Antibody responses to chimeric peptides derived from parasite antigens in mice and other animal species

Peptide vaccines constitute an interesting alternative to classical vaccines due to the possibility of selecting specific epitopes, easy of production and safety. However, an inadequate design may render these peptides poorly immunogenic or lead to undesirable outcomes (e.g., formation of B neoepitopes). As an approach to vaccine development, we evaluated the antibody response to chimeras composed of two or three known B epitopes from Trichinella and Fasciola, and several linkers (GSGSG, GPGPG and KK) in species as different as mice, sheep and turbot. All these species could mount an effective immune response to the short chimeric peptides. Nevertheless, this response depended on several factors including a favorable orientation of B-cell epitopes, adequateness of linkers and/or probability of formation of T neoepitopes. We also observed that, at least in mice, the inclusion of a decoy epitope may have favorable consequences on the antibody response to other epitopes in the chimera.

Ani s 1 and Ani s 7 recombinant allergens are able to differentiate distinct Anisakis simplex-associated allergic clinical disorders

Diagnosis in gastro-allergic anisakiasis (GAA) is straightforward, when clinical history is combined with further allergological evaluation of specific IgE by means of skin prick test and serum specific IgE. In Anisakis simplex sensitisation associated chronic urticaria (CU+), clinical evaluation of possible previous parasitism is difficult, and positive serum specific IgE could be due to cross-reactivity or other unknown factors. In this study, we evaluated the association between IgE seropositivity to the recombinant allergens Ani s 1 and Ani s 7 and several A. simplex-associated allergic disorders. Twenty-eight patients with GAA and 40 patients with CU+ were studied and their IgE responses were compared with a control group composed of patients with chronic urticaria not sensitized to A. simplex (CU-) according to the skin prick test, as well as a group of 15 healthy subjects not referring urticaria or currently A. simplex associated symptoms. 82.1% of GAA patients and 42.5% of CU+ patients were positive for Ani s 1 (P < 0.001), while the Ani s 7 allergen was recognized by 92.9 and 92.5% of sera from patients with GAA and CU+, respectively. The combined positivity obtained for both allergens reached 100% in GAA, and 95% in CU+. IgE determinations to Ani s 1 and Ani s 7 allergens are useful to diagnose the Anisakis infections and to differentiate among several A. simplex-associated allergic disorders. The IgE responses to Ani s 1 are mainly associated with GAA, while this molecule cannot be considered a major allergen in CU+ patients.

The Anisakis simplex Ani s 7 major allergen as an indicator of true Anisakis infections

Ani s 7 is currently the most important excretory/secretory (ES) Anisakis simplex allergen, as it is the only one recognized by 100% of infected patients. The allergenicity of this molecule is due mainly to the presence of a novel CX(17-25)CX(9-22)CX(8)CX(6) tandem repeat motif not seen in any previously reported protein. In this study we used this allergen as a model to investigate how ES allergens are recognized during Anisakis infections, and the usefulness of a recombinant fragment of Ani s 7 allergen (t-Ani s 7) as a marker of true Anisakis infections. The possible antigenic relationship between native Ani s 7 (nAni s 7) from Anisakis and Pseudoterranova decipens antigens was also investigated. Our results demonstrate that nAni s 7 is secreted and recognized by the immune system of rats only when the larvae are alive (i.e. during the acute phase of infection), and that this molecule is not present in, or is antigenically different from, Pseudoterranova allergens. The t-Ani s 7 polypeptide is a useful target for differentiating immunoglobulin E antibodies induced by true Anisakis infections from those induced by other antigens that may cross-react with Anisakis allergens, including P. decipiens. The results also support the hypothesis that the Ani s 7 major allergen does not participate in maintaining the antigenic stimulus during chronic infections.

Novel sequences and epitopes of diagnostic value derived from the Anisakis simplex Ani s 7 major allergen

BACKGROUND

Anisakis simplex allergens may cause severe allergic reactions in infected patients. Human anisakiasis can be specifically diagnosed by detection of immunoglobulin E (IgE) antibodies against O-deglycosylated nAni s 7 allergen captured by monoclonal antibody (mAb) UA3 (UA3-ELISA), although the nature of this important allergen is unknown. The aim of this study was to clone and characterize the Ani s 7 major allergen, and to obtain a recombinant fragment suitable for serodiagnosis.

METHODS

An Anisakis cDNA library was screened with mAb UA3 and a cDNA clone (rAni s 7) encoding a 1096-amino acid fragment of Ani s 7 (GenBank: EF158010) was identified. Bioinformatic tools and immunological and biochemical techniques were used to characterize the allergen obtained.

RESULTS

The rAni s 7 fragment comprised 19 repeats of a novel CX(17-25)CX(9-22)CX(8)CX(6) tandem repeat motif not seen in any previously reported protein sequence. An internal (435)Met-(713)Arg fragment of the rAni s 7 (t-Ani s 7) was expressed in Escherichia coli and evaluated for serodiagnostic utility. Indirect enzyme-linked immunosorbent assay (ELISA) with t-Ani s 7 identified as positive the same 60 sera as UA3-ELISA. The sequence MCQCVQKYGTEFCKKRLA from rAni s 7 was identified as the epitope recognized by mAb UA3, and is the target for over 60% of human IgE antibodies that react with O-deglycosylated nAni s 7.

CONCLUSIONS

In addition to their clear value for serodiagnosis of human anisakiasis, the nature of the novel sequences and epitopes identified in the Ani s 7 allergen are of interest for a better understanding of the mechanisms operating in Anisakis-induced allergy.

Efficacy of furunculosis vaccines in turbot, Scophthalmus maximus (L.): evaluation of immersion, oral and injection delivery

The commercial furunculosis vaccine Aquavac Furovac 5 and an autogenous vaccine, based on the challenge strain, induced immune protection in turbot, Scophthalmus maximus (L.), as shown in challenge tests 120 days post-immunization by injection (relative percentage of survival, RPS = 72-99%). This protective effect lasted for at least 6 months post-immunization at appreciable levels (RPS = 50-52%). Neither the autogenous vaccine nor the commercial vaccine was able to induce significant levels of protection against Aeromonas salmonicida in turbot when administered by immersion. Antibody levels were high or moderate in fish vaccinated by injection with the different vaccines and very low in fish vaccinated by immersion. The field results show that delivering an oral boost after the primary vaccination by injection did not enhance protection of turbot against furunculosis and that water-based (autogenous vaccine) and oil adjuvanted (Alpha Ject 1200) vaccines administered by injection conferred similar levels of protection (RPS > 80%) in turbot.

