Intestinal helminth infection enhances bacteria-induced recruitment of neutrophils to the airspace.

Intestinal helminth infections elicit Th2-type immunity, which influences host immune responses to additional threats, such as allergens, metabolic disease, and other pathogens. Th2 immunity involves a shift of the CD4+ T-cell population from type-0 to type-2 (Th2) with increased abundance of interleukin (IL)-4 and IL-13. This study sought to investigate if existing gut-restricted intestinal helminth infections impact bacterial-induced acute airway neutrophil recruitment. C57BL/6 mice were divided into four groups: uninfected; helminth-Heligmosomoides polygyrus infected; Pseudomonas aeruginosa infected; and coinfected. Mice infected with H. polygyrus were incubated for 2 weeks, followed by P. aeruginosa intranasal inoculation. Bronchial alveolar lavage, blood, and lung samples were analyzed. Interestingly, infection with gut-restricted helminths resulted in immunological and structural changes in the lung. These changes include increased lung CD4+ T cells, increased Th2 cytokine expression, and airway goblet cell hyperplasia. Furthermore, coinfected mice exhibited significantly more airspace neutrophil infiltration at 6 hours following P. aeruginosa infection and exhibited an improved rate of survival compared with bacterial infected alone. These results suggest that chronic helminth infection of the intestines can influence and enhance acute airway neutrophil responses to P. aeruginosa infection.

A Novel Non-invasive Method to Detect RELM Beta Transcript in Gut Barrier Related Changes During a Gastrointestinal Nematode Infection.

Currently, methods for monitoring changes of gut barrier integrity and the associated immune response via non-invasive means are limited. Therefore, we aimed to develop a novel non-invasive technique to investigate immunological host responses representing gut barrier changes in response to infection. We identified the mucous layer on feces from mice to be mainly composed of exfoliated intestinal epithelial cells. Expression of RELM-ß, a gene prominently expressed in intestinal nematode infections, was used as an indicator of intestinal cellular barrier changes to infection. RELM-ß was detected as early as 6 days post-infection (dpi) in exfoliated epithelial cells. Interestingly, RELM-ß expression also mirrored the quality of the immune response, with higher amounts being detectable in a secondary infection and in high dose nematode infection in laboratory mice. This technique was also applicable to captured worm-infected wild house mice. We have therefore developed a novel non-invasive method reflecting gut barrier changes associated with alterations in cellular responses to a gastrointestinal nematode infection.

Superimposed visceral leishmanial infection aggravates response to Heligmosomoides polygyrus.

BACKGROUND: Polyparasitism is the rule in all animal species, including humans, and has an important role in pathogenicity, diagnosis and control measures. Among them, co-infections by gastrointestinal helminths and protists are very prevalent under natural conditions but experimental infections are relatively scarce. Thus, despite the frequent association of visceral Leishmania infections and intestinal helminth parasitism the experimental co-infection has not been addressed. Heligmosomoides polygyrus, an intestinal nematode of mice, is related to other helminths causing important pathologies and is a model species for immunological studies. Mice are valuable experimental model for visceral leishmaniasis. METHODS: BALB/c mice infected with H. polygyrus (200 third-stage larvae, L3) were subsequently infected seven days later with Leishmania infantum (107 promastigotes) with the aim of determining the effect of the overinfection on the host response to the primary infection with the helminth. RESULTS: Overinfection with the protist did not affect the establishment rate of the nematode but induced a higher fecal egg output. Helminth burdens in co-infected animals were significant at the end of the experiment. Early unspecific immune suppression induced by the nematode in mesenteric lymph nodes was not switched by L. infantum infection. Co-infection elicited a higher serum antibody (IgG1) response against the helminth. CONCLUSIONS: Visceral leishmanial overinfection aggravated the early host response against primary infections with the intestinal helminth. This effect was evidenced by an increased longevity and higher production of non-protective antibodies.

Antibodies and coinfection drive variation in nematode burdens in wild mice.

