IL-17 is believed to be important for protection against extracellular pathogens, where clearance is dependent on neutrophil recruitment and local activation of epithelial cell defences. However, the role of
IL-17 in protection against intracellular pathogens such as Chlamydia is less clear. We have compared (i) the course of natural genital tract C. muridarum
infection, (ii) the development of oviduct pathology and (iii) the development of
vaccine-induced immunity against
infection in wild type (WT) BALB/c and
IL-17 knockout mice (IL-17-/-) to determine if IL-17-mediated immunity is implicated in the development of
infection-induced pathology and/or protection. Both the magnitude and duration of genital
infection was significantly reduced in IL-17-/- mice compared to BALB/c. Similarly, hydrosalpinx was also greatly reduced in IL-17-/- mice and this correlated with reduced neutrophil and macrophage infiltration of oviduct tissues.
Matrix metalloproteinase (
MMP) 9 and MMP2 were increased in WT oviducts compared to IL-17-/- animals at day 7 post-
infection. In contrast, oviducts from IL-17-/- mice contained higher MMP9 and MMP2 at day 21.
Infection also elicited higher levels of Chlamydia-
neutralizing antibody in serum of IL-17-/- mice than WT mice. Following intranasal immunization with C. muridarumMajor Outer
Membrane Protein (MOMP) and
cholera toxin plus CpG adjuvants, significantly higher levels of chlamydial MOMP-specific
IgG and
IgA were found in serum and vaginal washes of IL-17-/- mice. T cell proliferation and IFNγ production by splenocytes was greater in WT animals following in vitro re-stimulation, however vaccination was only effective at reducing
infection in WT, not IL-17-/- mice. Intranasal or transcutaneous immunization protected WT but not IL-17-/- mice against hydrosalpinx development. Our data show that in the absence of
IL-17, the severity of C. muridarum genital
infection and associated oviduct pathology are significantly attenuated, however neither
infection or pathology can be reduced further by vaccination protocols that effectively protect WT mice.