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Summary

The effect of dietary copper deficiency on T-cell mitogenic responsiveness and phenotypic profile of blood mononuclear cells (mnc) in weaned pigs was examined. Outbred, weaned pigs were fed a semipurified diet containing adequate (6.4 mg/kg of body weight) or deficient (0.8 mg/kg) amounts of Cu. Pigs fed the low Cu diet for 10 weeks had markedly decreased concentrations of Cu in liver and plasma, and hypertrophic hearts. In vitro reactivity of mnc from Cu-deflcient pigs to phytohemagglutinin and concanavalin A was significantly suppressed. This functional impairment was not associated with a decrease in the percentages of T cells, CD4 or CD8 cell subsets, or B cells. Expression of sla-dq and sla-dr class II major histocompatibility complex (mhc) antigens was increased by Cu deficiency, the former significantly. Unlike rodents, in which inadequate Cu nutriture induces functional T cell deficiency that is associated with a decrease in the CD4 T-cell subset, swine fed inadequate Cu diets for 10 weeks had no changes in mhc subsets yet clearly manifested functional impairment of T-cell responses.

Free access
in American Journal of Veterinary Research

Summary

Cell-mediated immunity was evaluated in intestinal, respiratory, and systemic lymphoid tissues of pigs exposed when 11 days old to virulent transmissible gastroenteritis virus (tgev), attenuated tgev, or porcine respiratory coronavirus (prcv), 3 antigenically related porcine coronaviruses with distinct enteric and respiratory tissue tropisms. Mononuclear cells were prepared from mesenteric lymph nodes (mln), bronchial lymph nodes (bln), and spleens of pigs and tested for virus-specific responses by use of lymphocyte proliferation assays. Vigorous mln and bln proliferation responses to virulent tgev and prcv, respectively, at postinoculation days 8 to 24 were strongly associated with prior detection of tgev in rectal swab samples and prcv in nasal swab samples. Gastrointestinal disease and intestinal virus replication, assessed on the basis of rectal virus shedding, were almost exclusively found in the virulent tgev-inoculated pigs, even though virulent tgev and a high dose of attenuated tgev elicited the highest proliferation responses in mln. Pigs exposed to prcv or attenuated tgev did not have clinical signs of disease, and only 1 pig given a high dose of attenuated tgev shed virus in feces. Porcine respiratory coronavirus replicated in the respiratory tract after either oronasal or aerosol inoculation of virus and induced strong bln, but not mln, proliferation responses. A high dose of attenuated tgev (4 × 108 plaque-forming units) was more effective than a lower dose of attenuated tgev (7 × 106 plaque-forming units) in eliciting significant lymphocyte proliferation in mln and bln. Cellular immune function, assessed on the basis of mitogen-induced proliferation of lymphocytes, was comparable for all 3 sources of lymphocytes and was not adversely affected by exposure to any of the 3 coronaviruses, nor did it vary with age of the pigs. The tissue tropism of tgev and prcv was associated with induction of virus-specific cell-mediated immune responses, as evidenced by substantial lymphocyte proliferation responses in mln and bln, mucosa-associated lymph nodes adjacent to the primary sites of virus replication. The failure of prcv strain ISU-1 to replicate in the intestinal tract correlated with poor virus-specific cellular immune responses in mln.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To follow antibody responses measured by various serologic tests in pigs orally inoculated with low (≤ 10 oocysts) numbers of Toxoplasma gondii oocysts.

Animals

24, 2- to 3-month-old pigs.

Procedure

Pigs (n = 42) were inoculated orally with 10 (14 pigs) or 1 (28 pigs) infective oocysts, and 6 pigs served as uninoculated controls. Blood (serum) samples were obtained at 1- to 3-week intervals until euthanasia. At necropsy, the brain, heart, and tongue of pigs were bioassayed in mice and cats for isolation of T gondii. Modified agglutination test (MAT), using whole, fixed tachyzoites and mercaptoethanol; latex agglutination test (LAT); indirect hemagglutination test (IHAT); Sabin-Feldman dye test (DT); and ELISA were used to evaluate serologic responses to T gondii.

Results

T gondii was isolated from tissues of 13 of 14 pigs each fed 10 oocysts, 17 of 28 pigs each fed 1 oocyst, and 0 of 6 control pigs. 29 of 30 T gondii-infected pigs developed antibodies when measured by MAT, DT, and ELISA; the 1 seronegative-infected pig had been fed 10 oocysts and was euthanatized 69 days after inoculation. LAT detected antibodies in 26 of 30 T gondii-infected pigs. IHAT detected antibodies in 11 T gondii-infected pigs.

Conclusion

MAT, DT, and ELISA were more sensitive serologic assays than LAT and IHAT for detecting antibodies induced by low numbers of T gondii in pigs. (Am J Vet Res 1996;57:1733–1737)

Free access
in American Journal of Veterinary Research