Dataset Information

Pathogenic outcome following experimental infection of sheep with Chlamydia abortus variant strains LLG and POS.

ABSTRACT: This study investigated the pathogenesis of two variant strains (LLG and POS) of Chlamydia abortus, in comparison to a typical wild-type strain (S26/3) which is known to be responsible for late term abortion in small ruminants. Challenge with the three strains at mid-gestation resulted in similar pregnancy outcomes, with abortion occurring in approximately 50-60% of ewes with the mean gestational lengths also being similar. However, differences were observed in the severity of placental pathology, with infection appearing milder for strain LLG, which was reflected in the lower number of organisms shed in vaginal swabs post-partum and less gross pathology and organisms present in placental smears. Results for strain POS were somewhat different than LLG with a more focal restriction of infection observed. Post-abortion antibody responses revealed prominent differences in seropositivity to the major outer membrane protein (MOMP) present in elementary body (EB) preparations under denaturing conditions, most notably with anti-LLG and anti-POS convalescent sera where there was no or reduced detection of MOMP present in EBs derived from the three strains. These results and additional analysis of whole EB and chlamydial outer membrane complex preparations suggest that there are conformational differences in MOMP for the three strains. Overall, the results suggest that gross placental pathology and clinical outcome is not indicative of bacterial colonization and the severity of infection. The results also highlight potential conformational differences in MOMP epitopes that perhaps impact on disease diagnosis and the development of new vaccines.

SUBMITTER: Livingstone M

PROVIDER: S-EPMC5426687 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Pathogenic outcome following experimental infection of sheep with Chlamydia abortus variant strains LLG and POS.

Livingstone Morag M Wheelhouse Nicholas N Ensor Hannah H Rocchi Mara M Maley Stephen S Aitchison Kevin K Wattegedera Sean S Wilson Kim K Sait Michelle M Siarkou Victoria V Vretou Evangelia E Entrican Gary G Dagleish Mark M Longbottom David D

PloS one 20170511 5

This study investigated the pathogenesis of two variant strains (LLG and POS) of Chlamydia abortus, in comparison to a typical wild-type strain (S26/3) which is known to be responsible for late term abortion in small ruminants. Challenge with the three strains at mid-gestation resulted in similar pregnancy outcomes, with abortion occurring in approximately 50-60% of ewes with the mean gestational lengths also being similar. However, differences were observed in the severity of placental patholog ...[more]

PMID: 28494018

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Project description:Ovine enzootic abortion, caused by Chlamydia abortus, leads to important economic losses worldwide. In addition to reproductive failures, infection may impact lamb growth during the first weeks after birth, yet this effect has not been well characterized. Vaccination can help to control the disease but variable efficacy values have been described, possibly related with factors associated with the host, the vaccine, the parameter used for efficacy determination, and the challenge conditions. In this context, we evaluated the efficacy of an inactivated standard commercial vaccine and a 1/2 diluted dose in pregnant sheep challenged with C. abortus by examining multiple indicators of vaccine effect (including incidence of reproductive failures, bacterial excretion, and evolution of weight gain of viable lambs during the first month of life). Three groups of ewes [control non-vaccinated, C (n?=?18); vaccinated with standard dose, SV (n?=?16); and vaccinated with 1/2 dose, DV (n?=?17)], were challenged approximately 90?days post-mating and tested using direct PCR (tissue samples and vaginal swabs) and ELISA (serum) until 31?days post-reproductive outcome. There were not significant differences in the proportions of reproductive failures or bacterial shedding after birth/abortion regardless the vaccination protocol. However, a beneficial effect of vaccination on offspring growth was detected in both vaccinated groups compared with the controls, with a mean increase in weight measured at 30?days of life of 1.5 and 2.5?kg (p?=?0.056) and an increase in the geometric mean of the daily gain of 8.4 and 9.7% in lambs born from DV and SV ewes compared with controls, respectively. Our results demonstrate the effect of an inactivated vaccine in the development of the offspring of C. abortus-infected ewes at a standard and a diluted dose, an interesting finding given the difficulty in achieving sufficient antigen concentration in the production of enzootic abortion of ewes-commercial vaccines.

