Fc-dependent depletion of activated T cells occurs through CD40L-specific antibody rather than costimulation blockade

Although the underlying mechanisms are not well understood, it is generally believed that antigen recognition by T cells in the absence of costimulation may alter the immune response, leading to anergy or tolerance. Further support for this concept comes from animal models of autoimmunity and transplantation, where treatments based on costimulation blockade, in particular CD40 ligand (CD40L)-specific antibodies, have been highly effective. We investigated the mechanisms of action of an antibody to CD40L and provide evidence that its effects are dependent on the constant (Fc) region. Prolongation of graft survival is dependent on both complement- and Fc receptor-mediated mechanisms in a major histocompatibility complex (MHC)-mismatched skin transplant model. These data suggest that antibodies to CD40L act through selective depletion of activated T cells, rather than exerting immune modulation by costimulation blockade as currently postulated. This finding opens new avenues for treatment of immune disorders based on selective targeting of activated T cells.     

Molecular monitoring of the Leu-164 mutation of dihydrofolate reductase in a highly sulfadoxine/pyrimethamine-resistant area in Africa

Background

Procalcitonin (PCT) is closely correlated with parasite burden and clinical outcome in falciparum malaria. The role of PCT in tertian malaria has not previously been investigated.

Patients and methods

PCT serum levels in 37 patients with tertian malaria were analysed. Clinical and laboratory parameters were assessed and statistically correlated both to the initial PCT levels and during the course of the disease.

Results

PCT levels rose for one day after commencing treatment and declined thereafter. However, there was no significant correlation with parasite burden, clinical parameters, laboratory values, or the presence of semi-immunity. Before treatment, the majority of patients showed normal or slightly elevated PCT levels (< 2.5 ng/ml), but PCT was markedly elevated (4.8 – 47 ng/ml) in one third of the population. The two groups did not differ by any other of the assessed parameters. Thus, while the post-treatment course of PCT resembles falciparum malaria, the lack of correlation between disease severity and even high PCT levels in a large proportion of patients is intriguing.

Conclusions

There is a fundamental difference in the relationship of PCT with tertian malaria not seen in other infectious diseases in which elevated PCT levels have been observed. This suggests distinct pathophysiological pathways in malaria.     

Physical polymer matrices based on affinity interactions between peptides and polysaccharides

A rapidly forming polymer matrix with affinity-based controlled release properties was developed based upon interactions between heparin-binding peptides and heparin. Dynamic mechanical testing of 10% (w/v) compositions consisting of a 3:1 molar ratio of poly(ethylene glycol)-co-peptide (approximately 18,000 g/mol) to heparin (approximately 18,000 g/mol) revealed a viscoelastic profile similar to that of concentrated, large molecular weight polymer solutions and melts. In addition, the biopolymer mixtures recovered quickly following thermal denaturation and mechanical insult. These gel-like materials were able to sequester exogenous heparin-binding peptides and could release these peptides over several days at rates dependent on relative heparin affinity. The initial release rates ranged from 3.3% per hour for a peptide with low heparin affinity to 0.025% per hour for a peptide with strong heparin affinity. By altering the affinity of peptides to heparin, a series of peptides can be developed to yield a range of release profiles useful for controlled in vivo delivery of therapeutics.     

ESF Programme on Functional Genomics 1st European Conference: Functional Genomics and Disease 2003

In this report from the 1st European Conference of the European Science Foundation Programme on Functional Genomics, we provide coverage of the high-profile plenary talks and a cross-section of the many presentations in the disease analysis symposia and functional genomics technologies workshops.     

Synthesis and SAR of aminoalkoxy-biaryl-4-carboxamides: novel and selective histamine H3 receptor antagonists

Novel 4'-[(NR1R2-1-yl)]-propoxy-biaryl-4-carboxamides were designed and synthesized. All compounds were tested for affinity at histamine H(3)receptors. Most compounds were highly potent and selective for human and rat H(3) receptors and selected examples such as A-349821 showed functional antagonism of H(3) receptors in vitro and in a mouse dipsogenia model.     

Specific detection of DNA and RNA targets using a novel isothermal nucleic acid amplification assay based on the formation of a three-way junction structure

The formation of DNA three-way junction (3WJ) structures has been utilised to develop a novel isothermal nucleic acid amplification assay (SMART) for the detection of specific DNA or RNA targets. The assay consists of two oligonucleotide probes that hybridise to a specific target sequence and, only then, to each other forming a 3WJ structure. One probe (template for the RNA signal) contains a non-functional single-stranded T7 RNA polymerase promoter sequence. This promoter sequence is made double-stranded (hence functional) by DNA polymerase, allowing T7 RNA polymerase to generate a target-dependent RNA signal which is measured by an enzyme-linked oligosorbent assay (ELOSA). The sequence of the RNA signal is always the same, regardless of the original target sequence. The SMART assay was successfully tested in model systems with several single-stranded synthetic targets, both DNA and RNA. The assay could also detect specific target sequences in both genomic DNA and total RNA from Escherichia coli. It was also possible to generate signal from E.coli samples without prior extraction of nucleic acid, showing that for some targets, sample purification may not be required. The assay is simple to perform and easily adaptable to different targets.     

In vivo regulation of Na/Ca exchanger expression by adrenergic effectors

The Na/Ca exchanger encoded by the NCX1 gene plays an important role in calcium homeostasis in cardiac muscle. We previously identified three in vitro signaling pathways that are of major importance in the regulation of Na/Ca exchanger gene expression in neonatal cardiac myocytes, the protein kinase A (PKA) and protein kinase C (PKC) pathways, and intracellular Ca(2+). To determine whether these pathways are important in vivo, we stimulated the PKA and PKC pathways and examined functional expression of the Na/Ca exchanger in adult rat heart. After a 3- and 7-day treatment, norepinephrine (200 microg x kg(-1) x h(-1)), isoproterenol (150 microg x kg(-1) x h(-1)), and phenylephrine (200 microg x kg(-1) x h(-1)) each stimulated a significant increase in NCX1 mRNA levels (35-85%, P < 0.05). Norepinephrine also stimulated a 35% increase in protein abundance (P < 0.05), a 20% decrease in relaxation duration (P < 0.05), and a 25% reduction in the fluorescence decay constant (P < 0.05) after a 7-day treatment. We conclude that a 7-day treatment of alpha- and beta-adrenergic agonists increases the expression of functional Na/Ca exchangers in adult rat heart.