Genetic live vaccines mimic the antigenicity but not pathogenicity of liveviruses

The development of an effective HIV vaccine is both a pressing and a formid able problem. The most encouraging results to date have been achieved using live-attenuated immunodeficiency viruses, However, the frequency of pathog enic breakthroughs has been a deterrent to their development, We suggest th at expression libraries generated from viral DNA can produce the immunologi c advantages of live vaccines without risk of reversion to pathogenic virus es, The plasmid libraries could be deconvoluted into useful components or a dministered as complex mixtures, To explore this approach, we designed and tested several of these genetic live vaccines (GLVs) for HIV, We constructe d libraries by cloning overlapping fragments of the proviral genome into ma mmalian expression plasmids, then used them to immunize mice, We found that inserting library fragments into a vector downstream of a secretory gene s equence led to augmented antibody responses, and insertion downstream of a ubiquitin sequence enhanced cytotoxic lymphocyte responses, Also, fragmenta tion of gag into subgenes broadened T-cell epitope recognition, We have fra gmented the genome by sequence-directed and random methods to create librar ies with different features, We propose that the characteristics of GLVs su pport their further investigation as an approach to protection against HIV and other viral pathogens.