Comparative immunopathophysiological responses in mice following different route of inoculation of Brucella melitensis and its lipopolysaccharide
Brucella melitensis, which causes a small ruminant brucellosis in sheep and goats and Malta fever in humans, is believed to enter the host via ingestion, inhalation or direct contact of the organism with broken skin or mucous membranes. Among the consequences of the different routes of infection...
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Online Access: | http://ethesis.upm.edu.my/id/eprint/12714/1/FPV%202016%2025%20T.pdf |
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| Summary: | Brucella melitensis, which causes a small ruminant brucellosis in sheep and goats
and Malta fever in humans, is believed to enter the host via ingestion, inhalation or
direct contact of the organism with broken skin or mucous membranes. Among the
consequences of the different routes of infection are septicaemia, increased
permeability of blood vessels and presence of the organism in several organs.
However, the oral and the respiratory tract may not be the only portal of entry and
route of spread of B. melitensis. Circumstantial evidence had suggested the
involvement of gastrointestinal, respiratory and reproductive tract in the
pathogenesis of B. melitensis and its lipopolysaccharide in ruminants. Nevertheless,
the pathogenesis and the immunopathophysiology of the disease following different
route of infection have not been well documented since previous reports on the
disease were limited to incidental observations. The response of gastrointestinal,
respiratory, and reproductive tract following oral, intranasal, subcutaneous and
intraperitoneal exposure to B. melitensis was studied and compared its severity with
lipopolysaccharide (LPS) exposure. The cytokine, antibody pattern and sex related
hormonal responses following the different route of inoculations to B. melitensis and
its lipopolysaccharide in mice were also investigated.
The clinical signs observed in these studies include; inappetence, ocular discharge,
and ruffled following the different route of exposure to B. melitensis and its
lipopolysaccharide. Although the severity of the clinical sign varied over time, type
of inoculum and route of inoculation, however, mean clinical score were
significantly higher in oral and intraperitoneal exposed groups to B. melitensis
followed by intranasal and subcutaneous groups, respectively. Clinical observations
for intranasal and subcutaneous groups were limited mostly to mild and moderate
involvement. In contrast to B. melitensis infected group, animals challenged with
LPS showed mild clinical signs which seemed to be limited in the first 48 h post nfection. Thereafter, normalization was observed in this group as they were not
significantly different from those served as a control group. No significant
differences were detected among the different sub groups of LPS infected indicating
that the clinical presentation did not differ by route of exposure. Animals in control
group did not develop any clinical signs throughout the experimental period.
The pathological alterations varied depending on the route of infection, days postinfection
and the type of the organs recorded. Spleen, liver, kidney, lung and the
reproductive organs that include uterus, ovary, testes, epididymis and seminal
vesicle were the most commonly and severely affected organs with predominance in
oral and intraperitoneally infected animals of B. melitensis group. These organs
presented marked infiltration of inflammatory cells, degeneration, necrosis,
haemorrhage and oedema. In intranasal and oral group of B. melitensis, lungs were
the most affected organ than the other route of infection, with an abundance of fibrin
admixed with cellular debris. Emphysema, oedema and marked infiltration of
inflammatory cells were also recorded in lungs from 24 hours post-infection until the
end point of the experiment. In contrast, histopathological changes of the various
organs infected with LPS were almost similar presenting mild degrees of lesion
involvement in all routes of infection with special reference in lungs and
reticuloendothelial organs. Thus, indicating that LPS have preventive properties
toward establishment of pathological lesions. Following the different routes of
exposure, B. melitensis was isolated from the vital and reproductive organs along
with intestinal segments of the mice that developed severe lesions scoring. Higher
isolation and detection by PCR was noted predominantly in both reproductive tract
and reticuloendothelial-rich organs of oral and intraperitoneal expose groups
followed by intranasal and subcutaneous groups to B. melitensis, respectively.
Concurrently the cytokine and antibody immune response of mice following
different routes of inoculation to B. melitensis and its lipopolysaccharide was also
evaluated. Both B. melitensis and LPS elicited sustained and significantly higher
serum Il-1β and IL-6 that has of minor relevance to the route of infection. However,
the highest responses were noted in LPS group than B. melitensis infected group
within the respective route of inoculation. Similarly, the LPS elicited sustained and
significantly higher IgM and IgG levels than B. melitensis in all different routes of
infection. Among the routes of infection, the subcutaneous group yielded highest
titters of antibody response followed by intranasal and intraperitoneal groups,
respectively. With the presence of severe histopathological evidence along with
higher isolation of B. melitensis infected group in the reproductive tract, the
experiment was conducted to evaluate the serum hormonal changes following
different route of exposure to B. melitensis and its lipopolysaccharide. Both B.
melitensis and LPS resulted in significant decrease in the circulating concentrations
of serum progesterone, estradiol, and testosterone levels that has significant (p<0.05)
difference when the effect is compared to those served as a control group.
This study showed that B. melitensis organisms were present in various segments
and tissues of the gastrointestinal, respiratory, and reproductive tract following the
different route of exposure. Therefore, it can be concluded that B. melitensis infection can be transmitted via the gastrointestinal, respiratory and reproductive
tract. Oral, intranasal and subcutaneous routes of administration of LPS elicited high
serum cytokine and antibody immune response than B. melitensis infected group,
although the responses of cytokines were variable. Thus, oral, intranasal and
subcutaneous infections with 109 of live B. melitensis and its lipopolysaccharide
were safer than the intraperitoneal route of inoculation. Both of these routes, in
particular subcutaneous route, can be considered as potential alternative route for
vaccine administration against B. melitensis infection in small ruminants. Similarly,
it was concluded that the LPS stimulated significantly the innate and acquired
immune system without significant systemic dysfunction, suggesting potentiality of
the protective properties of this component as alternative vaccine for brucellosis
infection. |
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