Trichinella Spiralis Infection Research Articles

PL-003 Protective effect of a pvax1-Ts87 DNA vaccine delivered in attenuated Salmonella typhimurium against Trichinella spiralis infection in mice

PL-003 Protective effect of a pvax1-Ts87 DNA vaccine delivered in attenuated Salmonella typhimurium against Trichinella spiralis infection in mice

Th17 cells influence intestinal muscle contraction during Trichinella spiralis infection

Trichinella spiralis infection in rodents is a well-known model of intestinal inflammation associated with hypermotility. The aim of the study was to use this experimental model to elucidate if Th17 cells are involved in the development of gastrointestinal hypermotility. Colonic smooth muscle contractility was investigated in response to acetylcholine. The levels of IL-17, IL-23 and TGF-beta1 in colon were measured by Western blotting. Flow cytometric detection of intracellular IFN-gamma/IL-4/IL-17 cytokine production was used to analyze the proportions of CD4+ T cells subsets in colon. Our results showed that colonic muscle contractility was increased 2 weeks post infection (PI) and stayed high 12 weeks PI when no discernible inflammation was present in the gut. The proportion of Th17 cells and the expression of IL-17 were up-regulated in colon 2 weeks PI and returned to normal 8 weeks PI. The content of IL-17 was correlated with the colonic smooth muscle hypercontracility 2 weeks PI. Meanwhile, TGF-beta1 was increased 2 weeks PI, while IL-23 was normal. Our results suggest that Th17 cells affect the colonic muscle contractility in mice infected with Trichinella spiralis at intestine stage but not at muscle stage and the effect of Th17 cells on muscle contractility might be induced by TGF-beta1. Other cytokines might be involved in the hypercontracility of colonic smooth muscle at muscle stage.

Strain difference in susceptibility to Trichinella spiralis infection between dark agouti and albino oxford rats

The influence of host genetics on the susceptibility to primary Trichinella spiralis infection has been extensively studied in a mouse model, but has not been clarified for rats. Analyses of interstrain and intrastrain genetic variation in response to infectious agents could be beneficial not only for elucidating the genetic basis of host resistance/susceptibility, but for revealing immune response mechanisms as well. The aim of this study was to analyse interstrain differences in worm burdens and cytokine production between Albino Oxford (AO) and Dark Agouti (DA) rats in muscle phase of T. spiralis infection. Clear strain-dependent variation was observed in the number of T. spiralis larvae per gram (lpg) of muscle tissue where values for DA rats (626.7±171lpg) vastly exceeded those found in AO rats (49.8±25.9lpg, p<0.001). Differences between the strains were also noticed in key cytokine levels. In infected AO rats, the cytokine production remained in favor of Th1 type response, while infected DA rats showed a shift towards a Th2 type response. The level of regulatory IL-10 was significantly increased only in T. spiralis infected DA rats. Our results provide evidence that DA rats express higher susceptibility to T. spiralis infection in comparison to AO rats with respect to muscle larvae burden. The infection in DA rats was accompanied by the production of anti-inflammatory cytokines, while the response of AO rats was characterized by a proinflammatory type of immune response.

The effectors responsible for gastrointestinal nematode parasites, Trichinella spiralis, expulsion in rats

Helper T (Th2) cells type 2 have a central role in host protective responses to gastrointestinal nematode parasite, Trichinella spiralis infection, but the actual effector mechanisms involved in parasite expulsion are still uncertain. Recent evidences suggest that mast cell recruitment and activation may associate with parasite elimination from host intestines in mice. On the other hand, IgE production may induce defensive responses to primary infection with the helminth in rats. The differences of host effector mechanisms to the same experimental infections might disturb our understanding of the host protective mechanisms to gastrointestinal nematode parasite infection. In order to redefine these differences, we investigated in detail the relationship between intestinal immune responses and worm expulsion following T. spiralis infection among several rat strains including mutants. As a result, there were significant correlations of parasite expulsion with mast cell hyperplasia in addition to serum IgE level. Moreover, mast cell-deficient and dysfunction rats showed delayed worm elimination from their gut. Therefore, the present study suggests that mast cells should also be one of the prominent effector cells involved in T. spiralis parasite expulsion in rats as well as mice.

