Virus-like Particles: a Novel Tool for the Induction and Monitoring of Both T-helper and Cytotoxic T-lymphocyte Activity

T-cells play a crucial role in the control of various viral infections such as HIV and herpes viruses. Thus, the development of advanced techniques for the stimulation and measurement of both antigen-specific T-helper and CTL responses is one of most meaningful objectives in vaccinology. Herein, we present HIV-1 Pr55gag lipoprotein particles (VLPs) to be a potent antigen for introducing epitopes into the MHC-class-I and -II processing and presentation pathway. These VLPs can easily be produced in insect cells by using the baculovirus expression system. Immunization studies in mice revealed the strong capacity of these VLPs to stimulate Gag-specific T-helper-1 cell-biased humoral and cellular immune responses. In addition, these VLPs can be used as a stimulator antigen for the detection of Gag-specific T-helper and CTL responses, as determined by conventional ELISA, ELISpot, FACS, and 51Cr-release assays. These results strongly underline the value of VLPs as a stimulator of MHC-class-I and -II mediated epitope presentation for preventive, therapeutic, and diagnostic purposes.