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Gastrointestinal helminth infection still constitutes a major public health issue, particularly in the developing world. As these parasites can undergo a large part of their lifecycle within the intestinal tract the host has developed various structural and cellular specializations at the epithelial barrier to contend with infection. Detailed characterization of these cells will provide important insights about their contributions to the protective responses mediated against helminths. Here, we discuss how key components of the intestinal epithelium may function to limit the initial establishment of helminths, and how these cells are altered during an active response to infection., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Increasing evidence suggests that intestinal helminth infection can alter intestinal microbial communities with important impacts on the mammalian host. However, all of the studies to date utilize different techniques to study the microbiome and access different sites of the intestine with little consistency noted between studies. In the present study, we set out to perform a comprehensive analysis of the impact of intestinal helminth infection on the mammalian intestinal bacterial microbiome. For this purpose, we investigated the impact of experimental infection using the natural murine small intestinal helminth, Heligmosomoides polygyrus bakeri and examined possible alterations in both the mucous and luminal bacterial communities along the entire small and large intestine. We also explored the impact of common experimental variables including the parasite batch and pre-infection microbiome, on the outcome of helminth-bacterial interactions. This work provides evidence that helminth infection reproducibly alters intestinal microbial communities, with an impact of infection noted along the entire length of the intestine. Although the exact nature of helminth-induced alterations to the intestinal microbiome differed depending on the microbiome community structure present prior to infection, changes extended well beyond the introduction of new bacterial species by the infecting larvae. Moreover, striking similarities between different experiments were noted, including the consistent outgrowth of a bacterium belonging to the Peptostreptococcaceae family throughout the intestine., (Copyright © 2019 Australian Society for Parasitology. Published by Elsevier Ltd. All rights reserved.)

Objectives: We aimed to analyze the effect of a protein-deficient diet on mucosal and systemic immunity during a Trichinella spiralis infection., Methods: Two groups of weaning Wistar rats received a protein-deficient diet (6.5% casein) and the other two groups received a control diet (20% casein). After 10 d, one group of each diet was infected (PD I and C I ) with muscle larvae (infecting stage). Food intake and body weight were assessed over time. Blood eosinophils counts, antibodies in serum, and tissue extracts were assessed at different days postinfection. Histologic studies were done in the lungs and intestines, and adult worm (AW) fecundity index score and muscle parasite burden were determined., Results: Food and protein intake were lower in PD I than in C I. Body weight was lower in PD I than in a non-infected protein-deficient diet. Eosinophils counts were lower in PD I than in C I. Total and specific antibodies were lower in PD I than C I. PD I had a reduced number of mast and goblet cells in the lungs and intestines compared with C I. The persistence of AW in the intestines and migrant larvae at the lungs was longer in PD I than in C I. . The AW fecundity index score was higher in PD I than in C I . Finally, PD I evidenced a higher muscular parasite burden than C I ., Conclusions: Protein deficiency affects the mucosal and systemic immune response to Trichinella spiralis and delays the expulsion and increases the fecundity index score of AW, which leads to a higher parasite burden in the muscles., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Cryptosporidium infection leads to acute diarrhea worldwide. The development of cryptosporidiosis is closely related to the immune status of its host, affecting primarily young ruminants, infants, and immunocompromised individuals. In recent years, several studies have improved our knowledge on the immune mechanisms responsible for the control of the acute phase of the infection and have highlighted the importance of innate immunity. The parasite develops in the apical side of intestinal epithelial cells, giving these cells a central role, as they are both the exclusive host cell for replication of the parasite and participate in the protective immune response. Epithelial cells signal the infection by producing chemokines, attracting immune cells to the infected area. They also actively participate in host defense by inducing apoptosis and releasing antimicrobial peptides, free or incorporated into luminal exosomes, with parasiticidal activity. The parasite has developed several escape mechanisms to slow down these protective mechanisms. Recent development of several three-dimensional culture models and the ability to genetically manipulate Cryptosporidium will greatly help to further investigate host-pathogen interactions and identify virulence factors. Intestinal epithelial cells require the help of immune cells to clear the infection. Intestinal dendritic cells, well known for their ability to induce and orchestrate adaptive immunity, play a key role in controlling the very early steps of Cryptosporidium parvum infection by acting as immunological sentinels and active effectors. However, inflammatory monocytes, which are quickly and massively recruited to the infected mucosa, seem to participate in the loss of epithelial integrity. In addition to new promising chemotherapies, we must consider stimulating the innate immunity of neonates to strengthen their ability to control Cryptosporidium development. The microbiota plays a fundamental role in the development of intestinal immunity and may be considered to be a third actor in host-pathogen interactions. There is an urgent need to reduce the incidence of this yet poorly controlled disease in the populations of developing countries, and decrease economic losses due to infected livestock., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The apicomplexan parasite Cryptosporidium causes cryptosporidiosis, a diarrheal disease that can become chronic and life threatening in immunocompromised and malnourished people. There is no effective drug treatment for those most at risk of severe cryptosporidiosis. The disease pathology is due to a repeated cycle of host cell invasion and parasite replication that amplifies parasite numbers and destroys the intestinal epithelium. This study aimed to better understand the Cryptosporidium replication cycle by identifying molecules that trigger the switch from invasive sporozoite to replicative trophozoite. Our approach was to treat sporozoites of Cryptosporidium parvum and Cryptosporidium hominis, the species causing most human cryptosporidiosis, with various media under axenic conditions and examine the parasites for rounding and nuclear division as markers of trophozoite development and replication, respectively. FBS had a concentration-dependent effect on trophozoite development in both species. Trophozoite development in C. parvum, but not C. hominis, was enhanced when RPMI supplemented with 10% FBS (RPMI-FBS) was conditioned by HCT-8 cells for 3h. The effect of non-conditioned and HCT-8 conditioned RPMI-FBS on trophozoite development was abrogated by proteinase K and sodium metaperiodate pretreatment, indicating a glycoprotein trigger. Cryptosporidium parvum and C. hominis trophozoite development also was triggered by Gal-GalNAc in a concentration-dependent manner. Cryptosporidium parvum replication was greatest following treatments with Gal-GalNAc, followed by conditioned RPMI-FBS and non-conditioned RPMI-FBS (P<0.05). Cryptosporidium hominis replication was significantly less than that in C. parvum for all treatments (P<0.05), and was greatest at the highest tested concentration of Gal-GalNAc (1mM)., (Copyright © 2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

