Small-animal positron emission tomography in the mouse model of genital Chlamydia infection

Abstract number: O386

Marangoni A., Nanni C., Donati M., Aldini R., di Pierro D., Trespidi S., Accardo S., Fanti S., Cevenini R.

Objectives:Chlamydia trachomatis is one of the world's major causes of sexually transmitted diseases of the cervix and urethra and it is a major agent of pelvic inflammatory disease.

Genital tract infection of female mice with Chlamydia muridarum closely mimics acute genital tract infection in women. Aim of this study was to assess the predictivity of 68Ga-chloride Small Animal Positron Emission Tomography (PET) for the identification of reactive animals and the follow-up of infection at various times after vaginal inoculation.

Methods: Chlamydiae elementary bodies were purified from LLC-MK2 cells by sucrose-gradients density centrifugation.

Animals used in this study were 23 female Balb/c mice, 6–8 weeks old. All the animals received 2.5 mg of medroxyprogesterone acetate i.m. 9 and 2 days prior the infection.

20 mice were infected by placing 15 ml of SPG containing 10⁷ inclusion forming units (IFUs) of C. muridarum into the vaginal vault. Infection was induced under Ketamine anaesthesia. As control, 3 animals were challenged with 15 ml of SPG.

5 infected animals plus 1 control mouse underwent a 68Ga-chloride Small Animal PET. After 60 minutes of uptake, the animals were anaesthetized again and whole body images were acquired for 15 minutes in a single bed position using a Small Animal PET tomography. Images were reconstructed with iterative algorithm. This procedure was performed 5, 12 and 19 days after infection.

Infection was monitored by obtaining cervical-vaginal swabs from all the 20 infected animals 6, 13 and 20 days after infection. Moreover, 5 groups of 3 animals each were sacrificed at 6, 13, 20, 27 and 34 days after infection. Genital tracts were divided into the cervical-vaginal region, uterine horns, and oviducts. Individual wells of LLC-MK2 monolayers in 24-well plates were inoculated with 200 ml of the solution from vaginal swabs or homogenised tissues.

Inclusions were visualised by using fluorescein conjugated monoclonal antibody against Chlamydia group antigen.

Results: Results are summarised in the figure.

Conclusion: These preliminary data indicate that 68Ga-chloride PET is a promising technique to in vivo evaluates inflammatory response to genital C. muridarum infection. Further studies are required to test 68Ga-chloride PET's potential in the follow-up of animals with experimental genital infection after antibiotic treatment.