold probe. TS32D12 reacted to constituents in the alpha-stichosome cells of the parasite; that is, alpha-granules and rough endoplasmic reticulum. Other structures were not recognized by the immunogold probe, but occasionally weak positive staining was seen on beta-granules, the cuticle, hypodermis and myofibrils.

Ultrastructural colocalization of phosphorylcholine and a phosphorylcholine-associated epitope in first-stage larvae of Trichinella spiralis

Although the presence of phosphorylcholine (PC) in Trichinella is well established, the structures of the TSL-4 antigens that bear this epitope are unknown. A subset of TSL-4 antigens (TSL-8 antigens) has been reported to be absent from the surface of first-stage T. spiralis larvae. We report experiments with a monoclonal antibody (mAb US2) developed in mice with a relative inability to produce antibodies to PC. In immunoblotting, mAb US2 and anti-PC mAb (BH8) showed apparently identical binding patterns. In addition, we used an immunogold double-labeling technique to study the anatomical distribution of the epitopes recognized by these mAbs; the results obtained indicate close colocalization of epitopes for BH8 and US2 in tissues of T. spiralis first-stage larvae. On the basis of these results, we suggest that US2 probably binds to all T. spiralis TSL-4 antigens, including TSL-8 antigens. We also clarify some conflicting previous reports on the distribution of PC immunoreactivity in first-stage larvae of T. spiralis.

Immunocytochemical localization of antigens in adult worms of Trichinella spiralis recognized by Fischer rats

We demonstrate the tissue localization, in adult Trichinella spiralis, of antigens recognized by Fischer rat sera at 32 weeks postinfection. Immunodominant antigens were located in a wide variety of tissues, including type 1 stichocyte granules, stichocyte cytoplasm, the canalicular tree, hemolymph, hypodermis, hypodermal glands, cord cytoplasm, intestinal-gland cell granules, membranous structures in the midgut epithelium, midgut-occupying substance, brush border, hindgut epithelial cytoplasm, hindgut cuticle, vaginal cuticle, epithelial cytoplasm of the female genital tract, microvilli and discrete areas of the ovum, embryo sheath, intersperm space, discrete areas in immature sperm, small granules and cup-shaped membrane structures of sperm, and exocrine granules in the seminal vesicle and ejaculatory duct. A small amount of antigen was located in the inner layers of the genital portion of the body cuticle. The precise localization of antigens in adult worms should form a basis for better analysis of T. spiralis-related immunology.

Anatomical location of phosphorylcholine and other antigens on encysted Trichinella using immunohistochemistry followed by Wheatley's trichrome stain

This work investigated the location on the parasite of Trichinella antigens recognized by the mouse immune system and the question as to which of them bear the epitope phosphorylcholine (PC). Wheatley's trichrome stain (initially developed for faecal smears) proved to be excellent for visualization of Trichinella structures, enabling four types of stichocyte to be distinguished. By applying this stain on infected muscle sections after immunocytochemistry using (a) anti-PC BH8 monoclonal antibodies, (b) serum from mice that had been infected twice in the presence of 0.05% thiabendazole (to prevent reproduction by adult females) and then bled on day 7 post-reinfection, (c) serum from infected mice that were bled on day 14 postinfection, or (d) serum from infected mice that were bled on day 42 postinfection, we found (1) that PC is an abundant structural epitope on the hypodermis/muscle, genital primordium and intestinal tract but is absent from the cuticle and stichosome; (2) that the principle secretory cells of adult worms are delta- and beta-stichocytes, whereas those of migrating and encysted L1 larvae are alpha-stichocytes; and (3) that Trichinella antigens recognized in the encysted phase of the parasite's life cycle are present in parasitized myofibres in the sarcoplasmic matrix and in the nucleoplasm of hypertrophic nuclei. The significance of these findings is discussed.

Trichuris muris: antigen recognition and transfer of immunity in mice by IgA monoclonal antibodies

Mesenteric node lymphocytes from mice that had been infected with the nematode Trichuris muris, and then boosted with adult worm excretory-secretory antigens were fused with myeloma cells to produce a panel of 9 monoclonal antibodies (MoAbs). Five of the MoAbs were of the IgA isotype. The antigen recognition profiles of these MoAbs were studied using SDS-PAGE and immunoblotting; three major profile patterns were identified. Five MoAbs recognized a major band in the MW range 43-48 kD; all recognized a range of antigens. Three MoAbs were used to localize antigens in the bodies of adult worms. Granules within the anterior stichocytes were recognized strongly, as was material within the eggs and pseudocoelom. Two MoAbs stained the cuticle. Although the phosphorylcholine (PC) determinant was widely distributed within worm tissues none of the MoAbs tested recognized PC. Passive transfer of immunity was achieved using two of the IgA monoclonals; no immunity was transferred by the IgM and IgG MoAbs used. The limited recognition profiles of these IgA MoAbs, and the ability to stain stichocyte granules, suggest that their protective activity results from an interaction with ES antigens.

Partial characterization of two antigens secreted by L1 larvae of Trichinella spiralis

Two protein antigens were isolated from excretory-secretory products of Trichinella spiralis by biochemical methods and characterized with respect to their chemical and immunological properties. One antigen, of apparent Mr 43,000, is an abundant secreted protein of infective L1 larvae, while the other, of 45-50 kDa, is present in smaller amounts. Yields, extinction coefficients, isoelectric points, amino acid compositions, and partial N-terminal amino acid sequences for each are reported. Partial amino acid sequences of peptides derived from the 43-kDa protein by cyanogen bromide cleavage have been determined. Treating a reduced-pyridylethylated derivative of the 43-kDa protein with glycopeptidase F (N-glycanase) resulted in formation of a transient product of 37 kDa followed by a stable polypeptide of 32 kDa (by SDS-PAGE), suggesting the presence of two N-linked carbohydrate groups. A similar result was obtained with the 45-50-kDa protein, which gave a transient doublet of 38 and 40 kDa and a final, stable product of 33 kDa, with a minor component of 35 kDa. Two glycosylation sites of the 43-kDa protein and one site of the 45-50-kDa protein can be identified in the amino acid sequences. Polyclonal antibodies prepared against the two proteins cross-reacted extensively, but failed to react with the doubly deglycosylated polypeptides in Western blots. The dominant epitopes present in the reduced-pyridylethylated polypeptides are, therefore, N-linked carbohydrate, although the presence of peptide epitopes in the native proteins cannot be excluded.