To date, three Entamoeba spp. (E. suis, zoonotic E. polecki and E. histolytica) have been identified in pigs, but their pathogenicity and molecular classification have not been fully determined. Examination and pathological analysis of pigs (n=3) with diarrhoea was conducted and revealed the presence of Entamoeba organisms. We performed a genetic analysis of the isolate using the small-subunit ribosomal RNA (SSU rRNA) gene region to identify the species. A severe ulcerative colitis was observed histopathologically with inflammatory cells, including macrophages and neutrophils, infiltrating the mucous membranes of the cecum and colon. Many Entamoeba trophozoites were found at the erosion site or at ulcerative lesions. Pathogenic viruses or bacteria were not detected. The SSU rRNA sequence of the Entamoeba isolate was found to be completely homologous to that of E. polecki subtype 3., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The molecular and cellular mechanisms leading to immune protection against coccidiosis are complex and include multiple aspects of innate and adaptive immunities. Innate immunity is mediated by various subpopulations of immune cells that recognize pathogen associated molecular patterns (PAMPs) through their pattern recognition receptors (PRRs) leading to the secretion of soluble factors with diverse functions. Adaptive immunity, which is important in conferring protection against subsequent reinfections, involves subtypes of T and B lymphocytes that mediate antigen-specific immune responses. Recently, global gene expression microarray analysis has been used in an attempt to dissect this complex network of immune cells and molecules during avian coccidiosis. These new studies emphasized the uniqueness of the innate immune response to Eimeria infection, and directly led to the discovery of previously uncharacterized host genes and proteins whose expression levels were modulated following parasite infection. Among these is the IL-17 family of cytokines. This review highlights recent progress in IL-17 research in the context of host immunity to avian coccidiosis., (Copyright © 2013. Published by Elsevier Ltd.)

Objective: This study investigated the role of L-arginine supplementation to undernourished and Cryptosporidium parvum-infected suckling mice., Methods: The following regimens were initiated on the fourth day of life and injected subcutaneously daily. The C. parvum-infected controls received L-arginine (200 mmol/L) or phosphate buffered saline. The L-arginine-treated mice were grouped to receive NG-nitro-arginine methyl ester (L-NAME) (20 mmol/L) or phosphate buffered saline. The infected mice received orally 10(6) excysted C. parvum oocysts on day 6 and were euthanized on day 14 at the infection peak., Results: L-arginine improved weight gain compared with the untreated infected controls. L-NAME profoundly impaired body weight gain compared with all other groups. Cryptosporidiosis was associated with ileal crypt hyperplasia, villus blunting, and inflammation. L-arginine improved mucosal histology after the infection. L-NAME abrogated these arginine-induced improvements. The infected control mice showed an intense arginase expression, which was even greater with L-NAME. L-arginine decreased the parasite burden, an effect that was reversed by L-NAME. Cryptosporidium parvum infection increased urine NO(3)(-)/NO(2)(-) concentrations compared with the uninfected controls, which was increased by L-arginine supplementation, an effect that was also reversed by L-NAME., Conclusion: These findings show a protective role of L-arginine during C. parvum infection in undernourished mice, with involvement of arginase I and nitric oxide synthase enzymatic actions., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Gastrointestinal nematodes represent a major production problem for ruminant livestock. Enhancing immunity to gastrointestinal nematodes through vaccination is desirable but mechanistic understanding of initial host responses that facilitate gastrointestinal nematode protective immunity is limited. We hypothesise that gastrointestinal nematode invasion induces mucosal epithelium damage and alarmin (e.g. IL33) release, thereby contributing to initiation of protective gastrointestinal nematode immunity. To test this, an in vitro air-liquid interface human HT-29 epithelial cell-Trichostrongylus colubriformis co-culture system was developed. Exsheathed L3 T. colubriformis exhibited both sinusoidal and burrowing motions in the co-culture system. Burrowing parasites, but not ivermectin-paralysed larvae, induced necrotic death of epithelial cells (annexin V(+)/propidium iodide(+)/caspase 3/7(-)). Microscopy confirmed that larvae consumed labelled necrotic epithelial cell contents. Trichostrongylus colubriformis larvae and their post-exsheathment antigens (excretory/secretory products) significantly induced IL33 mRNA expression in the epithelial cells. Immunoblot confirmed that IL33 was released from epithelial cells due to the damage caused by motile larvae. Exposure of HT-29 cells to alum or Sigma proprietary adjuvants induced significant epithelial cell IL33 mRNA expression without inducing cellular necrosis. Hence, the intracellular contents were not released externally where they might exert alarmin activity and this may limit their ability to trigger a protective anti-gastrointestinal nematode response. We conclude that T. colubriformis motion at the infection site induces intestinal epithelial cell necrosis which facilitates the release of intracellular contents, including IL33, and may be fundamental to the initiation of an appropriate host response to gastrointestinal nematodes. Our co-culture model is useful for studying initial epithelial cell-parasite interactions without conducting expensive animal trials., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)

