Effects of Trichinella spiralis infection on intestinal pathology in mice lacking interleukin-4 (IL-4) or intestinal trefoil factor (ITF/TFF3).

The nematode Trichinella spiralis induces pathological changes in the small intestine of the host, which are known to be controlled by immune and inflammatory mediators. The detail of this control has still to be completely understood. Mice deficient in interleukin 4 (IL-4) or in intestinal trefoil factor/trefoil family factor 3 (ITF/TFF3) were infected with T. spiralis and the resultant changes in the intestinal mucosa followed by quantifying numbers of mucosal mast cells, goblet cells, Paneth cells and by monitoring structural changes in villus length and crypt depth. Mice lacking IL-4 were unable to mount a normal protective response to infection, such that worm survival was increased. These mice failed to mount a mucosal mast cell response, but did make goblet cell and Paneth cell responses comparable to normal controls. Mice lacking ITF/TFF3 similarly made normal levels of goblet cell and Paneth cell responses. They also underwent profound changes in mucosal architecture, with marked villus atrophy and crypt hyperplasia. These results are discussed in relation to known patterns of T cell and cytokine control of protective immunity to T. spiralis. They suggest that increased numbers of goblet cell and Paneth cell are not, by themselves, required for protective immunity. ITF/TFF3 appears not to influence cellular responses and does not alter parasite-induced pathological changes in the small intestine.

High resolution mapping of chromosomal regions controlling resistance to gastrointestinal nematode infections in an advanced intercross line of mice.

Fine mapping of quantitative trait loci (QTL) associated with resistance to the gastrointestinal parasite Heligmosomoides polygyrus was achieved on F(6)/F(7) offspring (1076 mice) from resistant (SWR) and susceptible (CBA) mouse strains by selective genotyping (top and bottom 20% selected on total worm count in week 6). Fecal egg counts were recorded at weeks 2, 4, and 6, and the average was also analyzed. Blood packed cell volume in weeks 3 and 6 and five immunological traits (mucosal mast cell protease 1, granuloma score, IgG1 against adult worm, IgG1, and IgE to L4 antigen) were also recorded. On Chromosome 1 single-trait analyses identified a QTL with effects on eight traits located at about 24 cM on the F(2) mouse genome database (MGD) linkage map, with a 95% confidence interval (CI) of 20-32 cM established from a multitrait analysis. On Chromosome 17 a QTL with effects on nine traits was located at about 18 cM on the MGD map (CI 17.9-18.4 cM). Strong candidate genes for the QTL position on Chromosome 1 include genes known to be involved in regulating immune responses and on Chromosome 17 genes within the MHC, notably the Class II molecules and tumor necrosis factor.

Cellular and serological responses in resistant and susceptible mice exposed to repeated infection with Heligmosomoides polygyrus bakeri.

An experiment was carried out to compare the parasitological and immunological responses of SWR and CBA mice to trickle (repeated) infection with Heligmosomoides polygyrus. Male mice were given 125 L3 once per week and were killed in groups, together with naïve control mice, weekly until week 8. Worm burdens accumulated in CBA, stabilizing in week 5 in excess of 400 worms and remaining high until week 8. In contrast in SWR worm burdens peaked in week 3 at a mean worm burden of 129 and then fell sharply so that by week 6, despite continuing re-infection, no more worms were recovered from these mice. SWR mice showed a marked mast cell and mMCP-1 response, peaking in weeks 2-3, whereas in CBA mice these responses were slower, and even at their height in week 8 still less intense than those in SWR mice. Both strains responded initially with a very similar goblet cell response, which declined in SWR mice as worms were eliminated, but was sustained in CBA mice until week 8. Serum TNFalpha concentrations were higher in SWR mice throughout the experiment. Infection elicited strong serological responses against adult and L4 antigens in both SWR and CBA mice, involving all the isotypes tested (IgG1, IgA and IgE). Anti-L3 responses were examined only for IgG1. However, only two responses differed significantly between the strains: the IgE response to L4 antigens was more intense in SWR mice, and interestingly and unexpectedly, the IgG1 response to adult worm antigens was more intense in CBA mice. These results reflect the activation of predominantly Th2-driven effector mechanisms, that may be associated with host-protective immunity developing under the trickle infection protocol exploited in these experiments.

Mapping of chromosomal regions influencing immunological responses to gastrointestinal nematode infections in mice.

This paper reports the results of a genome-wide search for quantitative trait loci (QTL) influencing immunological responses to infection with the gastro-intestinal nematode parasite Heligmosomoides polygyrus in an F2 population created by crossing the resistant SWR and the susceptible CBA inbred mouse strains. Following infections, intestinal granuloma score at post mortem, mucosal mast cell protease 1, and IgE and IgG1 titres were recorded. The susceptible CBA mice had significantly higher IgG1, but significantly lower IgE, mucosal mast cell protease 1 and granuloma scores than SWR mice. Significant QTL were mapped to chromosomes 4, 11, 13 and 17 for granuloma score; chromosomes 12 and 17 for IgE; chromosome 10, 17 and 18 for IgG1 and chromosomes 1, 9, 10, 11, 17 and 18 for mucosal mast cell protease 1. Chromosomes 10, 11, 17 and 18 had QTL affecting more than one trait, and these are most likely to represent single QTL with multiple effects rather than multiple QTL. Some of these QTL map to regions known to harbour genes responsible for the induction of immunological responses to intestinal worms.

