Nippostrongylus brasiliensis: effects of immunity on the pre-intestinal and intestinal larval stages of the parasite

Nippostrongylus brasiliensis: effects of immunity on the pre-intestinal and intestinal larval stages of the parasite. International journal for Parasitology4: 183–191. Migration of the pre-intestinal larval stages of N. brasiliensis was studied in rats undergoing either primary or challenge infections. In rats undergoing a primary infection, more than 67 percent of larvae successfully migrated from the skin to the oesophagus by 70 h after infection, and subsequently over 90 per cent of these larvae became established in the small intestine as sexually mature adults. In immune rats undergoing a second infection, 46 per cent of larvae completed migration to the oesophagus by 70 h and of these, only 1·6 per cent became established in the intestine to produce eggs. These inhibitory effects on the pre-intestinal and intestinal larval stages were even more pronounced in immune rats undergoing a third or fourth infection and in addition, there was a prolonged sojourn and substantial retention of larvae in their lungs. There was no evidence that the immune response had an adverse effect on oesophageal fourth stags larvae as these organisms (obtained from immune donors) were able to establish and develop to maturity when transferred per os to normal animals.Syngeneic transfer of immune mesenteric lymph node cells to normal recipients, caused expulsion of parasites from the intestine but failed to effect migration of pre-intestinal larval stages. The implications of these findings are discussed in the context of current knowledge of the mechanisms of immunity to helminths.     

Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis: Comparison of cell populations in parasite resistant and susceptible guinea-pigs

Handlinger J. H. and Rothwell T. L. W. 1981. Studies of the responses of basophil and eosinophil leucocytes and mast cells to the nematode Trichostrongylus colubriformis: comparison of cell populations in parasite resistant and susceptible guinea-pigs. Internationaljournal for Parasitology11: 67–70. Basophil and eosinophil leucocytes and mast cells in T. colubriformis resistant and susceptible guinea-pigs were compared. There were significantly more circulating and small intestinal eosinophils in the resistant guinea-pigs. Intestinal eosinophils increased in both groups following infection with T. colubriformis but after 10 days the count in susceptible animals had only reached the pre-infection count in the resistant group. Pre-infection intestinal mast cell counts in the two groups were similar. Mast cell counts in susceptible guinea-pigs did not change during the period of observation but almost doubled within seven days of infection in the resistant animals.     

Effect of host sex on passive immunity in mice infected with Nematospiroides dubius

Dobson C. & Owen M. E. 1978. Effect of host sex on passive immunity in mice infected with Nematospiroides dubius. International Journal for Parasitology8: 359–364. Female C₃H but not Quackenbush (Q) mice harboured fewer Nematospiroides dubius than male C₃H and Q mice. Both strains lost worms 21 days after infection. C₃H and Q mice became progressively immune to infection following 4 sequential doses of N. dubius larvae and showed a sex resistance to infection. Hypothymic nu/nu CBA Balb/c mice did not show these effects on N. dubius infection. The reciprocal transfer of male and female immune mesenteric lymph node cells (IMLNC) to syngeneic male and female recipients showed that the female environment enhanced the protective qualities of both male and female IMLNC but the male environment suppressed these effects. Gonadectomized male and female recipients of male and female IMLNC had levels of infection similar to the entire female recipients. Serum from immune female donor mice protected both male and female recipients better than immune serum from male donors, but female mice in each treatment group were better protected than male mice. Immune serum transferred greater levels of protection then IMLNC to recipient mice against N. dubius infections. These data are consistent with the conclusion that the male environment suppresses lymphocyte activity and the production of protective antibodies and additionally may depress the effectiveness of sensitized lymphocytes and antibodies in ejecting N. dubius. On the other hand the female environment does not appear to adversely affect the mobilization of the protective immune response and may enhance immune effector mechanisms in protecting mice against N. dubius infections.     

