STAT3 inhibitor Stattic and its analogues inhibit STAT3 phosphorylation and modulate cytokine secretion in senescent tumour cells

Signal transducer and activator of transcription 3 (STAT3) signalling serves an important role in carcinogenesis and cellular senescence, and its inhibition in tumour cells represents an attractive therapeutic target. Premature cellular senescence, a process of permanent proliferative arrest of cells in response to various inducers, such as cytostatic drugs or ionizing radiation, is accompanied by morphological and secretory changes, and by altered susceptibility to chemotherapeutic agents, which can thereby complicate their eradication by cancer therapies. In the present study, the responsiveness of proliferating and docetaxel (DTX)‑induced senescent cancer cells to small molecule STAT3 inhibitor Stattic and its analogues was evaluated using tumour cell lines. These agents displayed cytotoxic effects in cell viability assays on both proliferating and senescent murine TRAMP‑C2 and TC‑1 cells; however, senescent cells were markedly more resistant. Western blot analysis revealed that Stattic and its analogues effectively inhibited constitutive STAT3 phosphorylation in both proliferating and senescent cells. Furthermore, whether the Stattic‑derived inhibitor K1836 could affect senescence induction or modulate the phenotype of senescent cells was evaluated. K1836 treatment demonstrated no effect on senescence induction by DTX. However, the K1836 compound significantly modulated secretion of certain cytokines (interleukin‑6, growth‑regulated oncogene α and monocyte chemoattractant protein‑1). In summary, the present study demonstrated differences between proliferating and senescent tumour cells in terms of their susceptibility to STAT3 inhibitors and demonstrated the ability of the new STAT3 inhibitor K1836 to affect the secretion of essential components of the senescence‑associated secretory phenotype. The present study may be useful for further development of STAT3 inhibitor‑based therapy of cancer or age‑related diseases.

Type I interferon signaling in malignant blasts contributes to treatment efficacy in AML patients

While type I interferon (IFN) is best known for its key role against viral infection, accumulating preclinical and clinical data indicate that robust type I IFN production in the tumor microenvironment promotes cancer immunosurveillance and contributes to the efficacy of various antineoplastic agents, notably immunogenic cell death inducers. Here, we report that malignant blasts from patients with acute myeloid leukemia (AML) release type I IFN via a Toll-like receptor 3 (TLR3)-dependent mechanism that is not driven by treatment. While in these patients the ability of type I IFN to stimulate anticancer immune responses was abolished by immunosuppressive mechanisms elicited by malignant blasts, type I IFN turned out to exert direct cytostatic, cytotoxic and chemosensitizing activity in primary AML blasts, leukemic stem cells from AML patients and AML xenograft models. Finally, a genetic signature of type I IFN signaling was found to have independent prognostic value on relapse-free survival and overall survival in a cohort of 132 AML patients. These findings delineate a clinically relevant, therapeutically actionable and prognostically informative mechanism through which type I IFN mediates beneficial effects in patients with AML.

Discovery of small molecule mechanistic target of rapamycin inhibitors as anti-aging and anti-cancer therapeutics

To date, the most studied drug in anti-aging research is the mTOR inhibitor - rapamycin. Despite its almost perfect anti-aging profile, rapamycin exerts one significant limitation - inappropriate physicochemical properties. Therefore, we have decided to utilize virtual high-throughput screening and fragment-based design in search of novel mTOR inhibiting scaffolds with suitable physicochemical parameters. Seven lead compounds were selected from the list of obtained hits that were commercially available (4, 5, and 7) or their synthesis was feasible (1, 2, 3, and 6) and evaluated in vitro and subsequently in vivo. Of all these substances, only compound 3 demonstrated a significant cytotoxic, senolytic, and senomorphic effect on normal and cancerous cells. Further, it has been confirmed that compound 3 is a direct mTORC1 inhibitor. Last but not least, compound 3 was found to exhibit anti-SASP activity concurrently being relatively safe within the test of in vivo tolerability. All these outstanding results highlight compound 3 as a scaffold worthy of further investigation.

Chronic inflammation decreases HSC fitness by activating the druggable Jak/Stat3 signaling pathway

Chronic inflammation represents a major threat to human health since long-term systemic inflammation is known to affect distinct tissues and organs. Recently, solid evidence demonstrated that chronic inflammation affects hematopoiesis; however, how chronic inflammation affects hematopoietic stem cells (HSCs) on the mechanistic level is poorly understood. Here, we employ a mouse model of chronic multifocal osteomyelitis (CMO) to assess the effects of a spontaneously developed inflammatory condition on HSCs. We demonstrate that hematopoietic and nonhematopoietic compartments in CMO BM contribute to HSC expansion and impair their function. Remarkably, our results suggest that the typical features of murine multifocal osteomyelitis and the HSC phenotype are mechanistically decoupled. We show that the CMO environment imprints a myeloid gene signature and imposes a pro-inflammatory profile on HSCs. We identify IL-6 and the Jak/Stat3 signaling pathway as critical mediators. However, while IL-6 and Stat3 blockage reduce HSC numbers in CMO mice, only inhibition of Stat3 activity significantly rescues their fitness. Our data emphasize the detrimental effects of chronic inflammation on stem cell function, opening new venues for treatment.

Design, synthesis, and in vitro evaluation of BP-1-102 analogs with modified hydrophobic fragments for STAT3 inhibition

Twelve novel analogs of STAT3 inhibitor BP-1-102 were designed and synthesised with the aim to modify hydrophobic fragments of the molecules that are important for interaction with the STAT3 SH2 domain. The cytotoxic activity of the reference and novel compounds was evaluated using several human and two mouse cancer cell lines. BP-1-102 and its two analogs emerged as effective cytotoxic agents and were further tested in additional six human and two murine cancer cell lines, in all of which they manifested the cytotoxic effect in a micromolar range. Reference compound S3I-201.1066 was found ineffective in all tested cell lines, in contrast to formerly published data. The ability of selected BP-1-102 analogs to induce apoptosis and inhibition of STAT3 receptor-mediated phosphorylation was confirmed. The structure–activity relationship confirmed a demand for two hydrophobic substituents, i.e. the pentafluorophenyl moiety and another spatially bulky moiety, for effective cytotoxic activity and STAT3 inhibition.

