Besides fluctuation in antibody response over time [23,24] and differences in the development of humoral response between individual animals [23], the most probable explanation for this observation is the fact that antibodies against the capsid arise early in the infection and tend to decline later in the infection [36,37,38] On the contrary, antibodies against the envelope glycoproteins, such as gp135, which are used in the Maeditect kit, are present at a later stage of the infection [25,36]. The gene discussed is ERVW-1; the disease is infection.