Immunopathology of Chlamydophila abortus infection in sheep and mice

Role of route of delivery on Chlamydia abortus vaccine-induced immune responses and genital tract immunity in mice

We investigated if the efficacy of a Chlamydia abortus (Cab) subunit vaccine is influenced by route of administration. Thus, female CBA/J mice were immunized either by mucosal or systemic routes with Vibrio cholerae ghost (VCG)-based vaccine expressing T and B cell epitopes of Cab polymorphic membrane protein (Pmp) 18D, termed rVCG-Pmp18.3. Vaccine evaluation revealed that all routes of vaccine delivery induced a Th1-type antibody response after a prime boost or three-dose immunization regimen. Also, the intranasal and rectal mucosal and intramuscular systemic routes induced cross-reactive neutralizing antibodies against homologous and heterologous Cab strains. Irrespective of the route of immunization, the vaccine elicited a Th1-type cytokine response (IFN-γ/IL-4 >1) in immunized mice. Analysis of reduction in genital Cab burden as an index of protection showed that immunization induced substantial degrees of protection against infection, irrespective of route of delivery with the intranasal and rectal mucosal routes showing superior levels of protection 12 days postchallenge. Furthermore, there was correlation between the humoral and cellular immune response and protection was associated with the Cab-specific serum IgG antibody avidity and IFN-γ. Thus, while route of administration impacts vaccine efficacy, the rVCG-Pmp18.3-induced protective immunity against Cab respiratory infection can be accomplished by both mucosal and systemic immunization.

Establishment and validation of a real-time fluorescent PCR freeze-dried type assay for 11 sheep and goats pathogens

Small ruminants are economic mainstay in developing countries because of its direct contribution to food security, but the occurrence of epidemics poses a continuous threat. Early diagnosis can strengthen the prevention of zoonosis. Therefore, a high-sensitivity real-time fluorescent PCR freeze-dried type assay that can be stored and transported at room temperature was developed for 11 sheep and goats pathogens in this study. The results showed that there was no non-specific amplification in systems containing different pathogen positive controls; The areas under the ROC curves were all in the range of 0.99-1.00; The LOD counted by Digital PCR were 194, 96, 84, 40, 265, 68, 208, 236, 118, 53 and 723 copies/mL for M. ovis, Pathogenic Leptospira, C. burnetii, BTV, PPRV, Brucella, exJSRV, C. abortus, ORFV, FMDV and CPV, respectively. The coefficients of variation of both intra-group and inter-group replicate tests were less than 5.00 %; The accelerated thermostatic lyophilization test was used to predict the validity period; The LOD of each positive pathogen was still detected after 6 days at 56 ℃, suggesting that the validity period can be at least 567 days at room temperature. In this study, a high-sensitivity real-time fluorescent PCR freeze-dried type assay that can be stored and transported at room temperature was developed for 11 sheep and goats pathogens, which were Mycoplasma ovis (M. ovis), Pathogenic Leptospira, Coxiella burnetii (C. burnetii), Bluetongue virus (BTV), Peste des pestis ruminants virus (PPRV), Brucella, exogenous jaagsiekte sheep retrovirus (exJSRV), Chlamydia abortus (C. abortus), Orf virus (ORFV), Foot-and-mouth disease virus (FMDV), and Capripox virus (CPV).

A novel cold-chain free VCG-based subunit vaccine protects against Chlamydia abortus-induced neonatal mortality in a pregnant mouse model

