The time course of the specific antibody response by various ELISAs in pigs experimentally infected with Toxoplasma gondii

Peter Lind, J. Haugegaard, Anne Wingstrand, Svend Aage Henriksen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    With the aim of developing routine serological tests for monitoring the Toxoplasma infection status of Danish swine herds, four ELISAs based on tachyzoite antigen were set up: (1) an indirect ELISA for IgG-antibody; (2) a blocking ELISA for antibody to the membrane antigen, P-30; (3) an indirect ELISA for IgM; (4) a reverse, antibody-catching IgM-ELISA. Groups of pigs (number between 6 and 10) were inoculated with tachyzoites of the RH-strain, tissue cysts of two complete strains, or oocysts in two doses (10(3) and 10(4)). All inoculations were tolerated well. Irrespective of strain and stage used for inoculation, specific IgG and anti-P-30 blocking activity appeared after 1-2 weeks, with OD-values stabilizing after 3-6 weeks and persisting throughout the study period (3-4 months). Specific IgM appeared quickly, but was short-lived (approximately weeks). A cut-off OD-value of 0.36 for positive seroreaction in the indirect IgG-ELISA was determined on the basis of 69 sera from four herds, investigated in the dye-test (serum dilution 1:10) and ELISA. The chosen cut-off gave optimal combined sensitivity and specificity of 0.94 and 0.92, respectively, using the dye-test as a standard. Corresponding figures for the blocking ELISA were 37% inhibition as cut-off, with sensitivity and specificity of 0.94 and 0.94, respectively. Sera from a total of 87 pigs, experimentally infected with bacteria of the genera Salmonella, Yersinia or Actinobacillus and with the parasites Isospora suis, Trichinella spiralis or Ascaris suum. in no case produced cross-reactions in the IgG-ELISA. However, 3/9 pigs inoculated with 50000 sporocysts of Sarcocystis miescheriana gave maximal OD-readings of 0.40-0.45 during the 13-15 weeks observation period. None of the sera from heterologously infected animals produced inhibitions in the anti-P-30 blocking ELISA exceeding 36%.
    Original languageEnglish
    JournalVeterinary Parasitology
    Volume71
    Issue number1
    Pages (from-to)1-15
    ISSN0304-4017
    DOIs
    Publication statusPublished - 1997

    Keywords

    • immune response-protozoa
    • Toxoplasma gondii
    • ELISA
    • protozoa

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