Development of an enzyme-linked immunosorbent assay for the detection of IgG subclasses in the serum of normal and diseased dogs

Immunoglobulin G1 subclass responses can be used to detect specific allergy to the house dust mites Dermatophagoides farinae and Dermatophagoides pteronyssinus in atopic dogs

BACKGROUND

In dogs with atopic dermatitis, intradermal testing (IDT) or allergen specific IgE serological testing are routinely employed to identify causative allergens. These allergens can then be used for allergen-specific immunotherapy and allergy management. The clinical relevance of this testing is affected by the source of allergen, and other biomarkers that are more related to specific allergens still need to be identified. The aim of this study was to investigate levels of specific IgE, total IgG, and IgG1 and IgG2 subclasses against the local house dust mites (HDM) Dermatophagoides farinae (DF) and D. pteronyssinus (DP) as biomarkers by using in-house ELISAs in healthy (n = 33) and atopic dogs (AD) (n = 44) that were either positive or negative by IDT to HDM.

RESULTS

Being over 3 years of age was a risk factor for AD (Odds Ratio (OD) = 4.10, 95% Confidence interval (CI) 1.57-10.75, p = 0.0049), but there was no relation to IDT outcomes (OR = 0.9091, 95% CI 0.22-3.74, p = 1.00). High levels of all antibody isotypes (IgE, IgG, IgG1 and IgG2) against HDM were found in aged healthy dogs (> 3 years old). In AD, HDM-IgE and IgG1 levels were higher in dogs that were IDT positive to HDM than in IDT negative animals. Levels of IgE and IgG1 could be used to distinguish the specific allergens, whereas total IgG and IgG2 levels were not different between IDT-positive and IDT-negative AD. By the receiver operating characteristic curve at a false-positive rate = 0.10, both IgE and IgG1 showed better sensitivity than IgG and IgG2. Similar to IgE, serum IgG1 concentration was also relevant to IDT outcomes.

CONCLUSIONS

Our in-house ELISAs coated with local HDM were useful for evaluating antibody levels, and we propose use of the HDM-specific IgG1 subclass as a biomarker to detect HDM specific allergens in AD, potentially together with an IgE based platform.

Infection of dogs by Leishmania infantum elicits a general response of IgG subclasses

Leishmania infantum is the etiological agent of zoonotic visceral leishmaniasis. In endemic areas, canine infections are considered the main source of infection for human populations. Therefore, any control of human leishmaniasis must include the control of canine infections. Chemotherapy of leishmaniasis is inadequate and canine immunoprophylaxis has important limitations. Reports on the response of infected dogs are abundant but no clear picture of immune events has emerged. To shed some light on these shortcomings the specific IgG subclass response was followed in 20 Beagle dogs experimentally infected with L. infantum using monoclonal antibodies (MAb) specific for canine IgG₁, IgG₂, IgG₃ and IgG₄, along with ELISA and flow cytometry. Results showed that parasitic infection elicits a general response of all IgG subclasses, with a predominant IgG₁ response and without any evidence of IgG₁/IgG₂ dichotomy. These findings suggest that the inconsistent results reported previously could be related to the lack of specific reagents and not to the actual differences in the immune response of infected animals. Differential IgG subclass reactivity in ELISA and cytometry and the analysis of the reacting antigens could facilitate the diagnosis and prognosis of the disease and provide a useful tool for adequate therapeutics and vaccine development against leishmaniasis.

Chronic Inflammatory Disease in the Pancreas, Kidney and Salivary Glands of English Cocker Spaniels and Dogs of Other Breeds Shows Similar Histological Features to Human IgG4-related Disease

Chronic pancreatitis (CP) is a common disease in the English cocker spaniel (ECS) and is characterized histologically by duct destruction, interlobular fibrosis and dense periductular and perivenous lymphocytic aggregates. These features are also found in human autoimmune pancreatitis type 1, part of a glucocorticoid-responsive, multiorgan syndrome, newly recognized as IgG4-related disease (IgG4-RD). Human IgG4-RD affects one or several organs, often showing a predominance of IgG4⁺ plasma cells histologically, with an IgG4⁺:total IgG⁺ plasma cell ratio of >40%. This study investigated whether ECSs with CP and/or inflammatory disease in several organs show an increase in IgG4⁺ plasma cells within affected tissues. Histological sections of pancreas, liver, kidney, salivary gland and conjunctiva were obtained from ECSs with idiopathic chronic inflammatory disease affecting those tissues. Tissue samples from age-matched dogs of other breeds with similar diseases were also sampled. Control diseased tissue samples, from dogs without a suspected immune-mediated disease, were included. A subset of ECSs and dogs of other breeds presented with disease in more than one organ. Immunohistochemistry was performed with primary reagents detecting total IgG and three of the four canine IgG subclasses (IgG2, IgG3 and IgG4). Normal sections of pancreas and liver showed an absence of labelled plasma cells of any subclass. Normal kidney and salivary gland sections showed the presence of a few labelled plasma cells (<10 plasma cells/high-power field). Fourteen tissue sections from 12 ECSs and seven sections from six dogs of other breeds showed elevated numbers of IgG4⁺ plasma cells and IgG4⁺:IgG⁺ ratios >40%. Individual dogs (ECSs and other breeds) showed marked increases in IgG4⁺ cells. There were no significant differences in the number of IgG4⁺ plasma cells between ECSs and dogs of other breeds for affected pancreas, liver, salivary glands and conjunctiva. Kidney sections had more IgG4⁺ cells, for both ECSs and dogs of other breeds, than did sections from other organs. Dogs of other breeds had significantly more IgG4⁺ plasma cells in affected kidneys than ECSs. In conclusion, several ECSs and dogs of other breeds fulfilled the histological criteria for the diagnosis of IgG4-RD, supporting the existence of a multiorgan immune-mediated disease in ECSs and some dogs of other breeds.