Vaccination against the nematode Trichostrongylus colubriformis. III. Some observations on factors influencing immunity to infection in vaccinated guinea-pigs

Rothwell T. L. W. 1978. Vaccination against the nematode Trichostrongylus colubriformis. III. Some observations on factors influencing immunity to infection in vaccinated guineapigs. International Journal for Parasitology8: 33–37. Guinea-pigs were protected against infection with T. colubriformis when soluble material extracted from fourth-stage larvae was administered by the subcutaneous, intradermal, intraperitoneal and intraduodenal but not oral routes. The level of immunity following vaccination by the various effective routes was similar. Mature animals were found to respond significantly better to vaccination than immature animals. Significant immunity was present 10 days after vaccination but higher levels were found after 20 and 40 days. A single dose of vaccine was as effective as three divided doses. Finally, it was found that the adjuvant aluminium hydroxide gel, but not B. pertussis vaccine or levamisole improved the level of immunity to infection which followed vaccination.     

The location of parasites within their hosts: The influence of host feeding and diet on the dispersion of adults of Nippostrongylus brasiliensis in the intestine of the rat

This paper is the first in a series to experimentally examine factors which determine the location of parasites within their hosts. Nippostrongylus brasiliensis is typically found one third of the way along the small intestine of the rat between days 7 and 12 of a primary infection. When rats were fasted for 2 days, N. brasiliensis became evenly distributed along the intestine and many individuals, mostly females, entered the caecum. Upon being fed again, the parasites were at their ‘normal site’ within 24 h. Experimental diets of α-cellulose, or simple dietary compounds caused the same re-distribution as did normal food. By sectioning the rat intestine when it was full of food and relating the dispersion of worms to the presence of intestinal contents, it was confirmed that N. brasiliensis is found amongst the intestinal contents of its host. The notion of a ‘site’ is critically discussed and the merit of ‘habitat’ is argued because the ‘site’ of N. brasiliensis would appear to be less a ‘place’ but rather a combination of environmental factors.     

Nippostrongylus brasiliensis: Infection decreases plasma butyrylcholinesterase activity in rats

Plasma butyrylcholinesterase (BChE) hydrolyzes ester-containing compounds such as succinylcholine, as well as acting as a scavenger against neurotoxic organophosphates (OPs). We previously found that Nippostrongylus brasiliensis infection makes rats more susceptible to OP toxicity by decreasing serum paraoxonase-1 (PON1) activity. In the present study, we examined the effects of N.brasiliensis infection on acetylcholinesterase (AChE) activity in plasma, red blood cells (RBCs), brain and diaphragm, as well as serum PON1 activity, in rats at day 7 after infection. N.brasiliensis infection significantly decreased plasma BChE and PON1 activities without significantly altering AChE activity in RBCs, brain and diaphragm. These results provide further insight into the unusual deleterious effects of intestinal nematode infections on body homeostasis.     

Expression of genes in gastrointestinal and lymphatic tissues during parasite infection in sheep genetically resistant or susceptible to Trichostrongylus colubriformis and Haemonchus contortus

Resistance to an acute gastrointestinal nematode (GIN) infection is dependent on the ability of the host to recognise the parasite and mount a protective Th2 response. It is hypothesised that lambs which are genetically susceptible to GIN will differentially up-regulate Th1-type genes and therefore remain susceptible to chronic parasitism compared with genetically resistant lambs which will differentially up-regulate Th2-type genes and clear the parasite infection. Two selection flocks, in which lines of Merino sheep produced lambs genetically resistant or susceptible to GIN, were acutely challenged once or thrice with either Haemonchus contortus or Trichostrongylus colubriformis. Faecal-egg counts (FECs), and plasma and tissue anti-parasite (H. contortus or T. colubriformis) antibody isotype responses showed that resistant animals challenged three times with T. colubriformis established a protective Th2 response (negligible FEC, IgG1 and IgE) whereas susceptible animals required multiple challenges to establish a significant IgG1 response despite FECs remaining high. Trichostrongylus colubriformis elicited a more pronounced host response than H. contortus. RNA extracted from tissues at the site of each parasite infection and associated lymph nodes were interrogated by microarray and quantitative PCR analyses to correlate host gene expression to FECs and antibody responses. The IFN-γ inducible gene cxcl10 was up-regulated in the susceptible line of the Trichostrongylus selection flock sheep after a tertiary challenge with the parasites H. contortus and T. colubriformis. However, a uniform pattern of genes was not up-regulated in resistant animals from both selection flocks during both parasite infections, suggesting that the mode of host resistance to these parasites is different, although some similarities in host susceptibility were apparent.     