Abstract 6686: SO-C101 displays strong anti-tumor effect in TC-1 and TRAMP-C2 tumor mice and in combination with PD-1 blockade prevents tumor development in a NK and CD8+ T cells dependent manner

SO-C101 (RLI-15) is a superagonist fusion protein of interleukin (IL)-15 and the IL-15 receptor α (IL-15Rα) sushi+ domain designed to bypass the need of endogenous IL-15Rα, thereby leveraging the activity of IL-15 in vivo on target immune cells and reducing the toxicity of IL-15 as such. SO-C101 was previously shown to exhibit a potent anti-metastatic activity in Renca, B16F10 melanoma and delayed tumor growth in T cell-based mouse tumor models (CT26, MC38). Here we investigated the anti-tumor efficacy in predominantly natural killer (NK)-cell based mouse tumor models TC-1 and TRAMP-C2. We showed that SO-C101 monotherapy was effective in the treatment of established TC-1 tumors, which was dependent on the presence of both NK and CD8+ T cells, but not CD4+ T cells. In an early treatment setting SO-C101 significantly decreased the rate of tumor development also in dependence on NK and CD8+ T cells. SO-C101 effectively reduced tumor growth in TRAMP-C2 mice in early and advanced treatment settings. However, only in combination with anti-PD-1 antibody treatment the tumor development was prevented in majority of mice. This effect was durable, and the new tumor development was further significantly delayed after a tumor cell re-challenge, which suggests the involvement of memory T cells despite an important NK cell role in anti-tumor efficacy in these models. The efficacy of SO-C101 and anti-PD-1 treatment was not dependent on CD4+ T cells, but mainly on NK and CD8+ T cells. Interestingly, SO-C101 and anti-PD-1 treatment in double NK/CD8+ T cell-depleted mice decreased tumor growth which suggests an involvement of other immune cell populations in the anti-tumor efficacy. SO-C101 stimulated the proliferation and the cytotoxic activity of NK cells and memory CD8+ T cells without significant expansion of regulatory T cells. These data show the importance of various immune cell populations during SO-C101 monotherapy and the treatment in combination with anti-PD-1 antibodies, and set a base for further complex analysis of SO-C101 behavior. The therapeutic potential of SO-C101 is currently being tested in an ongoing Phase I clinical study in cancer patients.

Citation Format: Irena Adkins, Romana Mikyskova, Nada Hradilova, Guy de Martynoff, David Bechard, Ulrich Moebius, Milan Reinis, Radek Spisek. SO-C101 displays strong anti-tumor effect in TC-1 and TRAMP-C2 tumor mice and in combination with PD-1 blockade prevents tumor development in a NK and CD8+ T cells dependent manner [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6686.

Abstract B35: Studies on photo-sensitivity of a glycol porphyrin derivative and its anti-tumor efficacy

Photodynamic therapy (PDT) has attracted great attention in cancer treatment. Porphyrin derivative with ethylene glycol chains linked to meta position of meso-tetraphenylporphyrin, mTPP(EG)4, is one of assumed compounds that can be used for treatment of cancer in photodynamic therapy (PDT). The aim of the study is to demonstrate the photodynamic efficacy in vitro and in vivo as well as to analyze its therapeutic mechanism. The cell viability, cell surface exposure of immunogenic molecules, maturation and phagocytic capacity of PDT-treated tumor cells were monitored by flow cytometry. The kinetics of key components of ER stress-mediated apoptotic pathway was analyzed by Western blotting. Our first results indicate a new and attractive possibility of immunogenic cell death induction. Initiation of immunogenic cell death by PDT was successfully demonstrated in vitro on human and mouse tumor cell lines. The effects of mTPP(EG)4 were compared with the effects of mTPP(EG)4 without subsequent photoactivation, hypericin-mediated PDT, and high hydrostatic pressure. In vivo assays evaluated immunogenicity of mTPP(EG)4 in mice and assessed the ability of PDT treated cells to induce effective immunity against transplanted syngeneic tumors (mouse TRAMP-C2, TC-1 and B16). The results obtained in this study will provide a basis for possible further preclinical experiments with mTPP(EG)4 or other derivatives, testing their potential in PDT and development of new antitumor therapies.

Citation Format: Sarka Vosahlikova, Irena Kusova Moserova, Jarmila Kralova, Milan Reinis, Romana Mikyskova, Jitka Palich Fucikova. Studies on photo-sensitivity of a glycol porphyrin derivative and its anti-tumor efficacy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B35.

Abstract B96: Calreticulin exposure on malignant blasts correlates with improved NK cell-mediated cytotoxicity in AML patients

In some settings, cancer cells responding to treatment undergo an immunogenic form of cell death that is associated with the abundant emission of danger signals in the form of damage-associated molecular patterns (DAMPs). Accumulating preclinical and clinical evidence indicates that danger signals play a crucial role in the (re-)activation of antitumor immune responses in vivo, thus having a major impact on patient prognosis. We have previously demonstrated that the presence of calreticulin (CRT) on the surface of malignant blasts is a positive prognostic biomarker for patients with acute myeloid leukemia (AML). CRT exposure not only correlated with enhanced T cell-dependent antitumor immunity in this setting but also affected the number of circulating NK cells upon restoration of normal hematopoiesis. Here, we report that CRT exposure on malignant blasts is associated with enhanced NK cell cytotoxic and secretory functions, both in AML patients and in vivo in mice. The ability of CRT to stimulate NK cells relies on CD11c+CD14high cells that, upon exposure to CRT, display higher levels of IL-15Rα, maturation markers (CD86 and HLA-DR), and CCR7. CRT exposure on malignant blasts also correlates with the upregulation of genes coding for type I interferons (IFNs). This suggests that CD11c+CD14high cells have increased capacity to migrate to secondary lymphoid organs, where can efficiently deliver stimulatory signals (IL-15Rα/IL-15) to NK cells. These findings delineate a multipronged, clinically relevant mechanism whereby surface-exposed CRT favors NK cell activation in AML patients.

Citation Format: Iva Truxova, Lenka Kasikova, Cyril Salek, Michal Hensler, Daniel Lysak, Peter Holicek, Pavla Bilkova, Monika Holubova, Xiufen Chen, Romana Mikyskova, Milan Reinis, Marek Kovar, Barbora Tomalova, Justin Kline, Lorenzo Galluzzi, Radek Spisek, Jitka Fucikova. Calreticulin exposure on malignant blasts correlates with improved NK cell-mediated cytotoxicity in AML patients [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B96.

Calreticulin exposure on malignant blasts correlates with improved natural killer cell-mediated cytotoxicity in acute myeloid leukemia patients

In some settings, cancer cells responding to treatment undergo an immunogenic form of cell death that is associated with the abundant emission of danger signals in the form of damage-associated molecular patterns. Accumulating preclinical and clinical evidence indicates that danger signals play a crucial role in the (re-)activation of antitumor immune responses in vivo, thus having a major impact on patient prognosis. We have previously demonstrated that the presence of calreticulin on the surface of malignant blasts is a positive prognostic biomarker for patients with acute myeloid leukemia (AML). Calreticulin exposure not only correlated with enhanced T-cell-dependent antitumor immunity in this setting but also affected the number of circulating natural killer (NK) cells upon restoration of normal hematopoiesis. Here, we report that calreticulin exposure on malignant blasts is associated with enhanced NK cell cytotoxic and secretory functions, both in AML patients and in vivo in mice. The ability of calreticulin to stimulate NK-cells relies on CD11c⁺CD14^high cells that, upon exposure to CRT, express higher levels of IL-15Rα, maturation markers (CD86 and HLA-DR) and CCR7. CRT exposure on malignant blasts also correlates with the upregulation of genes coding for type I interferon. This suggests that CD11c⁺CD14^high cells have increased capacity to migrate to secondary lymphoid organs, where can efficiently deliver stimulatory signals (IL-15Rα/IL-15) to NK cells. These findings delineate a multipronged, clinically relevant mechanism whereby surface-exposed calreticulin favors NK-cell activation in AML patients.

