Human herpesvirus 6B (HHV-6B) is the causative agent of the common childhood febrile illness, exanthema subitum. The virus is predominantly regarded as a T-cell tropic virus, although in reality it has the ability to infect a wide variety of cell types including monocytes, macrophages and dendritic cells (DC). Although DC are important immune regulators, the modulating effects of HHV-6B on DC are controversial. Here, we examine the phenotypic and functional consequences of HHV-6B infection of DC. The addition of HHV-6B to immature DC led to expression of the nuclear viral p41 protein and cell surface expression of the viral glycoprotein gp60/110 consistent with HHV-6B infection. Nevertheless, HHV-6B did not induce noticeable cytopathogenic effects or cell death in infected DC. Importantly, HHV-6B infection induced a partial phenotypic maturation of immature DC as demonstrated by a substantial increase in the expression of HLA-DR, CD86 and CD40, whereas only a minor increase in CD80 and CD83 was observed. This phenotypic maturation was, however, not followed by functional maturation, because HHV-6B infection did not induce IL-10 and IL-12p70 production in immature DC. However, infected DC were still able to react to bacteria-derived stimuli such as lipopolysaccaharide by an even more pronounced production of IL-10 and IL-12p70 when compared to that of uninfected DC.

Accumulation of T cells at the tumor is essential in cancer immunotherapy based on adoptive transfer of tumor-specific T cells. To gain further insight into the accumulation process and to evaluate the effect of using different routes of cell transfer, we investigated the accumulation of ovalbumin-specific CD8+ T cells (OT-I) injected either intravenously (IV) or intraperitoneally (IP) into mice carrying a subcutaneous tumor of the ovalbumin-expressing melanoma cell line B16-OVA. Maximal accumulation of the adoptively transferred cells in tumor tissue was observed 5 days after injection, irrespective of the injection route. The route of injection affected neither the total number of adoptively transferred cells found in tumor tissue nor the kinetics of this accumulation. In the spleen, however, the accumulation of adoptively transferred cells was clearly dependent on the injection route. IP injections resulted in a large number of adoptively transferred cells in the spleen on all days analyzed. In comparison, IV injection resulted in significantly fewer adoptively transferred cells in the spleen, and this number decreased over time. The route of injection affected neither the activation status of the adoptively transferred T cells that accumulated at the tumor site, nor the ability of these cells to control tumor growth. Two cell populations, SIINFEKL-tetramerLow(TetLow)CD69+CD25+ and TetHighCD69−CD25−, were present in tumor samples, whereas only TetHighCD69−CD25− cells accumulated in the spleen. In tumors, IV injection resulted in a higher fraction of adoptively transferred cells with an activated phenotype (TetLowCD69+CD25+) compared with IP injection.

In a mouse model, we demonstrate how to obtain a direct, unbiased estimate of the total number of adoptively transferred cells in a variety of organs at different time points. The estimate is obtained by a straightforward method based on the optical fractionator principle. Specifically, non-stimulated C57BL/6J mouse splenocytes were labelled with carboxyfluorescein diacetate succinimidyl ester (CFSE) and adoptively transferred to normal C57BL/6J mice by intravenous injection. The total number of CFSE-positive cells was subsequently determined in lung, spleen, liver, kidney, and inguinal lymph node at six different time points following adoptive transfer (from 60 s to 1 week), providing a quantitative estimate of the organ distribution of the transferred cells over time. These estimates were obtained by microscopy of uniform samples of thick sections from the respective organs. Importantly, the samples were chosen and prepared in accordance with the optical fractionator principle. We demonstrate that the method is simple, precise, and well suited for quantitative immunological studies.

s for the 19th Annual Scientific Meeting of the International Society for Biological Therapy of Cancer, San Francisco, California, November 4-7, 2004: Imaging

