Multimodal pooled Perturb-CITE-seq screens in patient models define mechanisms of cancer immune evasion

Resistance to immune checkpoint inhibitors (ICIs) is a key challenge in cancer therapy. To elucidate underlying mechanisms, we developed Perturb-CITE-sequencing (Perturb-CITE-seq), enabling pooled clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 perturbations with single-cell transcriptome and protein readouts. In patient-derived melanoma cells and autologous tumor-infiltrating lymphocyte (TIL) co-cultures, we profiled transcriptomes and 20 proteins in ~218,000 cells under ~750 perturbations associated with cancer cell-intrinsic ICI resistance (ICR). We recover known mechanisms of resistance, including defects in the interferon-γ (IFN-γ)-JAK/STAT and antigen-presentation pathways in RNA, protein and perturbation space, and new ones, including loss/downregulation of CD58. Loss of CD58 conferred immune evasion in multiple co-culture models and was downregulated in tumors of melanoma patients with ICR. CD58 protein expression was not induced by IFN-γ signaling, and CD58 loss conferred immune evasion without compromising major histocompatibility complex (MHC) expression, suggesting that it acts orthogonally to known mechanisms of ICR. This work provides a framework for the deciphering of complex mechanisms by large-scale perturbation screens with multimodal, single-cell readouts, and discovers potentially clinically relevant mechanisms of immune evasion.

[THE LEVEL OF EXPRESSION OF MOLECULES OF ADHESION ON LYMPHOCYTES DEPENDING ON AMOUNT OF THEIR CYTOPLASM]

The lymphocytes are true immunocytes specialized in discerning antigen in organism. Their behavior in blood is regulated by several classes of adhesion proteins, including selectin, integrin, immunoglobulin. In healthy humans there is no data concerning level of expression of adhesion molecules on lymphocytes depending on size of their cytoplasm. The study was carried out to determine level of expression of adhesion molecules of lymphocytes depending on size of their cytoplasm. The flow cytometer was applied to determine in venous blood level of expression of adhesion molecules in 50 individuals (22 males and 28 females) aged from 20 to 60 years and having no chronic pathology in anamnesis. The analysis of lymphocytogram permitted to differentiate lymphocytes according volume of cell considering size of cytoplasm: small lymphocytes- up to 8 mkm; medium - from 8 to 12 mkm; large - more than 12 mkm. In males a tendency was established concerning decreasing of concentration of lymphocytes with expressed molecule of L-selectin. The absence was detected concerning gender differences in level of lymphocytes with receptor LFA-1 and also lymphocytes with molecule ICAM-1. In males concentration of lymphocytes with receptor LFA-3 was higher than in females but only as a tendency. The lower level of expression of molecule PECAM-1 in males was observed. The correlation analysis between level of expresion of adhesion molecules and concentration of lymphocytes differing in size of cytoplasm, demonstrated that at increasing of size of cytoplasm of lymphocytes increases number of statistically reliable correlations. The shedding of molecules of L-selectin in lymphocytes proceeds significantly more active than in monocytes. At that, medium plasma lymphocytes and large granular lymphocytes identified as natural killers are more predisposed to migration. However, lymphocytes entering condition of lympho-proliferation have less ability to adhesion.

CD2 promotes human natural killer cell membrane nanotube formation

Membrane nanotubes are thin membranous projections that physically connect two cells. While nanotubes have been studied in human natural killer (NK) cells and are implicated in aiding NK cell cytotoxic function, requirements for their formation to susceptible target cells remain incompletely understood. Here we demonstrate that the CD2-CD58/48 receptor-ligand interaction promotes and is required for nanotube formation in human NK cells. In the CD2(-) NK cell line YTS, a stable CD2 expression variant enabled effective nanotube formation, and was associated with better cytotoxic function. Importantly, only interactions between an NK cell and a susceptible target cell were associated with multiple nanotubes and the number of nanotubes was inversely correlated with their length. Quantitative live cell fluorescence microscopy of CD2 nanotubes revealed time-dependent enrichment and localization of CD2 to the nanotube tip, and blocking CD2 receptor-ligand interactions prevented nanotube formation. Increased nanotube formation was not simply a feature of receptor-ligand pairing, as a KIR-MHC interaction in the same cell line system failed to promote nanotube formation. Additionally, blocking LFA-1-ICAM and 2B4-CD48 receptor-ligand interactions failed to inhibit nanotube formation. Thus only specific receptor-ligand pairs promote nanotubes. CD2 also promoted nanotube formation in ex vivo NK cells suggesting that CD2 plays a crucial role in the generation of nanotubes between an NK cell and its target.

