Regulation of egg production, worm burden, worm length and worm fecundity by host responses in sheep infected with Ostertagia circumcincta

Following infection with Ostertagia circumcincta there was considerable variation in worm burdens, worm size and number of inhibited larvae even among sheep matched for age, sex, breed, farm of origin and history of parasite exposure. There was also substantial variation among sheep in the concentration of mast cells, globule leucocytes, eosinophils, IgA-positive plasma cells and parasite-specific IgA in the abomasal mucosa. With the exception of faecal egg counts over time, the parasitological and immunological traits were all continually distributed among animals and sheep did not fall into discrete high and low-responder categories. The responses were correlated. Sheep with more mast cells also had more globule leucocytes, more eosinophils, more IgA plasma cells and greater amounts of parasite-specific IgA in the abomasal mucosa. Female worm length was strongly and positively correlated with the number of eggs in utero. Faecal egg counts were associated with variation in worm number and with variation in the number of eggs in utero. The worm burden was negatively correlated with the number of globule leucocytes in the abomasal mucosa, suggesting that worm numbers are regulated by immediate hypersensitivity reactions. Decreased female worm length was associated with an increased local IgA response to fourth stage larvae. The number of inhibited larvae was positively associated with the size of the local IgA response and positively associated with the size of the worm burden. The results suggest that variation among mature sheep in faecal egg counts is due, at least in part, to variation in local IgA responses which regulate worm fecundity and to variation in local immediate hypersensitivity reactions which regulate worm burdens.     

Effect of a low protein diet on the resistance of Churra sheep to Teladorsagia circumcincta

SUMMARY The aim of this study was to understand the influence of a low protein diet on the resistance of the Churra breed sheep to infection with Teladorsagia circumcincta. A previous experiment in our department demonstrated significant differences between resistant and susceptible sheep infected with T. circumcincta, in eggs per gram of faeces, serum pepsinogen, serum IgA and peripheral eosinophilia (unpublished). The sheep were fed with a balanced protein diet. In the current assay there were significant differences between the resistant and susceptible groups in egg output, serum pepsinogen and worm burden. The optical densities (OD) of the IgA in blood samples, nasal secretions and saliva were tested throughout the study and the differences between groups were not significant. At necropsy adult worm length, the number of eggs in utero in adult females, the number of fourth stage larvae and the OD of gastric mucus IgA did not differ between groups either. Moreover, due to diet there was a loss of weight in both groups but this was not significant. Our results support the view that low protein diets could influence immune function and as a result resistant genotypes do not show any superiority in comparison with susceptible ones.     

Isotype-specific antibody responses to Haemonchus contortus in genetically resistant sheep

The kinetics of anti-Haemonchus antibody responses in serum and faecal extracts of pasture-reared, genetically resistant and random-bred sheep infected with Haemonchus contortus were examined using an isotype-specific ELISA. Anti-Haemonchus antibodies of IgA, IgG1, IgG2 and IgM isotypes were detected in serum and faecal extracts of both resistant and random-bred sheep after challenge infection. Serum IgG1 and IgA levels in resistant sheep were significantly higher than in random-bred sheep between 10 and 31 days after infection. However, there were no differences in IgG2 and IgM antibody responses between the two genotypes. Faecal antibody responses to H. contortus showed a clear genetic effect with resistant sheep exhibiting higher IgA levels throughout infection and higher IgG1 levels between 24 and 31 days after infection. Furthermore, serum IgG1 and IgA, and faecal IgA responses were negatively correlated with faecal egg counts in both genotypes on 17, 24 and 31 days after infection. Together, these results are taken to indicate that anti-parasite IgA and IgG1 antibodies may play an important role in genetically determined resistance of sheep to haemonchosis     

