Design and immunogenicity assessment of HIV-1 virus-like particles as a candidate vaccine

Zhang, XiZhen; Wang, XiaoDan; Zhao, DongHai; Meng, XiangYu; Zhao, XingHong; Yu, XiangHui; Kong, Wei

The plasmid pNL4-3.Luc.R-E contains luciferase and the full HIV-1 genome of except for a frameshift mutation in the Env gene. The 293 T cells expressed constitutive Gag and Env following cotransfection of plasmids pNL4-3.Luc.R-E and pcDNA 3.1 EnvB/C, which contained the Env gene. These two proteins could be packaged into virus particles wherein the particle also contained luciferase. Such a particle is referred to as a pseudotype virus since it cannot replicate, but can infect HOS-CD4-CCR5 cells and the infection level could be detected by quantifying luciferase activity. The neutralization level could be evaluated by co-incubating blood samples and cotransfected supernatants and observing the change in luciferase. Our results showed that 0.5 g of VLPs could induce neutralizing antibody and that antibody levels increased as the immunizing dose increased. These antibodies could also counteract the infectivity of the pseudotype virus. The epitopes of the neutralizing antibodies resided mainly in Pr55gag and gp120. Neutralization activity was highest in VLPs samples 12.5 g, and 25 g, as indicated by the low luciferase activity. Interestingly, 100 g plasmid DNA could only elicit a lower level neutralization activity than all VLPs amounts tested. It is also conceivable that 12.5 ug is the optimal dose. The neutralization level in different dose groups tended to be similar at 1:1, 1:2 and 1:4 dilution ( Figure 8 ).