Immunomodulatory effects of Lactobacillous plantarum and Helicobacter pylori CagA⁺ on the expression of selected superficial molecules on monocyte and lymphocyte and the synthesis of cytokines in whole blood culture

Helicobacter pylori (H. pylori) infections are usually superficial and clinically asymptomatic, but in approximately 10-20% cases it can be more aggressive and associated with other pathologies. The reason for weak or strong pro-inflammatory responses in gastric mucosa that occur during H. pylori infection is not understood. Combined treatment, including antibiotic therapy with administration of probiotic bacteria along, considerably improves the effectiveness of H. pylori eradication and reduces the relapse rate. Thus, the aim of this study was to analyze the effect of Lactobacillus plantarum (L. plantarum) and/or H. pylori CagA(+) on leucocytes in whole blood cultures. This study revealed how selected strains of H. pylori and L. plantarum modulate expression of chosen membrane markers of monocytes and lymphocytes, and the cytokine synthesis of in vitro cultures. The level of IFN-γ was higher in cultures stimulated with L. plantarum than in combination of this two examinated strains. We also observe the tendency to increase the level of IFN-γ by L. planatrum in relation to cells stimulated by H. pylori. In contrast, both H. pylori alone and in combination with L. plantarum had a strong modulatory effect on the synthesis of interleukin-10. Moreover lymphocytes with higher expression of CD25 and CD58 receptors was observed only in those cultures that were stimulated with L. plantarum strain alone or in combination with H. pylori. Effects exerted on the immune system, both in terms of natural and adaptive response, constitute the only functional criterion of probiotic bacteria. The immunostimulant effects documented in this study suggest that Lactobacillus spp. can restore immune function of mucosal membrane during symptomatic infection with H. pylori.

Combined genetic inactivation of β2-Microglobulin and CD58 reveals frequent escape from immune recognition in diffuse large B cell lymphoma

We report that diffuse large B cell lymphoma (DLBCL) commonly fails to express cell-surface molecules necessary for the recognition of tumor cells by immune-effector cells. In 29% of cases, mutations and deletions inactivate the β2-Microglobulin gene, thus preventing the cell-surface expression of the HLA class-I (HLA-I) complex that is necessary for recognition by CD8(+) cytotoxic T cells. In 21% of cases, analogous lesions involve the CD58 gene, which encodes a molecule involved in T and natural killer cell-mediated responses. In addition to gene inactivation, alternative mechanisms lead to aberrant expression of HLA-I and CD58 in >60% of DLBCL. These two events are significantly associated in this disease, suggesting that they are coselected during lymphomagenesis for their combined role in escape from immune-surveillance.

[Effects of herbal cake-separated moxibustion on the expression of erythrocyte CD58 in different ages of healthy people]

OBJECTIVE

To observe the efficacy of herbal cake-separated moxibustion on the expression of erythrocyte CD58 in different ages of healthy people and explore the differences of the therapeutic effect in different ages and its mechanism.

METHODS

A total of 82 health participants were divided into a young age group and a middle-old age group according to the ages. They were treated with herbal cake-separated moxibustion on Shenque (CV 8), Guanyuan (CV 4), Zusanli (ST 36), Pishu (BL 20), Shenshu (BL 23) with cake made by Shudihuang (Radiz Re hmanniae Preparata), Shanyao (Rhizoma Dioscoreae), Shanzhuyu (Fructus Corni ), etc. The treatment was given for 10 sessions once other day and each acupoint for 3 successive dosages. The mean fluorescence intensities of erythrocyte CD58 were measured by flow cytometry before and after moxibustion.

RESULTS

After moxibustion, erythrocyte CD58 expression were significantly higher than that before moxibustion in two groups (both P < 0.01), particularly in young age group, which was significantly higher than that in middle-old age group (P < 0.01).

CONCLUSION

The effect of moxibustion in youth is evidently superior to that in middle-old age. Its mechanism is connected with that moxibustion can enhance the expression of erythrocyte CD58.

Human effector memory CD4+ T cells directly recognize allogeneic endothelial cells in vitro and in vivo