Tracking adoptively transferred antigen-specific T lymphocytes is an important prerequisite for devising better protocols for cellular therapy. To this end we have developed a highly sensitive method for “in situ” visualization of labelled lymphocytes in vivo by combined PET and magnetic resonance imaging (MRI) to monitor the distribution of adoptively transferred tumour-specific T cells in a mouse model system. Moreover, quantitation of the adoptively transferred cells in tumor was performed by flow cytometry. C57BL/6J mice carrying subcutaneous tumours of the ovalbumin (OVA)-expressing malignant melanoma cell line B16-OVA were adoptively transferred with OVA-specific CD8+ T cells labelled with 124IdU. Five days after transfer of T cells, mice were killed and subjected to PET and MR imaging. Using a newly developed method for co-registration of the two image modalities, the anatomical localisation of the transferred cells was visualised and the amount of radioactivity in various anatomical locations very accurately determined. For quantitation of tumor infiltrating non-labelled OVA-specific CD8+ T cells by flow cytometry (using AbsoluteCount Beads), tumors were removed from mice day 1 until day 8 following adoptive transfer (6 mice/group) and prepared for single cell suspension before labeled with anti-CD8-FITC and SIINFEKL-Tetramer-PE. Results showed a clear tumor localization of the adoptively transferred OVA-specific T cells in the tumours. In two independent experiments comprising 12 and 13 evaluable mice, respectively, we found a mean value of 0.909 +/− 0.468 Bq and 0.926 +/− 0.553 Bq in the tumours, and only 0.182 +/− 0.479 Bq and 0.026 +/− 0.480 Bq in the corresponding contralateral control volumes. The difference in activity between the tumour regions and the control regions was statistically highly significant with 2p-values of 0.002 and 0.006 for the two experiments. Using flow cytometry it was shown that the number of OVA specific T lymphocytes accumulating in tumor gradually increased until day 5 after transfer when an average of 3.3 million SIINFEKL-specific cells per gram tumor tissue was found. From day 5 until day 8 the number of SIINFEKL-specific cells per gram tumor tissue fluctuated at a fairly constant level. This method presented for tracking adoptively transfered tumor specific T lymphocytes represent a significant advancement for studies of adoptively transferred specific T cells, and could potentially be developed for diagnostic purposes. Moreover, since these studies show that tumor-specific T cells home to subcutaneous tumours in substantial numbers, we suggest that these migrating cells could be employed in a new form of therapy as carriers of toxic substances to tumors.

s for the 19th Annual Scientific Meeting of the International Society for Biological Therapy of Cancer, San Francisco, California, November 4-7, 2004: Adoptive Immunotherapy

Flow cytometric measurement of intracellular cytokines in T cells exposed to antigen is a widely used method for quantification of an antigen-specific T-cell response. As the frequency of antigen-specific T cells is often very low, any improvement in signal to noise ratio is of great importance. Thus, in this study, the ability of antigen-pulsed dendritic cells (DCs) to increase the number of antigen-specific, interferon-gamma (IFN-gamma)-producing CD4+ T cells measurable both in fresh peripheral blood and in reconstituted frozen blood mononuclear cell (MNC) samples was evaluated. Cytomegalovirus (CMV) was used as antigen in a 10 h assay, using cells from both CMV-seropositive and -seronegative donors. When reconstituted frozen samples were analysed, the general response towards CMV lysate in CMV-seropositive donors was 23-86% lower compared to the corresponding fresh blood samples. Antigen-pulsed DCs could not improve the sensitivity of the intracellular cytokine-detection assay when fresh peripheral blood samples were used. Interestingly, however, the addition of CMV lysate-pulsed DCs to cryopreserved MNC samples substantially increased the frequency of specifically induced IFN-gamma-producing cells to a level comparable to the frequency found in the corresponding fresh blood samples.

A method for precise and sensitive organ specific quantification of 124I (124IdUR) activities in small animals has been developed. The method is based upon high precision co-registration between PET and MR imagery, utilizing an innovative mouse fixation system with external point sources visible in both modalities. The methodology is generic, and thus can easily be extended to other types of small animal studies. The methodology comprises PET/MR rigid co-registration utilising external fiducial markers, measurement of activities within small 3D volumes manually drawn in MR data and extracted from the co-aligned PET data, and subsequently corrected for Partial Volume Effect.