Food-borne parasitic diseases, many known to be more prevalent in poor countries with deficient sanitary conditions, are becoming common worldwide. Among the emerging protozoan parasites, the most prominent is Trypanosoma cruzi, rarely reported in the past to be transmitted by the oral route but currently responsible for frequent outbreaks of acute cases of Chagas disease contracted orally and characterized by high mortality. Several other food-borne protozoans considered emerging include the apicomplexans Toxoplasma gondii and Cryptosporidium, as well as Giardia and Entamoeba histolytica. Here, the interactions of these protozoans with the mucosal epithelia of the host are discussed., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Giardia intestinalis is one of the major causes of parasite-induced diarrhea. The disease, giardiasis, is caused by trophozoites attaching to the intestinal epithelium, resulting in apoptosis of intestinal epithelial cells, disrupted epithelial barrier function and malabsorption. Microarray studies have detected extensive gene expression changes in intestinal epithelial cells (IECs) during interaction with Giardia trophozoites in vitro. In the present study, we examined this host-parasite interaction further by transcriptional profiling of interacting trophozoites using Giardia microarrays. A total of 200 Giardia transcripts were significantly changed due to the interaction, lasting up to 18 h in complete growth medium. Quantitative reverse transcriptase PCR confirmed the changes in all 12 genes tested using mRNA isolated in separate experiments. Genes encoding proteins previously suggested to be important during host-parasite interactions such as arginine deiminase, enolase and cysteine proteinases were up-regulated early but down-regulated later during the interaction. Cell division and attachment genes were down-regulated in the late time-points of interaction. The most highly up-regulated genes encode oxygen defense proteins and several members of the high cysteine membrane protein (HCMp) and Gly-rich repeat (GRREAT) families. Putative small RNAs were up-regulated, whereas the 5S rRNA was slightly down-regulated during the interaction with IECs. Thus, there are extensive gene expression changes in Giardia trophozoites and IECs during host-parasite interactions which can be important for establishment of infection and the induction of giardiasis., (Copyright © 2010 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

Immunoglobulin heavy chains identified in bony fish are broadly classified into three classes namely IgM, IgD and IgZ. The most recently described isotype is IgZ, a teleosts-fish specific isotype that shows variations in gene structure across teleosts. In this study we have identified two IgZ subclasses in common carp. IgZ1 is a four constant heavy chain domains containing antibody isolated across teleosts and IgZ2 is a two constant domains containing heavy chain chimera with a μ1 and ζ4 domain. Sequence analyses suggest that these subtypes are expressed from two separate genomic loci. Expression analyses show that IgZ1 is more abundant in systemic organs and IgZ2 chimera is preferentially expressed at mucosal sites. The basal expression level of IgM in fish is much higher than of the other isotypes. We show that IgZ1 expression in systemic and mucosal organs is responsive to blood parasites, while mucosal parasite infection induces IgM and IgZ2 gene expression. This report is the first to show differential expression of the IgZ variants in response to pathogens and suggests that the IgZ subtypes in carps may have mutually exclusive humoral functions., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

To provide re-description of Cryptosporidium cuniculus Inman and Takeuchi, 1979 (synonymous with rabbit genotype), a species closely related to Cryptosporidium hominis, the morphology, natural and experimental host specificity, and genetic characterisation were investigated. The morphology and diagnostic characteristics are typical of other intestinal species of Cryptosporidium, albeit with slightly larger oocysts (5.55-6.40×5.02-5.92 μm; mean 5.98×5.38 μm; length:width=1.1; n=50). Natural hosts appear to be European rabbits (Oryctolagus cuniculus) and humans (Homo sapiens). Experimental infections have been established in weanling rabbits (O. cuniculus), immunosuppressed Mongolian gerbils (Meriones unguiculatus) and immunosuppressed adult Porton strain mice (Mus musculus), but not in neonatal mice. Patterns of infection measured by oocyst shedding are significantly different compared with C. hominis, particularly in rabbits. Histological examination reveals endogenous stages in the brush border of the epithelium of the small intestinal villi, but clinical signs are absent. Inoculation of human HCT-8 cells results in discrete clusters of endogenous stages. A close relationship with C. hominis is inferred from molecular analyses at the ssrRNA, 70 kDa heat shock protein (HSP70), actin, Cryptosporidium oocyst wall protein (COWP), 60 kDa glycoprotein (GP60) genes and a region encoding a product of unknown function (LIB13). Sequences contained limited, consistent polymorphisms at the ssrRNA, HSP70 and actin genes, were identical at the COWP and LIB13 genes and demonstrated two unique families at the GP60 gene. Although genetically closely related, there are significant biological differences between C. cuniculus and C. hominis that support these protozoa being separate species. This is based on the current understanding of these organisms and relies on the assumption that mating between these species would not normally occur. If this is subsequently demonstrated their categorisation may need to be re-addressed., (Copyright © 2010 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