The frequency of circulating alloreactive human memory T cells correlates with allograft rejection. Memory T cells may be divided into effector memory (T(EM)) and central memory (T(CM)) cell subsets, but their specific roles in allograft rejection are unknown. We report that CD4+ T(EM) (CD45RO+ CCR7- CD62L-) can be adoptively transferred readily into C.B-17 SCID/bg mice and mediate the destruction of human endothelial cells (EC) in vascularized human skin grafts allogeneic to the T cell donor. In contrast, CD4+ T(CM) (CD45RO+ CCR7+ CD62L+) are inefficiently transferred and do not mediate EC injury. In vitro, CD4+ T(EM) secrete more IFN-gamma within 48 h in response to allogeneic ECs than do T(CM). In contrast, T(EM) and T(CM) secrete comparable amounts of IFN-gamma in response to allogeneic monocytes (Mo). In the same cultures, both T(EM) and T(CM) produce IL-2 and proliferate in response to IFN-gamma-treated allogeneic human EC or Mo, but T(CM) respond more vigorously in both assays. Blockade of LFA-3 strongly inhibits both IL-2 and IFN-gamma secretion by CD4+ T(EM) cultured with allogeneic EC but only minimally inhibits responses to allogeneic Mo. Blockade of CD80 and CD86 strongly inhibits IL-2 but not IFN-gamma production by in response to allogeneic EC or Mo. Transduction of EC to express B7-2 enhances allogeneic T(EM) production of IL-2 but not IFN-gamma. We conclude that human CD4+ T(EM) directly recognize and respond to allogeneic EC in vitro by secreting IFN-gamma and that this response depends on CD2 but not CD28. Consistent with EC activation of effector functions, human CD4+ T(EM) can mediate allogeneic EC injury in vivo.

Enhanced Fc-dependent cellular cytotoxicity of Fc fusion proteins derived from TNF receptor II and LFA-3 by fucose removal from Asn-linked oligosaccharides

Fucose removal from complex-type oligosaccharide of human IgGs results in a major enhancement of Fc-dependent cellular cytotoxicity. The aim of this study was to determine the effect of fucose removal on the effector function of another class of clinically important molecules that can effect cellular cytotoxicity, Fc fusion proteins. The receptors chosen for study were TNF receptor II and LFA-3, both of which have therapeutic significance. The fucosylated versions of these fusion proteins were produced in unmodified CHO cells, whereas the nonfucosylated counterparts were produced in CHO cells with alpha-1,6-fucosyltransferase, an enzyme required for fucosylation, knocked-out. Whilst binding activity of TNFRII-Fc and LFA-3-Fc were unchanged by fucose-removal, nonfucosylated Fc fusion proteins exhibited significantly higher Fc receptor gammaIIIa-binding and increased Fc-mediated cytotoxicity on target cells compared to fucosylated counterparts. Notably, in case of TNFRII-Fc, only the nonfucosylated protein exhibited potent Fc dependent cytotoxicity to transmembrane TNF-alpha expressing cells. These results prove that enhancement of Fc dependent cellular cytotoxicity by fucose-removal is effective in not only whole IgG but also Fc fusion proteins, and thus widens the potential of Fc-fusion proteins as therapeutic candidates.

Analyses of recombinant vaccinia and fowlpox vaccine vectors expressing transgenes for two human tumor antigens and three human costimulatory molecules

PURPOSE

The poor immunogenicity of tumor antigens and the antigenic heterogeneity of tumors call for vaccine strategies to enhance T-cell responses to multiple antigens. Two antigens expressed noncoordinately on most human carcinomas are carcinoembryonic antigen (CEA) and MUC-1. We report here the construction and characterization of two viral vector vaccines to address these issues.

EXPERIMENTAL DESIGN

The two viral vectors analyzed are the replication-competent recombinant vaccinia virus (rV-) and the avipox vector, fowlpox (rF-), which is replication incompetent in mammalian cells. Each vector encodes the transgenes for three human costimulatory molecules (B7-1, ICAM-1, and LFA-3, designated TRICOM) and the CEA and MUC-1 transgenes (which also contain agonist epitopes). The vectors are designated rV-CEA/MUC/TRICOM and rF-CEA/MUC/TRICOM.

RESULTS

Each of the vectors is shown to be capable of faithfully expressing all five transgenes in human dendritic cells (DC). DCs infected with either vector are shown to activate both CEA- and MUC-1-specific T-cell lines to the same level as DCs infected with CEA-TRICOM or MUC-1-TRICOM vectors. Thus, no evidence of antigenic competition between CEA and MUC-1 was observed. Human DCs infected with rV-CEA/MUC/TRICOM or rF-CEA/MUC/TRICOM are also shown to be capable of generating both MUC-1- and CEA-specific T-cell lines; these T-cell lines are in turn shown to be capable of lysing targets pulsed with MUC-1 or CEA peptides as well as human tumor cells endogenously expressing MUC-1 and/or CEA.

CONCLUSION

These studies provide the rationale for the clinical evaluation of these multigene vectors in patients with a range of carcinomas expressing MUC-1 and/or CEA.