Abstract 3775: Use of RLI-15 a clinical grade fusion protein with IL-15 superagonistic activity for the activation of anti-tumor immune response

RLI-15, a superagonist fusion protein of interleukin (IL)-15 and the IL-15 receptor α (IL-15Rα) sushi+ domain represents a promising candidate for the induction of anti-tumor immunity. RLI-15 was designed to bypass the need of endogenous IL-15Rα, thereby leveraging the activity of IL-15 in vivo on target immune cells. RLI-15 stimulates the proliferation and the cytotoxic activity of natural killer (NK) cells and memory CD8+ T cells with no significant expansion and activation of regulatory T cell compartment. RLI-15 was previously shown to exhibit a potent anti-metastatic activity in B16F10 melanoma and Renca renal cell carcinoma mouse models. RLI-15 also significantly delayed tumor growth and prolonged survival when combined with anti-PD1 therapy in CT26 and MC38 colon carcinoma models. Here, we report that the combination treatment with clinical-grade RLI-15 and an anti-PD1 antibody leads to a significant anti-tumor efficacy in a TRAMP-C2 prostate cancer mouse model with 70 % of mice remaining tumor free after the treatment. We evaluated the optimal schedule of such combination therapy to set the basis for the design of upcoming clinical trials. We further tested how the administration schedule affects the pharmacodynamics properties of clinical-grade RLI-15 and translates into the anti-tumor efficacy in metastatic Renca and CT26 mouse models. In cynomolgous monkeys, various schedules of administration of RLI-15 showed a dose-dependent expansion of peripheral blood lymphocytes, predominantly of NK cell and memory CD8+ T cell compartments. The toxicity in mice and cynomolgous monkeys was evaluated to determine the maximal tolerated dose of RLI-15. Furthermore, the activity of clinical-grade RLI-15 was tested in vitro on human PBMCs and the superiority over IL-2 and IL-15 stimulatory capacity has been confirmed. The complex analysis of RLI-15 behavior and of the induced anti-tumor immune response will be explored in the design of a planned Phase I clinical study in patients with both solid tumors and hematological malignancies.

Citation Format: Irena Adkins, Lenka Sadilkova, Nada Hradilova, Jakub Tomala, Barbora Tomalova, Marek Kovar, Romana Mikyskova, Milan Reinis, Guy de Martynoff, David Bechard, Ulrich Moebius, Radek Spisek. Use of RLI-15 a clinical grade fusion protein with IL-15 superagonistic activity for the activation of anti-tumor immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3775.

Tumor growth accelerated by chemotherapy-induced senescent cells is suppressed by treatment with IL-12 producing cellular vaccines

Standard-of-care chemo- or radio-therapy can induce, besides tumor cell death, also tumor cell senescence. While senescence is considered to be a principal barrier against tumorigenesis, senescent cells can survive in the organism for protracted periods of time and they can promote tumor development. Based on this emerging concept, we hypothesized that elimination of such potentially cancer-promoting senescent cells could offer a therapeutic benefit. To assess this possibility, here we first show that tumor growth of proliferating mouse TC-1 HPV-16-associated cancer cells in syngeneic mice becomes accelerated by co-administration of TC-1 or TRAMP-C2 prostate cancer cells made senescent by pre-treatment with the anti-cancer drug docetaxel, or lethally irradiated. Phenotypic analyses of tumor-explanted cells indicated that the observed acceleration of tumor growth was attributable to a protumorigenic environment created by the co-injected senescent and proliferating cancer cells rather than to escape of the docetaxel-treated cells from senescence. Notably, accelerated tumor growth was effectively inhibited by cell immunotherapy using irradiated TC-1 cells engineered to produce interleukin IL-12. Collectively, our data document that immunotherapy, such as the IL-12 treatment, can provide an effective strategy for elimination of the detrimental effects caused by bystander senescent tumor cells in vivo.

Dendritic cells pulsed with tumor cells killed by high hydrostatic pressure inhibit prostate tumor growth in TRAMP mice

Dendritic cell (DC)-based vaccines pulsed with high hydrostatic pressure (HHP)-inactivated tumor cells have recently been shown to be a promising tool for prostate cancer chemoimmunotherapy. In this study, DC-based vaccines, both pulsed and unpulsed, were as effective as docetaxel (DTX) in reducing prostate tumors in the orthotopic transgenic adenocarcinoma of the mouse prostate (TRAMP) model. However, we did not observe any additive or synergic effects of chemoimmunotherapy on the tumor growth, while only the combination of DTX and pulsed dendritic cells resulted in significantly lower proliferation detected by Ki67 staining in histological samples. The DC-based vaccine pulsed with HHP-treated tumor cells was also combined with another type of cytostatic, cyclophosphamide, with similar results. In another clinically relevant setting, minimal residual tumor disease after surgery, administration of DC-based vaccines after the surgery of poorly immunogenic transplanted TRAMP-C2, as well as in immunogenic TC-1 tumors, reduced the growth of tumor recurrences. To identify the effector cell populations after DC vaccine application, mice were twice immunized with both pulsed and unpulsed DC vaccine, and the cytotoxicity of the spleen cells populations was tested. The effector cell subpopulations were defined as CD4⁺ and NK1.1⁺, which suggests rather unspecific therapeutic effects of the DC-based vaccines in our settings. Taken together, our data demonstrate that DC-based vaccines represent a rational tool for the treatment of human prostate cancer.

Dynamic alterations of bone marrow cytokine landscape of myelodysplastic syndromes patients treated with 5-azacytidine

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal stem cell disorders characterized by ineffective hematopoiesis frequently progressing into acute myeloid leukemia (AML), with emerging evidence implicating aberrant bone marrow (BM) microenvironment and inflammation-related changes. 5-azacytidine (5-AC) represents standard MDS treatment. Besides inhibiting DNA/RNA methylation, 5-AC has been shown to induce DNA damage and apoptosis in vitro. To provide insights into in vivo effects, we assessed the proinflammatory cytokines alterations during MDS progression, cytokine changes after 5-AC, and contribution of inflammatory comorbidities to the cytokine changes in MDS patients. We found that IL8, IP10/CXCL10, MCP1/CCL2 and IL27 were significantly elevated and IL12p70 decreased in BM of MDS low-risk, high-risk and AML patients compared to healthy donors. Repeated sampling of the high-risk MDS patients undergoing 5-AC therapy revealed that the levels of IL8, IL27 and MCP1 in BM plasma were progressively increasing in agreement with in vitro experiments using several cancer cell lines. Moreover, the presence of inflammatory diseases correlated with higher levels of IL8 and MCP1 in low-risk but not in high-risk MDS. Overall, all forms of MDS feature a deregulated proinflammatory cytokine landscape in the BM and such alterations are further augmented by therapy of MDS patients with 5-AC.

