Auto IgG anti-IgE and IgG x IgE immune complex presence and effects on ELISA-based quantitation of IgE in canine atopic dermatitis, demodectic acariasis and helminthiasis

Rapid induction of allergen-blocking IgG in dogs vaccinated with plant-based, Der f 2-expressing bioparticles

BACKGROUND

Allergen-carrying virus-like particles are effective and safe means of allergen immunotherapy (AIT) in rodent models.

OBJECTIVE

To study the development of allergen-blocking immunoglobulin (Ig)G in dogs injected with Der f 2-carrying enveloped plant-based bioparticles (eBPs).

MATERIALS AND METHODS

Laboratory beagle dogs were injected intradermally (ID) or subcutaneously (SC) with Der f 2-eBP three times at 2-week intervals. A basophil mediator release assay was used to compare the reactivity of Der f 2-eBPs to that of recombinant Der f 2. Allergen-specific IgG serum levels were determined by immunoblotting and ELISA. The allergen-blocking potential of postvaccination IgG was assessed by Pet Allergy Xplorer (PAX) macroarray and basophil mediator release inhibition assays.

RESULTS

The amount of Der f 2 eBPs needed to induce basophil activation was 1000-fold higher than that of the soluble natural allergen. In both immunisation groups, eBP injections caused no adverse events and induced Der f 2-specific IgG, first detected on Day (D)14 and peaking on D41. The co-incubation of sera with a Der f 2-IgE-rich canine serum pool resulted in a mean PAX inhibition of 70% (ID) to 80% (SC) on D41. For both groups, the inhibition of basophil mediator release reached 75% on D28 and D41. The percentage inhibition of PAX and mediator release correlated significantly with Der f 2 IgG levels.

CONCLUSION AND CLINICAL RELEVANCE

Intradermal and subcutaneous injections of Der f 2-eBPs were safe and increased Der f 2-specific IgG. The clinical benefit of immunotherapy will be evaluated in future trials enrolling atopic dogs allergic to house dust mites.

Identification of cross-reactive allergens between the Dermatophagoides farinae house dust mite and the Toxocara canis nematode in dogs with suspected allergies

BACKGROUND

Immunoglobulin (Ig)E cross-reactivity has been shown between Dermatophagoides farinae (Df; house dust mite) and the nematode Toxocara canis (Tc), yet its allergen basis is unknown.

OBJECTIVES

To identify the Df allergens IgE-cross-reactive with those of Tc.

ANIMALS

Archived sera from 73 dogs with suspected allergy sensitised to Df.

MATERIALS AND METHODS

We performed a combination of Pet Allergy Xplorer (PAX) and enzyme-linked immunosorbent assay (ELISA) inhibitions with excretory-secretory and somatic (i.e. nematode body) extracts of Tc or recombinant Tc tropomyosin on coats of Df, Der f 15 and Zen-1 (ELISA) or PAX allergens.

RESULTS

The ELISA and PAX inhibitions established that there is mutual yet variable cross-reactivity between the Tc excretory-secretory extract, purified Der f 15 and purified Zen-1. This cross-reactivity is likely to involve cross-reactive glycans, as there is no inhibition between the Tc excretory-secretory extract and recombinant Der f 15 without its predicted natural O-glycans. We also confirmed a heterogeneous cross-reactivity between the somatic Tc extract and Der p 11 (paramyosin), as well as between the recombinant Toxo c 3 and Der p 10 tropomyosins. The cross-reactivity among tropomyosins and paramyosins is likely to involve peptidic epitopes, as these recombinant allergens are not glycosylated.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs with suspected allergies, the cross-reactivity between Tc and Df for dogs is complex and heterogeneous. Some of the cross-reactive IgE recognises shared glycans on Der f 15 and Zen-1, while some targets peptidic epitopes on shared paramyosins and tropomyosins. We do not exclude that additional cross-reactive allergens between Df and Tc also might exist.

Extensive protein hydrolyzation is indispensable to prevent IgE-mediated poultry allergen recognition in dogs and cats

Background

The central premise for the commercialization of diets with hydrolyzed ingredients is that the small-sized digested peptides would be unable to crosslink allergen-specific IgE at the surface of tissue mast cells and induce their degranulation. Evidence for the validity of this concept to diagnose food allergies in dogs and cats is limited, however. Our objectives were to study the recognition of standard and variably hydrolyzed poultry extracts by sera from dogs and cats with elevated chicken-specific serum IgE.