In our laboratory, we have developed a database system, which we believe is of immediate interest to the general scientific community. The database represents a computer‐based replacement for the laboratory notebooks used in the majority of research laboratories worldwide. In addition, the database provides an effective tool for organizing and managing laboratory information at all levels, spanning from managing and revising standard operating procedures and producing documentation of research activities to keeping track of data and conclusions. Using the commercially available database toolkit software FileMaker Pro, we have developed a relational database solution for management of laboratory information. The system consists of a hierarchy of five interrelated databases, each pertaining to a separate type of information, namely, overall project information, information relating to individual experiment setups, documentation of daily research activity, generated data and descriptions of standard operating procedures. Like other databases, each individual database consists of a number of records, each comprised of a set of fields in which information is entered. In each record, a certain field is reserved to specify the relation of the record to a record in another database at a higher level. Thus, the database is essentially five databases linked by a hierarchy of one‐to‐many relations, organizing information in a folder‐like structure. Importantly, the database system allows multiple users to access and edit records simultaneously, and the data entered in one database immediately becomes accessible through the other databases. The limitations of laboratory notebooks are apparent when looking for information, which is dispersed throughout one or more notebooks, or possibly on loose sheets of paper or printouts ‘somewhere’. The often complicated process of gathering laboratory data or results when writing grant applications or research papers is made considerably easier with the database system. Thus, the database solution presented should be broadly attractive to researchers, irrespective of their scientific discipline.

The aim of the present study was to characterise the local immune response in a chemically induced colon tumour model in the rat. Elucidating the character of the immune reaction may contribute to optimizing immunotherapeutic regimens for colon carcinoma in this model. Colon cancer was induced by four weekly subcutaneous azoxymethane injections in inbred rats of the BDIX/OrlIco strain in two separate studies. Azoxymethane‐induced tumours show many similarities to spontaneously occurring human colon carcinomas with respect to histopathological appearance. In our studies, the overall inflammatory reaction of the submucosa below the tumour was evaluated in haematoxylin‐eosin‐stained tissue sections. Phenotypic characterization of leukocyte infiltration in the tumour tissue was performed by immunohistochemical staining using antibodies detecting various leukocyte subsets, i.e. T cells, natural killer cells, macrophages/monocytes, and dendritic cells. The results showed that the azoxymethane‐induced colon tumours were strongly infiltrated by macrophages. Furthermore, the tumours showed a moderate degree of infiltrating CD4‐positive cells. Very few natural killer, CD8‐positive T cells and dendritic cells (identified by the OX62 antibody) were seen in the tumour tissue. Virtually no CD25‐positive cells were found. This immunohistochemical characterisation of the tumour‐infiltrating immune response in this rat model could form the basis for studies aimed at developing new immunotherapeutic regimens for human colon cancer.

Typically autologous dendritic cells (DCs) intended for vaccination are generated from bone marrow derived stem cells or blood monocytes, loaded with antigen and introduced into the organism. However, addition of serum to DC culture medium is often necessary. Thus, serum proteins will be taken up and presented by the DCs together with other antigens. If heterologous serum is used, some of the serum proteins might be antigenic and thus induce a strong immune response when introduced in the recipient. We used the murine model of malignant melanoma, B16, to investigate the consequences of addition of fetal calf serum (FCS) to the medium for culturing murine DCs. The results showed that vaccination of mice with DCs cultured in vitro in the presence of FCS but in the absence of extraneous tumour antigens, protected the mice from challenge with B16 tumour cells similarly cultured in FCS. This protection could not be elicited by vaccination with FCS alone. Interestingly, the protective effect of DC vaccination was abolished when the challenging B16 tumour cells were free of serum proteins. Thus, these results show that DCs grown in the presence of FCS are able to induce immunity, which may be mistaken to be tumour immunity.