Interferon gamma/NADPH oxidase defense system in immunity and cancer

As a part of cellular pathogen defense, IFNγ triggers induction of NADPH oxidase NOX2, which produces superoxide into phagosomes of immune cells. Recent data show that a similar mechanism can also operate in IFNγ-mediated anticancer control. IFNγ is capable of inducing expression of constitutively active NADPH oxidase NOX4 in tumor cells leading to generation of reactive oxygen species (ROS) damaging DNA, activation of DNA damage response and cell cycle arrest/premature cellular senescence.

IFNγ induces oxidative stress, DNA damage and tumor cell senescence via TGFβ/SMAD signaling-dependent induction of Nox4 and suppression of ANT2

Cellular senescence provides a biological barrier against tumor progression, often associated with oncogene-induced replication and/or oxidative stress, cytokine production and DNA damage response (DDR), leading to persistent cell-cycle arrest. While cytokines such as tumor necrosis factor-alpha (TNFα) and interferon gamma (IFNγ) are important components of senescence-associated secretome and induce senescence in, for example, mouse pancreatic β-cancer cell model, their downstream signaling pathway(s) and links with oxidative stress and DDR are mechanistically unclear. Using human and mouse normal and cancer cell models, we now show that TNFα and IFNγ induce NADPH oxidases Nox4 and Nox1, reactive oxygen species (ROS), DDR signaling and premature senescence. Unlike mouse tumor cells that required concomitant presence of IFNγ and TNFα, short exposure to IFNγ alone was sufficient to induce Nox4, Nox1 and DDR in human cells. siRNA-mediated knockdown of Nox4 but not Nox1 decreased IFNγ-induced DDR. The expression of Nox4/Nox1 required Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling and the effect was mediated by downstream activation of transforming growth factor-beta (TGFβ) secretion and consequent autocrine/paracrine activation of the TGFβ/Smad pathway. Furthermore, the expression of adenine nucleotide translocase 2 (ANT2) was suppressed by IFNγ contributing to elevation of ROS and DNA damage. In contrast to mouse B16 cells, inability of TC-1 cells to respond to IFNγ/TNFα by DDR and senescence correlated with the lack of TGFβ and Nox4 response, supporting the role of ROS induced by NADPH oxidases in cytokine-induced senescence. Overall, our data reveal differences between cytokine effects in mouse and human cells, and mechanistically implicate the TGFβ/SMAD pathway, via induction of NADPH oxidases and suppression of ANT2, as key mediators of IFNγ/TNFα-evoked genotoxicity and cellular senescence.

Effects of 5-azacytidine and trichostatin A on dendritic cell maturation

Maturation of dendritic cells (DC) towards functional antigen-presenting cells is a complex process, the regulation of which may also involve epigenetic mechanisms. Thus, it is of interest to investigate how gene expression changes during DC maturation can be influenced with epigenetic agents, such as DNA methyltransferase or histone deacetylase inhibitors. Here, we document the effects of DNA methyltransferase inhibitor 5-azacytidine (5AC) and histone deacetylase inhibitor trichostatin A (TSA) on the murine bone marrow-derived, as well as on the human monocyte-derived DC maturation. The major impact of 5AC and TSA on the DC maturation process consisted in the inhibition of unmethylated CpG oligodeoxynucleotide (CpG ODN) 1826 or LPS-induced activation of pro- and anti-inflammatory cytokine gene expression activation. In the in vitro studies, TSA but not 5AC significantly reduced the capacity of the peptide-pulsed DC to induce total spleen as well as CD8(+) or CD4(+) cell proliferation. IFNγ production by the specific CD4(+) spleen cells co-cultured with TSA- but not with 5AC-treated DC was lower, as compared to the cytokine production after co-cultivation with untreated mature DC. Collectively, these results demonstrate the potential of epigenetic agents, which are under intensive investigation as promising anti-tumour agents, to hamper the immune response induction through their inhibitory effects on DC.

NK1.1+ cells are important for the development of protective immunity against MHC I-deficient, HPV16-associated tumours

Loss or downregulation of MHC class I molecules on tumour cells is a common mechanism by which tumours can escape T-cell mediated immune responses. In this study, we examined the role of different immune cell lineages in the development of immunity against tumours of the same aetiology but with different MHC class I expression. In vivo depletion of CD8+ cells, but not of CD4+ or NK1.1+ cells in the immunization period resulted in complete elimination of the protective effects of immunization with irradiated TC-1 cells (MHC class I-positive cell line) against the TC-1 tumour challenge. After immunization with irradiated TC-1/A9 or with MK16 tumour cells (MHC class I-deficient sublines) a remarkable dependence on the presence of NK1.1+ cells was observed, while the tumour growth inhibition after CD4+ or CD8+ depletion was not efficient. Cytotoxic activity induced by TC-1 cell immunization was significantly abrogated in the CD8+ and CD4+ but not NK1.1+ cell-depleted mice, as compared to the immunized only controls. After MK16 or TC-1/A9 cell immunization, NK1.1+ but not CD8+ and CD4+ cell-depleted mice displayed significant reduction of specific cytotoxicity. Mice immunized with TC-1 cells showed similar percentage of IFNγ producing cells in CD8+, CD4+ and NK1.1+ cell populations. On the other hand, the highest proportion of IFNγ producing cells after immunization with TC-1/A9 or MK16 cells was concentrated into the NK1.1-positive spleen cell population. Our data demonstrate that the development of immunity against MHC class I-deficient tumours is highly dependent on the activity NK1.1+ cell population.