Chlamydia abortus (Cab) causes spontaneous abortion and neonatal mortality in infected ruminants and pregnant women. Most Cab infections are asymptomatic, although they can be treated with antibiotics, signifying that control of these infections may require alternative strategies, including the use of effective vaccines. However, the limitations imposed by live attenuated and inactivated vaccines further suggest that employment of subunit vaccines may need to be considered. The efficacy of a newly generated Vibrio cholerae ghost (rVCG)-based subunit vaccine harboring the N-terminal portion of the Cab Pmp18D protein (rVCG-Pmp18.3) in preventing Cab-induced abortion or neonatal mortality was evaluated in pregnant mice. Mice were intranasally (IN) immunized and boosted twice, 2 weeks apart with the vaccine, and immunized and unimmunized mice were caged with males 4 weeks postimmunization. The mice were then infected either IN or transcervically (TC) 10 days after pregnancy, and the fertility rate was determined 7 days postpartum. Eight days after delivery, the mice were sacrificed, and Cab infectivity in the lungs and spleens was evaluated by culturing tissue homogenates in tissue culture. Our results demonstrated that the vaccine induced immune effectors that mediated complete clearance of infection in the lungs and significantly reduced Cab infectivity in the spleen following IN immunization. Vaccine immunization also afforded protection against Cab-induced upper genital tract pathology (uterine dilation). Furthermore, while there was no incidence of abortion in both immunized and unimmunized mice, immunized mice were completely protected against neonatal mortality compared to unimmunized infected controls, which lost a significant percentage of their litter 7 days postpartum. Our results establish the capability of the rVCG-Pmp18.3 vaccine to prevent infection in the lungs (mucosal) and spleen (systemic) and protect mice from Cab-induced tubal pathologies and neonatal mortality, a hallmark of Cab infection in ruminants. To advance the commercial potential of this vaccine, future studies will optimize the antigen dose and the number of vaccine doses required for protection of ruminants.

Recent advances and public health implications for environmental exposure to Chlamydia abortus: from enzootic to zoonotic disease

Environmental transmission of Chlamydia abortus as a result of enzootic disease or disease outbreaks and the threats posed by this pathogen has been previously reported, however a state-of-the-science review of these reports and the identification of future research priorities in this area is still lacking. This study provides an overview of the current knowledge of host–pathogen–environment interactions, addressing public health risks and identifying critical questions and research gaps. We performed a systematic PubMed and Web of Science search for publications related to Chlamydia abortus in the past four decades, and we reviewed and combined the evidence critically discussing and commenting the results. A total of 182 studies, 5 chapters of specific books and the “OIE terrestrial manual” were included in this review. There were substantial variations between the studies in topic addressed and experimental design. Overall, the literature largely supports the crucial role played by environmental exposure on the acquisition of zoonotic disease caused by Chlamydia abortus. We also identify the paucity of information related to interspecies transmission and pathogen adaptation in relation to environmental dissemination and zoonotic risk. This analysis further highlights the need for additional research given that environmental transmission represents a serious risk not only to susceptible patients (pregnant women and immunocompromised individuals), but also for other species including wildlife.

Expression Level of the mip, pmp18D, and ompA Genes in Chlamydia abortus Isolated from Aborted Ewes

In this manuscript, we report the proteins macrophage infectivity potentiator (mip, CAB080), major outer membrane protein (momp, CAB048), and polymorphic outer membrane protein (pmp18D, CAB776) that are expressed in different times of pregnancy in mice infected with Chlamydia abortus. Enzootic abortion of ewes (EAE) by C. abortus, an obligate intracellular pathogen, is a critical zoonotic disease-causing significant economic loss to livestock farming globally. This study was carried out for the detection and characterization of macrophage infectivity potentiator (mip, CAB080), major outer membrane protein (momp, CAB048), and polymorphic outer membrane protein (pmp18D, CAB776) using RT-qPCR. These proteins are believed to be expressed as virulence factors in C. abortus isolated from aborted ewes. BALB/c mice (pregnant and nonpregnant) were used as an animal model to be injected intraperitoneally with C. abortus culture in Vero cells since the endometrial lymphoid tissues of these animals resembles that of ewes. Also, the short duration of pregnancy in mice makes them a suitable animal model for obstetric studies. Tissue samples were taken from the mice after 10, 15, and 20 days of pregnancy to compare the expression of the genes mip, pmp18D, and ompA. Transcription level was quantified using RT-qPCR, the GAPDH transcription quantification, as a normalization signal. Abortion occurred in pregnant mice, and apparent differences between the transcriptional levels of the mip, pmp18D, and ompA genes in the samples taken during different time intervals of pregnancy were not observed (p > 0.05). The result indicated that the three bacterial genes, mip, pmp18D, and ompA, play a role as virulence factors in abortion and are differentially expressed in pregnant and nonpregnant animals. Inactivation of the genes is suggested to confirm the hypothesis.