Identification of canine IgG and its subclasses, IgG1, IgG2, IgG3 and IgG4, by immunofixation and commercially available antisera

Immunofixation is a diagnostic and research tool used for characterizing the electrophoretic location of immunoglobulin fractions in serum and urine. Commercially available polyclonal antisera which discriminate two IgG subclasses (IgG1 and IgG2) are available and commonly used. More recently, four IgG subclasses have been defined in the dog based on cDNA data. Archived serum from 16 dogs with naturally occurring monoclonal or biclonal gammopathies were characterized using routine serum protein electrophoresis, routine immunofixation and LCMS/MS as 3 IgA, 3 IgM, 2 IgG2, 7 IgG3 and 2 IgG4 heavy chain predominant cases. Immunofixation reactivity of a panel of commercially available antisera to these cases was characterized. The anti-human IgG antisera was the only tested antisera which bound all canine IgG restricted bands without also labelling IgA or IgM heavy chains or light chains. The tested polyclonal antisera labeled as reacting with canine IgG2 bound canine IgG2, IgG3, IgA and IgM and may label IgG1. The tested polyclonal antisera labeled as reacting with canine IgG1 bound the canine IgG4 bands but not those identified as IgA, IgM, IgG2 or IgG3 and likely did not bind IgG1. This data suggests that commercially available polyclonal IgG1 antisera (Bethyl A40 - 120A and Bio-Rad AHP947) can be used to positively but possibly not selectively identify canine IgG4 by immunofixation.

Antibody levels to Malassezia pachydermatis and Staphylococcus pseudintermedius in atopic dogs and their relationship with lesion scores

BACKGROUND

Elevated immunoglobulin E (IgE) levels to Malassezia or Staphylococcus species in human atopic dermatitis are related to the skin severity index; a similar association has not been reported in atopic dogs.

OBJECTIVES

To investigate serum levels of allergen-specific IgE, total specific IgG and IgG subclasses (IgG1 and IgG2) for M. pachydermatis and S. pseudintermedius, and to correlate them with the severity of dermatitis in dogs.

ANIMALS

Serum samples were collected from dogs categorized by age and disease status. Groups 1 and 2: <3-year-old healthy (n = 9) and atopic dogs (n = 9), respectively; and groups 3 and 4: ≥3-year-old healthy (n = 11) and atopic dogs (n = 14), respectively.

METHODS AND MATERIALS

Antibody levels were measured by ELISA. The Canine Atopic Dermatitis Lesion Index (CADLI) was analyzed in relation to antibody levels.

RESULTS

Specific IgE and total IgG against M. pachydermatis and S. pseudintermedius were significantly increased in atopic dogs of all ages. Although differences between atopic and healthy dogs, with regard to specific IgG1 and IgG2 levels to each microbe, varied in significance within age groups. No significant relationships were found between the CADLI and any specific immunoglobulin levels for both microbe types.

CONCLUSIONS AND CLINICAL IMPORTANCE

In dog skin, microbes may act as allergens triggering inflammatory responses via IgE- and IgG-dependent pathway(s). The affinity of the IgG subclass produced may vary according to antigen type. Specific IgE levels may be related to clinical disease in dogs and not to skin lesion severity.

Immunoglobulin G4-related disease in a dog

Immunoglobulin G4-related disease (IgG4-RD), which affects many organ systems, has been recognized as a distinct clinical entity in human medicine for just over a decade but has not been previously identified in dogs. In humans, IgG4-RD is characterized by diffuse IgG4-positive lymphoplasmacytic infiltrates that commonly lead to increased serum concentrations of IgG4 and IgE, peripheral eosinophilia, tumorous swellings that often include the parotid salivary glands, obliterative phlebitis, and extensive fibrosis. Herein we describe the diagnosis, clinical progression, and successful treatment of IgG4-RD in an 8-year-old female spayed Husky mixed breed dog. Immunoglobulin G4-related disease should be considered as a differential diagnosis for dogs with vague clinical signs, lymphoplasmacytic swellings, restricted polyclonal gammopathy, eosinophilia or some combination of these findings.