Induction of protective immunity against MHC class I-deficient, HPV16-associated tumours with peptide and dendritic cell-based vaccines

Downregulation of MHC class I expression on the cell surface is a common mechanism by which tumour cells, including cervical carcinoma, can escape the T cell-mediated anti-tumour immunity. This downregulation represents an obstacle for the efficacy of anti-tumour vaccines. In this study, we investigated the efficacy of prophylactic peptide and peptide-pulsed dendritic cell-based vaccines in a murine model of experimental MHC class I-deficient tumours (TC-1/A9), expressing E6/E7 oncogenes derived from HPV16, and compared the efficacy of particular vaccination settings to anti-tumour protection against parental MHC class I-positive TC-1 tumours. Peptide vaccine based on the 'short' peptide E749-57 harbouring solely the CTL epitope and co-administered to the C57BL/6 mice with CpG oligodeoxynucleotide (CpG ODN) 1826 was effective against MHC class I-positive but not -deficient tumours, while the 'longer' peptide E744-62 (peptide 8Q, harbouring CTL and Th epitopes)-based vaccines were also effective against MHC class I-deficient tumours. We have compared the adjuvant efficacies of two CpG ODN, CpG ODN 1826 and CpG ODN 1585. The 8Q peptide immunisation combined with CpG ODN 1585 inhibited growth of the TC-1/A9 tumours more effectively as compared to CpG ODN 1826. Further, we investigated the efficacy of cellular vaccines based on ex vivo cultured dendritic cells pulsed with either E749-57 or E744-62 peptides and matured with CpG ODN 1826. Unlike in the peptide immunisation setting, treatment with dendritic cells pulsed with a 'short' peptide resulted in the tumour growth inhibition, albeit weaker as compared to the immunisation with the longer peptide. Our data demonstrate that peptide and dendritic cell-based vaccines can be designed to elicit protective immunity against MHC class I-deficient tumours.

Therapy for minimal residual tumor disease: beta-galactosylceramide inhibits the growth of recurrent HPV16-associated neoplasms after surgery and chemotherapy

Natural killer T (NKT) cells are potent modulators of antitumor immunity. Their protective effects can be achieved upon their activation by glycolipid ligands presented in the context of the CD1d molecule. These CD1d-binding glycolipid antigens have been described as potent therapeutic agents against tumors, infections, as well as autoimmune diseases. Immunoregulatory and therapeutic effects of glycolipid ligands depend on their structure and modes of administration. Therefore, more studies are needed for optimization of the particular therapeutic settings. This study was focused on the tumor-inhibitory effects of 12 carbon acyl chain beta-galactosyl ceramide (C12 beta-D-Galactosyl Ceramide; beta-GalCer(C12)) on the growth of human papillomavirus type 16 (HPV16)-associated neoplasms transplanted in syngeneic mice. Treatment of tumor-bearing mice with beta-GalCer(C12) 3-14 days after tumor cell transplantation significantly inhibited the growth of the major histocompatibility complex (MHC) Class I-positive (TC-1), as well as MHC Class I-deficient (TC-1/A9) HPV16-associated tumors. Moreover, administration of beta-GalCer(C12) after surgical removal of TC-1 tumors inhibited the growth of tumor recurrences. Similar results were obtained in the treatment of tumors after chemotherapy. beta-GalCer(C12) treatment turned out to be also synergistic with immunotherapy based on administration of IL-12-producing cellular vaccines. These results suggest that beta-GalCer(C12), whose antitumor effects have so far not been studied in detail, can be effective for the treatment of minimal residual tumor disease as well as an adjuvant for cancer immunotherapy.

Methods for viral RNA isolation and PCR amplification for sequencing of near full-length HIV-1 genomes

HIV-1 in plasma represents the viral quasispecies replicating in the patient at any given time. Studies of HIV-1 viral RNA from plasma or other body fluids therefore reflect the virus present in real time. To obtain near full-length genomic sequences derived from virion RNA it is first necessary to carefully isolate and amplify the RNA.The procedure described below, involves viral RNA extraction, reverse transcription (RT) of the extracted RNA to produce cDNA copies, and PCR amplification of long HIV-1 gene fragments using site-specific, overlapping primers. The primers are based on subtype B HIV-1 strains, and plasma specimens are used in the procedures. However, the protocol can easily be adapted to other HIV-1 subtypes by modifying the primers to match the subtype of interest.

HPV 16-associated tumours: IL-12 can repair the absence of cytotoxic and proliferative responses of tumour infiltrating cells after chemotherapy

We have examined the effect of IL-12-producing cellular vaccines on the cytotoxicity and proliferative potential of CD45+ tumour-infiltrating cells (TIL) in mice carrying syngeneic TC-1 and TC-1/A9 HPV 16-associated tumours after chemotherapy with CBM-4A ifosfamide derivative. The chemotherapy resulted in the decrease of the CD4+ and CD8+ TIL, increase of the Gr-1+/CD11b+ TIL, no changes in the infiltration with CD4+/CD25+ Treg TIL, and decrease of the cytolytic and proliferative potential of the CD45+ TIL. Subsequent immunotherapy with the IL-12-producing, genetically modified TC-1 (TC-1-IL-12) cells increased tumour infiltration with CD8+ and CD4+ cells, decreased the Gr-1+/CD11b+ cells, and increased the cytolytic and proliferative potential of the CD45+ TIL. Taken together, these findings suggest that peritumoral administration of the IL-12-producing cellular vaccine can restore the cytolytic potential and inhibit immunosuppressive TIL-dependent mechanisms in the individuals bearing HPV 16-associated tumours, and explain our previously described tumour-inhibitory effects of the vaccine in mice with minimal residual disease after the tumour chemotherapy.

BiovaxID, a personalized therapeutic vaccine against B-cell lymphomas

Biovest International Inc (a subsidiary of Accentia BioPharmaceuticals Inc), under license from Stanford University, is developing BiovaxID, a personalized therapeutic vaccine against B-cell lymphomas that, in combination with GM-CSF, exclusively targets cancerous B-cells by raising an immune response to tumor-specific immunoglobulin proteins called idiotypes, for the potential treatment of follicular non-Hodgkin's lymphoma (NHL). Phase I and II clinical trials demonstrated the immunogenicity, safety and therapeutic efficacy of BiovaxID. Phase III clinical trials in NHL were ongoing at the time of publication.

Glycopeptide dendrimers, part III: a review. Use of glycopeptide dendrimers in immunotherapy and diagnosis of cancer and viral diseases

Glycopeptide dendrimers containing different types of tumor associated-carbohydrate antigens (T(N), TF, sialyl-T(N), sialyl-TF, sialyl-Le(x), sialyl-Le(a) etc.) were used in diagnosis and therapy of different sorts of cancer. These dendrimeric structures with incorporated T-cell epitopes and adjuvants can be used as antitumor vaccines. Best results were obtained with multiantigenic vaccines, containing, e.g. five or six different TAAs. The topic of TAAs and their dendrimeric forms at molecular level are reviewed, including structure, syntheses, and biological activities. Use of glycopeptide dendrimers as antiviral vaccines against HIV and influenza is also described. Their syntheses, physico-chemical properties, and biological activities are given with many examples.

