ALBERT

Description: Invasive fungal infections (IFI), in particular infections due to Aspergillus spp and Candida spp, still pose considerable problems in patients undergoing allogeneic stem cell transplantation (SCT). Despite the availability of new antifungal agents, morbidity and mortality of IFI are still unacceptable high. Although neutropenia is known as the single most important risk factor for IFI, there is a growing body of evidence that T cells play a major role in the defense against fungi. Therefore, adoptive immunotherapy with T cells against Candida spp. might be an interesting therapeutic option in patients undergoing allogeneic SCT. After overnight incubation of 1×108 peripheral blood mononuclear cells from 4 healthy individuals with cellular extracts of C.albicans, activated T cells were selected using the IFN-γ secretion-assay (Miltenyi Biotec, Bergisch Gladbach, Germany). After 14 days of culture, T cell clones were generated by limiting dilution and incubated for another 14 days. The median number of cells obtained was 2.6×107 (range, 0.85–5.75×107). Flow cytometry revealed a highly homogenous population of CD3+CD4+ cells (97.2% ± 2.6; n=6), of which an average of 8.6% (range, 4.8–58.2%) produced IFN-gamma on re-stimulation with C.albicans antigens, as assessed by intracellular cytokine staining assay. 20.5% (range, 5.8–72.4%) of the generated cells produced TNF-alpha, whereas no significant number of cells produced TH2 cytokines such as IL-4 and IL-10, indicating that the generated T cell clones were TH1 cells. The percentage of IFN-gamma producing T cells was significant upon stimulation with C.albicans and C.tropicalis, whereas less than 1% of cells produced IFN-gamma upon stimulation with antigens of other yeasts such as C.glabrata, Debaryomyces hansenii and Kluyveromyces lactis and molds such as A.fumigatus, Penicillium chrysogenum and Alternaria alternata. Compared to CD4+ T cells of the original fraction, the isolated and expanded anti-Candida T cells showed reduced alloreactivity, as assessed by means of CSFE. In addition, a strong proliferation of the generated anti-Candida T cells was seen after re-stimulation with C.albicans antigens. The potency of the generated T-cells to damage C.albicans was evaluated using the XTT assay. Compared to polymorphonucelar cells (PMNs), APCs and T-cells alone or to the combination of PMNs with T cells or APCs, respectively, the combination of PMNs, APCs and T-cells showed highest fungal damage (n=4). In conclusion, our data suggest that the isolation and expansion of anti-Candida T cells is possible and feasible. The generated T cells show low alloreactivity in vitro and increase the antimycotic potential of phagocytes. Thus, antimycotic T cells might become an important tool in the prophylaxis and therapy of IFI in patients after allogeneic SCT.

Description: Invasive aspergillosis is still a life-threatening complication, in particular in patients after allogeneic hematopoietic stem cell transplantation (HSCT). Whereas prolonged neutropenia is a well established risk factor for invasive fungal disease, there is a growing body of evidence that T-cells also play an important role in the immunological response to Aspergillus species. Since invasive aspergillosis often occurs during the phase of postengraftment, which is characterized by impaired cell-mediated immunity, Aspergillus-specific T-cells could be a potential therapeutic target in these patients. We therefore analyzed in a first step the response of T-cells to several potential antigens of Aspergillus fumigatus by means of 3H-thymidine incorporation assay. In order to generate Aspergillus-specific T-cells, the antigens with the highest proliferation indices (EC-SAB and 90 kDa catalase) were used to stimulate 1.0 x 108 mononuclear cells from healthy donors. The activated T-cells were isolated on the following day using the IFN-γ secretion assay (Miltenyi Biotec, Germany) and then expanded for 14 days. Intracellular cytokine analysis of EC-SAB generated cell lines (n=7) revealed a significant IFN-γ secretion by 13.6%±2.3 of CD4+ cells (seven out of seven tested cell lines) and an Aspergillus-specific IL-2 secretion by 6.5%±1.9 of CD4+ cells (three out of three tested cell lines), which supports the TH1 response of the generated cells to Aspergillus antigen. In contrast to EC-SAB generated T-cell populations, all three cell lines which were generated with 90 kDa catalase were not informative. Further analysis showed that restimulation with EC-SAB induced a strong proliferation of EC-SAB generated T-cell populations (all three populations tested), whereas alloreactivity was unaffected. The number of these cells could be expanded within 14 days up to 20fold using OKT-3, IL-2 and feeder cells. Currently, we investigate the impact of these Aspergillus-specific cell populations in the defense to different species of Aspergillus. Our preliminary results suggest that Aspergillus-specific T-cells could be an interesting option in prophylaxis and therapy of invasive aspergillosis in patients undergoing HSCT.

Description: Invasive aspergillosis remains a serious complication in patients undergoing allogeneic stem cell transplantation (SCT). Since it became clear that lymphocytes provide a critical secondary defense against fungi, adoptive transfer of functionally active anti-Aspergillus T cells might be an option to restore adaptive immune effector mechanisms. Using the interferon (IFN)-γ secretion assay, we isolated human activated T cells upon stimulation with a cellular extract of Aspergillus fumigatus. Culturing this cell population for 14 days, we obtained an average of 1.1 × 107 cells from a single 100-mL blood draw in 7 of 7 healthy individuals. Within another 14 days, these cells were expanded to an average number of 2.0 × 108 T-helper 1 (TH1) cells secreting IFN-γ on stimulation with Aspergillus antigens. Testing various fungal antigen extracts, similar proportions of IFN-γ-producing CD3+/CD4+ cells were obtained upon activation with antigen extracts of A fumigatus, A flavus, A niger, and Penicillium chrysogenum, whereas no significant IFN-γ production was observed upon activation with antigen extracts of Alternaria alternata and Candida albicans. In addition, generated T cells were able to induce damage to A fumigatus hyphae, and significantly increased hyphal damage induced by human neutrophils. CD4+ T-cell-mediated alloreactivity of generated anti-Aspergillus T cells was clearly reduced compared with that of the original cell population. In conclusion, we present a simple and feasible strategy for rapid generation of a high number of functional active T cells against Aspergillus from a single blood draw. Our data suggest that functionally active T cells against Aspergillus could be a promising treatment option for patients undergoing allogeneic SCT. (Blood. 2006;107: 2562-2569)