Larval viability and serological response in horses with long-term Trichinella spiralis infection

The horse is considered an aberrant host for the nematode parasite Trichinella spiralis, and many aspects of the biology and epidemiology of Trichinella infection in the horse are poorly understood. It has been reported that experimentally-infected horses produce a transient serological response to infection and that muscle larvae are cleared more rapidly than in parasite-adapted hosts such as the pig and humans. However, limited numbers of animals have been studied, and both the longevity of larvae in horse musculature and the immune response to Trichinella larvae remain unclear. In this study, we infected 35 horses with 1000, 5000, or 10,000 T. spiralis muscle larvae and followed the course of infection for 1 year, assessing larval burdens in selected muscles, the condition and infectivity of recovered larvae, and the serological response of infected horses. The results demonstrated that T. spiralis establishes infection in horses in a dose dependent manner. Anti- Trichinella IgG antibodies peaked between weeks 6–10 post-inoculation. Viable, infective larvae persisted in horse musculature for the duration of the study (12 months), and exhibited no apparent reduction in muscle burdens over this period. Encapsulated larvae showed no obvious signs of degeneration in histological sections. Larval capsules were surrounded by infiltrates consisting of mature plasma cells and eosinophils. Macrophages were notably absent. Given the lack of a detectable serological response by 26 weeks p.i. and the persistence of infective muscle larvae for at least 1 year, parasite recovery methods are currently the only suitable detection assays for both meat inspection and epidemiological studies of Trichinella infection in the horse.

Acute trichinellosis increases susceptibility to Giardia lamblia infection in the mouse model

The intestinal protozoan parasite Giardia lamblia causes diarrhoea in humans and animals. In the present study, we used the C57BL/6 inbred mouse model to assess the impact of a nematode (Trichinella spiralis) infection on the course of a G. lamblia (clone GS/M-83-H7) infection. Acute trichinellosis coincided with transient intestinal inflammation and generated an intestinal environment that strongly promoted growth of G. lamblia trophozoites although the local anti-Giardia immunoglobulin (Ig) A production was not affected. This increased G. lamblia infection intensity correlated with intestinal mast cell infiltration, mast cell degranulation, and total IgE production. Furthermore, a G. lamblia single-infection investigated in parallel also resulted in intestinal mast cell accumulation but severe infiltration was triggered in the absence of IgE. Recently, intestinal mast cells emerging during a G. lamblia infection were reported to be involved in those immunological mechanisms that control intestinal proliferation of the parasite in mice. This anti-giardial activity was assumed to be related to the capacity of mast cells to produce IL-6. However, this previous assumption was questioned by our present immunohistological findings indicating that murine intestinal mast cells, activated during a G. lamblia infection were IL-6-negative. In the present co-infection experiments, mast cells induced during acute trichinellosis were not able to control a concurrent G. lamblia infection. This observation makes it feasible that the T. spiralis infection created an immunological and physiological environment that superimposed the anti-giardial effect of mast cells and thus favoured intestinal growth of G. lamblia trophozoites in double-infected mice. Furthermore, our findings raise the possibility that intestinal inflammation e.g. as a consequence of a 'pre-existing' nematode infection is a factor which contributes to increased susceptibility of a host to a G. lamblia infection. The phenomenon of a 'pre-existing' nematode infection prior to a G. lamblia infection is a frequent constellation in endemic areas of giardiasis and may therefore have a direct impact on the epidemiological situation of the disease.

Vaccination of mice against intestinal Trichinella spiralis infections by oral administration of antigens microencapsulated in methacrilic acid copolymers

BALB/c and NIH mice have been successfully vaccinated against the intestinal nematode Trichinella spiralis by oral administration of crude larval extracts (CLE) and excretory–secretory (ES) products derived from first stage T. spiralis larvae (L1) encapsulated in microcapsules made of copolymers of the metacrylic acid (Eudragit L100). Oral vaccination stimulated the secretion of IFN-γ and inhibited the secretion of IL-4 in spleen and mesenteric lymph nodes (MLN) of BALB/c mice. In vaccinated mice the proportion of CD4+ cells increased ( p < 0.05) in Peyer's patches (PP) and decreased ( p < 0.05) in spleen whereas the proportion of CD19+ cells decreased ( p < 0.05) in both PP and spleen, with regard to unvaccinated controls. No variation was evident for the proportion of CD8+ cells. Oral vaccination elevated the antigen-specific serum IgG1 and IgA ( p < 0.05) as well as the antigen-specific IgA response in MLN ( p < 0.05). It is concluded that this way of vaccination induced a concurrent Th1/ Th2 local and systemic responses that are protective and at the same time they may help balancing the strong Th2 response triggered by helminth infections.

