Local delivery of poxvirus vaccines for melanoma

Intratumoral delivery of recombinant vaccinia virus encoding for ErbB2/Neu inhibits the growth of salivary gland carcinoma cells

Background

The antitumor activity induced by intratumoral vaccination with poxvirus expressing a tumor antigen was shown to be superior to that induced by subcutaneous vaccination. Salivary gland carcinomas overexpress ErbB2. Trastuzumab, a monoclonal antibody to ErbB2, was proposed for salivary gland tumors treatment. We explored the effectiveness of intratumoral vaccination with the recombinant vaccinia virus ErbB2/Neu (rV-neuT) vaccine in hampering the growth of transplanted Neu-overexpressing BALB-neuT salivary gland cancer cells (SALTO) in BALB-neuT mice.

Methods

BALB-neuT male mice were subcutaneously injected with SALTO tumor cells and intratumorally vaccinated twice with different doses of either rV-neuT or V-wt (wild-type). Tumors were measured weekly. The presence of anti-ErbB2/Neu antibodies was assayed by ELISA, immunoprecipitation or indirect immunofluorescence. Biological activity of immune sera was investigated by analyzing antibody-dependent cellular cytotoxicity (ADCC), SALTO cells proliferation and apoptosis, ErbB2/Neu receptor down regulation and ERK1/2 phosphorylation. Anti-Neu T cell immunity was investigated by determining the release of IL-2 and IFN-gamma in T cells supernatant. Survival curves were determined using the Kaplan-Meier method and compared using the log-rank test. Differences in tumor volumes, number of apoptotic cells, titer of the serum, percentage of ADCC were evaluated through a two-tailed Student’s t-test.

Results

rV-neuT intratumoral vaccination was able to inhibit the growth of SALTO cancer cells in a dose-dependent manner. The anti-Neu serum titer paralleled in vivo antitumor activity of rV-neuT vaccinated mice. rV-neuT immune serum was able to mediate ADCC, inhibition of SALTO cells proliferation, down regulation of the ErbB2/Neu receptor, inhibition of ERK1/2 phosphorylation and induction of apoptosis, thus suggesting potential mechanisms of in vivo tumor growth interference. In addition, spleen T cells of rV-neuT vaccinated mice released IFN-gamma and IL-2 upon in vitro stimulation with several Neu-specific peptides located in the extracellular domain of Neu sequence.

Conclusions

rV-neuT intratumoral vaccination could be employed to induce an efficient antitumor response and reject transplanted salivary gland tumors. Our findings may have important implications for the design of cancer vaccine protocols for the treatment of salivary gland tumors and other accessible tumors using intratumoral injection of recombinant vaccinia virus.

Local delivery of recombinant vaccinia virus encoding for neu counteracts growth of mammary tumors more efficiently than systemic delivery in neu transgenic mice

Recombinant vaccinia virus has been widely employed as a cancer vaccine in several clinical trials. In this study we explored, employing BALB/c mice transgenic for the rat neu oncogene, the ability of the recombinant vaccinia virus neu (rV-neuT) vaccine to inhibit growth of neu+ mammary carcinomas and whether the efficacy of vaccination was dependent on: (a) carcinogenesis stage at which the vaccination was initiated; (b) number of vaccinations and (c) route of delivery (systemic vs. local). BALB-neuT mice were vaccinated one, two and three times by subcutaneous (s.c.) and intramammary gland (im.g.) injection with rV-neuT or V-wt (wild-type vaccinia virus) starting at the stage in which mouse mammary gland displays atypical hyperplasia, carcinoma in situ or invasive carcinoma. We demonstrated that vaccination using rV-neuT was more effective when started at an earlier stage of mammary carcinogenesis and after three vaccinations. The im.g. vaccination was more effective than the s.c. vaccination in inhibiting mammary carcinogenesis, eliciting anti-Neu antibodies, increasing anti-Neu IgG2a/G3 isotypes and inducing antibodies able to trigger mammary tumor cells apoptosis and antibody-dependent cellular cytotoxicity. The better protective ability of rV-neuT im.g. vaccination was associated with its capacity to induce a superior degree of in vivo mammary cancer cells apoptosis. Our research suggests that intratumoral vaccination using recombinant vaccinia virus could be employed to increase the activity of a genetic cancer vaccine. This study may have important implications for the design of cancer vaccine protocols for the treatment of breast cancer and of accessible tumors using recombinant vaccinia virus.

