Heligmosomoides polygyrus: decreased apoptosis in fast responder FVB mice during infection

Primary infection with Heligmosomoides polygyrus in some strains of mice is chronic although fast responder mouse strains eliminate the parasite in a short period of time. The reason for the differences is unknown. In this study apoptosis, proliferation, IL-2 and IL-6 production of mesenteric lymph node (MLN) and spleen cells in vitro from fast (FVB) and slow (C57Bl/6) responder mice were compared during H. polygyrus infection. FVB cells showed decreased apoptosis, more proliferation and more cytokine production than cells from C57Bl/6 mice during infection. At the beginning of infection in C57Bl/6 mice the apoptosis of CD4(+) but not CD8(+) cells significantly increased in MLN and spleen cell cultures. Apoptosis, when the first immune signal is given by infective larvae, might play an important role in the modulation of the response in slow responder mice.     

Early lymphocytic responses to Heligmosomoides polygyrus infections in mice

Responses to parasite antigens were studied in three strains of mice, BALB/c, CBA and NIH, during the initial phases of a primary infection with the intestinal nematode Heligmosomoides polygyrus. Changes in the rate of in vivo cell division were analysed in mesenteric lymph nodes and spleens during the phases of larval maturation and adult establishment, and related to changes in organ size and cellularity. The nature of the proliferating cell populations was also investigated by flow cytometry, carried out on cell suspensions prepared at the time when larval development was complete. The variation in the ability of the strains of mice to become resistant to a challenge infection was manifest as only slight differences in their initial responses to infection. All three strains showed an increase in 125I-iododeoxyuridine incorporation in their mesenteric lymph nodes and spleen, and an increase in B cell frequency over that of T cells in the draining lymph nodes. Although lymph node weight in NIH mice continued to rise over a 4 week period, the majority of responses measured were short lived, peaking 10 to 14 days after infection. The low responder status of CBA mice was thus reflected in a transient and relatively small enlargement of lymphoid tissues, but their early proliferative responses to antigen were similar in scale to those of responder strains.     

The microbial environment and intestinal nematode infections of Heligmosomoides polygyrus in laboratory mice

The difficulty of establishing primary infections of Heligmosomoides polygyrus (= Nematospiroides dubius) in ASH/CSI mice in the Laboratory Animal House at Royal Holloway and Bedford New College during a recent autumn and spring period was associated with a syndrome of worm distortion, together with zero or low worm establishment and reduced fecundity (eggs/female worm). The eggs produced were non-viable and the egg capsule comprised a rumpled lipid and ruptured chitin layer. The egg size and peaks of egg production were also reduced and the total egg output ceased entirely by day 28 post-infection in male mice. The syndrome was repeated when control LACA mice harbouring 'normal' infections of H. polygyrus were housed on the same source of peat bedding material as the ASH/CSI mice. An increase in H. polygyrus egg production in ASH/CSI mice, removed from the peat or treated with 0.04% oxytetracycline hydrochloride suggested that the cause of the syndrome was microbial in origin. A microbiological assay of the peat, which was the common denominator of all syndrome infections, revealed an abundance of chitinase secreting species of bacteria (Bacillaceae). Bacterial chitinase was therefore likely to rupture the chitin layer of the egg capsule producing nonviable eggs and either abnormal or no larvae. Preliminary in vitro studies using chitinase from Streptomyces griseus indicated that the hatching success of eggs of H. polygyrus was reduced as the concentration of chitinase increased.     

The dynamics of trickle infections with Heligmosomoides polygyrus in syngeneic strains of mice.

NIH, CBA, SWR and C57B1/10 mice were repeatedly infected with Heligmosomoides polygyrus, using doses of 10-50 larvae at frequencies of 2-16 days. NIH and SWR mice regulated the worm burdens at a stable dose-dependent level for a period of several weeks, following which expulsion occurred and immunity to subsequent re-infection was established. This regulation did not occur in CBA or C57B1/10 mice, and was inhibited by cortisone treatment. Evidence was found to suggest that regulation is the result of an immune response directed against the late larval stages of the parasite, shortly after their emergence into the lumen of the gut. The frequency of infection was an important factor in determining the course of infection. Frequently infected mice expelled the parasites more rapidly than mice infected with the same total number of larvae in fewer less frequent doses.     