Infection with Giardia duodenalis is one of the most common causes of waterborne diarrheal disease worldwide. Mechanisms of pathogenesis and host response in giardiasis remain incompletely understood. Previous studies have shown that exposure to G. duodenalis products induce apoptosis in enterocytes. We recently discovered that sodium-dependent glucose cotransporter (SGLT)-1-mediated glucose uptake modulates enterocytic cell death induced by bacterial lipopolysaccharide. The aim of this study was to examine whether enhanced epithelial SGLT-1 activity may constitute a novel mechanism of host defense against G. duodenalis-induced apoptosis. SGLT-1-transfected Caco-2 cells were exposed to G. duodenalis products in low (5mM) or high (25mM) glucose media. In low glucose environments, G. duodenalis-induced caspase-3 activation and DNA fragmentation in these cells. These apoptotic phenomena were abolished in the presence of high glucose. A soluble proteolytic fraction of G. duodenalis was found to upregulate SGLT-1-mediated glucose uptake in a dose- and time-dependent manner, in association with increased apical SGLT-1 expression on epithelial cells. Kinetic analysis showed that this phenomenon resulted from an increase in the maximal rate of sugar transport (V(max)) by SGLT-1, with no change in the affinity constant (K(m)). The addition of phloridzin (a competitive inhibitor for glucose binding to SGLT-1) abolished the anti-apoptotic effects exerted by high glucose. Together, the findings indicate that SGLT-1-dependent glucose uptake may represent a novel epithelial cell rescue mechanism against G. duodenalis-induced apoptosis.

Sheep have a varying ability to resist infection with gastrointestinal nematodes. This ability is due in part to genetic differences that exist between individuals. In order to define these differences we have used real-time PCR to quantify gene expression responses in the gut mucosal surface of genetically resistant and susceptible sheep, following a nematode challenge. Expression profiles were determined in response to two different nematode species, Haemonchus contortus and Trichostrongylus colubriformis, and in divergent sheep originating from two different genetic backgrounds. Results show that the response generated differs between resistant and susceptible animals and is further impacted by the origin of the sheep and nematode species used for challenge. However, some conserved features of a response mounted by a resistant or a susceptible animal were identified. Genes found to be more abundantly expressed in resistant animals include markers of an early inflammatory response, several Toll-like receptors (TLR2, 4, 9) and free radical producing genes (DUOX1 and NOS2A). Conversely, genes differentiating susceptible animals indicate a prolonged response and development of a chronic inflammatory state, characterised by elevated expression of members of the NF-kappabeta signalling pathway (IKBKB and NFKBIA) together with delayed expression of regulatory markers such as IL2RA (CD25), IL10 and TGFbeta2. While multiple nematode response pathways were identified, the identification of conserved aspects of the response which associate with resistance provides evidence that alternative nematode control strategies, such as breeding for resistant animals, may be feasible.

Unlabelled: Hymenolepis diminuta is spontaneously expelled from mice; concomitant with worm expulsion was protection against colitis induced by dinitrobenzene sulphonic acid (DNBS). Here we examined the immune response mobilized by Balb/c and C57Bl/6 male mice in response to H. diminuta and assessed the requirement for CD4+ cells (predominantly T cells) in worm expulsion and the anti-colitic effect. Wild-type (CD4+) or CD4 knock-out (CD4-/-) mice received five H. diminuta cysticercoids and segments of jejunum and mesenteric lymph nodes (MLNs), or spleen, were excised 5, 8 and 1l days later for mRNA analysis and cytokine production, respectively. In separate experiments uninfected and infected mice received DNBS by intra-rectal infusion and indices of inflammation were assessed 3 days later (i.e. 11 days p.i.). Infection of Balb/c mice resulted in a time-dependent increase in intestinal mRNA for Foxp3, a marker of natural regulatory T cells, and markers of alternatively activated macrophages (arginase-1, FIZZ1), while concanavalin-A activation of MLN cells revealed a significant increase in T helper 2 (TH2) type cytokines: IL-4, -5, -9, -10, -13. MLN cells showed a reduced ability to induce Foxp3 expression upon stimulation. CD4-/- mice did not display this response to infection, but surprisingly did expel H. diminuta. Moreover, DNBS-induced colitis in CD4-/- mice (wasting, tissue damage, elevated myeloperoxidase) was not reduced by H. diminuta infection, whereas time-matched infected CD4+ C57Bl/6 mice had significantly less DNBS-induced inflammation., In Conclusion: (i) in addition to stereotypical TH2 events, H. diminuta-infected Balb/c mice develop a local immuno-regulatory response; and (ii) CD4+ cells are not essential for H. diminuta expulsion from mice but are critical in mediating the anti-colitic effect that accompanies infection in this model.

In order to investigate immunological changes over time in pigs infected with Trichuris suis, we inoculated 40 pigs with 5000 infective T. suis eggs and left 40 pigs as uninfected controls. Equal numbers of pigs from both groups were sacrificed every other week from 1 to 11 weeks p.i. At necropsy tissue samples were collected from all pigs and their worm burdens were determined. In the proximal colon of T. suis-infected pigs infiltration of eosinophils peaked 5 weeks p.i. and mast cell infiltration developed from 5 to 11 weeks p.i. Histological evaluation of the proximal colon revealed that the presence of T. suis was closely associated with intestinal histopathological changes such as crypt hyperplasia, goblet cell hyperplasia and a general hypertrophy of mucosa. The crypt lengths were positively associated with worm burdens. Real-time PCR analysis of genes related to immune function indicate a local increased transcription of genes coding for CCR3, ARG1, MUC5AC, IL-4, IL-5, IL-13, FcepsilonR1alpha, and IL-13Ralpha2 and decreased expression of genes coding for iNOS, TNF-alpha, IL-10, CD3epsilon, CD80, CD86, IL-4Ralpha, IL-13Ralpha1 and CD40 in the proximal colon of pigs infected with T. suis. This local T-helper cell Type 2-like gene-expression pattern indicates that the Type 2 immune response characteristic of helminth infections in both mouse and humans also develops in pigs infected with T. suis. The results from this study expand our knowledge of the immunomodulatory effect of T. suis, a parasite that has proven effective in treating inflammatory bowel disease, when its eggs are administered regularly to patients.