Effect of Ovar‐DRA and Ovar‐DRB1 genotype in small ruminants with haemonchosis

The effect of Ovar‐DRA and Ovar‐DRB1 genotypes on faecal egg count (FEC) was determined in sheep and goats infected with Haemonchus contortus. One hundred and forty‐three sheep from 3 different breeds (St. Croix, Katahdin and Dorper) and 150 goats from three different breeds (Spanish, Boer and Kiko) were used. Parasitological (FEC), haematological (packed cell volume) and immunological (IgA, IgG and IgM) parameters were measured. Sheep populations showed a higher FEC and humoural response than goat breeds. Genotypes were determined by high‐resolution melting assays and by conventional PCR. For Ovar‐DRA, sheep and goats carrying the AA genotype showed significant lower FEC than AG and GG genotypes. The additive effect was found to be 115.35 less eggs per gram of faeces for the A allele for goats. For Ovar‐DRB1, only in sheep, the GC genotype was associated with low FEC. The additive effect was 316.48 less eggs per gram of faeces for the G allele, and the dominance effect was 538.70 less eggs per gram of faeces. The results indicate that single nucleotide polymorphisms within Ovar‐DRA and Ovar‐DRB1 could be potential markers to be used in selection programmes for improving resistance to Haemonchus contortus infection.     

Mechanisms of immunity to Haemonchus contortus infection in sheep

In two separate experiments, sheep were immunized by nine to 12 weekly immunizing infections with 4000 Haemonchus contortus third stage larva (L3), drenched with anthelminthics and maintained free of H. contortus infection for a further 12 weeks. The anamnestic cellular immune responses in both the abomasal lymph node (ALN) and mucosa of the immunized sheep were examined 3 and 5 days post challenge with 50 000 H. contortus L3. Sheep in the two experiments clearly segregated out in two distinct groups, one in which challenge larvae were obviously present in the tissues of all 12 sheep at 3 and 5 days post challenge while no challenge larvae were detected in tissues of seven of the eight sheep in the other group. In sheep in which no tissue larvae were detected, very few changes were noted in either the ALN or mucosa. In contrast, dramatic changes were observed in the cellular profiles of the ALN and mucosa after challenge infection in sheep in which larvae were observed in the abomasal tissues. In the ALN, these changes were characterized by an increase in the relative percentage of gammadelta-TCR+ T cells and B cells and an increase in the proportion of CD4+ T cells coexpressing the activation markers MHC class II and CD25. In the abomasal mucosa, an increase in the number of infiltrating CD4+ and gammadelta-TCR+ T cells and B cells was observed by 3 days postinfection and these levels were further increased at 5 days postinfection. This infiltration of the abomasal mucosa by lymphocytes was accompanied by a dramatic increase in the number of infiltrating eosinophils, which were often in intimate association with the surface of H. contortus larvae. None of these changes occurred in the mucosa of the sheep that showed no sign of challenge larvae in the tissues; however, a transient increase in gammadelta T cells in the ALN and a drop in intraepithelial globule leucocytes were uniquely observed in these sheep at 5 days post challenge. These results suggest that two different types of immune responses can be generated after challenge infection of immunized sheep, one where tissue larvae are excluded from their tissue niche as observed previously and which is associated with changes in globular leucocyte population but no mobilization of the local immune system. In contrast, when challenge larvae reach their tissue niche, dramatic changes in the local immune system occur, including a pronounced infiltration of eosinophils. These two immune mechanisms may be associated with the rapid and delayed rejection of parasite infections in immune sheep.     

Shared HLA class II-associated genetic susceptibility and resistance, related to the HLA-DQB1 gene, in IgA deficiency and common variable immunodeficiency.

