Anti-tumor effect of the alphavirus-based virus-like particle vector expressing prostate-specific antigen in a HLA-DR transgenic mouse model of prostate cancer

Vaccine. 2015 Oct 5;33(41):5386-5395. doi: 10.1016/j.vaccine.2015.08.062. Epub 2015 Aug 28.


The goal of this study was to determine if an alphavirus-based vaccine encoding human Prostate-Specific Antigen (PSA) could generate an effective anti-tumor immune response in a stringent mouse model of prostate cancer. DR2bxPSA F1 male mice expressing human PSA and HLA-DRB1(*)1501 transgenes were vaccinated with virus-like particle vector encoding PSA (VLPV-PSA) followed by the challenge with Transgenic Adenocarcinoma of Mouse Prostate cells engineered to express PSA (TRAMP-PSA). PSA-specific cellular and humoral immune responses were measured before and after tumor challenge. PSA and CD8 reactivity in the tumors was detected by immunohistochemistry. Tumor growth was compared in vaccinated and control groups. We found that VLPV-PSA could infect mouse dendritic cells in vitro and induce a robust PSA-specific immune response in vivo. A substantial proportion of splenic CD8 T cells (19.6 ± 7.4%) produced IFNγ in response to the immunodominant peptide PSA(65-73). In the blood of vaccinated mice, 18.4 ± 4.1% of CD8 T cells were PSA-specific as determined by the staining with H-2D(b)/PSA(65-73) dextramers. VLPV-PSA vaccination also strongly stimulated production of IgG2a/b anti-PSA antibodies. Tumors in vaccinated mice showed low levels of PSA expression and significant CD8+ T cell infiltration. Tumor growth in VLPV-PSA vaccinated mice was significantly delayed at early time points (p=0.002, Gehan-Breslow test). Our data suggest that TC-83-based VLPV-PSA vaccine can efficiently overcome immune tolerance to PSA, mediate rapid clearance of PSA-expressing tumor cells and delay tumor growth. The VLPV-PSA vaccine will undergo further testing for the immunotherapy of prostate cancer.

Keywords: DR2b mice; PSA; Prostate cancer; TC-83 virus; VLPV; Vaccine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alphavirus / genetics
  • Alphavirus / immunology
  • Animals
  • Cancer Vaccines / genetics
  • Cancer Vaccines / immunology*
  • Cell Line
  • Dendritic Cells / immunology
  • Dendritic Cells / metabolism
  • Disease Models, Animal
  • Gene Expression*
  • Gene Order
  • Genetic Vectors / genetics
  • HLA-DR Antigens / genetics*
  • HLA-DR Antigens / immunology
  • Humans
  • Immunity
  • Immunization
  • Lymphocytes, Tumor-Infiltrating / immunology
  • Lymphocytes, Tumor-Infiltrating / metabolism
  • Male
  • Mice
  • Mice, Transgenic
  • Prostate-Specific Antigen / genetics*
  • Prostate-Specific Antigen / immunology*
  • Prostatic Neoplasms / genetics*
  • Prostatic Neoplasms / immunology*
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / therapy
  • Tumor Burden / immunology
  • Vaccines, Virus-Like Particle / genetics
  • Vaccines, Virus-Like Particle / immunology*


  • Cancer Vaccines
  • HLA-DR Antigens
  • Vaccines, Virus-Like Particle
  • Prostate-Specific Antigen