Heligmosomoides polygyrus (Nematoda): the dynamics of primary and repeated infection in outbred mice

The population dynamics of Heligmosomoides polygyrus were studied in outbred male MF1 mice subject either to primary or repeated experimental infection. Little variability in susceptibility was observed between mice, but heterogeneity increased with both duration and intensity of primary infection; this result indicates that there are differences in parasite survival between hosts. The rate of parasite-induced host mortality was 4 X 10(-4) per parasite per host per parasite lifespan. The mortality rates of male and female larvae during their development in the intestinal wall were estimated as 0.033 and 0.021 per parasite per day respectively, and estimates of the expected lifespans of the adult male and female parasites in primary infection of 11.22 and 9.92 weeks were obtained. Approximately 40% of female worms were observed in copula at any one time, although this proportion was significantly depressed in hosts harbouring fewer than 50 parasites and during the first four weeks of infection. Parasite fecundity was markedly age-dependent; each female worm produced approximately 31,000 eggs during its lifespan. No density dependence in either worm survival or fecundity in primary infection was apparent. The only detectable effect of worm density was in association with spatial distribution in the intestine; high levels of infection were associated with a posterior shift in the location of a proportion of the parasite population. Characterization of the dynamics of primary infection allowed predictions to be made about the expected dynamics of repeated infection. The comparison of predicted results and observed data revealed unequivocal epidemiological evidence for the density-dependent regulation of parasite population growth during repeated infection, affecting both parasite survival and parasite fecundity. The results also demonstrated the existence of two types of host individual in which the dynamics of repeated infection were markedly different. It is concluded that immunological differences between mice (possibly under genetic control) may be responsible for the observed effects; approximately 25% of MF1 mice seem unable to generate any protective immunity against H. polygyrus, whereas 75% become almost completely refractory to reinfection. This experimental system could be used for quantitative investigation of the impact of acquired immunity and genetic heterogeneity on helminth population dynamics. Both are of obvious relevance with respect to the control of infections of medical and veterinary significance.     

Diet texture modifies outcome of a primary infection with Heligmosomoides polygyrus (nematoda) in mice.

To determine if dietary texture altered the establishment, survival and reproduction of Heligmosomoides polygyrus during a primary infection, commercial mouse chow (Purina Chow) was fed in either pelleted or powdered form to 2 groups of infected BALB/c mice, and a semipurified, biotin-fortified, egg-white-based diet was provided in powdered form to a third group of mice. Diet texture (powdered vs. pelleted) modified parasite establishment, as evidenced by higher worm recovery 6 days postinfection (PI) in both groups of mice fed powdered diets compared with the group fed the pelleted diet, but diet texture had no detectable effect on net or per capita egg production or on day 30 worm survival. However, almost twice as many worms were recovered from mice fed the semipurified, powdered diet than those fed either textural formulation of the commercial mouse chow on day 30 PI, indicating that a dietary component in the semipurified diet, such as the single fiber source cellulose, facilitated parasite survival, or that other ingredients in the commercial mouse chow, perhaps the more complex fiber components, reduced worm survival, or both. We conclude that dietary texture influences parasite establishment and that specific fibers that change texture can individually and independently modify H. polygyrus survival.     

Primary infections with Babesia microti are not prolonged by concurrent Heligmosomoides polygyrus

Seven experiments were carried out to test the hypothesis that concurrent infection with the chronic and immunomodulatory intestinal nematode parasites, Heligmosomoides polygyrus, and the piroplasm, Babesia microti, would result in more intense and long-lasting infections with the hemoprotozoan. However, despite variations in the experimental protocols (different mouse strains, varying levels of infection and different intervals between infection with the two species) a significantly higher B. microti parasitaemia was detected on only one occasion, and a significantly lower parasitaemia on two occasions, relative to control mice. In none of our experiments was the duration of infection prolonged. We conclude that the presence of H. polygyrus does not interfere markedly with the host's ability to mount a protective response against B. microti and hence season-dependent peaks of abundance of H. polygyrus in wild rodents are unlikely to present a particular threat to human communities by providing a greater reservoir of infection with B. microti in wild rodents than at other times of the year.     

Trypanosoma musculi with Trichinella spiralis or Heligmosomoides polygyrus: concomitant infections in the mouse

Inbred mice infected with Trypanosoma musculi displayed wide variations in peak blood parasitemia. The most susceptible mice were C3H and A strain, while Balb/c, C57B1/6, and the related congenic B10 strains were the most resistant. The effect of an intestinal infection with either Trichinella spiralis or Heligmosomoides polygyrus on proliferation of T. musculi was investigated. T. spiralis infections given at the same time or up to 45 days before a T. musculi infection always caused an increase in blood parasitemia in C3H mice. Maximum increases were observed when T. spiralis infections preceded T. musculi by 5-10 days. In all mouse strains examined, dual infections increased maximum parasitemia by two- to four-fold, regardless of the degree of resistance of that mouse strain to either T. musculi or T. spiralis. This suggested that the immunological "cost" of a T. spiralis infection was the same for strains that were strong or weak responders to a primary infection with T. spiralis. In contrast, infection with H. polygyrus did not promote T. musculi parasitemia over the level of a single infection. The increase in blood parasitemia in T. spiralis-infected mice was largely due to the intestinal adult worm, but migratory larvae and mature muscle larvae also stimulated increased parasitemias. The increase in parasitemia was proportionate to the dose of T. spiralis, and the sex of the host did not affect the blood trypanosome level.     