Effects of the histiophagous ciliate Philasterides dicentrarchi on turbot phagocyte responses

Philasterides dicentrarchi is an opportunistic histiophagous ciliate parasite causing systemic scuticociliatosis in cultured turbot (Scophthalmus maximus L.). This study investigated the effects of inoculation with live or killed trophozoites of this ciliate (plus 3% thioglycollate) on the in vitro phagocytic activity and respiratory-burst responses of inflammatory peritoneal leucocytes obtained from the fish thus treated. The phagocytic activity of leucocytes from fish inoculated with killed P. dicentrarchi was higher in the presence than in the absence of infected turbot serum (ITS). The effect of ITS was smaller in fish inoculated with live P. dicentrarchi, indicating modulation of the opsonic activity of ITS. Inoculation with live ciliates led to a significant increase in subsequent in vitro extracellular ROS production, but only when normal turbot serum (NTS) or ITS was included in the assay medium. Inclusion of live P. dicentrarchi in the medium abolished this increase, suggesting ROS-scavenging activity. Inoculation with live P. dicentrarchi led to a significant decline in subsequent in vitro intracellular ROS production; when NTS was included in the medium, there was a significant increase in intracellular ROS production, but no such increase was observed when ITS was included in the medium. Inoculation with live P. dicentrarchi alone did not increase subsequent in vitro NO? production in response to LPS; a significant increase was observed when NTS or ITS was included in the assay medium, but this increase was not affected by prior inoculation with P. dicentrarchi. These results suggest that the amphizoic nature of this parasite may reflect the ease with which it can develop mechanisms of evasion of the host immune response.

Minor interspecies variations in the sequence of the gp53 TSL-1 antigen of Trichinella define species-specific immunodominant epitopes1

Among the Trichinella TSL-1 antigens, whose antigenicity is generally due mainly to tyvelose-containing epitopes, gp53 is unusual in that its antigenicity is due mainly to protein epitopes. In the present study we mapped two of these epitopes, recognized by monoclonal antibodies (mAbs) that specifically recognize gp53 from all encysting Trichinella species (mAb US9), or gp53 from Trichinella spiralis alone (mAb US5). Based on previously published sequences of this glycoprotein [Mol. Biochem. Parasitol. 72 (1995) 253], in this study, we cloned the full gp53 cDNA from a new strain, Trichinella britovi (ISS 11; AN: ), and from another T. spiralis isolate (ISS 115; AN: ). The gp53 sequence comprised an ORF of 1239bp, coding for 412 amino acids, with 61 nucleotide differences (resulting in 38 residue changes) between the two species. Mapping of US5- and US9-recognized epitopes was undertaken through the construction and expression in the pGEX4T vector of truncated gp53 peptides, and by the construction of peptides derived from the antigenic regions. The epitope recognized by mAb US9 was a linear peptide of 8 residues, 33Met- 40Ser, located in the amino-terminal region, while the corresponding epitope recognized by mAb US5 was a 47-amino acid sequence containing two alpha-helix regions flanked by random coils, 290Thr- 336Lys. Molecular modeling of these peptides seems to indicate that recognition of the US9 epitope depends on the presence of two available hydroxyl groups provided by one methionine and one serine on T. spiralis gp53 (not present on Trichinella pseudospiralis gp53). Additionally, the stability of the US5 epitope seems to depend on correct folding of the 47-amino acid sequence (only present in T. spiralis). The relevance of these findings for understanding the antigenic recognition of Trichinella TSL-1 antigens, and for further studies to investigate possible function(s) of gp53 in Trichinella, is discussed.

Cysteine proteinase activities in the fish pathogenPhilasterides dicentrarchi(Ciliophora: Scuticociliatida)

This study investigated protease activities in a crude extract andin vitroexcretion/secretion (E/S) products ofPhilasterides dicentrarchi, a ciliate fish parasite causing economically significant losses in aquaculture. Gelatin/SDS–PAGE analysis (pH 4, reducing conditions) detected 7 bands with gelatinolytic activity (approximate molecular weights 30–63 kDa) in the crude extract. The banding pattern observed in analysis of E/S products was practically identical, except for 1 low-molecular-weight band detected in the crude extract but not in the E/S products. In assays with synthetic peptidep-nitroanilide substrates, the crude extract hydrolysed substrates characteristic of cysteine proteases, namely Z-Arg-Arg pNA, Bz-Phe-Val-Arg pNA and Z-Phe-Arg pNA. These activities were strongly inhibited by the cysteine protease inhibitor E-64 and by Ac-Leu-Val-Lys aldehyde, a potent inhibitor of cysteine proteases of the cathepsin B protease subfamily. The proteases present in the crude extract degraded both type-I collagen and haemoglobinin vitro, consistent with roles in tissue invasion and nutrition respectively. Again, E-64 completely (collagen) or markedly (haemoglobin) inhibited this degradation. Finally, the histolytic activity of the ciliate in turbot fibroblast monolayers was strongly reduced in the presence of E-64, confirming the importance of secreted cysteine proteinases in the biology ofPhilasterides dicentrarchi.

Anthelminthic and antiallergic activities of Mangifera indica L. stem bark components Vimang and mangiferin

This study investigated the antiallergic and anthelmintic properties of Vimang (an aqueous extract of Mangifera indica family stem bark) and mangiferin (the major polyphenol present in Vimang) administered orally to mice experimentally infected with the nematode, Trichinella spiralis. Treatment with Vimang or mangiferin (500 or 50 mg per kg body weight per day, respectively) throughout the parasite life cycle led to a significant decline in the number of parasite larvae encysted in the musculature; however, neither treatment was effective against adults in the gut. Treatment with Vimang or mangiferin likewise led to a significant decline in serum levels of specific anti-Trichinella IgE, throughout the parasite life cycle. Finally, oral treatment of rats with Vimang or mangiferin, daily for 50 days, inhibited mast cell degranulation as evaluated by the passive cutaneous anaphylaxis test (sensitization with infected mouse serum with a high IgE titre, then stimulation with the cytosolic fraction of T. spiralis muscle larvae). Since IgE plays a key role in the pathogenesis of allergic diseases, these results suggest that Vimang and mangiferin may be useful in the treatment of diseases of this type.

Mangifera indicaL. extract (Vimang) and mangiferin modulate mouse humoral immune responses

The present study investigated the effects of orally administered Vimang (an aqueous extract of Mangifera indica) and mangiferin (the major polyphenol present in Vimang) on mouse antibody responses induced by inoculation with spores of microsporidian parasites. Inoculation induced specific antibody production with an exponential timecourse, peaking after about one month. Vimang significantly inhibited this antibody production from about three weeks post-inoculation, and most markedly by four weeks post-inoculation; by contrast, mangiferin had no significant effect. Determination of Ig isotypes showed that the IgM to IgG switch began about four weeks post-inoculation, with IgG2a predominating. Vimang significantly inhibited IgG production, but had no effect on IgM. Mangiferin did no affect either IgM or IgG2a, but significantly enhanced production of IgG1 and IgG2b. Neither Vimang nor mangiferin enhanced specific antibody secretion by splenic plasma cells from mice inoculated with microsporidian spores, whether administered in vivo before serum extraction or in vitro to the culture medium. Inoculation with spores induced splenomegaly, which was significantly reduced by Vimang and significantly enhanced by mangiferin. These results suggest that components of Mangifera indica extracts may be of potential value for modulating the humoral response in different immunopathological disorders.

