Prolactin-like hormone in the nematode Trichinella spiralis larvae

Expression of prolactin (PRL) or prolactin-like hormone has been reported in invertebrates. We investigated the larval phase of Trichinella spiralis: (a) to express 23 kDa PRL, (b) to define its localization and (c) to test its possible biological activity. Immunostaining in isolated larvae demonstrated positive material to 23 kDa PRL by all along the stichosome, specifically in the stichocytes. Homogenized immunoblot larvae showed a 23 kDa protein band. To assess PRL release and its biological activity, larvae were incubated in culture medium and the excretory/secretory products were analyzed by the Nb2 cells bioassay. A cellular growth equivalent until 10 nM PRL and using antibody against 23 kDa PRL, the growth was blocked. In conclusion our result provides evidence that PRL-like hormone is expressed and secreted by the larvae of T. spiralis.     

Trichinella spiralis: infection reduces airway allergic inflammation in mice

In an effort to define the mechanism underlying the host immune downregulation inherent to Trichinella spiralis infection, we compared the levels of Th1, Th2, and regulatory cytokines and CD4⁺CD25⁺ forkhead box P3 (FoxP3)⁺ T (T_reg) cell recruitment, as well as cellular pathology in the airway between T. spiralis infected and uninfected asthma-induced mice. After the induction of allergic airway inflammation, we noted influxes of inflammatory cells into the peribronchial tree. However, in the T. spiralis infection groups, cellular infiltration was minimal around the bronchial tree, with only a smattering of inflammatory cells. In the OVA-challenged group after T. spiralis infection, the numbers of macrophages and eosinophils in the bronchial alveolar lavage fluid were reduced by 23% and 52%, respectively, as compared to those of the OVA-challenged group. Airway hyperresponsiveness of OVA-challenged mice after T. spiralis infection was significantly suppressed as compared to the OVA-only challenged mice. The T. spiralis-infected mice exhibited a significant reduction in IL-5 concentrations relative to that noted in the OVA-challenged group (p < 0.01). Nevertheless, the regulatory cytokines IL-10 and TGF-β levels were increased significantly as the result of T. spiralis infection, and we verified the recruitment of T_reg cells in lung draining lymph nodes via T. spiralis infection. Therefore, T_reg cells, which were recruited by T. spiralis infection, might ameliorate lung function and reduce allergic airway inflammation.     

Novel albendazole formulations given during the intestinal phase of Trichinella spiralis infection reduce effectively parasitic muscle burden in mice

Trichinellosis is a zoonotic disease affecting people all over the world, for which there is no speedy and reliable treatment. Albendazole (ABZ), an inexpensive benzimidazole used in oral chemotherapy against helminthic diseases, has a broad spectrum activity and is well tolerated. However, the low absorption and variable bioavailability of the drug due to its low aqueous solubility are serious disadvantages for a successful therapy. In this study, we evaluated the in vivo antiparasitic activity of three novel solid microencapsulated formulations, designed to improve ABZ dissolution rate, in a murine model of trichinellosis. Both ABZ and the microparticulate formulations were administered during the intestinal phase of the parasite cycle, on days 5 and 6 post-infection. This protocol significantly decreased muscle larval burden measured in the parenteral phase, on day 30 post-infection, when compared with the untreated control. Moreover, two of the three microencapsulated formulations both strongly and consistently reduced worm burden.     

Biphasic hypothermia in mice infected with a parasitic nematode, Trichinella spiralis.

In BALB/c mice infected with Trichinella spiralis, changes in body temperature (Tb) were observed over 35 days after the infection. T. spiralis infection induced hypothermia two times at 7 and 28 days after infection. The initial decrease persisted for about one week with a peak (37.1 +/- 0.62 degrees C) around 10 days after the infection, while the later phase persisted for at least one week. Both 10 and 35 days after the infection, there were remarkable decreases in Tb. The serum glucose level of infected mice at 10 days was significantly (p < 0.01) decreased compared with that of control mice at the same number of days, while the level in infected mice at 35 days was not decreased. Moreover, the later phase of hypothermia was prevented by the cyclooxygenase inhibitor indomethacin (10 mg/kg i.p.), while the initial phase was not. We conclude that hypothermia was caused by two different mechanisms, involving the effects of hypoglycemia and prostaglandins.     

Characterization of cholinesterases from the parasitic nematode Trichinella spiralis

1. Trichinella cholinesterases occur in multiple molecular forms which differ in size, kinetics, activity with butyrylthiocholine, and effects of inhibitors.2. The 5.3 and 13S forms identified in Trichinella extracts are also found in C. elegans and other nematodes but the 7S form which occurs in other nematodes was absent from Trichinella detergent extracts. Differences in kinetic and inhibition properties among nematode species were also evident.3. The level of cholinesterases in excretory/secretory products is low.4. Trichinella cholinesterases did not elicit a detectable antibody response in mice.     