Most cases of selective IgA deficiency (IgA-D) and common variable immunodeficiency (CVID) occur sporadically. However, familial clustering is not uncommon, and the two disorders can occur within the same family. We have previously described positive associations with three DR-DQ haplotypes as well as a strong negative association with DRw15,DQw6,Dw2 in IgA-D. Different amino acids at position 57 of the HLA-DQ beta chain were found to be related to susceptibility and resistance to IgA-D. Now we have found identical, although somewhat weaker, positive and negative DR-DQ associations in a large group of CVID patients (n = 86), as well as the same associations with codon 57 of the DQB1 gene. In addition, we have confirmed our earlier observations in an independent group of IgA-D individuals (n = 69), and in sib-pair analysis we have found linkage of the genetic susceptibility to IgA-D to the HLA class II region. In IgA-D individuals not carrying the three overrepresented DR-DQ haplotypes, the same positive association with a non-aspartic acid residue at position 57 of the HLA-DQ beta chain was seen. The previously reported associations with deletions of the HLA class III genes C4A (fourth component of complement) and CYP21P (steroid 21-hydroxylase pseudogene) were, in our groups of immunodeficient individuals, statistically secondary to the association with the DQB1 allele 0201. The shared HLA class II associations in the two humoral immunodeficiencies support the hypothesis that IgA-D and CVID are related disorders. Disease susceptibility and resistance are most closely associated with a gene(s) within the DR-DQ region, alleles of the DQB1 locus being candidate genes.     

Genetic resistance to Teladorsagia circumcincta: IgA and parameters at slaughter in Churra sheep

SUMMARY Previous experiments have shown that genetic resistance to infection by Teladorsagia circumcincta in sheep can be measured by the level of IgA in gastric mucus, jointly with other parameters. The aim of this study has been to observe the influence of IgA on adult worms. The experiment was carried out with Churra sheep experimentally infected with T. circumcincta. At slaughter, gastric content, gastric mucus, blood samples and faeces were recovered to determine the number of eggs in utero, length of adult females, worm burden, number of L4, titre of serum pepsinogen, peripheral eosinophilia and eggs per gram (epg). IgA activity in gastric mucus, serum, nasal secretions and saliva were tested against somatic antigen from fourth-stage larvae (L4), somatic antigen from the adult stage and excretory-secretory (E/S) antigen from the adult stage. The results showed a significant correlation between serum IgA and gastric mucus (P<0.01) as well as in nasal secretions (P<0.01). We found negative correlations between IgA activity in gastric mucus with the eggs in utero and with adult female length. Furthermore there were also strong relationships between the peripheral eosinophilia with serum (P<0.01) and gastric mucus IgA activity (P<0.01). Moreover serum pepsinogen and the number of L4 at slaughter were related (P<0.01).     

Some aspects of the immune response of Polish Wrzosówka sheep against gastrointestinal nematodes infection

The paper presents different aspects of natural gastrointestinal nematode infection in this primitive, prolific Polish Wrzosówka breed of sheep. The study was carried out on the flock located at the farm run by Warsaw Agricultural University at Zelazna (central Poland) in 1995-1998. Egg counts per gram of faeces, larval differentiation, total white blood cell counts, blood eosinophil counts, interleukin-5 concentration, lymphocyte blastogenic activity and IgG immune response were discussed. The egg counts were overdispersed and followed a different pattern each grazing season. The larvae obtained from faecal culture belonged to 6 categories: Trichostrongylus spp., Haemonchus contortus, Teladorsagia spp., Cooperia spp., Chabertia ovina/Oesophagostomum spp. and Nematodirus spp. However there were no discernible patterns in the composition of nematode population over time. Data analyses have shown that egg counts, eosinophil counts, IL-5 concentration and IgG level in different months each year were repeatable. The results obtained in two divergent groups of sheep, chosen for consistently low or high faecal egg counts have been presented also. Polish Wrzosówka breed of sheep is under conservation breeding program based mainly on the markers of breed standard. The results obtained in this study revealed that some parasitological, haematological and immunological parameters should be added to this program.     