Results

Forty sera from dogs and 40 from cats with undetectable, low, medium or high serum levels of chicken-specific IgE were tested by ELISA on plates coated with the positive controls chicken, duck and turkey meat extracts and the negative controls beef meat (dogs) or wheat (cats). Plates were also coated with a non-hydrolyzed chicken meal, and mildly- or extensively-hydrolyzed poultry feather extracts. The frequencies of dogs with positive IgE against the various extracts were: chicken meat: 100%, duck and turkey meats: 97%, beef meat: 3%, non-hydrolyzed chicken meal: 73%, mildly-hydrolyzed poultry feathers: 37% and extensively-hydrolyzed poultry feathers: 0%. For cats, these respective percentages were (with wheat replacing beef as a negative control): 100, 84, 97, 7, 7, 0 and 0%. To detect any allergenic cross-reactivity between poultry meat-based and feather hydrolysate-derived extracts, an IgE ELISA inhibition was also done. Ten canine sera with the highest level of anti-poultry IgE in the previous experiment were incubated overnight with a previously optimized 50 μg amount of each of the extracts used above. We performed ELISA on plates coated with chicken, duck or turkey meats with or without inhibitors. The median inhibition percentages after incubation with the non-hydrolyzed chicken meal were ~22%, with the mildly-hydrolyzed poultry feathers: 14–22%, and those with the extensively-hydrolyzed poultry feathers: 5 to 10%; the last inhibition level was similar to that of the beef meat negative control.

Conclusions

Altogether, these results suggest that an extensive—but not partial—hydrolyzation of the poultry feather extract is necessary to prevent the recognition of allergenic epitopes by poultry-specific IgE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1183-4) contains supplementary material, which is available to authorized users.

Therapeutic anti-IgE monoclonal antibody single chain variable fragment (scFv) safety and immunomodulatory effects after one time injection in four dogs

BACKGROUND

The therapeutic monoclonal antibody omalizumab that is specific for IgE has proven to be an effective addition to the treatment of allergic disease in humans.

HYPOTHESIS/OBJECTIVES

The aims of this study were to demonstrate the safety and immunomodulating effects of a single injection of a monoclonal antibody single chain variable fragments (scFv) specific for canine IgE in normal dogs.

ANIMALS

Three normal dogs were bled for EDTA whole blood samples for 112 days post-injection (dpi). A fourth dog was monitored for 28 days.

METHODS

Anti-IgE scFv was pegylated to minimize scFv dimerization. Four normal dogs were injected once subcutaneously with anti-IgE scFv at 1 mg/kg. Flow cytometry was performed on whole blood. Plasma levels of IgE were measured by ELISA.

RESULTS

None of the four dogs showed signs of anaphylaxis. All dogs demonstrated decreases in IgE(+) cells in lymphocyte-gated events by 14 dpi. Dogs C and D returned to pre-injection levels by 21 days, whereas dogs A and B remained below pre-injection levels until Day 112. Similar differences were seen in IgE-bearing granulocyte-gated cells. Free plasma IgE decreased below pre-injection levels by 47% in Dog A and by 52% in Dog B at 112 days. Dogs C and D did not change by more than 32% from preinjection levels.

CONCLUSION

A single injection of monomeric, pegylated scFv with high affinity for dog IgE was demonstrated to be safe. Marked reduction in IgE-bearing lymphocytes and granulocytes accompanied by reduced "free" plasma IgE level in two of four dogs is analogous to omalizumab in humans.

