From the Guidelines
After 2 weeks of clinical symptoms of Epstein-Barr virus (EBV) infection, IgG antibodies would typically be high. This is because, as noted in the 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM) 1, the presence of VCA IgM (with or without VCA IgG) antibodies in the absence of antibodies to EBNA indicates recent primary infection with EBV. Given that EBV has a long incubation period, by the time clinical symptoms appear, the body has already started to mount an immune response. Some key points to consider include:
- The antibody response to EBV infection follows a predictable pattern, with IgM antibodies rising first and IgG antibodies beginning to rise shortly after and continuing to increase 1.
- The presence of EBNA antibodies indicates infection more than 6 weeks from the time of the sample and therefore not likely implicating EBV as a cause 1.
- Over 90% of the normal adult population has IgG class antibodies to VCA and EBNA antigens, although approximately 5%–10% of patients who have been infected with EBV fail to develop antibodies to the EBNA antigen 1. Considering these points, it is reasonable to expect IgG to be high after 2 weeks of clinical symptoms, as this timeframe allows for the immune system to have mounted a significant response to the infection, characterized by increasing levels of IgG antibodies.
From the Research
EBV Infection and IgG Levels
- The incubation period of symptomatic primary EBV infection is approximately six weeks 2.
- During this period, the immune response to EBV infection is not fully understood, but it is known that the virus can evade the host's immune surveillance through multiple mechanisms 3.
- The diagnosis of acute EBV infection is often based on the combination of positive viral capsid antigen (VCA) IgM antibodies and negative EB viral nuclear antigen 1 (EBNA-1) IgG antibodies 4.
IgG Avidity and EBV Infection
- Determination of EBV IgG avidity can help clarify the EBV status in patients with unclear serology 4, 5.
- IgG avidity is typically low in the early stages of EBV infection and increases over time 4, 5.
- In immunocompetent patients, low IgG avidity is often associated with acute primary infection, while high IgG avidity is associated with past infection 5.
Expected IgG Levels after 2 Weeks of Clinical Symptoms
- Given that the incubation period of EBV infection is approximately six weeks, it is likely that IgG levels would still be increasing 2 weeks after the onset of clinical symptoms.
- Studies have shown that IgG avidity is typically low in the early stages of EBV infection and increases over time 4, 5.
- Therefore, it would be expected that IgG levels would be relatively low 2 weeks after the onset of clinical symptoms, but increasing as the infection progresses 4, 5.