Characteristics of Chlamydia suis Ocular Infection in Pigs

Abstract

Chlamydia (C.) suis can often be isolated from conjunctival swab specimens from pigs with conjunctivitis or keratoconjunctivitis. In the field, it is assumed to be a multifactorial disease triggered by immunosuppressing factors. This is the first experimental study to provoke clinical signs of conjunctivitis in pigs after C. suis primary mono-infection. Five six-week-old male piglets, free of ocular chlamydia shedding and seronegative for Chlamydia, were conjunctivally infected with the C. suis-type strain S45 (1 × 109 inclusion forming units), while four piglets served as negative controls. The infection group developed clinical signs of conjunctivitis with a peak in the first week post-infection. Immunohistochemical evaluation revealed the presence of Chlamydia not only in the conjunctival epithelium, but also in the enlarged lacrimal glands, lungs, and intestine. No circulating antibodies could be detected during the whole study period of three weeks, although three different test systems were applied as follows: the complement fixation test, MOMP-based Chlamydiaceae ELISA, and PmpC-based C. suis ELISA. Meanwhile, high numbers of IFN-γ-producing lymphocytes within PBMC were seen after C. suis re-stimulation 14 days post-infection. Hence, these data suggest that entry via the eye may not elicit immunological responses comparable to other routes of chlamydial infections.

Animal Chlamydiae: A Concern for Human and Veterinary Medicine

“…While C. suis is associated with conjunctivitis or keratoconjunctivitis in pigs [ 3 , 6 ], our understanding of C. suis ocular infections is still limited. Unterweger and colleagues present the first in vivo study, in which an experimental mono-infection with C. suis produced clinical signs of conjunctivitis in piglets [ 7 ]. Apart from eyes, the authors detected C. suis in the lungs and intestines of infected piglets, suggesting systemic infection, but no C. suis -specific antibodies were detected over the course of the three-week study period.…”

A TriAdj-Adjuvanted Chlamydia trachomatis CPAF Protein Vaccine Is Highly Immunogenic in Pigs

“…Based on high similarities regarding size, physiology, reproductive cycles, immunology, and susceptibility to Ct, pigs have been used as biomedical animal models [9][10][11][12], including the study of immunity [13][14][15], STIs [16,17], and Ct vaccine development [18][19][20][21][22]. In addition, pigs can be infected both ocularly [23] and genitally [22,24] with C. suis (Cs). Cs is a chlamydia species not only closely related to Ct, but it is also associated with similar pathologies like conjunctivitis, respiratory infections, reproductive disorders, or enteritis [25,26].…”