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.
Animals—Forty-eight 4-week-old calves.
Procedure—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-γ via
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, antigenspecific
interferon-γ production by LNMCs did not differ
significantly; vaccine-inoculated calves had
marked interferon-γ expression by CD4+ T-cells.
Conclusions and Clinical Relevance—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. (Am J Vet Res 2005;66:474–482)
Objective—To develop a method for inducing acute
leptospirosis in dogs.
Animals—31 nine-week-old female Beagles.
Procedure—Beagles were randomly assigned to 2
inoculation groups or a control group. Dogs were
inoculated on 3 successive days by conjunctival instillation
of 5 X 107 cells of Leptospira kirschneri serovar
grippotyphosa strain 82 (12 dogs) or strain RM 52 (14
dogs). Control dogs (n = 5) were similarly inoculated
with sterile leptospiral culture media. Clinical signs,
clinicopathologic variables, anti-leptospiral antibody
titers, and evidence of leptospires in tissues and body
fluids were evaluated. Dogs were euthanatized and
necropsied on days 7, 14, 22, or 28 after inoculation or
as required because of severe illness.
Results—Clinical signs in infected dogs included conjunctivitis,
lethargy, diarrhea, dehydration, vomiting,
and icterus. Consistent clinicopathologic alterations
included azotemia, hyperphosphatemia, increased
anion gap, hyperbilirubinemia, and an increase in alkaline
phosphatase activity. Leptospires were cultured
from the kidneys (11/12), urine (6/9), aqueous humor
(9/12), blood (12/12), and liver (12/12) of dogs inoculated
with strain 82. Only 3 of 14 dogs became infected
after inoculation with strain RM 52.
Histopathologic lesions in infected dogs included
interstitial nephritis, renal tubular degeneration and
necrosis, pulmonary hemorrhage, and hepatic edema
Conclusions and Clinical Relevance—Conjunctival
exposure to L kirschneri serovar grippotyphosa strain
82 resulted in acute leptospirosis in all inoculated
dogs, but only 3 of 14 dogs inoculated with strain RM
52 became infected. This method of infection by
serovar grippotyphosa can be used to study the
pathogenesis and prevention of leptospirosis in dogs.
(Am J Vet Res 2004;65:1100–1107)