“…While VN antibodies are type-specific and give longer protection (up to a year), there is cross-reactivity between CF antibodies of EHV-1 and EHV-4; however, CF antibodies only last for about 3 months. The host humoral immunity is usually targeted to recognize epitopes on the surface of envelope glycoproteins of EHV-1 (Allen and Yeargan, 1987; Crabb et al, 1991; Packiarajah et al, 1998; Perkins et al, 2019), and IgGa, IgGb, IgGc, IgGd, IgM, and IgG(T) antibody isotypes have all been detected in EHV-1-infected horses (Paillot et al, 2008; Wagner et al, 2015; Perkins et al, 2019). The protective effect of circulating antibodies during infection with EHV-1 is limited once a state of cell-associated viremia is established.…”