Efficient induction of T‐cell responses to carcinoembryonic antigen by a heterologous prime‐boost regimen using DNA and adenovirus vectors carrying a codon usage optimized cDNA

Abstract

The immunogenic properties of plasmid DNA and recombinant adenovirus (Ad) encoding the carcinoembryonic antigen (CEA) were examined in mice by measuring both the amplitude and type of immune response, and the immunogenicity of codon usage optimized cDNA encoding CEA (CEAopt) was assessed both in C57Bl/6 and CEA transgenic mice. Vectors were injected into quadriceps muscle either alone or in combination, and plasmid DNA was electroporated to enhance gene expression efficiency and immunogenicity. Injection of plasmid pVIJ/CEA followed by Ad-CEA boost elicited the highest amplitude of both CD4 1 and CD8 1 T-cell response to the target antigen, measured by both IFNc-ELIspot assay and intracellular staining. Vectors carrying cDNA of CEAopt expressed a greater amount of the CEA protein than their wild-type counterparts, and this enhanced expression was associated with greater immunogenicity. Both CD4 1 and CD8 1 T-cell epitopes were mapped in the C-terminal portion of the protein. In CEA transgenic mice, only immunization based on repeated injections of pVIJ/ CEAopt followed by Ad-CEAopt was able to elicit a CEA-specific CD8 1 T-cell response, whereas the wild-type vectors did not break tolerance to this target antigen. MC38-CEA tumor cells injected s.c. in CEA transgenic mice vaccinated with CEAopt vectors exhibited delayed growth kinetics. These studies demonstrate that this type of genetic vaccine is highly immunogenic and can break tolerance to CEA tumor antigen in CEA transgenic mice. ' 2005 Wiley-Liss, Inc.Key words: CEA; DNA electroporation; adenovirus Despite improvements in prevention, early detection and treatment, the possibility of curing many cancer patients remains elusive. Thus, cancer continues to be a largely unmet medical need for which more efficient therapeutic strategies must be developed. 1 Particular attention has been given to active specific immunotherapy of cancer, whereby patients are immunized against antigens presented by tumor cells. In fact, experimental and clinical evidence have demonstrated the critical role played by the cellular and humoral responses in controlling tumor growth and metastasis. 2 Many of these therapies are specifically targeted to tumorassociated antigens among which carcinoembryonic antigen (CEA) is a frequent example due to its ectopic and deregulated expression in a large percentage of adenocarcinomas. 3 Human CEA is the prototypic member of the human CEA family, a group of highly glycosylated homotypic/heterotypic cell surface intracellular adhesion molecules, and part of the immunoglobulin gene superfamily. CEA is widely used as human tumor marker, is expressed mostly in the gastrointestinal tract and is overexpressed in many human cancers, including epithelial tumors originating from the gastrointestinal tract, lung, thyroid, breast, prostate, cervix and ovaries. 4 CEA has been the focus of extensive preclinical and clinical investigation aimed at developing a CEA-specific vaccine with a therapeutic impact on tumor progression. 5 In this context, genetic vacc...

Enhancing Th2 immune responses against amyloid protein by a DNA prime-adenovirus boost regimen for Alzheimer's disease

“…A number of DNA prime-adenovirus boost regimens were intended to induce cellular immune responses through intramuscular injection [42][43][44][45][46][47][48][49]. Some research groups, however, reported that DNA prime-virus boost regimens stimulated strong humoral immune responses.…”

CD4+CD25+ regulatory T-cell-inactivation in combination with adenovirus vaccines enhances T-cell responses and protects mice from tumor challenge

“…8 Here, we evaluated whether the administration of anti-CD25 mAb could enhance the CEA-specific immune responses.…”

“…8 The same CEA codon optimized expression cassette was inserted in an Ad serotype 6 generating Ad6-CEA.…”

Genetic vaccines against Ep‐CAM break tolerance to self in a limited subset of subjects: Initial identification of predictive biomarkers

“…DNA vaccination in mice was performed via both electroporation according to Rizzuto et al [32] and adenovirus vaccination according to Mennuni et al [17]. Monkey immunization studies were performed at The Biomedical Primate Research Center (BPRC, Rijswijk, The Netherlands) using a group of four rhesus macaques (Macaca mulatta).…”

“…It was also shown in rhesus macaques that a mixed vaccination modality, such as DNA followed by adenovirus, later may elicit a more effective immune response including a persistent CD8 response [16]. We have previously assessed the efficacy of a mixed-modality DNA-EP/Adeno against carcinoembryonic antigen (CEA) in hCEA-transgenic mice and showed this vaccine to be able to induce anti-CEA cellmediated immunity as well as partial protection from subsequent tumor challenge [17]. In the present study, we have therefore started to evaluate Ep-CAM as immunogen when delivered by DNA-EP and adenovirus.…”