Heterogeneity and immunogenicity of the Trichinella TSL-1 antigen gp53

This study investigates the heterogeneity and immunogenicity of the Trichinella TSL-1 antigen gp53. Western blotting analysis of several Trichinella isolates with the gp53-specific monoclonal antibodies (mAbs) US5 and US9, produced in Btkxid mice, revealed that gp53 from the species T. britovi, T. murrelli and genotype T8 had higher MW (60 kDa) than gp53 from T. spiralis, T. nelsoni and genotype T6 (53 kDa) and from T. nativa (55 kDa). mAb US5 reacted only with gp53 from T. spiralis. Experiments including immunoassays of gp53 binding by sera from T. spiralis-infected mice, in the presence of different potential inhibitors (recombinant gp53, US5, T. britovi-crude larval extract (CLE), and CLE N- and O-glycans), indicate (i) that gp53 from T. spiralis bears specific epitopes that induce antibody formation during infection; (ii) that the protein epitopes of gp53 are much more important (76 or 68% of total antibody reactivity in BALB/c and Swiss CD-1 mice, respectively) than the corresponding glycan epitopes including tyvelose (11 or 32% of total reactivity) for the induction of anti-gp53 circulating antibodies; and (iii) that the species-specific epitopes present on gp53 are differentially recognized in different mouse strains. Whereas in BALB/c mice US5- and non-US5-recognized species-specific epitopes on gp53 bind about 84% of circulating antibodies on day 80 post-infection, this percentage was only 38% in Swiss CD-1 mice. These data on the antigenicity of gp53 contrast with data for Trichinella CLE antigens, in that most circulating antibodies reactive with CLE antigens recognized tyvelose-containing epitopes (57% and 58% of circulating antibodies in BALB/c and Swiss CD-1 mice, respectively). Together these results demonstrate that gp53 is recognized during infection but is antigenically different from other Trichinella TSL-1 antigens.

Philasterides dicentrarchi (Ciliophora:Scuticociliatida) expresses surface immobilization antigens that probably induce protective immune responses in turbot

Philasterides dicentrarchi is a histophagous ciliate causing systemic scuticociliatosis in cultured turbot. This study demonstrates that turbot which survive this disease have serum antibodies that recognize ciliary antigens of this ciliate in ELISA and immobilize/agglutinate the ciliate in vitro. Mouse sera raised against ciliary antigens and integral membrane proteins are likewise capable of immobilizing/agglutinating the ciliates, indicating that P. dicentrarchi, like other ciliates, expresses surface immobilization antigens. Furthermore, the antigen agglutinating reaction induces the parasite to shed its surface antigens rapidly, replacing them with others with different specific serology. This antigen shedding and variation response is similar to that detected in other protozoan parasites. Immunization of turbot with ciliate lysate plus adjuvant or with formalin-fixed ciliates induced synthesis of agglutinating antibodies and conferred a degree of protection against challenge infection, suggesting that the response to surface antigens may play an important role in defence against this pathogen, SDS-PAGE and immunoblotting studies indicated the existence of a predominant polypeptide of about 38 kDa in the ciliary antigen and membrane protein fractions, and this may be the principal surface antigen of P. dicentrarchi.

Mouse antibody response to a microsporidian parasite following inoculation with a gene coding for parasite ribosomal RNA

This study found that a plasmid construct encoding the small-subunit ribosomal RNA (SSUrRNA) of the microsporidian Microgemma caulleryi generates a humoral response upon intramuscular inoculation in mice. The plasmid used was pCMV, following preliminary trials indicating efficient beta-galactosidase gene expression in mouse muscle cells transfected with pCMV/beta-Gal. The antibodies produced after inoculation with pCMV/SSUDNA recognized parasite spore antigens and reached maximum levels at 30 days postinoculation, subsequently remaining stable for at least 120 days. Due to the highly conserved sequence of the SSUrDNA in different microsporidian species, these results open up interesting prospects for broad-spectrum vaccination.

Modulation of rat macrophage function by the Mangifera indica L. extracts Vimang and mangiferin

Vimang is an aqueous extract of Mangiferia indica L., traditionally used in Cuba as an anti-inflammatory, analgesic and antioxidant. In the present study, we investigated the effects of Vimang and of mangiferin (a C-glucosylxanthone present in the extract) on rat macrophage functions including phagocytic activity and the respiratory burst. Both Vimang and mangiferin showed inhibitory effects on macrophage activity: (a) intraperitoneal doses of only 50-250 mg/kg markedly reduced the number of macrophages in peritoneal exudate following intraperitoneal injection of thioglycollate 5 days previously (though there was no significant effect on the proportion of macrophages in the peritoneal-exudate cell population); (b) in vitro concentrations of 0.1-100 microg/ml reduced the phagocytosis of yeasts cells by resident peritoneal and thioglycollate-elicited macrophages; (c) in vitro concentrations of 1-50 microg/ml reduced nitric oxide (NO) production by thioglycollate-elicited macrophages stimulated in vitro with lipopolysaccharide (LPS) and IFNgamma; and (d) in vitro concentrations of 1-50 microg/ml reduced the extracellular production of reactive oxygen species (ROS) by resident and thioglycollate-elicited macrophages stimulated in vitro with phorbol myristate acetate (PMA). These results suggest that components of Vimang, including the polyphenol mangiferin, have depressor effects on the phagocytic and ROS production activities of rat macrophages and, thus, that they may be of value in the treatment of diseases of immunopathological origin characterized by the hyperactivation of phagocytic cells such as certain autoimmune disorders.

Non-isotopic detection of Tetramicra brevifilum (Microspora) DNA in turbot tissues

A non-isotopic in situ hybridization (ISH) method was developed for detection of Tetramicra brevifilum, a commercially important parasite in farmed turbot Scophthalmus maximus. The probe relies on sequences from the small-subunit rRNA gene (SSUrDNA) of Tetramicra brevifilum and was obtained by polymerase chain reaction then labeled with digoxigenin. The results obtained demonstrate that the probe hybridizes well with genomic DNA of the spores; thus, it is an effective method for detecting multiorgan infections of turbot by T. brevifilum.

Effect of Tetramicra brevifilum (Microspora) infection on respiratory-burst responses of turbot (Scophthalmus maximus L.) phagocytes

In vitro assays were performed to investigate microsporidian-induced intracellular and extracellular production of reactive oxygen species (ROS) by peritoneal-exudate adherent (PEA) cells from turbot. ROS production was quantified using the fluorescent reagents OxyBURST Green H2HFF BSA (extracellular) and OxyBURST Green H2DCFDA succinimidyl ester (intracellular). Five days before assay, the cells had been elicited in vivo by intraperitoneal injection of sodium thioglycollate or spores of Tetramicra brevifilum. Elicitation with spores led to a marked increase in the proportion of neutrophils among PEA cells. PEA cells from normal turbot showed considerable extracellular and intracellular ROS production in response to microsporidian spores. By contrast, PEA cells from microsporidian-infected turbot showed considerably reduced extracellular and intracellular ROS production in response to microsporidian spores. Extracellular ROS production was affected by the addition of infected turbot serum to the assay medium, regardless of whether the PEA cells had been obtained from normal or infected fish. The presence of microsporidian-infected turbot serum significantly reduced intracellular ROS production by PEA cells elicited with microsporidian spores. These results suggest that (a) microsporidian spores partially suppress the repiratory-burst response of turbot phagocytes; and (b) infected turbot serum contains substances capable of modulating the respiratory-burst response of turbot phagocytes to microsporidian spores.

