Katelijn Schautteet

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.

Tetracycline-resistant Chlamydia suis in cases of reproductive failure on Belgian, Cypriote and Israeli pig production farms.

Similar cases of severe reproductive failure associated with the presence of Chlamydia suis in two Belgian, one Cypriote and one Israeli pig farrowing to slaughter farms are presented. Vaginal and rectal swabs from 39 sows were examined by culture and DNA microarray. Nineteen of 23 (83 %) C. suis-positive sows were infected with tetracycline-resistant C. suis strains, as determined by MIC tests. Furthermore, boar semen from a German artificial insemination centre, intended for export, was positive for C. suis. Emergence of tetracycline-resistant C. suis strains was confirmed.

Chlamydia trachomatis Vaccine Research through the Years

Chlamydia trachomatis is a Gram-negative obligate intracellular bacterium. It is the leading cause of bacterial sexual transmitted infections (STIs). World Health Organization figures estimated that over 90 million new cases of genital C. trachomatis infections occur worldwide each year. A vaccination program is considered to be the best approach to reduce the prevalence of C. trachomatis infections, as it would be much cheaper and have a greater impact on controlling C. trachomatis infections worldwide rather than a screening program or treating infections with antibiotics. Currently, there are no vaccines available which effectively protect against a C. trachomatis genital infection despite the many efforts that have been made throughout the years. In this paper, the many attempts to develop a protective vaccine against a genital C. trachomatis infection will be reviewed.

Protection of pigs against genital Chlamydia trachomatis challenge by parenteral or mucosal DNA immunization

The current study evaluates combined aerosol-vaginal delivery of a MOMP-based Chlamydia trachomatis (serovar E) DNA vaccine in a pig genital challenge model. Most non-replicating antigens are rather poor mucosal immunogens in comparison to replicating antigens. Therefore, a mucosal administered DNA vaccine, which actually mimics a live vaccine, could be promising. Protection was promoted by plasmids encoding the porcine granulocyte macrophage-colony stimulating factor (pcDNA3.1zeo::GM-CSF), the Escherichia coli thermo-labile enterotoxin (LT) subunit A (plasmid PJV2004::LTa) and subunit B (plasmid PJV2005::LTb). Mucosal C. trachomatis DNA vaccination induced significant protection against genital C. trachomatis challenge although the infection could not be eradicated. Intradermal immunization was significantly less efficient in protecting experimentally infected pigs. Protection was correlated with efficient T cell priming and significantly higher serum IgA titers following primo vaccination.

Protection of pigs against Chlamydia trachomatis challenge by administration of a MOMP-based DNA vaccine in the vaginal mucosa

Plasmid DNA (pWRG7079::MOMP) expressing the major outer membrane protein of a human Chlamydia trachomatis serovar E strain was tested for the ability to induce an immune response and protect against experimental genital infection with the same serovar. The vaccine was tested in pigs, as they are genetically and physiologically related to humans and suitable for studying C. trachomatis infection of the genital system. To increase the immune response, GM-CSF, LTA and B and CpG motives were used as adjuvants. GM-CSF was administered seven days before immunization, while the other adjuvants were administered together with the vaccine. Ten pigs were randomly divided into two groups. One group received an intravaginal primo-vaccination and a booster of 500 μg pWRG7079::MOMP, while the other group received the placebo vaccine pWRG7079. All animals were challenged with 10(8) TCID(50) of C. trachomatis serovar E. Pigs immunized with the DNA vaccine showed significantly less macroscopic lesions, vaginal excretion and chlamydial replication in the genital tract, as compared to placebo-vaccinated controls. However, infection could not be completely cleared.

