ERVW-1 and infection: Viable cysts were observed in less than 30% of pigs with class 2 responses, and degenerated cyst infections represented 43.2% of pigs with any cysts in this class, reflecting the persistence of antibody responses to antigens GP42-39 and GP24, which are frequent in class 2 (T24/42 antigen family) [23,43], which may explain the presence of antibodies to these antigens in pigs with degenerated or resolved infections [34].