OX40 interactions in gastrointestinal nematode infection

The immune expulsion of gastrointestinal nematode parasites is usually associated with T helper type 2 (Th2) responses, but the effector mechanisms directly responsible for parasite loss have not been elucidated. The intestinal inflammatory response accompanying infection with gastrointestinal helminths is thought to be a contributory factor leading to the expulsion of the parasite. However, we have shown that the intestinal inflammation, which is controlled by interleukin (IL)-4, is not required for parasite expulsion. OX40-OX40 ligand (L) signals have been shown to be important for the development of Th2 immune responses but are also involved in a number of inflammatory diseases including those of the intestine. Here, we have investigated the effect of OX40 and OX40L fusion protein treatment on the induction of protective Th2 responses and enteropathy following infection with the gastrointestinal nematode Trichinella spiralis. Treatment with an OX40-immunoglobulin (Ig) blocking fusion protein resulted in enhanced expulsion of the parasite and an increase in the accompanying mastocytosis, despite unaltered levels of Th2 cytokines. Furthermore, there was a delay in the villus atrophy and crypt hyperplasia usually associated with this infection. In contrast, levels of Th2 cytokines were greatly up-regulated in mice treated with an OX40L-Ig activating fusion protein, yet the expulsion of the parasite and the enteropathy were unaffected. Therefore, OX40 ligation potentiates the Th2 response without enhancing host protective immune responses, whereas blocking the OX40-OX40L interaction enhances host protection without promoting Th2 cytokine responses during Trichinella spiralis infection.

Trichinella spiralis: Macrophage activity and antibody response in chronic murine infection

The role of macrophages, their products, and the specific antibody response were examined during chronic Trichinella spiralis infection in BALB/c mice. Adult T. spiralis in intestines were detected from 5 to 20 dpi. Muscle larvae numbers peaked at 45 dpi and thereafter a reduction was noted. The highest numbers of macrophages in the peritoneal cavity of infected mice were obtained up to 30 dpi. The production of NO by macrophages in infected mice was suppressed at 5 dpi, and then NO release increased until 45 dpi. The levels of NO in plasma and urine were lower in infected mice during the entire experiment in comparison to control. The production of O 2 − in peritoneal macrophages was inhibited during the first two weeks after infection and then increased until 90 dpi. Circulating T. spiralis antigens in plasma and urine were detected from 5 to 30 dpi. Specific IgM and IgA in serum increased until 20 dpi. IgG, IgG 1, and IgG 2 levels in serum increased until 60 dpi.

Disruption of CD40-CD40 ligand pathway inhibits the development of intestinal muscle hypercontractility and protective immunity in nematode infection.

In our previous studies, we demonstrated that during Trichinella spiralis infection, T helper (Th) 2 cells contribute to the development of intestinal muscle hypercontractility and worm expulsion from the gut via STAT6. In addition, we have linked the altered muscle contractility to the eviction of the parasite and thereby to the host defense. However, the initial events linking infection to the development of muscle hypercontractility are poorly understood. In this study, we examined the contribution of CD40-CD40 ligand (CD40L) interaction in the development of intestinal muscle hypercontractility, in monocyte chemoattractant protein-1 (MCP-1) production, and in the Th2 response in CD40 ligand-deficient (CD40L -/-) mice infected with T. spiralis. Expulsion of intestinal worms was substantially delayed in CD40L -/- mice compared with the wild-type mice after T. spiralis infection. Consistent with delayed worm expulsion, there was a significant attenuation of intestinal muscle contractility in CD40L -/- mice. Infected CD40L -/- mice also exhibited marked impairment in the production of MCP-1, IL-4, IL-13, IgG1, IgE, and mouse mucosal MCP 1 (MMCP-1), and in goblet cell response. These results demonstrate that CD40-CD40 ligand interaction plays an important role in MCP-1 production, Th2 response, intestinal muscle hypercontractility, and worm expulsion in nematode infection. The present data suggest that the early events leading to the generation of Th2 response include CD40-CD40 ligand interaction, which subsequently influences the production of Th2 cytokines, most likely via upregulation of MCP-1.

