T-cell epitope analogues from carcinoembryonic antigen for vaccination against cancer: WO2009002418.

BACKGROUND: Cancer is one of the leading causes of death in the Western world. Therapeutic vaccination to target minimal residual disease or prevent tumor recurrence represents an interesting and novel alternative for treatment of tumor diseases. T-cell peptide epitopes are commonly used as vaccine candidates for the induction of antitumor immune responses. By modifying the amino-acid sequence of the peptide at certain, so-called anchor positions, the binding affinity to MHC class I and the immunogenicity of the peptide can be improved. Vaccination with the modified peptide analogue can then be used to induce an immune response to the wild-type epitope. METHOD: The present application concerns the use of peptides representing wild-type T-cell epitopes and analogues from carcinoembryonic antigen for vaccination against cancer. The stated claims also include the use of these epitopes in several other vaccine modalities, including RNA, DNA and adenoviral vector vaccines. CONCLUSION: Although the available data clearly support the basic claims that some of the peptide analogues indeed are able to induce a potent immune response in mice to the corresponding wild-type epitopes, the lack of in vivo antitumor data for any of the covered vaccine modalities prevents a thorough evaluation of the stated claims.

Late administration of plasmid DNA by intradermal electroporation efficiently boosts DNA-primed T and B cell responses to carcinoembryonic antigen.

Heterologous boost immunisation is considered the most efficient way to enhance DNA-primed immune responses. We have previously shown that administration of recombinant carcinoembryonic antigen (CEA) efficiently boosts humoral responses in mice primed with CEA DNA. However, clinical grade recombinant proteins are far more intriguing to produce than plasmid DNA. Therefore, the possibility to use plasmid DNA for both priming and boosting would be beneficial. With the prospect of future use in a clinical trial, we investigated if electroporation-mediated delivery of DNA could be used to boost DNA-primed immune responses to CEA. The Biojector was used to prime BALB/c mice intradermally three times with CEA66 DNA, encoding an intracellular modified form of CEA. Twelve weeks after the last prime, the animals received either one injection of recombinant CEA or one intradermal injection of twtCEA DNA, encoding the wild type CEA fused to a tetanus T helper epitope, in combination with electroporation. Boosting with rCEA protein did not enhance T cell responses to CEA but induced CEA-specific IgG in 4 of 8 mice. In contrast, intradermal delivery of twtCEA DNA by electroporation led to a tenfold increase in IFN-gamma-producing CD8+ T cells, compared to the levels obtained after the third priming immunisation. The DNA boost also induced high CEA-specific IgG titers in all immunised animals (8/8). The data suggests that a late DNA boost, in combination with enhanced DNA delivery by electroporation, could be used to enhance the efficiency of DNA vaccination and substitute for a heterologous protein boost vaccination.

Modulation of the tumor cell phenotype by IFN-gamma results in resistance of uveal melanoma cells to granule-mediated lysis by cytotoxic lymphocytes.

IFN-gamma, a pleiotropic immune regulator, is implicated in both tumor immune surveillance and selection of tumor variants resistant to immune control, i.e., immunoediting. In uveal melanoma patients, elevated serum levels of IFN-gamma correlate with the spread of metastasis and represent a negative prognostic marker. Treatment with IFN-gamma boosted the MHC class I presentation machinery in uveal melanoma cells but suppressed their MHC class I-restricted CTL lysis. Tumor cells exposed to IFN-gamma efficiently activated specific CTL but were less susceptible to permeabilization by perforin and exhibited a decreased capacity to bind and incorporate granzyme B. These results define a novel mechanism of resistance to granule-mediated CTL lysis in human tumors. Furthermore, the data suggest that immunoediting is not limited to genetic or epigenetic changes resulting in stable cellular phenotypes but also involves an inducible modulation of tumor cells in response to a microenvironment associated with immune activation.

Immunization of mice with the nef gene from Human Immunodeficiency Virus type 1: study of immunological memory and long-term toxicology.

