Active specific immunotherapy of residual micrometastasis

Abstract

A vaccine of Bacillus Calmette-Gu~rin (BCG) admixed with tumor cells induced systemic immunity and had a therapeutic effect on subclinical, disseminated mierometastasis. Inbred strain-2 guinea-pigs given I V injections of 5 x 103 to 106 syngeneic LIO hepatocarcinoma cells were vaccinated after metastatic foei were established in the lung parenchyma. The purpose of this study was to establish the variables that can be manipulated to assure optimal immunotherapy while minimizing deleterious side effects of the BCG. In the present study we examined the variables of source, dose, and ratio of BCG to tumor cells. Four BCG sources (lyophilized Tiee and Connaught; fresh-frozen Phipps and Tice) were compared. No significant differences among these BCG preparations couM be detected with respect to adjuvant potential when they were admixed with attenuated tumor cells in a vaccine. The dose study clearly demonstrated that a BCG dose dependency exists with relation to induction of effective cell-mediated immunity or survival from disseminated mierometastatic disease. Furthermore, evaluations of dose versus ratio of BCG to tumor cells also supported a BCG dose dependency, with the lowest effective BCG dose being directly influenced by tumor burden of the host. Cutaneous reactivity and hypersensitivity of the primary and secondary immunization sites of tumor-bearing animals treated with effective and ineffective vaccines supported the direct association of reaction to BCG and specific tumor immunity. However, when an in vitro leukocyte migration inhibition assay was used, the degree of reactivity to BCG could not be exploited as a quantitative, diagnostic monitor of effective systemic tumor immunity.

Postoperative Active-Specific Immunotherapy of Lymph Node Micrometastasis in a Guinea Pig Tumor Model

“…Tumor cells undergo inactiva tion prior to ASI in order to prevent their outgrowth in the autologous host. Blockade of metabolic cell activity is preferred to cell destructing measures because tumor cells with maintained structural integrity and lim ited generation capacity appear to be more immunogenic [ 16,23,27,28]. In our experi ments tumor cells received either incubation with mitomycin C or irradiation -both methods resulted in almost 100% cell viabil ity determined by trypan blue exclusion, i.e.…”

“…Outgoing from the basic experiments of Zbar et al [33,38,39] on local BCG immu notherapy Hanna et al [15,16,27,28] de veloped the concept of ASI with BCG-admixed autologous tumor cells in the L 10-strain 2 guinea pig model. They performed extensive investigations on ASI of visceral micrometastasis concerning several aspects of vaccine preparation and treatment sched ule.…”

“…(2) Active immunotherapy is based on the application of immunostimulating agents (BRM, lymphokines, BCG, etc.) or tumor cell preparations (autologous/allogenic) in order to elicit a nonspecific or specific im mune enhancement in the tumor-bearing host [7,16,17,22,36]. The approach of active-specific immunotherapy (ASI) is very similar to the concept of vaccination.…”

“…Cru cial parameters are (1) number of tumor cells; (2) amount of immunogenizing agent, and (3) viability or integrity of tumor cells [23. 27, 28], According to our own doseresponse experiments and earlier reports [16,17] we used 1 X 107 autologous tumor cells modified with 160 HU NDV or ad mixed with 1-3 X 107 BCG organisms per vaccination. Tumor cells undergo inactiva tion prior to ASI in order to prevent their outgrowth in the autologous host.…”

“…After the establish ment of microscopic disease in the first draining lymph node the intradermally growing primary tumor was resected and subsequent ASI was performed with either Newcastle disease virus (NDV) modified or BCG-admixed autologous tumor cells ac cording to respective protocols [15][16][17]32], Both ASI procedures were compared with each other and the therapeutic effect of a combined treatment (ASI with NDV and BCG) was investigated. Furthermore, we tested the influence of different measures of tumor cell inactivation (irradiation, mito mycin C treatment) in the course of vaccine preparation on ASI.…”