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  • Author or Editor: Kathleen E. Friebertshauser x
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Abstract

Objective

To develop a system for analysis of immune response variables in the lymph draining the lung and to establish baseline data for clinically normal calves.

Design

Surgery was performed on 6 calves to insert a cannula into the efferent lymphatic duct of the caudal mediastinal lymph node to create a long-term thoracic lymph fistula draining to the exterior. Lymph was collected daily, and on the fifth postoperative day, calves were exposed to an aerosol of cell culture medium (mock infection). For the next 10 days, lymph was collected for analysis and, on the tenth day, necropsy was performed.

Animals

Six 6- to 8-week-old Holstein bull calves.

Procedures

Daily lymph samples were evaluated for: flow rate; total and differential cell counts; and IgG, IgM, IgA, IgE, and protein concentrations. On days −4, −1, 1, 4, 7, and 10, cells were stained and quantitated by fluorescence-activated cell sorter analysis for T, B, CD4+, and CD8+ cells. Blood lymphocytes were evaluated on days -1 and 10 for comparison.

Results

Flow was established for up to 25 days, with a mean rate between 11 and 22 ml/h. Protein concentrations in lymph and plasma did not indicate a protein drain. Although mean lymphocyte counts reflected a slight gradual decrease in lymph lymphocytes, this effect was not apparent in every calf, nor was the effect seen in blood lymphocytes. There were no significant changes in IgG, IgM, IgA, or IgE concentration, with the exception of IgA concentration in 1 calf that developed an abscess at the cannulation site. The T-cell subset absolute numbers of CD4+ and CD8+ cells decreased slightly over time, but the CD4+-to-CD8+ cell ratio remained almost constant at near 2.

Conclusions

Creation of a thoracic lymphatic fistula appears to be a useful technique for studying effects of lung infection on immunologic variables, with potential application to bacterial and viral respiratory tract diseases.

Clinical Relevance

Thoracic lymphatic cannulation can be used in studies to determine pathogenic mechanisms in respiratory tract disease and to develop more effective vaccines against respiratory tract pathogens.

Free access
in American Journal of Veterinary Research

Abstract

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-γ 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-γ 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. (Am J Vet Res 2000;61:291–298)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To develop a model of bovine respiratory syncytial virus (BRSV) infection that induces severe disease similar to that seen in some cattle with naturally acquired BRSV infection.

Animals

25 male Holstein calves, 8 to 16 weeks old.

Procedure

17 calves were given a low-passage field isolate of BRSV by aerosolization; 8 control calves were given supernatant from noninfected cell culture. Disease was characterized by evaluating clinical signs, virus isolation and pulmonary function tests, and results of blood gas analysis, gross and histologic postmortem examination, and microbiologic testing.

Results

Cumulative incidence of cough, harsh lung sounds, adventitious sounds, and dyspnea and increases in rectal temperature and respiratory rate were significantly greater in infected calves. Three infected calves developed extreme respiratory distress and were euthanatized 7 days after inoculation. Virus was isolated from nasal swab specimens from all infected calves but not from mock infected calves. On day 7 after inoculation, mean Pao2 and Paco2 were significantly lower, and pulmonary resistance was significantly higher, in infected calves. During necropsy, infected calves had varying degrees of necrotizing and proliferative bronchiolitis and alveolitis with syncytial formation. The 3 calves euthanatized on day 7 had emphysematous bullae in the caudal lung lobes; 1 had unilateral pneumothorax.

Conclusion and Clinical Relevance

Severe disease similar to that seen in some cattle with naturally acquired BRSV infection can be induced in calves with a single aerosol exposure of a low-passage clinical isolate of BRSV. Our model will be useful for studying the pathogenesis of BRSV infection and for evaluating vaccines and therapeutics. (Am J Vet Res 1999;60:473-480)

Free access
in American Journal of Veterinary Research