Natural antibodies to nematode biotinyl-enzymes in human sera

Biotinyl-enzymes are conservative molecules present in helminths, as well as in other animals, bacteria and plants. They have recently been found to be antigenic in mice, and a potential source of cross-reactivity among helminths. This study investigated the presence in human sera of antibodies reactive with biotinyl-enzymes from the nematodes Anisakis simplex, Toxocara canis and Ascaris suum. Biotinyl-enzymes from all these nematodes were recognized by IgG1 antibodies in sera from healthy subjects and from Anisakis-free patients infected with other parasites. Interestingly, IgE antibodies reactive with Anisakis simplex biotinyl-enzymes were present in about one third of the sera from Anisakis-free patients infected with other parasites. Our results also demonstrate that the anti-BE IgG1 and IgE antibodies present in the sera of Anisakis-free subjects are cross-reactive among helminths. We conclude that biotinyl-enzymes from nematodes are recognized by natural human antibodies, although Anisakis biotinyl-enzymes do not seem to be the cause of sensitization. Since sera from the Anisakis-free population also present these antibodies, as-yet unidentified factors (dietary components, intestinal inflammation and/or the presence of parasites) may contribute to the induction of anti-BE antibody background.

Prevalence of and risk factors for IgE sensitization to Anisakis simplex in a Spanish population

BACKGROUND

The number of allergic reactions to A. simplex reported in Spain has increased dramatically in the last decade. Nevertheless, there have been no studies of the prevalence of and possible risk factors for IgE sensitization to this parasite, possibly because suitably specific diagnostic methods have only recently become available. The objective was to investigate the prevalence of and risk factors for IgE sensitization to A. simplex in Galicia, a region of northwestern Spain with a population of about 3 million and high average fish consumption (78.5 g/person per day).

METHODS

The study was performed with a random sample of 2801 healthy blood donors distributed in 53 geographic areas, proportional to the density of donors. IgE sensitization to A. simplex was tested by a capture ELISA method that has proved to be the most specific method currently available.

RESULTS

The results showed a total of only 12 positive subjects, of whom five also showed IgG1 sensitization. All positive subjects and 101 randomly selected seronegative subjects were then included in a case-control study of risk factors for sensitization to A. simplex, based on a telephone interview about fish consumption (especially raw and undercooked fish). All seropositive subjects (but only 25% of seronegative subjects) reported consumption of undercooked fish or homemade raw-fish products.

CONCLUSIONS

Our results strongly suggest that sensitization to A. simplex is caused only by live larvae, and not by allergens contained in fish tissues, and that ingestion of homemade boquerones (anchovies [Engraulis encrasicholus] in vinegar), and to a much lesser extent of undercooked fish, are the main risk factors for IgE sensitization to Anisakis in this region.

Characterization of two monoclonal antibodies raised in Btk(xid) mice that recognize phosphorylcholine-bearing antigens from Trichinella and other helminths

This study investigated the binding properties of two monoclonal antibodies (mAbs US1 and US2) raised in (CBA/n x BALB/c)F1 (NBF1) Btk(xid) male mice. Both mAbs show unusual specificity for phosphorylcholine (PC)-containing TSL4 antigens of Trichinella. Specifically, and in contrast to mAbs raised in normal mice, US1 and US2 mAbs do not bind to artificial PC-protein conjugates and are not inhibited by either free PC or NPPC, although US2 was partially inhibited by NPPC at high concentration (10(-2) M). However, both mAbs completely abrogate the binding to Trichinella antigens of other anti-PC mAbs (e.g. BH8 and Mab-2). These results suggest that both US1 and US2 recognize complex PC-containing epitopes. The patterns of recognition of PC-bearing antigens from different helminths by US1, US2, Mab-2 and BH8 were broadly correlated with phylogenetic proximity. The closest similarities were observed between the members of the Trichinelloidea superfamily (Trichinella spiralis and Trichuris muris) and among the ascarids (Toxocara canis, Anisakis simplex, Hysterothylacium aduncum and Ascaris lumbricoides). However, US1 did not react with the filarial nematode Onchocerca volvulus and reacted only weakly with Onchocerca gibsoni, while US2 reacted only weakly with both species. Only BH8 recognized PC-bearing antigens from the trematode Fasciola hepatica and the cestode Bothriocephalus scorpii. These results suggest that PC is attached to identical or very similar structures on most different nematode species, although major differences exist with respect to helminth species from groups such as the trematodes and cestodes that are phylogenetically distant from the nematodes.

Unusual electrophoretic patterns for phosphoglucomutase and fumarase in a population of Lecithochirium rufoviride (Trematoda: Hemiuridae), a parasite of Conger conger

Electrophoretic analyses of phosphoglucomutase (PGM) and fumarase (FH) in a population of Lecithochirium rufoviride parasitizing Conger conger, revealed 2 independent activity zones for each enzyme on starch gel electrophoresis. However, some individuals exhibited only 1 activity zone for 1 or both enzymes. The banding patterns observed strongly suggest that (1) PGM is coded by 2 polymorphic loci, Pgm-1 (expressed in all individuals) with allelic frequencies not significantly different from those expected under Hardy-Weinberg equilibrium, and Pgm-2 (expressed in a subset of individuals); and (2) FH is coded by 2 loci, Fh-2 (monomorphic and expressed in all individuals) and Fh-1 (expressed in a subset of individuals). A high degree of concordance (88.75%) was observed between the expression and nonexpression of Pgm-2 and Fh-1. The most likely explanations for these findings are either variation in enzyme expression with developmental stage or the presence of null alleles at high frequencies in the population.

A comparison of antigenic peptides in muscle larvae of several Trichinella species by two-dimensional western-blot analysis with monoclonal antibodies

The antigens recognised by mAb US5 specific to 53 kDa glycoprotein (gp 53) in T. spiralis L-1 muscle larvae (TSL1) antigens, mAb US9 specific to gp 53 in TSL1 from all encapsulated species and mAb US4 specific to a tyvelose containing tetrasaccharide present in TSL1, were investigated in crude extracts from muscle larvae of T. spiralis, T. nativa and T. britovi by 2D-electrophoresis and western-blot. At least four proteins of different p1 were recognised by mAb US5 on T. spiralis antigens. Recognition profile of mAb US9 on T. spiralis antigens exhibited some variation with regard to that of the US5. Polymorphism was apparent in gp 53. High reactivity was shown by the mAb US4 with the three species.

