ERVW-1 and infection: For the genotype A infection (Figure 8) in sheep, only one sheep (20540) produced a specific antibody response against the capsid peptides 17–18–19, and it became only detectable at 9 months p.i. On the other hand, for different epitopes of the SU protein, an increase in the antibody response was observed for all three sheep starting at 6 months p.i. which further increased until 9 months p.i. For example, the antibody reactivity of sheep 90045 and 20540 against peptides 41, 130–134 and 159–160 roughly doubled every three months until the end of the experiment.