Parasite loss and inhibited development of Teladorsagia circumcincta in relation to the kinetics of the local IgA response in sheep

Groups of yearling sheep, which had been trickle infected with Teladorsagia circumcincta for 8 weeks and then drenched, were challenged with 50 000 T. circumcincta larvae together with groups of worm-free controls. Fewer parasites and a greater proportion of early fourth stage larvae were recovered from previously infected sheep compared to controls. Worm loss and arrested development were evident by 5 days after challenge whereas growth retardation of developing worms was observed by day 10. In the previously infected sheep a secondary IgA response was observed in the efferent gastric lymph from 5 days post-infection. Western blot analysis showed the lymph IgA to be predominantly dimeric and nonsecretory in nature and that the somatic antigens recognized were predominantly in the 100-250 kDa range. The concentration of IgA in lymph was always higher than in blood and in the previously infected sheep increased fivefold 8 days post-challenge in contrast to blood where IgA levels were unchanged. The timing of the response suggested that it occurred too late to have been the cause of worm loss or arrested development, though it may have retarded the growth of developing parasites.     

HLA class II genotypes associated with chronic hepatitis C virus infection and response to α‐interferon treatment in Poland

Abstract: Aims/Background: Recent evidence suggests that spontaneous clearance of hepatitis C virus (HCV) may be associated with the HLA DQB1*0301 allele but there is still some debate over the role of other alleles and HLA haplotypes in HCV infection. As this may best be resolved by studying genetically different populations, we have investigated HLA class II‐encoded susceptibility and resistance to HCV infection in a relatively sedentary population of patients from northwestern Poland. Methods: The distributions of HLA class II DRB1, DQA1, DQB1 and DPB1 alleles were determined by standard PCR‐protocol in 129 unrelated patients with chronic hepatitis C (anti‐HCV and HCV‐RNA positive) and 103 healthy unrelated racially‐matched control subjects. Fifty‐five patients were treated with α‐interferon (5 MIU thrice weekly for 6 months) out of whom 29 showed a complete response and 26 were non‐responders. Results: A significantly reduced frequency of the DQB1*0301 allele in the patients was observed (24.0% vs. 38.8%; p=0.015). Additionally, two different DR‐DQ haplotypes were found to be associated with chronic HCV infection: DRB1*1501‐DQA1*01‐DQB1*0602 (24.0% vs. 12.6%; p=0.027) and DRB1*0701‐DQA1*0201‐DQB1*02 (31.8 vs. 12.6%; p=0.0006), the latter difference being most pronounced in those patients who responded to α‐interferon treatment (41.4% vs. 12.6%; p=0.00048). Conclusions: The results confirm the negative association between chronic HCV and DQB1*0301 and identify two novel genetic associations. In particular, the DRB1*0701‐DQA1*0201‐DQB1*02 haplotype is associated with both chronic infection and response to α‐interferon. Interestingly, the same haplotype is reportedly associated with non‐response to hepatitis B vaccination.     

The influence of challenge dose, duration of immunity, or steroid treatment on mucosal mast cells and on the distribution of sheep mast cell proteinase in Haemonchus-infected sheep

Summary The distribution of granule-specific sheep mast cell proteinase (SMCP). was assayed by immunocytochemistry and quantified by immunoassay in sheep immune to Haemonchus contortus. Repeated infection with Haemonchus larvae over 10–12 weeks induced a pronounced mucosal mastocytosis, including intraepithelial globule leukocytes (GL), which. 7 days after ceasing this dosing regime, was associated with the inability of incoming larvae to establish within the abomasal mucosa. Loss of this resistance, due to the cessation of stimulation with Haemonchus larvae 84 days previously or to treatment of sheep with cortico-steroid. was associated with a marked decline in mast cell density and concentrations of SMCP in abomasal mucosal tissues. Nevertheless, larvae also failed to establish in immune sheep rested from challenge 42 days previously and in which mast cell counts were not significantly different from those of control sheep. A small, but significant, release of SMCP was demonstrated in gastric mucus from immune sheep following larval challenge, whereas little or no SMCP was detected in mucus from naïve animals.     