Glutamine and asparagine synthesis in the nematodes Heligmosomoides polygyrus and Panagrellus redivivus

Low levels of glutamine synthetase were demonstrated in Panagrellus redivivus and Heligmosomoides polygyrus. Asparagine synthetase was detected in P. redivivus but activity was too low to be detected in H. polygyrus.     

Heligmosomoides polygyrus: inoculum size and glucose, ion, and gas fluxes in the small intestine of mice

Female CDI mice were inoculated with 10, 50, 100, 250, or 500 larvae of Heligmosomoides polygyrus. At Days 7, 9, and 12 after infection, the anterior third of the small intestine was perfused using an in vivo technique. The distribution of worms in the mouse intestine was determined after 7, 9, and 12 days. All worms that were recovered were from the proximal half of the small intestine. When compared to uninfected controls, there was a significant increase (+56%) in glucose absorption of the small intestine at Day 7 after infection with inocula of 50 and 100 larvae; at Day 9, glucose absorption was significantly increased with a 10-larvae inoculum. A decrease in glucose absorption occurred at Days 7 and 9 after infection with a 500-larvae inoculum. Net water absorption was significantly increased (+183%) with the 50- and 100-larvae inocula at Day 7, but was significantly reduced at Day 9 after infection with the 50-, 100-, 250-, and 500-larvae inocula. Both Cl- and Na+ absorption were significantly increased with the 50-, 100-, and 250-larvae inocula at Day 7 after infection; at 9 and 12 days, there was significant net secretion of both ions. In control mice, there was net secretion of K+, while with the 50-, 100-, and 250-larvae inocula on Day 7 there was significant net absorption of K+ ions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heligmosomoides polygyrus: effect of exogenous steroid hormones on egg output in vitro

The effect of exogenous steroid hormones on the egg output of Heligmosomoides polygyrus (Nematoda: Trichostrongylidae) was examined in vitro. Using worms raised in female mice, it was found that estradiol, testosterone, and cortisone each significantly decreased egg output. Although similar trends were found using H. polygyrus raised in male mice, none of the decreases found was significant. No significant differences were found with ecdysone or progesterone treatments using worms from female or male mice. Treatment of worms with cortisone did not significantly affect retention of eggs within the uterus of H. polygyrus. Titration of the effect of cortisone on egg output indicated that levels of reduction were significant for concentrations of 5.6 x 10(-6) M to 5.6 x 10(-3) M in worms from female mice and for concentrations of 5.6 x 10(-8), x 10(-7), x 10(-5) and x 10(-3) in worms from male mice. Radioisotope labelling experiments showed incorporation of 3H-corticosterone in the nucleus of intestinal cells of H. polygyrus suggesting that its effect on egg production may be via a modulatory effect on the intestinal cells.     

Heligmosomoides polygyrus (=Nematospiroides dubius): suppression of antibody response to orally administered sheep erythrocytes in infected mice.

Mice infected with 200 to 300 Heligmosomoides polygyrus had reduced serum hemagglutinin titers following a series of oral inoculations of sheep erythrocytes (SRBC) when compared to similarly inoculated uninfected mice. Study of antibody-producing cells by the indirect hemolytic plaque technique demonstrated a low splenic response to oral immunization in which IgA predominated. No alteration was evident in the proportions of antibody-containing cells in the different Ig classes with infection. Comparison of the immune response to oral and intraperitoneal routes of SRBC inoculation in infected and uninfected mice demonstrated a similar reduction in antibody titer with both routes of inoculation, although immunosuppression following intraperitoneal inoculations was not consistantly observed. The data are discussed in relation to the influence of the helminth infection on intestinal immune response and systemic immune response.     