Possible presence of common tyvelose-containing glycans in Trichinella L1 larvae and embryonated eggs of several nematodes

A monoclonal antibody (mAb US4) recognising an epitope containing tyvelose within the T. spiralis L-1 muscle larvae (TSL-1) antigens was tested in western-blot against various antigenic preparations from different stages of the following nematodes: T. spiralis (L1, adult), T. muris (egg, L1, L3, adult), Ascaris suum (egg, adult), Toxocara canis (egg, adult), Anisakis simplex (L3) and Haemochus contortus (egg). Positive reaction was present in antigen preparations from L1 larvae of T. spiralis and T. muris and from embryonated eggs of T. muris, A. seum, T. canis and H. contortus.

Respiratory burst responses of rat macrophages to microsporidian spores

This study investigated the respiratory burst responses of rat resident peritoneal macrophages and of peritoneal macrophages stimulated 5 days previously with viable spores of the fish infecting microsporidian Microgemma caulleryi. Nitric oxide production by resident macrophages and prestimulated macrophages in response to viable microsporidian spores was significantly lower than in response to Escherichia coli lipopolysaccharide (LPS) (nitrite concentration in medium 57 +/- 1 microM for resident macrophages stimulated with LPS versus 31 +/- 1 microM for resident macrophages stimulated with microsporidian spores and 36 +/- 4 microM for M. caulleryi prestimulated macrophages; P < 0.05). Extracellular release of reactive oxygen species (ROS) by resident macrophages in response to microsporidian spores was similar to that in response to Kluyveromyces lactis yeast cells and to that in response to phorbol myristate (a stimulator of protein C kinase). Intracellular ROS production by resident macrophages in response to microsporidian spores was similar to that produced in response to yeast cells. Both extracellular ROS production and intracellular ROS production (in response to all stimuli) were significantly lower after in vivo prestimulation of macrophages with microsporidian spores. These results demonstrate that microsporidian spores of species other than those that habitually infect mammals are capable of modulating the respiratory burst of rat peritoneal macrophages. Such modulation may contribute to avoidance by the microsporidian of cytotoxic responses associated with the respiratory burst.

Usefulness of currently available methods for the diagnosis of Anisakis simplex allergy

BACKGROUND

Serodiagnosis of anisakiosis and Anisakis allergy is difficult since many Anisakis antigens show cross-reactivity complications. In the present study, we assess the usefulness of the major immunologic methods currently available for the diagnosis of Anisakis allergy.

METHODS

Four tests (skin prick test, CAP-FEIA system, Western blotting, and an antigen-capture ELISA using O-deglycosylated antigen bound by the monoclonal antibody UA3) were applied to Anisakis-free subjects and subjects with confirmed Anisakis allergy.

RESULTS

The skin prick test, CAP-FEIA, and the antigen-capture ELISA identified Anisakis allergy sera with 100% sensitivity, while Western blotting showed 96%/ sensitivity. The antigen-capture ELISA also showed 100% specificity, but CAP-FEIA showed a specificity of only 50%. In Western blotting, none of the bands detected were specific for either Anisakis-free or Anisakis allergy subjects. The skin prick test was not applied to the Anisakis-free subjects, so its specificity could not be determined.

CONCLUSIONS

On the basis of these results, we suggest that the most appropriate procedure for diagnosis of Anisakis allergy suspected on clinical grounds is the antigen-capture ELISA using UA3, or, alternatively, a preliminary skin prick test with a positive result subsequently confirmed by UA3-ELISA.

Non-specific responses of turbot (Scophthalmus maximus L.) adherent cells to microsporidian spores

We investigated non-specific responses of turbot spleen- and pronephros-resident adherent cells to spores of fish microsporidians, and the effects of the glucocorticoid dexamethasone (DX) on these responses. On average, 65% of adherent cells from the spleen and pronephros showed esterase activity (as characteristic of macrophages); 32% showed peroxidase activity (as characteristic of neutrophils), and 19% of peroxidase-positive cells were capable of phagocytosing microsporidian spores. A significantly higher proportion of adherent cells showed phagocytic activity when viable spores were the target than when non-viable spores were the target. Microsporidian spores stimulated adherent cells to produce reactive oxygen and nitrogen intermediates (ROIs and RNIs), though less effectively than the other stimulants tested. Adherent cells exposed to viable spores produced significantly less intracellular superoxide than adherent cells exposed to non-viable spores. Daily injection of fish with DX over 6 days significantly inhibited both phagocytosis of microsporidian spores and spore-induced ROI production, and similar effects were observed when adherent cells were exposed to DX in vitro.

O-glycans as a source of cross-reactivity in determinations of human serum antibodies to Anisakis simplex antigens

BACKGROUND

Anisakis simplex is a seafood-borne parasite that may both infect humans and cause allergy. Serodiagnosis of anisakiasis and allergy caused by this nematode is difficult since most Anisakis antigens show cross-reactivity problems.

OBJECTIVE

To analyse the possible role of sugar epitopes contained in Anisakis simplex antigens as causes of false-positive results in serodiagnostic assays.

METHODS

The antigens UA2R and UA3R recognized by two anti-Anisakis monoclonal antibodies were used in this study. Capture ELISA techniques were used to compare the reactivities with native or O-deglycosylated antigens of sera from Anisakis-free children (most of them infected by several other parasites) and from Anisakis allergy patients. O-deglycosylation was done by mild alkali treatment with NaOH. SDS-PAGE and immunoblotting were used to characterize the effects of NaOH or N-glycanase F treatment on UA3R.

RESULTS

Native UA2R was recognized by IgG1 and IgM antibodies in the sera of both Anisakis-free subjects and allergy patients. Native UA3R was recognized by most sera from allergy patients (92% considering immunoglobulin (Ig) G1, 100% considering IgE), but also by a significant proportion of sera from Anisakis-free subjects (36% considering IgG1, 14% considering IgE). O-deglycosylation of UA3R greatly improved specificity: none of the sera from Anisakis-free patients showed either IgG1 or IgE reactivity with O-deglycosylated UA3R, while the proportion of sera from allergy patients showing IgE reactivity with this antigen was practically unaffected. O-deglycosylation of UA2R did not improve the specificity of assays using this antigen. Our results also show that the protein core of glycoproteins may be altered by even very mild alkali treatment, depending on the nature of the protein.

CONCLUSION

Native glycoproteins of A. simplex should not be used for diagnostic purposes. O-deglycosylated UA3R seems to be an excellent candidate for use as target antigen in the serodiagnosis of anisakiasis and A. simplex allergy.

