Experimental Study On Specific Anti-colorectal Carcinoma Immunity With CEA/B7-1 And CEA/IL-2 Dna Vaccine

Colorecta1 cancer is one of the most common ma1ignant carcinomaof the digestive tract. The main treatment for co1orecta1 cancer isexci sion, but recurrence or metastasi s often occurs postoperat ive1y,which common1y resu1ts in death. If we can do something duringoperation or in early postoperative period to prevent recurrence ormetastasis, the surviva1 time for patients wi11 be pro1ongedremarkab1e1y. At present, chemica1 treatment is the conunon method usedto achieve this, but it is neither specific nor sensitive.Tumor DNA vaccine, a nove1 type of vaccine, e1 icits both humora1and ce11u1ar irmune responses. Ce11u1ar inununity especial1y has beenproved to p1ay the important ro1es in anti--tumor inununity. Since DNAvaccines directly inocu1ate and express in myocyte, via MHC I andMHC 1I of APC or myocyte de1ivering antigen to inunune system, itis not necessary to consider MHC restriction in differentindividuals.Carcinoembryonic Antigen (CEA) is a re1ated antigen which isexpressed in many adenocarcinomas of the digestive systemadenocarcinomas. A1most a11 co1orecta1 cancers express CEA. Inaddition, CEA is a1so an adherence factor that faci1itates theconjugation of tumor and norma1 ce11s, which plays an important ro1ein tumor recurrence and metastasis. However, tumor antigen is so weakin ant igenicity that effective inunune response can not be e1 icited.An important strategy to overcome this insufficiency is combinationof adjuvant and antigen.T ce11 activation is dependent upon signa1s de1ivered throughthe antigen--specific T ce11 receptors and accessory receptors on theT ce11. Costimu1atory factors is the second singa1 for T ce11activation. T--ce11 receptor (TCR) binding with antigen deve1op thefirst singa1 for T ce11 to become active. CD28 on the T ce11 surfacebinding with B7 which is expressed from APC deve1op second singa1. Tce11 can on1y be activated when it receives these two singa1s. If thereis only first singa1, without the second singa1, maybe the T ce1l wi11die or be ionuno1ogica11y unresponsive. Besides B ce11 1yinphoma andsome me1anoma, tumor ce11 do not express B7--1 (CD80) or B7--2 (CD86), sotumor ce11s can easi1y deve1op immuno1ogica1 to1erance. IL--2 is oneof the cytokines that have been studied wide1y. IL--2 produces a markedeffect through the receptor system with distribution in the T, B, NKand K ce11s. The mo1ecu1e direct1y activate the monocytes and induceother histiocytes. When DNA and antigen both inocu1ate, IL--2 uti1 ityamp1ify the B ce11s and T ce11s respond to the antigen. Inaddition, IL--2 is a kind of important T ce11 growth factor. It is neededfor the conversion of irnature T ce11s to TH, or TH, ce11s. Its primaryadjuvant effect is to acce1erate the ce11u1ar inununity response.In this study, we c1oned the CEA cDNA with RT--PCR and constructedthe pIRES expression vector. Taking Carcinoembryonic antigen (CEA)as an examp1e of tumor antigens, CEA cDNA was c1oned from patientssuffering from co1orecta1 carcinoma that where CEA positive.We c1oned the B7--1 and IL--2 cDNA with RT--PCR. The coexpressionplasmid of CEA,B7,land IL－2 were constructed．Further,theireffects as antn－tumor,their aballty to Induce llune response eereS上tidied． Theresultsshowedthat:(l)Threeeukaryotlcexpress。onplasmlds,PIRES－CEA,PIRES－CEA／B7－1,PIRES－CEA／工乙－2,had bPPn Sllccess上＂flyconstructed,transformed Into COS7 cells and expression of twoproteins were demonstrated by ELISA。flow cytometer and elecsy．(2)Inununlzed mince with coexpressson plasmld and controls,showed thatco—dellveryofB7－for IL－2 andCEAcDNAproduces anti一CEA immuneresponse(SI and IL－4)that are sUperior to those generated by thenlasmid DNA encoding CEA alone．(3)pIRES－CEA,pIRES－CEA／B7－landpIRES－CEA／IL－2 can induce mice cellular lllllllunlty and humoral1mLlfllty In vlvo．The lllllllune resPonse of PIRES－CEA／B7－landpIRES－CEA／IL...