IL-12 immunotherapy of minimal residual disease in murine models of HPV16-associated tumours: induction of immune responses, cytokine production and kinetics of immune cell subsets

We have established animal models of HPV16-associated tumours with distinct levels of MHC class I expression. This model was used for examination of immune responses, production of cytokines and kinetics of immune cell subsets after IL-12 therapy of minimal residual tumour disease induced by CBA-4A (cyclophosphamide derivative) treatment. Upregulation of cytokine production was detected, compared to control animals without tumours. No differences in Th1/Th2 polarization of the immune responses after immunotherapy in animals bearing tumours with different surface expression of MHC class I molecules were observed. In the spleens of TC-1 (MHC class I+) but not of TC-1/A9 (MHC class I-) treated tumour-bearing animals, the cytotoxic CD8+ cells detectable in 51Cr microcytotoxicity assay, were found. In the spleens of TC-1/A9 but not of TC-1 tumour-treated animals, the NK activity measured as the lysis of NK-sensitive YAC-1 targets was detected. Down-regulation of the CD4+ and CD8+ subpopulations in spleens of tumour-bearing animals were not restored after therapy. The percentage of CD25+/CD4+ T regulatory (Treg) cells in lymph nodes remained unchanged. The cytoreductive chemotherapy led to strong upregulation and accumulation of immunosuppressive immature myeloid Gr-1+/CD11b+ cells (IMC) in the spleens of treated animals. The accumulation of Gr-1+/CD11b+ cells was significantly decreased after subsequent IL-12 immunotherapy. These data suggest that elimination of IMC after IL-12 immunotherapy may be responsible for the improvement of antitumour responses after adjuvant IL-12 vaccination for the treatment of CMRTD.

Induction of MHC class I molecule cell surface expression and epigenetic activation of antigen-processing machinery components in a murine model for human papilloma virus 16-associated tumours

Epigenetic events play an important role in tumour progression and also contribute to escape of the tumour from immune surveillance. In this study, we investigated the up-regulation of major histocompatibility complex (MHC) class I surface expression on tumour cells by epigenetic mechanisms using a murine tumour cell line expressing human E6 and E7 human papilloma virus 16 (HPV16) oncogenes and deficient in MHC class I expression, as a result of impaired antigen-presenting machinery (APM). Treatment of the cells with the histone deacetylase inhibitor Trichostatin A, either alone or in combination with the DNA demethylating agent 5-azacytidine, induced surface re-expression of MHC class I molecules. Consequently, the treated cells became susceptible to lysis by specific cytotoxic T lymphocytes. Further analysis revealed that epigenetic induction of MHC class I surface expression was associated with the up-regulation of APM genes [transporter associated with antigen processing 1 (TAP-1), TAP-2, low-molecular-mass protein 2 (LMP-2) and LMP-7]. The results demonstrate that expression of the genes involved in APM are modulated by epigenetic mechanisms and suggest that agents modifying DNA methylation and/or histone acetylation have the potential to change the effectiveness of antitumour immune responses and therapeutically may have an impact on immunological output.

Drug evaluation: FavId, a patient-specific idiotypic vaccine for non-Hodgkin's lymphoma

Favrille Inc is developing FavIld, a patient-specific immunotherapy combining tumor-specific idiotype protein and keyhole limpet hemocyanin, for the potential treatment of lymphoma. A phase III clinical trial in follicular B-cell non-Hodgkin's lymphoma is underway.

CpG oligodeoxynucleotides are effective in therapy of minimal residual tumour disease after chemotherapy or surgery in a murine model of MHC class I-deficient, HPV16-associated tumours

Oligodeoxynucleotides containing guanine-cytidine dimers (CpG ODN) are potent inducers of anti-tumour immune responses. In this study, we analyzed the capacity of CpG ODN to inhibit the growth of both MHC class I-positive and -deficient tumours after debulking the tumour mass by chemotherapy or surgery. We employed an animal model resembling human papillomavirus (HPV) 16-associated tumours. Tumour cell lines with distinct cell surface expression of the MHC class I molecules were injected into syngeneic C57BL/6 mice, and the growing tumours were either subjected to cytoreductive chemotherapy with ifosfamide derivative, CBM-4A, or surgically removed. Subsequent treatment with synthetic CpG ODN significantly blocked the growth of the recurrent tumours. Our results indicate that the therapy with CpG ODN can be effective for the treatment of minimal residual tumour disease of the tumours that have escaped from the immune surveillance by downmodulating the MHC class I expression.

Immunization with MHC class I-negative but not -positive HPV16-associated tumour cells inhibits growth of MHC class I-negative tumours

Loss or downregulation of MHC class I molecules on tumour cells is a common mechanism by which tumours can escape from T-cell mediated immune responses. In this study we have investigated the immunologic crossreactivity between murine tumour cell lines expressing human papilloma virus (HPV) 16-derived E6/E7 oncoproteins with distinct surface expression of MHC class I molecules. The aims of this study were to demonstrate whether immune responses capable of coping with MHC class I-positive tumours can also be effective against their MHC class I-deficient derivatives and whether it is possible to induce immunity against MHC class I-deficient tumours by cellular vaccines based on MHC class I-deficient tumour cell lines. Our data showed that immunization with MHC class I-deficient but not with MHC class I positive tumour cells inhibited the growth of MHC class I-deficient tumours. In vivo depletion studies revealed that the mechanisms underlying effective immune responses against MHC class I-negative tumours in animals immunized with MHC class I-deficient tumour cells involved natural killer cells. The presented findings are of particular clinical relevance in the sense of construction of vaccines directed against a broad spectrum of HPV-associated tumours.

Genomic analysis of HIV type 1 strains derived from a mother and child pair of long-term nonprogressors

To investigate the viral features of long-term nonprogressive HIV-1 infection and the selection of viral genomes, we studied serial complete HIV-1 sequences obtained from a mother-child pair, both long-term nonprogressors. Analysis of four genomic sequences demonstrated that all viral genes were intact, lacking major deletions or premature stop codons to easily explain the slow disease progression. These data suggest that viral attenuation, if present, was caused by subtle sequence variations or virus-host interactions. Serial sequences from an HIV-1-infected mother-child pair afforded us the opportunity to examine the immune selection of HIV-1 sequences years after transmission between individuals. We demonstrated that the daughter's strains were most likely subjected to immunoselection or immunoediting according to the presence of novel MHC class I alleles that differed between mother and daughter. An analysis of nef-specific cytotoxic T-lymphocyte responses in the child, whose HIV-1 nef sequence differed from the maternal nef, supported this interpretation. This study highlights the potential of full genome analysis in the investigation of pathogenesis and immune selection during HIV-1 evolution.

Depletion of T(reg) cells inhibits minimal residual disease after surgery of HPV16-associated tumours

It is generally accepted that T regulatory cells (T(reg) CD4(+)CD25(+)Foxp3(+)) play an important role in the suppression of tumour immunity. We examined the impact of T(reg) cell depletion with anti-CD25 antibody as adjuvant therapy in the treatment of minimal residual disease after excision of murine HPV16-associated tumours. We found that the depletion of T(reg) cells inhibited growth of the recurrences after surgery of HPV16-associated MHC class I+ as well as MHC class I-deficient tumours transplanted in syngeneic mice. These results demonstrate that depletion of CD25(+)CD4(+) T(reg) cells can be used as an efficient adjuvant treatment improving the results of surgery in the experimental systems mimicking human MHC class I+ and MHC class I-deficient, HPV16-associated neoplasms. Therefore, this therapeutic modality is worth being examined in patients with minimal residual HPV16-associated tumour disease after surgery.