Circulating malignant cells in peripheral blood are thought to be precursors and surrogate markers of distant metastases and hence markers of a poor clinical outcome. In this study, we used the detection of MART-1 and tyrosinase (TYR) mRNA with a quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay to identify circulating melanoma cells. Blood samples were obtained from 35 patients with metastatic melanoma before, during and after treatment with interleukin-2, interferon-alpha and cisplatin. In addition, MART-1 and TYR protein was identified by immunohistochemistry in consecutive biopsies from 15 of the patients. Analysis of three daily blood samples for 3 days demonstrated that four out of 11 patients examined were negative for both markers on all occasions, and two patients were positive for both markers on all occasions but one. The remaining five patients showed sporadic low positive results for one or the other of the two markers. By comparing the immunohistochemistry results from consecutive biopsies with the RT-PCR results, we demonstrated that patients with MART-1 and TYR protein in their tumour cells had circulating MART-1 and TYR mRNA in 77% and 54% of the cases, respectively. During treatment, the majority of patients who were positive for MART-1 and TYR mRNA converted to being negative. However, these conversions did not significantly correlate with objective response. The presence of TYR mRNA in one of the first two samples showed a trend towards being an independent prognostic factor for poor survival.

The circulatory pattern of IL-2 activated natural killer (A-NK) cells was studied in C57BL/6 mice bearing 10 day-old pulmonary and subcutaneous (s.c.) metastases of the B16 melanoma in order to evaluate the roles of the concentration of A-NK cells in the blood and of tumor blood flow on accumulation of A-NK cells in tumors. Kinetic studies of the presence of A-NK cells in peripheral blood after adoptive transfer revealed that these cells rapidly disappear from the blood. Via intravital microscopy of animals with exposed lung tissue, we have shown that the vast majority of transferred A-NK cells become efficiently arrested within the lung microcirculation at their first encounter with this organ, thereby explaining the fast disappearance of the cells from the bloodstream. Despite the low number of A-NK cells circulating in the blood, systemically injected A-NK cells (20 million per mouse) localized significantly (70-80 million cells/g) into most pulmonary metastases within 8-16 hours. In contrast, very few A-NK cells (< 0.2 million cells/g) were found in the s.c. metastases. Based on measurements of tumor blood flow (showing a classic inverse relationship between tumor size and tumor blood flow) and the blood concentration of A-NK cells, we estimated the highest intratumoral density of A-NK cells that theoretically can be generated by A-NK cells transported to the tumor by way of the blood. In s.c. tumors, the observed density of A-NK cells was at all times lower (10-50 fold) than the estimated density, indicating that only a few percent of the A-NK cells arriving at these tumors become retained in them. In contrast, the observed density of A-NK cells in pulmonary metastases was at all times higher (2-3 fold) than the estimated density. This finding indicates that A-NK cells might not reach the pulmonary metastases solely by way of the blood stream. In conclusion, i.v. injected A-NK cells become immediately entrapped in the lungs and, consequently, circulate poorly. While lung metastases become significantly infiltrated by i.v. injected A-NK cells, metastases in organs down-stream from the lungs become poorly infiltrated. We hypothesize that only a part of the A-NK cells found in lung metastases 8-16 hours following injection reach these metastases by way of the blood-vascular system. They might also migrate into the metastases from the surrounding normal lung tissue.

The therapeutic potential of dendritic cells loaded with tumour antigens for the induction of effective immune responses against cancer is currently being tested in numerous clinical trials. In most cases, the dendritic cells are generated in vitro from peripheral blood monocytes. Many aspects of dendritic cell-based vaccination have not yet been examined in detail, and homologous mouse model systems may prove very valuable for optimizing clinical procedures. In the murine system, however, dendritic cells are usually isolated from either lymphoid tissues or bone marrow cultures. To date, murine monocyte-derived dendritic cells have been described only sporadically. Here, we describe a culture system for the generation of murine dendritic cells from adherent peripheral blood mononuclear cells by culturing in the presence of granulocyte-macrophage colony stimulating factor and interleukin-4. After 7 days of culture the nonadherent cells were harvested from the cultures. Most of these cells exhibited well-accepted characteristics of mature dendritic cells (e.g. veiled appearance, high expression of major histocompatibility complex class II and CD86) and stimulated vigorous proliferation of allogeneic T cells in a primary mixed leucocyte reaction following stimulation with bacterial lipopolysaccharide. Interestingly, staining the cells for expression of the putative antigen-uptake receptor DEC-205 revealed a distinct bimodal distribution.