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.

Use of ELISA employing homologous and heterologous antigens for the detection of IgG and subclasses (IgG1 and IgG2) in the diagnosis of canine visceral leishmaniasis

Indirect immunofluorescence is the method recommended for the diagnosis of visceral leishmanisis in dogs, however, the accuracy of this technique is low and its use on a large scale is limited. Since ELISA does not present these limitations, this technique might be an option for the detection of IgG or specific IgG1 and IgG2 subclasses. Canine ehrlichiosis is an important differential diagnosis of American Visceral Leishmaniasis (AVL). The present study compared ELISA using Leishmania chagasi and Leishmania braziliensis antigen for the detection of anti-Leishmania IgG and subclasses in serum samples from 37 dogs naturally infected with L. chagasi (AVL) and in samples from four dogs co-infected with L. braziliensis and L. chagasi (CI). The occurrence of cross-reactivity was investigated in control serum samples of 17 healthy dogs (HC) and 35 infected with Ehrlichia canis (EC). The mean optical density obtained for the detection of IgG was significantly higher when L. chagasi antigen was used, and was also higher in subgroup VLs (symptomatic) compared to subgroup Vla (asymptomatic). The correlation between IgG and IgG1 was low. The present results suggest that IgG ELISA using homologous antigen yields the best results, permitting the diagnosis of asymptomatic L. chagasi infection and the discrimination between cases of AVL and ehrlichiosis in dogs.

Canine antibody response to Phlebotomus perniciosus bites negatively correlates with the risk of Leishmania infantum transmission

Background

Phlebotomine sand flies are blood-sucking insects that can transmit Leishmania parasites. Hosts bitten by sand flies develop an immune response against sand fly salivary antigens. Specific anti-saliva IgG indicate the exposure to the vector and may also help to estimate the risk of Leishmania spp. transmission. In this study, we examined the canine antibody response against the saliva of Phlebotomus perniciosus, the main vector of Leishmania infantum in the Mediterranean Basin, and characterized salivary antigens of this sand fly species.

Methodology/Principal Findings

Sera of dogs bitten by P. perniciosus under experimental conditions and dogs naturally exposed to sand flies in a L. infantum focus were tested by ELISA for the presence of anti-P. perniciosus antibodies. Antibody levels positively correlated with the number of blood-fed P. perniciosus females. In naturally exposed dogs the increase of specific IgG, IgG1 and IgG2 was observed during sand fly season. Importantly, Leishmania-positive dogs revealed significantly lower anti-P. perniciosus IgG2 compared to Leishmania-negative ones. Major P. perniciosus antigens were identified by western blot and mass spectrometry as yellow proteins, apyrases and antigen 5-related proteins.

Conclusions

Results suggest that monitoring canine antibody response to sand fly saliva in endemic foci could estimate the risk of L. infantum transmission. It may also help to control canine leishmaniasis by evaluating the effectiveness of anti-vector campaigns. Data from the field study where dogs from the Italian focus of L. infantum were naturally exposed to P. perniciosus bites indicates that the levels of anti-P. perniciosus saliva IgG2 negatively correlate with the risk of Leishmania transmission. Thus, specific IgG2 response is suggested as a risk marker of L. infantum transmission for dogs.

Leishmania infantum is the causative agent of zoonotic visceral leishmaniasis in the Mediterranean Basin and Phlebotomus perniciosus serve as the major vector. In the endemic foci, Leishmania parasites are transmitted mostly to dogs, the main reservoir host, and to humans. We studied the canine humoral immune response to Phlebotomus perniciosus saliva and its potential use as a marker of sand fly exposure and consequently as a risk marker for Leishmania transmission. We also characterized major salivary antigens of P. perniciosus. We demonstrated that under laboratory conditions, the levels of anti-P. perniciosus saliva antibodies positively correlated with the number of blood-fed sand flies and therefore, may be used to evaluate the need for, and the effectiveness of, anti-vector campaigns. In parallel, we studied sera of dogs naturally exposed to P. perniciosus in highly active focus of canine leishmaniasis in Southern Italy. Specific antibodies against P. perniciosus saliva were significantly increased according to the ongoing sand fly season. Moreover, the levels of anti-P. perniciosus antibodies in naturally bitten dogs negatively correlated with anti-Leishmania seropositivity. Thus, for dogs living in endemic areas, specific antibody response against saliva of the vector is an important marker for estimating the risk of Leishmania transmission.

