Clostridium difficile is a spore-forming bacterium, the toxin-producing strains of which cause colitis. Risk factors are antibiotics, advanced age and severe comorbidity. C. difficile infection ... Show moreClostridium difficile is a spore-forming bacterium, the toxin-producing strains of which cause colitis. Risk factors are antibiotics, advanced age and severe comorbidity. C. difficile infection (CDI) has been regarded as mostly a hospital-acquired infection. Preventing relapses is considered the biggest challenge in CDI management. In this thesis, we show that CDI occurs in Dutch general practices, often in patients without contact with hospitals. Also, we show that the emerging virulent strain PCR ribotype 027 has not become dominant in European hospitals, but community-associated type 078 has become highly prevalent. Furthermore, we found that cystic fibrosis outpatients are frequently colonized with C. difficile, though mostly with nonpathogenic strains. Thus, acquisition of C. difficile in the community appears more important than previously thought. Next, we show that renal failure at the time of diagnosis predicts relapses. In addition, patients who fail to develop antibodies against C. difficile toxins have a higher chance of relapse. We describe an experimental product derived from the milk of cows vaccinated against C. difficile and its toxins, which might prevent relapses. The last part of the thesis consists of the European guideline for CDI treatment and its recent update Show less
This dissertation deals with the role of local immune stimulation in the lymph node and tumor microenvironment and its effect on systemic CD8+ T cell responses, in particular the anti-tumor CD8+ T... Show moreThis dissertation deals with the role of local immune stimulation in the lymph node and tumor microenvironment and its effect on systemic CD8+ T cell responses, in particular the anti-tumor CD8+ T cell responses. In chapter 2 the use of a slow-release system is described to deliver the immune-activating agonistic CD40 antibody to the tumor-draining area, and the advantages of this method over systemic administration of the antibody. The local, slow-release administration was very effective in activating a systemic anti-tumor effector CD8+ T cell response, to such an extent that a tenfold lower dose of antibody could be used without loss of efficacy. Adverse side-effects, analyzed by organ histology and liver enzymes in the blood, were much lower upon local anti-CD40 antibody delivery compared to systemic administration. The local delivery of anti-CD40 antibody resulted in a systemic anti-tumor CD8+ T cell response, capable of clearing distant tumors expressing identical tumor antigens. Chapter 3 shows that slow-release local administration of CTLA-4 blocking antibody can also activate a tumor-specific CD8+ T cell response and cause tumor regression, while lowering systemic adverse side-effect as compared to systemic administration. CTLA-4 blocking antibody is being widely used in clinical trials, and its use has been complicated by induction of auto-immune disease. Here we show that using a local low dose injection of CTLA-4 blocking antibody in a slow-release formulation is equally effective in activating a tumor-specific CD8+ T cell response, capable of eradicating tumor cells as systemic high dose treatment. The influence of local lymph node activation on systemic T cell responses is further analyzed in chapter 4. CD8+ T cell priming generally occurs in a locally inflamed lymph node, called a reactive LN, due to the presence of pathogens. The role of the inflammatory milieu on the priming and fate of CD8+ T cells was studied by separating the TCR-MHC interaction from the inflammatory cues, by priming briefly in vitro followed by transfer to mice with or without a CpG-induced reactive lymph node. The primary CD8+ T cell response was not influenced by the presence of a reactive lymph node, however, after a boost vaccination in the memory phase, CD8+ T cells primed in the presence of a reactive LN displayed a strong quantitative advantage over control CD8+ T cells. The reactive LN, which remained swollen with enhanced cellularity for a pronounced period of time, was envisaged to act as a shelter for CD8+ T cells while undergoing contraction after the primary response. In chapter 5, the advantages and disadvantages of the use of dextran-based microparticles as slow-release system for the delivery of immune-activating antibodies such as agonistic CD40 in the tumor-draining area are described. Dextran-based microparticles can be tailored to release antibodies in desired pharmacokinetics, leading to an even further decrease of adverse side-effects, as compared to previously described Montanide-ISA 51. However, dextran-based particles were unexpectedly found to have a stimulating effect on tumor-outgrowth. This effect coincided with the appearance of large, ulcerated swellings at the site of injection. In chapter 6, the issues presented in this thesis are discussed. The knowledge gained in the work shown here, compared with and strengthened by related published work, is used to state the opinion that targeting the tumor-draining lymph node and/or tumor microenvironment for immune-activating therapy against tumors must be seriously considered. Show less
