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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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IFN-γ production from PBMC restimulated with UV-killed C. abortus antigen in vitro.PBMC was prepared from whole blood from ewes, restimulated in vitro with UV-killed C. abortus antigen and culture supernatants harvested for analysis using the BOVIGAM™ commercial ELISA to determine the concentration (in pg/ml) of IFN-γ produced (see Materials and Methods). The data are log10 transformed means (± SEM) of normalised responses for each group following intranasal inoculation with 5×103 (Group 1 -▪-), 5×105 (Group 2 -▴-) or 5×107 (Group 3 -♦-) IFU C. abortus or negative control inoculum (Group 4a -+-) prior to pregnancy; or subcutaneous injection with 2×106 IFU C. abortus at 70 days of gestation (Group 5 -•-).
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pone-0057950-g004: IFN-γ production from PBMC restimulated with UV-killed C. abortus antigen in vitro.PBMC was prepared from whole blood from ewes, restimulated in vitro with UV-killed C. abortus antigen and culture supernatants harvested for analysis using the BOVIGAM™ commercial ELISA to determine the concentration (in pg/ml) of IFN-γ produced (see Materials and Methods). The data are log10 transformed means (± SEM) of normalised responses for each group following intranasal inoculation with 5×103 (Group 1 -▪-), 5×105 (Group 2 -▴-) or 5×107 (Group 3 -♦-) IFU C. abortus or negative control inoculum (Group 4a -+-) prior to pregnancy; or subcutaneous injection with 2×106 IFU C. abortus at 70 days of gestation (Group 5 -•-).

Mentions: Blood samples were taken from the ewes for IFN-γ analysis prior to inoculation and then at specific time points during the course of the first lambing season (at 6 and 17 weeks post inoculation (wpi), at the start of lambing/abortion (22 wpi) and 7 weeks following the lambing/abortion period (36 wpi) (Figure 4). Overall statistical analysis of data from groups 1, 2 and 3 showed no evidence of an effect of ‘group’ or ‘lambing status’ on the mean IFN-γ levels produced by PBMC stimulated with C. abortus antigen, indicating that the difference in mean IFN-γ production between animals that aborted or lambed normally was statistically non-significant, irrespective of the group.


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)

IFN-γ production from PBMC restimulated with UV-killed C. abortus antigen in vitro.PBMC was prepared from whole blood from ewes, restimulated in vitro with UV-killed C. abortus antigen and culture supernatants harvested for analysis using the BOVIGAM™ commercial ELISA to determine the concentration (in pg/ml) of IFN-γ produced (see Materials and Methods). The data are log10 transformed means (± SEM) of normalised responses for each group following intranasal inoculation with 5×103 (Group 1 -▪-), 5×105 (Group 2 -▴-) or 5×107 (Group 3 -♦-) IFU C. abortus or negative control inoculum (Group 4a -+-) prior to pregnancy; or subcutaneous injection with 2×106 IFU C. abortus at 70 days of gestation (Group 5 -•-).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585262&req=5

pone-0057950-g004: IFN-γ production from PBMC restimulated with UV-killed C. abortus antigen in vitro.PBMC was prepared from whole blood from ewes, restimulated in vitro with UV-killed C. abortus antigen and culture supernatants harvested for analysis using the BOVIGAM™ commercial ELISA to determine the concentration (in pg/ml) of IFN-γ produced (see Materials and Methods). The data are log10 transformed means (± SEM) of normalised responses for each group following intranasal inoculation with 5×103 (Group 1 -▪-), 5×105 (Group 2 -▴-) or 5×107 (Group 3 -♦-) IFU C. abortus or negative control inoculum (Group 4a -+-) prior to pregnancy; or subcutaneous injection with 2×106 IFU C. abortus at 70 days of gestation (Group 5 -•-).
Mentions: Blood samples were taken from the ewes for IFN-γ analysis prior to inoculation and then at specific time points during the course of the first lambing season (at 6 and 17 weeks post inoculation (wpi), at the start of lambing/abortion (22 wpi) and 7 weeks following the lambing/abortion period (36 wpi) (Figure 4). Overall statistical analysis of data from groups 1, 2 and 3 showed no evidence of an effect of ‘group’ or ‘lambing status’ on the mean IFN-γ levels produced by PBMC stimulated with C. abortus antigen, indicating that the difference in mean IFN-γ production between animals that aborted or lambed normally was statistically non-significant, irrespective of the group.

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