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Intranasal infection with Chlamydia abortus induces dose-dependent latency and abortion in sheep.

Longbottom D, Livingstone M, Maley S, van der Zon A, Rocchi M, Wilson K, Wheelhouse N, Dagleish M, Aitchison K, Wattegedera S, Nath M, Entrican G, Buxton D - PLoS ONE (2013)

Bottom Line: Three groups of sheep (groups 1, 2 and 3) were experimentally infected with different doses of C. abortus (5×10(3), 5×10(5) and 5×10(7) inclusion forming units (IFU), respectively) prior to mating and monitored over 2 breeding cycles for clinical, microbiological, pathological, immunological and serological outcomes.Two further groups received either negative control inoculum (group 4a,b) or were inoculated subcutaneously on day 70 of gestation with 2×10(6) IFU C. abortus (group 5).Pathological, microbiological, immunological and serological analyses support the view that the maternal protective immune response is influenced by initial exposure to the bacterium.

View Article: PubMed Central - PubMed

Affiliation: Moredun Research Institute, Edinburgh, United Kingdom. david.longbottom@moredun.ac.uk

ABSTRACT

Background: Latency is a key feature of the animal pathogen Chlamydia abortus, where infection remains inapparent in the non-pregnant animal and only becomes evident during a subsequent pregnancy. Often the first sign that an animal is infected is abortion occurring late in gestation. Despite this, little is understood of the underlying mechanisms that control latency or the recrudescence of infection that occurs during subsequent pregnancy. The aim of this study was to develop an experimental model of latency by mimicking the natural route of infection through the intranasal inoculation of non-pregnant sheep with C. abortus.

Methodology/principal findings: Three groups of sheep (groups 1, 2 and 3) were experimentally infected with different doses of C. abortus (5×10(3), 5×10(5) and 5×10(7) inclusion forming units (IFU), respectively) prior to mating and monitored over 2 breeding cycles for clinical, microbiological, pathological, immunological and serological outcomes. Two further groups received either negative control inoculum (group 4a,b) or were inoculated subcutaneously on day 70 of gestation with 2×10(6) IFU C. abortus (group 5). Animals in groups 1, 2 and 5 experienced an abortion rate of 50-67%, while only one animal aborted in group 3 and none in group 4a,b. Pathological, microbiological, immunological and serological analyses support the view that the maternal protective immune response is influenced by initial exposure to the bacterium.

Conclusions/significance: The results show that intranasal administration of non-pregnant sheep with a low/medium dose of C. abortus results in a latent infection that leads in a subsequent pregnancy to infection of the placenta and abortion. In contrast a high dose stimulates protective immunity, resulting in a much lower abortion rate. This model will be useful in understanding the mechanisms of infection underlying latency and onset of disease, as well as in the development of novel therapeutics and vaccines for controlling infection.

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Related in: MedlinePlus

Histopathological changes and immunohistochemical detection of chlamydial antigen in sheep infected with C. abortus.(A) Cross-section of an affected placental membrane at 138 days gestation (dg) from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing necrosis and sloughing of the chorionic epithelium (n) and inflammation in the underlying mesenchyme (i), HE. (B) Immunohistochemical labelling of C. abortus LPS in the placenta of a control ewe (group 5; subcutaneously infected with 2×106 IFU C. abortus) at 141 dg; note intense labelling (brown colouration) of chlamydial inclusions and antigen in chorionic epithelial cells displaying signs of acute degeneration. (C) Immunohistochemical labelling of placenta sampled at 102 dg from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing an area of diffuse and granular positive labelling for C. abortus antigen associated with the destruction and loss of the chorionic epithelium. (D) Cross-section through a placentome at 138 dg from a ewe intranasally administered 5×105 IFU C. abortus (group 2), showing the interdigitating caruncular septum (s) and fetal placental villus (v). Note the light inflammation and pockets of positively labelled chlamydial antigen in the septal tissue and the proportionately greater villous labelling along with necrotic changes. (E) Section of fetal forebrain sampled at 138 days gestation from a ewe intranasally administered 5×103 IFU C. abortus (group 1) showing periventricular leucomalacia (pl), HE. (F) Section of fetal liver sampled at 136 days gestation from a ewe intranasally administered 5×105 IFU C. abortus (group 2), HE; note the focal necrosis (n) and periportal inflammation (arrow).
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pone-0057950-g002: Histopathological changes and immunohistochemical detection of chlamydial antigen in sheep infected with C. abortus.(A) Cross-section of an affected placental membrane at 138 days gestation (dg) from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing necrosis and sloughing of the chorionic epithelium (n) and inflammation in the underlying mesenchyme (i), HE. (B) Immunohistochemical labelling of C. abortus LPS in the placenta of a control ewe (group 5; subcutaneously infected with 2×106 IFU C. abortus) at 141 dg; note intense labelling (brown colouration) of chlamydial inclusions and antigen in chorionic epithelial cells displaying signs of acute degeneration. (C) Immunohistochemical labelling of placenta sampled at 102 dg from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing an area of diffuse and granular positive labelling for C. abortus antigen associated with the destruction and loss of the chorionic epithelium. (D) Cross-section through a placentome at 138 dg from a ewe intranasally administered 5×105 IFU C. abortus (group 2), showing the interdigitating caruncular septum (s) and fetal placental villus (v). Note the light inflammation and pockets of positively labelled chlamydial antigen in the septal tissue and the proportionately greater villous labelling along with necrotic changes. (E) Section of fetal forebrain sampled at 138 days gestation from a ewe intranasally administered 5×103 IFU C. abortus (group 1) showing periventricular leucomalacia (pl), HE. (F) Section of fetal liver sampled at 136 days gestation from a ewe intranasally administered 5×105 IFU C. abortus (group 2), HE; note the focal necrosis (n) and periportal inflammation (arrow).