The ultrastructural characterisitics of four types of Toxoplasma gondii schizonts (types B, C, D and E) and their merozoites, microgamonts and macrogamonts were compared in cats killed at days 1, 2, 4 and 6 after feeding tissues cysts from the brains of mice. Schizonts, merozoites and gamonts contained most of the ultrastructural features characteristic of the phylum Apicomplexa. All four types of schizonts developed within enterocytes or intraepithelial lymphocytes. Occasionally, type B and C schizonts developed within enterocytes that were displaced beneath the epithelium into the lamina propria. Type D and E schizonts and gamonts developed exclusively in the epithelium. Tachyzoites occurred exclusively within the lamina propria. Type B schizonts formed merozoites by endodyogeny, whereas types C to E developed by endopolygeny. The parasitophorous vacuoles surrounding type B and C schizonts consisted of a single membrane, whereas those surrounding types D and E schizonts were comprised of two to four electron-dense membranes. The parasitophorous vacuole of type B schizonts had an extensive tubulovesicular membrane network (TMN); the TMN was reduced or absent in type C schizonts and completely absent in types D and E schizonts and gamonts. Type B merozoites were ultrastructurally similar to tachyzoites, except that they were slightly larger. Type C merozoites exhibited a positive periodic acid-Schiff reaction by light microscopy and ultrastructurally contained amylopectin granules. Rhoptries were labyrinthine in type B merozoites but were electron-dense in types C-E. The development of microgamonts, macrogamont and oocysts is also described.

It has been suggested that the periparturient breakdown of immunity to parasites has a nutritional basis. Our overall hypothesis is that it results from a prioritised scarce nutrient allocation to reproductive functions (e.g. milk production) rather than to immune functions. We tested this hypothesis by offering five levels of dietary metabolisable protein, ranging from 0.65 to 1.25 times their assumed requirements, for 4 weeks post-parturition to twin-rearing Greyface ewes, experimentally infected with Teladorsagia circumcincta. We hypothesised that the initial increments of metabolisable protein supply would increase milk production without affecting the degree of breakdown of immunity whilst later increments would reduce the degree of breakdown of immunity. The first two increments of metabolisable protein supply indeed increased milk production and did not affect final worm burdens, but in contrast to the expectation, reduced faecal egg counts and total egg output. The last two increments of metabolisable protein supply did not further affect milk production and egg output, but resulted in reduced final worm burdens. Metabolisable protein supply did not affect plasma IgG and IgE antibody against somatic L(3) antigen but the first three increments reduced plasma pepsinogen and plasma IgA antibody. The last increment did not further reduce plasma pepsinogen but increased plasma IgA. Metabolisable protein supply did not systematically affect abomasal mucosal mast cell, globule leukocyte and eosinophil counts. Our results support the view that the priority of scarce metabolisable protein allocation to milk production over immune functions may be gradual rather than absolute. The contrast between effects of metabolisable protein supply on faecal egg count and final worm burden points towards the possibility that if different effector responses regulate fecundity and worm expulsion, then they would differ in their sensitivity towards changes in the degree of nutrient scarcity.

Limited studies have shown that in intestinal schistosomosis, the enteric nervous tissue becomes inflamed, disrupted and destroyed by granulomas and peptides, amines and neurofilaments contents are altered. Therefore, immunoreactivities of vasoactive intestinal peptide and substance P were correlated to pathological lesions in the large intestine from pigs infected with Schistosoma japonicum. Ganglia situated within or near granulomas showed ganglionitis, and necrosis of neurons as well as infiltration by eosinophils, mast cells, lymphocytes, plasma cells, neutrophils and macrophages. The inner submucous and mucous plexuses were the most damaged. In all categories of inflamed areas, the vasoactive intestinal peptide-like immunoreactive was reduced in all plexuses whereas, that of substance P was increased both in the enteric nerve plexuses and enterochromaffin cells in lightly, moderately and severely inflamed tissues. However, both peptides were highly diminished or absent in very severe lesions and areas surrounding schistosome eggs and mature worms laying eggs in the submucosal veins. The alterations of the levels of vasoactive intestinal peptide and substance P were correlated with severity of inflammation. Our observations show alterations of vasoactive intestinal peptide and substance P contents in the local microenvironment in the vasoactive intestinal peptide- and substance P-mediated reflex pathways which regulate intestinal motility, epithelial transport and modulate immunity. These changes could cause alterations in bowel motility, electrolyte and fluid secretion, vascular and immune functions during S. japonicum infections in the pig. This may, therefore, partly play a role in the pathobiology of migration and egress of schistosome eggs as well as influence trapping of eggs in granulomas, and account for diarrhoea, loss of body weight and failure to thrive, which are recorded in schistosomosis.

This study aimed to characterise the local (intestinal) immune response of rats after primary and challenge infections with Eimeria separata. Naive rats and rats which had been immunised by two moderate infections were exposed to a heavy infection with 100000 oocysts per animal. Necropsies were performed 0, 24 and 48 h after infection and lymphocyte subpopulations were microscopically quantified in the caecum mucosa after marking by immunohistological techniques. There was no difference between naive and immune rats concerning the number of CD45R(+) (B) cells, whereas significantly more CD3(+) (T) cells were found in the caecum wall of the immune rats. CD4(+) T cells predominated in animals after primary infection, whereas CD8(+) T cells represented the major T-cell subset in challenged rats. The proportion of TCRgammadelta(+) T cells did not differ in the mucosa between the groups examined, whereas challenged rats showed significantly increased numbers of TCRalphabeta(+) T cells in the caecum wall when compared with animals after a primary infection. Thus, CD4(+) T cells may be particularly involved in the immune response to a primary infection of rats with E. separata whereas immunity to a challenge infection seems to be mediated predominantly by CD8(+) and TCRalphabeta(+) T cells.

