title: Mixed infections in vitro with different Chlamydiaceae strains and a cell culture adapted porcine epidemic diarrhea virus.
abstract: Assuming a synergistic or additive effect of Chlamydiaceae in coexistence with other enteropathogenic agents, the viral/bacterial interaction between a cell culture adapted porcine epidemic diarrhea virus (ca-PEDV) and different Chlamydiaceae strains was studied in vitro. Vero cells were dually infected with ca-PEDV and one of the three chlamydial strains Chlamydia trachomatis S45, Chlamydophila abortus S26/3 or Chlamydophila pecorum 1710S. Three experimental protocols were designed varying the inoculation sequence. Cell layers were first inoculated with Chlamydiaceae and 20 h later with ca-PEDV in protocol one. In protocol two, both agents were administered concurrently, whereas in protocol three, ca-PEDV was applied 20 h in advance of the Chlamydiaceae. Immunofluorescence techniques, immunohistochemical (IH) staining and electron microscopy were subsequently employed to investigate the cell layers. Using indirect immunofluorescence (IF) labeling, all mixed infections revealed dually infected cells, however, only incidentally and in low numbers. Characteristically, ca-PEDV syncytia with one or more chlamydial inclusions were detected but dually infected single cells were absent. Some syncytial cells contained enlarged C. abortus or C. pecorum inclusions with abnormally large developmental forms. In comparison with simultaneously conducted monoinfections, larger chlamydial inclusions were observed in dually infected cell layers. Experiments with C. trachomatis showed significantly increased numbers of chlamydial inclusions in dually infected cell layers compared to monoinfected ones. These findings indicate an influence of ca-PEDV on the chlamydial developmental cycle and in the case of C. trachomatis, a positive effect on chlamydial colonization in mixed infections.
authors.affiliation: Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, CH-8057 Zurich, Switzerland.
authors.forename: Angela
authors.initials: A
authors.lastname: Stuedli
authors.forename: Paula
authors.initials: P
authors.lastname: Grest
authors.forename: Irene
authors.initials: I
authors.lastname: Schiller
authors.forename: Andreas
authors.initials: A
authors.lastname: Pospischil
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods / Q000662:veterinary*; D002693:Chlamydiaceae / Q000254:growth & development* / Q000502:physiology; D002522:Chlorocebus aethiops; D018920:Coculture Techniques / Q000379:methods / Q000662:veterinary; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D007150:Immunohistochemistry / Q000662:veterinary; D046529:Microscopy, Electron, Transmission / Q000662:veterinary; D013997:Time Factors; D005760:Transmissible gastroenteritis virus / Q000254:growth & development* / Q000502:physiology; D014709:Vero Cells