Two loci on chromosome 5 are associated with serum IgE levels in Labrador retrievers

Crosslinking of immunoglobulin E antibodies (IgE) bound at the surface of mast cells and subsequent mediator release is considered the most important trigger for allergic reactions. Therefore, the genetic control of IgE levels is studied in the context of allergic diseases, such as asthma, atopic rhinitis, or atopic dermatitis (AD). We performed genome-wide association studies in 161 Labrador Retrievers with regard to total and allergen-specific immunoglobulin E (IgE) levels. We identified a genome-wide significant association on CFA 5 with the antigen-specific IgE responsiveness to Acarus siro. We detected a second genome-wide significant association with respect to the antigen-specific IgE responsiveness to Tyrophagus putrescentiae at a different locus on chromosome 5. A. siro and T. putrescentiae both belong to the family Acaridae and represent so-called storage or forage mites. These forage mites are discussed as major allergen sources in canine AD. No obvious candidate gene for the regulation of IgE levels is located under the two association signals. Therefore our studies offer a chance of identifying a novel mechanism controlling the host's IgE response.

Total IgE and allergen-specific IgE and IgG antibody levels in sera of atopic dermatitis affected and non-affected Labrador- and Golden retrievers

Canine atopic dermatitis (CAD) is an allergic skin disease associated with IgE and IgG antibodies (Ab) to environmental allergens. The aim of this study was to determine which other factors influence serum Ab levels in CAD-affected and non-affected dogs as this has only been poorly investigated in dogs so far. Total and allergen-specific IgE levels and Dermatophagoides farinae (DF)-specific IgG1 and IgG4 were measured by ELISA in sera of 145 CAD-affected and 271 non-affected Labrador- and Golden retrievers. A multivariable logistic regression analysis including the factors age, breed, gender, castration, clinical CAD status and allergen-specific immunotherapy (ASIT) was performed. Golden retrievers had more frequently total (OR=1.87, 95% CI=1.26-2.87, p<0.01) and specific IgE levels above the threshold value than Labrador retrievers, suggesting that genetic factors influence IgE levels in dogs. Castration was generally associated with low Ab levels (OR=0.43-0.65, p<0.05). Surprisingly, dogs with CAD did not have increased odds for high IgE against any of the allergens tested. ASIT with DF was associated with high DF-specific IgG1 (OR=4.32, 95% CI 1.46-12.8, p<0.01) but was not associated with DF-specific IgG4 or decreased IgE levels. Further studies are needed to understand the role of allergen-specific IgE in CAD and of IgG1 in ASIT.

Canine immunoglobulin E

Canine IgE discovery and characterization historically closely paralleled that of human IgE. The reason for this would seem to be the early recognition of the spontaneous manifestation of allergic diseases in dogs that are nearly identical to human allergic diseases. The discovery and characterization of human IgE being dependent upon its biological activity in sensitizing mast cells and basophils was matched early on by analogous approaches readily applied to dogs. Following the early work on IgE, cloning and sequencing of the IgE heavy chain, epsilon, lagged well behind the human and rodent for want of IgE producing canine myelomas. As with human allergic diseases, measurement of allergen-specific and total IgE in canine tissues and body fluids revealed the same associations with various disease manifestations that some times defied discovery of straight-forward cause and effect relationships because of the complexity of pathogenesis in spontaneous allergic disease. However it is clear that research on IgE in spontaneously allergic dogs offers many opportunities to explore novel immunotherapeutic approaches to the control of allergic disease that will benefit both dogs and humans.

Lack of detection of circulating skin-specific IgE autoantibodies in dogs with moderate or severe atopic dermatitis

Human patients with atopic dermatitis (AD) commonly exhibit IgE reactivity to cutaneous self-antigens. The presence of serum IgE autoantibodies appears to correlate with disease severity, and it is suspected to reflect or contribute to tissue damage. The objective of this study was to determine whether IgE autoantibodies specific for cutaneous antigens could be detected in the serum of dogs with AD. Serum was collected from 19 dogs with untreated moderate to severe AD and four specific-pathogen free (SPF) dogs. Indirect immunofluorescence was performed using normal canine skin collected at four different locations (concave ear, nose, medial thigh and lateral thorax), while Western immunoblotting was done using normal canine ear pinna epidermal and dermal extracts and reducing conditions. In both methods, IgE was detected using a monoclonal antibody specific for heat stable epitopes of canine IgE. At 1:10 dilution, specific IgE autoantibodies against cutaneous autoantigens were not detected, with either method, in AD and SPF canine sera. Either IgE autoreactivity is not associated with moderate to severe AD in dogs, or the methods employed herein were not sensitive enough to permit IgE autoantibody detection.