RFLP analysis of PCR-amplified small subunit ribosomal DNA of three fish microsporidian species

The phylogenetic relationships of the microsporidian species Microgemma caulleryi, Pleistophora finisterrensis and Tetramicra brevifilum were investigated on the basis of restriction fragment length polymorphism (RFLP) analysis of PCR-amplified small-subunit rDNA (SSUrDNA). Using PCR primers specific for microsporidian SSUrDNA, a single product was obtained from each species, and heteroduplex analysis indicated a high degree of sequence homology among the 3 products. In RFLP analysis of the PCR-amplified SSUrDNA, the enzymes AluI and DdeI gave restriction patterns that differed among all 3 species. Phylogenetic analysis using restriction patterns as differential characters indicated that Microgemma caulleryi and Tetramicra brevifilum are more closely related to each other than to Pleistophora finisterrensis.

DNA probes for detection of the fish microsporidians Microgemma caulleryi and Tetramicra brevifilum

DNA probes were developed for the detection and identification of 2 microsporidian parasites of marine fishes, Microgemma caulleryi (infecting the liver of the greater sand-eel, Hyperoplus lanceolatus) and Tetramicra brevifilum (infecting muscle, intestine and liver of the turbot, Scophthalmus maximus, a commercially important species). The probe-development procedure used is fast and straightforward, and readily applicable to the development of probes for other microsporidian species. First, genomic DNA of microsporidian spores was isolated and digested with the restriction enzyme Hind III. The fragments obtained were ligated into the vector pBluescript SK(+) and cloned in Escherichia coli. Appropriate inserts were identified and then amplified by PCR, using primers specific for regions adjacent to the Hind III restriction site in the vector sequence (and thus avoiding the need to develop primers specific for the inserts themselves). The copies were labelled with digoxigenin, for subsequent use as probes, during PCR itself. The specificity of candidate probes was tested in dot-blot hybridization assays, with the target DNA being (a) genomic DNA of the microsporidian from which the probe had been obtained, or of another species, (b) the corresponding genomic DNA in the phagemid, or (c) DNA from the corresponding host tissue. These assays identified a ca 1180 bp probe for M. caulleryi, denominated C38, and a ca 1363 bp probe for T. brevifilum, denominated F9. Similar assays designed to assess sensitivity indicated that F9 showed detectable binding to as little as 500 ng of T. brevifilum genomic DNA, and C38 to as little as 125 ng of M. caulleryi DNA; these results were obtained with detection of DIG by enzyme immunoassay (i.e. using a phosphatase-coupled anti-DIG antibody), and could no doubt be improved if a radioactive labelling and detection system were used. The probes developed in this study will greatly facilitate detection and identification of M. caulleryi and T. brevifilum in fish tissues, and may prove useful for identifying possible intermediate hosts used by these species.

Human immunoglobulin isotype profiles produced in response to antigens recognized by monoclonal antibodies specific to Anisakis simplex

BACKGROUND

Anisakis simplex is a medically important pathogen which not only causes anisakiasis but may provoke allergy reactions, ranging from mild urticaria to anaphylactic shock.

OBJECTIVE

To investigate anti-Anisakis isotype profiles in anisakiasis and Anisakis allergy patients.

METHODS

Capture ELISA techniques were used to investigate the isotype profiles of antibodies specific for two defined Anisakis simplex antigens, in serum from Japanese patients with confirmed anisakiasis and from Spanish patients with allergy to Anisakis. The antigens were 'UA2R antigens' (two proteins with MW of 48 and 67 kDa, recognized by our monoclonal antibody UA2) and 'UA3R antigens' (two proteins with MW of 139 and 154 kDa, recognized by our monoclonal antibody UA3).

RESULTS

Considering IgG, the two most frequent isotypes in the response to the UA2R antigens were IgG1 and IgG2, with IgG4 detected in only one case; in response to the UA3R antigens, by contrast, the two most frequent isotypes were IgG1 and IgG4 (though IgG2 remained reasonably frequent). As regards potential utility for serodiagnosis, 95% of the Japanese anisakiasis patients and 84% of the allergy patients showed detectable IgG1 antibodies to the UA3R antigens. Furthermore, all allergy patients showed IgE antibodies to these antigens.

CONCLUSION

Anisakis simplex contains antigens that induce responses which are differentially regulated. Because of their immunogenicity, immunodominance and allergenic nature, we consider that the 139/154-kDa antigens recognized by our MoAb UA3 are good candidates for use in tests for the diagnosis of anisakiasis and of the allergy caused by this parasite.

Analysis of the antigenicity in mice of biotinyl enzymes from Anisakis simplex and other nematodes

We analyzed the antigenicity of biotinyl enzymes contained in somatic extracts from Anisakis simplex and other parasite nematodes and show in this report that these molecules are an important source of cross-reactivity problems among these nematodes. Cross-reactivity was most pronounced among members of the superfamily Ascaridoidea. These results suggest that the presence of biotinyl enzymes in whole somatic extracts of A. simplex and other parasites may make serodiagnostic assays based on this kind of antigenic preparation unreliable.

Characterization by enzyme electrophoresis of specimens of the genus Helicometra (Trematoda, Opecoelidae) from fish caught off the coast of northwest Spain

Species within the genus Helicometra are difficult to distinguish on morphological grounds alone, and are best discriminated with the aid of biochemical techniques. In the work reported here, the electrophoretic mobility of malate dehydrogenase isoenzyme of the Mdh-1 locus was used to characterize 375 individuals of Helicometra obtained from various teleost species (Anguilla anguilla, Conger conger, Gobius niger or Ciliata mustela) caught off the coast of northwest Spain. The results suggest that all specimens belong to only one species, probably H. fasciata. Observed genotype frequencies did not differ from those expected under the assumptions of Hardy-Weinberg equilibrium, even when the genic frequencies differ considerably respecting a Mediterranean population.

Carrier-dependent suppression of the anti-phosphorylcholine plaque-forming cell response in Trichinella-infected mice is mediated by anti-hapten IgG1 antibodies

In normal mice, the phosphorylcholine(PC)-bearing Trichinella spiralis antigen FCp induces PC-specific IgM antibodies. Infection with T. spiralis appears to suppress this response, without affecting the production of anti-PC antibodies in response to other PC-bearing antigens; the suppression can thus be considered carrier-dependent. Previous work in our laboratory has indicated that the observed suppression is due to a soluble factor present in the serum of infected mice. In the work reported here, we investigated the identity of this factor. After in vitro stimulation with FCp, spleen cells from FCp-primed infected mice showed a stronger anti-PC IgM response than spleen cells from FCp-primed uninfected mice, confirming that cell memory for FCp is unimpaired by infection. Passive transfer of serum from infected mice to normal recipients, followed by immunization of recipients with FCp or another thymus-dependent or thymus-independent PC-bearing antigen, confirmed that the suppressive agent is soluble and that its activity is carrier-dependent. The suppressive agent was retained by immunoaffinity chromatography with PC or rabbit anti-mouse Ig as ligand, showing that it is a PC-specific Ig. Gel filtration of the fractions retained by PC-immunoaffinity, and subsequent identification of Ig isotypes by an ELISA-based procedure, indicated that the suppressive Igs are of the IgG1 isotype. These findings may be relevant for understanding antibody-mediated down-regulation of the immune response.