A non‐classical type of alveolar macrophage response to Trichinella spiralis infection

Studies of arginase expression and activity in guinea pig alveolar macrophages during Trichinella spiralis infection, prompted by earlier observation of innate lung response to the parasite, showed the macrophages to express both activity and protein of arginase type I. In cultured macrophages part of the enzyme was found to be always released to the extracellular medium. Whereas BCG in vivo treatment, alone or preceded by T. spiralis infection, stimulated arginase activity, T. spiralis infection alone affected the enzyme distribution between intracellular and extracellular fractions, and properties (K(m) and V(max)), rather than total (intracellular + extracellular) activity, with TGF-beta apparently responsible for a part of the effect. Anti-TGF-beta antibody treatment of the animals influenced both arginase activation by Mn(2+) and dependence of the enzyme-catalysed reaction on pH. Whereas T. spiralis infection activated guinea pig alveolar macrophages by the type II macrophage activation, as indicated by constant arginase expression, associated with previously demonstrated lack of stimulation of nitric oxide production, BCG treatment invoked an alternative type of activation mechanism, reflected by stimulation of macrophage arginase, but not iNOS, activity.

Effect of viable or dead Lactobacillus casei organisms administered orally to mice on resistance against Trichinella spiralis infection.

The capacity of viable, dead Lactobacillus casei and supernatant from L. casei culture, administered by oral route, to induce resistance in mice against Trichinella spiralis infection was evaluated. The percentage of adult worm reduction in the intestine five days after T. spiralis infection as compared with the worm burden in the control group fluctuated between between 53.1 and 58% in mice treated with viable L. casei, while reductions in animals treated with dead lactobacilli or supernatant from L. casei culture were of 44 and 32.5% respectively. The percentage of larvae per gram of muscle tissue reductions, as compared with controls, obtained 30 days after infection ranged from 48.4 to 70.7% in rodents which ingested viable L. casei compared with the percentage reductions of 65.9 and 24% obtained respectively in mice treated with dead lactobacilli or with L. casei supernatant. The protective response observed in the present study may be explained on the basis of 1) lactobacilli colonization of the intestine, 2) macrophage processing of dead lactobacilli in local immune tissues and presentation of L. casei antigens to Th1 cells which, in turn, produced IL-2 to activate B cells and other T cells.

Detection of coproantigen in early trichinellosis.

Trichinellosis has become undoubtedly worldwide in distribution. Its diagnosis relies largely on the serodiagnostic procedures which are of great value but unfortunately miss the enteric phase. This could be a serious diagnostic problem in the absence of corresponding epidemiological data and typical symptoms and signs of the disease. In this study the possibility of coproantigen detection, as an early diagnostic aid in trichinellosis, was investigated in mice experimentally infected with Trichinella spiralis. A modified double sandwich ELISA was developed using polyclonal antibodies raised in rabbits and guinea pigs against larval somatic antigens. The first detection of coproantigen was as early as the first day post infection, gradually increasing to reach its peak on the seventh day and then decreasing to disappear completely on the third week post infection. Another test, the coagglutination test (Co-A) was used, and this test confirmed the previous results. The finding of this study suggest that the coproantigen detection could be exploited to confirm ongoing early Trichinella spiralis infection. This fast and easy to use diagnostic method should improve the early infection in human.

Epidemiological survey of Trichinella infection in some areas of Henan province.

During 1996-1998 epidemiological survey of domestic Trichinella spiralis infection and serological survey on human beings were carried out in Yanling, Xuchang counties and Luohe city. By the artificial digestion method, the positive rates of pork in market and mutton were 1.6% and 0.6% respectively. Meat samples of pigs from pig-farms, cats and dogs were all negative for Trichinella larvae. Trichinellosis infection levels in rats captured in peasant households and places around abattoirs were 0.5% and 4.1% respectively (P < 0.05). By ELISA (double-antibody) with excretion-secretion (ES) antigens of Trichinella larvae, the positive rates of antibodies against Trichinella in sera of peasants and professional drivers were 2.2% and 7.8% (P < 0.05). The positive rates of antibodies in pigs from pig-farms and from peasant households were 1% and 7% respectively (P < 0.05). The levels of anti-Trichinella antibodies in rats captured in peasant households and places close to abattoirs were 0% and 11.1% respectively. Trichinella spiralis larvae were found in the washing meat slop in abattoirs.