Mentions: Placental tissues were available for examination from all but 4 ewes in the study. Lesions characteristic of C. abortus infection [7] were observed in the placental samples from groups 1, 2, 3 and 5 (Table 2). Histopathological changes consisted of suppurative placentitis with extensive disruption of the chorionic epithelium and associated aggregations of polymorphonuclear neutrophils (PMNs) along with arteritis (Figure 2A). Aborted/non-viable offspring were produced by 10 ewes in group 1 and the placentas of 7 contained lesions consistent with C. abortus infection and a further 3 had milder pathological changes (Table 2). In group 2 the placentas of 7 ewes that produced non-viable offspring had characteristic pathological changes, a further 2 had milder, less extensive changes and one was normal (placental samples were not retrieved from two ewes). In group 3, the placenta of the one ewe that aborted contained mild lesions, not necessarily specific for infection with C. abortus, whereas in group 5, all ewes that aborted had lesions characteristic of infection with C. abortus in the placenta. In all cases, when histopathological changes suggestive of C. abortus infection were observed, C. abortus DNA was detected by qPCR and organisms were also detected by mZN and by immunohistochemistry (IHC) using anti-LPS monoclonal antibody 13/5 (Figure 2B, C, D). Positive IHC labelling was observed to be in the form of intracytoplasmic inclusions in chorionic epithelial cells (Figure 2B). In placental samples with more advanced lesions, labelling was more diffuse and granular and associated with the destruction of the chorionic epithelium (Figure 2C).


Intranasal infection with Chlamydia abortus induces dose-dependent latency and abortion in sheep.

Longbottom D, Livingstone M, Maley S, van der Zon A, Rocchi M, Wilson K, Wheelhouse N, Dagleish M, Aitchison K, Wattegedera S, Nath M, Entrican G, Buxton D - PLoS ONE (2013)

Histopathological changes and immunohistochemical detection of chlamydial antigen in sheep infected with C. abortus.(A) Cross-section of an affected placental membrane at 138 days gestation (dg) from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing necrosis and sloughing of the chorionic epithelium (n) and inflammation in the underlying mesenchyme (i), HE. (B) Immunohistochemical labelling of C. abortus LPS in the placenta of a control ewe (group 5; subcutaneously infected with 2×106 IFU C. abortus) at 141 dg; note intense labelling (brown colouration) of chlamydial inclusions and antigen in chorionic epithelial cells displaying signs of acute degeneration. (C) Immunohistochemical labelling of placenta sampled at 102 dg from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing an area of diffuse and granular positive labelling for C. abortus antigen associated with the destruction and loss of the chorionic epithelium. (D) Cross-section through a placentome at 138 dg from a ewe intranasally administered 5×105 IFU C. abortus (group 2), showing the interdigitating caruncular septum (s) and fetal placental villus (v). Note the light inflammation and pockets of positively labelled chlamydial antigen in the septal tissue and the proportionately greater villous labelling along with necrotic changes. (E) Section of fetal forebrain sampled at 138 days gestation from a ewe intranasally administered 5×103 IFU C. abortus (group 1) showing periventricular leucomalacia (pl), HE. (F) Section of fetal liver sampled at 136 days gestation from a ewe intranasally administered 5×105 IFU C. abortus (group 2), HE; note the focal necrosis (n) and periportal inflammation (arrow).
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Related In: Results  -  Collection