Monoclonal antibodies against diagnostic Anisakis simplex antigens

Five monoclonal antibodies (UA2, UA3, UA5, UA6, and UA8) specific for Anisakis simplex are described. All are IgG1/kappa monoclonal antibodies, except for UA2, which is an antibody IgM/kappa. The molecular weights of the major components recognized in immunoblotting are 48 and 67 kDa (UA2); 139 kDa (UA3 and UA5; same epitope); 35, 38, and 139 kDa (UA6); and 205 kDa (UA8). UA2 was the only monoclonal antibody to recognize both components of an excretion-secretion antigen preparation and antigens in the excretory cell and esophageal glands of third-stage A. simplex larvae; antigens in the excretory cell were also recognized by UA3 and UA6. Cross-reactivity studies using a hyperimmune polyclonal rabbit serum reacting with various ascaridoid nematodes indicated that the antigens captured by our monoclonal antibodies were specific for A. simplex. Finally, comparative studies of our monoclonal antibodies and An2 (the only monoclonal antibody currently available for serodiagnosis of human anisakiasis), based on the calculation of multiples of normal activity for human anisakiasis sera, indicated that our monoclonal antibodies (and particularly UA3) recognized antigens that are good candidates for serodiagnostic purposes.

Effects of chitinolytic and proteolytic enzymes on in vitro phagocytosis of microsporidians by spleen macrophages of turbot, Scophthalmus maximus L

The serum of many teleosts, including turbot, contains chitinolytic and proteolytic enzymes. In the present study, the possible role of these enzymes in nonspecific immune responses to microsporidian infection was investigated. The rate of phagocytosis of Glugea caulleryi spores by turbot splenic macrophages was significantly reduced after pretreatment of spores with proteolytic or chitinolytic enzymes, suggesting that alteration of surface glycoproteins affects spore recognition. However, intracellular superoxide production by macrophages was significantly higher after stimulation with protease-treated spores, or with untreated spores plus normal turbot serum (NTS), than after stimulation with untreated spores in the absence of NTS. These results support the view that the chitinolytic and proteolytic activities in teleost serum may play a role in defence against microsporidian infection.

The humoral immune response of turbot, Scophthalmus maximus L., to spore-surface antigens of microsporidian parasites

Experiments based on enzyme-linked immunosorbent assay (ELISA) revealed considerable antigenic homology in turbot between two species of microsporidian, Tetramicra brevifilum (a parasite of the turbot, Scophthalmus maximus) and Glugea caulleryi (a parasite of the lesser sand-eel, Ammodytes tobianus). We next investigated whether G. caulleryi is able to suppress the turbot immune response. Intraperitoneal inoculation of turbot with G. caulleryi spores (whether heat-killed or viable) did not suppress the humoral immune response to injection of G. caulleryi spores plus adjuvant 15 days later; in fact, specific serum antibody levels (as revealed by ELISA) reached maximum levels by about Day 30 post re-exposure. Similar results were obtained with cellular enzyme-linked immunosorbent assay: 15 days after injection with G. caulleryi spores plus adjuvant, specific antibody secretion rate was higher in turbot which had been pre-exposed to G. caulleryi spores than in turbot which had not been pre-exposed.

Free and bound biotin molecules in helminths: a source of artifacts for avidin biotin-based immunoassays

The avidin-biotin molecular recognition system is widely used in parasite immunology. However, the presence of biotin and/or biotin-containing molecules (BCMs) in samples may lead to erroneous results. In the work reported herein we investigated the extent to which biotin and BCMs present in helminth extracts may interfere in avidin/biotin-based immunoassays and developed an enzyme-linked immunosorbent assay (ELISA) for quantification of these components. In avidin-based ELISA using antinematode monoclonal antibodies, an extract of the nematode Anisakis simplex showed very high background reactivity due to biotin/BCMs, whereas the background reactivity in an extract of the nematode Trichinella spiralis was negligible. To investigate interspecies differences further, we performed Western-blot analyses (with avidin as the detector) of extracts from seven nematodes (A. simplex, Ascaris suum, Toxocara canis, Hysterothylacium aduncum, T. spiralis, and Trichuris muris) and the cestode Bothriocephalus scorpii. Even within superfamilies there was considerable variation in the banding patterns obtained. The above-mentioned results confirm that biotin and BCMs may be a significant source of interference in ELISA and immunoblotting, two of the techniques most widely used in parasitological immunodiagnosis. A competition ELISA designed to allow accurate quantification of biotin and BCMs in helminth extracts likewise indicated very considerable interspecies variation. Both A. simplex and H. aduncum had very high biotin/BCM contents. Microdialysis of extracts in the presence of dimethylsulfoxide to remove free biotin prior to ELISA indicated that the high biotin/BCM content of the H. aduncum extract (but not the A. simplex extract) was very largely due to free biotin. Taken together, these results indicate that extreme caution should be exercised in the use of avidin/biotin-based immunoassays for the detection of helminth antigens and that in many cases it may be better to use an alternative recognition system.

The role of opsonization by antibody and complement in in vitro phagocytosis of microsporidian parasites by turbot spleen cells

We investigated the role played by opsonization by antibody and complement in in vitro phagocytosis of microsporidian spores by turbot adherent phagocytes. Most turbot adherent cells displaying phagocytic activity are probably macrophages. Phagocytosis of yeast cells and polystyrene beads was greatly enhanced in the presence of both the Ig and the non-Ig (i.e. complement-containing) fractions of normal turbot serum, but phagocytosis of Glugea caulleryi or Tetramicra brevifilum spores was not affected by either fraction. Neither anti-G. caulleryi immune serum, nor anti-T. brevifilum immune serum (which cross-reacted considerably with G. caulleryi antigens), enhanced phagocytosis of G. caulleryi spores. Finally, spores treated with sodium m-periodate (to modify the structure of surface-borne sugars) were less effectively ingested than untreated spores, suggesting that phagocytosis of microsporidian spores involves recognition of such sugars by the phagocytic cell. The results of this study support the hypothesis that microsporidian parasites of fish in some way modulate the host phagocytic responses.

Antigenic cross-reactivity in mice between third-stage larvae of Anisakis simplex and other nematodes

We used ELISA and immunoblotting to investigate antigenic cross-reactivity in mice between third-stage larvae of Anisakis simplex and five other nematodes: the ascaridoids Ascaris suum, Toxocara canis and Hysterothylacium aduncum, and the nonascaridoids Trichinella spiralis and Trichuris muris. Two sera were raised against each species (including A. simplex, but excluding A. suum), by infection or by immunization with somatic antigens. Serum against A. suum was raised by immunization only. The reactivities of each serum with A. simplex somatic antigens (SA), excretion-secretion antigens (ES), pseudocoelomic fluid antigens (PF) and cuticular antigens (CA) were investigated. The results of ELISA indicated high antigenic cross-reactivity between A. simplex and the remaining ascaridoid nematodes, confirming that there is extensive antigenic similarity within this group of nematode parasites. Immunoblotting again confirmed the high degree of cross-reactivity between the SA of A. simplex and SAs of the other ascaridoids, although several A. simplex SA components in the 11-18 kDA range were only recognized by sera from mice infected with A. simplex. In addition, two A. simplex PF components of 22 and 27 kDA, were recognized only by sera from mice infected with, or immunized with the SA of, A. simplex. Finally, the anti-phosphorylcholine monoclonal antibody BH8 recognized only a small number of A. simplex antigens, indicating that phosphorylcholine epitopes are not significant contributors to the observed cross-reactivity with the other nematodes.