Comparison of monoclonal and polyclonal antibodies for the detection of canine IgG1 and IgG2, and associations with infection outcome in Leishmania infantum naturally infected dogs

In murine models of leishmaniasis, IgG subclass expression is a proxy measure for Th1/Th2 cellular immune response bias. However, in dogs, the reservoir of zoonotic visceral leishmaniasis, no consistent association has been described between IgG subclass ratios and disease resistance. Inconsistent results may reflect lack of specificity of commonly used commercial antibodies. Our aim was to measure IgG1 and IgG2 responses to crude Leishmania antigen using commercial polyclonal antibodies for comparison with a panel of commercially unavailable monoclonal antibodies, in a cohort of 60 naturally infected dogs, and to compare associations between subclass responses and clinical or parasitological outcomes. IgG1 and IgG2, measured by both antibodies, were higher in clinically symptomatic than in asymptomatic dogs (P</=0.03), reflecting general upregulation of IgG in infected dogs. Unlike the murine model, canine IgG2:IgG1 ratios were not predictive of clinical or parasitological outcomes of infection. Associations between subclass levels and positivity by bone marrow culture and PCR were not consistent when measured with different antibodies. Further research is needed to re-evaluate the specificity of commercially available IgG subclass antibodies.

IgG subclass profile of serum antibodies to Leishmania chagasi in naturally infected and vaccinated dogs

Leishmaniosis is a zoonotic disease that is caused by Leishmania chagasi and transmitted by sandflies. In Brazil, canine visceral leishmaniosis (CVL) is an emerging disease in urban areas and dogs are the main reservoir host. The aim of the present study was to analyze IgG seroconversion of dogs to L. chagasi and to determine whether there was dominance of any particular IgG subclasses in this immune response. Antibody detection was performed by ELISA with 120 sera from confirmed seropositive dogs (obtained from epidemiological surveys), 24 samples from naturally infected dogs with clinical signs of the disease, and 40 sera from animals immunized with a commercially available vaccine. Ninety percent of seropositive survey population samples had detectable levels of anti-Leishmania total IgG by ELISA, compared with 70% of samples from symptomatic animals and only 13% of samples from the immunized dogs. The serological response in each group displayed a distinct bias in IgG subclass usage as detected by application of a panel of monoclonal antibodies specific for canine IgG1-IgG4. The survey population, which comprised predominantly asymptomatic dogs, had a dominant IgG1 response, while symptomatic dogs had a mixed pattern of IgG subclass usage. In contrast, sera from vaccinated animals had high titres of IgG2 Leishmania antibody. These distinctive IgG subclass profiles may be related to the infection status of the dogs. Moreover, detection of antigen-specific IgG subclasses may provide a valuable diagnostic tool for predicting the clinical outcome of visceral leishmaniasis, as well as differentiating infected dogs from vaccinated animals.

Immunoglobulin G subclass distribution in canine leishmaniosis: A review and analysis of pitfalls in interpretation

Infection with Leishmania may have different outcomes in genetically distinct individuals and the course of infection is determined by the nature of the host innate and adaptive immune response. Thus in experimentally infected mice, and in naturally infected dogs or humans, the protective (self-healing or asymptomatic) phenotype is associated with the induction of Th1-regulated cell-mediated immunity. By contrast, a Th2-regulated humoral immune response is associated with severe symptomatic disease. In the murine model system there is strong correlation between clinicopathological phenotype and the nature of the antigen-specific humoral immune response. Symptomatic infection and Th2-regulation is associated with elevation in antigen-specific IgG1 and IgE, whereas asymptomatic infection with Th1-regulation is linked with IgG2a production. IgG subclass restriction is less clear in human disease with only some clinical forms being correlated to a specific serological profile. Although numerous studies have questioned whether infected dogs develop skewed IgG subclass usage, the results of these have been conflicting-suggesting bias towards IgG1 or IgG2 or neither subclass in different investigations. This confusion could relate to the specificity of the commercially available polyclonal antisera used to detect the canine IgG1 and IgG2 subclasses. More meaningful results might be obtained by the use of the panel of monoclonal antibodies with well-validated specificity for all four canine IgG subclasses.

