Action and Reaction: Chlamydophila pneumoniae proteome alteration in a persistent infection induced by iron deficiency

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Abstract
Chlamydophila pneumoniae is an obligate intracellular pathogen implicated in a variety of acute and chronic diseases. Long-term infections are associated with a persistent life stage, in which bacteria can stay for years. They are less accessible to antibiotic treatment but still prone to sustain an inflammatory response. Different in vitro models have been established to mimic and characterize chlamydial persistency. For C. pneumoniae and Chlamydia trachomatis, altered metabolic activities and changed antigenic profiles compared to acute infections have been reported. Most studies including transcriptome and proteome analyses describe persistency induced by IFNγ treatment. Here, we use iron depletion of the infected cell culture that also leads into persistent infection. We describe differently regulated proteins found by subtractive proteome analysis comparing two early stages of infection with and without addition of the iron chelator deferoxamine-mesylate. While only one bacterial protein was up-regulated during iron deficiency up to 24 h post infection (p.i.), 11 were found to be up-regulated and eight to be down-regulated from 24–48 h p.i. Two down-regulated proteins could be identified by peptide mass fingerprinting as thioredoxin reductase and chromosome partitioning protein (ParB). The latter is involved in chromosome segregation. Thus, using a comparative approach we identified on a proteome level down-regulation of ParB in persistent chlamydial forms, which is in agreement with previous results describing changes in cell division and atypical altered morphology of persistent Chlamydiae.