Severity and Extent of Infection by Chlamidia Pneumoniae: Comparison of C57BL/6 and BALB/C Mice

Stephanie C. Richard, Philadelphia College of Osteopathic Medicine


C. pneumoniae is a gram-negative, obligate, intracellular bacterial pathogen linked to acute respiratory infections. It has recently been implicated in non-respiratory disease processes, such as atherosclerosis and Alzheimer's disease, that are seen in the aging population { {34 Little,C.S. 2005}}. Immunosenescence, or the decreased ability to effectively fight infection with age, is thought to playa role in the inability to clear or limit a localized C. pneumoniae infection. The pathogenesis of these diseases may be related to C. pneumoniae spread to the brain, olfactory bulbs, and cardiovascular system { {34 Little,C.S. 2005}}. While critical studies linking C. pneumoniae infection to the pathogenesis of at hero sci eros is have used C57BLl6 mice { {39 Campbell,L.A. 2004}}, age related studies utilizing the organism have looked at the resolution of acute respiratory infection as well as dissemination to extra-pulmonary sites in BALB/c mice{ {34 Little,C.S. 2005}}. It is therefore imperative to examine the dif1erences between the two strains of mice to ultimately examine the relationship between age and immune response changes in C57BLl6 mice. \Vhile BALB/c mice are known to elicit a classic Th2 response involving cytokines IL-4, IL-5, IL-lO, and IL-13 { {49 Santos,lL. 2006}}, C57BLl6 respond to infection via a Thl response with TNF-a, IFN-y, and lL- 12{ {38 Mills,C.D. 2000}}. It has been hypothesized that a Thl versus Th2 response to C. pneurnoniae infection may playa role in the strain's ef1ectiveness in clearing the infection. Previous studies in our lab have conflrmed the release of these cytokines in response to acute respiratory infection established by C. pneumoniae up to 14 days after inoculation. Further examination of these cytokines, however, is necessary to elucidate their roles in the control of C. pneumoniae infection. The aim of this study was to examine the differences in the ability of BALB/c and C57BLl6 mice to clear C. pneumoniae infection from lung tissue on days 14 and 28 post-infection. This study found that inoculation ofBALB/c and C57BLl6 mice with C. pneumoniae establishes an acute respiratory infection on days 14 and 28 post-infection. There are no statistically significant differences between these two strains of mice in their ability to clear infection with pneumoniae by 28 days post-infection.