Seroepidemiology of EBV and interpretation of the 'isolated VCA IgG' pattern

摘要

Epstein-Barr virus (EBV) is ubiquitous., and about 90% of the world adult population has anti-EBV antibodies. Acute infection is generally asymptomatic in immunocompetent children and presents as infective mononucleosis in 30-50% of cases involving immunocompetent adolescents and adults. Like other herpes viruses, EBV follows a productive lytic cycle and establishes latent infection in the host. Primary EBV infection induces both humoral and cellular immune responses. Humoral responses include antibodies against lytic and latent antigens: although not always measurable, the levels of anti-EA antibodies increase for 3-4 weeks and then usually become undetectable after 3-4 months but low levels may be detected for years. The antibodies against gp 350/220 are particularly important in limiting the spread of infection and preventing reinfection. VCA IgG antibodies generally appear at the onset of clinical symptoms of acute infection and remain positive throughout life. VCA IgM antibodies usually present together with VCA IgG but sometimes may appear earlier. Levels generally decrease after a few weeks and become undetectable. Anti-EBNA-2 antibodies appear early and may be present in up to 30% of individuals at the time of disease but, as antibodies to EBNA-1, they are not generally detectable during the first 3-4 weeks after the appearance of clinical symptoms. EBNA-1 IgG antibodies are considered an indication of past infection.