Immunisation regimes used to elevate serum IgE in sheep

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.

Bovine respiratory syncytial virus-specific IgE is associated with interleukin-2 and -4, and interferon-gamma expression in pulmonary lymph of experimentally infected calves

OBJECTIVE

To study the local immune response of calves to bovine respiratory syncytial virus (BRSV) infection with emphasis on IgE production and cytokine gene expression in pulmonary lymph.

ANIMALS

Twelve 6- to 8-week-old Holstein bull calves. Six similar control calves were mock infected to obtain control data.

PROCEDURE

Lymphatic cannulation surgery was performed on 12 calves to create a long-term thoracic lymph fistula draining to the exterior. Cannulated calves were exposed to virulent BRSV by aerosol. Lymph fluid collected daily was assayed for BRSV and isotype-specific IgE antibody, total IgG, IgA, IgM, and protein concentrations. Interleukin-4 (IL-4), interleukin-2 (IL-2), and interferon-gamma were semi-quantitated by reverse transcription-polymerase chain reaction (RT-PCR). Cell counts and fluorescence-activated cell scanner (FACSCAN) analysis of T-cell subsets were performed on lymph cells.

RESULTS

Calves had clinical signs of respiratory tract disease during days 5 to 10 after infection and shed virus. Bovine respiratory syncytial virus-specific IgE in infected calves was significantly increased over baseline on day 9 after infection. Mean virus-specific IgE concentrations strongly correlated with increases in severity of clinical disease (r = 0.903). Expression of IL-2, IL-4, and interferon-gamma was variably present in infected and control calves, with IL-4 expression most consistent during early infection.

CONCLUSIONS AND CLINICAL RELEVANCE

Infection with BRSV was associated with production of BRSV-specific IgE, and IL-4 message was commonly found in lymph cells of infected calves. This finding supports the concept that BRSV-induced pathophysiology involves a T helper cell type-2 response. Effective therapeutic and prophylactic strategies could, therefore, be developed using immunomodulation to shift the immune response more toward a T helper cell type-1 response.

Protection in lambs vaccinated with Haemonchus contortus antigens is age related, and correlates with IgE rather than IgG1 antibody

Protection by vaccination with excretory-secretory products (ES) from Haemonchus contortus, containing predominantly proteins of 15 and 24 kDa, against an experimental challenge infection depends on the age of the sheep. Vaccinated sheep 9, 6 or 3 months of age were protected for 83%, 77% and -34%, respectively. There was a significant difference in ES-specific serum IgE response but not in IgG1 response, after the last vaccination between the different age groups. In the protected 9-month-old animals, there was an increase up to 18 times the prevaccination levels, while the increase in the unprotected 3-month-old animals was at most 1.4 times. The 6-month-old animals showed an intermediate increase of approximately six times the prevaccination level. There was no correlation within the 9-month-old sheep between ES-specific IgE levels and protection, measured as worm burden. However, when the different age groups were combined, there was a positive correlation (r = 0.38) between protection and ES-specific IgE levels 1 week after the vaccination. 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. Increased serum IgE levels, eosinophilia and mucosal mast cell hyperplasia are the hallmarks of a Th2 response and were all demonstrated in protected, older sheep, but not in unprotected, younger sheep.

Vaccination against the gastrointestinal nematode, Haemonchus contortus, using a purified larval surface antigen

Sheep were immunized with a purified antigen (Hc-sL3) expressed on the surface of L3 larvae of the gastro-intestinal parasite, Haemonchus contortus, using different adjuvant and immunization routes. In the first experiment, intradermal immunization of sheep with Hc-sL3 and QuilA did not result in reductions in faecal egg counts after subsequent challenge infection while significant reductions were obtained when aluminium hydroxide (AH) was used as the adjuvant. Significant protection with Hc-sL3 absorbed on AH was confirmed in a second experiment and this protection was maintained when dextran sulphate was added to the Hc-sL3/AH mixture while the addition of pertussis toxin abrogated the protective effect. Significant levels of protection, as determined by reductions in both faecal egg counts and worm burdens, were also obtained when the Hc-sL3/AH mixture was injected into the rectal mucosa or the Hc-sL3 antigen was deposited on the surface of the rectal mucosa with cholera toxin. No correlations with antibody levels or isotype and protection were observed.