Trichinella spiralis infections of inbred mice: immunologically specific responses induced by different Trichinella isolates

The immune response of inbred mice was studied following infection with Trichinella spiralis var. pseudospiralis (TP) or with isolates of T. spiralis derived from a pig or from an arctic fox. Animals given a primary infection with 1 isolate of Trichinella and challenged 21 days later with the same or different isolates responded more quickly by expelling worms from the homologous challenge. In addition, although mesenteric lymph node cells from mice infected with each isolate of Trichinella would proliferate in vitro when cultured with antigen derived from each of the others, the strongest proliferation response always occurred when cells were cultured in the presence of antigen prepared from the specific isolate used to infect the mouse from which the cells were derived. In addition, it was possible to prepare monoclonal antibodies that recognized an antigen expressed by TP which was not shared by T. spiralis isolates and vice versa. Collectively, these data support the conclusion that the differences observed in the kinetics of immune responsiveness to different Trichinella isolates are referable, at least in part, to differences among the isolates in the expression of functionally relevant antigens.     

Cells containing IgE in the intestinal mucosa of mice infected with the nematode parasite Trichinella spiralis are predominantly of a mast cell lineage

To determine whether IgE+ cells in the intestinal mucosa of nematode-infected mice were of a mast cell or a lymphocyte lineage, the intestinal mucosae of mast cell-deficient w/wv mice were examined for IgE+ cells after inoculation with Trichinella spiralis muscle-stage larvae. Immunofluorescence staining techniques were used to detect IgE associated with cells in the intestinal mucosa. Comparisons were made among four strains of mice, w/wv (mast cell-deficient), +/+ (normal congenic littermates of w/wv), BALB/c, and SJL, that were either uninfected controls or inoculated with T. spiralis. Tissue sections from the small intestine of T. spiralis-infected BALB/c, SJL, and +/+ mice were fixed in ethanol and were stained with an affinity-purified F(ab')2 rabbit anti-mouse IgE followed by FITC goat anti-rabbit IgG. Large numbers of cells in the intestinal mucosa exhibited bright fluorescence. When other sections of intestines from these mice were processed in Carnoy's fixative and were stained with alcian blue at low pH (a metachromatic stain for mast cells) or alcian blue followed by immunofluorescence staining for IgE, large numbers of mast cells were observed in the intestinal mucosa, and 70 to 90% stained positively for IgE. There was a considerable number of cells in the intestinal mucosa which were IgE+ but which did not stain with alcian blue. Few alcian blue-positive cells and no IgE+ staining cells were present in the intestinal mucosa of control, uninfected +/+, BALB/c, and SJL mice. To determine whether these IgE+ alcian blue-negative cells were of a lymphocyte or a mast cell lineage, the mast cell-deficient w/wv mouse strain was examined after infection with T. spiralis. In contrast to BALB/c, SJL, or +/+ mice, few cells in the intestinal mucosa of T. spiralis-infected w/wv mice stained with alcian blue or were positive for IgE. However, when the IgE response in the MLN of the w/wv mice was compared to the IgE response of BALB/c, SJL, and +/+ mice, numerous IgE+ cells, but no alcian blue-positive cells, were observed in the parenchyma of the MLN from all four strains of T. spiralis-infected mice. In addition, flow microfluorometric analysis of MLN cells stained for surface IgE in suspension showed a comparable proportion of IgE-bearing cells, which were mostly B lymphocytes, among all four strains of T. spiralis-infected mice.(ABSTRACT TRUNCATED AT 400 WORDS)     

Trichinella spiralis infections of inbred mice: genetics of the host response following infection with different Trichinella isolates

The immune response of inbred strains of mice was studied following infection with isolates of Trichinella from a pig (P1), an arctic fox (AF1), and T. spiralis var. pseudospiralis (TP). Strains of mice previously characterized as highly resistant to a separate pig isolate of T. spiralis responded to the P1 and AF1 isolates by expelling over 80% of the worms by day 10 postinfection (PI), and by suppressing the in vitro release of newborn larvae by female worms. However, the response induced by AF1 worms was expressed more quickly when compared to responses induced by the P1 and TP isolates. The host response to TP was less as recovery was always higher at day 10 PI and antifecundity effects were not induced in TP worms even in highly resistant strains of mice. Strains of mice previously characterized as susceptible to T. spiralis infection were slow to develop resistance when compared to the resistant mouse strains, but even among the susceptible strains, infection with AF1 induced a more rapid response. The mouse strains used in these experiments allowed us to assess the role of the major histocompatibility complex (MHC) and/or non-MHC genes in influencing the responses observed. As previously reported for a pig isolate of T. spiralis, both MHC and non-MHC genes influenced the rate at which worms were expelled from the gut and the host response that limits the fecundity of adult female worms.     

Immune responses to Trichinella pseudospiralis and Trichinella spiralis in mice

Primary infections with Trichinella pseudospiralis and Trichinella spiralis were followed in rapid- (NIH) and slow- (B10G) responder strains of mice. Expulsion of T. pseudospiralis was slower in both strains, but markedly so only in slower responder B10G mice. Blast cell activity in the mesenteric lymph nodes of the mice correlated with the expulsion patterns. In NIH mice, both parasites stimulated a strong response by day 8 of infection and activity had returned to control levels by day 11. In B10G mice, T. spiralis elicited an earlier peak response (day 12) than T. pseudospiralis (day 18), but in both, activity returned to control levels by day 21. Immunity to T. pseudospiralis and T. spiralis could be stimulated in NIH mice by prior infection with either parasite, by injection of T. spiralis larval antigen and by adoptive transfer of immune mesenteric lymph node cells taken from mice infected with either parasite. This extensive cross reactivity, and the differences seen during primary infections, are discussed in relation to the biology and specific identity of the two worms.