Inhibitory effects of unmethylated CpG oligodeoxynucleotides on MHC class I-deficient and -proficient HPV16-associated tumours

Unmethylated oligodeoxynucleotides containing guanine-cytidine dimers (CpG ODN) have been described as potent inducers of selected antitumour immune responses and the immunotherapeutic efficacy of CpG ODN has been examined either alone or as a vaccine adjuvant. We hypothesized that CpG ODN therapy could be an effective tool for immunotherapy of not only conventional MHC class I(+) tumours but also of those tumours that have lost MHC class I expression during their progression. To address this hypothesis, we employed the animal model resembling MHC class I-proficient and -deficient human papilloma virus (HPV) 16-associated tumours. A cell line transformed with HPV16 E6 and E7 oncogenes, TC-1, as a prototype of MHC class I-positive line, and its MHC class I-deficient sublines TC-1/A9 and TC-1/P3C10 were injected into syngeneic C57BL/6 mice and the growing tumours were subjected to immunotherapy with CpG ODN 1826. The therapy started either 1 day after the challenge with the tumour cells or later, when the tumours had reached a palpable size. In both settings, CpG ODN 1826 significantly reduced the growth of MHC class I-proficient and -deficient tumours. Furthermore, we demonstrated that CpG ODN 1585, whose mechanism of action preferably involves indirect activation of the natural killer cells, induced regression of the MHC class I-deficient tumours TC1/A9 but not of the MHC class I-proficient tumours TC-1. This study infers that synthetic CpG ODN have a potential for the therapy of both MHC class I-proficient and -deficient tumours and thus could be also used against tumours that tend to down-regulate their MHC class I expression.

nef gene sequence variation among HIV-1-infected African children*

BACKGROUND

There are few data on African children infected with nonclade B HIV-1 in endemic settings, which limits generalizations about pathogenesis and progression. Genotypic and phenotypic variations in host immunogenetics and HIV-1 negative factor (nef) accessory protein may influence disease progression and have frequently been characterized in subjects infected with clade B HIV-1.

METHODS

In this descriptive study, we report nef gene sequence variation and host genetic polymorphisms in 32 Kenyan children, including 12 slow progressors.

RESULTS

Phylogenetic analysis identified HIV-1 clades A, C and D and a recombinant A/D subtype. Grossly defective nef genes or significant changes from relevant clade reference sequences were not identified in children with delayed disease progression.

CONCLUSIONS

nef sequence variations may not be common in perinatally infected African children. Further studies are warranted in HIV-1-infected subjects in settings where infection is endemic.

Chemotherapy, IL-12 gene therapy and combined adjuvant therapy of HPV 16-associated MHC class I-proficient and -deficient tumours

Moderately immunogenic HPV 16-associated murine tumour cell line mimicking human HPV 16-associated neoplasms TC-1 (MHC class I(+)) and its variants, TC-1/P3C10 and TC-1/A9, with a marked down-regulation of MHC I molecules, were used to examine the effect of local interleukin 12 (IL-12) gene therapy for the treatment of early tumour transplants and minimal residual tumour disease obtained after cytoreductive chemotherapy (CMRTD). Experiments were designed to examine whether down-regulation of MHC class I molecules plays a role during chemotherapy and gene therapy of early tumour transplants. It was found that peritumoral administration of IL-12-producing tumour cell vaccines (single dose, day 8 after tumour cell administration) inhibited the growth of both TC-1 (MHC class I positive) tumours and their MHC class I-deficient variants. To investigate the antitumour effects in a clinically relevant setting, IL-12 gene therapy was utilised for the treatment of minimal residual tumour disease after cytoreductive chemotherapy. Intra-peritoneal treatment of tumour-bearing mice with ifosfamide derivative, CBM-4A, produced a significant tumour-inhibitory effect. This treatment was followed by peritumoral s.c. administration of genetically modified TC-1 (MHC class I positive) or MK16/I/IIIABC (MHC class I negative) vaccines producing IL-12 (single dose, day 7 after chemotherapy) or with recombinant interleukin 12 (rIL-12) in two cycles of 5 daily doses (days 8-19) after chemotherapy. This combined therapy significantly inhibited the growth of TC-1 and TC-1/A9 (MHC class I-) tumours. When the combined therapy of TC-1 (MHC class I positive) tumours was followed by peritumoral administration of bone marrow dendritic cell (BMDC) vaccines, the IL-12-mediated inhibitory effect was significantly boosted. In the next set of experiments, the impacts of chemotherapy and IL-12 adjuvant therapy on MHC class I surface expression were assessed. Chemotherapy and gene therapy of tumours led to the up-regulation of MHC I expression on MHC class I-deficient tumours (TC-1/A9 and TC-1/P3C10) and to down-regulation on MHC I-proficient tumours (TC-1). These findings indicate that the MHC I phenotype is not stable during tumour progression and treatment. Collectively, these results illustrate the efficacy of IL-12 gene therapy in combination with chemotherapy on HPV-associated tumours regardless of the level of MHC class I expression on the tumour cells.

Technology evaluation: NV-1020, MediGene

NV-1020 is a recombinant oncolytic HSV-based virus, in development by MediGene (formerly NeuroVir) for the potential treatment of cancer. The therapy is currently undergoing phase II clinical trials.

Long-term analysis of the resistance development in HIV-1 positive patients treated with protease and reverse transcriptase inhibitors: correlation of the genotype and disease progression

In this study, 27 HIV-1-positive patients on long-term highly active antiretroviral therapy (HAART) in the Czech Republic were followed for a period of up to 7 years. Variability of the HIV-1 protease (PR) sequence common in the Czech Republic was observed. Under the pressure of inhibitors of protease (PRIs) and reverse transcriptase (RTIs) mutations in PR were detected. Development of resistance to PRIs was followed by a decrease in CD4 count and increase in viral load. The dynamics of viral load closely corresponded to the accumulation of specific primary mutations in PR and RT. Out of 27 patients 18 developed resistance to PRIs and the prolonged therapy led to the accumulation of a higher number of amino acid changes associated with the resistance and, consequently, cross-resistance to several PRIs was observed. These multi-resistant variants of HIV-1 with mutations in PR could not be inhibited sufficiently with PRIs that are currently available in clinical practice. Efficient yet temporary suppression of viral replication was achieved by a lopinavir (LPV) treatment.

