Specific Antibodies of Epstein Barr Virus In patients with negative heterophile test, testing of specific antibodies is recommended. Viral capsid antigen (VCA) At the onset of infection anti-VCA IgG and anti-VCA IgM are present. IgM appears in early phase and disappears usually within 4-6 weeks. IgG appears in acute phase, peaks at 2-4 weeks and builds life-long immunity. Anti-VCA IgM does not solely suggest EBV infection as it Also suggests herpes virus infection. EBV Nuclear antigen (EBNA) When EBV enyters latent phase, EBNA is expressed. It usually appears after 6-12 weeks of initial presentation of symptoms. If this protein is present in the early course then it excludes the possibility of EBV infection. Early antigen (EA) In acute phase of EBV infection anti-EA IgG appears and it takes 3-6 months to resolve. However, if these proteins are absent then it does not exclude acute EBV infection.