Chemokine and chemokine receptor dynamics during genital chlamydial infection

Abstract

Current design strategies for vaccines against certain microbial pathogens, including Chlamydia trachomatis, require the induction and targeting of specific immune effectors to the local sites of infection known as the mucosal effector sites. Chemokines and their receptors are important mediators of leukocyte trafficking and of the controlled recruitment of specific leukocyte clonotypes during host defense against infections and during inflammation. We analyzed the dynamics of chemokine and chemokine receptor expression in genital mucosae during genital chlamydial infection in a murine model to determine how these molecular entities influence the development of immunity and the clearance of infection. A time course study revealed an increase of up to threefold in the levels of expression of RANTES, monocyte chemotactic protein 1 (MCP-1), gamma-interferon-inducible protein 10 (IP-10), macrophage inflammatory protein 1alpha (MIP-1alpha), and intercellular adhesion molecule type 1 (ICAM-1) after genital infection with the C. trachomatis agent of mouse pneumonitis. Peak levels of expression of RANTES, MCP-1, and MIP-1alpha occurred by day 7 after primary infection, while those of IP-10 and ICAM-1 peaked by day 21. Expression levels of these molecules decreased by day 42 after primary infection, by which time all animals had resolved the infection, suggesting an infection-driven regulation of expression. A rapid upregulation of expression of these molecules was observed after secondary infection. The presence of cells bearing the chemokine receptors CCR5 and CXCR3, known to be preferentially expressed on Th1 and dendritic cells, was also synchronous with the kinetics of immune induction in the genital tract and clearance of infection. Results demonstrated that genital chlamydial infection is associated with a significant induction of chemokines and chemokine receptors that are involved in the recruitment of Th1 cells into the site of infection. Future studies will focus on how selective modulation of chemokines and their receptors can be used to optimize long-term immunity against CHLAMYDIA:

FIG. 1.

Chemokine induction during genital chlamydial infection. Female BALB/c mice were infected intravaginally with 10⁵ IFU of MoPn. Total RNAs isolated from genital tract tissues at the indicated time points (days) after the primary (1°) and secondary (2°) infections were analyzed by a semiquantitative RT-PCR to assess the expression levels of RANTES, MCP-1, MIP-1α, IP-10, ICAM-1, and β-actin. NI, noninfected genital tissues; Inf, infection.

FIG. 2.

Semiquantitation of chemokine expression levels during genital chlamydial infection. Results presented in Fig. 1 were normalized to those for β-actin in each reaction. Results are expressed as the mRNA level (i.e., the ratio of the chemokine band to that of β-actin) versus time, as indicated in Fig. 1.

FIG. 3.

Kinetics of Th1 induction in genital mucosae after genital chlamydial infection. Nylon wool-purified genital tract T cells were isolated from infected mice at the indicated time points. The cells were stimulated with chlamydial antigen plus APCs for 5 days, and the amounts of IFN-γ in the culture supernatants were measured by enzyme-linked immunosorbent assays (15). The concentrations of IFN-γ are expressed as the mean of results from at least three different experiments. Control cultures containing T cells and APCs without chlamydial antigen had no measurable amounts of IFN-γ, and so the data are not presented.

FIG. 4.

Course of genital chlamydial infection. Female BALB/c mice were infected intravaginally with 10⁵ IFU of MoPn. The course of the infection was monitored by periodic (every 3 days) cervicovaginal swabbing of individual animals. Chlamydiae isolated from cervicovaginal swabs in tissue culture were assayed by staining infected monolayers of McCoy cells with fluorescein isothiocyanate-labeled, genus-specific antibody as described in Materials and Methods. The animals were monitored for 6 weeks. Experiments were repeated twice, making for a total of 10 animals per experimental group.

FIG. 5.

Chemokine receptor expression in genital mucosae during genital chlamydial infection. Female BALB/c mice were infected intravaginally with 10⁵ IFU of MoPn. Total RNAs isolated from genital tract tissues at the indicated time points (days) after the primary and secondary infections were analyzed by a semiquantitative RT-PCR to assess the expression of CCR5 and CXCR3, as described in Materials and Methods and the legend to Fig. 1. Lane M, molecular size markers. NI, noninfected genital tissues.

FIG. 6.

Semiquantitation of expression of chemokine receptors CCR5 (a) and CXCR3 (b) in genital mucosae during genital chlamydial infection. Results presented were normalized to those for β-actin in each reaction.