Concurrent infections with Trypanosoma brucei and Nippostrongylus brasiliensis in mice deficient in inducible nitric oxide.

Concurrent infection with Trypanosoma brucei (Tb) delays the normal protective responses of mice to the gastrointestinal parasite Nippostrongylus brasiliensis (Nb). The course of such infections was followed in mice genetically deficient in inducible nitric oxide synthase (INOS) to assess the role of nitric oxide (NO) in this effect. The time course of trypanosome infection in INOS deficient (INOS-/-) mice was similar to that in wild type (WT) and heterozygote (INOS+/-) mice but did not result in NO production. Although concurrent infection with Tb increased initial susceptibility to Nb in INOS-/- mice, the immune-mediated loss of N. brasiliensis and the associated decline in faecal egg output occurred more rapidly then in WT and INOS+/- littermates. Concurrent infection with trypanosomes markedly suppressed Concanavalin A (ConA)-induced in vitro proliferation of splenic lymphocytes in all groups, but had little effect on the responses of mesenteric node lymphocytes. Trypanosome infection was also associated with increased early release of interferon-gamma and reduced IL-5 from lymphocytes stimulated in vitro with ConA, but did not affect later release of IL-5. The overall similarity of proliferative and cytokine responses in WT, INOS+/- and INOS-/- mice suggest that the suppressive effects of T. brucei on N. brasiliensis infection do not simply reflect depressed lymphocyte responsiveness or altered cytokine profiles. NO appears to be involved in suppression only of the later phases of the host responses to Nb.

Chromosomal regions controlling resistance to gastro-intestinal nematode infections in mice.

Quantitative trait loci (QTL) associated with resistance to an intestinal worm in a well-defined murine model are described. These have been identified in an F(2) population derived from resistant (SWR) and susceptible (CBA) parental mouse strains infected with the gastro-intestinal nematode parasite Heligmosomoides polygyrus. Seven QTL located on six chromosomes are described, associated with components of the complex host response and the differential regulation of parasite survival and reproduction. The combined additive effects of the five significant QTL associated with worm survival (total worm count at necropsy) account for about 60% of the difference in worm count between the parental lines. The dominance effect for these five QTL are all in the direction of resistance, supporting the heterosis for resistance established from the mean worm count for the F(2) line relative to the parental lines. It is now possible to identify the comparative chromosomal regions of these QTL in livestock and humans and to consider the possibility of future improved control strategies. These may include breeding of resistant or tolerant livestock, development of vaccines, or identification of new anthelmintic drugs.

Nasal immunization with homogenate and peptide antigens induces protective immunity against Trichinella spiralis.

Mice were successfully immunized against the intestinal nematode Trichinella spiralis by intranasal administration of a 30-mer peptide antigen with cholera toxin B. Immunized mice developed antigen-specific serum immunoglobulin G1, intestinal immunoglobulin A, and a type 2-biased cytokine response. Intranasal immunization therefore generates the Th2-mediated responses required for immunity against intestinal parasites.

Helminths.

Helminths affect more than one quarter of the world's population, contributing significantly to socioeconomic problems in developing countries. Control is heavily dependent on chemotherapy, which can be cost-effectively targeted to school-age children, in whom combined drug treatments work well. Drug resistance, however, is a constant threat. Human behaviour significantly influences transmission. New infections or foci are frequently reported and tourism exposes non-endemic individuals to serious risks. Infection and pathology are strongly influenced by genetic factors, which are now being defined. Immune responses contribute to both protection and pathology. Clarification of these responses is providing opportunities for vaccination and for the modulation of immunopathology.

Intestinal helminthiasis and anaemia in youngsters from Matriz da Luz, district of Säo Lourenço da Mata, State of Pernambuco, Brazil

A group of youngsters (4-18 years old) in northeast Brazil was studied to stablish the prevalence of anaemia and intestinal parasitism, as well as to analyse the correlation between them. Two criteria were used to determine the state of anaemia, the level of haemoglobin and the mean of corpuscular volume. The first was considered a single criterion and the second an associated criteria, used in an attempt to correlate anaemia with iron deficiency. The prevalence of intestinal parasitism was 93 per cent while the prevalence of anaemia was 43.1 per cent and 16.1 per cent according to the criteria employed (single or associated respectively). Anaemia was significantly associated with both sex and age. No significant statistical difference was observed when the association was made between each parasite and anaemia even with those more related to anaemia.