The present invention relates to a novel chimeric nucleic acid molecule of porcine circovirus (PCV2Gen-lRep) that embraces a nucleic acid molecule encoding porcine circovirus type 2 (PCV2) which contains a nucleic acid sequence encoding a Rep protein of porcine circovirus type 1 (PCVl), particularly wherein the nucleic acid sequence encoding the Rep protein of PCVl is an open reading frame (ORF) gene and, more particularly, wherein the ORF Rep gene is ORFl. A highly desirable chimeric nucleic acid molecule is constructed by replacing the ORFl Rep gene of PCV2 by the ORFl Rep gene of PCVl. The invention also encompasses the biologically functional plasmid or viral vector containing the unique chimeric nucleic acid molecules, suitable host cells transfected by the plasmid or vector, infectious chimeric porcine circoviruses that are produced by the suitable host cells, the process for the production of an immunogenic polypeptide product making use of the new chimera, viral vaccines that protect a pig against viral infection or postweaning multisystemic wasting syndrome (PMWS) caused by PCV2, methods of protecting a pig against viral infection or postweaning multisystemic wasting syndrome (PMWS) caused by PCV2, methods of preparing the unique chimera of PCV2Gen-lRep and the like. This invention further includes a new method for improving the replication and titer of PCV2 in a cell culture.La présente invention porte sur une nouvelle molécule dacide nucléique chimérique du circovirus porcin (PCV2Gen-1Rep) qui englobe une molécule dacide nucléique codant pour le circovirus porcin de type 2 (PCV2) qui contient une séquence dacide nucléique codant pour une protéine Rep du circovirus porcin de type 1 (PCV1), en particulier dans laquelle la séquence dacide nucléique codant pour la protéine Rep de PCV1 est un gène de cadre de lecture ouvert (ORF) et, plus particulièrement, dans laquelle le gène Rep ORF est ORF1. Une molécule dacide nucléique chimérique hautement souhaitable es
