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Domestic and sylvatic Trichinella genotypes were evaluated for infectivity, muscle larvae persistence, and host antibody responses in rats. Groups of rats were inoculated with T. spiralis, T. nativa, T. britovi, three genotypes of T. pseudospiralis (from USSR, USA, and Australia), T. murrelli, Trichinella T6, and T. nelsoni, respectively. The muscle larvae intensity (larvae per gram), total larval burden (lpg x rat weight), and the antibody levels were determined at necropsy 5, 10, 20, and 40 weeks post inoculation. All Trichinella genotypes were established in the rats, but infectivity and persistence differed significantly: T. spiralis established and persisted in high numbers, the three T. pseudospiralis genotypes were also highly infective but differed significantly in persistence, T. britovi and T. nativa had limited infectivity and persistence, Trichinella T6 had low infectivity and very low persistence, and T. murrelli and T. nelsoni were almost non-infective. Except for T. spiralis, initial total muscle larval burdens declined significantly for other genotypes during the experiment. A high initial serological response was detected for all genotypes, but the antibody levels decreased rapidly in relation to decreasing larval burdens. After 20 w.p.i. the antibody levels remained high only in T. spiralis and T. pseudospiralis infected rats. The high infectivity and persistence of T. pseudospiralis in rats, suggests that in addition to T. spiralis, this species might be of significant importance in the domestic cycle of trichinellosis.

The bioavailability and anthelmintic activity of albendazole-cyclodextrin complexes (ABZ-CDC) compared to albendazole suspensions in carboxymethylcellulose (ABZ-CMC) was assessed in a mouse model for Trichinella infections. Swiss CD-1 mice experimentally infected with T. spiralis were treated with both formulations against enteral (adult worms) and parenteral (migrating and encysted larvae). Oral bioavailability was assessed in age matched mice treated with 50 mg/kg of both formulations. The anthelmintic effects and plasma concentration of the active metabolite albendazole-sulphoxide (ABZSO) enantiomer (-) were significantly increased following administration of ABZ-CDC in relation to ABZ-CMC.

Characterization of human IgA responses to newborn larva (NBL) and TSL-1 antigens was carried out by ELISA assays. Relevant and differential IgA antibody responses to these antigens were detected in humans infected with T. spiralis. The inhibition ELISA results showed that the IgA response to NBL antigens was inhibited significantly by both NBL and TSL-1 antigens and to a lesser extent when phosphorylcholine (PC) was used as inhibitor. In contrast, the IgA response to TSL-1 antigens was inhibited by the homologous antigen and to a lesser extent by the NBL and PC. Thus, the early IgA antibodies developed in trichinellosis patients contained a portion of IgA antibodies directed to PC which is present in TSL-1, A and NBL component. Another portion of antibodies to NBL are directed to other common non-defined epitopes present in TSL-1 and NBL antigens. All together these results suggest that the IgA response to common epitopes in antigens of both stages of the parasite may be useful for early diagnosis and epidemiological studies of human trichinellosis.

The antibody isotype response to Trichinella spiralis excretory/secretory (ES) products of muscle larva was examined using sera from patients with confirmed trichinellosis. Using Western blots we identify components of the ES antigen that are recognized by IgM and IgG antibodies. A 45 kDa component was strongly recognized by different antibody classes and subclasses. We observed a 45 kDa-specific IgG4 response that was detected exclusively using sera of patients with trichinellosis and not of patients with echinococcosis, filariasis, cysticercosis, ascariasis, strongyloidiasis or toxocariasis. These results are relevant for the diagnosis of human trichinellosis.

A novel lateral flow card (TS-Card pork) test was developed for the serological detection of Trichinella infected pigs. Based on extensive studies performed in Romania during 1999-2000 this test proved to be highly specific sensitive, rapid (3-12 minutes) and easy to use (no need for laboratory facilities). It can be used both for the detection of Trichinella infection in carcasses and for epizooliological studies using a variety of samples including whole or dried blood, serum, or tissue fluids. The TS-Card pork test, used as a screening test, can be the foundation of an on-farm or field based inspection system to significantly improve food safety in countries with a high prevalence of Trichinella in pigs or other food animal species. The results presented are also promising for application of the test in an on-line laboratory based inspection system since the speed of the test allows sufficient time to rail out suspected hog carcasses during the slaughter process.

