Antitumor immunopreventive effect in mice induced by DNA vaccine encoding a fusion protein of -fetoprotein and CTLA4

Abstract

AIM:To develop a tumor DNA vaccine encoding a fusion protein of murine AFP and CTLA4, and to study its ability to induce specific CTL response and its protective effect against AFP-producing tumor. METHODS:Murine α-fetoprotein (mAFP) gene was cloned from total RNA of Hepa1-6 cells by RT-PCR. A DNA vaccine was constructed by fusion murine α-fetoprotein gene and extramembrane domain of murine CTLA4 gene. The DNA vaccine was identified by restriction enzyme analysis, sequencing and expression. EL-4 (mAFP) was developed by stable transfection of EL-4 cells with pmAFP. The frequency of cells producing IFN-γ in splenocytes harvested from the immunized mice was measured by ELISPOT. Mice immunized with DNA vaccine were inoculated with EL-4 (mAFP) cells in back to observe the protective effect of immunization on tumor. On the other hand, blood samples were collected from the immunized mice to check the functions of liver and kidney.RESULTS: 1.8 kb mAFP cDNA was cloned from total RNA of Hepa1-6 cells by RT-PCR. The DNA vaccine encoding a fusion protein of mAFP-CTLA4 was constructed and confirmed by restriction enzyme analysis, sequencing and expression. The expression of mAFP mRNA in EL-4 (mAFP) was confirmed by RT-PCR. The ELISPOT results showed that the number of IFN-γ-producing cells in pmAFP-CTLA4 group was significantly higher than that in pmAFP, pcDNA3.1 and PBS group. The tumor volume in pmAFP-CTLA4 group was significantly smaller than that in pmAFP, pcDNA3.1 and PBS group, respectively. The hepatic and kidney functions in each group were not altered.CONCLUSION: AFP-CTLA4 DNA vaccine can stimulate potent specific CTL responses and has distinctive antitumor effect on AFP-producing tumor. The vaccine has no impact on the function of mouse liver and kidney.Tian G, Yi JL, Xiong P. Antitumor immunopreventive effect in mice induced by DNA vaccine encoding a fusion protein of α-fetoprotein and CTLA4.

Enhancement of immunotherapeutic effects of HPV16E7 on cervical cancer by fusion with CTLA4 extracellular region

“…Huang et al (2000) reported that even at a relatively high dose of 50 mg of CTLA4-Ig, B-7 molecules remain available to engage with CD28 and thereby provide a signal for T-cell activation. Our present results and those reported previously by other workers on vaccination with Id-CTLA4, DNA encoding CTLA4-Ig, and DNA vaccines fused with CTLA4 provide lines of evidence that CTLA4-Ig at low levels increases both Ab and T-cell proliferation responses (Boyle et al, 1998;Deliyannis et al, 2000;Nayak et al, 2003;Tian et al, 2004). An alternative explain is, under certain circumstances, CTLA4-Ig can augment immunity.…”

“…In several studies, DNA vaccines harnessing fusion CTLA4 to antigen were exploited for antitumor and antivirus purposes (Boyle et al, 1998;Deliyannis et al, 2000;Nayak et al, 2003;Tian et al, 2004). Our present study sought to assess the efficacy of a novel fusion protein consisting of modified HPV16E7 and the extracellular region of human CTLA4 in the immunotherapy of tumor models expressing HPV16E6E7 protein.…”

Strategies for Successful Vaccination against Hepatocellular Carcinoma

“…A combined DNA vaccine encoding a fusion protein of AFP and CTLA-4 antigen (that binds co-stimulatory B7-1 and B7-2 molecules) obtained both potent specific CTL response and antitumor effect on AFP-producing tumor in mice, without impairing hepatic and renal functions (29). Also uncharacterized and mutated antigens can be targeted with whole tumor cell or tumor lysate-based immunization strategies , as well as using vectors bearing genes making tumor cells immunogenic ; the immune system in these instances shall evolve specificity against these new immunogenic target antigens.…”