The study reported here investigated acquired resistance of mice and pigs to challenge-infections with Schistosoma japonicum. Two morphologically indistinguishable isolates of the parasite (from the Anhui and Zhejiang provinces of China), which could be typed by polymerase chain reaction-linked restriction fragment length polymorphism analysis (PCR-RFLP), were used for the infections. In two parallel infection studies, 60 female outbred NMRI mice and 29 Danish Landrace/Yorkshire/Duroc crossbred pigs were used. Two of the groups received a primary infection with either the Anhui or the Zhejiang isolate, respectively. The remaining groups received a primary infection with the Zhejiang isolate and challenge-infections with the Anhui isolate at either week 2, 3, 4 or 6 post primary infection. The results of the study indicated that both mice and pigs are partially resistant to challenge-infection from week 4 post primary infection. Resistance appeared to decrease in pigs 6 weeks after primary infection, while it remained effective in mice. These results suggest that the mechanism responsible for acquired resistance in mice and pigs may not be the same and support the theory that worm burdens in pigs receiving repeated infection are in a balance between acquisition and loss of worms.

Intestinal parasitism is a major stress factor leading to malnutrition and lowered performance and production efficiency of livestock and poultry. Coccidiosis is an intestinal infection caused by intracellular protozoan parasites belonging to several different species of Eimeria. Infection with coccidia parasites seriously impairs the growth and feed utilization of chickens and costs the US poultry industry more than $1.5 billion in annual losses. Although acquired immunity to Eimeria develops following natural infection, due to the complex life cycle and intricate host immune response to Eimeria, vaccine development has been difficult and a better understanding of the basic immunobiology of pertinent host-parasite interactions is necessary for developing effective immunological control strategies against coccidiosis. Chickens infected with Eimeria produce parasite specific antibodies in both the circulation and mucosal secretions but humoral immunity plays only a minor role in protection against this disease. Rather, recent evidence implicates cell-mediated immunity as the major factor conferring resistance to coccidiosis. This review will summarize current understanding of the avian intestinal immune system and its response to Eimeria as well as provide a conceptual overview of the complex molecular and cellular events involved in intestinal immunity to coccidiosis. It is anticipated that increased knowledge of the interaction between parasites and host immunity will stimulate the birth of novel immunological and molecular biological concepts in the control of intestinal parasitism.

Small intestine goblet cell numbers and the composition of their mucus were compared in guinea pigs with genetically determined differences in responsiveness to Trichostrongylus colubriformis infection. Prior to infection, no differences between high responder and low responder animals were detected. However, following primary infection with T. colubriformis, pronounced goblet cell hyperplasia developed and the proportion of sulphomucin in these cells increased. Both changes developed significantly earlier in high responder animals.

Oesophagostomum dentatum, one of the most common nematodes in pigs, causes the formation of subepithelial granuloma in the large intestine. To investigate possible changes in epithelial function or response during the infection we incubated epithelia of pig proximal colon in Ussing chambers at different days post infectionem (p.i.). Transepithelial conductance, gt, and the Cl flux from serosal to mucosal, JsmCl, were increased on day 2 p.i., when the nematodes penetrate the epithelium of the large intestine, and declined toward control levels thereafter. Histamine, PGE2 and carbachol caused transient increases in short circuit current, Isc, and conductance that could partly be attributed to a higher JsmCl. The Isc responses were highest on the days of nematode penetration in or out of the epithelium (days 2 and 14 p.i.) and did decline on day 7 p.i. during the histotropic development of the parasite. This reduced epithelial reaction on day 7 p.i. might be an adaptation to secretory stimuli released from the inflammatory cells in the intestinal wall or might reflect modulation by the parasite and could be responsible for the absence of marked clinical signs during the infection.

Progress towards effective vaccines to control internal parasites, especially those affecting mucosal compartments, has been inhibited by the combined problems of the antigenic complexity of parasites and the lack of understanding of the host response. However, the accumulation of information regarding regulation of mucosal immunity has enabled a reappraisal of vaccination options to provide appropriate mucosal effector responses. The pivotal role of T cell influences, and in particular the contribution of cytokine signals, has been clearly established from in vitro studies, but data emerging from our laboratories provide evidence for these effects in vivo. We have demonstrated the role of T cells in determining the outcome of an intestinal response and propose a role for local Th2 cytokine production in this regard. To support this proposition, the distribution of cytokine mRNA has been determined by in situ hybridisation techniques in normal and parasitised animals. Further, we have shown that in the absence of Th2 cytokines (using gene knockout animals) mucosal responses are grossly deficient; we have also shown that this defect can be overcome by vector-directed gene therapy. These studies have indicated that new mucosal immunisation opportunities exist by combining traditional immunisation approaches with strategies to upregulate local cytokine production. However, the success of these new strategies will depend on selection of highly immunogenic subunit antigens, coupled with techniques for cytokine manipulation and delivery with appropriate adjuvant/vehicle formulations. This paper reviews delivery technologies available to chaperone labile antigenic and genetic material to appropriate sites for mucosal stimulation after systemic or oral administration.

