Replication-restricted vaccinia as a cytokine gene therapy vector in cancer: persistent transgene expression despite antibody generation

Our plain-English summary of Replication-restricted vaccinia as a cytokine gene therapy vector in cancer: persistent transgene expression despite antibody generation, by S. Mukherjee, T. Haenel, R. Himbeck, et al (Cancer Gene Therapy, 2000).

The study

• Authors: S. Mukherjee, T. Haenel, R. Himbeck, B. Scott, I. Ramshaw, R.A. Lake, G. Harnett, P. Phillips, S. Morey, D. Smith, J.A. Davidson, A.W. Musk, B. Robinson
• Journal: Cancer Gene Therapy
• Published: 2000;7(5):663-70
• Cited by: 85 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: As antitumoral immunity requires the generation of local immunity directed against tissue proteins, we attempted to recreate within tumors the same environment found within tissues affected by autoimmune diseases (i.e., prolonged cytokine expression). Vaccinia virus (VV) has not been widely used as a cytokine gene therapy vector because of presumed high immunogenicity that would likely make repeated injections impossible; therefore, we modified it by inserting the cytokine gene into the thymidine kinase region, rendering it replication-restricted. The cytokine chosen was human interleukin-2 (IL-2); a molecule with powerful antitumoral effects.

Methods: Six patients with the treatment-resistant tumor malignant mesothelioma received intratumoral (i.t.) VV-IL-2 therapy for 12 weeks by injection of 10(7) plaque-forming units of VV-IL-2 per dose. Serial tumor biopsies, sputum, urine, and blood samples were tested for VV-IL-2 mRNA expression; VV culture and T-cell infiltrates were evaluated by immunohistochemistry. Patients and contacts of patients were monitored for changes in VV immunoglobulin G (IgG) levels and clinical evidence of VV infection.

Results: VV-IL-2 was not excreted and was only cultured in one patient from tumor biopsies. A T-cell infiltrate was detected in 50% of tumor biopsies. VV-IL-2 mRNA expression was highest on days 1-3 postinjection and was detected for up to 3 weeks after each injection even though VV IgG levels rose in all patients. No significant toxicities, infection of patient contacts, or tumor regressions were observed.

Conclusions: I.t. VV-IL-2 administration is safe, is associated with minimal toxicity, and results in i.t. expression of VV-IL-2 for up to 3 weeks postinjection regardless of the level of anti-VV IgG titers generated. This suggests that VV may be a good vector for repeated cytokine gene therapy of solid human cancer.

