Abstract <p>An approach is proposed to using membrane filtration in the development of methodologies for obtaining horseradish peroxidase-based conjugates for the detection of viral infections. This approach is significantly simpler, faster, and more cost-effective than chromatographic methods. Nearly no conjugate losses occur during the purification of the components. A procedure for the membrane purification of horseradish peroxidase and its analysis via capillary electrophoresis is proposed. The procedure also ensures the preparation of horseradish peroxidase conjugates with viral antigens for use in enzyme-linked immunosorbent assays (ELISA) for the detection of class M antibodies against a virus (in the M antibody capture modification). The practice of utilizing various diagnostic kits prepared with this approach is described, for example, in ELISA test systems, for diagnosing diseases caused by viruses like West Nile, Crimean–Congo hemorrhagic fever, tick-borne encephalitis, and others.</p>