Serotypes (also referred to as serovars) are distinct variants within a viral or bacterial species that are differentiated based on their surface antigen composition and the immune response they elicit — specifically, the antibodies produced against them. In the context of gene therapy, serotype classification is particularly important for adeno-associated virus (AAV) and adenovirus, where different serotypes — such as AAV2, AAV5, AAV8, and AAV9 — exhibit distinct tissue tropism, receptor binding profiles, and immunogenicity, directly influencing vector selection, manufacturing platform design, and clinical outcome.