Seroepidemiological feature of Chlamydia abortus in sheep and goat population located in northeastern Iran

Chlamydia abortus is a Gram-negative intracellular bacteria responsible for major economic losses due mainly to infection and subsequent induction of abortion in several animal species and poses considerable public health problems in humans. This study was conducted to determine the prevalence of antibody against C. abortus in sheep and goat population of Khorasan Razavi province located in northeastern Iran. Four hundred fifty-two (271 sheep and 181 goats) sera samples from 40 sheep/goat epidemiologic units located in 11 counties were selected. Sera were assayed for antibodies against C. abortus using ELISA assay. Out of 452 sheep and goat sera, 44 [9.70% (95.00%CI: 7.10%-12.40%)] were positive for C. abortus antibodies. 28 out of 40 epidemiologic units (70.00%) and 10 out of 11 counties (91.00%), at least one seropositive sample was found. There was no significant difference between the seropositivity of sheep and goats. Age, sex, and location did not show significant relationship with the test results. The results showed that C. abortus was circulating in wide parts of Khorasan Razavi province. Considering the economic and public health importance of C. abortus, measures should be taken to help prevent its spread and to reduce the zoonotic risk of C. abortus in the studied region.

The inhibitory effect of flavonoids and their gut-derived metabolites on the replication of Chlamydia abortus in the AH-1 ovine trophoblast cell line

The obligate intracellular bacterium Chlamydia abortus causes abortion and constitutes a worldwide threat for livestock. Plant-derived flavonoids have antimicrobial effects against veterinary and human pathogens and may be of help in the fight against C. abortus. The anti-infective efficacy against C. abortus of the flavonoids apigenin and naringenin, and of four of their derived metabolites was explored using an in vitro model of ovine trophoblast cells. Overall, the anti-infective effectiveness was apigenin > naringenin > benzoic acid > 3-(4-hydroxyphenyl) propionic acid ~ 4-hydroxyphenyl acetic acid ~ 4-hydroxybenzoic. At the lowest concentration tested (10 μM), apigenin, naringenin and benzoic acid inhibited the formation of C. abortus inclusions by 80%, 67%, and 39%, respectively. The cytotoxicity and anti-proliferative effects on the trophoblast host cells also differed greatly between the tested compounds. Our findings suggest that flavonoids may be of therapeutic value against C. abortus infection but metabolic conversion has a substantial and variable effect on their anti-chlamydial activity. Our results also support the notion that the mechanisms of anti-infective action may involve combined effects of the compounds against the host cells and the bacteria.

Development of an in vivo model of Chlamydia abortus chronic infection in mice overexpressing IL-10

Chlamydia abortus, like other members of the family Chlamydiaceae, have a unique intracellular developmental cycle that is characterized by its chronic nature. Infection of a flock can remain undetected for months, until abortion occurs the following reproductive season but, to date, neither the location nor the mechanisms that maintain this latent phase are fully understood. Studies have shown that IL-10 produced as a response to certain micro-organisms sustains the intracellular survival of pathogens and increases host susceptibility to chlamydial infections. In order to induce a sustained infection C. abortus, transgenic mice that constitutively express IL-10 were infected and the immunological mechanisms that maintain infection in these mice were compared with the mechanisms of a resistant wild-type mouse strain. Viable bacteria could be detected in different tissues of transgenic mice up to 28 days after infection, as analysed by bacterial isolation and immunohistochemistry. Chronic infection in these mice was associated with an impaired recruitment of macrophages, decreased iNOS activity at the site of infection and a more diffuse distribution of inflammatory cells in the liver. This murine model can be of great help for understanding the immunological and bacterial mechanisms that lead to chronic chlamydial infections.

Effect of Preventive Chlamydia abortus Vaccination in Offspring Development in Sheep Challenged Experimentally

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.

