Chlamydia trachomatis is a Gram-negative obligate intracellular bacterial pathogen. It is the leading cause of bacterial sexually transmitted disease in the world, with more than 100 million new cases of genital tract infections with C. trachomatis occurring each year. Animal models are indispensable for the study of C. trachomatis infections and the development and evaluation of candidate vaccines. In this paper, the most commonly used animal models to study female genital tract infections with C. trachomatis will be reviewed, namely, the mouse, guinea pig, and nonhuman primate models. Additionally, we will focus on the more recently developed pig model. Chlamydia trachomatis, a Gram-negative obligate intracellular bacterium, is the leading cause of bacterial sexually transmitted disease. World Health Organization values for 2008 estimated an annual increase of over 100 million genital tract infections with C. trachomatis worldwide (1). The incidence of cases is increasing in many countries (1, 2). Genital tract infections with C. trachomatis can cause cervicitis in women and urethritis in men. However, these infections remain largely subclinical in approximately 70% of women and 50% of men and consequently are often not detected (3). Untreated infections may lead to pelvic inflammatory disease, tubal scarring, ectopic pregnancy, infertility, and chronic pelvic pain in women, epididymitis in men, and infant pneumonia in children (4-7). Uncomplicated chlamydial infections can be treated easily with antibiotics, but once infection and pathology are established, treatment may be less effective. Asymptomatic individuals can be identified through screening programs, but this approach is likely to be too costly for developing countries. A vaccination program would be much cheaper and have a greater impact in controlling C. trachomatis infections worldwide. Computer modeling suggests that even a partially efficacious chlamydial vaccination program would rapidly reduce the prevalence of genital infection (8). Animal models are indispensable for the study of C. trachomatis infections and the development and evaluation of candidate vaccines. Various animal models have been developed, including mouse (9, 10), guinea pig (11, 12), nonhuman primate (13,14), pig (15), rat (16), and rabbit (17) models. Here, the most commonly used animal models to study female genital tract infections with C. trachomatis will be reviewed, namely, the mouse, guinea pig, and nonhuman primate models. Additionally, we will focus on the more recently developed pig model. MOUSE MODELSMice are the most commonly used animals to study genital chlamydial infections. The advantages of the mouse model are their small size, ease of handling, availability in sufficient amounts, and low cost. Moreover, there are many well-characterized inbred and knockout mouse strains available (18). The female mouse genital tract is susceptible to infection with both Chlamydia muridarum (9) and C. trachomatis (10), which has resulted in the establishment of two murine mod...

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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.

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.

As aerosolization was an easy and effective method to deliver complexes to the vaginal tract of pigs, we believe this application technique has future potential for both vaginal and perhaps nasal vaccination using non-viral gene delivery vectors.