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Evaluation of serovar‐independent ELISA antigens of A ctinobacillus pleuropneumoniae in pigs following vaccination or experimental challenge with respiratory pathogens and natural A . pleuropneumoniae serovar 1 challenge
Author(s) -
Eamens GJ,
Gonsalves JR,
Whittington AM,
Turner B
Publication year - 2012
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.2012.01008.x
Subject(s) - antigen , actinobacillus pleuropneumoniae , pasteurella multocida , serotype , vaccination , serology , biology , microbiology and biotechnology , recombinant dna , virology , cross reactivity , antibody , immunology , bacteria , gene , cross reactions , biochemistry , genetics
Objective To compare the sensitivity and cross‐reactivity of six serological enzyme‐linked immunosorbent assays ( ELISA s) based on serovar‐independent antigens of A ctinobacillus pleuropneumoniae ( A pp). Design An experimental pig trial using direct or natural challenge with A pp and direct challenge or vaccination using other common respiratory pathogens. Procedure A 39‐ kDa outer membrane protein antigen and five recombinant antigens from the ApxIVA gene of A pp were evaluated. The latter were derived from the ApxIVA N terminus ( ApxIVA ‐ N , ApxIVA ‐ NP , ApxIVA ‐ NPS ) or C terminus ( ApxIVA ‐ C , ApxIVA ‐ CP ). Pigs were sampled after direct challenge with A pp, P asteurella multocida or H aemophilus parasuis , after vaccination with these organisms and after natural A pp infection. Clinical and necropsy findings were evaluated. Results The 39‐ kDa ELISA had high sensitivity, but cross‐reactivity, following P . multocida challenge. ELISA s using ApxIVA N terminus antigens were clearly more sensitive than C terminus antigens for detection of A pp‐induced disease. Although affinity‐purified ApxIVA ‐ NP antigen detected marginally more diseased pigs than the ‐ N and ‐ NPS ELISA s, these assays only detected 41–47% of 17 pigs with lung lesions and microbiological evidence of A pp based on sampling up to 4–5 weeks after natural (13 pigs) or 5 weeks after direct A pp serovar 1 challenge (4 pigs). Conclusions The 39‐ kDa ELISA readily detects A pp exposure and infection, but is adversely affected by P . multocida infection. ApxIVA ‐ N ‐based ELISA s can be used to evaluate the A pp status of commercial herds, but a proportion of infected and diseased animals are seronegative at 1 month after likely exposure to aerosol transmission of A pp from clinical cases.