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Unique potential of 4-1BB agonist antibody to promote durable regression of HPV+ tumors when combined with an E6/E7 peptide vaccine.

ABSTRACT: Antibody modulation of T-cell coinhibitory (e.g., CTLA-4) or costimulatory (e.g., 4-1BB) receptors promotes clinical responses to a variety of cancers. Therapeutic cancer vaccination, in contrast, has produced limited clinical benefit and no curative therapies. The E6 and E7 oncoproteins of human papilloma virus (HPV) drive the majority of genital cancers, and many oropharyngeal tumors. We discovered 15-19 amino acid peptides from HPV-16 E6/E7 for which induction of T-cell immunity correlates with disease-free survival in patients treated for high-grade cervical neoplasia. We report here that intranasal vaccination with these peptides and the adjuvant alpha-galactosylceramide elicits systemic and mucosal T-cell responses leading to reduced HPV(+) TC-1 tumor growth and prolonged survival in mice. We hypothesized that the inability of these T cells to fully reject established tumors resulted from suppression in the tumor microenvironment which could be ameliorated through checkpoint modulation. Combining this E6/E7 peptide vaccine with checkpoint blockade produced only modest benefit; however, coadministration with a 4-1BB agonist antibody promoted durable regression of established genital TC-1 tumors. Relative to other therapies tested, this combination of vaccine and α4-1BB promoted the highest CD8(+) versus regulatory FoxP3(+) T-cell ratios, elicited 2- to 5-fold higher infiltration by E7-specific CTL, and evoked higher densities of highly cytotoxic TcEO (T cytotoxic Eomesodermin) CD8 (>70-fold) and ThEO (T helper Eomesodermin) CD4 (>17-fold) T cells. These findings have immediate clinical relevance both in terms of the direct clinical utility of the vaccine studied and in illustrating the potential of 4-1BB antibody to convert therapeutic E6/E7 vaccines already in clinical trials into curative therapies.

SUBMITTER: Bartkowiak T

PROVIDER: S-EPMC4586868 | biostudies-other | 2015 Sep

REPOSITORIES: biostudies-other

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Project description:BackgroundHuman Papillomavirus type 16 (HPV16) has been associated with a subset of head and neck cancers. Two HPV encoded oncogenic proteins, E6 and E7, are important for the malignant progression of HPV-associated cancers. A spontaneous HPV16 E6/E7-expressing oral tumor model in human HLA-A2 (AAD) transgenic mice will be important for the development of therapeutic HPV vaccines for the control of HPV-associated head and neck cancers.MethodsIn the current studies, we characterized the HLA-A2 restricted HPV16 E7-specific CD8 + T cell mediated immune responses in the HLA-A2 (AAD) transgenic mice using a therapeutic naked DNA vaccine encoding calreticulin (CRT) linked to a mutated E7(N53S). We also employed oncogenic DNA plasmids that encoded HPV16E6/E7/Luc, NRasG12V, and sleeping beauty transposase for the transfection into the submucosal of oral cavity of the transgenic mice with electroporation to create a spontaneous oral tumor. Furthermore, we characterized the therapeutic antitumor effects of CRT/E7(N53S) DNA vaccine using the spontaneous HPV16 E6/E7-expressing oral tumor model in HLA-A2 (AAD) transgenic mice.ResultsWe found that CRT/E7(N53S) DNA vaccine primarily generated human HPV16 E7 peptide (aa11-20) specific CD8 + T cells, as compared to the wild-type CRT/E7 vaccine, which primarily generated murine H-2Db restricted E7 peptide (aa49-57) specific CD8 + T cell responses. We also observed transfection of the oncogenic DNA plasmids with electroporation generated spontaneous oral tumor in all of the injected mice. Additionally, treatment with CRT/E7(N53S) DNA vaccine intramuscularly followed by electroporation resulted in significant antitumor effects against the spontaneous HPV16 E6/E7-expressing oral tumors in HLA-A2 (AAD) transgenic mice.ConclusionsTaken together, the data indicated that the combination of HPV16 E6/E7-expressing DNA, NRasG12V DNA and DNA encoding sleeping beauty transposase is able to generate spontaneous oral tumor in HLA-A2 (AAD) transgenic mice, which can be successfully controlled by treatment with CRT/E7(N53S) DNA vaccine. The translational potential of our studies are discussed.

Project description:BackgroundHuman papillomavirus (HPV) E6 and E7 oncoproteins play a crucial role in HPV-related diseases, such as cervical cancer, and can be used as ideal targets for therapeutic vaccines. Human leukocyte antigen (HLA) participates in the immune response to block HPV infection and invasion by its target/recognition function. HPV-33 and HPV-58 are highly prevalent among Chinese women. Therefore, it is of great significance to study the E6 and E7 region-specific gene polymorphisms of HPV-33 and HPV-58 in Southwest China and to identify ideal epitopes for vaccine design. Both HPV-33 and HPV-58 belong to α-9 genus HPV and are highly homologous, so their correlations are included in our research.MethodsTo study the E6 and E7 variations and polymorphisms of HPV-33 and HPV-58 in Southwest China, we collected samples, extracted and sequenced DNA, and identified variants. Nucleotide sequences were translated into amino acids by Mega 6.0 software. The physical/chemical properties, amino acid-conserved sequences and secondary structure of protein sequences were analysed by the Protparam server, ConSurf server and PSIPRED software. The T and B cell epitopes of the E6/E7 reference and variant sequences in HPV-33 and HPV-58 were predicted by the Immune Epitope Database (IEDB) analysis server and the ABCpred server, respectively.ResultsFive and seven optimal HLA-I restricted T cell epitopes were selected from HPV-33 and HPV-58 E6, respectively, and these optimal epitopes are mainly located in 41-58EVYDFAFADLTVVYREGN of HPV-33 E6 and 40-60SEVYDFVFADLRIVYRDGNPF of HPV-58 E6. Six optimal HLA-I-restricted T cell epitopes were selected from HPV-33 and HPV-58 E7, and these epitopes are mainly located in 77-90RTIQQLLMGTVNIV of HPV-33 E7 and 78-91RTLQQLLMGTCTIV of HPV-58 E7.ConclusionsHPV-33/HPV-58 E6/E7 gene polymorphisms and T/B cell epitopes of their reference and variant sequences were studied, and candidate epitopes were selected by bioinformatics techniques for therapeutic vaccine design for people in Southwest China. This study was the first to investigate the correlation of epitopes between HPV-33 and HPV-58. After experimental validation, these selected epitopes will be employed to induce a wide range of immune responses in heterogeneous HLA populations.

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Unique potential of 4-1BB agonist antibody to promote durable regression of HPV+ tumors when combined with an E6/E7 peptide vaccine.

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