The role of mast cells in atopy: what can we learn from canine models? A thorough review of the biology of mast cells in canine and human systems

Mast cell research has largely focused on the role of these cells in the early phase of allergic reactions. However, their involvement may well extend beyond this stage, and even reach across nonallergic conditions. Mast cells from different sources have helped advance our knowledge of their biology. Although in vitro and in vivo research in this area has mainly focused on humans, such studies are limited by the extent to which cells from certain human tissues and/or human patients can be collected or studied. While rodents also provide valuable models with which to further our understanding of the behaviour of mast cells and their contribution to allergy, reported differences between human and murine mast cells, and, in some instances, the limitations of in vivo rodent models of mast cell-mediated allergic conditions, preclude their use. In this review, we introduce a relatively unknown mast cell population, that of the dog. Canine mast cells display many phenotypic and functional similarities with their human counterparts, and dogs develop spontaneous and induced allergic diseases that share clinical and pathophysiological features with the human condition. Therefore, the use of canine cells can shed light on the general role of mast cells, particularly in relation to allergic diseases given the potential of in vivo dog models within this field. Here we provide a detailed review of the data reported from in vitro and in vivo studies of canine mast cells, and compare them with results obtained in human systems. We also highlight direct evidence of the mast cell contribution to canine atopy. We conclude that the dog offers useful in vitro and in vivo models in which to investigate mast cell behaviour, and that its use should be considered when undertaking studies aimed either at elucidating the role of mast cells in health and disease, or at prescreening novel therapies prior to entry into man.

Effects of routine prophylactic vaccination or administration of aluminum adjuvant alone on allergen-specific serum IgE and IgG responses in allergic dogs

OBJECTIVE

To determine the acute corn-specific serum IgE and IgG, total serum IgE, and clinical responses to s.c. administration of prophylactic vaccines and aluminum adjuvant in corn-allergic dogs.

ANIMALS

20 allergic and 8 nonallergic dogs.

PROCEDURE

17 corn-allergic dogs were vaccinated. Eight clinically normal dogs also were vaccinated as a control group. Serum corn-specific IgE, corn-specific IgG, and total IgE concentrations were measured in each dog before vaccination and 1 and 3 weeks after vaccination by use of an ELISA. The corn-allergic dogs also had serum immunoglobulin concentrations measured at 8 and 9 weeks after vaccination. Twenty allergic dogs received a s.c. injection of aluminum adjuvant, and serum immunoglobulin concentrations were measured in each dog 1, 2, 3, 4, and 8 weeks after injection. The allergic dogs were examined during the 8 weeks after aluminum administration for clinical signs of allergic disease.

RESULTS

The allergic dogs had significant increases in serum corn-specific IgE and IgG concentrations 1 and 3 weeks after vaccination but not 8 or 9 weeks after vaccination. Control dogs did not have a significant change in serum immunoglobulin concentrations after vaccination. After injection of aluminum adjuvant, the allergic dogs did not have a significant change in serum immunoglobulin concentrations or clinical signs.

CONCLUSIONS AND CLINICAL RELEVANCE

Allergen-specific IgE and IgG concentrations increase after prophylactic vaccination in allergic dogs but not in clinically normal dogs. Prophylactic vaccination of dogs with food allergies may affect results of serologic allergen-specific immunoglobulin testing performed within 8 weeks after vaccination.