Acquisition of HLA-DR and costimulatory molecules by T cells from allogeneic antigen presenting cells

There is accumulating evidence that cell surface molecules may be transferred between cells during an encounter. The aim of these experiments was to determine whether transfer of allogeneic material to T cells could influence human alloresponses. CD4(+) cells were cocultured with M1 cell (human fibroblast) transfectants expressing HLA-DR1, CD80 and CD86 alone or in combination. Up to 95% of the allogeneic T cells became positive for HLA-DR and the appropriate costimulatory molecules after only 4 h of coculture. The phenomenon required cell contact and cell membrane fluidity because transfer was abolished by transwell separation of the M1 cells and the T cells or by pre-treatment of the APC with paraformaldehyde. Flow cytometric sorting of T cells after coculture and subsequent mixed lymphocyte assays demonstrated that the T cells that had acquired both HLA-DR and costimulatory molecules could act as potent antigen presenting cells. Finally, matured human dendritic cells were also shown to transfer these molecules to CD4(+) cells, which could then act as antigen presenting cells for unprimed T cells and for a cell line specific for an HLA-peptide complex acquired from the DCs. Taken together, these data suggest a novel pathway for the amplification of human alloresponses.

Immunotherapy with T11TS / S-LFA-3 specifically induces apoptosis of brain tumor cells by augmenting intracranial immune status

BACKGROUND

Immunopotentiating agents are the best options in cancer therapeutics because they can specifically destroy tumor cells via immunocytes, which are mostly apoptotic in nature. Previously, immunotherapy with T11TS / SLFA-3 in a ethyl-nitrosourea (ENU)-induced animal model (Druckrey rats) of neural neoplasm showed a significant tumor mass destruction by augmenting the cellular immune status.

MATERIALS AND METHODS

The modulations of the peripheral as well as neural immune systems after T11TS administration were monitored by assessing the CD4+ and CD8+ lymphocytes, along with the cytotoxic activity of splenic and brain infiltrating lymphocytes (BIL). The rate of apoptosis of the tumor cells, microglial cells (Mg) and BIL were measured by flow cytometry-based propidium iodide analysis and TUNEL assay.

RESULTS

Cell cycle phase distribution analysis by propidium iodide -FACS and TUNEL assay revealed that T11TS administration gradually increased the number of apoptotic brain tumor cells and, at the same time, decreased the number of dividing cells. Up-regulation of the CD4+ and CD8+ lymphocytes were observed after T11TS administration in ENU - induced immunosuppressed animals. A gradual increment of cytotoxicity of splenic and BIL was also demonstrated after successive administration of T11TS.

CONCLUSION

These data strongly support the specific apoptosis-inducing role of T11TS in experimental brain tumor cells. Apoptosis of BIL and Mg, that occurred to a much lower level, can be explained in terms of changes in the neural immune system before and after T11TS application.

Functional analysis of highly defined, FACS-isolated populations of human regulatory CD4+ CD25+ T cells

The importance of CD4+ CD25+ regulatory T cells (Treg) in maintaining immune homeostasis has been directly demonstrated in vivo by their manipulation in a number of autoimmune disease models in the mouse. In the study of human regulatory cells, we have found that the cells that consistently demonstrate the in vitro regulatory activity most similar to that described for murine cells in vitro are best identified by restricting the isolation of CD25+ CD4 T cells to those cells expressing only the highest levels of CD25, representing approximately 2-3% of total CD4 T cells. Thus, it is the CD4+ CD25high subset that exhibits the in vitro characteristics that are identical to the CD4+ CD25+ regulatory cells initially characterized in mice. Furthermore, the cells expressing medium to low levels of CD25 not only do not exhibit suppressive activity directly ex vivo, but also actually contain a significant proportion of CD62L- CD4 T cells which are believed to be in vivo activated T cells. Due to the inherent difficulties in using CD25 as a marker for the purification of Treg cells, the finding that selection of the CD25high subset of CD4+ CD25+ T cells minimizes the co-isolation of contaminating activated CD4 T cells is important for future studies of these Treg cells in human disease. In order to perform these studies, we first had to establish a highly reproducible 'micro in vitro co-culture' assay system to enable the functional analysis of high-purity, but low-yield regulatory populations derived from FACS sorting. With this system in place, we are poised to dissect the potential heterogeneity of mechanisms employed by highly specific subpopulations of CD4+ CD25+ cells.

Phase I study of immunization with dendritic cells modified with fowlpox encoding carcinoembryonic antigen and costimulatory molecules

PURPOSE

To determine the safety and immunologic and clinical efficacy of a dendritic cell vaccine modified to hyperexpress costimulatory molecules and tumor antigen.

EXPERIMENTAL DESIGN

In this phase I study, we administered one or two cycles of four triweekly s.c./intradermal injections of ex vivo generated dendritic cells modified with a recombinant fowlpox vector encoding carcinoembryonic antigen (CEA) and a triad of costimulatory molecules [rF-CEA(6D)-TRICOM]. Controls consisted of immature dendritic cells loaded with tetanus toxoid and a HLA A2-restricted peptide derived from cytomegalovirus pp65 protein.

