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Creation of a Merkel cell polyomavirus small T antigen-expressing murine tumor model and a DNA vaccine targeting small T antigen.

Gomez B, He L, Tsai YC, Wu TC, Viscidi RP, Hung CF - Cell Biosci (2013)

Bottom Line: MCPyV LT antigen expression was found to be a requirement for MCC tumor maintenance and ST protein also likely contributes to the carcinogenesis of MCC.The LT-targeting DNA vaccine generated prolonged survival, decreased tumor size and increased LT-specific CD8+ T cells in tumor-bearing mice.In ST-expressing tumor-bearing mice, this vaccine, pcDNA3-MCC/ST, generated a significant number of ST antigenic peptide-specific CD8+ T cells and experienced markedly enhanced survival compared to mice vaccinated with empty vector.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departments of Pathology, Johns Hopkins Medical Institutions, Baltimore, MD, USA. chung2@jhmi.edu.

ABSTRACT

Background: Merkel cell polyomavirus (MCPyV) is a DNA virus expressing transcripts similar to the large T (LT) and small T (ST) transcripts of SV40, which has been implicated in the pathogenesis of Merkel cell carcinoma (MCC), a rare and highly aggressive neuroendocrine skin cancer. MCPyV LT antigen expression was found to be a requirement for MCC tumor maintenance and ST protein also likely contributes to the carcinogenesis of MCC. Previously, we have identified the probable immunodominant epitope of MCPyV LT and developed a DNA vaccine encoding this epitope linked to calreticulin. The LT-targeting DNA vaccine generated prolonged survival, decreased tumor size and increased LT-specific CD8+ T cells in tumor-bearing mice.

Results: In this study, we developed a MCPyV ST-expressing tumor cell line from B16 mouse melanoma cells. We then utilized this ST-expressing tumor cell line to test the efficacy of a DNA vaccine encoding ST. In ST-expressing tumor-bearing mice, this vaccine, pcDNA3-MCC/ST, generated a significant number of ST antigenic peptide-specific CD8+ T cells and experienced markedly enhanced survival compared to mice vaccinated with empty vector.

Conclusions: The formation of an effective vaccine against MCPyV has the potential to advance the field of MCC therapy and may contribute to the control of this severe malignancy through immunotherapy. Both of the innovative technologies presented here provide opportunities to develop and test MCPyV-targeted therapies for the control of Merkel cell carcinoma.

No MeSH data available.


Related in: MedlinePlus

Characterization of the role of CD8+ T cells in tumor protection elicited by the pcDNA3-MCC/ST vaccine. Vaccinated mice were boosted two times at the same dose and regimen at one week intervals. Beginning 1 day after last vaccination, vaccinated mice were intraperitoneally injected with anti-CD8 monoclonal antibody other day. Antibody-depleted mice were then challenged with B16/ST tumor (1×105 cells/mouse) subcutaneously in the right flank on day 22 after vaccination. Mice were monitored for evidence of tumor growth by inspection, palpation and tumor size was measured once a week. (A) Survival analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine. (B) Tumor size analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine.
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Figure 5: Characterization of the role of CD8+ T cells in tumor protection elicited by the pcDNA3-MCC/ST vaccine. Vaccinated mice were boosted two times at the same dose and regimen at one week intervals. Beginning 1 day after last vaccination, vaccinated mice were intraperitoneally injected with anti-CD8 monoclonal antibody other day. Antibody-depleted mice were then challenged with B16/ST tumor (1×105 cells/mouse) subcutaneously in the right flank on day 22 after vaccination. Mice were monitored for evidence of tumor growth by inspection, palpation and tumor size was measured once a week. (A) Survival analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine. (B) Tumor size analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine.

Mentions: In order to examine the impact of CD8+ T cells on the therapeutic antitumor effect elicited by pcDNA3-MCC/ST DNA vaccine against B16/ST tumors, we performed an in vivo antibody depletion assay. C57BL/6 mice were vaccinated with pcDNA3-MCC/ST three times at one week intervals. Beginning on day 15 after the first vaccination, mice were treated with anti-CD8 antibody every other day and then were challenged subcutaneously with B16/ST tumor cells. As shown in Figure 5A, virtually all of the mice depleted of CD8+ T cells developed tumors, compared to only 60% of non-depleted mice. Furthermore, mice treated with anti-CD8 antibody developed significantly larger tumors compared to mice untreated mice. These data suggest that CD8+ T cells are essential for the observed therapeutic antitumor effect against ST-expressing tumors generated by the pcDNA3-MCC/ST DNA vaccine.