BACKGROUND: The human immunodeficiency virus type 1 (HIV-1) regulatory protein, Nef, is an attractive vaccine target because it is involved in viral pathogenesis, is expressed early in the viral life cycle and harbors many T and B cell epitopes. Several clinical trials include gene-based vaccines encoding this protein. However, Nef has been shown to transform certain cell types in vitro. Based on these findings we performed a long-term toxicity and immunogenicity study of Nef, encoded either by Modified Vaccinia virus Ankara or by plasmid DNA. BALB/c mice were primed twice with either DNA or MVA encoding Nef and received a homologous or heterologous boost ten months later. In the meantime, the Nef-specific immune responses were monitored and at the time of sacrifice an extensive toxicological evaluation was performed, where presence of tumors and other pathological changes were assessed. RESULTS: The toxicological evaluation showed that immunization with MVAnef is safe and does not cause cellular transformation or other toxicity in somatic organs.Both DNAnef and MVAnef immunized animals developed potent Nef-specific cellular responses that declined to undetectable levels over time, and could readily be boosted after almost one year. This is of particular interest since it shows that plasmid DNA vaccine can also be used as a potent late booster of primed immune responses. We observed qualitative differences between the T cell responses induced by the two different vectors: DNA-encoded nef induced long-lasting CD8+ T cell memory responses, whereas MVA-encoded nef induced CD4+ T cell memory responses. In terms of the humoral immune responses, we show that two injections of MVAnef induce significant anti-Nef titers, while repeated injections of DNAnef do not. A single boost with MVAnef could enhance the antibody response following DNAnef prime to the same level as that observed in animals immunized repeatedly with MVAnef. We also demonstrate the possibility to boost HIV-1 Nef-specific immune responses using the MVAnef construct despite the presence of potent anti-vector immunity. CONCLUSION: This study shows that the nef gene vectored by MVA does not induce malignancies or other adverse effects in mice. Further, we show that when the nef gene is delivered by plasmid or by a viral vector, it elicits potent and long-lasting immune responses and that these responses can be directed towards a CD4+ or a CD8+ T cell response depending on the choice of vector.

Intracellular targeting of CEA results in Th1-type antibody responses following intradermal genetic vaccination by a needle-free jet injection device.

The route and method of immunization, as well as the cellular localization of the antigen, can influence the generation of an immune response. In general, intramuscular immunization results in Th1 responses, whereas intradermal delivery of DNA by gene gun immunization often results in more Th2 responses. Here we investigate how altering the cellular localization of the tumor antigen CEA (carcinoembryonic antigen) affects the quality and amplitude of DNA vaccine-induced antibody responses in mice following intradermal delivery of DNA by a needle-free jet injection device (Biojector). CEA was expressed either in a membrane-bound form (wild-type CEA) or in two truncated forms (CEA6 and CEA66) with cytoplasmic localization, where CEA66 was fused to a promiscuous T-helper epitope from tetanus toxin. Repeated intradermal immunization of BALB/c mice with DNA encoding wild-type CEA produced high antibody titers of a mixed IgG1/IgG2a ratio. In contrast, utilizing the DNA construct that resulted in intracellular targeting of CEA led to a reduced capacity to induce CEA-specific antibodies, but instead induced a Th1-biased immune response.

Immunization with HIV protease peptides linked to syngeneic erythrocytes.

New potent vaccine adjuvants are desirable for increasing the efficacy of novel vaccine modalities such as DNA and peptides. We therefore tested if syngeneic erythrocytes could serve as delivery vectors for selected HIV peptides and compared the potency of these constructs to immunization with peptides in phosphate buffered saline or in incomplete Freunds adjuvant. Immunization of mice with peptides in a low dose (5 ng) coupled to erythrocytes induced a weak immune response in mice. These peptides alone (5 microg) gave no immune responses, while formulating the peptides (50 microg) in IFA induced strong homologous immunity as well as prominent cross reactivity to a related mutant epitope. Thus, vaccine delivery using syngeneic erythrocytes, although attractive for clinical use, might be of limited value due to the low amount of antigen that can be loaded per erythrocyte.

Autocrine secretion of Fas ligand shields tumor cells from Fas-mediated killing by cytotoxic lymphocytes.

Mechanisms responsible for resistance of tumors to death receptor-mediated damage by cytotoxic lymphocytes are not well understood. Uveal melanoma cells expressed Fas but were insensitive to Fas triggering induced by bystander cytotoxic T lymphocytes or a Fas-specific agonistic antibody; this could not be ascribed to tumor counterattack against T cells or general resistance of the tumors to apoptosis. Treatment with inhibitors of metalloproteases rendered uveal melanomas sensitive to Fas-mediated cytotoxicity. Metalloprotease inhibitors did not affect the expression of Fas but increased the surface expression of Fas ligand (FasL), which correlated with the disappearance of soluble FasL from culture supernatants of tumor cells. FasL eluted from the surface of uveal melanomas specifically inhibited cytotoxic T lymphocyte lysis of tumor cells pretreated with an inhibitor of metalloproteases. In addition to uveal melanomas, a number of other tumor cell lines of various cellular origins were sensitized to Fas-mediated cytotoxicity by metalloprotease inhibitors. Our results show that autocrine secretion of FasL shields tumor cells from Fas-mediated killing by cytotoxic lymphocytes. This defines a novel mechanism of tumor escape from immune surveillance.