Splenic immune responses during canine visceral leishmaniasis

Dogs are the main reservoir host for zoonotic visceral leishmaniasis caused by Leishmania infantum. In this study we investigated the immune response in spleens of L. infantum-infected dogs by measuring the mRNA expression levels for a wide panel of cytokines, transcription factors and chemokines. mRNA levels and parasite load were followed during 7 months of experimental infection and 14 months post-treatment, and were compared to naturally-infected (NI) dogs. Similarly, serum anti-Leishmania IgG and IgG subclass levels were measured during experimental infection. An increase in IFN-gamma, T-bet, IP-10 and RANTES was found in the experimentally and NI dogs, implicating a substantial type-1 immune response during canine visceral leishmaniasis. IL-4, a type-2 associated cytokine, increased as early as one month after experimental infection, while IL-5 was high at later stages. Interestingly, the expression levels of the Treg-associated cytokines, IL-10 and TGF-beta, did not change during the infection. Total anti-Leishmania IgG and IgG subclasses increased during the experimental infection. However, no association with specific cytokine patterns was observed. Parasite load in the spleens increased as early as one month post-infection and remained high until treatment. The load was higher in the polysymptomatic NI dogs than in the experimentally-infected dogs. This study indicates that both type-1 and type-2 immune responses occur in the spleen during canine L. infantum infection, and suggests that the early elevation of IL-4 might have a role in the persistence of parasites in the presence of high IFN-gamma expression.

Evaluation of IgG subclass responses against Dermatophagoides farinae allergens in healthy and atopic dogs

A semiquantitative chemiluminescent Western blot analysis system was developed and validated to evaluate antigen-specific IgG subclass responses to electrophoretically separated proteins of Dermatophagoides farinae in healthy and atopic dogs. Both groups mounted similar D. farinae-specific IgG1 and IgG4 responses to multiple antigens, but IgG2 and IgG3 responses were difficult to detect. The most commonly recognized bands in both groups were 18 and 98 kDa antigens for IgG1 and 18, 45, 66, 98, 130 and 180 kDa for IgG4. The number of bands recognized per dog did not differ significantly, but significantly more atopic dogs had an IgG1 response to a 180 kDa protein. The overall D. farinae-specific IgG1 and IgG4 responses were slightly higher, but not significantly different, in the healthy group. The results suggest that some antigens produced by D. farinae can induce different subclass responses. However, as most of these responses are seen in both healthy and atopic dogs, they are likely to merely represent recognition of foreign proteins presented to the immune system, rather than involvement in the pathogenesis of atopic dermatitis. The role of the 180 kDa antigen warrants further study.

Examination of serum total IgG1 concentration in atopic and non-atopic dogs

In this study, serum immunoglobulin G1 (IgG1) concentrations were examined in atopic and non-atopic dogs receiving different levels of parasite control. Significantly lower serum total IgG1 concentrations were found in non-atopic dogs receiving stringent parasite control than in atopic dogs or non-atopic dogs receiving less stringent parasite control. Examination of serum total IgG1 concentrations of atopic dogs after six months of allergen specific immunotherapy (ASIT) showed a significant increase in serum total IgG1 concentrations. It is proposed that serum total IgG1 concentrations are affected by parasitism, atopic dermatitis and ASIT.

Parental allergic status influences the risk of developing allergic sensitization and an asthmatic-like phenotype in canine offspring

Increasing evidence suggests that parental allergic status, especially that of the mother, may play a unique and important role in influencing the development of fetal infant immune responses to inhaled allergens, independently of genetic predisposition. We have developed an experimental model in dogs where the offspring from allergic parents, when exposed to inhaled allergen, develop allergic sensitization and an asthmatic phenotype, whereas the offspring from non-allergic parents do not. Offspring from ragweed-sensitized (two litters, n = 10) or non-sensitized (two litters, n = 11) Beagle dogs were exposed repeatedly, by inhalation, to ragweed or filtered air (negative control) beginning within 1 week after birth. Serum levels of total immunoglobulin (Ig)E, and ragweed-specific IgE and IgG, were measured at specific time-points up to 40 weeks after birth. Cell differentials in the bronchoalveolar lavage were determined on days 1 and 4 following ragweed instillation into the offspring's lungs at 26 weeks of age. Changes in pulmonary resistance following challenge with histamine and ragweed (five breaths) were measured at 40 weeks after birth. Offspring from sensitized parents exposed to ragweed developed elevated serum total IgE and ragweed-specific IgE and IgG, and showed an increased pulmonary resistance to histamine and ragweed, and increased numbers of eosinophils in bronchoalveolar lavage. In contrast, offspring from non-sensitized parents did not exhibit this immune response. These results suggest that parental allergic sensitivity is important in the development of allergic sensitization and an asthmatic phenotype in the offspring.

IgG subclass responses in a longitudinal study of canine visceral leishmaniasis

Visceral leishmaniasis (VL), caused by Leishmania infantum, is an important disease of domestic dogs. Here, we present data on the IgG subclass antibody response to crude L. infantum antigen in a cohort of naturally infected Brazilian dogs. Specific IgG1-IgG4 responses could be detected in 98, 58, 70 and 82%, respectively of 57 dogs that were seropositive for specific IgG. Levels of all IgG subclasses were strongly inter-correlated. Levels of all IgG subclasses increased at the time of seroconversion, before reaching a plateau after several months. Levels of all IgG subclasses were higher in sick dogs than healthy dogs, and levels of all except IgG2 were higher in parasite-positive (by PCR) than parasite-negative dogs. However, levels of IgG2 relative to IgG1 were lower in sick or parasite-positive dogs compared to healthy or parasite-negative infected dogs. In contrast to previous studies, the results suggest that canine VL is associated with upregulation of specific antibody of all IgG subclasses, particularly IgG1, IgG3 and IgG4.