The immunopathogenesis of flea allergy dermatitis in dogs, an experimental study

In this study, we investigated the development of clinical disease and immune responses in the development of an experimental model of flea allergy dermatitis. Dogs were randomly divided into four treatment groups and were infested with fleas on two different feeding schedules (continuous and episodic). Group 1 consisted of four non-exposed dogs (negative controls) and Group 2 consisted of six dogs exposed to fleas continually. Groups 3 and 4 consisted of 14 dogs each that were exposed to fleas on an episodic schedule (two consecutive days every other week for 12 weeks). Group 4 also received intraperitoneal injections of a low dose of lectin (ricin) with immunomodulatory properties. The purpose of Group 4 was to investigate the effects of ricin on enhancing the development of clinical signs, flea antigen-specific IgE levels and altering the number of CD4+ and CD8+ T cell subsets in peripheral blood. Clinical signs developed in all flea exposed dogs, however, the dermatology lesion scores were less and shorter in duration for continuously exposed dogs compared to episodic exposed dogs, independent of ricin treatment. Lesion development was concentrated in the flea triangle and consisted principally of erythema, followed by alopecia, excoriation, papules, and crusts. CD4+ and CD8+ lymphocyte subsets or IgE levels were not altered by ricin treatment. Flea antigen-specific IgE values were highest in dogs exposed to fleas on a continuous basis compared to those episodically exposed. A greater percentage of clinical responder dogs with negative flea-specific IgE titers or negative intradermal test (IDT) were present in the episodic exposure groups than in the continuous exposure group. IgE titers corresponded slightly better with clinical responders than the IDT. The agreement between the IgE titers and IDT was good (weighted K = 0.67). Histopathology of skin samples were consistent with a Type I hypersensitivity. In conclusion, we were able to develop a model of flea allergy dermatitis by experimentally exposing dogs to fleas on an episodic and continuous feeding schedule. In this study, continuously exposed dogs did not develop immunotolerance, and ricin did not enhance the development of FAD.

Evaluation of the clinical and allergen specific serum immunoglobulin E responses to oral challenge with cornstarch, corn, soy and a soy hydrolysate diet in dogs with spontaneous food allergy

Fourteen dogs with known clinical hypersensitivity to soy and corn were maintained on a limited antigen duck and rice diet until cutaneous manifestations of pruritus were minimal (78 days). Sequential oral challenges with cornstarch, corn and soy were then performed. Subsequently, the dogs were fed a diet containing hydrolysed soy protein and cornstarch. Throughout the study period the dogs were examined for cutaneous manifestations of pruritus and, additionally, serum was collected for measurement of allergen-specific and total immunoglobulin (Ig)E concentrations. Intradermal testing with food antigens was performed prior to entry into the study and after 83 days. A statistically significant clinical improvement was measured between days 0 and 83. Significant pruritus was induced after oral challenge with cornstarch, corn and soy (P = 0.04, 0.002, 0.01, respectively) but not with the hydrolysed diet (P = 0.5). The positive predictive value of the skin test for soy and corn allergy was reduced after feeding a soy and corn free diet. Although increases in soy and corn-specific serum IgE concentrations were measured in individual dogs post challenge they were not statistically significant and could not be used to predict clinical hypersensitivity.

Serum IgE and IgG responses to food antigens in normal and atopic dogs, and dogs with gastrointestinal disease

In human food allergy, with or without concurrent atopy, there may be significant increases in serum allergen-specific IgE. Serological methods have been tried but are not currently recommended for diagnosis of suspected food allergy in dogs. The aim of this study was to investigate humoral immune responses to food antigens in dogs. Serum IgG and IgE antibodies specific for food antigens were measured by enzyme linked immunosorbent assay (ELISA) using polyclonal anti-dog IgG and IgE reagents. Antigens tested were beef, chicken, pork, lamb, chicken, turkey, white fish, whole egg, wheat, soybean, barley, rice, maize corn, potato, yeast and cow's milk. Three groups were examined: normal dogs, dogs with atopic dermatitis (AD); and dogs with one of four types of gastrointestinal (GI) disease: small intestinal bacterial overgrowth (SIBO), inflammatory bowel disease (IBD), food-responsive disease, and infectious diarrhoea. Statistically significant differences in food-specific antibodies were not detected between the GI subgroups. There were statistically significant differences in the IgE concentration between the normal dogs, and dogs with atopic or GI disease, for all of the antigens tested. There were statistically significant differences in the average IgG concentrations between the normal dogs, and dogs with atopic or GI disease, for all of the antigens tested, except egg and yeast. The relationship of antigen responses for pooled data was analysed using principle component analysis and cluster plots. Some clustering of variables was apparent for both IgE and IgG. For example, all dogs (normal and diseased) made a similar IgG antibody response to chicken and turkey. Compared with other groups, atopic dogs had more food allergen-specific IgE and this would be consistent with a Th(2) humoral response to food antigens. Dogs with GI disease had more food allergen-specific IgG compared with the other groups. This may reflect increased antigen exposure due to increased mucosal permeability which is a recognised feature of canine intestinal disease.

