Vaccination With a FAT1-Derived B Cell Epitope Combined With Tumor-Specific B and T Cell Epitopes Elicits Additive Protection in Cancer Mouse Models

Abstract

Human FAT1 is overexpressed on the surface of most colorectal cancers (CRCs) and in particular a 25 amino acid sequence (D8) present in one of the 34 cadherin extracellular repeats carries the epitope recognized by mAb198.3, a monoclonal antibody which partially protects mice from the challenge with human CRC cell lines in xenograft mouse models. Here we present data in immune competent mice demonstrating the potential of the D8-FAT1 epitope as CRC cancer vaccine. We first demonstrated that the mouse homolog of D8-FAT1 (mD8-FAT1) is also expressed on the surface of CT26 and B16F10 murine cell lines. We then engineered bacterial outer membranes vesicles (OMVs) with mD8-FAT1 and we showed that immunization of BALB/c and C57bl6 mice with engineered OMVs elicited anti-mD8-FAT1 antibodies and partially protected mice from the challenge against CT26 and EGFRvIII-B16F10 cell lines, respectively. We also show that when combined with OMVs decorated with the EGFRvIII B cell epitope or with OMVs carrying five tumor-specific CD4+ T cells neoepitopes, mD8-FAT1 OMVs conferred robust protection against tumor challenge in C57bl6 and BALB/c mice, respectively. Considering that FAT1 is overexpressed in both KRAS+ and KRAS− CRCs, these data support the development of anti-CRC cancer vaccines in which the D8-FAT1 epitope is used in combination with other CRC-specific antigens, including mutation-derived neoepitopes.

Proteome‐minimized outer membrane vesicles from Escherichia coli as a generalized vaccine platform

“…We next investigated whether the removal of the OMV endogenous proteins could have affected the loading capacity of OMVs. We previously showed that foreign antigens and epitopes efficiently compartmentalize in OMVs when their coding sequences are either directly fused to a lipoprotein leader sequence (Irene et al., 2019) or hooked to the C‐terminus of an OMV‐associated lipoprotein (Grandi et al., 2017, 2018). Therefore, we selected ten heterologous proteins and epitopes, we expressed them as lipidated antigens in both E. coli BL21(DE3) ΔompA and E. coli BL21(DE3) Δ60 and we purified the vesicles from each recombinant strain.…”

“…FhuD2, Hla H35L are two S. aureus protective antigens (Irene et al., 2019). FhuD2‐mFAT1 is a C‐terminal fusion carrying the murine homolog of a surface‐exposed epitope of FAT1, a protein found overexpressed in colorectal cancer (Grandi et al., 2018; Pileri et al., 2016). Finally, FhuD2‐Bp is a fusion carrying three copies of an immunogenic epitope (TRMQTQINGLNQGVSNAND) from Burkholderia pseudomallei flagellin separated by a short linker sequence (GS).…”

“…Plasmids encoding FhuD2, SpA KKAA , Csa1, Hla H35L , FhuD2‐mFAT1 and Nm‐NHBA were already described (Fantappiè et al., 2017; Grandi et al., 2018; Irene et al., 2019). For the construction of plasmids encoding ClfA Y338A , FhuD2‐Bp, FhuD2‐OVA and FhuD2‐hFAT1, the PIPE‐PCR method was used (Klock & Lesley, 2009).…”

“…Percentage of OVA‐ and SV40‐specific T cells in immunized mice was performed as previously described (Grandi et al., 2018). Statistical significance was assessed using two‐tailed Student's t ‐test.…”

Commensal Bifidobacterium Strains Enhance the Efficacy of Neo-Epitope Based Cancer Vaccines

“…In this work, we have investigated whether and to what extent the gut microbiome can influence the antitumor activity of neo-epitope-based cancer vaccines. To address this question we have used the BALB/c-CT26 murine tumor model and we have tested whether the efficacy of a vaccine constituted by OMVs decorated with five CT26-specific neoepitopes [12,16] could be potentiated by Bifidobacterium administration during vaccination. Here, we show that Bifidobacterium administration per se has a beneficial effect on tumor growth inhibition.…”