Conjugation of hydroxyethyl starch to desferrioxamine (DFO) modulates the dual role of DFO in Yersinia enterocolitica infection

Abstract

The iron chelator desferrioxamine (DFO) B is widely used in the therapy of patients with iron overload. As a side effect, DFO may favor the occurrence of fulminant Yersinia infections. Previous work from our laboratory showed that this might be due to a dual role of DFO: growth promotion of the pathogen and immunosuppression of the host. In this study, we sought to determine whether conjugation of DFO to hydroxyethyl starch (HES-DFO) may prevent exacerbation of Yersinia infection in mice. We found HES-DFO to promote neither growth of Yersinia enterocolitica nor mitogen-induced T-cell proliferation and gamma interferon production by T cells in vitro. Nevertheless, in vivo HES-DFO promoted growth of Y. enterocolitica possibly due to cleavage of HES and release of DFO. The pretreatment of mice with DFO resulted in death of all mice 2 to 5 days after application of a normally sublethal inoculum of Y. enterocolitica, while none of the mice pretreated with HES-DFO died within the first 7 days postinfection. However, some of the HES-DFO-treated mice died 8 to 14 days postinfection. Thus, due to the delayed in vivo effect HES-DFO failed to trigger Yersinia-induced septic shock, which accounts for early mortality in DFO-associated septicemia. Moreover, our data suggest that DFO needs to be taken up by host cells in order to exert its immunosuppressive action. These results strongly suggest that HES-DFO might be a favorable drug with fewer side effects than DFO in terms of DFO-promoted fulminant infections.

FIG. 1

Inhibition of ConA-induced proliferation of SMNC by serial dilutions of DFO B (DFO), FO B (FO), HES-DFO, and HES-FO, respectively. Values from cultures containing SMNC and ConA only were taken as 100%.

FIG. 2

IFN-γ production by splenic T cells of BALB/c mice after coincubation with 100 μM DFO, FO, HES-DFO, and HES-FO. T cells were stimulated with 3 μg of ConA per ml in the presence of irradiated feeder cells in macroculture wells. Supernatants were harvested 24 h later and used in an IFN-γ-specific ELISA (see Materials and Methods). The values shown are the means ± standard deviations from triplicates.

FIG. 3

Survival of mice after Y. enterocolitica infection modulated by 1 ml of 8 mM DFO (n = 20; black dots) or HES-DFO (n = 12; open circles). All control mice pretreated with PBS did survive the Y. enterocolitica infection (n = 15; black triangles).

FIG. 4

Effects of in vivo administration of PBS, DFO, and HES-DFO on clearance of Y. enterocolitica from the spleen of sublethally (0.7 × 10⁵ CFU) infected BALB/c mice determined on days 2 and 4 postinfection (p.i.). Results are means ± standard deviations of eight animals. The asterisks indicate statistically significant differences (P < 0.05).