Abomasal cannulae were surgically placed in 7 2-year-old New Zealand Romney sheep which had been maintained parasite-free from birth. Four of these sheep were randomly selected and dosed orally with 10,000 infective Trichostrongylus axei larvae per week for 8 weeks, while the remaining 3 sheep served as uninfected controls. Abomasal biopsy, blood and faecal samples were obtained from all sheep at regular intervals from 5 days before and until 58 days after the first infection. The sheep were then killed, worm burdens assessed and abomasal and small intestinal samples collected Faecal egg counts of all 4 dosed sheep were low and only one (No. 701) had a substantial worm burden (8400) post mortem. Overall, levels of mucosal mast cells/globule leukocytes, eosinophils, T19+ cells and larval migration inhibitory activity increased significantly in the abomasal mucosa of the dosed sheep compared to the controls. The CD4+:CD8+ cell ratio in the abomasal mucosa of the dosed sheep also increased compared to that of the controls (P = 0.06). In blood, T. axei-specific antibody (total and IgG1) and eosinophil numbers increased significantly in the dosed sheep. Mucosal cells staining for IgE (IgE+), and blood and mucosal eosinophils showed the earliest substantive increases in number followed by increases in specific serum antibody levels, numbers of mucosal cells fluorescing under UV light (UVf) and T19+ cells. The difference in the IgE+ and UVf cell responses indicated that expansion of globule leukocyte numbers lagged behind that of mucosal mast cells. The results supported the concept of CD4+ T cell help in the abomasal mucosa and defined the sequential expression of components of the immunological responses potentially mediating resistance to T. axei. In sheep No. 701, persistence of adult worms was associated with lower mucosal IgE+ cell and eosinophil responses compared with the other dosed sheep.

A bobcat was found recently killed on "Highway 101" near the town of San Fernando, Tamaulipas State, Mexico (100 km south of Brownsville, TX, U.S.A.). The cat (Lynx rufus texensis) was parasitized by several species of nematodes and trematodes, but mainly by a cestode, Echinococcus oligarthrus. The diagnostic characteristics of this cestode are described and illustrated. E. oligarthrus has not been reported previously in North America. This is the first time that the strobilar stage has been recovered from a "bobcat". A potential public health problem may be raised by the presence of this cestode in Mexico.

Interactions between live Entamoeba invadens trophozoites and guinea-pig caecal explants were studied. A high percentage of amoebae adhering to the apical surface of epithelial cells was observed 10-20 min after infection, but no histopathological changes were observed. After 30 min, mild oedema at the base of the interglandular epithelium and death of some epithelial cells were evident. The epithelial barrier was invaded by amoebae at desquamating zones and phagocytosis of epithelial cells or cellular debris was occasionally observed. Invasion of the mucosa and tissue necrosis became more severe with increased time of incubation. The continuity of epithelial lining was severely compromised after 2 h of infection and erosive lesions were prominent in the mucosa. These results demonstrate that E. invadens is able to invade the intestinal epithelium although it reportedly lacks the powerful cytotoxic and cytolytic elements described for E. histolytica.

Vaccination by different routes and with different adjuvants is known to influence profiles of immune responses and may be used to overcome genetically determined low-responsiveness to infection. A mouse model of infection with the intestinal nematode Trichinella spiralis was used to investigate the effect of mode of vaccination upon immune responsiveness and worm expulsion phenotype in high- (NIH) and low- (C57 BL/10) responder strains of mice. Muscle larval homogenate antigen was given subcutaneously in Freund's complete adjuvant (FCA) to induce a systemic immune response or with cholera toxin (CT) orally to stimulate mucosal immunity. Both approaches significantly protected NIH mice. Vaccination with FCA was correlated with elevated serum IgG after infection, whereas oral CT-vaccination resulted in increased levels of intestinal IgA. Neither type of vaccination successfully protected the low-responder C57 BL/10 strain and there were no effects on the low antibody levels that infection induced in this strain.

Tissues from corticosteroid-treated gerbils hyperinfected with Strongyloides stercoralis were compared grossly and microscopically to similar tissues from animals with uncomplicated strongyloidiasis. Gerbils with hyperinfection developed severe pulmonary alveolar haemorrhage with a variable degree of subacute eosinophilic interstitial pneumonia associated with numerous alveolar, vascular and interstitial larvae. Hyperinfection induced by corticosteroids, given either before inoculation of S. stercoralis larvae or after a chronic Strongyloides infection was established, produced similar lesions. In contrast, lungs from gerbils with uncomplicated Strongyloides infection had severe eosinophilic perivasculitis and vasculitis with very little haemorrhage, no pneumonia and no larvae. Sections of adult worms were present in the proximal part of the intestinal tract, lodged in spaces between mucosal epithelial cells. Adult worms were not associated with inflammation and were more common in the corticosteroid-treated gerbils. In corticosteroid-treated gerbils only, there were numerous larvae in the distal intestinal tract, throughout the intestinal wall and adjacent mesentery, within interstitial tissues and in lymphatic vessels. Significant inflammation with associated larvae was only present in the caecum and mesenteric lymph nodes, suggesting that the caecum was the main site for initiation of parenteral migration with subsequent invasion of the lymphatic system and lungs. The lesions in these gerbils were similar to those found in humans. Infection of gerbils with S. stercoralis is the best rodent model of human strongyloidiasis.