Late production of CXCL8 in ruminant oro-nasal turbinate cells in response to Chlamydia abortus infection

Chlamydia abortus is an obligate intracellular bacterium that is an important cause of ovine abortion worldwide. There are reports of abortions in cattle, but these are very rare compared to the reported incidence in sheep. The bacterium is transmitted oro-nasally and can establish a sub-clinical infection until pregnancy, when it can invade the placenta and induce an inflammatory cascade leading to placentitis and abortion. Early host-pathogen interactions could explain differential pathogenesis and subsequent disease outcome in ruminant species. In this study, we assessed the ability of sheep and cattle oro-nasal turbinate cells to sense and respond to C. abortus infection. The cells expressed toll like receptor (TLR) 2, TLR4, nucleotide oligomerization domain (NOD) 1 and NOD-like receptor pyrin domain containing 3 (NLRP3) mRNA. In response to C. abortus infection, both ovine and bovine turbinate cells produce CXCL8 mRNA and protein late in the bacterial developmental cycle, but do not produce IL-1β or TNF-α. The UV-inactivated bacteria did not elicit a CXCL8 response, suggesting that intracellular multiplication of the bacteria is important for activating the signalling pathways. The production of innate immune cytokines from cattle and sheep turbinate cells in response to C. abortus infection was found to be largely similar.

Diversification and Distribution of Ruminant Chlamydia abortus Clones Assessed by MLST and MLVA

Chlamydia abortus, an obligate intracellular bacterium, is the most common infectious cause of abortion in small ruminants worldwide and has zoonotic potential. We applied multilocus sequence typing (MLST) together with multiple-locus variable-number tandem repeat analysis (MLVA) to genotype 94 ruminant C. abortus strains, field isolates and samples collected from 1950 to 2011 in diverse geographic locations, with the aim of delineating C. abortus lineages and clones. MLST revealed the previously identified sequence types (STs) ST19, ST25, ST29 and ST30, plus ST86, a recently-assigned type on the Chlamydiales MLST website and ST87, a novel type harbouring the hemN_21 allele, whereas MLVA recognized seven types (MT1 to MT7). Minimum-spanning-tree analysis suggested that all STs but one (ST30) belonged to a single clonal complex, possibly reflecting the short evolutionary timescale over which the predicted ancestor (ST19) has diversified into three single-locus variants (ST86, ST87 and ST29) and further, through ST86 diversification, into one double-locus variant (ST25). ST descendants have probably arisen through a point mutation evolution mode. Interestingly, MLVA showed that in the ST19 population there was a greater genetic diversity than in other STs, most of which exhibited the same MT over time and geographical distribution. However, the evolutionary pathways of C. abortus STs seem to be diverse across geographic distances with individual STs restricted to particular geographic locations. The ST30 singleton clone displaying geographic specificity and represented by the Greek strains LLG and POS was effectively distinguished from the clonal complex lineage, supporting the notion that possibly two separate host adaptations and hence independent bottlenecks of C. abortus have occurred through time. The combination of MLST and MLVA assays provides an additional level of C. abortus discrimination and may prove useful for the investigation and surveillance of emergent C. abortus clonal populations.

Exploiting ovine immunology to improve the relevance of biomedical models

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Sheep make a valuable contribution to immunology research.

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Lessons to be learned from studying infections in the natural host.

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Factors to consider when selecting biomedical models.

Animal models of human disease are important tools in many areas of biomedicine; for example, in infectious disease research and in the development of novel drugs and medical devices. Most studies involving animals use rodents, in particular congenic mice, due to the availability of a wide number of strains and the ease with which they can be genetically manipulated. The use of mouse models has led to major advances in many fields of research, in particular in immunology but despite these advances, no animal model can exactly reproduce all the features of human disease. It is increasingly becoming recognised that in many circumstances mice do not provide the best model and that alternative species may be more appropriate. Here, we describe the relative merits of sheep as biomedical models for human physiology and disease in comparison to mice, with a particular focus on reproductive and respiratory pathogens.

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

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 (5×10³, 5×10⁵ and 5×10⁷ 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 2×10⁶ 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.