Characterization of host responder types after a single Cooperia oncophora infection: kinetics of the systemic immune response

After primary infection with 100,000 third stage larvae of the intestinal nematode Cooperia oncophora in 3-month-old calves, a high variability in egg output and worm counts is observed. Based on this variability, infected animals can be divided in different responder types. The three major phenotypes can be classified as high, intermediate and low responder animals. We investigated whether calves classified into different responder types show different immune responses during infection. Peripheral blood eosinophil counts and flow cytometric analysis of different lymphocyte subsets of the blood did not reveal major differences between infected and control animals, nor between responder types. However, the levels of Cooperia-specific immunoglobulin (Ig)G1 and IgA during primary infection were significantly higher in intermediate responders than in low responders. In the intermediate responders, isotype specific responses were negatively correlated with parasitological parameters expressing worm expulsion and influence on worm fecundity. Total serum IgE levels were elevated in most of the infected animals. A quantitative positive relationship between worm counts and total serum IgE levels was observed. Based on the observed correlations, we propose a role for the humoral response against the maintenance of the infection in the gut.     

Genetic control of acquired resistance to haemonchosis in Merino lambs

Parasitological and immunological responses of genetically resistant and random-bred lambs to primary and secondary infection with H. contortus were studied. Resistant lambs had higher faecal egg counts and total worm burdens than the random-bred lambs following the primary infection. As there were no significant differences in serum and antibody levels, mucosal mast cells, circulating and tissue eosinophils between the two groups, it is inferred that what ever the underlying mechanism it was an innate characteristic. In contrast to primary infection, resistant lambs had significantly lower faecal egg counts and worm burdens than the random-bred lambs on secondary infection. Resistant lambs also exhibited significantly higher antibody levels, mucosal mast cell hyperplasia and mucosal eosinophilia in response to a challenge infection than the random-bred lambs. Furthermore, levels of mast cell hyperplasia and anti-Haemonchus antibodies correlated positively with the resistance status of the host. Taken together these results suggest that the genetic resistance of sheep to H. contortus results from the expression of an acquired immune response, and that anti-parasite antibodies and mast cell-derived mediators may play an important role in genetically determined resistance of sheep to haemonchosis.     

HLA class II genotypes associated with chronic hepatitis C virus infection and response to alpha-interferon treatment in Poland

AIMS/BACKGROUND: Recent evidence suggests that spontaneous clearance of hepatitis C virus (HCV) may be associated with the HLA DQB1*0301 allele but there is still some debate over the role of other alleles and HLA haplotypes in HCV infection. As this may best be resolved by studying genetically different populations, we have investigated HLA class II-encoded susceptibility and resistance to HCV infection in a relatively sedentary population of patients from northwestern Poland. METHODS: The distributions of HLA class II DRB1, DQA1, DQB1 and DPB1 alleles were determined by standard PCR-protocol in 129 unrelated patients with chronic hepatitis C (anti-HCV and HCV-RNA positive) and 103 healthy unrelated racially-matched control subjects. Fifty-five patients were treated with alpha-interferon (5 MIU thrice weekly for 6 months) out of whom 29 showed a complete response and 26 were non-responders. RESULTS: A significantly reduced frequency of the DQB1*0301 allele in the patients was observed (24.0% vs. 38.8%; p=0.015). Additionally, two different DR-DQ haplotypes were found to be associated with chronic HCV infection: DRB1*1501-DQA1*01-DQB1*0602 (24.0% vs. 12.6%; p= 0.027) and DRB1*0701-DQA1*0201-DQB1*02 (31.8 vs. 12.6%; p=0.0006), the latter difference being most pronounced in those patients who responded to alpha-interferon treatment (41.4% vs. 12.6%; p=0.00048). CONCLUSIONS: The results confirm the negative association between chronic HCV and DQB1*0301 and identify two novel genetic associations. In particular, the DRB1*0701-DQA1*0201-DQB1*02 haplotype is associated with both chronic infection and response to alpha-interferon. Interestingly, the same haplotype is reportedly associated with non-response to hepatitis B vaccination.     

