Allergen hybrids - next generation vaccines for Fagales pollen immunotherapy.

BACKGROUND: Trees belonging to the order of Fagales show a distinct geographical distribution. While alder and birch are endemic in the temperate zones of the Northern Hemisphere, hazel, hornbeam and oak prefer a warmer climate. However, specific immunotherapy of Fagales pollen-allergic patients is mainly performed using birch pollen extracts, thus limiting the success of this intervention in birch-free areas. OBJECTIVES: T cells are considered key players in the modification of an allergic immune response during specific immunotherapy (SIT), therefore we thought to combine linear T cell epitope-containing stretches of the five most important Fagales allergens from birch, hazel, alder, oak and hornbeam resulting in a Fagales pollen hybrid (FPH) molecule applicable for SIT. METHODS: A Fagales pollen hybrid was generated by PCR-based recombination of low IgE-binding allergen epitopes. Moreover, a structural-variant FPH4 was calculated by in silico mutagenesis, rendering the protein unable to adopt the Bet v 1-like fold. Both molecules were produced in Escherichia coli, characterized physico-chemically as well as immunologically, and tested in mouse models of allergic sensitization as well as allergy prophylaxis. RESULTS: Using spectroscopic analyses, both proteins were monomeric, and the secondary structure elements of FPH resemble the ones typical for Bet v 1-like proteins, whereas FPH4 showed increased amounts of unordered structure. Both molecules displayed reduced binding capacities of Bet v 1-specific IgE antibodies. However, in a mouse model, the proteins were able to induce high IgG titres cross-reactive with all parental allergens. Moreover, prophylactic treatment with the hybrid proteins prevented pollen extract-induced allergic lung inflammation in vivo. CONCLUSION: The hybrid molecules showed a more efficient uptake and processing by dendritic cells resulting in a modified T cell response. The proteins had a lower IgE-binding capacity compared with the parental allergens, thus the high safety profile and increased efficacy emphasize clinical application for the treatment of Fagales multi-sensitization.

Allelic loss in the progression of myelodysplastic syndrome.

To elucidate the genetic events that may play an important role in the progression of myelodysplastic syndrome (MDS) to acute myeloid leukemia (AML), we performed allelotype analysis of 24 individuals using matched MDS and AML samples from the same patients. Because the evolution can take years to occur, we used DNAs extracted from archival samples. These samples were analyzed with 79 microsatellite markers, which mapped to each of the autosomal arms except the short arms of the acrocentric chromosomes. Loss of heterozygosity on at least one locus was observed in 18 of the 24 cases (75%) as the disease progressed. Frequent allelic loss in >20% of the informative cases was observed on chromosome arms 6q (31%), 7p (23%), 10p (31%), 11q (27%), 14q (25%), and 20q (23%). Although cytogenetic information was available for many of our cases with allelic loss on 6q, 7p, 10p, 11q, 14q, and 20q, no deletions were observed on these arms. Fractional allelic loss, calculated for each sample as the total number of chromosomal arms lost per total number of arms with information, showed a median value of 0.06 and a mean of 0.15 (range, 0-0.59). No microsatellite instability at more than one marker was found in any of the samples. These results suggest that tumor suppressor genes exist on 6q, 7p, 10p, 11q, 14q, and 20q that have an important role in the evolution of MDS to AML when they are mutated.

In vitro stimulation of erythropoiesis by stem cell factor alone in myelodysplastic syndrome patients with elevated endogenous erythropoietin serum levels.

Anemia remains a therapeutic problem in patients with myelodysplastic syndrome (MDS). In view of the recently reported potential of stem cell factor (SCF) in restoring erythropoiesis in combination with erythropoietin (Epo), we first aimed to define a correlation between SCF serum levels and anemia in MDS. Endogenous SCF levels in 50 MDS patients were determined by using a quantitative sandwich enzyme immunoassay. Broad interindividual variations were observed, but SCF serum levels were in the normal range with no correlation to peripheral blood count. A soft agar culture system was used to further define the role of SCF for stimulation of erythroid growth. Bone marrow mononucleated cells of 20 MDS patients (4 refractory anemia, 5 refractory anemia with excess of blasts, 7 refractory anemia with excess of blasts in transition, and 4 chronic myelomonocytic leukemia) were investigated, and SCF plus Epo was able to stimulate burst-forming unit-erythroid significantly more than SCF or Epo alone independent of French-American-British group. When mononucleated cells from six MDS patients (two refractory anemia, two refractory anemia with excess of blasts, and 2 refractory anemia with excess of blasts in transition) with elevated serum Epo levels were incubated in the presence of SCF and autologous serum, a significant dose-dependent stimulation of burst-forming unit-erythroid number and cells per colony was detected. Erythroid differentiation was further enhanced by adding serum with high colony-stimulating activity obtained from patients with severe aplastic anemia. Our data suggest that in MDS patients with high endogenous Epo serum levels SCF alone might be effective in stimulating erythropoiesis in vivo.

Evaluation of optimal survival of primitive progenitor cells (LTC-IC) from PBPC apheresis products after overnight storage.

Optimal overnight (ON) storage of PBPC aphereses is becoming an increasingly important issue and different options for storing PBPC products exist. The survival of primitive progenitor cells is of major interest, as recent data suggest that these progenitors are not only important for long-term engraftment but also contribute significantly to the early phase of hematopoietic engraftment after myeloablative therapy. We therefore investigated the survival of primitive progenitor cells (ie long-term culture initiating cells, LTC-IC) before (ie within 2 h after finishing the apheresis procedure) and after ON storage lasting 16 to 20 h. In addition, we compared the % of recovery of LTC-IC with that of mature progenitors (ie colony-forming cells, CFC) and with the % viability of the mononuclear cells in the apheresis product. Aliquots of PBPC aphereses products were tested in collection bags at room temperature (RT), in EDTA tubes both at RT or 4 degrees C +/- the addition of autologous plasma (AP; 2.6-fold the apheresis volume) and +/- the possibility of gas exchange. Mean viable cell counts did not show strong differences between the different storage conditions and were poor predictors for the survival of CFC and LTC-IC. At RT (collection bags, EDTA tubes +/- gas exchange) recoveries (% of input) of both, CFC (18%, 18% and 31%) and LTC-IC (10%, 4%, 17%) were low. The addition of AP at RT improved the survival of CFC and LTC-IC to 66% and 38%, respectively. Optimal recoveries for both types of progenitors (CFC: 99%, LTC-IC: 109%) were obtained at 4 degrees C in the presence of AP. In addition, a good correlation between the survival of CFC and LTC-IC was obtained (r = 0.76) suggesting that the analysis of CFC may also allow some conclusions to be drawn on the survival of LTC-IC. Bone Marrow Transplantation (2000) 25, 197-200.