The dendritic cell (DC) is a professional antigen-presenting cell of central importance in immunity. In this paper, we examined DCs generated by 11-day culture of bone-marrow cells from the four mouse strains C57BL/6J, BALB/cA, C3H/HeN and B10.PL-H2(u) (73NS)/Sn with respect to cell yield as well as surface-marker phenotype and morphology. We also investigated the phenotypic changes and the T-cell stimulatory activity of the DCs induced by bacterial lipopolysaccharide (LPS). Morphologically, we observed low levels (5-10%) of granulocyte contamination of the cultures after a culture period of 11 days. Considerable strain-specific differences were found in the expression levels of the surface markers in addition to the differences in the ratio of the immature to mature DCs in the cultures that were not stimulated with LPS. Furthermore, we found that LPS strongly induces maturation of DCs in all strains investigated with the exception of the B10.PL strain.

Dendritic cells (DCs) represent a group of antigen-presenting leukocytes which are very effective in activating resting T-cells. DCs are present in almost all tissues of the body, but they are generally difficult to isolate. The study of human DCs has recently become greatly facilitated due to the advent of methods for isolation and in vivo generation of DCs from blood. Experiments in animal models have shown that DCs loaded with tumour antigens may induce effective immune responses against cancer. Now the potential of vaccination with tumour antigens presented on DCs is being evaluated in cancer patients. Preliminary clinical studies have shown encouraging results.

In murine models, therapeutic efficacy of adoptive immunotherapy (AIT) of cancer with lymphokine activated killer (LAK) cells is seen only when applied together with substantial doses of interleukin-2 (IL-2), probably because this cytokine is imperative for both motility and viability of the LAK cells. We wanted to investigate whether IL-2 in addition mediates an immunostimulatory activation and expansion of endogenous effector cells contributing to tumor regression. Using an immunoperoxidase technique, we have been able to longitudinally analyze the accumulation of tumor infiltrating lymphocytes expressing the pan-T cell/activated lymphocyte phenotype (Thy1.2), the natural killer (NK) cell phenotype (AsGM,) as well as the cytotoxic T (CD8) cell phenotype within experimental established B16 pulmonary melanoma metastases in C57BL/6 mice during the first 48 h after high dose IL-2 monotherapy. Whereas a substantial and selective infiltration of AsGM1+ lymphocytes in tumor tissue was seen (262 and 937 cells per sq.mm malignant tissue at 0 and 48 h, respectively), only a minor increase in accumulation of CD8+ cells was seen (106 and 171 cells per sq.mm tumor tissue at 0 and 48 h, respectively). The addition of adoptive transfer with lymphokine-activated adherent NK (A-NK) cells to the high-dose IL-2 treatment resulted in more than a 1.5 fold increase in infiltrating AsGM1+ cells compared to IL-2 therapy alone (1520 compared to 937 AsGM1+ cells per sq.mm malignant tissue). No substantial accumulation of CD8+ cells was observed in this setting either. In contrast, the treatment with high dose IL-2 together with adoptive transfer of mitogen-stimulated, lymphokine-activated T killer (T-LAK) cells increased the infiltration of CD8+ cells 10-fold compared to IL-2 monotherapy (2078 compared to 171 CD8+ cells per sq.mm malignant tissue, respectively). Interestingly, infiltration of both endogenous and exogenous cells continued over time, since the effector-to-tumor cell ratio in metastatic tissue dramatically increased from 1:8 and 1:6 at 16 h to 1:3 and 1:2 at 48 h after adoptive transfer of A-NK and T-LAK cells, respectively. These data underline the longevity of LAK cells in vivo and highlight the importance of IL-2 treatment in recruiting endogenous immune cells to tumor areas.