Establishment of tumor-specific immunotherapy model utilizing vaccinia virus-reactive helper T cell activity

Potential of oncolytic viruses in the treatment of multiple myeloma

Multiple myeloma (MM) is a clonal malignancy of plasma cells that is newly diagnosed in ~30,000 patients in the US each year. While recently developed therapies have improved the prognosis for MM patients, relapse rates remain unacceptably high. To overcome this challenge, researchers have begun to investigate the therapeutic potential of oncolytic viruses as a novel treatment option for MM. Preclinical work with these viruses has demonstrated that their infection can be highly specific for MM cells and results in impressive therapeutic efficacy in a variety of preclinical models. This has led to the recent initiation of several human trials. This review summarizes the current state of oncolytic therapy as a therapeutic option for MM and highlights a variety of areas that need to be addressed as the field moves forward.

Replicating vectors for gene therapy of cancer: risks, limitations and prospects

There are good theoretical arguments for exploring the use of replicating gene-transfer vectors for human cancer therapy. Such vectors should be derived from weakly pathogenic human viruses with initially broad tissue tropism. Coat protein engineering and promoter engineering might be used successfully to narrow the tropism of the vector, enhancing its ability to target tumour cells. Killing of uninfected 'bystander' tumour cells could be achieved through prodrug activation by a vector-encoded enzyme. Rapid elimination of infused vector particles by circulating antiviral antibody would limit access to tumour deposits after repeated administration, but might be circumvented by the use of infectious nucleic acid which is poorly imunogenic [64]. This putative therapeutic strategy is illustrated in Figure 1.

Immunotherapy of the rat 13762SC mammary adenocarcinoma by vaccinia virus augmentation of tumor immunity

We studied whether vaccinia virus (VV) functioned as an immunogenic carrier in augmenting anti-tumor immunity in rats bearing a syngeneic metastatic tumor. The primary tumor was induced by injecting 10(6) 13762SC mammary adenocarcinoma cells subcutaneously into the right hind footpad of Fischer 344 rats. A concomitant anti-tumor response is induced by the tumor as demonstrated by the inhibited growth of a second tumor challenge given in the contralateral footpad 3-15 days later. Attempts were made to increase the concomitant immunity by injecting tumor-bearing animals intramuscularly with irradiated, VV-infected or uninfected 13762SC cells without adjuvant. Provided the immunotherapy was done within 5 days of the tumor challenge, administration of 10(6)-10(7) irradiated, VV-infected 13762SC cells resulted in significantly slower tumor growth, or led to complete tumor regression, compared to control animals given no treatment. In contrast, tumor growth in animals given only VV or given irradiated, uninfected 13762SC cells, alone or mixed with VV, was the same as that in control animals. Kinetics of early primary tumor growth were predictive of a longer-term anti-tumor effect. Rechallenge of 13762SC tumor-cured animals with either the homologous or with a heterologous syngeneic mammary adenocarcinoma showed the animals to be specifically 13762SC tumor-resistant, since only rats challenged with the heterologous mammary adenocarcinoma developed progressive tumors. We interpret these results to mean that early immunotherapy with irradiated, VV-infected 13762SC cells enhances an on-going anti-tumor immune response sufficiently to cause rejection of the primary tumor and any metastases that have occurred. We also believe that later immunotherapy with irradiated, VV-infected cells has no effect due to tumor-induced immunosuppression becoming paramount.