Targeting the local tumor microenvironment with vaccinia virus expressing B7.1 for the treatment of melanoma

Abstract

Immunotherapy for the treatment of metastatic melanoma remains a major clinical challenge. The melanoma microenvironment may lead to local T cell tolerance in part through downregulation of costimulatory molecules, such as B7.1 (CD80). We report the results from the first clinical trial, to our knowledge, using a recombinant vaccinia virus expressing B7.1 (rV-B7.1) for monthly intralesional vaccination of accessible melanoma lesions. A standard 2-dose-escalation phase I clinical trial was conducted with 12 patients. The approach was well tolerated with only low-grade fever, myalgias, and fatigue reported and 2 patients experiencing vitiligo. An objective partial response was observed in 1 patient and disease stabilization in 2 patients, 1 of whom is alive without disease 59 months following vaccination. All patients demonstrated an increase in postvaccination antibody and T cell responses against vaccinia virus. Systemic immunity was tested in HLA-A*0201 patients who demonstrated an increased frequency of gp100 and T cells specific to melanoma antigen recognized by T cells 1 (MART-1), also known as Melan-A, by ELISPOT assay following local rV-B7.1 vaccination. Local immunity was evaluated by quantitative real-time RT-PCR, which suggested that tumor regression was associated with increased expression of CD8 and IFN-gamma. The local delivery of vaccinia virus expressing B7.1 was well tolerated and represents an innovative strategy for altering the local tumor microenvironment in patients with melanoma.

Figures

Figure 1

Patient 3 received 3 intratumoral injections of rV-B7.1 (4.26 × 107 PFU) in a left inguinal subcutaneous melanoma lesion. Following the last vaccine she developed new autoimmune vitiligo involving the right lower chin (A) and a skin graft donor site on the right lateral thigh (B). She had a complete response of metastatic disease, and excision of the left inguinal melanoma revealed necrotic tumor. She has had no evidence of recurrent disease for more than 59 months.

Figure 2

Local delivery of rV-B7.1–induced gp100- and MART-1–specific T cell response in peripheral blood lymphocytes 6 months after vaccination. T cell response was measured by IFN-γ ELISPOT assay after 7 days of IVS with an HLA-A*0201–restricted MART-1 peptide or a mixture of 3 gp100 peptides. In patient 3, a dramatic increase in both gp100 and MART-1 T cell responses was seen by IFN-γ ELISPOT assay 3 months after completion of the vaccine trial (month 6), and she is alive without disease recurrence more than 59 months later without other therapy. Pre-Tx, pretreatment.

Figure 3

The gene expression levels of CD8, IFN-γ, and IL-10 in the tumor microenvironment were altered by local rV-B7.1 vaccination. RNA was amplified from FNAs obtained before and after vaccination. (A) Logarithmic changes of target genes corrected by PKG-1 endogenous control values are shown for 5 index lesions. Postvaccination gene expression of CD8, IFN-γ, and IL-10 in index lesions from patients 3, 4, 5, 7 and 9 classified as SD, PR, or PD are shown. ND, not determined. (B) Postvaccination gene expression levels of CD8, IFN-γ, and IL-10 are shown for patient 4, classified as PR, throughout the administration of 3 vaccine cycles (9 injections of rV-B7.1). The specific injection number within each cycle is indicated. Post, postvaccination; pre, prevaccination. (C) Measurements of the index lesion area (cm2) of patient 4 corresponding to the gene transcript levels in B are shown.