Coinfections with parasitic helminths and microparasites are highly common in nature and can lead to complex within-host interactions between parasite species which can cause negative health outcomes for humans, and domestic and wild animals. Many of these negative health effects worsen with increasing parasite burdens. However, even though many studies have identified several key factors that determine worm burdens across various host systems, less is known about how the immune response interacts with these factors and what the consequences are for the outcome of within-host parasite interactions. We investigated two interacting gastrointestinal parasites of wild wood mice, Heligmosomoides polygyrus (nematode) and Eimeria spp. (coccidia), in order to investigate how host demographic factors, coinfection and the host's immune response affected parasite burdens and infection probability, and to determine what factors predict parasite-specific and total antibody levels. We found that antibody levels were the only factors that significantly influenced variation in both H. polygyrus burden and infection probability, and Eimeria spp. infection probability. Total faecal IgA was negatively associated with H. polygyrus burden and Eimeria spp. infection, whereas H. polygyrus-specific IgG1 was positively associated with H. polygyrus infection. We further found that the presence of Eimeria spp. had a negative effect on both faecal IgA and H. polygyrus-specific IgG1. Our results show that even in the context of natural demographic and immunological variation amongst individuals, we were able to decipher a role for the host humoral immune response in shaping the within-host interaction between H. polygyrus and Eimeria spp.

Production and analysis of immunomodulatory excretory-secretory products from the mouse gastrointestinal nematode Heligmosomoides polygyrus bakeri.

Heligmosomoides polygyrus bakeri (Hpb) infection in mice is a convenient model for studying the pathophysiology and immunology of gastrointestinal (GI) helminth infection. Hpb infection suppresses immune responses to bystander antigens and unrelated pathogens, and it slows the progression and modifies the outcome of immune-mediated diseases. Hpb-derived excretory-secretory (ES) products potently modulate CD4(+) helper T cell (TH) responses by inducing regulatory T cells, tolerogenic dendritic cells (DCs) and immunoregulatory cytokines. This observation has spiked interest in identifying the immunomodulatory molecules, especially proteins, in ES products from Hpb and other GI nematodes for development as novel therapies to treat individuals with immune-mediated diseases, such as inflammatory bowel diseases (IBDs). In this protocol, we describe how to (i) maintain Hpb in the laboratory for experimental infections, (ii) collect adult worms from infected mice to generate ES products and (iii) evaluate the modulatory effects of ES products on toll-like receptor (TLR) ligand-induced maturation of CD11c(+) DCs. The three major sections of the PROCEDURE can be used independently, and they require ∼6, 10 and 27 h, respectively. Although other methods use a modified Baermann apparatus to collect Hpb adult worms, we describe a method that involves dissection of adult worms from intestinal tissue. The protocol will be useful to investigators studying the host-parasite interface and identifying and analyzing helminth-derived molecules with therapeutic potential.

Contrasting patterns of structural host specificity of two species of Heligmosomoides nematodes in sympatric rodents.

Host specificity is a fundamental property of parasites. Whereas most studies focus on measures of specificity on host range, only few studies have considered quantitative aspects such as infection intensity or prevalence. The relative importance of these quantitative aspects is still unclear, mainly because of methodological constraints, yet central to a precise assessment of host specificity. Here, we assessed simultaneously two quantitative measures of host specificity of Heligmosomoides glareoli and Heligmosomoides polygyrus polygyrus infections in sympatric rodent hosts. We used standard morphological techniques as well as real-time quantitative PCR and sequencing of the rDNA ITS2 fragment to analyse parasite infection via faecal sample remains. Although both parasite species are thought to be strictly species-specific, we found morphologically and molecularly validated co- and cross-infections. We also detected contrasting patterns within and between host species with regard to specificity for prevalence and intensity of infection. H. glareoli intensities were twofold higher in bank voles than in yellow-necked mice, but prevalence did not differ significantly between species (33 vs. 18%). We found the opposite pattern in H. polygyrus infections with similar intensity levels between host species but significantly higher prevalence in mouse hosts (56 vs. 10%). Detection rates were higher with molecular tools than morphological methods. Our results emphasize the necessity to consider quantitative aspects of specificity for a full view of a parasites' capacity to replicate and transmit in hosts and present a worked example of how modern molecular tools help to advance our understanding of selective forces in host-parasite ecology and evolution.

Understanding the role of antibodies in murine infections with Heligmosomoides (polygyrus) bakeri: 35 years ago, now and 35 years ahead.