Cloning and characterization of cDNAs encoding four different canine immunoglobulin gamma chains

cDNAs encoding four different canine immunoglobulin G (caIgG) gamma chains were identified in this study. One of these IgG gamma chain cDNAs, (caIgG-A), represents 92.5% of the IgG gamma chain cDNAs in a dog spleen cell cDNA library; a second partial IgG gamma chain cDNA (caIgG-B) was also identified in the library. The other two IgG gamma chain cDNAs (caIgG-C and caIgG-D) were RT-PCR amplified from canine lymphoma samples. Comparison of the four different canine IgG gamma chain cDNAs showed homologies from 83.6 to 89.2% and from 73.1 to 81.8% at nucleotide and amino acid sequence levels, respectively. Despite the high similarity in CH1, CH2 and CH3 domains among the different caIgG gamma chains, the hinge regions were distinct, sharing only 19.0-35.2% homology at the amino acid level. No multiple duplication of the hinge region, as reported for human IgG1 and IgG3, was detected in any of the canine IgG gamma chains. The numbers of cysteines in the putative hinge regions were found to be 3, 2, 7 and 3 for the four canine IgG heavy gamma chains (A, B, C and D), respectively. Specific primers were designed based on caIgG gamma chain hinge region DNA sequences and were used in RT-PCR for measuring different caIgG gamma chain mRNA levels in canine PBMC samples.

Immunoglobulin isotypes in sera and nasal mucosal secretions and their neonatal transfer and distribution in horses

OBJECTIVE

To determine concentrations of IgA and IgG subclasses in serum, colostrum, milk, and nasal wash samples of adult horses and foals.

ANIMALS

Seven 2-year-old Welsh ponies, 27 adult mixed-breed horses, and 5 Quarter Horse mares and their foals.

PROCEDURE

Serum was obtained from ponies and adult horses. Colostrum and milk were obtained from mares and serum and nasal wash samples from their foals immediately after parturition and on days 1, 7, 14, 28, 42, and 63. Nasal wash samples were also obtained from 23 adult horses. Concentrations of immunoglobulins were determined by use of inhibition ELISA. To determine transfer of maternal isotypes to foals, concentrations in colostrum and milk were compared with those in foal serum. Serum half-lives of isotypes in foals were also determined.

RESULTS

IgGb was the most abundant isotype in serum and colostrum from adult horses, whereas IgA was the predominant isotype in milk. The major isotype in nasal secretions of adult horses and foals > or = 28 days old was IgA, but IgGa and IgGb were the major isotypes in nasal secretions of foals < or = 14 days old. Serum half lives of IgGa, IgGb, IgG(T), and IgA in foals were 176, 32, 21, and 3.4 days, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The early immunoglobulin repertoire of neonatal foals comprised IgGa, IgG(T), and IgA; endogenous synthesis of IgGb could not be detected until 63 days after birth. The restricted repertoire of immunoglobulins in foals may influence humoral immune responses to vaccination.

An immunohistochemical study of histiocytic ulcerative colitis in boxer dogs

Histiocytic ulcerative colitis (HUC) is an inflammatory bowel disease (IBD) that occurs predominantly in dogs of the boxer breed. The lesions are characterized by mucosal ulceration and mixed inflammatory cell infiltrate that includes the presence of periodic acid-Schiff (PAS)-positive macrophages. However, the phenotype of the inflammatory cells has not been characterized further. In the present study, immunohistochemistry and computer-aided morphometric analysis were used to define populations of leucocyte subsets in the colon of 14 boxer dogs with HUC. Biopsies from six of these dogs included both lesional and non-lesional regions. Colonic tissue from 11 dogs of various breeds without evidence of gastrointestinal disease served as controls. In HUC lesions there were significantly more IgG(+), IgG3(+), IgG4(+)plasma cells, CD3(+)T cells, MHC class II(+)cells, L1(+)cells and PAS(+)cells in the lamina propria than in both control colon and non-lesional colonic regions of affected dogs. In the epithelial compartment, goblet cells were significantly decreased in HUC lesions compared to both control and non-lesional HUC colon, and intensity of enterocyte MHC class II expression was significantly increased. These observations are similar to those documented in human IBD, especially ulcerative colitis, and suggest an important role for the mucosal immune system in the pathogenesis of canine HUC.

