An oral WT1 protein vaccine composed of WT1-anchored, genetically engineered Bifidobacterium longum allows for intestinal immunity in mice with acute myeloid leukemia

Abstract

Wilms’ tumor 1 (WT1) is a promising tumor-associated antigen for cancer immunotherapy. We developed an oral protein vaccine platform composed of WT1-anchored, genetically engineered Bifidobacterium longum (B. longum) and conducted an in vivo study in mice to examine its anticancer activity. Mice were orally treated with phosphate-buffered saline, wild-type B. longum105-A, B. longum 2012 displaying only galacto-N-biose/lacto-N-biose I-binding protein (GLBP), and WT1 protein- and GLBP-expressing B. longum 420. Tumor size reduced significantly in the B. longum 420 group than in the B. longum 105-A and 2012 groups (P < 0.00 l each), indicating B. longum 420’s antitumor activity via WT1-specific immune responses. CD8+ T cells played a major role in the antitumor activity of B. longum 420. The proportion of CD103+CD11b+CD11c+ dendritic cells (DCs) increased in the Peyer’s patches (PPs) from mice in the B. longum 420 group, indicating the definite activation of DCs. In the PPs, the number and proportion of CD8+ T cells capable of producing interferon-gamma were significantly greater in the B. longum 420 group than in the B. longum 2012 group (P < 0.05 or < 0.01). The production of WT1-specific IgG antibody was significantly higher in the B. longum 420 group than in the 2012 group (P < 0.05). The B. longum 420 group showed the most intense intratumoral infiltration of CD4+ and CD8+ T cells primed by activated DCs in the PPs of mice in the B. longum 420 group. Our findings provide insights into a novel, intestinal bacterium-based, cancer immunotherapy through intestinal immunity.

Enhanced antitumor activity of a novel, oral, helper epitope-containing WT1 protein vaccine in a model of murine leukemia

“…Among these, we selected WT1 35 as an epitope with the most potent IFN-γ-producing capability of CD4 + T cells that strengthen the CTL-induced WT1-specific lysis of RMAS cells pulsed with WT1 35–52 peptide, suggesting its great potential of inducing CD4 + T cell help that provides critical cellular and molecular mechanisms in CTL responses in cancer immunotherapy [ 12 ]. In addition, Nakagawa et al demonstrated that an oral WT1 protein vaccine of WT1-anchored, genetically engineered B. longum provokes intestinal immunity to exert the cytotoxic activity of WT1-specific CD8 + T cells possibly through CD4 + T cell help [ 16 ]. Results from the present study indicate that the combination of B. longum 420 and B. longum 2656 exhibited the most enhanced anticancer activity in intestinal immunity among studied materials, supporting the reasonable therapeutic strategy of genetically engineering a WT1 amino acid sequence 35–52 into an oral B. longum -based vaccine structure.…”

“…Recent technologies including flow cytometry and single-cell RNA sequencing provide an unprecedented view of the composition, function, and location of immunocompetent cells within the tumor microenvironment (TME) [ 17 ]. Our data on TILs indicate 1) the increased frequency of WT1-specific CTLs in CD8 + T cells, 2) the obvious production of WT1-specific IFN-γ by CD4 + T cells, and 3) the strengthened tumor-infiltrating capability of WT1-specific CTLs primed in the intestine [ 16 ], all of which afford flow cytometric evidence about the antitumor activity of combining B. longum 420 for WT1-specific CD8 + T cell activation and B. longum 2656 for CD4 + T cell help.…”

“…Our previous study [ 16 ], in which mice were orally treated B. longum wild type, B. longum wild type displaying only GLBP, and B. longum 420, provided insights into a novel, intestinal bacterium-based, cancer immunotherapy through intestinal immunity and afforded the following findings: 1) CD8 + T cells played a central role in the cytotoxic activity of B. longum 420; 2) only B. longum 420 augmented the efficiency of T cell priming; and 3) CD4 + T cell help was evidenced by the production of anti-WT1 IgG antibody and by the increased number and proportion of IFN-γ-producing CD4 + T cells in the Peyer’s patches (PPs) and mesenteric lymph nodes. Intestinal immunity is an attractive immune mechanism in intestinal bacterium-based, cancer immunotherapy because an oral peptide/protein vaccine stimulates lamina propria and PP immune cells (e.g., DCs, T- and B-cells, and macrophages) and these stimulated immune cells may reach systemic circulation through lymphocyte network—the site where the efficient recognition and presentation of a TAA by DCs occur.…”

An oral cancer vaccine using a Bifidobacterium vector enhances the efficacy of combination therapy with anti-PD-1 and anti-CTLA-4 antibodies in a mouse renal cell carcinoma model

“…The fundamental principle of cancer immunotherapy, including ICI, is to induce or activate tumor-speci c cellular immunity. Many studies have been conducted on cancer vaccines that can arti cially induce tumor immunity and can be used in combination with ICI 4,5 . Cancer vaccines, which can forcibly induce tumor-speci c cellular immunity through antigen presentation to dendritic cells, are a promising treatment strategy for enhancing the e cacy of cancer immunotherapy 5,6 .…”

“…Many studies have been conducted on cancer vaccines that can arti cially induce tumor immunity and can be used in combination with ICI 4,5 . Cancer vaccines, which can forcibly induce tumor-speci c cellular immunity through antigen presentation to dendritic cells, are a promising treatment strategy for enhancing the e cacy of cancer immunotherapy 5,6 . The National Cancer Institute has ranked tumor associated antigens (TAA) as targets for cancer vaccines based on criteria such as therapeutic e cacy, immunogenicity, carcinogenicity, speci city, expression level and positive cell rate.…”