Libraries of human rhinovirus-based HIV vaccines generated using random systematic mutagenesis

Human rhinovirus (HRV), an immunogenic and relatively nonpathogenic virus, has been engineered to display HIV-1 immunogens with the intent of developing a vaccine against AIDS. HIV immunogens from the V3 loop have been placed into the neutralizing immunogenic (NIm) sites on the surface of HRV14 naturally recognized by the immune system. To increase the likelihood of recovering viable chimeras displaying the transplanted HIV-1 V3 loop sequences in conformations that mimic that of HIV, we have used random systematic mutagenesis to produce libraries of chimeric HRV14 in which the transplanted epitope from HIV-1 is flanked by one or more randomized amino acid residues. This allows the HIV epitope to be accommodated into the HRV coat proteins in many conformations, some of which should result in the production of viable, immunogenic hybrids. Using this approach, a library containing the sequence XXIGPGRAXX, where X could be any of the 20 amino acids, was generated. A nonrandom distribution of residues was found at the randomized positions, which may be a reflection of the structural requirements for viability. A subset of chimeras was identified that reacted with neutralizing anti-HIV-1 V3 loop antibody preparations, indicating that the antigenicity of the epitopes had been transplanted. Another chimeric virus library was designed to reflect the natural diversity of the V3 loop by incorporating amino acids at frequencies similar to those found among naturally occurring isolates of HIV-1. Powerful selection techniques utilizing anti-HIV-1 V3 loop neutralizing antibodies are being employed to isolate efficiently antigenic chimeras that could serve as potential vaccine candidates.