Protection studies with recombinant excretory/secretory proteins of Haemonchus contortus

The efficacy of two recombinant proteins of Haemonchus contortus was studied in both adult sheep and young lambs. These 15 and 24 kDa excretory/secretory proteins were given combined, either supplemented or not with a glycan-rich insect cell extract. In 9-month-old sheep (trial 1), faecal egg output and worm burden were reduced by 49% and 55%, respectively, after vaccination with rec15/24, and by 46% and 65% after vaccination with rec15/24 and glycan extract. No reduction in egg output or number of worms was found in young lambs using the above recombinant proteins plus glycan-rich extract (trial 2). When trial 1 was repeated (trial 3), the protection could not be reproduced, possibly due to differences in batches of recombinant proteins. In all sheep, independent of their age, rec15/24-specific immunoglobulin (Ig)G1 and IgA titres were present, but 9-month-old protected sheep had significantly higher IgA titres than the lambs. Addition of glycans resulted in lower rec15/24-specific IgG1 and IgA in 9-month-old sheep after challenge. This did not affect the level of protection. A significant negative correlation was found between IgA and worm numbers in protected sheep immunized with rec15/24 supplemented with glycans. Total IgE and rec15/24 specific IgE titres were low. The number of eosinophils, mast cells, sheep mast cell protease (SMCP)+ cells and IgA+ cells did not differ between the protected and unprotected sheep, but the lambs had significantly fewer mast cells independent of their immunization.     

Differences in immune parameters are associated with resistance to Haemonchus contortus in Caribbean hair sheep

Caribbean hair sheep are more resistant to gastrointestinal nematodes than conventional wool breeds, but mechanisms that confer resistance are not fully understood. This study compared immune effector cell populations and antibody concentrations in 12 hair and 12 wool lambs infected with the abomasal parasite Haemonchus contortus and sacrificed at 3 or 27 days post‐infection (p.i.) and 14 uninfected animals of each breed. Faecal egg counts were over 2·5‐fold higher (P = 0·12) and packed cell volumes approximately 8% lower (P < 0·10) in infected wool lambs. Abomasal lymph nodes were heavier in infected animals (P < 0·05) and infected hair sheep had larger lymph nodes than infected wool sheep (P < 0·05). Tissue eosinophil concentrations were likewise larger (P = 0·07) in hair compared with wool sheep at 3 days p.i. Circulating levels of IgE and IgA in uninfected lambs were higher in hair sheep (P < 0·05) and during infection, hair sheep had higher serum IgA than wool sheep at 3, 5, and 21 days p.i. (P < 0·05). Serum IgE in infected lambs did not differ between breeds, but concentrations of IgE in lymph nodes were higher (P < 0·01) at 27 days p.i. in infected hair sheep.     

Analysis of HLA-DRB1, DQA1, DQB1 haplotypes in Sardinian centenarians

Some genetic determinants of longevity might reside in those polymorphisms for the immune system genes that regulate immune responses. Many longevity association studies focused their attention on HLA (the human MHC) polymorphisms, but discordant results have been obtained. Sardinians are a relatively isolate population and represent a suitable population for association studies. Some HLA-DR and DQ alleles form very stable haplotypes with a strong linkage disequilibrium. In a previous study on Sardinian centenarians we have suggested that HLA-DRB1 *15 allele might be marginally associated to longevity. HLA-DR,DQ haplotypes are in strong linkage disequilibrium and well conserved playing a role in the association to diseases. Hence, we have evaluated, by amplification refractory mutation system/polymerase chain reaction (ARMS-PCR) the HLADQA1 and HLA-DQB1 allele frequencies in 123 centenarians and 92 controls from Sardinia to assess whether the association to HLA-DRB1 *15 allele may be due to the other genes involved in the HLA-DR,DQ haplotypes. The frequencies of HLA-DQA1, DQB1 haplotypes were not significantly modified in centenarians. Nevertheless by evaluating the frequency of DRB1 *15 linked haplotypes, we observed a not significant increase in centenarians of HLA-DQA1 *01, DQB1 *05 and HLA-DQA1 *01,DQB1 *06 haplotypes. These data suggest that these haplotypes might have a role in determining life span expectancy and longevity.     

