Detection of coproantibodies and faecal immune complexes in human trichinellosis

Early diagnosis of experimental Trichinella spiralis infection by nano-based enzyme-linked immunosorbent assay (nano-based ELISA)

Trichinellosis is a serious foodborne zoonotic disease. It is an important threat to public health all over the world. Although anti-Trichinella IgG detection is the most widely used method for diagnosis of trichinellosis, but there is an obvious window between clinical symptoms and positive serology. Gold nanoparticles (AuNPs) can be conjugated with antibodies affording them promising applications for bio-chemical detection. Herein, AuNPs-based ELISA was evaluated for the first time in the detection of Trichinella spiralis circulating antigen (CAg) for its potential as a diagnostic tool of experimental infection. Swiss Albino mice were orally inoculated with 100 muscle larvae/mouse. Animals were sacrificed 6, 8, 10, 12, 14, 16, 22 and 28 day-post infection (dpi). Blood samples were tested for CAg by both standard ELISA and nano-based ELISA using anti-rabbit polyclonal IgG conjugated with AuNPs. CAg was only detected by nano-based ELISA 6, 8, 10 dpi and by both formats 12-28 dpi. Nano-based assay recorded a statistically significant high sensitivity (58.33%, 91.67%) and accuracy (72.22%, 94.44%) 8 and 10 dpi, respectively in comparison to standard ELISA. Both assays showed high sensitivity and accuracy 12-28 dpi. Thus, nano-based ELISA could be considered as an early sensitive diagnostic method for experimental trichinellosis.

Trichinella britovi muscle larvae and adult worms: stage-specific and common antigens detected by two-dimensional gel electrophoresis-based immunoblotting

Background

Trichinella britovi is the second most common species of Trichinella that may affect human health. As an early diagnosis of trichinellosis is crucial for effective treatment, it is important to identify sensitive, specific and common antigens of adult T. britovi worms and muscle larvae. The present study was undertaken to uncover the stage-specific and common proteins of T. britovi that may be used in specific diagnostics.

Methods

Somatic extracts obtained from two developmental stages, muscle larvae (ML) and adult worms (Ad), were separated using two-dimensional gel electrophoresis (2-DE) coupled with immunoblot analysis. The positively-visualized protein spots specific for each stage were identified through liquid chromatography-tandem mass spectrometry (LC-LC/MS).

Results

A total of 272 spots were detected in the proteome of T. britovi adult worms (Ad) and 261 in the muscle larvae (ML). The somatic extracts from Ad and ML were specifically recognized by T. britovi-infected swine sera at 10 days post infection (dpi) and 60 dpi, with a total of 70 prominent protein spots. According to immunoblotting patterns and LC-MS/MS results, the immunogenic spots recognized by different pig T. britovi-infected sera were divided into three groups for the two developmental stages: adult stage-specific proteins, muscle larvae stage-specific proteins, and proteins common to both stages. Forty-five Ad proteins (29 Ad-specific and 16 common) and thirteen ML proteins (nine ML-specific and four common) cross-reacted with sera at 10 dpi. Many of the proteins identified in Ad (myosin-4, myosin light chain kinase, paramyosin, intermediate filament protein B, actin-depolymerizing factor 1 and calreticulin) are involved in structural and motor activity. Among the most abundant proteins identified in ML were 14-3-3 protein zeta, actin-5C, ATP synthase subunit d, deoxyribonuclease-2-alpha, poly-cysteine and histide-tailed protein, enolase, V-type proton ATPase catalytic and serine protease 30. Heat-shock protein, intermediate filament protein ifa-1 and intermediate filament protein B were identified in both proteomes.

Conclusions

To our knowledge, this study represents the first immunoproteomic identification of the antigenic proteins of adult worms and muscle larvae of T. britovi. Our results provide a valuable basis for the development of diagnostic methods. The identification of common components for the two developmental stages of T. britovi may be useful in the preparation of parasitic antigens in recombinant forms for diagnostic use.

Immunoproteomic profile of Trichinella spiralis adult worm proteins recognized by early infection sera

Background

Trichinellosis, a widespread zoonosis, is regarded as an emerging or reemerging disease. Effective treatment and prognosis of trichinellosis depends on early diagnosis of the infection. The objective of this study was to identify sensitive and specific antigens for early diagnosis or effective vaccine antigens for preventing infection.