Vaccination against the nematode Trichostrongylus colubriformis. II. Attempts to protect guinea-pigs with worm acetylcholinesterase.

Soluble material extracted from T. colubriformis fourth stage larvae was fractionated by membrane ultrafiltration, gel filtration and ion-exchange chromatography. The acetylcholinesterase (AChE) peak obtained by gel filtration protected guinea-pigs against infection but it was contaminated by worm allergen. However, there was no relationship between the AChE content of fractions obtained by membrane ultrafiltration and ion-exchange chromatography and their ability to stimulate protective immunity. Purified T. colubriformis AChE, prepared by ion-exchange chromatography and free from demonstrable allergen did not stimulate protective immunity whereas another fraction, containing less than one-thousandth the amount of AChE, was effective in doing so.     

Taenia crassiceps in the rat: transfer of immunity and immunocompetence with lymph node cells.

Using T. crassiceps infections of young AS₂ rats as a model system, it was shown that immunity can be transferred adoptively with lymph node cells, whereas serum from the same donors was ineffective. Normal adult rat lymph node cells also conferred immunocompetence on neonatal recipients. There was no correlation between antibody and elimination or persistence of metacestodes in infected rats. It is suggested that susceptibility of neonates to infection with this parasite is the result of functional immaturity of thymus-derived cells involved in cell-mediated immune responses rather than T-cell facilitation of antibody production.     

Protection against Nippostrongylus brasiliensis by adoptive immunization with immune thoracic duct lymphocytes

The protective capacities of different sources of immune lymphocytes against Nippostrongylus brasiliensis infection were examined. Thoracic duct lymphocytes (TDL) drained from donors on the tenth day of a primary infection (Day 10 TDL) conferred greater protection against adult worms established by larval infection than either mesenteric lymph node cells (MLNC) or TDL drained from hyperimmune donors. Day 10 TDL also conferred a high degree of protection against intraduodenally implanted “normal” and “damaged” worms. These results suggest that the different susceptibilities of “normal” and “damaged” worms to adoptive protection is a quantitative rather than a qualitative phenomenon. The results also emphasise that kinetic and dose-response experiments are important in evaluating the protective capacities of transferred cells.     

Investigations of 'transfer factor' activity in immunity to Ostertagia circumcincta and Trichostrongylus colubriformis infections in sheep.

Immunity was successfully transferred by ‘Transfer Factor’ prepared from leucocytes of two adult Scottish Blackface donor rams infected with O. circumcincta and T. colubriformis to 4-month-old susceptible Fin X Dorset lambs. The immunity was expressed by a significantly reduced faecal egg count and worm burden compared to challenged, untreated controls. The immunity was comparable to that produced in another group of lambs given an initial infection prior to challenge with both parasites.     

Nippostrongylus brasiliensis and Nematodirus battus: Changes in numbers and weight during the course of infection

Nematodirus battus has been shown to be subject to a “self-cure” mechanism when lambs 6 weeks of age are infected with 60,000 larvae. It is proposed that this self-cure phenomenon is an immune response similar to that which occurs in rats infected with Nippostrongylus brasiliensis. Changes in the weight of adult Nematodirus sp. and Nippostrongylus sp. occur over the period of an infection in their hosts. Females of both species from high-dose infections increased in weight up to that time postinfection where most adult worms were present, then decreased in weight with the onset of rejection from the host. Male Nematodirus sp. showed a similar pattern of weight change to that of females but male Nippostrongylus sp. maintained a steady weight throughout the infection. The consequences of these changes in weight are discussed with relevance to expression of enzyme activities of the nematodes on a weight of individual nematode basis.     

