Genexpressionsanalysen der frühen angeborenen Immunantwort des Haushuhns induziert durch eine Infektion mit Salmonella enteritidis mit Hilfe der Microarray Technologie

Salmonella infections in humans arise through chicken-based food
such as eggs, egg-products, or chicken meat. The most common cause
for these infections is Salmonella enteritidis, and the aim of this
study has been to analyze the early innate immune response of
chickens induced via this pathogen. Note that S. enteritidis is a
host-adapted serovar, which only causes clinical findings in young
chickens during their first week of life; adult chickens do not get
sick, but may nevertheless act as inapparent infected carriers. We
studied the reaction from the chicken immune system on S.
enteritidis, using macrophage cultures as well as tissue samples of
infected adult chickens. The gene expression studies were carried
out by an “Agilent 4x44K chicken microarray” method. In our in
vitro studies, we infected primary macrophages with S. enteritidis
for 4 hours, using a MOI of 10. The gene expression studies
resulted in the inductions of interleukins (IL1β, IL6, IL12p40,
IL18), of chemokines (CCL1, CCL4 (K203), CCL20, CXCL8 (IL8),
CXCL13), of some members of the tumor-nekrose-factor-superfamily
(TNFSF), and of some toll-like receptors (TLR). Hence the cells
have an inflammatory reaction. Particularly prominent were the
expression changes of K60 (IL8 homolog), K203 (chCCLi2, MIP-1β),
CCL20, and TL1a (TNFSF15). Finally, infected macrophages expressed
a group of typical Th1-cytokines, including IL12p40, IL18, and
IFN-γ. In further analysis of our data, we focused on cytokines,
chemokines, and members of the TNF-superfamily. In the ceca we
found similar expression patterns within these three groups as was
previously found for them in the macrophages study. In our in vivo
studies, we infected chickens that were 8 weeks old and already had
a well developed immune system. They were infected in the crop
using a dose of 107 salmonella. At 5, 12, 24, and 48 hours of
infection, we sampled the ceca and cecal tonsils for the bacterial,
histological, and gene expression analyses. Already at 5 hours
p.i., we were (for all but one animal) able to isolate bacteria
from the ceca-tissue. The bacterial load reached its maximum at 12
hours p.i.. The infection of the cecal-tissues was confirmed in the
histology, both by the detection of bacteria and by the occurrence
of inflammatory cells. However, using histology, we could not
detect any bacteria in cecal tonsils, which suggests that no
infection was present in these organs. This suggestion was
confirmed in gene expression analyses. When comparing the gene
expression studies of cecal tonsils and ceca, the former showed
lower counts of differential regulated genes (Tab. 11). Both their
count maxima occurred at 12 hour p.i though. Moreover, at this time
41 significant regulated pathways had been identified.. In summary,
the in vitro and the in vivo experiment both resulted in an initial
inflammatory reaction, as well as in a typical Th1-cytokines
reaction. To investigate functional characterisation of named
candidate genes, in the first instance CCL20, CXCL8, K60, K203, and
TL1a, future analyses of the innate immune response should involve
them. This may contribute to a better understanding of the
successful defense mechanisms against S. enteritidis in chicken,
which may help to contain the amount of salmonellosis in humans.