cryptotope cryptotope a cryptotope is an antigenic site or epitope hidden in a protein or virion by surface subunits. cryptotopes are antigenically active only after the dissociation of protein aggregates and virions some infectious pathogens are known to escape immunological targeting by b-cells by masking antigen-binding sites as cryptotopes. a cryptotope can also be referred to as a cryptic epitope. cryptotopes are becoming important for hiv vaccine research as a number of studies have shown that cryptic epitopes can be revealed or exposed when hiv gp120 binds to cd4.