Lack of oviduct pathology in mice infected with TLR2-signaling deficient chlamydiae is associated with earlier resolution of oviduct inflammation, and a decreased Th17 response

TLR2 KO mice infected with wild-type C. muridarum strain Nigg and immunologically normal mice infected with plasmid-deficient C. muridarum CM3.1, that fails to activate TLR2, are protected from oviduct pathology during primary and challenge infection. Genital tracts harvested from normal mice sacrificed 7, 14, 21, and 28 days post infection with Nigg or CM3.1 were examined histologically. On day 14, neutrophil infiltrates were significantly decreased in the oviducts from mice infected with CM3.1 versus oviducts from mice infected with Nigg. On days 21 and 28, neutrophils and lymphocytes were significantly decreased in oviducts of mice infected with CM3.1 versus Nigg. Quantitative culture of oviduct homogenates thru 35 days post infection revealed equivalent bacterial burden and resolution of infection in both groups by day 19. Significant amounts of TNF, IL-1α, IL-1β, IL-6, GM-CSF, G-CSF, MIP-2, KC and IFN-γ were detected by bead assay in the oviduct homogenates of Nigg-infected mice on days 9 through 15, but were low or undetectable in mice infected with CM3.1. ELISPOT for IFN-γ and IL-17 producing CD4 T cells in iliac nodes reveal significantly increased Th17 cells on days 7 and 20 post infection in Nigg-infected mice. Chlamydial-induced TLR2 signaling promotes enhanced cytokine production, prolonged oviduct inflammation, and activation of Th17 cells that may contribute to induction of pathology.