RESULTS

Fourteen patients (11 with colorectal cancer and 3 with non-small cell lung cancer) were enrolled and 12 completed at least one cycle of immunization. There were no grade 3/4 toxicities directly referable to the immunizations. One patient had a decrease in the CEA level from 46 to 6.8 and a minor regression in adenopathy that occurred several months after completion of the immunizations. Five other patients were stable through at least one cycle of immunization (3 months). Direct analysis of peripheral blood mononuclear cells using the ELISpot assay showed an increase in the frequency of CEA-specific T cells in 10 patients (range, 10-541 CEA-specific cells/10(5) peripheral blood mononuclear cells). There was a trend for a greater peak frequency of CEA-specific T cells among those with either a minor response or a stable disease following at least one cycle of therapy. A second cycle was not associated with higher T-cell frequencies. Cytokine flow cytometry showed CEA-specific immune response among both CD4(+) and CD8(+) T cells in all immune responders.

CONCLUSION

This immunization strategy is safe and activates potent CEA-specific immune responses.

The active role played by xenogeneic endothelial cells in the indirect presentation pathway is not lymphocyte trans-co-stimulation

The human CD4+ T lymphocyte response to major histocompatibility complex (MHC) class II-negative porcine endothelial cells is dependent on the presence of human monocytes through a human leukocyte antigen (HLA) class II-restricted indirect presentation pathway. Because the role of porcine endothelial cells had been previously shown to do more than simply supply xenopeptides, co-stimulatory signals were analysed. Endothelial cells were shown to express the CD54, CD58, CD59 and CD86 transcripts; however, no membrane B7 molecule could be detected. Blocking experiments in a direct pathway model confirmed that porcine endothelial cells could provide co-stimulatory signals to human T cells through the CD2 and LFA-1 pathways. Nevertheless, the proliferation achieved in the indirect presentation model required co-stimulation by LFA-1, CD2 and CD28, engaged by co-stimulation molecules expressed in the cis-form by the human monocytes. These results clearly show that the active role played by the endothelial cells in the indirect pathway is not lymphocyte trans-co-stimulation and suggest that cis-co-stimulation dominates trans-co-stimulation when both are present.

Immunological Synapses Are Versatile Structures Enabling Selective T Cell Polarization

Helper T cells discriminate among different antigen-presenting cells to provide their help in a selective fashion. The molecular mechanisms leading to this exquisite selectivity are still elusive. Here, we demonstrate that immunological synapses are dynamic and adaptable structures allowing T cells to communicate with multiple cells. We show that T cells can form simultaneous immunological synapses with cells presenting different levels of antigenic ligands but eventually polarize toward the strongest stimulus. Remarkably, living T cells form discrete foci of signal transduction of different intensities during the interaction with different antigen-presenting cells and rapidly relocate TCR and Golgi apparatus toward the cell providing the strongest stimulus. Our results illustrate that, although T cell activation requires sustained signaling, T cells are capable of rapid synapse remodeling and swift polarization responses. The combination of sustained signaling with preferential and rapid polarization provides a mechanism for the high sensitivity and selectivity of T cell responses.

2B4 (CD244) is expressed and functional on human eosinophils

Eosinophils are present in parasitic, allergic, various immunological, and malignant disorders as well as in a variety of idiopathic hypereosinophilic syndromes. However, their exact role in some of these conditions remains elusive. They can be activated both in vivo and in vitro by various agonists, such as Igs, lipid mediators, and cytokines. By phenotyping the surface of the eosinophils, it may be possible to better define their function(s) in different pathophysiological settings. In the present work we screened eosinophils with a panel of Abs recognizing CD2 subfamily receptors usually present on a number of hemopoietic cells. We have demonstrated that human peripheral blood eosinophils, but not basophils or neutrophils, express NTB-A. In addition eosinophils express 2B4, CD84, CD58, and CD48, but not signaling lymphocytic activation molecule or CD2, on their surface (FACS). Cross-linking of 2B4 on eosinophils elicited a significant release of eosinophil peroxidase (30 min), IFN-gamma, and IL-4 (18 h). Moreover, activation of eosinophils via 2B4 induced eosinophil-mediated cytotoxicity toward two malignant cell lines, i.e., mouse mastocytoma P815 and EBV-infected 721.221 B cell lines. Cross-linking of 2B4 on the surface of eosinophils or pervenadate treatment elicited ERK and tyrosine phosphorylation, respectively. Furthermore, we showed that eosinophils express slam-associated protein. The demonstration that human eosinophils express a functional 2B4 receptor indicates a broader role for these cells in health and disease.

