Adenovirus delivery provides extended interferon-alpha exposure and augments treatment of metastatic carcinoma.

Type I interferons (e.g. IFNalpha2b) have been successfully used to treat a variety of hematological malignancies, but have not been efficacious for treatment of most solid tumors. We tested the hypothesis that delivery of type I interferon utilizing recombinant adenovirus (rAd) vectors may improve treatment efficacy of metastatic carcinomas by providing increased interferon exposure resulting from continuous transgene expression. Treatment of mice with a rAd-vector expressing hybrid-IFN (rAd-IFNalpha2alpha1) inhibited 4T1 mammary carcinoma tumor growth and induced tumor regression in a dose-dependent manner. Moreover, rAd-IFNalpha2alpha1 treatment reduced hepatic and pulmonary metastatic burden. A comparison of local and systemic routes of administration demonstrated that intratumoral delivery of rAd-IFNalpha2alpha1 was sufficient for inhibition of tumor growth. Moreover, it reduced toxicity associated with high-dose systemic IFNalpha2alpha1 exposure. Interestingly, antitumor activity following intratumoral treatment was due, in part, to the immunostimulatory capacity of the rAd vector component. Furthermore, systemic administration of rAd-IFNalpha2alpha1 potentiated the immunotherapeutic effect induced by local intralesional delivery of empty-rAd vector. These results suggest continuous interferon-alpha exposure may provide improved antitumor responses for metastatic carcinomas. Additionally, immunostimulatory responses induced by rAd-IFNalpha2alpha1 may mitigate the immune-evasive tumor microenvironment.

The role of adoptively transferred CD8 T cells and host cells in the control of the growth of the EG7 thymoma: factors that determine the relative effectiveness and homing properties of Tc1 and Tc2 effectors.

We had previously examined the factors that regulate the response of OVA-specific TCR-transgenic CD8 T cells to the B16 OVA melanoma, growing as lung metastases. We examine here whether the same parameters operate for EG7, growing intradermally. Tc1 or Tc2 CD8 effector cells from OT-1 mice were injected either mixed with the tumor or i.v. at day 0 or 7. Tc2 were one-fifth to one-tenth as effective as Tc1 when injected with the tumor, in controlling tumor growth, but were only 1/20 to 1/100 injected i.v. Tc1 injected i.v. entered the draining lymph nodes faster than Tc2 and caused a faster accumulation of host cells. Both caused an abrupt termination of host cell entry into lymph nodes and spleen after tumor elimination, but this occurred earlier for Tc1 than for Tc2. Host responses were ineffective in the absence of adoptive transfer but were essential after transfer. Perforin expression in the donor cells plays no role in adoptively transferred Tc1 or Tc2 control of the tumor, and neither IL-4 nor IL5 is needed for Tc1 or Tc2 function. Tc1 cells from mice lacking IFN-gamma, however, control tumor growth less well, whereas Tc2 effectors lacking IFN-gamma are unaffected. Tc1 from IFN-gamma-deficient mice attract fewer host cells to the draining lymph node, whereas Tc1 cells from perforin-deficient donors are unimpaired. We conclude that host cell recruitment is a crucial element in adoptive immunotherapy. The differences between the EG7 and the previous B16 melanoma model are discussed.

The effects of prolonged administration of 5-bromodeoxyuridine on cells of the immune system.

We have determined the in vivo effect of 5-bromodeoxyuridine (BrdU) administered to mice in the drinking water for various lengths of time on the performance of T and B lymphocytes in a number of experimental protocols. Young mice continuously exposed to BrdU fail to gain weight, and the lymphocytes recovered after a prolonged period of exposure are fewer in number than in control mice. The recovery of normal levels of T and B lymphocytes after irradiation is severely impaired. Ag-specific cells responding to Ag in an adoptive transfer model fail to expand as much in the presence of BrdU as in the absence, and the Ag-specific effectors produced in the presence of BrdU are less able to secrete cytokines upon restimulation in vitro. Polarized populations of Tc1 and Tc2 effectors generated in vitro proliferate less in the presence of BrdU, and the resulting effectors make less cytokines per cell upon restimulation. Thus, the incorporation of BrdU into T or B lymphocytes can, under some circumstances, seriously impair the performance of the labeled cells, and these findings raise a note of caution in the interpretation of studies that make use of long-term exposure to BrdU.