http://repub.eur.nl/res/aut/6814/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/29809/ 2008-01-01T00:00:00Z Major problems in the analysis of CD4+effector cell and regulatory T cell (Treg) populations in an activated immune system are caused by the facts that both cell types can express CD25 and that the discriminatory marker forkhead box p3 can only be analyzed in nonviable (permeabilized) cells. Here, we show that CD134 (OX40) can be used as a discriminatory marker combined with CD25 to isolate and characterize viable CD4+effector cells and Tregs. Before and during adjuvant arthritis in rats, coexpression of CD134 and CD25 identified activated Tregs consistently, as these T cells proliferated poorly to disease-associated antigens and were suppressive in vitro and in vivo. Depending on the time of isolation and location, CD4+T cell populations expressing CD134 or CD25 contained effector/memory T cells. Analysis of the function, phenotype, and amount of the CD4+T cell subsets in different lymph node stations revealed spatiotemporal differences in effector cell and Treg compartments during experimental arthritis. http://repub.eur.nl/res/pub/12917/ 2001-02-08T00:00:00Z Long-circulating liposomes (LCL) may be used as targeted antimicrobial drug carriers as they localize at sites of infection. As a result, LCL-encapsulated gentamicin (LE-GEN) has demonstrated superior antibacterial activity over the free drug in a single-dose study of immunocompetent rats with Klebsiella pneumoniae pneumonia. In the present study, the therapeutic efficacy of LE-GEN was evaluated by monitoring rat survival and bacterial counts in blood and lung tissue in clinically relevant models, addressing the issue of impaired host defense and low bacterial antibiotic susceptibility. The results show that in immunocompetent rats infected with the high-GEN-susceptibility K. pneumoniae strain, a single dose of LE-GEN is clearly superior to an equivalent dose of free GEN. Yet complete survival can also be obtained with multiple doses of free GEN. In leukopenic rats infected with the high-GEN-susceptible K. pneumoniae strain, free GEN at the maximum tolerated dose (MTD) was needed to obtain survival. However, with the addition of a single dose of LE-GEN to free-GEN treatment, complete survival can be obtained using a sevenfold-lower cumulative amount of GEN than with free-GEN treatment alone. In leukopenic rats infected with low-GEN-susceptible K. pneumoniae cells, free GEN at the MTD did not result in survival. The use of LE-GEN is needed for therapeutic success. Increasing LE-GEN bilayer fluidity resulted in an increased GEN release from the liposomes and hence improved rat survival, thus showing the importance of the liposome lipid composition for therapeutic efficacy. These results warrant further clinical studies of liposomal formulations of aminoglycosides in immunocompromised patients with severe infections. http://repub.eur.nl/res/pub/9653/ 2001-01-01T00:00:00Z Antimicrobial agents may interact synergistically. But to ensure synergy in vivo, the drugs should both be present at the site of infection at sufficiently high concentrations for an adequate period of time. Coencapsulation of the drugs in a drug carrier may ensure parallel tissue distributions. Since liposomes localize preferentially at sites of infection, this mode of drug delivery could, in addition, increase drug concentrations at the focus of infection. The therapeutic efficacy of gentamicin and ceftazidime coencapsulated into liposomes was examined by monitoring survival in a rat model of an acute unilateral pneumonia caused by antibiotic-susceptible and antibiotic-resistant Klebsiella pneumoniae strains. It is shown that administration of gentamicin in combination with ceftazidime in the free form either as single dose or as 5-day treatment resulted in an additive effect on rat survival in both models. In contrast, targeted delivery of liposome-coencapsulated gentamicin and ceftazidime resulted in a synergistic interaction of the antibiotics in both models. Consequently, liposome coencapsulation of gentamicin and ceftazidime allowed both a shorter course of treatment at lower cumulative doses compared with administration of the antibiotics in the free form to obtain complete survival of rats. Liposomal coencapsulation of synergistic antibiotics may open new perspectives in the treatment of severe infections. http://repub.eur.nl/res/pub/9735/ 2001-01-01T00:00:00Z Liposome-encapsulated amikacin has recently entered clinical trials. The rationale for liposome encapsulation of aminoglycosides is the possibility to increase the therapeutic index of this class of antibiotics by increasing aminoglycoside concentrations at the site of infection and/or by reducing the toxicity of these drugs. Three approaches can be distinguished: the use of liposomes as a depot formulation for local drug administration; targeting of (relatively) short circulating conventional liposomes to the cells of the mononuclear phagocyte system (MPS) for treating intracellular bacterial infections; and targeting of long-circulating liposomes to infectious foci localized outside the MPS. This review discusses the pre-clinical and clinical data in connection with recent developments in liposome technology.