Creation of a Merkel cell polyomavirus small T antigen-expressing murine tumor model and a DNA vaccine targeting small T antigen.

Gomez B, He L, Tsai YC, Wu TC, Viscidi RP, Hung CF - Cell Biosci (2013)

Characterization of the role of CD8+ T cells in tumor protection elicited by the pcDNA3-MCC/ST vaccine. Vaccinated mice were boosted two times at the same dose and regimen at one week intervals. Beginning 1 day after last vaccination, vaccinated mice were intraperitoneally injected with anti-CD8 monoclonal antibody other day. Antibody-depleted mice were then challenged with B16/ST tumor (1×105 cells/mouse) subcutaneously in the right flank on day 22 after vaccination. Mice were monitored for evidence of tumor growth by inspection, palpation and tumor size was measured once a week. (A) Survival analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine. (B) Tumor size analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3750327&req=5

Figure 5: Characterization of the role of CD8+ T cells in tumor protection elicited by the pcDNA3-MCC/ST vaccine. Vaccinated mice were boosted two times at the same dose and regimen at one week intervals. Beginning 1 day after last vaccination, vaccinated mice were intraperitoneally injected with anti-CD8 monoclonal antibody other day. Antibody-depleted mice were then challenged with B16/ST tumor (1×105 cells/mouse) subcutaneously in the right flank on day 22 after vaccination. Mice were monitored for evidence of tumor growth by inspection, palpation and tumor size was measured once a week. (A) Survival analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine. (B) Tumor size analysis of B16/ST tumor-bearing mice treated with pcDNA3-MCC/ST DNA vaccine.
Mentions: In order to examine the impact of CD8+ T cells on the therapeutic antitumor effect elicited by pcDNA3-MCC/ST DNA vaccine against B16/ST tumors, we performed an in vivo antibody depletion assay. C57BL/6 mice were vaccinated with pcDNA3-MCC/ST three times at one week intervals. Beginning on day 15 after the first vaccination, mice were treated with anti-CD8 antibody every other day and then were challenged subcutaneously with B16/ST tumor cells. As shown in Figure 5A, virtually all of the mice depleted of CD8+ T cells developed tumors, compared to only 60% of non-depleted mice. Furthermore, mice treated with anti-CD8 antibody developed significantly larger tumors compared to mice untreated mice. These data suggest that CD8+ T cells are essential for the observed therapeutic antitumor effect against ST-expressing tumors generated by the pcDNA3-MCC/ST DNA vaccine.

Bottom Line: MCPyV LT antigen expression was found to be a requirement for MCC tumor maintenance and ST protein also likely contributes to the carcinogenesis of MCC.The LT-targeting DNA vaccine generated prolonged survival, decreased tumor size and increased LT-specific CD8+ T cells in tumor-bearing mice.In ST-expressing tumor-bearing mice, this vaccine, pcDNA3-MCC/ST, generated a significant number of ST antigenic peptide-specific CD8+ T cells and experienced markedly enhanced survival compared to mice vaccinated with empty vector.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departments of Pathology, Johns Hopkins Medical Institutions, Baltimore, MD, USA. chung2@jhmi.edu.

ABSTRACT

Background: Merkel cell polyomavirus (MCPyV) is a DNA virus expressing transcripts similar to the large T (LT) and small T (ST) transcripts of SV40, which has been implicated in the pathogenesis of Merkel cell carcinoma (MCC), a rare and highly aggressive neuroendocrine skin cancer. MCPyV LT antigen expression was found to be a requirement for MCC tumor maintenance and ST protein also likely contributes to the carcinogenesis of MCC. Previously, we have identified the probable immunodominant epitope of MCPyV LT and developed a DNA vaccine encoding this epitope linked to calreticulin. The LT-targeting DNA vaccine generated prolonged survival, decreased tumor size and increased LT-specific CD8+ T cells in tumor-bearing mice.

Results: In this study, we developed a MCPyV ST-expressing tumor cell line from B16 mouse melanoma cells. We then utilized this ST-expressing tumor cell line to test the efficacy of a DNA vaccine encoding ST. In ST-expressing tumor-bearing mice, this vaccine, pcDNA3-MCC/ST, generated a significant number of ST antigenic peptide-specific CD8+ T cells and experienced markedly enhanced survival compared to mice vaccinated with empty vector.

Conclusions: The formation of an effective vaccine against MCPyV has the potential to advance the field of MCC therapy and may contribute to the control of this severe malignancy through immunotherapy. Both of the innovative technologies presented here provide opportunities to develop and test MCPyV-targeted therapies for the control of Merkel cell carcinoma.

No MeSH data available.


Related in: MedlinePlus