Measurement of IgG, IgM and IgA concentrations in canine serum, saliva, tears and bile

Capture ELISAs, for canine IgG, IgM, IgA and albumin, were developed and used to analyse immunoglobulin (Ig) concentrations in both serum and secretions. Matched samples of serum, saliva and tears were taken from 31 dogs, assigned to two groups based on age, whilst bile samples were obtained from nine adult dogs at post-mortem. Serum and tear IgA concentrations were significantly lower in dogs < or = 12 months of age compared with dogs > 12 months of age (p = 0.006 and 0.045, respectively). There was no significant correlation between serum and secretory Ig levels, with the single exception of serum and tear IgM concentrations (rp = 0.553, p = 0.004). IgG and IgM concentrations were significantly correlated in matched tear and saliva samples (IgG: rp = 0.470, p = 0.023; IgM: rp = 0.651, p < 0.0001). Albumin concentrations were significantly correlated with IgG, but not IgM or IgA, in both saliva and tears (saliva, rp = 0.581, p = 0.004; tears, rp = 0.843, p < 0.0001) whilst IgA and IgM concentrations were significantly correlated with each other in both secretions (saliva, rp = 0.644, p = 0.001; tears, rp = 0.555, p = 0.009). Significantly, more Ig of all classes was secreted into saliva than tears as calculated by a secretory index. A large diurnal and day-to-day variation was observed in Ig concentrations in serial saliva and tear samples taken from a further four dogs. Serum Ig concentrations are therefore, poor indicators of mucosal secretion in this species and significant intra-individual variation exists in secretory Ig levels. Both findings should be taken into account in future studies of canine mucosal immunoglobulins.

A syndrome of anaemia, immunodeficiency and peripheral ganglionopathy in Fell pony foals

Fell pony foals developed a syndrome of anaemia, immunodeficiency and peripheral ganglionopathy. They became ill in the second or third week, and died in the second or third month of life. Clinical and pathological investigations revealed severe anaemia associated with small numbers of late erythroid precursors in bone marrow, small thymi, an absence of secondary lymphoid follicles, a lack of plasma cells and neuronal chromatolysis involving trigeminal, cranial mesenteric and dorsal root ganglia. Some of the foals had cryptosporidial enteritis and adenoviral bronchopneumonia and pancreatitis. The clinical and pathological findings were compatible with an intrinsic defect.

Allergen-specific IgG antibodies in cats with allergic skin disease

An enzyme-linked immunosorbent assay was developed for quantifying feline serum allergen-specific IgG directed against selected house dust, pollen and flea allergens. The assay was used to compare allergen-specific IgG concentrations in sera from healthy cats, cats with non-dermatologic illness, confirmed allergic cats and undiagnosed pruritic cats. Our results demonstrate that cats with confirmed allergic skin disease have significantly more IgG directed against house dust, flea and ryegrass allergens than other cat groups examined. These results support the theory that cats with allergic skin disease have an underlying TH2 lymphocyte response that directs production of both allergen-specific IgG and IgE.

Subclass profile of allergen-specific IgG antibodies in atopic dogs

Levels of allergen-specific IgE and IgE antibodies were determined in serum samples from 60 atopic and 11 normal dogs by means of commercially available ELISA test kits and a panel of 33 allergens. In the atopic population, IgE antibodies were most commonly identified with a specificity for Dermatophagoides farinae (78.3 per cent of affected dogs), D pteronyssinus (61.6 per cent), mould mix (25 per cent) and house dust (19 per cent), whereas the most frequently detected IgG antibodies had a specificity for D farinae (38.3 per cent), D pteronyssinus (33.3 per cent), mould mix (33.3 per cent), insect mix (16.6 per cent) and meadow fescue (16.6 per cent). The IgG subclass profile of allergen-specific antibodies was determined for five representative allergens from the panel. The IgG response to D farinae and D pteronyssinus was dominated by IgG4 antibodies, although lower levels of IgG2, and IgG3 and IgG1 D pteronyssinus antibodies were also detected. The IgG response to Timothy grass was predominantly within the IgG1 and IgG4 subclasses, IgG subclass selection in the response to mould mix and insect mix was broader, with relatively low level reactions from all four subclasses. The data suggest a degree of IgG subclass restriction in the humoral immune response of canine atopy which may be dependent upon the nature of the allergen.

