Protein deficiency during Trichinella spiralis infection impairs lung immunity against newborn larvae.

The goal of this study was to analyse the effects of a protein-deficient (PD) diet on antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro against newborn larvae (NBL) of Trichinella spiralis in the lungs of infected rats. Two groups of weaning Wistar rats received a PD diet (6.5% casein) and other two received a control diet (C, 20% casein). After ten days, one group of each diet was infected (PDI and CI ) with muscle larvae. Lung tissue extracts (LTE) and lung cell suspension (LCS) were obtained. PDI had lower titres of anti-NBL antibodies in LTE than CI . In ADCC assays using control cells, NBL mortality percentage was lower with LTE from PDI than LTE from CI (P < .01). In assays using control cytotoxic sera, ADCC was exerted by LCS from CI at all days post-infection (p.i.), but only by LCS from 13 days p.i. from PDI . ADCC assays combining LTE and LCS from the same group showed a lower response for PDI than for CI (P < .0001). LCS from PDI contained lower numbers of neutrophils, eosinophils and FcεRI+ cells than CI . PD may diminish ADCC activity against T spiralis NBL in lungs through alterations in specific antibodies and effector cells.

Serum IgE and IgG4 against muscle larva excretory-secretory products during the early and late phases of human trichinellosis.

In human trichinellosis, the relevance of the presence and persistence of specific serum IgE and IgG4 during the early and late phases of infection is still controversial.The aim of this work was to determine the percentage of human sera presenting IgE and IgG4 against Trichinella spiralis muscle larvae excretory-secretory products as well as their levels during the early and late phases of the infection. The antigen recognition pattern by serum total immunoglobulins (IgGAM), IgE, and IgG4 was assessed over time. Serum samples during early and late phases were analyzed by ELISA and immunoelectrotransfer blot (IETB).Results showed that (a)-IgE and IgG4 are present at constant levels in both phases; (b)-IgE recognized the glycoproteins of ~ 45 and ~ 55 kDa and IgG4 only the ~ 45 kDa;

Trichinella spiralis: killing of newborn larvae by lung cells.

The migratory stage of Trichinella spiralis, the newborn larva (NBL), travels along the pulmonary microvascular system on its way to the skeletal muscle cells. The present work studies the capability of lung cells to kill NBL. For this purpose, in vitro cytotoxicity assays were performed using NBL, lung cell suspensions from Wistar rats, rat anti-NBL surface sera, and fresh serum as complement source. The cytotoxic activity of lung cells from rats infected on day 6 p.i. was compared with that from noninfected rats. Two and 20 h-old NBL (NBL2 and NBL20) were used as they had shown to exhibit different surface antigens altering their biological activity. Sera antibodies were analyzed by indirect immunofluorescence assay, and cell populations used in each assay were characterized by histological staining. The role of IgE in the cytotoxic attack against NBL was analyzed using heated serum. The FcεRI expression on cell suspensions was examined by flow cytometry. Results showed that lung cells were capable of killing NBL by antibody-dependent cell-mediated cytotoxicity (ADCC). Lung cells from infected animals yielded the highest mortality percentages of NBL, with NBL20 being the most susceptible to such attack. IgE yielded a critical role in the cytotoxic attack. Regarding the analysis of cell suspensions, cells from infected rats showed an increase in the percentage of eosinophils, neutrophils, and the number of cells expressing the FcεRI receptor. We conclude that lung cells are capable of killing NBL in the presence of specific antibodies, supporting the idea that the lung is one of the sites where the NBL death occurs due to ADCC.

Protein malnutrition impairs the immune control of Trichinella spiralis infection.