IFN-γ expression in placenta is associated to resistance to Chlamydia abortus after intragastric infection

Intragastric infection mimics the natural route of infection of Chlamydia abortus (etiological agent of ovine enzootic abortion). In the mouse model, intragastric experimental infection induces very mild signs of infection followed by late term abortions, as it is shown by the natural ovine host. In order to evaluate the immune mechanisms associated to the dissemination of the pathogen from the gastrointestinal tract, we have administered an intragastric dose of C. abortus to pregnant mice. Systemic and local expression of cytokines, tissue colonization and excretion of bacteria after parturition were monitored during pregnancy. Susceptible CBA/J mice showed a higher bacterial colonization of the placenta and excretion of live bacteria after parturition that were related to a higher local IL-10 expression. By contrast, resistant C57BL/6 mouse strain had higher local IFN-γ mRNA expression in the placenta just before parturition and a transient bacterial colonization of the reproductive tract, with no excretion of C. abortus after parturition. In summary, intragastric infection not only mimics the natural route of infection of C. abortus, but can also be useful in order to understand the immunopathogenesis of chlamydial abortion in the mouse.

Evolutionary relationships among Chlamydophila abortus variant strains inferred by rRNA secondary structure-based phylogeny

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.

Chlamydiaceae infections in pig

Chlamydiaceae are Gram-negative obligate intracellular bacteria. They are responsible for a broad range of diseases in animals and humans. In pigs, Chlamydia suis, Chlamydia abortus, Chlamydia pecorum and Chlamydia psittaci have been isolated. Chlamydiaceae infections in pigs are associated with different pathologies such as conjunctivitis, pneumonia, pericarditis, polyarthritis, polyserositis, pseudo-membranous or necrotizing enteritis, periparturient dysgalactiae syndrome, vaginal discharge, return to oestrus, abortion, mummification, delivery of weak piglets, increased perinatal and neonatal mortality and inferior semen quality, orchitis, epididymitis and urethritis in boars. However, Chlamydiaceae are still considered as non-important pathogens because reports of porcine chlamydiosis are rare. Furthermore, Chlamydiaceae infections are often unnoticed because tests for Chlamydiaceae are not routinely performed in all veterinary diagnostic laboratories and Chlamydiaceae are often found in association with other pathogens, which are sometimes more easily to detect. However, recent studies have demonstrated that Chlamydiaceae infections in breeding sows, boars and piglets occur more often than thought and are economically important. This paper presents an overview on: the taxonomy of Chlamydiaceae occurring in pigs, diagnostic considerations, epidemiology and pathology of infections with Chlamydiaceae in pigs, public health significance and finally on prevention and treatment of Chlamydiaceae infections in pigs.

Chlamydiaceae in cattle: commensals, trigger organisms, or pathogens?

Epidemiological data indicate that infection of cattle with chlamydiae such as Chlamydophila (C.) pecorum, C. abortus, C. psittaci and Chlamydia suis, is ubiquitous with mixed infections occurring frequently. The apparent lack of association between infection and clinical disease has resulted in debate as to the pathogenic significance of these organisms, and their tendency to sub-clinical and/or persistent infection presents a challenge to the study of their potential effects. However, recent evidence indicates that chlamydial infections have a substantial and quantifiable impact on livestock productivity with chronic, recurrent infections associated with pulmonary disease in calves and with infertility and sub-clinical mastitis in dairy cows. Data also suggest these infections manifest clinically when they coincide with a number of epidemiological risk factors. Future research should: (1) use relevant animal models to clarify the pathogenesis of bovine chlamydioses; (2) quantify the impact of chlamydial infection at a herd level and identify strategies for its control, including sub-unit vaccine development; and (3) evaluate the zoonotic risk of bovine chlamydial infections which will require the development of species-specific serodiagnostics.

