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

Roberto M.C. Guedes, Connie J. Gebhart

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124 Scopus citations

Abstract

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 4.4×109 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.

Original languageEnglish (US)
Pages (from-to)135-145
Number of pages11
JournalVeterinary Microbiology
Volume91
Issue number2-3
DOIs
StatePublished - Feb 2 2003

Bibliographical note

Funding Information:
R.M.C. Guedes was supported by the Brazilian government sponsoring agency “Conselho Nacional de Desenvolvimento Cientifico e Tecnologico” (CNPq), and Universidade Federal de Minas Gerais. This study was supported by grants from the National Pork Board and Boehringer Ingelheim Vetmedica. We thank Dr. Federico Zuckermann and Debra Swanson for technical assistance, Dr. Maria Isabel M. Coelho-Guedes and Keith Kinsley for help with handling the animals, and Dr. John Deen for critical review of the manuscript.

Keywords

  • Immune response
  • Lawsonia intracellularis
  • Pig-bacteria
  • Vaccine

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