Description: Relapse is the leading cause of treatment failure after allogeneic SCT of Hodgkin Disease (HD). As Ebstein-Barr infection (EBV) is associated with 60% of all HD cases, adoptive immunotherapy with donor derived EBV-specific T-cells lines has resulted in disease control of allogeneic SCT. Potential targets for the adoptively transferred T-cells are the type II latency protein LMP-1 and LMP-2a, which are both homogenously expressed by HD cells. In healthy individuals, both LMP-1 and LMP-2a elicits subdominant CD8+ T-cell responses with frequencies of less than 1:10000. LMP-1 and LMP-2a specific T-cells from 1x108 PBMC derived from HLA A*0201+healthy donors were stimulated with the HLA A*0201 LMP1-epitopes YLLEMLWRL and YLGQNWWTL and the HLA A*0201 LMP-2a epitope CLGGLLTM. Activated T-cells were selected by the cytokine secretion assay and expanded for 10 days. In 85% of donors 1.7 x106 (range 0.7 –4.5 x106; n=13) LMP-1 or LMP-2a specific CD8+ T-cell could be generated with an average purity of 83% as determined by tetramer staining. LMP1- and LMP2a-specific CD8+ T-cells were then expanded 3000 x in 14 d by the rapid expansion protocol and evaluated functionally for cytokine production and specific lysis. Both LMP-1 and LMP-2a specific CD8+ T-cells retained specific cytokine production if stimulated with peptide pulsed targets, efficiently lysed peptid pulsed targets. Surprisingly, if LMP-1 was presented endogenously by EBV positive targets or by targets cells transduced with LMP-1, no cytokine production or specific lysis was detected despite protein expression of LMP-1 in all targets. In contrast, IFN-γ production could be readily detected in LMP-2a-specific CD8+ T-cells after stimulation with target cells processing endogenously the LMP-2a antigen as well as specific lysis of EBV positive target cells. Furthermore, LMP2a specific CD8+ demostrated also specific lyse of Hodgkin-cells expressing the LMP2a (30:1 E/T ratio; 29,3%) where as LMP-1-specific CD8+ T-cells could not lyse HD-cells. In summary, LMP-1 and LMP-2a specific T-cells, although present at undectable levels in healthy donors, can be readily selected and expanded to up to 6x109 antigen-specific T-cells in less than 4 weeks starting from 1x108 PBMC. Based on this data, adoptive immunotherapy of relapsed EBV positive HD after allogeneic SCT should be preferentially performed with LMP-2a specific CD8+ T-cells rather than with LMP-1 specific CD8+ T-cells.

Description: Invasive aspergillosis (IA) remains a major cause of morbidity and mortality in patients with hematological malignancies, in particular in patients who have undergone allogeneic hematopoietic stem cell transplantation (SCT). There is a growing body of evidence that T-cells play an important role in the immunological response to Aspergillus fumigatus. Using the Aspergillus fumigatus antigen extract EC SAB and the IFN-γ secretion assay (Miltenyi Biotec, Germany), we generated Aspergillus fumigatus specific T-cell clones by limiting dilution (n=4). Flow cytometry revealed a cell population of CD3+/CD4+ cells (mean±SEM, 98.2±1.2%). Functional assessment by ICC revealed that an average of 8.7% of these cells (range, 6.6%–18.5%) specifically secreted IFN-γ on stimulation with EC SAB, which supports the TH1 response of the generated cells to Aspergillus fumigatus antigens. The antigenic components of EC SAB are one or more proteins, since the addition of proteinase completely suppressed the stimulating effect of this preparation. The percentage of IFN-γ producing CD3+/CD4+ cells was less than 1% upon activation with antigen extracts from Aspergillus flavus, Aspergillus niger, Alternaria alternata, Mucor racemosus, Penicillium notatum and Candida albicans, indicating that the generated T-cell clones are specific for Aspergillus fumigatus. A strong proliferation of the generated Aspergillus fumigatus specific T-cells was seen after re-stimulation with EC SAB, whereas alloreactivity was reduced compared to CD4+ T-cells of the original fraction. Hyphal damage of Aspergillus fumigatus was assessed by means of an XTT assay. Polymorphonuclear leukocytes (PMNs) showed a similar hyphal damage when tested alone (mean±SEM, 14.2±2.1%), in combination with antigen presenting cells (APCs) (15.1±1.4%), or in combination with Aspergillus fumigatus specific T-cells (15.0±2.0%). A comparable hyphal damage was seen when Aspergillus fumigatus specific T-cells were co-incubated with APCs (14.2±1.7%). In contrast, the combination of APCs and Aspergillus fumigatus specific T-cells with PMNs resulted in a significantly higher hyphal damage compared to all other settings (23.3±2.8%; P