In plain English

This was a pilot clinical trial of a replication-restricted vaccinia virus carrying the human interleukin-2 gene (VV-IL-2) injected directly into tumor. Six patients with malignant mesothelioma that had grown through the chest wall as a subcutaneous nodule received intratumoral VV-IL-2 over 12 weeks, to a maximum dose of 10 to the 7th plaque-forming units; patient 1 began at 10 to the 5th and was escalated, and patients had between 2 and 12 treatments (mean 5). Serial tumor biopsies, sputum, urine and blood were tested, and 31 contacts were followed. The authors reported no toxicity and no change in blood counts or biochemistry, though the first patient had transient fevers after the highest doses. Virus was not cultured from body fluids; biopsies from patient 4 grew vaccinia. Anti-vaccinia IgG titers rose in all patients (1/10 to 1/1280), apart from patient 1, who had high titers before treatment from revaccination; VV-IL-2 mRNA was still detectable in biopsies for up to 3 weeks, with 67% positive on days 1 to 3 in patients 1 to 4. Of 36 biopsies stained, 18 showed CD3 T-cell staining. No tumor regression was seen. The authors concluded the approach was safe and that vaccinia may be a useful repeat cytokine gene therapy vector.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Pilot (phase I-type) clinical trial of intratumoral gene therapy in six patients, with accompanying in vitro cell-line testing
• Who was studied: Six patients with histologically or cytologically confirmed malignant mesothelioma with a subcutaneous chest-wall nodule, aged 55-71, five male and one female, all ECOG performance status 1, mean 16 months since diagnosis (range 8-27), treated in Western Australia; 31 contacts also evaluated
• Exposure: Intratumoral injection of replication-restricted recombinant vaccinia virus carrying the human IL-2 gene inserted into the thymidine kinase region, to a maximum dose of 10 to the 7th plaque-forming units per patient per week; patient 1 started at 10 to the 5th PFU with escalation over the next two cycles; injections weekly or three-weekly over 12 weeks
• Main results:
  • No toxicity was observed in the six treated patients and no change in blood or biochemical parameters
  • In the discussion the authors noted that the first patient, who had been revaccinated, had transient fevers within 12 hours of the highest-dose injections
  • VV-IL-2 was not cultured from sputum, urine, mouth wash, pleural fluid or blood in any patient; tumor biopsies from patient 4 were positive on culture on all three samples taken during the second cycle
  • None of 31 contacts of the six patients developed signs or symptoms of vaccinia infection, and unvaccinated contacts showed no rise in vaccinia antibody titer
  • Anti-vaccinia IgG titers rose progressively in all patients, from a minimum of 1/10 to a maximum of 1/1280, with patient 1 the exception because revaccination had already produced high pre-treatment titers
  • In patients 1 to 4, VV-IL-2 mRNA was positive in 67% of tumor biopsies on days 1-3, 54% on days 5-8 and 40% on day 21, a difference the authors reported as not statistically significant (P = .46); in patients 5 and 6, 63% of biopsies were positive on day 1
  • VV-IL-2 mRNA was detectable in tumor biopsies regardless of anti-VV IgG titer, with no statistically significant difference between low and high antibody titer groups (P = .41)
  • Of 36 tumor biopsies available for immunohistochemistry, 18 showed CD3 (T-cell marker) staining compared with pre-treatment controls; CD4 and CD8 staining could not be adequately obtained
  • No significant tumor regression was observed in the treated patients, radiologically or clinically
  • In vitro, two human mesothelioma cell lines (JU77 and NO36) infected with VV-IL-2 at a multiplicity of infection of 0.5 produced 1192 to 3767 ng/mL of IL-2 at 24 hours
• The authors' conclusion: The authors concluded that intratumoral VV-IL-2 was safe with minimal toxicity and produced intratumoral VV-IL-2 expression for up to 3 weeks after injection regardless of anti-vaccinia IgG titers, suggesting vaccinia may be a good vector for repeated cytokine gene therapy of solid human cancer
• Limitations the authors state:
  • The authors could not be certain biopsies came from the exact injection site, could not estimate the spread of infection, and noted more cells may have been transduced but not sampled
  • The authors stated there was no accurate way to determine whether the T-cell infiltrate reflected a specific antitumoral response, nonspecific IL-2 effects, or the virus itself
  • Evaluation of antitumoral effect was not the main aim, and the authors described the study as limited, with the optimum therapeutic regimen not yet achieved
  • Satisfactory CD4 and CD8 staining could not be obtained because of limited section material

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Cytokine, Malignant Mesothelioma, Sputum, Immunohistochemistry.

Related studies

• Cytokine gene therapy or infusion as treatment for solid human cancer — B.W. Robinson, S.A. Mukherjee, et al. (1998)
• Cytokine-armed vaccinia virus infects the mesothelioma tumor microenvironment to overcome immune tolerance and mediate tumor resolution — C. Jackaman, D.J. Nelson (2010)
• Gene therapy for lung diseases: development in the vector biology and novel concepts for gene therapy applications — M. Suzuki, T. Matsuse, et al. (2001)
• Use of protamine to augment adenovirus-mediated cancer gene therapy — M. Lanuti, C.E. Kouri, et al. (1999)
• A potential therapeutic strategy for malignant mesothelioma with gene medicine — Y. Tada, H. Shimada, et al. (2013)
• Combinatorial anti-angiogenic gene therapy in a human malignant mesothelioma model — S. Kubo, M. Takagi-Kimura, et al. (2015)

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