[Morphological and functional characteristics of lymphokine-activated killer cells generated from the mononuclear cells of human peripheral blood]

The aim of this research was to study the morphological, functional and immunophenotypical characteristics of lymphokine-activated killer cells (LAKC) generated from the mononuclear cells (MNC) of healthy donors' peripheral blood at different time intervals after the cultivation with interleukin-2 (IL-2). LAKC had the appearance of large lymphoid cells of prolymphocyte and immunoblast type with highly pyroninophilic cytoplasm and electrone-microscopic features indicative of synthetic activity. LAKC were shown to intensely express activation antigens and adhesion molecules on their surface and to posess high cytotoxic potential in respect to tumor cells. Time-course of LAKC surface antigen expression corresponded to the changes of a proportion of activated cellular forms, generated from MNC of healthy donors' peripheral blood by incubation with IL-2. On the basis of these experimental findings, the usage of 3-5-day culture of LAKC could be recommended for the immunotherapy of malignant tumors.

A novel, rapid and sensitive heterotypic cell adhesion assay for CD2-CD58 interaction, and its application for testing inhibitory peptides

The immunoglobulin CD2 is a cell adhesion molecule that mediates T-cell activation by binding to its receptor CD58 on antigen-presenting cells (APCs). Modulation or inhibition of this interaction has been shown to be therapeutically useful. E-rosetting assay is usually applied in the study of the modulation of CD2-CD58 interaction. In this study, we demonstrated a novel, rapid and sensitive heterotypic cell adhesion assay for CD2-CD58 interaction. The CD2 expression on the surface of Jurkat cells and the CD58 expression on the Caco-2 cells were confirmed by flow cytometry and ELISA studies, respectively. Then Jurkat cells were fluorescent-labeled with 2 microM of BCECF-AM for 45 min at 37 degrees C before adding to confluent Caco-2 monolayers cultured in 96-well culture dishes. After 30 min, non-adherent Jurkat cells were removed by washing with PBS, while the monolayer-associated Jurkat cells were lysed with 0.5 ml of 2% Triton X-100 in 0.1 M NaOH. Fluorescence (FL) was quantitated using a microplate fluorescence analyzer with BCECF's excitation maximum of 485 nm and emission maximum of 535 nm. This method was successfully applied for testing inhibitory peptides to CD2-CD58 interaction.

Analysis of human and primate CD2 molecules by protein sequence and epitope mapping with anti-human CD2 antibodies

A panel of anti-human CD2 monoclonal antibodies (mAb) and soluble human CD58 (LFA-3) were tested for binding to human peripheral blood mononuclear cells (PBMCs), recombinant human CD2 and mononuclear cells from Cynomolgus, Rhesus and African green monkey, Stump-tail, Pig-tail and Assamese macaque, Chimpanzee and Baboon. This analysis revealed that whilst some antibodies recognized all species, there were differential binding profiles with others. Three antibodies, MEDI-507, 6F10.3 and 4B2, recognized CD2 from human and Chimpanzee but not that from the other primates. We have cloned eight of the previously unknown primate CD2 molecules and report here their sequences for the first time. This analysis revealed that 12 amino acids formed a common set of residues in the extra cellular domain of human and Chimpanzee CD2. Using a "knock-in" mutagenesis approach starting with Baboon CD2, which does not bind MEDI-507, 6F10.3 and 4B2, we have identified three residues in the adhesion domain of human CD2 which are critical for its binding to these mAbs. These residues, N18, K55 and T59 define a region located outside of the previously described binding regions on CD2. Affinity measurements of the mutants revealed a variety of degrees of binding restoration for MEDI-507, 6F10.3 and 4B2, indicating that there are fine differences within a given epitope. Furthermore, the analysis of the competition of several of the anti-human CD2 antibodies with each other and CD58 demonstrated the existence of a continuum of overlapping epitopes on human CD2, which is in contrast to the commonly held belief that epitopes on human CD2 are clearly segregated.

Human B cells that hyperexpress a triad of costimulatory molecules via avipox-vector infection: an alternative source of efficient antigen-presenting cells

Dendritic cells (DCs) are the most potent of the antigen-presenting cells (APCs). Preparation of sufficient numbers of mature DCs, however, is both costly and time-consuming. We have examined here the possibility of using an alternative source of APCs that would be easier to obtain, would not require extensive culture, and thus would be more applicable to human immunotherapy protocols. We show here that freshly isolated human B cells can be efficiently infected by a replication-defective fowlpox recombinant vector, designated rF-TRICOM (TRIad of COstimulatory Molecules), to markedly increase surface expression of the human costimulatory molecule B7-1 and moderately increase expression of intercellular adhesion molecule-1 (ICAM-1) and leukocyte function-associated antigen-3 (LFA-3). Peptide-pulsed rF-TRICOM-infected B cells were highly efficient in activating antigen-specific human T cells and shown to be superior to the use of CD40L in enhancing APC potency. Moreover, when infection of freshly isolated B cells with rF-TRICOM was combined with CD40L, a still further marked enhancement of the antigen-presenting potency was observed. Ex vivo-generated antigen-specific T cells activated in this manner might be applied to experimental protocols or used for adoptive transfer in immunotherapy protocols.

