Onset and duration of fecal shedding, cell-mediated and humoral immune responses in pigs after challenge with a pathogenic isolate or attenuated vaccine strain of Lawsonia intracellularis

• Published in: Veterinary microbiology Vol. 91; no. 2; pp. 135 - 145
• Main Authors: Guedes, Roberto M.C, Gebhart, Connie J
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02-02-2003; Elsevier Science
• Subjects: Animals; Antibodies, Bacterial - blood; Bacterial Vaccines - immunology; Bacteriology; Biogenesis of cell structures, supramolecular organization; Biological and medical sciences; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Enzyme-Linked Immunosorbent Assay - veterinary; Feces - microbiology; Fundamental and applied biological sciences. Psychology; Gram-Negative Bacterial Infections - blood; Gram-Negative Bacterial Infections - immunology; Gram-Negative Bacterial Infections - microbiology; Gram-Negative Bacterial Infections - veterinary; Immune response; Immunoenzyme Techniques - veterinary; Interferon-gamma - metabolism; Intestinal Diseases - immunology; Intestinal Diseases - microbiology; Intestinal Diseases - veterinary; Lawsonia Bacteria - genetics; Lawsonia Bacteria - immunology; Lawsonia intracellularis; Microbiology; Miscellaneous; Pig–bacteria; Polymerase Chain Reaction - veterinary; Random Allocation; Swine; Swine Diseases - immunology; Swine Diseases - microbiology; Vaccine; Vaccines, Attenuated - immunology; Pig–bacteria; Vaccine; Immune response; Lawsonia intracellularis; Pig-bacteria; Antibody; Vaccine strain; Swine proliferative enteropathy; Infection; Pathogenic; Bacteriosis; Bacteria; Isolate; Feces; Veterinary; Attenuated strain; Humoral immunity
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/S0378-1135(02)00301-2

Little is known about the humoral and, especially, cell-mediated immune response in pigs exposed to
Lawsonia intracellularis. The objectives of this study were to investigate the onset and duration of fecal shedding, cell-mediated and humoral immune responses in pigs after challenge with a pathogenic isolate or a commercial live vaccine strain of
L. intracellularis. Twenty-four 5-week-old pigs were exposed to 4.4×10
9 organisms of a pathogenic
L. intracellularis isolate PHE/MN1-00 (10 pigs), a
L. intracellularis live attenuated vaccine strain (10 pigs) or sham inoculum (4 pigs). Fecal, serum and whole blood samples were collected from all animals before exposure and weekly up to 13 weeks post inoculation and tested by PCR, immunoperoxidase monolayer assay serology and an interferon-gamma assay, respectively. One animal from each group was euthanized on day 22 post exposure to confirm infection. Humoral and cell-mediated immune responses were initially detected 2 weeks after exposure in pigs challenged with the pathogenic isolate, and 5 and 4 weeks, respectively, in pigs exposed to the modified-live vaccine group. Humoral and cell-mediated immune responses were still detected in some pigs from both
L. intracellularis exposed groups 13 weeks after exposure. Fecal shedding was initially detected 1 week and lasted, intermittently, 12 weeks post exposure in pigs challenged with the pathogenic isolate, while fecal shedding was first detected 2 weeks and lasted, also intermittently, 9 weeks after exposure to the vaccine. In summary, both pathogenic isolate challenged and vaccine exposed pigs demonstrated long-term shedding of and immune responses to
L. intracellularis.