Phase I study of the intratumoral administration of recombinant canarypox viruses expressing B7.1 and interleukin 12 in patients with metastatic melanoma

The objective of this study was to evaluate the safety and activity of the intratumoral administration of the immune costimulatory molecule, B7.1, encoded by a vector derived from the canarypox virus, ALVAC (ALVAC-B7.1), alone and with the intratumoral injection of ALVAC encoding the immune-stimulatory cytokine, interleukin 12 (ALVAC-IL-12). Fourteen patients with metastatic melanoma who had s.c. nodules received intratumoral injections on days 1, 4, 8, and 11. Nine patients were given escalating doses of up to 25 x 10(8) plaque-forming units of ALVAC-B7.1. Five patients were given 25 x 10(8) plaque-forming units of ALVAC-B7.1 combined with ALVAC-IL-12 50% tissue culture infective dose of 2 x 10(6). Toxicity was mild to moderate and consisted of inflammatory reactions at the injection site and fever, chills, myalgia, and fatigue. Higher levels of B7.1 mRNA were observed in ALVAC-B7.1-injected tumors compared with saline-injected control tumors. Higher levels of intratumoral vascular endothelial growth factor and IL-10, cytokines with immune suppressive activities, were also observed in ALVAC-B7.1- and ALVAC-IL-12-injected tumors compared with saline-injected controls. Serum levels of vascular endothelial growth factor increased at day 18 and returned to baseline at day 43. All patients developed antibody to ALVAC. Intratumoral IL-12 and IFN-gamma mRNA decreased. Changes in serum IL-12 and IFN-gamma levels were not observed. Tumor regressions were not observed. The intratumoral injections of ALVAC-B7.1 and ALVAC-IL-12 were well tolerated at these dose levels and at this schedule and resulted in measurable biological response. This response included the production of factors that may suppress the antitumor immunologic activity of these vectors.

Vaccination with T cell-defined antigens

Tumour immunology encompasses a broad array of biological phenomena including interactions between neoplastic cells and the innate and adaptive immune response. Among immune cells, T cells have taken the centre stage because they can be easily demonstrated to specifically recognise autologous cancer cells. As most tumour-associated antigens are intracellular proteins, T cells appear to be the most suitable tool for cancer-specific attack, as antibodies do not cross the cell membrane and the innate immune response lacks the same level of specificity. Finally, the relative ease in which T cells can be educated through antigen-specific immunisation to recognise cancer cells has elevated them to an even higher stature. In this review, it will be argued that T cells represent a unique anticancer agent, characterised by absolute specificity. Although other therapeutic modalities (antibody-based) have been effectively implemented, a comparison of T cell-based approaches with other modalities goes beyond the purposes of this review and will not be included in the discussion. However, it is obvious that the role of the T cell is limited and other components of the immune response (effector mononuclear phagocytes, natural killer cells, cytokines, chemokines, soluble factors), genetic background and tumour heterogeneity are likely to be necessary for the completion of cancer rejection.

Understanding the response to immunotherapy in humans

Whether the efforts of the last decade aimed at the development of vaccines against tumor-specific antigens encountered success or failure is a matter of expectations. On the bright side, we could optimistically observe that anti-cancer-vaccines stand as an outstanding example of the successful implementation of modern biotechnology tools for the development of biologically sound therapeutics. In particular, vaccines against melanoma (the prototype model of tumor immunology in humans) can reproducibly induce cytotoxic T cell (CTL) responses exquisitely specific for cancer cells. This achievement trespasses the specificity of any other anti-cancer therapy. The skeptics, on the other end, might point out that immunization only rarely leads to cancer regression, labeling, therefore, this approach is ineffective. In our opinion this judgment stems from the naïve expectation that CTL induction is sufficient for an effective immune response. Here we propose that more needs to be understood about the mechanisms required for the induction of a therapeutically relevant immune response in humans. In particular, we will discuss the variables related to cancer heterogeneity, the weight of individual patients' polymorphism(s), the role of the T cell activation and differentiation and, finally, the complex relationship between immune and cancer cells within the tumor microenvironment.

Overview of melanoma vaccines and promising approaches

It is difficult to envision anything better than melanoma vaccines to exemplify the effectiveness of modern biotechnology in developing biologically rational therapeutics. Melanoma vaccines can reproducibly induce cytotoxic T lymphocyte (CTL) responses better than any other anticancer therapy. Anticancer vaccines have been labeled by some as ineffective for the simple reason that they only rarely lead to cancer regression. This oxymoron stems from the naïve expectation that CTLs are all that is needed to reject cancer. Little is known about requirements for CTL localization and effector function within the tumor microenvironment. In the future, more attention should be given to events downstream of immunization (afferent arm of immune response) to identify combination therapies likely to facilitate localization and activation of CTL at the receiving end (efferent arm).