OBJECTIVES: We aimed to analyze the effect of a protein-deficient diet on mucosal and systemic immunity during a Trichinella spiralis infection. METHODS: Two groups of weaning Wistar rats received a protein-deficient diet (6.5% casein) and the other two groups received a control diet (20% casein). After 10 d, one group of each diet was infected (PDI and CI) with muscle larvae (infecting stage). Food intake and body weight were assessed over time. Blood eosinophils counts, antibodies in serum, and tissue extracts were assessed at different days postinfection. Histologic studies were done in the lungs and intestines, and adult worm (AW) fecundity index score and muscle parasite burden were determined. RESULTS: Food and protein intake were lower in PDI than in CI. Body weight was lower in PDI than in a non-infected protein-deficient diet. Eosinophils counts were lower in PDI than in CI. Total and specific antibodies were lower in PDI than CI. PDI had a reduced number of mast and goblet cells in the lungs and intestines compared with CI. The persistence of AW in the intestines and migrant larvae at the lungs was longer in PDI than in CI.. The AW fecundity index score was higher in PDI than in CI. Finally, PDI evidenced a higher muscular parasite burden than CI. CONCLUSIONS: Protein deficiency affects the mucosal and systemic immune response to Trichinella spiralis and delays the expulsion and increases the fecundity index score of AW, which leads to a higher parasite burden in the muscles.

Regulatory parameters of the lung immune response during the early phase of experimental trichinellosis.

Parasitic infection caused by Trichinella spiralis provokes an early stimulation of the mucosal immune system which causes an allergic inflammatory response in the lungs. The present work was intended to characterize the kinetics of emergence of regulatory parameters in Wistar rat lungs during this early inflammatory response, between days 0 and 13p.i. The presence of regulatory cells such as regulatory T cells (Tregs) and alternatively activated macrophages (AAM) was analyzed in lung cell suspensions. Moreover, a regulatory cytokine (TGF-ß) was studied in lung tissue extracts. Considering that newborn larvae (NBL) travel along the pulmonary microvasculature, the ability of this parasite stage to modulate the activation of lung macrophages was evaluated. For this purpose, lung macrophages from non-infected or infected rats (day 6p.i.) were cultured with live or dead NBL. Arginase activity (characteristic of AAM) and nitric oxide (NO produced by iNOS, characteristic of classical activated macrophages) were measured after 48h. Our results revealed a significant increase in the percentage of Tregs on days 6 and 13p.i., arginase activity on day 13p.i. and TGF-ß levels on days 6 and 13p.i. Lung macrophages from non-infected rats cultured with live NBL showed a significant increase in arginase activity and NO levels. Live and dead NBL induced a significant increase in arginase activity in lung macrophages from infected rats. Only live NBL significantly increased NO levels in these macrophages. The present work demonstrates for the first time, the emergence of regulatory parameters in the early lung immune response during T. spiralis infection. The immumodulatory properties exerted by NBL during its passage through this organ could be the cause of such regulation. Moreover, we have shown the ability of NBL to activate macrophages from the lung parenchyma by the classical and alternative pathways.

Trichinella spiralis infection and transplacental passage in human pregnancy.

Infection by Trichinella spp. during pregnancy still arises many questions. Worldwide an important number of trichinellosis outbreaks have occurred over time where pregnant women were or might have been involved. Parasitological and immunoserological parameters, clinical background and transplacental passage of Trichinella spiralis of six pregnant women, from different outbreaks, were studied. Serum samples were collected from patients and their children: at pregnancy, at delivery, newborn and/or infant (≥1 year-old). Total immunoglobulins (Igs) and isotypes against excretion-secretion products from muscle larvae (ESP-ML) and newborn larvae (NBL) of T. spiralis were detected by immunoserological techniques. Sera helminthocytotoxic activity against NBL was evaluated by antibodies dependent cell cytotoxicity assay. Patients presented similar clinical symptoms. Mother's sera showed differences in the presence and titres of Igs, IgE, IgG1 and IgG4 against NBL surface. All of them showed helminthocytotoxic activity against NBL, four in progesterone dependent manner and the other two by antibodies. Igs anti ESP-ML were present in mother's sera, with differences in the isotypes detected. Anti-ESP-ML IgE, IgA and/or IgM in newborn sera were observed. Three out of four infants showed specific Igs; one even at 8 years-old. The distinct immune response between mothers at pregnancy evidenced by sera helminthocytotoxic activity and immunoserological parameters may be associated with a different parasite burden exposition. Specific Igs observed in newborns would be a suggestion of transplacental passage of this Igs and/or their production by the fetus. Specific Igs found in infants sera suggests that newborn larvae transplacental passage is possible.