The humoral immune response of turbot to recently isolated pathogenic Enterococcus strains. Cross-reactivity with other Gram-positive bacteria

An Enterococcus sp. causing severe mortalities among farmed turbot (Scophthalmus maximus) has recently been detected in northwest Spain. We found that specific turbot serum antibodies raised against isolate RA-99.1 of the new pathogen by intraperitoneal immunization, did not cross react in enzyme-linked immunosorbent assay (ELISA) with other enterococcal or non-enterococcal Gram-positive bacteria. In immunoblotting, antibodies raised against strain RA-99.1 recognized the same components in the homologous total soluble antigen preparation (TSA) as in TSA of two other isolates of the pathogen obtained from different farms. Anti-RA-99.1 serum also recognized some components of the TSA of several other Gram-positive bacteria. Immunogold labelling indicated that the antigens which provoke the humoral immune response to this pathogen are located mainly on the bacterial surface.

Anisakis simplex: stage-specific antigens recognized by mice

To investigate antigenic differences between the developmental stages of Anisakis simplex, somatic, excretion-secretion and detergent-solubilized surface antigen preparations of third- and fourth-stage A. simplex larvae, and a somatic antigen preparation of adults, were characterized by SDS-PAGE and immunoblotting using mouse immune serum containing antibodies against the two larval stages. Excretion-secretion and surface antigen preparations from third-stage larvae behaved very differently from those of fourth-stage larvae, in both SDS-PAGE and immunoblotting; this suggests that certain excretion-secretion and surface antigens are highly stage-specific. By contrast, somatic components of third- and fourth-stage larvae were found to have very similar banding patterns, suggesting conservation of these components during the development of the parasite in mice. The SDS-PAGE and immunoblotting results for adult somatic components seem to support this hypothesis.

A sandwich immunoassay to quantify low levels of turbot (Scophthalmus maximus) immunoglobulins

We have developed an enzyme-linked immunosorbent assay for the quantification of turbot (Scophthalmus maximus) immunoglobulin (Ig). The capture antibody is a rabbit polyclonal antiserum to turbot Ig, and the detector antibody a monoclonal antibody (UR3) to the turbot Ig heavy chain. Both antibodies bind nearly 100% of turbot Ig. The assay allows detection of turbot Ig in serum at concentrations as low as 0.16 micrograms ml-1 and takes less than 4 h. Precision is satisfactory, with intra-assay coefficients of variation (CVs) ranging from 2.1 to 16.6%, and inter-assay CVs ranging from 5.8 to 24.6%. We used the assay to determine Ig concentrations in the sera of healthy turbot of different weights. Mean serum Ig concentration was 3.35 +/- 0.74 mg ml-1 for fish weighing 15-25 g and 11.14 +/- 1.87 mg ml-1 for fish weighing 1000-2000 g.

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.

Glycans as targets for monoclonal antibodies that protect rats against Trichinella spiralis

We have investigated the role of glycans on Trichinella spiralis antigens in recognition by rat monoclonal antibodies (mAbs) which protect rat pups against challenge with the parasite. In pups born to infected dams or pups passively immunized with mAbs, antibodies eliminate a challenge dose from the intestine within hours ('rapid expulsion'). Because such dramatic protection can be afforded by mAbs, we have sought to characterize the parasite antigens they target. In this report we show that protective antibodies were unable to bind excretory/secretory (ES) antigens deglycosylated with trifluoromethanesulphonic acid (TFMS). In addition, oligosaccharides isolated from glycoproteins by alkaline hydrolysis or peptide: N glycosidase F (PNGase F) digestion were bound by protective, but not non-protective, mAbs. Glycans affinity purified with protective mAb 9D bound to all but one protective mAb. These antibodies have been shown previously to bind to the surfaces of intact larvae, indicating that the glycan is exposed on the parasite surface. Candidate glycans that may be involved in binding protective mAbs have unusual tri- and tetra-antennary structures with terminal tyvelose moieties (Reason et al., Glycobiology, 4, 000-000, 1994). Coating of the larval surface with such glycans may serve to protect the parasite and its secreted products from enzymatic attack as the parasite travels to and resides in its epithelial niche.

Molecular analysis of antigens targeted by protective antibodies in rapid expulsion of Trichinella spiralis

Rapid expulsion is a protective immune mechanism which eliminates as much as 99% of a challenge infection of Trichinella spiralis muscle larvae from the gastrointestinal tract of suckling rats. Protective monoclonal antibodies (mAbs) generated against larval excretory-secretory antigens (ESA) specifically recognize a 45-kDa glycoprotein, gp45, in addition to a distinct profile of other cross-reactive antigens that are also recognized by non-protective mAbs. Recent data indicate that protective mAbs recognize carbohydrate epitopes. To complement biochemical studies on the target(s) of rapid expulsion, we describe here the cloning and characterization of the cDNA, TspE1, which belongs to a multigene family and encodes several larval proteins in the 40-50-kDa range. A second cDNA, TspM6 encodes a 45-kDa antigen and is homologous to the published sequence of gp45. Anti-TspE1 antibodies detected antigens within beta- and gamma-stichocytes while anti-TspM6 antibodies detected antigens within alpha-stichocytes of the secretory organs of muscle larvae. Sequence analysis has provided no functional information on the encoded gene products. Neither recombinant antigen is recognized by the mAbs but native parasite molecules with peptide homology to both the TspE1 and TspM6 recombinant antigens bear the glycan recognized by the protective mAbs. These molecules are candidate targets in rapid expulsion.

Monoclonal antibodies to turbot (Scophthalmus maximus) immunoglobulins: characterization and applicability in immunoassays

Five monoclonal antibodies (mAbs) to immunoglobulins (Igs) of the turbot Scophthalmus maximus were produced and characterized. All the mAbs (denominated UR1, UR3, UR4, UR6 and UR7) are of isotype IgG1/kappa and show good anti-turbot Ig reactivity in enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Results of competitive ELISA and immunoblotting analysis indicate that these five mAbs react with at least three different epitopes on the turbot Ig H chain. Except in the case of UR1, reactivity with periodate-treated purified turbot Ig was much lower than with the untreated Ig, suggesting that carbohydrate residues are involved in epitope recognition. All the mAbs showed reactivity with sera from the closely related species Scophthalmus rhombus but not with sera from species of other flatfish genera. One of these mAbs (UR3) has been successfully applied for the detection of antibodies against Vibrio anguillarum in ELISA.