Acaroid mite, intestinal and urinary acariasis

AIM: To investigate epidemiology and pathogenic mite species of intestinal and urinary acariasis in individuals with different occupations.

METHODS: A total of 1994 individuals were tested in this study. History collection, skin prick test and pathogen identification were conducted. The mites were isolated from stool and urine samples by saturated saline flotation methods and sieving following centrifugation, respectively.

RESULTS: Among the 1994 individuals examined, responses to the skin prick test of “+++”, “++”, “+”, “±” and “-” were observed at frequencies of 3.96% (79), 3.21% (64), 2.31% (46), 1.25% (25) and 89.27% (1780), respectively. A total number of 161 (8.07%) individuals were shown to carry mites, with 92 (4.61%) positive only for stool samples, 37 (1.86%) positive only for urine samples and 32 (1.60%) for both. The positive rate of mites in stool samples was 6.22% (124/1994), being 6.84% (78/1140) for males and 5.39% (46/854) for females. No gender difference was observed in this study (χ² = 1.77, P > 0.05). The mites from stool samples included Acarus siro, TyroPhagus putrescentiae, Dermatophagoides farinae, D. pteronyssinus, Glycyphagus domesticus, G.ornatus, Carpoglyphus lactis and Tarsonemus granaries. The positive rate of mites in urine samples was 3.46% (69/1994). The positive rates for male and female subjects were found to be 3.95% (45/1140) and 2.81% (24/854) respectively, with no gender difference observed (χ² = 1.89, P > 0.05). Mites species in urine samples included Acarus siro, Tyrophagus putrescentiae, T. longior, Aleuroglyphus ovatus, Caloglyphus berlesei, C. mycophagus, Suidasia nesbitti, Lardoglyphus konoi, Glycyphagus domesticus, Carpoglyphus lactis, Lepidoglyphus destructor, Dermatophagoides farinae, D. pteronyssinus, Euroglyphus magnei, Caloglyphus hughesi, Tarsonemus granarus and T. hominis. The species of mites in stool and urine samples were consistent with those separated from working environment. A significant difference was found among the frequencies of mite infection in individuals with different occupations (χ² = 82.55, P < 0.001), with its frequencies in those working in medicinal herb storehouses, those in rice storehouse or mills, miners, railway workers, pupils and teachers being 15.89% (68/428), 12.96% (53/409), 3.28% (18/549), 2.54% (6/236), 5.10% (13/255) and 2.56% (3/117), respectively.

CONCLUSION: The prevalence of human intestinal and urinary acariasis was not associated with gender, and these diseases are more frequently found in individuals working in medicinal herb, rice storehouses or mills and other sites with high density of mites. More attention should be paid to the mite prevention and labor protection for these high-risk groups.

IgE is present on peripheral blood monocytes and B cells in normal dogs and dogs with atopic dermatitis but there is no correlation with serum IgE concentrations

Blood was collected from 29 dogs, 14 with atopic dermatitis (AD) and 15 controls. Total serum IgE was quantitated. Peripheral blood monocytes were harvested and labeled with leucocyte markers and anti-canine IgE before analysis by flow cytometry. There was no statistically significant difference between the atopic and control groups when the mean number of cells in the monocyte (CD14), antigen presenting cell (CD1c) or B cell (CD21) populations were examined. However, the variation in cell numbers was significant and much greater in the atopic group for CD1c and CD14 labeled cells. The mean percentage of double labeled cells, CD1c/IgE and CD14/IgE was significantly lower in the atopic population compared with the controls. More variation was observed in the numbers of monocytes of atopic dogs (CD14/IgE) and antigen presenting cells (CD1c/IgE) of control dogs. The mean percentage of B cells expressing IgE was 65 and 51% in the atopic and control groups respectively which is greater than that reported in humans. There was no statistically significant difference. Total serum IgE concentrations were similar in each group and did not correlate with cell bound IgE in any of the leucocyte populations studied. Canine AD is associated with more variability in circulating monocyte numbers and lower numbers of monocytes expressing IgE than control dogs. Unlike in humans, there is no correlation between circulating and cell bound IgE. Furthermore, high levels of IgE in the dog may be related to a greater number of B cells in the circulation committed to IgE production.

