Recruitment of Oligoclonal Viral-Specific T cells to Kill Human Tumor Cells Using Single-Chain Antibody–Peptide–HLA Fusion Molecules

Abstract

Tumor progression is often associated with the development of diverse immune escape mechanisms. One of the main tumor escape mechanism is HLA loss, in which human solid tumors exhibit alterations in HLA expression. Moreover, tumors that present immunogenic peptides via class I MHC molecules are not susceptible to CTL-mediated lysis, because of the relatively low potency of the tumor-specific CLTs. Here, we present a novel cancer immunotherapy approach that overcomes these problems by using the high affinity and specificity of antitumor antibodies to recruit potent antiviral memory CTLs to attack tumor cells. We constructed a recombinant molecule by genetic fusion of a cytomegalovirus (CMV)-derived peptide pp65 (NLVPMVATV) to scHLA-A2 molecules that were genetically fused to a single-chain Fv Ab fragment specific for the tumor cell surface antigen mesothelin. This fully covalent fusion molecule was expressed in E. coli as inclusion bodies and refolded in vitro. The fusion molecules could specifically bind mesothelin-expressing cells and mediate their lysis by NLVPMVATV-specific HLA-A2-restricted human CTLs. More importantly, these molecules exhibited very potent antitumor activity in vivo in a nude mouse model bearing preestablished human tumor xenografts that were adoptively transferred along with human memory CTLs. These results represent a novel and powerful approach to immunotherapy for solid tumors, as demonstrated by the ability of the CMV-scHLA-A2-SS1(scFv) fusion molecule to mediate specific and efficient recruitment of CMV-specific CTLs to kill tumor cells.

Applications of Anti-Cytomegalovirus T Cells for Cancer (Immuno)Therapy

“…Due to the above-mentioned beneficial characteristics of anti-CMV CD8 pos T cells, such as their abundance and constant renewability, various strategies have been developed to exploit these potent cytolytic effector cells for cancer immunotherapy. In contrast to naïve T cells, antigen-experienced inflationary anti-CMV CD8 pos T cells do not require classical priming through presentation of peptides by dendritic cells or other professional antigen-presenting cells [38].…”

“…These fusion proteins bind to the respective target antigen that is selectively (over)expressed on the surface of cancer cells via their antibody domain and thereby 'present' exogenous CMV peptide-HLA-I complexes. Anti-CMV CD8 pos T cells can then recognize and eliminate CMV peptide-presenting cancer cells Noy et al (2015). constructed a recombinant molecule, designated CMV-scHLA-A2-SS1(scFv), by genetic fusion of the CMV pp65 peptide epitope NLV to the singlechain (sc)HLA-A*02:01 molecule and scFv anti-mesothelin antibody fragment SS1[38].…”

“…Anti-CMV CD8 pos T cells can then recognize and eliminate CMV peptide-presenting cancer cells Noy et al (2015). constructed a recombinant molecule, designated CMV-scHLA-A2-SS1(scFv), by genetic fusion of the CMV pp65 peptide epitope NLV to the singlechain (sc)HLA-A*02:01 molecule and scFv anti-mesothelin antibody fragment SS1[38]. In the presence of anti-CMV CD8 pos T cells, CMV-scHLA-A2-SS1(scFv) induced elimination of various cancer cell lines.…”