Modified vaccinia virus ankara recombinants are as potent as vaccinia recombinants in diversified prime and boost vaccine regimens to elicit therapeutic antitumor responses

Cancer vaccine regimens use various strategies to enhance immune responses to specific tumor-associated antigens (TAAs), including the increasing use of recombinant poxviruses [vaccinia (rV) and fowlpox (rF)] for delivery of the TAA to the immune system. However, the use of replication competent vectors with the potential of adverse reactions have made attenuation a priority for next-generation vaccine strategies. Modified vaccinia Ankara (MVA) is a replication defective form of vaccinia virus. Here, we investigated the use of MVA encoding a tumor antigen gene, carcinoembryonic antigen (CEA), in addition to multiple costimulatory molecules (B7-1, intercellular adhesion molecule-1, and lymphocyte function-associated antigen-3 designated TRICOM). Vaccination of mice with MVA-CEA/TRICOM induced potent CD4+ and CD8+ T-cell responses specific for CEA. MVA-CEA/TRICOM could be administered twice in vaccinia naïve mice and only a single time in vaccinia-immune mice before being inhibited by antivector-immune responses. The use of MVA-CEA/TRICOM in a diversified prime and boost vaccine regimen with rF-CEA/TRICOM, however, induced significantly greater levels of both CD4+ and CD8+ T-cell responses specific for CEA than that seen with rV-CEA/TRICOM prime and rF-CEA/TRICOM boost. In a self-antigen tumor model, the diversified MVA-CEA/TRICOM/rF-CEA/ TRICOM vaccination regimen resulted in a significant therapeutic antitumor response as measured by increased survival, when compared with the diversified prime and boost regimen, rV-CEA/TRICOM/rF-CEA/TRICOM. The studies reported here demonstrate that MVA, when used as a prime in a diversified vaccination, is clearly comparable with the regimen using the recombinant vaccinia in both the induction of cellular immune responses specific for the "self"-TAA transgene and in antitumor activity.

Infection of U937 Monocytic Cells withChlamydia pneumoniaeInduces Extensive Changes in Host Cell Gene Expression

The effect of infection with Chlamydia pneumoniae on host messenger RNA expression in human monocytic cells with complement DNA microarrays was studied. The data chronicle a cascade of transcriptional events affecting 128 genes, many of which have not previously been reported to be affected by C. pneumoniae infection. Down-regulated genes are primarily associated with RNA and DNA metabolism, chromosomal stability, and cell-cycle regulation. Up-regulated messages include those for a variety of genes with important proinflammatory functions. Many of the up-regulated genes-including the hyaluron receptor CD44, vasoconstrictor endothelin-1, smooth muscle growth factor heparin-binding EGF-like growth factor, and fatty acid binding protein-4-had been previously described as linked to the development of atherosclerosis and other chronic inflammatory diseases. C. pneumoniae-infected monocytes can contribute to the development and progression of diseases for which acute or chronic inflammation has been shown to be important, such as atherosclerosis.

Red blood cells promote survival and cell cycle progression of human peripheral blood T cells independently of CD58/LFA-3 and heme compounds

Red blood cells (RBC) are known to modulate T cell proliferation and function possibly through downregulation of oxidative stress. By examining parameters of activation, division, and cell death in vitro, we show evidence that the increase in survival afforded by RBC is due to the maintenance of the proliferative capacity of the activated T cells. We also show that the CD3+CD8+ T cell subset was preferentially expanded and rescued from apoptosis both in bulk peripheral blood lymphocyte cultures and with highly purified CD8+ T cells. The ability of RBC to induce survival of dividing T cells was not affected by blocking the CD58/CD2 interaction. Moreover, addition of hemoglobin, heme or protoporphyrin IX to cultures of activated T cells did not reproduce the effect of intact RBC. Considering that RBC circulate throughout the body, they could play a biological role in the modulation of T cell differentiation and survival in places of active cell division. Neither CD58 nor the heme compounds studied seem to play a direct relevant role in the modulation of T cell survival.