Skin mast cell histamine release following stem cell factor and high-affinity immunoglobulin E receptor cross-linking in dogs with atopic dermatitis

Stem cell factor (SCF) influences mast cell activation and inflammatory mediator release, and is elevated in tissues undergoing allergic inflammation. Wheal formation in response to the injection of SCF or anti-immunoglobulin (Ig)E antibody injection was compared between normal (n = 10) and nonlesional atopic (n = 10) canine skin. In situ SCF secretion was compared between lesional and nonlesional skin using immunohistochemistry. Histamine release by skin cell suspensions after stimulation with SCF, concanavalin A (ConA) or rabbit anticanine IgE antibodies was compared between normal and atopic dogs. All dogs exhibited strong responses to intradermal SCF injection at 10 and 50 ng mL(-1). Atopic dogs had significantly (P = 0.002) larger wheal responses to anti-IgE than normal dogs; but there was no difference in numbers of skin mast cells bearing IgE as detected by immunohistochemistry. Only atopic dogs exhibited interstitial deposition of SCF in both lesional and nonlesional skin specimens. Median histamine release stimulated by SCF in the absence of IgE from lesional skin cells was higher in atopic than normal dogs (P = 0.04). These experiments suggest that dermal SCF secretion could potentiate histamine release following IgE receptor cross-linking and thus, could be one of the explanations for the inherent mast cell hyperexcitability observed in canine atopic dermatitis.

In vitro IgE but not IgG production of canine peripheral blood B cells is inhibited by CD40 ligation

The aim of this study was to investigate in vitro IgE induction in peripheral canine B cells. CD21(+) B cells were purified from the peripheral blood of beagle dogs by positive selection via magnetic separation to a purity of >/=95%. Subsequently, proliferation, and IgG and IgE production of canine B cells were investigated after stimulation with human recombinant Interleukin-4 (hrIL-4) and human recombinant Interleukin-2 (hrIL-2) in the presence or absence of CD40L-CD8 fusion protein (CD40L) of mouse origin. We could demonstrate that canine B cells react on hrIL-2 alone by proliferation and IgG production but not by IgE secretion, whereas activation with hrIL-4 induced proliferation and mainly IgE production. Together, both cytokines synergistically increased B cell proliferation as well as IgG and IgE production. We could also show that mouse CD40L induces proliferation of dog B cells, which is further enhanced by addition of hrIL-4. Unexpectedly, CD40L led to a dramatic decrease in the IL-4 mediated IgE secretion (82% inhibition on an average). In contrast, IgG production was not affected significantly by CD40L. The same effects of CD40L were observed when B cells were stimulated by a combination of IL-2 and IL-4 and this inhibition could not be abrogated by increasing the amounts of IL-4. In summary, activation of canine B cells from peripheral blood by hrIL-4 in the presence or absence of hrIL-2 led to marked IgE production that is strongly and in a dose-dependent manner inhibited by CD40L. Stimulation of IgG production is not influenced by CD40L.

Veterinary sources of nonrodent monoclonal antibodies: interspecific and intraspecific hybridomas

The generation of monoclonal antibodies from species other than rats and mice has developed slowly over the last 20 years. The advent of antibody engineering and realization of the advantages of nonmurine antibodies, in terms of their superior affinities and specificities, and their potential as components of human and veterinary therapeutics has increased their relevance recently. There have been significant advances in the development of myeloma and heteromyeloma fusion partners. This is an opportune moment to consolidate experiences of MAb production across the range of species of veterinary interest and place it into context with other developments in the field of monoclonal antibodies. The background to the development of antibodies from species other than the mouse is discussed. The species and antigens used to date are reviewed, as are the methods and results reported. A suggested protocol is provided for first attempts to exploit the huge potential of this aspect of hybridoma technology and suggestions are made for its further expansion.