IgG subclasses of canine anti-erythrocyte, antinuclear and anti-thyroglobulin autoantibodies

A panel of monoclonal antibodies (mAbs) reactive with the four canine IgG subclasses (IgG1, IgG2, IgG3 and IgG4) was used to investigate the activity of IgG subclasses in autoimmune responses to erythrocytes, nuclear antigens and thyroglobulin in dogs with autoimmune disease. mAbs specific for canine IgG1 and IgG4 were able to agglutinate normal dog erythrocytes coated with purified canine IgG containing each of the four subclasses. IgG1 autoantibodies were demonstrated on the surface of erythrocytes from seven dogs with Coombs'-positive autoimmune haemolytic anaemia and IgG4 autoantibodies were also present in two of these cases. Serum antinuclear antibody was shown in nine dogs to be predominantly of IgG1, IgG3 and IgG4 subclasses with only one of the dogs also producing an IgG2 antinuclear antibody. The IgG subclass profile of antinuclear antibodies differed between dogs with polyarthritis and dogs with other systemic disease. In six dogs with hypothyroidism, thyroglobulin autoantibodies of subclasses, IgG1, IgG2 and IgG4 predominated, but one dog also produced significant levels of IgG3 thyroglobulin autoantibodies. The mAbs are widely applicable to the study of the pathogenesis of canine autoimmune disease.

Tissue immunoglobulin G subclasses observed in immune-mediated dermatopathy, deep pyoderma and hypersensitivity dermatitis in dogs

A panel of monoclonal antibodies has been used to define three of the four subclasses of canine immunoglobulin G (IgG2, IgG3 and IgG4) in formalin-fixed tissues. These reagents, together with a polyclonal antiserum specific for the Fc region of canine IgG, were used in an immunohistochemical study of biopsies of skin from five normal dogs and from the lesions of canine pemphigus foliaceus in seven dogs, discoid lupus erythematosus in eight dogs, bullous pemphigoid in one dog, cutaneous drug eruption in two dogs, deep pyoderma in 13 dogs and hypersensitivity dermatitis in eight dogs. IgG autoantibody was identified in the skin of all the dogs with immune-mediated dermatoses by using the polyclonal reagent, and antibody of the IgG2 and/or IgG4 subclass was identified in the epidermis of three of the dogs with pemphigus foliaceus, two of those with discoid lupus erythematosus and in the dog with bullous pemphigoid. In all the lesions, the infiltrate of dermal plasma cells consisted of similar numbers of IgG2 and IgG4 bearing cells, with relatively few IgG3 positive cells. The total number of these cells was generally approximately the same as or greater than the number of cells labelled with the polyclonal reagent. There was no significant difference between the IgG-bearing plasma cell infiltrate in German shepherd dogs with deep pyoderma and that in dogs of other breeds. The infiltration of IgG2 and IgG4 bearing plasma cells into the skin of dogs with a range of cutaneous disorders was related to the selectively enhanced serum levels of these subclasses in the diseased dogs.

Immunophenotypic characterization of cutaneous lymphoid neoplasia in the dog and cat

Clinical, histopathological and immunohistochemical findings are presented from a series of cutaneous lymphoid neoplasms including canine epitheliotrophic lymphoma (n = 7), canine non-epitheliotrophic cutaneous lymphoma (n = 10), canine cutaneous plasmacytoma (n = 10) and feline non-epitheliotrophic cutaneous lymphoma (n = 6). Three cases of canine epitheliotrophic lymphoma expressed the CD3 T-lymphocyte marker, but the remainder were negative for this molecule and for a panel of B-cell markers. Non-epitheliotrophic cutaneous lymphoma was shown to be predominantly of T-cell phenotype (CD3+) in the dog (eight of 10 cases) and cat (five of six cases), the remaining cases in both species being of B-cell origin, expressing the gamma heavy chain of immunoglobulin (with or without lambda light chain). One canine non-epitheliotrophic B-cell lymphoma expressed IgG of the IgG2 subclass. Two of the biopsies from dogs with cutaneous plasmacotyoma were shown to express immunoglobulin alpha chain (one with lambda chain) and two neoplasms were positive for immunoglobulin gamma chain (both with lambda chain). One of the latter immunoglobulins was of the IgG4 subclass. In the majority of all cases of cutaneous lymphoid neoplasia examined, there was a local polyclonal immune response, manifested as infiltration by a mixed population of plasma cells expressing IgG (IgG2, IgG4), IgA or IgM. In the feline tumours CD3+ small T lymphocytes were included in these infiltrates.

Preparation of monoclonal antibodies specific for the subclasses of canine IgG

Canine IgG is composed of four subclasses, which are defined as IgG1, IgG2, IgG3 and IgG4 on the basis of data from fast protein liquid chromatography, and their electrophoretic mobilities and relative concentrations in serum. This paper describes the preparation of mAbs specific for determinants on canine IgG2, IgG3 and IgG4. The mAb specific for IgG2 resulted from a conventional immunisation protocol. The mAb specific for IgG3 was a result of immunisation with IgG3 combined with the suppression of the immune response to IgG1 by passively administered anti-IgG1 antibody. The mAb specific for IgG4 resulted from immunisation with Fab or Fc fragments which were obtained by the cleavage of the IgG4 molecule with papain. The specificity of each mAb was established by using an enzyme-linked immunosorbent assay which showed that all three specific clones recognised a determinant in the Fd region of the canine immunoglobulin molecule.