Table 1.

Main characteristics of glioblastoma microenvironment as described in the literature or observed in H-1 parvovirus-treated glioblastoma patients.

Glioblastoma Microenvironment (Literature Data)	Glioblastoma Microenvironment (First Parvovirus Clinical Trial)
sparse inflammatory infiltrates (except the mesenchymal transcriptional class) [63]	tumor infiltration with CD8+/granzyme B+ T cells [45]
tumor-infiltrating lymphocyte involvement in inhibitory (e.g., via PD-1) interactions [8]	PD-1-negative tumor-infiltrating T cells
increased numbers of tumor-infiltrating Treg cells [64]	Treg cells only scarcely detected [45]
M2 tumor-supportive tumor-associated microglia/macrophage (TAM) phenotype [51]	detection of markers of M1 TAM polarization (CD68, CTSB, iNOS) [45]
release of immunosuppressive factors and anti-inflammatory cytokines [8]	detection of proinflammatory cytokines (IFN-γ, IL-2) [45]

PD-1, programmed cell death protein 1; Treg, regulatory T cell; M2, macrophage phenotype 2; CD, cluster of differentiation; CTSB, cathepsin B; iNOS, inducible nitric oxide synthase; IFN-γ, interferon gamma; IL-2, interleukin 2.