Capture ELISA and flow cytometry methods for toxicologic assessment following immunization and cyclophosphamide challenges in beagles

The purpose of this subacute 22-day study was to evaluate methods for canine circulating immunoglobulins (IgM, IgG, and IgE) and select B- and T-lymphocyte populations (CD4-helpers, CD8-suppressors, pan-T and pan-B) for immunotoxicity testing using an organ system (concordance) approach. The challenge substance for immunoglobulin testing was repeated immunization with six-way distemper vaccination (DHLAPP), while the challenge substance for leukocyte subpopulations was treatment with cyclophosphamide. Immunoglobulin measurements were made by capture enzyme-linked immunosorbent assay (ELISA), and leukocyte immunophenotyping by fluorescein isothiocyanate/phycoerythrin conjugation (flow cytometry). A battery of parameters that would be used in a typical regulatory study were taken to aid interpretation of the data generated by these methods. Body weights, food consumption, clinical observations, complete clinical chemistry and urinalysis measurements were taken. Gross pathology and micropathology of sternal bone marrow, spleen, mesenteric and retropharyngeal lymph nodes, thymus, liver and kidney were completed. The ELISA method demonstrated acceptable intra-assay reproducibility for IgM, IgG and IgE, with values in good agreement as reported for radial immunodiffusion. The immunologic challenge demonstrated a biological trend of an increase in IgM that preceded an increase in IgG with no discernible trend in IgE response, and no abnormalities in lymphocyte subpopulations. Principle flow cytometry findings related to cyclophosphamide were that the relative percent of B cells decreased dramatically and progressively after compound administration; being statistically decreased in males on day 22 compared with day -5. The relative percent CD4 and CD8 contribution increased, but the CD4/CD8 ratio remained relatively unchanged as total white blood cells decreased progressively. The increase in relative percent CD4 (males only) was statistically significant according to a two-sample t-test on days 17, 20 and 22 when compared with the pre-treatment day -5. There was a relative percent increase in CD5-panT, but absolute numbers were dramatically decreased. We conclude that an organ system approach to assessment of the immune system which incorporates humoral antibody, enumeration of lymphocyte populations and pathologic evaluation of the lymphoreticular organs assists in the interpretation of an adverse toxicological response. The ELISA method for measurement of Igs detected the expected levels of IgG, IgM and IgE due to repeated vaccinations and to cyclophosphamide treatment. The flow cytometry method was acceptable for measuring select canine lymphocyte populations and detecting the expected decrease in B cells due to cyclophosphamide treatment. Both methods may be added to a testing battery for assessing immunotoxicityl in canine regulatory studies.

Total serum IgE and IgA antibody levels in healthy dogs of different breeds and exposed to different environments

Total serum immunoglobulin (Ig) E and A levels were analysed in 233 healthy dogs as basis for comparison with atopic dogs in future studies. They were measured by ELISA in a group of non- colonised dogs of various breeds (group A) and three groups of colonised dogs including one German Shepherd and two Beagle kennels (groups B-D). IgE levels from non-colonised dogs were significantly higher than the ones of German Shepherds and Beagles C (P<0.05). IgA levels were alike in all groups except for the German Shepherds which displayed the lowest levels. Age and sex were not identified as common significant cofactors for IgE and IgA levels in all groups and IgE levels correlated negatively with IgA only in non-colonised dogs. In conclusion, IgE and IgA levels seem to be mainly influenced by genetic background. Thus use of total serum IgE as a diagnostic tool in the atopic dogs required extensive family data and therefore appears most suitable for research purposes within specific, well defined dog populations.

Domain mapping and comparative binding features of eight dog IgE-specific reagents in ELISA, immunoblots, and immunohistochemistry

Eight dog IgE-specific reagents including monoclonal and polyclonal antibodies (Ab) and a cross-reactive alpha chain of the human high affinity IgE receptor were mapped to recombinant fragments of the second (IgEf2) and third/fourth (IgEf3/4) domains of the dog IgE heavy chain. In ELISA, five out of eight reagents reacted to solid-phase bound IgEf2, of which two polyclonal Ab bound in addition to IgEf3/4. All Ab which recognized at least one recombinant IgE fragment, also bound to IgE in ELISA, immunoblots, and immunohistochemistry. In contrast, only one monoclonal Ab, that did not bind to the recombinant IgE fragments, reacted with immunoblots of serum and immunohistochemistry. The alpha chain could only be applied to ELISA with serum IgE. Furthermore, there was a wide range of heat-lability of binding reactions. Comparative analysis of available dog IgE-specific reagents enables more in-depth functional studies on IgE-mediated phenomena in dogs, and helps to further establish the dog as an animal model for allergy research.