HPV16-associated tumours: therapy of surgical minimal residual disease with dendritic cell-based vaccines

Dendritic cell (DC)-based vaccines are being intensively investigated for the treatment of a variety of human neoplasms. However, little attention has until now been paid to the use of DC-based vaccines for immunotherapy of tumour residua after surgery. In this communication, an animal model mimicking human HPV16-associated neoplasms was employed to examine the effect of DC-based vaccines for the treatment of surgical minimal residual tumour disease. Mice were subcutaneously inoculated with syngeneic TC-1 tumour cells of HPV16 origin. When the tumours reached approximately 1 cm in diameter, they were surgically removed and the operated mice were injected into the site of the operation with bone marrow-derived DC, which were either pulsed with TC-1 cell lysates or co-cultured with irradiated TC-1 cells. It has been found that the growth of TC-1 tumour recurrences in the mice treated with these vaccines was substantially suppressed, as compared to the operated-only controls. The phenotypic analysis of the spleen cells has shown that the percentage of CD3+ cells was diminished in the operated-only and vaccinated mice carrying recurrent tumours, in comparison with healthy control mice and with operated tumour-free mice. Moreover, accumulation of immature myeloid cells (CD11b+/Gr-1+) was observed in spleens of the tumour-bearing mice. These findings indicate that the immune system of the tumour-bearing individuals was compromised, as compared to that of normal individuals or tumour regressors. To our knowledge, this is the first report that has demonstrated the positive effect of local administration of the DC-based, HPV16 E6/E7 oncoprotein-containing, tumour lysate-loaded vaccines in the treatment of surgical minimal residual tumour disease.

Technology evaluation: TroVax, Oxford BioMedica

TroVax, a gene-based tumor vaccine that uses a poxvirus vector to deliver the tumor antigen gene 5T4, is under development by Oxford BioMedica for the potential treatment of cancer. TroVax is undergoing phase II clinical trials.

Technology evaluation: HPV vaccine (quadrivalent), Aventis Pasteur MSD/CSL

CSL, licensee of UniQuest's HPV technology, and Aventis Pasteur MSD (a joint venture between Merck & Co and Aventis) are jointly developing a vaccine for the potential prophylaxis of genital warts and cervical cancer caused by human papilloma virus infection. Enrollment for a phase III trial has been completed.

Immunogenicity of dendritic cell-based HPV16 E6/E7 peptide vaccines: CTL activation and protective effects

We have investigated the capacity of cellular vaccines based on dendritic cells loaded with human HPV16 E6/E7 oncoprotein-derived peptides to induce immune responses in vitro and to elicit protective immunity in a murine experimental model mimicking human HPV16-associated carcinomas. Dendritic cells loaded with the HPV16 E6/E7 peptides exhibiting CTL or Th epitopes (E6(41-50), E6(81-90), E6(98-107), E6(130-137), E7(49-57), and E7(44-62)) were able to stimulate in vitro DNA synthesis in syngeneic H-2b spleen cells. The priming capacity of peptide-loaded BMDC and peptide-loaded dendritic cell lines DC2.4 and JAWS II was compared. It has been found that both peptide-loaded BMDC and established dendritic cell lines can activate the syngeneic responder cells, but the priming capacity of BMDC was substantially higher. In the second set of experiments, we have examined the cytolytic activity of syngeneic spleen cells after repeated activation in vitro with BMDC loaded with HPV16 synthetic peptides containing CTL epitopes. Significant cytotoxic responses against HPV16 E6/E7 antigen-expressing TC-1 targets have been found after repeated in vitro activation with all peptides containing the CTL epitopes. In contrast, peptide E7(44-62) harbouring both Th and CTL epitopes induced significant cytotoxic responses already after single in vitro activation. This cytotoxic effect could be enhanced with admixture of the E7(49-57) peptide. Experiments with MHC class I proficient (TC-1, MK16-IFNgamma) and deficient (MK16) target cells revealed that the dendritic cells loaded with the E6/E7 HPV16 peptides activated CTLs in vitro, but not the other cytolytic effector mechanisms. The effectiveness of the peptide-loaded BMDC-based cellular vaccines was also investigated in vivo. C57BL/6 (H-2b) mice were immunized with various peptide-loaded BMDC and subsequently challenged with TC-1 cells. The strongest protective effect was achieved with the BMDC loaded with the peptide E7(44-62) harbouring both CTL and Th epitopes. Mice immunized with the E7(44-62) peptide remained tumour-free after s.c. transplantation of the TC-1 cells and exhibited long-lasting protective immunity, whereas the mice immunized with E6(81-90) and E7(49-57) peptides did not remain tumour-free and exhibited only partial inhibition of tumour growth detectable as depression of the tumour growth curves.

Human immunodeficiency virus 1 strains resistant to nucleoside inhibitors of reverse transcriptase in isolates from the Czech Republic as monitored by line probe assay and nucleotide sequencing

The genetic resistance to nucleoside inhibitors of the reverse transcriptase (RT) of human immunodeficiency virus I (HIV-1) isolates in the Czech Republic was examined by a line probe assay (LiPA) and nucleotide sequencing. The results of LiPA analysis of 294 blood specimens obtained from 156 patients revealed a high incidence of mutations in the RT gene related to resistance to various drugs (67.3%) in various combinations. Mutations in RT gene (M41L, K70R and T215Y/F) conferring the resistance to zidovudine (ZDV) were most frequent (62.6%), that (M184V) responsible for the resistance to lamivudine (3TC) was less frequent (33.7%), while those linked to the resistance to dideoxyinosine (ddl) and dideoxyinosine together with dideoxycytidine (ddl/ddC) were rather rare (6.5% and 5.1%, respectively). LiPA gave a high rate of uninterpretable results due to codon hybridization failure, especially in HIV-1 isolates of non-B subtype. Thirty-two specimens were analyzed also by direct sequencing of a part of RT gene. The results obtained by LiPA and the sequencing were highly concordant for codons successfully analyzed by both methods, but the sequencing provided information also about the codons that could not be analyzed by LiPA. A high prevalence of resistant strains in the Czech Republic and their heterogeneity justifies a regular HIV-1 resistance testing. LiPA turned out as a fast, powerful and most reliable tool for such a purpose. However, due to an increasing diversity of HIV-1 strains circulating in the Czech Republic, LiPA cannot replace the nucleotide sequence analysis.

HIV-1-specific CD8 T cell responses in a pediatric slow progressor infected as a premature neonate

We describe the long-term survival of an individual infected with HIV-1 during extrauterine life as a premature newborn. In the absence of viral attenuation in the Nef/LTR structure or significant co-receptor polymorphisms, slow progression was associated with the strong HIV-1-specific broadly cross-reactive CD8 T cell responses. HIV-1 infection as early as 25 weeks' gestation may thus results in the development of immune responses that control viral replication and lead to prolonged survival.