PREVALÊNCIA DE ANTICORPOS CONTRA OS AGENTES DA MAEDI-VISNA E CLAMIDOFILOSE EM OVINOS NO MUNICÍPIO DE UBERLÂNDIA, MG

RESUMO Objetivou-se com este estudo realizar o primeiro inquérito soro-epidemiológico para o vírus da maedi-visna e Chlamydophila spp. em 12 rebanhos de ovinos do Município de Uberlândia, MG. Foram utilizadas 334 amostras de soro sanguíneo de ovinos e aplicou-se um inquérito epidemiológico a cada propriedade. Os testes realizados para a pesquisa de anticorpos contra o vírus da maedi-visna e Chlamydophila spp. foram imunodifusão em gel de ágar (IDGA) e reação de fixação do complemento (RFC), respectivamente. Não foram detectados ovinos reagentes para maedi-visna. Verificou-se uma prevalência de 3,3% para Chlamydophila spp., com títulos variando de 32 a 64. Não houve diferença estatística significativa (p > 0,05) para os fatores de risco analisados. Ressalta-se a importância dos sistemas de vigilância epidemiológica para atuar no controle dessas infecções, evitando a introdução do vírus da maedi-visna e uma maior propagação da Chlamydophila spp. neste município.

Monitoring clinical outcomes, pathological changes and shedding of Chlamydophila abortus following experimental challenge of periparturient ewes utilizing the natural route of infection

Enzootic abortion of ewes (EAE) caused by Chlamydophila abortus is an important disease resulting in significant lamb loss in most sheep producing countries. Ewes are considered to be naturally infected with C. abortus via the oral-nasal route and may become persistent carriers, shedding during subsequent oestrous cycles and at lambing. The aim of this study was to monitor the clinical outcomes, pathological changes and shedding of C. abortus in 18 periparturient orally infected sheep for two breeding seasons. In the first season, C. abortus was detected by real-time PCR (rt-PCR) in 13/18 conjunctival swabs at oestrus. Three out of the 15 pregnant ewes gave birth to 1 live and 1 dead lamb, and 2 of them aborted. Following parturition/abortion, C. abortus was detected in 12/15 vaginal swabs and in all the collected foetal membranes. However, only those membranes containing high copy numbers of the bacterium displayed the EAE typical lesions. In the second season, none of the 13 pregnant ewes aborted, and 5 of them gave birth to dead or weak lambs. C. abortus was not detected in conjunctival or vaginal swabs at oestrus or parturition. The bacterium was detected at low levels in 36% of the foetal membranes, but with no evidence of histopathological lesions. These results indicate that C. abortus can be detected in a large proportion of animals during the first pregnancy after oral infection. However, this proportion is reduced at the subsequent breeding season, confirming the occurrence of a chronic low level persistent infection in post-abortion/lambing ewes.

Chlamydophila abortus infection in the mouse: a useful model of the ovine disease

Chlamydophila (C.) abortus is an obligate intracellular bacterium able to colonize the placenta of several species of mammals, which may induce abortion in the last third of pregnancy. The infection affects mainly small ruminants resulting in major economic losses in farming industries worldwide. Furthermore, its zoonotic risk has been reported in pregnant farmers or abattoir workers. Mouse models have been widely used to study both the pathology of the disease and the role of immune cells in controlling infection. Moreover, this animal experimental model has been considered a useful tool to evaluate new vaccine candidates and adjuvants that could prevent abortion and reduce fetal death. Future studies using these models will provide and reveal information about the precise mechanisms in the immune response against C. abortus and will increase the knowledge about poorly understood issues such as chlamydial persistence.

Characterization of a murine model of intranasal infection suitable for testing vaccines against C. abortus