Project description:BACKGROUND: Chlamydia pecorum is an important pathogen of domesticated livestock including sheep, cattle and pigs. This pathogen is also a key factor in the decline of the koala in Australia. We sequenced the genomes of three koala C. pecorum strains, isolated from the urogenital tracts and conjunctiva of diseased koalas. The genome of the C. pecorum VR629 (IPA) strain, isolated from a sheep with polyarthritis, was also sequenced. RESULTS: Comparisons of the draft C. pecorum genomes against the complete genomes of livestock C. pecorum isolates revealed that these strains have a conserved gene content and order, sharing a nucleotide sequence similarity?>?98%. Single nucleotide polymorphisms (SNPs) appear to be key factors in understanding the adaptive process. Two regions of the chromosome were found to be accumulating a large number of SNPs within the koala strains. These regions include the Chlamydia plasticity zone, which contains two cytotoxin genes (toxA and toxB), and a 77 kbp region that codes for putative type III effector proteins. In one koala strain (MC/MarsBar), the toxB gene was truncated by a premature stop codon but is full-length in IPTaLE and DBDeUG. Another five pseudogenes were also identified, two unique to the urogenital strains C. pecorum MC/MarsBar and C. pecorum DBDeUG, respectively, while three were unique to the koala C. pecorum conjunctival isolate IPTaLE. An examination of the distribution of these pseudogenes in C. pecorum strains from a variety of koala populations, alongside a number of sheep and cattle C. pecorum positive samples from Australian livestock, confirmed the presence of four predicted pseudogenes in koala C. pecorum clinical samples. Consistent with our genomics analyses, none of these pseudogenes were observed in the livestock C. pecorum samples examined. Interestingly, three SNPs resulting in pseudogenes identified in the IPTaLE isolate were not found in any other C. pecorum strain analysed, raising questions over the origin of these point mutations. CONCLUSIONS: The genomic data revealed that variation between C. pecorum strains were mainly due to the accumulation of SNPs, some of which cause gene inactivation. The identification of these genetic differences will provide the basis for further studies to understand the biology and evolution of this important animal pathogen.

Project description:The evolutionary relationships among known Chlamydophila abortus variant strains including the LLG and POS, previously identified as being highly distinct, were investigated based on rRNA secondary structure information. PCR-amplified overlapping fragments of the 16S, 16S-23S intergenic spacer (IS), and 23S domain I rRNAs were subjected to cloning and sequencing. Secondary structure analysis revealed the presence of transitional single nucleotide variations (SNVs), two of which occurred in loops, while seven in stem regions that did not result in compensatory substitutions. Notably, only two SNVs, in 16S and 23S, occurred within evolutionary variable regions. Maximum likelihood and Bayesian phylogeny reconstructions revealed that C. abortus strains could be regarded as representing two distinct lineages, one including the "classical" C. abortus strains and the other the "LLG/POS variant", with the type strain B577(T) possibly representing an intermediate of the two lineages. The two C. abortus lineages shared three unique (apomorphic) characters in the 23S domain I and 16S-23S IS, but interestingly lacked synapomorphies in the 16S rRNA. The two lineages could be distinguished on the basis of eight positions; four of these comprised residues that appeared to be signature or unique for the "classical" lineage, while three were unique for the "LLG/POS variant". The U277 (E. coli numbering) signature character, corresponding to a highly conserved residue of the 16S molecule, and the unique G681 residue, conserved in a functionally strategic region also of 16S, are the most pronounced attributes (autapomorphies) of the "classical" and the "LLG/POS variant" lineages, respectively. Both lineages were found to be descendants of a common ancestor with the Prk/Daruma C. psittaci variant. Compared with the "classical", the "LLG/POS variant" lineage has retained more ancestral features. The current rRNA secondary structure-based analysis and phylogenetic inference reveal new insights into how these two C. abortus lineages have differentiated during their evolution.

Dataset Information

Pathogenic outcome following experimental infection of sheep with Chlamydia abortus variant strains LLG and POS.

Publications

Pathogenic outcome following experimental infection of sheep with Chlamydia abortus variant strains LLG and POS.

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