An immunogenic composition is provided herein. The immunogenic compositions are used to identify and select immunogenic antigens that elicit immune responses in a subject and may be subsequently used in multi-antigen vaccine compositions against one or more diseases or conditions. According to some embodiments, the immunogenic composition may include a plurality of nucleic acid fragments or minigenes derived from a nucleic acid library, wherein each nucleic acid fragment encodes a different antigen or functional portion thereof, and wherein the different antigens or functional portions thereof are associated with one or more disease or condition. The immunogenic composition may also include a delivery medium loaded with the plurality of nucleic acid fragments and in some embodiments, the delivery medium is loaded with nucleic acid fragments in such a way that individual antigen presenting cells receive only a subset of the nucleic acids within a vaccine in order to minimize antigenic competition.