Surfactant Protein-D Is Essential for Immunity to Helminth Infection

Pulmonary epithelial cell responses can enhance type 2 immunity and contribute to control of nematode infections. An important epithelial product is the collectin Surfactant Protein D (SP-D). We found that SP-D concentrations increased in the lung following Nippostrongylus brasiliensis infection; this increase was dependent on key components of the type 2 immune response. We carried out loss and gain of function studies of SP-D to establish if SP-D was required for optimal immunity to the parasite. N. brasiliensis infection of SP-D-/- mice resulted in profound impairment of host innate immunity and ability to resolve infection. Raising pulmonary SP-D levels prior to infection enhanced parasite expulsion and type 2 immune responses, including increased numbers of IL-13 producing type 2 innate lymphoid cells (ILC2), elevated expression of markers of alternative activation by alveolar macrophages (alvM) and increased production of the type 2 cytokines IL-4 and IL-13. Adoptive transfer of alvM from SP-D-treated parasite infected mice into naïve recipients enhanced immunity to N. brasiliensis. Protection was associated with selective binding by the SP-D carbohydrate recognition domain (CRD) to L4 parasites to enhance their killing by alvM. These findings are the first demonstration that the collectin SP-D is an essential component of host innate immunity to helminths.     

Trichinella spiralis: Delayed rejection in mice concurrently infected with Nematospiroides dubius

The immune response of mice to the nematode Trichinella spiral's was markedly altered when the infection was superimposed upon an existing infection with Nematospiroides dubius. The expulsion of a primary infection of T. spiralis was delayed in such mice, and the worms persisted for at least 4 weeks longer than they did in control mice. The degree to which expulsion was suppressed was related to the number of N. dubius present. It would appear that both adult and larval stages of N. dubius can exert a suppressive effect, since the expulsion of T. spiralis was affected within days of a super-imposed (i.e., larval) N. dubius infection. When adult N. dubius were removed from mice 4 days before infection with T. spiralis, the mice expelled the latter parasite within the normal time, indicating that recovery from the suppressive effects of concurrent infection occurred rapidly. Concurrent infection with N. dubius appeared to affect both the afferent and efferent arms of the immune response to T. spiralis, since sensitization by, and memory of, prior infection were impaired and the expression of acquired immunity was inferior to that of controls.     

Perinatal Exposure to a Low Dose of Bisphenol A Impaired Systemic Cellular Immune Response and Predisposes Young Rats to Intestinal Parasitic Infection

Perinatal exposure to the food contaminant bisphenol A (BPA) in rats induces long lasting adverse effects on intestinal immune homeostasis. This study was aimed at examining the immune response to dietary antigens and the clearance of parasites in young rats at the end of perinatal exposure to a low dose of BPA. Female rats were fed with BPA [5 µg/kg of body weight/day] or vehicle from gestational day 15 to pup weaning. Juvenile female offspring (day (D)25) were used to analyze immune cell populations, humoral and cellular responses after oral tolerance or immunization protocol to ovalbumin (OVA), and susceptibility to infection by the intestinal nematode Nippostrongylus brasiliensis (N. brasiliensis). Anti-OVA IgG titers following either oral tolerance or immunization were not affected after BPA perinatal exposure, while a sharp decrease in OVA-induced IFNγ secretion occurred in spleen and mesenteric lymph nodes (MLN) of OVA-immunized rats. These results are consistent with a decreased number of helper T cells, regulatory T cells and dendritic cells in spleen and MLN of BPA-exposed rats. The lack of cellular response to antigens questioned the ability of BPA-exposed rats to clear intestinal infections. A 1.5-fold increase in N. brasiliensis living larvae was observed in the intestine of BPA-exposed rats compared to controls due to an inappropriate Th1/Th2 cytokine production in infected jejunal tissues. These results show that perinatal BPA exposure impairs cellular response to food antigens, and increases susceptibility to intestinal parasitic infection in the juveniles. This emphasized the maturing immune system during perinatal period highly sensitive to low dose exposure to BPA, altering innate and adaptative immune response capacities in early life.     

IL-22 Mediates Goblet Cell Hyperplasia and Worm Expulsion in Intestinal Helminth Infection

Type 2 immune responses are essential in protection against intestinal helminth infections. In this study we show that IL-22, a cytokine important in defence against bacterial infections in the intestinal tract, is also a critical mediator of anti-helminth immunity. After infection with Nippostrongylus brasiliensis, a rodent hookworm, IL-22-deficient mice showed impaired worm expulsion despite normal levels of type 2 cytokine production. The impaired worm expulsion correlated with reduced goblet cell hyperplasia and reduced expression of goblet cell markers. We further confirmed our findings in a second nematode model, the murine whipworm Trichuris muris. T.muris infected IL-22-deficient mice had a similar phenotype to that seen in N.brasiliensis infection, with impaired worm expulsion and reduced goblet cell hyperplasia. Ex vivo and in vitro analysis demonstrated that IL-22 is able to directly induce the expression of several goblet cell markers, including mucins. Taken together, our findings reveal that IL-22 plays an important role in goblet cell activation, and thus, a key role in anti-helminth immunity.     