Possible pathogenic interplay between Chlamydia suis, Chlamydophila abortus and PCV-2 on a pig production farm

A concurrent outbreak of chlamydial disease in boars, sows and gilts and postweaning multisystemic wasting syndrome (PMWS) in weaned piglets was investigated on a large pig production farm in Estonia. Chlamydia suis DNA was detected in conjunctival swabs from boars, sows and gilts, but also in the faeces of boars and sows. Chlamydophila abortus DNA was found in semen, and in conjunctival swabs from sows; DNA was demonstrated by microarrays. Serum samples from boars were examined using a Chlamydiaceae-specific recombinant ELISA. All 10 serum samples examined were positive (1:960 to 1:3840). Chlamydiosis was characterised by reproductive failure and conjunctivitis. Piglets were not examined for Chlamydiaceae, as eye problems were not observed. Piglets showed wasting, respiratory signs, diarrhoea, enlargement of lymph nodes and increased mortality (10 per cent). Porcine circovirus type 2 (PCV-2) was detected in the lymph nodes of piglets by immunohistochemistry, and PCV-2 antibodies were demonstrated in all 10 serum samples from sows examined using an immunoperoxidase monolayer assay.

Validation of the Chlamydia trachomatis genital challenge pig model for testing recombinant protein vaccines.

Chlamydia trachomatis is a Gram-negative obligate intracellular bacterial pathogen that is the leading cause of bacterial sexually transmitted disease in humans in developing countries. A vaccination programme is considered to be the best approach to reduce the prevalence of C. trachomatis infections. However, there are still no commercial C. trachomatis vaccines. In order to develop effective C. trachomatis vaccines, it is important to identify those antigens that elicit a protective immune response, and to develop new and adequate methods and adjuvants for effective vaccine delivery, as conventional methods have failed to induce protective immunity. In order to test different vaccine candidates, animal models are needed. Former studies have used non-primate monkeys, mice or guinea pig infection models. The present study used a pig model for testing recombinant protein vaccines. Two recombinant proteins, polymorphic membrane protein G (PmpG), and secretion and cellular translocation protein C (SctC), were tested for their ability to create protection in a pig C. trachomatis challenge model. The vaccines were administered subcutaneously with GNE adjuvant. Six weeks later, animals were challenged intravaginally with C. trachomatis serovar E. After a further 4 weeks, the pigs were euthanized. PmpG-immunized pigs were better protected than pigs immunized with the less promising SctC candidate vaccine antigen. Interestingly, significant protection was apparently not correlated with a strong humoral immune response upon subcutaneous immunization. In conclusion, the pig model is useful for studying the efficacy of vaccine candidates against genital human C. trachomatis infection.

Protection of budgerigars (Melopsittacus undulatus) against Chlamydophila psittaci challenge by DNA vaccination

Plasmid DNA (pcDNA1::MOMP A) expressing the major outer membrane protein (MOMP) of Chlamydophila psittaci genotype A strain 89/1051 has been tested for its ability to induce protective immunity against Cp. psittaci challenge in budgerigars. Eight pairs of male and female budgerigars were housed in eight separate bird cages placed in two negative pressure isolators, four cages per group. All budgerigars were immunised twice intramuscularly with 100 microasmid DNA. Both groups received a primary DNA inoculation at day 0 followed by a booster inoculation 3 weeks later. Group 1 received pcDNA1::MOMP A, while group 2 received the placebo vaccine pcDNA1. Budgerigars were challenged by aerosol 2 weeks following the booster vaccination. The challenge consisted of 10(8) TCID(50) of the homologous Cp. psittaci genotype A strain. Cloacal and pharyngeal swabs of all budgerigars, taken prior to the experimental infection were negative in both PCR and culture. However, all budgerigars showed low pre-existing serum antibody titres. This indicates that animals were previously infected. Nevertheless, DNA immunisation could significantly reduce clinical signs, macroscopic lesions, pharyngeal and cloacal excretion as well as chlamydial replication, even in the presence of pre-existing serum antibodies, as compared to the placebo-vaccinated controls.

Primary infection with Chlamydia trachomatis L2c in a porcine model produced urogenital pathology similar as in humans and failed to induce protective immune responses against re-infection

Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium. Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium. Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B9820 Merelbeke, Belgium. Center for Immunobiology and Vaccine Development, Children’s Hospital Oakland, Research Institute, Oakland, California, USA. *shared senior authorship