Genetic Regulation of the Response to Her-2 DNA Vaccination in Human Her-2 Transgenic Mice

Genetic regulation of immune reactivity to Her-2 vaccination and the consequent antitumor effect was tested in human Her-2 transgertic (Tg) mice of C57BL/6 (B6), BALB/c (BALB), and (B6x BALB) F1 (F1) background. Mice were electro-vaccinated with Her-2 DNA with or without pretreatment with CD25 monoclonal antibody to remove CD25(hi) regulatory T cells. When CD25(+) T cells were intact, BALB Her-2 Tg mice were more responsive than the other two strains in both humoral and cellular immunities, and their tumor growth was significantly delayed. B6 Her-2 Tg mice responded poorly and F1 mice showed modest immune reactivity, but tumor growth did not change in either strain. Depletion of CD25 hi T cells before vaccination significantly improved protection from tumor challenge in F1 Her-2 Tg mice. This was associated with elevated levels of Her-2 IgG1, IgG2a, and lgG2c antibodies, an some mice also showed IFN-(alpha) producing T-cell response. The same treatment induced modest improvement in B6 Her-2 Tg mice. In BALB Her-2 Tg mice, however, depletion of CD25 hi T cells did not further improve antitumor efficacy. Although their Her-2-specific IgG1 and interleukin-5-secreting T cells increased, the levels of IgG2a and IFN-alpha-secreting T cells did not change. These results are the first to show genetic regulation of the response to a cancer vaccine and an unequal effect of removing CD25(hi) T cells on antitumor immunity. These results warrant individualized treatment plans or patients with heterogeneous genetic backgrounds and possibly differential intrinsic immune reactivity to tumor antigens. [Cancer Res 2009;69(1):212-8]