Expression of inflammatory cytokine mRNA in lymphoid tissue from swine experimentally infected with Mycobacterium avium serovar 2

Murray E. Hines II Veterinary Diagnostic and Investigational Laboratory, College of Veterinary Medicine, University of Georgia, Tifton, GA 31793.

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Kendall S. Frazier Veterinary Diagnostic and Investigational Laboratory, College of Veterinary Medicine, University of Georgia, Tifton, GA 31793.

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Abstract

Objective—To evaluate in situ expression of inflammatory cytokine mRNA in lymphoid tissue of swine experimentally infected with Mycobacterium avium serovar 2.

Animals—7 noninfected pigs and 7 pigs infected with M avium serovar 2.

Procedure—Expression of mRNA of inflammatory cytokines such as tumor necrosis factor α (TNFα), interleukin (IL)-1β, IL-6, and IL-8 in formalin-fixed paraffin- embedded blocks of lymphoid tissue (lymph nodes and tonsil) of swine experimentally infected with M avium serovar 2 was compared with that of noninfected pigs. Tissues were evaluated by use of morphologic localization of cytokine mRNA, using in situ hybridization at 160 days after inoculation.

Results—A noticeable increase in mRNA expression for TNFα and mild increases in mRNA expression of IL-8 and IL-1β were detected in mandibular lymph nodes from infected swine, compared with noninfected swine. Mild increase in mRNA expression for IL-6 also was observed in tonsils from infected swine. Cytokine mRNA was detected in macrophages and lymphocytes, primarily within cortical follicles and adjacent mantle zones.

Conclusions and Clinical Relevance—Expression of mRNA for inflammatory cytokines was increased in lymphoid tissue of infected swine, possibly resulting from local factors on, or secreted by, M avium. These results suggest that alterations in cytokine mRNA expression are important in the pathogenesis and clinical course of mycobacteriosis in swine. Modulation of the immune response by vaccines that selectively target cytokine expression and secretion in response to mycobacterial challenge may be effective in prevention of mycobacteriosis in swine. (Am J Vet Res 2000;61:1487–1491)

Abstract

Objective—To evaluate in situ expression of inflammatory cytokine mRNA in lymphoid tissue of swine experimentally infected with Mycobacterium avium serovar 2.

Animals—7 noninfected pigs and 7 pigs infected with M avium serovar 2.

Procedure—Expression of mRNA of inflammatory cytokines such as tumor necrosis factor α (TNFα), interleukin (IL)-1β, IL-6, and IL-8 in formalin-fixed paraffin- embedded blocks of lymphoid tissue (lymph nodes and tonsil) of swine experimentally infected with M avium serovar 2 was compared with that of noninfected pigs. Tissues were evaluated by use of morphologic localization of cytokine mRNA, using in situ hybridization at 160 days after inoculation.

Results—A noticeable increase in mRNA expression for TNFα and mild increases in mRNA expression of IL-8 and IL-1β were detected in mandibular lymph nodes from infected swine, compared with noninfected swine. Mild increase in mRNA expression for IL-6 also was observed in tonsils from infected swine. Cytokine mRNA was detected in macrophages and lymphocytes, primarily within cortical follicles and adjacent mantle zones.

Conclusions and Clinical Relevance—Expression of mRNA for inflammatory cytokines was increased in lymphoid tissue of infected swine, possibly resulting from local factors on, or secreted by, M avium. These results suggest that alterations in cytokine mRNA expression are important in the pathogenesis and clinical course of mycobacteriosis in swine. Modulation of the immune response by vaccines that selectively target cytokine expression and secretion in response to mycobacterial challenge may be effective in prevention of mycobacteriosis in swine. (Am J Vet Res 2000;61:1487–1491)

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