Antigen-specific immune responses and clinical outcome after vaccination with glioma-associated antigen peptides and polyinosinic-polycytidylic acid stabilized by lysine and carboxymethylcellulose in children with newly diagnosed malignant brainstem and nonbrainstem gliomas

Abstract

Purpose: Diffuse brainstem gliomas (BSGs) and other high-grade gliomas (HGGs) of childhood carry a dismal prognosis despite current treatments, and new therapies are needed. Having identified a series of glioma-associated antigens (GAAs) commonly overexpressed in pediatric gliomas, we initiated a pilot study of subcutaneous vaccinations with GAA epitope peptides in HLA-A2-positive children with newly diagnosed BSG and HGG.

Patients and methods: GAAs were EphA2, interleukin-13 receptor alpha 2 (IL-13Rα2), and survivin, and their peptide epitopes were emulsified in Montanide-ISA-51 and given every 3 weeks with intramuscular polyinosinic-polycytidylic acid stabilized by lysine and carboxymethylcellulose for eight courses, followed by booster vaccinations every 6 weeks. Primary end points were safety and T-cell responses against vaccine-targeted GAA epitopes. Treatment response was evaluated clinically and by magnetic resonance imaging.

Results: Twenty-six children were enrolled, 14 with newly diagnosed BSG treated with irradiation and 12 with newly diagnosed BSG or HGG treated with irradiation and concurrent chemotherapy. No dose-limiting non-CNS toxicity was encountered. Five children had symptomatic pseudoprogression, which responded to dexamethasone and was associated with prolonged survival. Only two patients had progressive disease during the first two vaccine courses; 19 had stable disease, two had partial responses, one had a minor response, and two had prolonged disease-free status after surgery. Enzyme-linked immunosorbent spot analysis in 21 children showed positive anti-GAA immune responses in 13: to IL-13Rα2 in 10, EphA2 in 11, and survivin in three.

Conclusion: GAA peptide vaccination in children with gliomas is generally well tolerated and has preliminary evidence of immunologic and clinical responses. Careful monitoring and management of pseudoprogression is essential.

Trial registration: ClinicalTrials.gov NCT01130077.

Fig 1.

Magnetic resonance imaging (MRI) results in a responding patient (patient 11), with transient pseudoprogression. In each panel, sagittal T1-weighted gadolinium-enhanced images are on the left, and axial fluid-attenuated inversion recovery images are on the right. (A) MRI scan at diagnosis. (B) MRI scan before vaccine therapy (3 months after diagnosis and start of irradiation). Tumor is unchanged from baseline. (C) Four months after the start of vaccination, the patient had tumor enlargement, increased enhancement, and symptomatic worsening. High-dose dexamethasone was started. (D) The MRI scan shows dramatic reduction of enhancement and mass effect 1 month later (1/16/11). Dexamethasone was weaned, and vaccination was subsequently resumed. The partial response status was then maintained until 18 months after diagnosis.

Fig 2.

(A) Time course of glioma-associated antigen epitope-specific T-cell responses evaluated by interferon-γ enzyme-linked immunosorbent spot (ELISPOT) analyses in 15 patients who had samples available at week 0 (prevaccine) and at the week 6, 15, and 21 time points. Points represent net values after background subtraction. Patients who exhibited progression and did not have data at the week 15 or 21 time points are not shown. (B) ELISPOT results for patient 11, showing a dramatic response to interleukin 13 receptor alpha 2 (IL-13Rα2). The 12/11/10 scan from Figure 1 corresponds to time point A. High-dose steroids were started and the scan and symptoms rapidly and dramatically improved. ELISPOT positivity was diminished after initiation of high-dose dexamethasone (time point B), with subsequent recovery on weaning of dexamethasone.

Fig 3.

Immunohistochemistry results for antigen expression (column A, IL13Rα2; column B, EphA2; column C, survivin) in patients 11 (postmortem specimen) and 13 (pretreatment specimen), illustrating the range of antigen expression observed. Patient 11 had diffuse immunoreactivity for all three antigens, whereas patient 13 had absent expression of EphA2 and low-level expression of survivin in a minority of cells. High levels of expression of interleukin 13 receptor alpha 2 were observed, which was one antigen to which the patient mounted a strong enzyme-linked immunosorbent spot assay response, highlighting the importance of including multiple antigen epitopes in the vaccine cocktail.

Fig 4.

Kaplan-Meier plots of overall survival in 20 patients with brainstem gliomas (BSGs) treated either with (n = 6) or without (n = 14) chemotherapy during irradiation compared with six children with high-grade gliomas (HGGs), all of whom received chemotherapy during irradiation.

Fig A1.

The time course of interleukin-15 (IL-15), macrophage inflammatory protein-1beta (MIP-1β), and monocyte chemotactic protein-1 (MCP-1) expression in serum from patient 22.