The response of the regional lymph node of guinea-pigs to primary and challenge infection with the nematode, Trichostrongylus colubriformis

Responses characteristic of both cell-mediated immunity and the production of humoral antibodies occurred in the regional lymph node (mesenteric) of guinea-pigs following primary and challenge infection with the nematode Trichostrongylus colubriformis. In addition, depletion of lymphocytes in the paracortical areas and pronounced infiltration with basophil and eosinophil leucocytes were observed. All these changes were chronologically related to parasite rejection.     

Peripheral blood white cell responses during Angiostrongylus cantonensis infection in rats

Yono W. K. and Dobson C. 1984. Peripheral blood white cell responses during Angiostrongylus cantonensis infections in rats. Interntional Journal for Parasitology14: 207–211. Changes in white blood cell (WBC) populations and their proliferative responses to phytohaemagglutinin (PHA) and parasite antigens in vitro were studied in rats given one to three concurrent infections with Angiostrongylus cantonensis. WBC counts were elevated following infection; these changes were augmented following each successive reinfection. The WBC response could be partitioned into variations in the numbers of four major cell types. There was a loss of lymphocytes from the circulation after infection or reinfection followed by an increase in circulating lymphocytes when the parasite migrated to the lungs and matured. An eosinophilia was observed in all rats immediately after infection which was enhanced successively after each reinfection. The monocyte populations increased in a similar, but less obvious manner, to the eosinophil leucocytes. Neutrophil leucocytes increased after infection, but the numbers declined after reinfection. All rats given one to three infections showed a neutrophilia late in the experiment. A reversal in the neutrophil leucocyte-lymphocyte ratio was observed after each infection. A peak response in the proliferation of peripheral blood lymphocytes in vitro to PHA preceded and exceeded that stimulated by A. cantonensis antigen. These responses were interpreted as the dissemination of uncommitted thymus-dependent lymphocytes involved in the induction of antigen sensitized memory cells released following the protective immune reaction. The degree of lymphocyte responsiveness to mitogens correlated with the numbers of these cells circulating at each time interval. The relationships between in vitro lymphocyte responses and protective immunity in the rat against A. cantonensis are discussed.     

Effect of repeatedly sensitized bursal extract on the resistance of WLH chickens to experimental infection of Ancylostoma caninum larvae

Goyal P. K. and Johri G. N. 1982. Effect of repeatedly sensitized bursal extract on the resistance of WLH chickens to experimental infection of Ancylostoma caninum larvae. International Journal for Parasitology12: 245–249. Bursal extract from chickens, repeatedly sensitized with Ancylostoma caninum larvae and from normal nonsensitized donor WLH chickens were injected separately into experimental and control groups of isologous recipients of same age and weight. Extract from donors infected with repeatedly high dose (250 + 250 + 500) and low dose (125 + 125 + 250) of A. caninum larvae produced significantly greater acquired immunity in recipients compared to those which received nonsensitized (normal) extract. However, no significant difference was observed between the two experimental groups.     

Serum opsonins and the passive transfer of protection in Babesia rodhaini infections of rats

Serum opsonins and the passive transfer of protection in Babesia rodhaini infections of rats. International Journal for Parasitology4: 197–201. An investigation into the protective activity of serum from rats immune to B. rodhaini and the role played by opsonins in that activity was undertaken. One, three and six infections with B. rodhaini resulted in corresponding increases in the titre of specific protective antibody demonstrable by the administration of immune serum to rats. Drug control of infection resulted in a lower level of protective activity than that which developed when rats controlled infection unaided. Protective activity following recovery from a single drug controlled infection was undiminished 20 weeks after infection.Serum opsonins were detected in an in vitro culture system of normal rat peritoneal macrophages and these antibodies were specific for parasitized erythrocytes. It is suggested that opsonins were largely responsible for the protective effect demonstrated by assay in rats but that their importance, relative to other antibodies with a possible protective function, in the development of acquired immunity remains to be determined.