Mouse models have been widely used to test candidate vaccines against Chlamydophila abortus infection in mice. Although the induction of a systemic infection by endogenous or intraperitoneal inoculation is a useful tool for understanding the immune mechanism involved in the protection conferred by the vaccination, a different approach is necessary to understand other factors of the infection, such as mucosal immunity or the colonization of target organs. To test whether C. abortus intranasal model of infection in mice is a useful tool for testing vaccines in a first group of experiments mice, were infected intranasally with C. abortus to characterize the model of infection. When this model was used to test vaccines, two inactivated experimental vaccines, one of them adjuvated with QS-21 and another with aluminium hydroxide, and a live attenuated vaccine (strain 1B) were used. Non-vaccinated control mice died within the first 8 days, after displaying substantial loss of weight. Histologically, the mice showed lobar fibrinopurulent bronchointerstitial pneumonia. Prior immunization with QS-21 adjuvated vaccine or 1B vaccine presented mortality and the recipients showed a greater number of T cells in the lesions, especially CD8(+) T cells, than the control mice and mice immunized with vaccine adjuvated with aluminium hydroxide. The results confirm that the C. abortus intranasal model of infection in mice is a useful tool for testing vaccines.

Role of polymorphonuclear neutrophils (PMNs) and NK cells in the protection conferred by different vaccines against Chlamydophila abortus infection

Ovine enzootic abortion (OEA) is caused by Chlamydophila abortus, an intracellular bacterium which acts by infecting the placenta, causing abortion in the last term of gestation. The main prevention strategy against OEA is the vaccination of flocks. An effective vaccine against C. abortus must induce a Th1-like specific immune response, which is characterized by the early production of IFN-gamma and the activation of CD8(+)T cells. Moreover, vaccine effectiveness could be modulated by the functioning of the innate immunity. The purpose of this study was to ascertain how polymorphonuclear neutrophils (PMNs) and NK cells might influence vaccine-induced protection. The live attenuated 1B vaccine and two inactivated experimental vaccines, adjuvated with aluminium hydroxide (AH) or QS-21 (QS), were used in PMN-depleted or NK cell-depleted mice. For PMN depletion, RB6-8C5 monoclonal antibody, which recognizes GR1(+) receptors (Robben, P.M., LaRegina, M., Kuziel, W.A., Sibley, L.D. 2005. Recruitment of Gr-1(+) monocytes is essential for control of acute toxoplasmosis. The Journal of Experimental Medicine 201, 1761-1769.) was used, while for NK cell-depletion the anti-asialo GM1 polyclonal antibody was used. The depletion of PMNs caused 100% mortality in non-vaccinated mice (NV) and 60% mortality in the AH-vaccinated mice by day 10 p.i., while both groups showed a significant increase in their bacterial burden in the liver by day 4 p.i. The depletion of NK cells caused mortality only in the NV group (50% by day 10 p.i.), although this group and the 1B vaccinated mice showed an increased bacterial burden in the liver at day 4 p.i. Our results suggest that the importance of PMNs in inactivated vaccines depends on the adjuvant chosen. The results also demonstrated that the importance of NK cells is greater in live vaccines than in inactivated vaccines.

Relative importance of CD4+ and CD8+ T cells in the resolution of Chlamydophila abortus primary infection in mice

The role of the specific cellular immune response is well established in Chlamydiaceae infections, but the importance of each T-cell subset seems to be species-dependent. This study was designed to clarify the role of T-cell subsets in the response to Chlamydophila abortus primary infection. C57BL/6 mice were depleted of CD4+ or CD8+, or both, by monoclonal antibody injections and subsequently infected with C. abortus. Mice were killed at intervals and samples were collected for bacteriological and histopathological analysis. Also carried out were spleen cell culture, cytokine quantification, immunolabelling for C. abortus antigen, and a TUNEL assay for apoptosis. CD8+ T cell-depleted mice all died within 12 days of C. abortus infection, while no mortality was observed in the other groups; surprisingly, CD4+ T cell-depleted mice showed lower morbidity (expressed as weight loss) than did a non-depleted (control) group. CD8+ T cell-depleted mice also differed from the other groups in showing a significantly higher chlamydial burden in the liver. CD8+ T cell-depleted mice also had a higher number of apoptotic cells in hepatic inflammatory foci and showed exacerbated IFN-gamma production by spleen cells after specific stimulation. Simultaneous depletion of both T-cell subpopulations led to a chronic infection, but not to early mortality. It is concluded that CD8+ T cells may play a role in the regulatory control of the CD4+ T-cell response and may have a direct cytotoxic or IFN-gamma-mediated effect on infected cells.