Interleukin-5 deficient mice exhibit impaired host defence against challenge Trichinella spiralis infections.

Enteric nematode infections are characterized by both peripheral and tissue eosinophilia. The cytokine interleukin (IL)-5 is considered a critical factor in the proliferation and recruitment of eosinophils, however, studies suggest it plays little role in host defence, at least during primary Trichinella spiralis infections. Less is known concerning its role in host defence or in the inflammatory response that develops against challenge infections with the same parasite. We examined these questions by infecting IL-5 deficient and wild-type mice, with T. spiralis parasites. Both strains expelled the primary infection by day 21. Forty days after the primary infection, we challenged the mice with a second T. spiralis infection and counted tissue eosinophils and worms in the intestine. While wild-type mice developed a large tissue eosinophilia, IL-5 deficient mice showed little increase in eosinophil numbers within the intestine. Throughout the challenge infection, significantly larger worm burdens were recovered from IL-5 deficient mice, and worm expulsion was also significantly slower (day 21) compared to wild-type mice (day 14). Thus, unlike in a primary infection, IL-5 is not only essential for the onset of intestinal eosinophilia, but also makes a significant contribution to enteric host defence during challenge T. spiralis infections.

Long-term effects of acute trichinella spiralis (T.sp) infection on substance P levels in NIH swiss mice

Long-term effects of acute trichinella spiralis (T.sp) infection on substance P levels in NIH swiss mice

Analysis of intestinal intraepithelial lymphocyte populations in experimental Trichinella spiralis infection of mice

The potential role of intestinal intraepithelial lymphocytes (i-IELs) in the generation of host protective immunity after helminth infection was investigated using the Trichinella spiralis (Owen, 1835)/mouse model. In this study we found a significant rise of TCRgamma(delta)+ i-IELs (P < 0.001) concurrent with the jejunal goblet cells (GC) hyperplasia in T. spiralis-infected C57BL mice on day 4 p.i. However, no direct relationship between the kinetics of the increase in TCRgamma(delta)+ i-IELs and T. spiralis expulsion was observed in infected mice. Taken together, these results implicate that gamma(delta) i-IELs probably perform a unique functions related to the regulation of the GC proliferation accompanying T. spiralis gut infection. As is known, these TCRgamma(delta)+ i-IELs may release mediators or growth factors that in turn influence GC differentiation. With the use of dexamethason (DEX), a potent anti-inflammatory agent which also induces apoptotic cell death in i-IELs, we have confirmed that the expulsion of T. spiralis from the mouse gut is accompanied by an inflammatory response. Indeed, the GC are clearly involved in these phenomena, apparently under the regulation by TCRgamma(delta)+ i-IEL-mediated responses, since DEX abrogated GC proliferation in T. spiralis-infected C57BL mice and subsequently augmented adult worm burden. Our data also show that the rejection of adult worms starts concurrently with a significant increase in TCRalpha(beta)+ and CD8+ i-IELs (P < 0.05 and P < or = 0.01, respectively), namely by day 7 p.i. At the same time, CD4+ cells significantly decreased (P < 0.05) in the intestinal epithelium of T. spiralis-infected, vs uninfected mice. These results may indicate that the TCRalpha(beta)+ and CD8+ i-IELs act as effectors of anti-T spiralis defence reactions. The implications of these findings for the potential role of intestinal intraepithelial CD8+ and TCRalpha(beta)+ cells in the pathogenesis of the intestinal lesions during T. spiralis gut infection are discussed.

Mucosal immunity against parasitic gastrointestinal nematodes.

