Development of a hamster model of Chlamydophila pneumoniae infection.

The aim of this study was to develop a new experimental model of Chlamydophila pneumoniae infection in the hamster. Intraperitoneal injection of C. pneumoniae purified elementary bodies (EBs) in the hamsters caused a systemic infection, since it was possible to isolate viable chlamydiae from several organs up to 14 days after infection. In particular, spleen infection was detectable up to 7 days post infection in 100% of animals. In contrast, cultures of the organs obtained from intranasally infected animals were far less frequently positive. Systemic infection probably occurred via macrophages, as demonstrated by the presence of intracellular chlamydial inclusions in peritoneal macrophages of peritoneally inoculated animals four days after infection. Furthermore, by infecting LLC-MK2 cells with supernatant preparations obtained from these macrophages, it was possible to observe the development of chlamydial intra-cytoplasmic inclusions after 96 h. Immunization of 18 hamsters with heat-inactivated purified EBs completely protected 16 animals and substantially reduced infection levels in the remaining two. Sera obtained from immunized hamsters prior to challenge reacted mainly against two C. pneumoniae proteins of about 60 kDa, when tested by immunoblot.