Study On Complement C3d Enhancement Of Pseudorabies Virus GC Gene Immunogenicity

Pseudorabies, also designated as Aujeszky's disease (AD), is a serious illness of swine and causes significant financial losses in the pig industry. To control AD and to reduce economic losses in the pig industry, active immunization with modified live or inactivated vaccines has been performed widely. Although these vaccines can provide protection against clinical signs of AD in swine to some degrees, they have certain defects, especially limited protective efficacy and the danger of reversion to a more virulent strain. Therefore, it is urgent to develop safer and more effective vaccines to control this disease.Recently DNA vaccines to PrV have been actively studied. It was demonstrated that DNA expressing major glycoproteins of PrV gB, gC, and gD, which are involved in essential steps of viral infection, confers protective immunity in pigs and mice. Besides, the DNA vaccine encoding for gB and gD of PrV primed the immune system in the presence of maternal immunity more efficiently than conventional vaccines, and reduced virus excretion earlier after challenge infection. Several approaches were explored to enhance the immunity of DNA vaccines to PrV such as using a Sindbis virus DNA-based expression vector, genetic adjuvants granulocyte macrophage-colony stimulating factor (GM-CSF) gene, CpG motif, IL-2, type 1 interferon, T helper 1-type cytokine, etc. However, although DNA vaccines induce strong cell-mediated immunity, they are challenged by slow antibody rise, compared to protein or attenuated viral vaccines. The use of complement-tagged proteins as antigens was demonstrated to be effective approach to enhance humoral immunity. C3d, the activated complement product were able to augument humoral immunity to both the couple proteins or expressed fusion protein in DNA vaccine.Based on the above mentioned research background, the present study investigated the immunogenicity and protective efficacy of DNA vaccine encoding the immunogenic PrV glycoprotein C (gC) fused to complement C3d or M28 (complement C3d receptor binding domain), and evaluated the immunogenicity to the fusion protein of gC with three copies of porcine homolog complement C3d. The main results are as follows:1. Cloning and sequence analysis of murine, porcine and goatcomplement C3dTotal cell RNA was extracted from the liver tissue of mouse,pig and goat, and the cDNA of C3d was amplified by reverse transcription polymerase chain reaction(RT-PCR). The bioinformatics analysis was performed to predict the structure and function of...