Paradigms in HIV vaccine research

Although a large number of preventative human immunodeficiency virus (HIV) vaccine trials have been carried out during the last 30 years, it is remarkable that an effective HIV vaccine has not yet been developed. Research paradigms correspond to theoretical assumptions and particular strategies that scientists use when they try to solve a particular problem. Many paradigms used successfully in vaccinology were ineffective with HIV. For instance: 1) The structure-based reverse vaccinology approach failed because investigators tried to generate a vaccine starting with the antigenic structure of HIV-envelope (Env) epitopes bound to neutralizing monoclonal antibodies (mAbs) derived from HIV-infected individuals. They assumed that this antigenic structure would also possess the immunogenic capacity of inducing in vaccinees a polyclonal antibody (Ab) response with the same neutralizing capacity as the mAb. 2) The structures observed in epitope-paratope crystallographic complexes result from mutually induced fit between the two partners and do not correspond to the structures present in the free molecules before they had interacted. 3) The affinity-matured neutralizing mAbs obtained from chronically infected individuals did not recognize the germline predecessors of these Abs present in vaccinees. 4) The HIV p17 matrix protein that lines the inner surface of the viral membrane is one of the most disordered proteins identified on our planet and this prevents the induced Abs from binding to the glycosylated HIV gp120 protein. 5) Vaccinologists need to solve so-called inverse problems, for instance, guessing what are the multiple causes that produced an earlier wanted beneficial effect such as the absence of deleterious HIV infection in elite controllers. Since the immune system consists of numerous subsystems that have not yet been elucidated, it is impossible to solve the inverse problems posed by each subsystem. 6) Vaccinology is an empirical science that only sometimes succeeds because we do not understand the complex mechanisms that lead to protective immune responses.