An ultrastructural and histochemical study of oogenesis in the trichostrongylid nematode Heligmosomoides polygyrus

Oogenesis in trichostrongylids has been examined for the first time in a light and electron microscopic investigation of Heligmosomoides polygyrus. The female reproductive tract is a single straight tube containing small oogonia (6 micron in diameter), which are arranged in a rosette pattern around a central rachis at the anterior end of the tract. Developing oocytes separate from the rachis and pass posteriorly in single file down the growth zone. Oocytes increase rapidly in volume due to the accumulation of cytoplasmic inclusion granules. These granules are of 3 types. Type 1 granules are amorphous and probably consist primarily of lipoprotein. Type 2 granules are large lipid inclusions and type 3 granules are electron-dense lipoprotein yolk bodies, which are probably used for energy reserves in the developing embryo. Histochemical studies show a more intense reaction for DNA in the nuclei of oogonia than in the nuclei of oocytes. There is a strong reaction for RNA in the nucleoli and in the cytoplasm of oogonia and oocytes. Ultrastructural studies indicate that this RNA is probably in the form of rRNA in the abundant ribosomes. Mature oocytes are cylindrical (60 X 70 micron), have a distinct nucleus with nuclear pores, and the cytoplasm is filled with inclusion granules and ribosomes but contains only small amounts of glycogen. Prior to fertilization the plasma membrane of oocytes acquires a flocculent coat. These oocytes contain 6 distinct bivalent chromosomes in diakinesis. Thus the major changes that occur in developing germ cells are 2-fold: nuclear changes that prepare the chromosomes for fertilization by initiating reduction division, and cytoplasmic changes that involve the synthesis and storage of inclusion granules.     

Heligmosomoides polygyrus: influence of infection on lymphocyte subpopulations in mouse mesenteric lymph nodes

The immune response to a primary infection of Heligmosomoides polygyrus (Nematospiroides dubius) was studied by flow cytometry in three strains of mice, BALB/c, CBA, and NIH. The chief feature of the response was a pronounced increase, during the first week, in the proportion of B lymphocytes in the mesenteric lymph nodes. All three strains also showed an increase in lymph node cellularity, although this was delayed in NIH and CBA mice. Total B cell numbers thus also increased, particularly in the BALB/c and NIH strains but only in the latter was this response maintained throughout the 4-week study. Although the early changes in B cell frequency were similar in all three strains, B cell responses were greatest in BALB/c mice, and most prolonged in NIH, when they persisted into the adult phase of the infection. These features distinguished them from CBA mice, and could be associated with known variations in resistance to challenge infections. An increase in T cell numbers was delayed in comparison with the changes in the B cell population, and the ratio of 'helper' to 'suppressor/cytotoxic' T cells remained more or less constant in all three strains. There was thus no evidence for an increase in the frequency of suppressor T cells in any strain of mouse.     

The relative involvement of Th1 and Th2 associated immune responses in the expulsion of a primary infection of Heligmosomoides polygyrus in mice of differing response phenotype

T helper cell (Th1 and Th2) associated responses were examined following a primary infection with the gastrointestinal nematode Heligmosomoides polygyrus in five inbred strains of mice with different resistance phenotypes. Levels of (i) mast cell protease, (ii) specific IgE, (iii) nitric oxide and (iv) specific IgG2a, as markers of Th2 and Th1 associated responses, respectively, were determined in sera and intestinal fluids and correlated with worm burdens. The "fast" responder (resistant) strains SWR and SJL produced strong Th2 and Th1 associated responses respectively in a mutually exclusive fashion. The F1 hybrid (SWRxSJL) F1, showed rapid expulsion of the parasite and expressed both intense Th1 and Th2 responses, suggesting synergism between Th1 and Th2 activity in these mice. The results indicate that both Th2 and Th1 responses operate in mice following a primary infection with H. polygyrus and that each Th response may be involved to a greater or lesser degree within certain strains. Resistance to H. polygyrus was found to correlate only to the intensity of either the gut-associated mastocytosis or nitric oxide production in these strains but not to either specific IgE or IgG2a titres. Chronic infections in the "slow" response phenotype mouse strains CBA and C57BL/10, were associated with both poor Th2 and poor Th1-associated responses attributed to a general parasite-mediated immunosuppression of the host immune response to infection.     

Heligmosomoides polygyrus (=Nematospiroides dubius): the development of self-cure and/or protection in several strains of mice.

Strains of outbred (ICR/CD1 and S--W) and inbred (BALB/C and C57BL/6) mice vaccinated subcutaneously (SQ) with 500, 1,000, or 2,000 exsheathed Heligmosomoides polygyrus larvae developed varying levels of protection upon subsequent oral challenge with larvae. In contrast, the inbred C3H/HEJ strain failed to develop protection at any dosage level tested. ICR/CD1 mice vaccinated intraperitoneally with exsheathed larvae developed a high level of resistance but exhibited extensive adhesions of the viscera. When ensheathed larvae were used for vaccination, ICR/CD1 mice developed a moderate level of protection; but 1% of the vaccine dose was recovered in the intestine as adult stages. Both the inbred and outbred strains given multiple oral infections developed a protection response similar to that strain's response following parenteral vaccination. The specificity of this protection was demonstrated using various complex foreign antigens. In contrast, the self-cure response was observed only in the S--W strain.