The rodent intestinal nematode H.p.bakeri has played an important role in the exploration of the host-parasite relationship of chronic nematode infections for over six decades, since the parasite was first isolated in the 1950s by Ehrenford. It soon became a popular laboratory model providing a tractable experimental system that is easy to maintain in the laboratory and far more cost-effective than other laboratory nematode-rodent model systems. Immunity to this parasite is complex, dependent on antibodies, but confounded by the parasite's potent immunosuppressive secretions that facilitate chronic survival in murine hosts. In this review, we remind readers of the state of knowledge in the 1970s, when the first volume of Parasite Immunology was published, focusing on the role of antibodies in protective immunity. We show how our understanding of the host-parasite relationship then developed over the following 35 years to date, we propose testable hypotheses for future researchers to tackle, and we speculate on how the new technologies will be applied to enable an increasingly refined understanding of the role of antibodies in host-protective immunity, and its evasion, to be achieved in the longer term.

Functional analysis of effector and regulatory T cells in a parasitic nematode infection.

Parasitic nematodes typically modulate T-cell reactivity, primarily during the chronic phase of infection. We analyzed the role of CD4-positive (CD4+) T effector (T(eff)) cells and regulatory T (T(reg)) cells derived from mice chronically infected with the intestinal nematode Heligmosomoides polygyrus. Different CD4+ T-cell subsets were transferred into naïve recipients that were subsequently infected with H. polygyrus. Adoptive transfer of conventional T(eff) cells conferred protection and led to a significant decrease in the worm burdens of H. polygyrus-infected recipients. Roughly 0.2% of the CD4+ T cells were H. polygyrus specific based on expression of CD154, and cells producing interleukin 4 (IL-4) and IL-13 were highly enriched within the CD154+ population. In contrast, adoptive transfer of T(reg) cells, characterized by the markers CD25 and CD103 and the transcription factor Foxp3, had no effect on the worm burdens of recipients. Further analysis showed that soon after infection, the number of Foxp3+ T(reg) cells temporarily increased in the inflamed tissue while effector/memory-like CD103+ Foxp+ T(reg) cells systemically increased in the draining lymph nodes and spleen. In addition, T(reg) cells represented a potential source of IL-10 and reduced the expression of IL-4. Finally, under in vitro conditions, T(reg) cells from infected mice were more potent suppressors than cells derived from naïve mice. In conclusion, our data indicate that small numbers of T(eff) cells have the ability to promote host protective immune responses, even in the presence of T(reg) cells.

The effects of host population density on the epidemiology of the trichostrongyle nematode Heligmosomoides polygyrus.

The present study considers the effect mouse population density on the fecundity, expressed as daily egg output per gram of faeces, and infectivity of the trichostrongyle nematode. Heligmosomoides polygyrus and in the field mouse (Apodemus sylvaticus) and H. p. bakeri in laboratory mouse (CD1). The higher host density resulted in an increased fecundity of H. polygyrus compared with medium and lower host densities. However, the number of H. p. polygyrus and H. p. bakeri recovered 30 days post-infection indicated an increase in worm recovery with increasing host population density. Overcrowding in a host density may affect susceptibility to infection as a result of stress-mediated immunodepression.

The role of lipid content in the infectivity of third-stage larvae of Heligmosomoides polygyrus.

The concurrent effects of aging on the lipid content of third-stage larvae (L3) of H.p. polygyrus and H.p. bakeri were described experimentally. It was shown that larval age was closely correlated with their infectivity. The infectivity of H. polygyrus in field and laboratory mice, as indicated by mean worm recovery, was significantly higher for one week old compared with 16 weeks old larvae. Image analysis has been used for the first time to quantify the lipid content of L3 of H. polygyrus with age. The proportion of lipid within infective larvae was reduced and their infectivity declined with age. It has also been found that larvae of H.p. polygyrus possess more lipid than H.p. bakeri suggesting that L3 larvae of H.p. polygyrus are physiologically different from those of H.p. bakeri and the additional lipid reserves assist in extending their survival time in the extremes of climatic conditions in the field.

[Susceptibility of the Chinese hamster (Cricetulus griseus) to parasitic infections. (1). Experimental infection with Nematospiroides (Heligmosomoides) dubius to the cortisone-treated Chinese hamster].

Chinese hamsters (Cricetulus griseus) were experimentally infected with Nematospiroides (Heligmosomoides) dubius. Though they were resistant to the infection of this parasite, they were found to become susceptible to it by the treatment with cortisone. The number of the worms in the intestine of the Chinese hamster and the number of the eggs oviposited by female worms were markedly affected by the doses of the cortisone. Egg oviposition of N. (H.) dubius ceased within 27 days post infection in the cortisone treated Chinese hamster, probably because of the expulsion of the worms. It was suggested that cortisone treatment controlled the infection of the Chinese hamster with N. (H.) dubius and the reproductive activity of this parasite.