A prostate cancer DNA vaccine comprising: (a) a polynucleotide that encodes an antigen, wherein the antigen is prostatic acid phosphatase; and (b) an agent that suppresses immune regulatory cell function, wherein the immune regulatory cell function is that of IL-35 and the agent is an IL-35 antagonist, for use in a method of administering a vaccine to an individual in need thereof, the method comprising the step of: administering to the individual the vaccine, wherein the individual is selected to receive the vaccine by a method comprising the steps of: (i) administering to an immunocompromised animal peripheral blood mononuclear cells from the individual, where the immunocompromised animal is capable of mounting a delayed-type hypersensitivity response; (ii) administering to the immunocompromised animal the target antigen; and (iii) determining an antigen-specific immune regulatory response by measuring a delayed-type hypersensitivity in the immunocompromised animal to the target antigen in an assay configured to distinguish between absence of an effector response to the target antigen and presence of an antigen-specific immune regulatory response, and wherein the individual is selected to receive the vaccine if the cells mediate a delayed-type hypersensitivity response otherwise suppressed by the antigen-specific immune regulatory response. (a) a polynucleotide that encodes an antigen, wherein the antigen is prostatic acid phosphatase; and (b) an agent that suppresses immune regulatory cell function, wherein the immune regulatory cell function is that of IL-35 and the agent is an IL-35 antagonist, for use in a method of administering a vaccine to an individual in need thereof, the method comprising the step of: administering to the individual the vaccine, wherein the individual is selected to receive the vaccine by a method comprising the steps of: (i) administering to an immunocompromised animal peripheral blood mononuclear cells from the individual, where the immunocompromised animal is capable of mounting a delayed-type hypersensitivity response; (ii) administering to the immunocompromised animal the target antigen; and (iii) determining an antigen-specific immune regulatory response by measuring a delayed-type hypersensitivity in the immunocompromised animal to the target antigen in an assay configured to distinguish between absence of an effector response to the target antigen and presence of an antigen-specific immune regulatory response, and wherein the individual is selected to receive the vaccine if the cells mediate a delayed-type hypersensitivity response otherwise suppressed by the antigen-specific immune regulatory response. administering to the individual the vaccine, wherein the individual is selected to receive the vaccine by a method comprising the steps of: (i) administering to an immunocompromised animal peripheral blood mononuclear cells from the individual, where the immunocompromised animal is capable of mounting a delayed-type hypersensitivity response; (ii) administering to the immunocompromised animal the target antigen; and (iii) determining an antigen-specific immune regulatory response by measuring a delayed-type hypersensitivity in the immunocompromised animal to the target antigen in an assay configured to distinguish between absence of an effector response to the target antigen and presence of an antigen-specific immune regulatory response, and wherein the individual is selected to receive the vaccine if the cells mediate a delayed-type hypersensitivity response otherwise suppressed by the antigen-specific immune regulatory response. (i) administering to an immunocompromised animal peripheral blood mononuclear cells from the individual, where the immunocompromised animal is capable of mounting a delayed-type hypersensitivity response; (ii) administering to the immunocompromised animal the target antigen; and (iii) determining an antigen-specific immune regulatory response by measuring a delayed-type hypersensitivity in the immunocompromised animal to the target antigen in an assay configured to distinguish between absence of an effector response to the target antigen and presence of an antigen-specific immune regulatory response, and wherein the individual is selected to receive the vaccine if the cells mediate a delayed-type hypersensitivity response otherwise suppressed by the antigen-specific immune regulatory response.