Advances in methods for the production, purification, and characterization of HIV-1 Gag–Env pseudovirion vaccines

HIV pseudovirion or virus-like particle vaccines represent a promising approach for eliciting humoral and cellular immune responses. Pseudovirions present the envelope glycoprotein complex in its authentic trimeric form, and thus have the potential to generate neutralizing antibodies against relevant virion-associated epitopes that may be lacking in protein subunit vaccines. The development of pseudovirion particles as a viable vaccine approach for progression to clinical testing has been limited by a number of factors, including shedding of particle-associated gp120, practical limitations to large-scale production and purification, and the generation of antibodies against cellular proteins incorporated on the particle surface that confound the analysis of HIV-specific neutralizing antibody responses. Here, we review methods that address each of these challenges, with a focus on production methods for generating non-infectious Gag–Env pseudovirions. Mammalian cell lines that inducibly express HIV Gag and Env can overcome production limitations, and produce pseudovirions that retain gp120 following purification. Baculovirus production systems have the potential to provide higher quantities of particles, but cleavage of gp160 remains a current limitation. Anti-cellular antibody responses can be diminished by adsorption with cell lysates or whole cells. These technical advances should facilitate the further development of pseudovirion vaccine approaches in preclinical testing and future clinical trials.