Two strains of Trichostrongylus colubriformis of ovine origin, one resistant and one susceptible to thiabendazole, were compared during experimental infection in rabbits. Groups of rabbits were infected with 5000 infective larvae (L3) of either the resistant or the susceptible strain. On days 21 and 42 post-infection (p.i.), 5 rabbits of each group were killed and the small intestine divided into three sections for worm counts and histological or biochemical analysis. Faecal egg counts were performed twice a week from day 15 to day 42 p.i. The physiology of the worms was characterised by in vitro acetylcholinesterase secretion of adult worms. The host inflammatory response was determined by peroxidase activity in mucosal homogenates and by histological counts of mast cells and eosinophils. Infectivity was not significantly different between the two strains. However, egg production was delayed and was significantly lower for the resistant strain. Conversely, in vitro secretion of resistant worms was significantly higher than the susceptible ones. The mucosal homogenetates of rabbits infected with the resistant strain had significantly higher levels of peroxidase activity in the duodenum on days 21 and 42 p.i. Mast cell counts were also significantly higher in the duodenum on day 42 p.i., in rabbits infected with the resistant strain. No difference was observed in the eosinophil counts. These results suggest that genetic variation in the nematode, such as anthelminthic resistance, is associated with variations in worm biology and physiology as well as differences in the inflammatory response of the host.

Susceptibility of the Indian soft-furred rat, Millardia meltada, to infection with the intestinal helminth, Nippostrongylus brasiliensis, was examined. After subcutaneous infection with 1500 infective larvae (L3), daily faecal egg output (EPG) of both male and female animals reached a peak at 1 week post-infection (p.i.) with the same magnitude (about 20,000 epg faeces) and then rapidly decreased below detection level at around 2 weeks p.i. In male animals, however, after a transient cessation at 2 weeks p.i., parasite eggs reappeared in faeces 3 weeks afterwards, though the counts were far lower than the first peak. This phenomenon was rarely seen in female animals. High susceptibility of M. meltada to N. brasiliensis was confirmed by worm burdens. About 70% of the initial dose of larvae became adult worms in the intestine of male and female hosts. As suggested by the decline in egg counts, the majority of adult worms were expelled by 2 weeks p.i. The residual worm burden at 2 and 4 weeks p.i. was significantly higher in male than female animals. When orchidectomized males were infected with N. brasiliensis, the magnitude of residual worm burden was significantly reduced. On the other hand, ovariectomy did not affect the number of residual worms in females.

Helminthologically naive merino sheep were given either a single infection of 30,000 or a trickle infection of 6000 Trichostrongylus colubriformis infective larvae (TcL3) per week. Faecal egg counts started to fall after 8 weeks in the single infection and after 11 weeks in the trickle infection. Small intestinal contents were collected from indwelling intestinal fistulae over the next 14 weeks. Concentrations of sheep mast cell protease (SMCP) in these contents increased to highest levels 9-11 weeks and 6-10 weeks after the single infection and from the start of the trickle infection, respectively. Similarly, peptidyl leukotriene (PLT) concentrations were highest at 6 weeks and at 6-9 and 13 weeks, respectively. Histamine concentrations increased slightly after both infections to peak values at 7 weeks and 9 weeks, respectively. Inhibition of migration of larvae in vitro was increased in contents sampled at 8 weeks after the single infection and after 6-10 weeks of the trickle infection. Another 2 groups of sheep were immunised by repeated infections with TcL3. Gut contents from 1 group sampled immediately before and after challenge with 30,000 TcL3 at 0 and 18 days had increased levels of larval migration inhibitory (LMI) activity throughout the 35 day period, especially 7-14 days after challenge (DAC). The mediators SMCP increased significantly 5-7 DAC while PLT increased 7-14 DAC. In the second group of immunised sheep, levels of SMCP and PLT increased rapidly within 1 DAC and further increased 3-14 DAC.(ABSTRACT TRUNCATED AT 250 WORDS)

The possible importance of mucosal mast cells in the expulsive mechanisms of mice against Strongyloides venezuelensis was examined. After a primary infection by subcutaneous inoculation with various doses into C57BL/6 mice, about 50% of the initial dose of infective larvae (L3) became adult worms and, regardless of the dose of infection, they were completely expelled by Day 12 with similar kinetics. Intestinal mastocytosis at the time of expulsion was comparable among groups given different doses of infection. A kinetic study after infection with 2000 L3 in C57BL/6 mice revealed that mastocytosis started from Day 8, rapidly reached a peak on Day 12, and then gradually decreased. The strongest mastocytosis was observed in the upper one sixth of the small intestine where the majority of adult worms parasitized. Over 80% of mast cells induced by the infection were located in the intestinal epithelial layer. When mast cell-deficient W/Wv and their normal littermate +/+ mice were infected with 1000 L3, expulsion was significantly delayed in W/Wv mice, though adult worms were eventually expelled by Day 18 in W/Wv mice. Delayed expulsion as well as defective mast cell responses of W/Wv mice were completely restored by bone marrow grafting 10 weeks prior to infection. These results show that, like S. ratti infection, intestinal mucosal mast cells are important in causing expulsion of S. venezuelensis.

During infection in mice Echinostoma caproni is attached to the mucosa of the small intestine with the ventral sucker (acetabulum). The morphology, histology and dynamics of attachment sites from primary infections were examined. The sites were highly characteristic microscopically, and consisted of a plug of grasped mucosa occupying the cavity of the ventral suckers. The mucosa in the area of the small intestine where the parasite resided showed marked villous atrophy and crypt hyperplasia. The cellular composition of the attachment sites did not appear significantly different from what was seen in other parts of the mucosa in the residential area, and the study did not reveal any specific cellular host response at the attachment site. After mechanical removal of the parasites from unfixed tissue in saline, the attachment sites gradually reduced in size and disappeared. It is suggested that the attachment sites are only temporary structures, formed by the mechanical grasp of the ventral sucker as the parasites move about in the residential area of the intestine.