there is provided a biologically - active agent , in particular , for the early diagnosis and / or preventative therapy of virally - infected living cells , the efficacy of which is selective for the cell membranes of the virally - infected cells , which are modified after viral infection . the agent includes at least one component , selected from a group of materials , including recombinant human histone h1 or at least an h1 subtype or the active portion thereof . the appropriate biological activity for killing a virally - infected cell at the modified cell membrane thereof through cooperation with similarly or differently active agent components may be achieved , which together form a biologically - effective complex with increased biological activity .