Methods

The somatic proteins of T. spiralis adult worms were separated by two-dimensional gel electrophoresis (2-DE). The separated proteins were probed with early infection sera from swine or mice infected with T. spiralis for 7 days. The primary immunoreactive spots were characterized by MALDI-TOF/TOF-MS analysis in combination with bioinformatics. The identified proteins were annotated using WEGO based on their functions. The immunodominant protein was chosen for expression as recombinant protein in E. coli and the purified recombinant protein was used to confirm its antigenicity by Western blot with the same infection sera.

Results

Approximately 300 spots were separated by 2-DE, with molecular weights ranging from 10 to 130 kDa, and pI values ranging from pH 4 to 10. The sera from swine and mice infected with T. spiralis for 7 days recognized 64 proteins. MALDI-TOF/TOF-MS analysis identified 55 proteins, some with different isoforms. Finally, 40 individual immunoreactive proteins were obtained with a wide range of biological functions. Several proteins, such as heat shock protein 70, 14-3-3 protein, and cysteine protease could be used as immunodiagnostic or vaccine antigens. Among these identified proteins, the highly immunodominant Ts14-3-3 was chosen for expression in E. coli and purified recombinant Ts14-3-3 was able to be strongly recognized by the same T. spiralis infected sera used for identifying these antigens, therefore the most promising antigen for early immunodiagnosis of Trichinella infection.

Conclusions

A total of 64 proteins from the adult worm were recognized by early infection sera from swine and mice infected with T. spiralis for 7 days. Several proteins, are of particular interest as immunodiagnostic or vaccine antigens, especially with Ts14-3-3 as most promising due to its highly immunogenicity during early infection, expressed protein can be recognized by Trichinella early infection sera and the native Ts14-3-3 expression in both adult and larval stages.

Trichinella spiralis: monoclonal antibody against the muscular larvae for the detection of circulating and fecal antigens in experimentally infected rats

In this work we search for antigens of Trichinella spiralis in sera and stool of rats experimentally infected. The kinetic of antibodies to excretory and secretory (ES) antigens of muscle larvae (ML) was also determined. Wistar rats were infected with 15 ML per gram of body weight and blood samples were collected weekly for 10 weeks. Antibodies were studied using an indirect ELISA. For detection of circulating antigens and coproantigens, a sandwich ELISA was developed with the use of polyclonal rabbit antibodies obtained against the total extract of ML and an IgM monoclonal antibody (Mab) against ES antigens of ML. No reactivity was observed between Mab and the total worm antigens of Angiostrongylus cantonensis, Ascaris suum, Echinococcus granulosus, Fasciola hepatica, Strongyloides stercoralis, Taenia solium, Toxocara canis and Trichuris trichiura. The IgM Mab recognized antigens of 45, 49, and 55 kDa in ES antigens and was unable to bind ES antigens deglycosylated with trifluoromethanesulphonic acid (TFMS) indicating that a glycan structure is present in the epitope recognized by this Mab. The sensitivity of sandwich ELISA was 1 ng/mL. Circulating antigens were detected in all infected rats between 3 and 8 weeks post infection and coproantigens were found during the first two days post infection. Antibodies were detected since the third week post infection through the end of experiment. These results suggested that antigen detection by our sandwich ELISA could be a useful complementary laboratory test for antibody detection.

Detection of Trichinella spiralis DNA in mouse faeces during the early stage of infection

Trichinella spiralis is an etiological agent of trichinellosis, a parasitic disease present worldwide, affecting both animals and humans. The infection starts from the intestinal stage which usually lasts a few weeks and develops into the muscle phase when larvae enter the muscle cells and create a nurse cell-larva-complex. In animals, the infection is asymptomatic even if a high number of larvae is ingested. The aim of this work was to develop a sensitive test to monitor the early phase of trichinellosis in laboratory animals. T. spiralis DNA presence was assayed in faeces of mice during the first 21 days of experimental infection. The target gene fragment of the mitochondrial ATP6 synthase F0 subunit was amplified by PCR from faecal samples of mice infected with 50, 250 or 500 larvae per mouse (lpm). Trichinella DNA was detected in 45% (116) of the examined faecal samples from days 1 to 21 post infection (p.i.). The time of appearance of the parasite DNA in the faeces and the percentage of PCR positive results were dose dependent. In collective samples consisting of faeces from 3 mice average 80%, 83% and 90% of PCR positive results were obtained for 50, 250 and 500 lpm doses, respectively, throughout 21 days of the observation period. In individual mice faeces DNA was detected on days 2-19 and 9-18 p.i. for 250 lpm and 50 lpm doses, respectively. For both infective doses the highest probability of DNA detection was on day 11 p.i. Since the developed test is simple and non-invasive, it can be useful for monitoring the intestinal phase of Trichinella sp. infection in laboratory animals.