The last two decades witnessed significant advances in the efforts of immunoparasitologists to elucidate the nature and role of the host mucosal defence mechanisms against intestinal nematode parasites. Aided by recent advances in basic immunology and biotechnology with the concomitant development of well defined laboratory models of infection, immunoparasitologists have more precisely analyzed and defined the different immune effector mechanisms during the infection; resulting in great improvement in our current knowledge and understanding of protective immunity against gastrointestinal (GI) nematode parasites. Much of this current understanding comes from experimental studies in laboratory rodents, which have been used as models of livestock and human GI nematode infections. These rodent studies, which have concentrated on Heligmosomoides polygyrus, Nippostrongylus brasiliensis, Strongyloides ratti/S. venezuelensis, Trichinella spiralis and Trichuris muris infections in mice and rats, have helped in defining the types of T cell responses that regulate effector mechanisms and the effector mechanisms responsible for worm expulsion. In addition, these studies bear indications that traditionally accepted mechanisms of resistance such as eosinophilia and IgE responses may not play as important roles in protection as were previously conceived. In this review, we shall, from these rodent studies, attempt an overview of the mucosal and other effector responses against intestinal nematode parasites beginning with the indices of immune protection as a model of the protective immune responses that may occur in animals and man.

Using heat shock proteins as indicators of the immune function in Wistar rats during a secondary Trichinella spiralis infection

The muscle, liver, brain and spleen tissues from Wistar rats with either a primary Trichinella spiralis infection alone, or reinfected 45 days after primary infection, were collected at Days 1, 7, 14, 20 and 27 post reinfection. They were then assayed for levels of four heat shock proteins (HSPs), i.e. hsp90, hsp70, hsp60 and hsp25. Detection and quantitation of the separate HSPs in tissue specimens were achieved using Western blot and image analysis technique, respectively. The results show that the elements affecting altered expression of rat organs’ HSP were ‘neutralized’ by resistance-related events in immunized rats. Thus, while rat organs exhibited varying HSP levels in primary infections [Martinez, J., Perez-Serrano, J., Bernadina, W., Rodriguez-Caabeiro, F., 1999. Parasitology 118, 202–209], there was, in reinfected versus primary-infected rats, no difference in test HSPs levels in any organ, and at any time within the time course of this study. We have interpreted the results by using the model that involves induction of anti- T.spiralis immunity during primary infection and (almost) complete removal of effectors of tissue injury (infective T.spiralis larvae and newborn larvae) during reinfection.

Effects of aging on resistance to Trichinellaspiralis infection in rodents exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

Immune function, including resistance to infection, decreases as humans and rodents age. We have shown that preinfection exposure of young (9–11 weeks) mice or rats to TCDD decreased resistance to Trichinella spiralis (Ts) infection, expressed as delayed onset or completion of parasite elimination and as increased muscle burdens of larvae. It has also been shown that aged mice express lower constitutive levels of resistance to Ts infection, compared to young adult animals. This study tested the hypothesis that the age-related decrease in constitutive levels of resistance to Ts infection exacerbates the decreased resistance to infection that follows TCDD exposure. This hypothesis addresses the concern that TCDD may pose a greater threat to the elderly than to the population at large. Animals were given a single oral dose of 1, 10, or 30 μg TCDD/kg, 7 days before infection. Eleven days later, young (≈10 weeks) control rodents had eliminated a greater proportion of the original parasite burden from the intestine than aged control animals. Nevertheless, parasite elimination was decreased by TCDD exposure only in young rodents. The effect of TCDD exposure on numbers of encysted larvae was evaluated only in rats. Increased larvae burdens occurred in young rats at 30 μg TCDD/kg and at 10 or 30 μg TCDD/kg in aged rats. Parasite-specific splenocyte and lymph node cell proliferation was suppressed following dioxin exposure in young mice; cells from aged mice were markedly less responsive to stimulation, yet less sensitive to TCDD exposure. The response to parasite antigens was not affected in aged rats exposed to TCDD, although elevated mitogen-driven B-cell proliferation was observed. These results indicate that age-related constitutive immunosuppression did not exacerbate TCDD-induced suppression of T-cell mediated adult parasite expulsion; rather, advanced age provided some degree of protection. On the other hand, a lower dose of TCDD was required in aged rats to suppress the combined humoral and cellular responses that limit the burden of encysted larvae, compared to young rats. These model-dependent results preclude acceptance or rejection of the tested hypothesis.