Investigation of antigen-specific T-cell responses and subcutaneous granuloma development during experimental sensitization of calves with Mycobacterium avium subsp paratuberculosis.
OBJECTIVE
To characterize the early cellular immune response to Mycobacterium avium subsp paratuberculosis (MAP) infection and evaluate the development of granulomatous inflammation at the SC injection site in experimentally inoculated calves.


METHODS
Forty-eight 4-week-old calves.


METHODS
Calves received an SC injection of MAP strain 19698 (n = 25), sterile saline (0.9% NaCl) solution (20), or a commercial paratuberculosis vaccine (3); the inoculation site tissue and associated draining lymph node were excised at postinoculation day (PID) 0 (n = 36), 7 (14), 14 (6), 21 (8), and 60 (32). Sections of inoculation site tissues were evaluated immunohistochemically for T-cell subsets; lymph node mononuclear cells (LNMCs) were assessed for T-cell surface markers and for intracellular interferon-gamma via flow cytometry.


RESULTS
At MAP inoculation sites, calves developed mild, focal granulomatous inflammation by PID 7; by PID 60, areas of inflammation contained macrophages with numerous lymphocytes. Compared with control calves, there was increased antigen-specific LNMC proliferation in MAP- and vaccine-inoculated calves at PID 60, although proliferation among lymphocyte subsets was not significantly different between MAP-inoculated and control calves; in vaccine-inoculated calves, CD4+ T-cells predominated. In MAP-inoculated and control calves, antigen-specific interferon-gamma production by LNMCs did not differ significantly; vaccine-inoculated calves had marked interferon-gamma expression by CD4+ T-cells.


CONCLUSIONS
In calves, SC administration of MAP resulted in granulomatous inflammation at inoculation sites and an antigen-specific T-cell proliferative response. Results suggest that this experimental system can be used to reproducibly generate antigen-specific T-cells during MAP infection for functional analysis.
Simutis
Frank J
FJ
Department of Veterinary Pathology, College of Veterinary Medicine, Iowa State University, Ames, IA 50010, USA.
Cheville
Norman F
NF
Jones
Douglas E
DE
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology* / Q000382:microbiology* / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005434:Flow Cytometry / Q000662:veterinary; D006099:Granuloma / Q000473:pathology*; D007111:Immunity, Cellular / Q000276:immunology*; D007150:Immunohistochemistry / Q000662:veterinary; D007371:Interferon-gamma / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000473:pathology; D008198:Lymph Nodes / Q000166:cytology / Q000473:pathology; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology*; D010283:Paratuberculosis / Q000276:immunology* / Q000473:pathology
D007371:Interferon-gamma