Protective immunity to Brugia malayi larvae in BALB/c mice: potential of this model for the identification of protective antigens

Protective immune responses against the infective larvae of Brugia malayi have been demonstrated in BALB/c mice. Various factors governing resistance to reinfection have been examined to provide baseline data for use of this model in studies of immunoprophylaxis. Parasites that established following a primary infection survived for approximately 10 days, following which numbers declined rapidly to a low level. Resistance was evidenced by a more rapid clearance of secondary infection parasites. The degree of immunity expressed was not related to the route of administration of the initial infection (subcutaneous, intravenous, intramuscular, or intraperitoneal). However, both the level of resistance and the rapidity of its expression were dependent on dose, with as few as 2 larvae stimulating measurable immunity. Sensitization with living male or female adult worms, fourth stage larvae or microfilariae of B. malayi, or infective larvae of B. pahangi conferred substantial resistance to larval challenge. Significant levels of immunity were also induced by dead B. malayi larvae (46%) and their aqueous extracts (76%), but not with the corresponding insoluble fraction. We suggest that this experimental system is ideally suited to aid in the identification of putative protective antigens in brugian filariasis.     

Age-related protective immunity after vaccination with Haemonchus contortus excretory/secretory proteins

Protection against an experimental challenge infection by immunization with excretory/secretory products (ES) from Haemonchus contortus, containing predominantly proteins of 15 and 24 kDa, depends on the age of the sheep. Vaccinated sheep 9 and 6 months of age had reduced final worm burdens of 82 and 77, respectively. No reduction in worm burden was found in 3-month-old lambs. Nine-month-old sheep had significantly higher ES-specific serum immunoglobulin (Ig)G1 and IgA during immunizations and after challenge infection than 3-month-old lambs. There was no correlation within the 9-month-old sheep between ES-specific IgA or IgG1 levels and protection, measured as worm burden. However, when the different age groups were combined, negative correlations between percentage protection and ES-specific IgA and IgG1 levels after challenge were found. At the end of the experiment, peripheral blood eosinophils and mast cell counts in abomasal tissue were also significantly higher in the vaccinated and challenged 9-month-old sheep than in the vaccinated and challenged 3-month-old or than in the 9-month-old sheep with challenge, but without vaccination. The responses measured in young lambs were similar to the responses in sheep, but the height of these responses was in general of a lower magnitude.     

Experimental Schistosomiasis japonica in the pig: immunohistology of the hepatic egg granuloma

Use of the pig as an animal model in schistosomiasis research is increasing, but knowledge of the porcine immune response to schistosome infection is still very limited. We investigated the immunohistology of different maturation stages of the Schistosoma japonicum egg granuloma in pigs. Liver sections from pigs experimentally infected with S.japonicum for 9, 12 or 21 weeks were examined by immunohistochemistry using a three-step streptavidin-biotin-complex/immunoperoxidase method or a two-step alkaline phosphatase-mediated system. All granulomas showed marked expression of major histocompatibility complex (MHC) class II in epithelioid macrophages and were dominated by T lymphocytes, comprising both CD4+ and CD8+ phenotypes, with consistently higher proportions noted for CD8+ cells. B lymphocytes, as identified by expression of CD21, were confined to lymphoid nodular structures primarily associated with mature granulomas. Early and mature granulomas contained numerous immunoglobulin (Ig)G+ plasma cells. Significant differences in immunohistology related to duration of infection were not observed. The results indicate that all stages of the hepatic S.japonicum egg granuloma in the pig manifests MHC class II-dependent CD4+ T cell activity concomitant with infiltration of CD8+ T cells. B cell activity preceding the effector cell stage appears to occur in granuloma-associated lymphoid nodules, whereas antibody, mainly IgG, is produced within the granuloma.