Protection patterns in duck and chicken after homo- or hetero-subtypic reinfections with H5 and H7 low pathogenicity avian influenza viruses: a comparative study.

Avian influenza viruses are circulating continuously in ducks, inducing a mostly asymptomatic infection, while chickens are accidental hosts highly susceptible to respiratory disease. This discrepancy might be due to a different host response to the virus between these two bird species and in particular to a different susceptibility to reinfection. In an attempt to address this question, we analyzed, in ducks and in chickens, the viral load in infected tissues and the humoral immune response after experimental primary and secondary challenge infections with either homologous or heterologous low pathogenicity avian influenza viruses (LPAIV). Following homologous reinfection, ducks were only partially protected against viral shedding in the lower intestine in conjunction with a moderate antibody response, whereas chickens were totally protected against viral shedding in the upper respiratory airways and developed a stronger antibody response. On the contrary, heterologous reinfection was not followed by a reduced viral excretion in the upper airways of chickens, while ducks were still partially protected from intestinal excretion of the virus, with no correlation to the antibody response. Our comparative study provides a comprehensive demonstration of the variation of viral tropism and control of the host humoral response to LPAIV between two different bird species with different degrees of susceptibility to avian influenza.

DNA vaccination induces WT1-specific T-cell responses with potential clinical relevance.

The Wilms tumor antigen, WT1, is associated with several human cancers, including leukemia. We evaluated WT1 as an immunotherapeutic target using our proven DNA fusion vaccine design, p.DOM-peptide, encoding a minimal tumor-derived major histocompatibility complex (MHC) class I-binding epitope downstream of a foreign sequence of tetanus toxin. Three p.DOM-peptide vaccines, each encoding a different WT1-derived, HLA-A2-restricted epitope, induced cytotoxic T lymphocytes (CTLs) in humanized transgenic mice expressing chimeric HLA-A2, without affecting hematopoietic stem cells. Mouse CTLs killed human leukemia cells in vitro, indicating peptide processing/presentation. Low numbers of T cells specific for these epitopes have been described in cancer patients. Expanded human T cells specific for each epitope were lytic in vitro. Focusing on human WT1(37-45)-specific cells, the most avid of the murine responses, we demonstrated lysis of primary leukemias, underscoring their clinical relevance. Finally, we showed that these human CTL kill target cells transfected with the relevant p.DOM-peptide DNA vaccine, confirming that WT1-derived epitopes are presented to T cells similarly by tumors and following DNA vaccination. Together, these data link mouse and human studies to suggest that rationally designed DNA vaccines encoding WT1-derived epitopes, particularly WT1(37-45), have the potential to induce/expand functional tumor-specific cytotoxic responses in cancer patients.

[F-18]-Fluoro-2-deoxy-D: -glucose positron emission tomography as a tool for early detection of immunotherapy response in a murine B cell lymphoma model.

[F-18]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) is a non-invasive imaging technique which has recently been validated for the assessment of therapy response in patients with aggressive non-Hodgkin's lymphoma. Our objective was to determine its value for the evaluation of immunotherapy efficacy in immunocompetent Balb/c mice injected with the A20 syngeneic B lymphoma cell line. The high level of in vitro FDG uptake by A20 cells validated the model for further imaging studies. When injected intravenously, the tumour developed as nodular lesions mostly in liver and spleen, thus mimicking the natural course of an aggressive human lymphoma. FDG-PET provided three-dimensional images of tumour extension including non-palpable lesions, in good correlation with ex vivo macroscopic examination. When mice were pre-immunized with an A20 cell lysate in adjuvant before tumour challenge, their significantly longer survival, compared to control mice, were associated with a lower incidence of lymphoma visualized by PET at different time points. Estimation of tumour growth and metabolism using the calculated tumour volumes and maximum standardized uptake values, respectively, also demonstrated delayed lymphoma development and lower activity in the vaccinated mice. Thus, FDG-PET is a sensitive tool relevant for early detection and follow-up of internal tumours, allowing discrimination between treated and non-treated small animal cohorts without invasive intervention.

Analysis of the intraclonal diversity of HLA-A0201-restricted T lymphocyte epitopes in follicular lymphoma idiotype.

Lymphoma-derived immunoglobulin idiotype (Id) is a tumour-specific antigen used for antitumour vaccination in follicular lymphoma (FL). However, FL Ids are subject to hypermutation and subclones may escape antitumour cytotoxic T-cell response. To investigate the intraclonal epitope diversity, we sequenced the FL heavy chain gene (consensus Id gene) and subclones of 24 patients. The derived polypeptide sequences were analysed by bioinformatics for human leucocyte antigen (HLA)-A0201-restricted epitope prediction. Epitopes were classified according to BIMAS and SYFPEITHI scores. Surprisingly in these highly mutated polypeptides, the epitopes concentrated in short hotspots in the conserved framework regions (FRs), both in HLA-A0201(+) and HLA-A0201(-) patients. Similar hotspots have been observed by others in chronic lymphocytic leukaemia Ids which in contrast to FL have low mutation frequency. FR3 amino acids 78-88 displayed the best-score epitopes in Ids containing a VH3-family segment, the most represented in FL Ids. Such VH3-FR3(78-88) epitopes were previously demonstrated as immunogenic. Modifications of the epitope pattern in subclones of HLA-A0201(+) patients were generally absent from high-score peptides, including VH3-FR3(78-88) epitopes (83% unmodified). Therefore, no tendency for loss of HLA-A0201-restricted epitopes was evidenced and, given their limited intraclonal diversity, VH3-FR3(78-88) epitopes may provide a useful target for the induction of cytotoxic response in Id-vaccinated FL patients.