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pone-0057950-g002: Histopathological changes and immunohistochemical detection of chlamydial antigen in sheep infected with C. abortus.(A) Cross-section of an affected placental membrane at 138 days gestation (dg) from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing necrosis and sloughing of the chorionic epithelium (n) and inflammation in the underlying mesenchyme (i), HE. (B) Immunohistochemical labelling of C. abortus LPS in the placenta of a control ewe (group 5; subcutaneously infected with 2×106 IFU C. abortus) at 141 dg; note intense labelling (brown colouration) of chlamydial inclusions and antigen in chorionic epithelial cells displaying signs of acute degeneration. (C) Immunohistochemical labelling of placenta sampled at 102 dg from a ewe intranasally administered 5×103 IFU C. abortus (group 1), showing an area of diffuse and granular positive labelling for C. abortus antigen associated with the destruction and loss of the chorionic epithelium. (D) Cross-section through a placentome at 138 dg from a ewe intranasally administered 5×105 IFU C. abortus (group 2), showing the interdigitating caruncular septum (s) and fetal placental villus (v). Note the light inflammation and pockets of positively labelled chlamydial antigen in the septal tissue and the proportionately greater villous labelling along with necrotic changes. (E) Section of fetal forebrain sampled at 138 days gestation from a ewe intranasally administered 5×103 IFU C. abortus (group 1) showing periventricular leucomalacia (pl), HE. (F) Section of fetal liver sampled at 136 days gestation from a ewe intranasally administered 5×105 IFU C. abortus (group 2), HE; note the focal necrosis (n) and periportal inflammation (arrow).
Mentions: Placental tissues were available for examination from all but 4 ewes in the study. Lesions characteristic of C. abortus infection [7] were observed in the placental samples from groups 1, 2, 3 and 5 (Table 2). Histopathological changes consisted of suppurative placentitis with extensive disruption of the chorionic epithelium and associated aggregations of polymorphonuclear neutrophils (PMNs) along with arteritis (Figure 2A). Aborted/non-viable offspring were produced by 10 ewes in group 1 and the placentas of 7 contained lesions consistent with C. abortus infection and a further 3 had milder pathological changes (Table 2). In group 2 the placentas of 7 ewes that produced non-viable offspring had characteristic pathological changes, a further 2 had milder, less extensive changes and one was normal (placental samples were not retrieved from two ewes). In group 3, the placenta of the one ewe that aborted contained mild lesions, not necessarily specific for infection with C. abortus, whereas in group 5, all ewes that aborted had lesions characteristic of infection with C. abortus in the placenta. In all cases, when histopathological changes suggestive of C. abortus infection were observed, C. abortus DNA was detected by qPCR and organisms were also detected by mZN and by immunohistochemistry (IHC) using anti-LPS monoclonal antibody 13/5 (Figure 2B, C, D). Positive IHC labelling was observed to be in the form of intracytoplasmic inclusions in chorionic epithelial cells (Figure 2B). In placental samples with more advanced lesions, labelling was more diffuse and granular and associated with the destruction of the chorionic epithelium (Figure 2C).

Bottom Line: Three groups of sheep (groups 1, 2 and 3) were experimentally infected with different doses of C. abortus (5×10(3), 5×10(5) and 5×10(7) inclusion forming units (IFU), respectively) prior to mating and monitored over 2 breeding cycles for clinical, microbiological, pathological, immunological and serological outcomes.Two further groups received either negative control inoculum (group 4a,b) or were inoculated subcutaneously on day 70 of gestation with 2×10(6) IFU C. abortus (group 5).Pathological, microbiological, immunological and serological analyses support the view that the maternal protective immune response is influenced by initial exposure to the bacterium.

View Article: PubMed Central - PubMed

Affiliation: Moredun Research Institute, Edinburgh, United Kingdom. david.longbottom@moredun.ac.uk

ABSTRACT

Background: Latency is a key feature of the animal pathogen Chlamydia abortus, where infection remains inapparent in the non-pregnant animal and only becomes evident during a subsequent pregnancy. Often the first sign that an animal is infected is abortion occurring late in gestation. Despite this, little is understood of the underlying mechanisms that control latency or the recrudescence of infection that occurs during subsequent pregnancy. The aim of this study was to develop an experimental model of latency by mimicking the natural route of infection through the intranasal inoculation of non-pregnant sheep with C. abortus.

Methodology/principal findings: Three groups of sheep (groups 1, 2 and 3) were experimentally infected with different doses of C. abortus (5×10(3), 5×10(5) and 5×10(7) inclusion forming units (IFU), respectively) prior to mating and monitored over 2 breeding cycles for clinical, microbiological, pathological, immunological and serological outcomes. Two further groups received either negative control inoculum (group 4a,b) or were inoculated subcutaneously on day 70 of gestation with 2×10(6) IFU C. abortus (group 5). Animals in groups 1, 2 and 5 experienced an abortion rate of 50-67%, while only one animal aborted in group 3 and none in group 4a,b. Pathological, microbiological, immunological and serological analyses support the view that the maternal protective immune response is influenced by initial exposure to the bacterium.

Conclusions/significance: The results show that intranasal administration of non-pregnant sheep with a low/medium dose of C. abortus results in a latent infection that leads in a subsequent pregnancy to infection of the placenta and abortion. In contrast a high dose stimulates protective immunity, resulting in a much lower abortion rate. This model will be useful in understanding the mechanisms of infection underlying latency and onset of disease, as well as in the development of novel therapeutics and vaccines for controlling infection.

Show MeSH
Related in: MedlinePlus