A triad of costimulatory molecules synergize to amplify T-cell activation in both vector-based and vector-infected dendritic cell vaccines

The activation of a T cell has been shown to require two signals via molecules present on professional antigen presenting cells: signal 1, via a peptide/MHC complex, and signal 2, via a costimulatory molecule. Here, the role of three costimulatory molecules in the activation of T cells was examined. Poxvirus (vaccinia and avipox) vectors were employed because of their ability to efficiently express multiple genes. Murine cells provided with signal 1 and infected with either recombinant vaccinia or avipox vectors containing a TRIad of COstimulatory Molecules (B7-1/ICAM-1/LFA-3, designated TRICOM) induced the activation of T cells to a far greater extent than cells infected with vectors expressing any one or two costimulatory molecules. Despite this T-cell "hyperstimulation" using TRICOM vectors, no evidence of apoptosis above that seen using the B7-1 vector was observed. Results employing the TRICOM vectors were most dramatic under conditions of either low levels of first signal or low stimulator cell to T-cell ratios. Experiments employing a four-gene construct also showed that TRICOM recombinants could enhance antigen-specific T-cell responses in vivo. These studies thus demonstrate the ability of vectors to introduce three costimulatory molecules into cells, thereby activating both CD4+ and CD8+ T-cell populations to levels greater than those achieved with the use of only one or two costimulatory molecules. This new threshold of T-cell activation has broad implications in vaccine design and development. Dendritic cells infected with TRICOM vectors were found to greatly enhance naïve T-cell activation, and peptide-specific T-cell stimulation. In vivo, peptide-pulsed DCs infected with TRICOM vectors induced cytotoxic T lymphocyte activity markedly and significantly greater than peptide-pulsed DCs.

Vaccine therapy of established tumors in the absence of autoimmunity

PURPOSE

Many current clinical trials involve vaccination of patients with vaccines directed against tumor-associated antigens, which are, in actuality, "self-antigens" overexpressed in tumors as compared with normal tissues. As tumor vaccines become more potent through the addition of costimulatory molecules and cytokines and the use of diversified prime and boost regimes, the level of concern rises regarding the balance between antitumor immunity and pathological autoimmunity. Studies were conducted using mice bearing a transgenic self-antigen [human carcinoembryonic antigen (CEA)], which is expressed in some normal adult tissues, and tumor expressing the same self-antigen. These mice were vaccinated with recombinant poxviral vectors [recombinant vaccinia, recombinant fowlpox (rF)] encoding the CEA transgene as well as a triad of costimulatory molecules [B7-1, ICAM-1, and LFA-3 (TRICOM)]. Here we investigate the mechanism of tumor therapy and evaluate the safety of such a regimen in a self-antigen system. To our knowledge, the study reported here is the first description of a vaccine to a defined antigen where the regimen is potent enough to induce tumor therapy in the absence of autoimmunity.

EXPERIMENTAL DESIGN

CEA transgenic mice were transplanted with CEA-expressing tumors. Fourteen days later, mice were vaccinated with recombinant vaccinia-CEA/TRICOM admixed with recombinant murine granulocyte macrophage colony-stimulating factor and then given low-dose interleukin 2. Mice were boosted on days 21, 28, and 35 with rF-CEA/TRICOM admixed with rF-granulocyte macrophage colony-stimulating factor and then given low-dose interleukin 2. Mice were monitored for survival and compared with groups of mice vaccinated in a similar manner with poxviral vectors containing CEA/B7-1 or CEA transgenes. To determine the mechanism of antitumor therapy, mice were depleted of T-cell subpopulations before vaccination with the CEA/TRICOM regimen. Mice successfully cured of tumor and age-matched control mice were monitored for 1 year. At 1 year, several clinical assays were carried out involving analysis of 9 serological parameters, 11 urinalysis parameters, and 14 immunological parameters. In addition, histopathology was performed on 42 tissues/mouse.

RESULTS

The CEA/TRICOM vaccination regimen induced a therapeutic antitumor response as measured by increased survival, which was due largely to induced T-cell responses (both CD4(+) and CD8(+)) as determined by selective T-cell subset depletion. The CEA/TRICOM vaccination regimen induced a significant increase in proliferation of CD4(+) T cells to CEA protein and a significant increase in secretion of IFN-gamma from CD8(+) T cells in response to a defined CEA epitope. Despite CEA expression in normal adult gastrointestinal tissues, no toxicity was observed in the CEA/TRICOM-vaccinated group when an array of clinical serum and urine chemistry assays was conducted 1 year after vaccination. Moreover, a comprehensive histopathological evaluation of all tissues from these groups also showed no evidence of toxicity.

CONCLUSIONS

Activation of T cells directed against a tumor-associated self-antigen, sufficient to mediate therapeutic antitumor immunity, was observed in vivo without the development of autoimmunity as analyzed by a comprehensive evaluation of biochemical, immunological, and histopathological criteria. These studies demonstrate that the use of vectors containing as many as three costimulatory molecules does not induce autoimmunity or other pathology. These studies thus demonstrate that a balance can indeed be achieved between the induction of an immune response to a self-antigen, which is capable of antitumor therapy, and the absence of autoimmunity.