Cytotoxic T-cell, delayed type hypersensitive and listeriolysin O responses in experimental bovine listeriosis

Five different antigens of Listeria monocytogenes NCTC 11994 were assayed f or their lymphoproliferative, cytotoxic, humoral and delayed type hypersens itivity (DTH) responses in experimentally infected calves. The antigens use d were culture filtrate antigen (CFA), listeriolysin O (LLO), sonicated ant igen (SA), live antigen (LA) and heat killed antigen (HKA). CFA was most ly mphoproliferative when assayed in vitro. In an autologous monocyte cytotoxi city assay, soluble protein as well as bacterial cells elicited cytolytic r esponses, however, LA and LLO primed monocytes showed a higher cytotoxic ef fect. The expression of cell surface markers of lymphocyte subpopulations w as almost identical in experimentally infected as well as non-infected calv es. SA elicited the highest humoral and DTH responses. LLO being a major vi rulence factor with appreciable humoral as well as cellular responses may b e used as a candidate antigen to develop a reliable diagnostic immunoassay. (C) 1999 Elsevier Science B.V. All rights reserved.