Clinical studies performed in 44 patients, one, three, four, six or seven years after they had experienced trichinellosis demonstrated the persistence of various general and motor ailments in 88.7% of the patients. The persisting for many years antibodies against E/S antigen of Trichinella in 86.4% of examined patients seem to reflect chronic stimulation by the larvae which, as shown by parasitological and histopathological tests, survived longer and underwent gradual destruction in muscles. Bio-electric disturbances in muscles were most frequently of a mixed type, with prevalence of a neural type record. These observations illustrate a disturbed function of motor neurones and of impulse transmission at the myoneural junction in patients chronically infected with Trichinella.

Results of our studies using ELISA and competitive inhibition assay (CIA) tests fully confirmed the previously experienced trichinellosis and reflected persistent stimulation of antibody production due to the antigen release from Trichinella larvae, which had survived longer and undergone gradual destruction in the muscles. The studies proved that the tests complement each other, yielding concordant results in 86.7% of cases. Due to its higher specificity, the CIA test can help in interpreting pathological signs/symptoms and in evaluating humoral response activity at late and distant in time periods following the invasion.

Different assays to detect antigens of Trichinella spiralis during current infection have been standardized, although sensitivity values have been the main limitation to use them as routine diagnostic test. We report the production and use of monoclonal antibodies (MAbs) against the new born larvae which recognize both somatic and metabolic antigens from adult and muscular larvae (ML). We used two IgG3 MAbs (4B1, 4B2) and two IgG2a (2D3, 2D4) to detect antigens during experimental infection. All MAbs detect fecal antigens starting the second to third week post infection (wpi), although it was less clear with MAbs 4B1 and 4B2, while circulating antigens were detected from third to fourth wpi. Thus, the recognition of shared antigens among T. spiralis developmental stages can be used for early diagnosis of trichinellosis.

We report the analysis by ELISA of class and subclass antibody response against a total soluble extract from T. spiralis adult stage (TSE-A) during a year after the infection in 17 symptomatic trichinellosis patients (SI) and five asymptomatic individual (AI) involved in an outbreak of trichinellosis occurred in the State of Mexico. Serum samples from 20 healthy individuals (HI) and 24 patients with other parasitosis were included as control. All SI showed a polyisotypic antibody response against the TSE-A, during the infection. Higher response of IgA, IgE, IgM were detected in SI during the acute phase of the infection, but only IgE remained at high levels all along the infection. None or a lower reactivity against TSE-A was observed in sera from AI and from HI. Some patients with trichuriosis and ascariosis showed a higher cross-reactivity, against TSE-A when IgG and their subclasses were analyzed.

A follow-up study of the class antibody responses to newborn larva (NBL) antigens in individuals involved in an outbreak of human trichinellosis was carried out by ELISA assays. The data showed that similar kinetics of antibody responses of different magnitude developed in trichinellosis patients; it was low by week 3, a peak raised by week 5 and decreased from week 7 up to the end of the study. The IgA-ELISA assay was the most sensitive and specific while the IgM was the least sensitive and specific. IgA antibodies to NBL antigens were detected in 80% of patients while IgE, IgG and IgM responses were observed in 44, 31 and 19% of the patients by week 3, respectively. From weeks 5 to 7, IgA antibodies were found in 89 to 100% of the patients while lower percentages (0-82%) were found for the other isotypes. Reactivity of IgA, IgE, IgG and IgM to NBL antigens decreased from week 37 to 57 after infection (0-38%). These results suggest that detection of IgA antibodies may be useful for early diagnosis and epidemiological studies in human trichinellosis.

Hosts infected with Trichinella produce antibodies specific for an epitope common to the TSL-1 family antigens. This epitope contained uncommon terminal 3, 6-dideoxy-D-arabinohexose (so called tyvelose) residues. The disaccharide moiety was synthesized and an immunodiagnostic assay was developed, which was specific and sensitive in swine trichinellosis. We aimed to verify the specificity and sensitivity of this immunodiagnostic test in human trichinellosis. 15 sera from normal subjects, 12 from patients with other parasitic diseases and 50 from trichinellosis patients were tested. Indirect enzyme linked immunosorbent assay (ELISA) for specific IgG and an amplified ELISA for specific IgE were performed using beta-tyvelose-GalNAc-bovine serum albumin (BSA) disaccharide conjugate or T. spiralis muscle larvae excretory/secretory (E/S) products, as antigens. Neither control sera nor other parasitic infection sera resulted positive both for IgG and IgE when synthetic or E/S antigens were used. In trichinellosis patient sera, specific IgG were present in 100% of cases, irrespective of the antigen used, but whereas specific IgE were detected in 78% using E/S antigens, a 100% positivity rate was obtained, using the beta-tyvelose-BSA conjugate.