| HIV is single-stranded, positive-sense RNA virus and belongs to retrovirus family. Because of the characteristics of high mutation, recombination and replication, its genome can mutate rapidly and a number of mutant strains appear. These virus can escape the immune pressure of host successfully and lead to more and more HIV-infected persons or AIDS patients.Nef (Negative factor) is an N-terminally myristoylated protein. Although nef is dispensable for virus replication in vitro, it has been shown that nef plays an important role in HIV-1 pathogenesis in vivo. Many functions of nef have been intensively studied. Since nef gene was cloned decades ago, thousand of papers have been published about the in vitro functions of nef. These findings have defined four main functions of nef, including modulation of cell surface molecule expression, enhancement of viral infectivity, interference of cellular signal transduction, and manipulation of the apoptosis mechanism. Although the biological relevance of theses findings still remains to be determined, it suggests a link between the in vitro functions of nef and its role in HIV-1 pathogenesis in vivo.It has been verified that DNA vaccine can elicit protective immune response mediated by humoral and cellular immunity in several virus-infected animal models. The rising and development of DNA vaccine provide a new way for prevention and treatment of HIV infection. DNA vaccines could induce humoral and cellular immunity, it is superior to recombinant protein vaccine and peptide vaccine, especially in inducing cellular immune responses.There is a great difference among the immune effects of DNA vaccine in different animals. It is difficult to induce effective immune responses for some tumor and virus antigens with weak T or B cell epitope and many strategies have been employed to improve the effect of DNA vaccines. Genetic adjuvant is constructed by cloning genes encoding cytokines and costimulators into the same vector or different vectors with target genes. After co-immunization with DNA vaccine, the expressed protein could play the role in enhancing the immune responses as the adjuvant.LIGHT is a member of the TNF superfamily and functions as a costimulatory molecule for T cell proliferation. LIGHT plays a role in costimulating and takes part in T cell proliferation and the production of cytokines through combining with HVEM, a receptor of LIGHT for mediating T cell activation. More and more studies suggest that the interaction of LIGHT and its receptors could be a potential target for controlling cellular immune responses. Considering the important roles in HIV infection of nef, it has great significance to prepare DNA vaccine and study its immune effects using nef as the target gene. In the research, a prokaryotic expression plasmid pET24-Nef harboring nef gene was constructed and the expression of nef protein were studied in E.coli BL21. The rabbit was immunized with recombinant Nef protein and high titers of sera against HIV-1 Nef were acquired. The eukaryotic expression plasmid pcDNA-Nef was constructed by inserting full-length nef gene into pcDNA3.1(+) and transfection in vitro has demonstrated that nef gene was expressed successfully in mammalian cells. Balb/c mice were immunized with HIV-1 Nef DNA vaccine plasmids alone or in combination with LIGHT expression plasmids. The results of humoral and cellular immune responses suggested that HIV-1 Nef DNA vaccine plasmids alone could elicit strong specific immune responses in mice. The stronger specific immune responses in mice were induced when coimmunizing HIV-1 Nef DNA vaccine plasmids with LIGHT expression plasmids, suggesting that LIGHT performed the function as immune adjuvant.
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