Search for Anti-EA(D) Antibodies in Subjects with an “Isolated VCA IgG” Pattern

The presence of an “isolated viral capsid antigen (VCA) IgG” pattern in serum is not easy to interpret without the aid of further tests, such as specific immunoblotting or a virus genome search, that often give rise to organisational and economic problems. However, one alternative is to use an enzyme-linked immunosorbent assay (ELISA) to detect anti-early antigen (EA) antibodies, which can be found in about 85% of subjects with acute Epstein-Barr virus (EBV) infections. The purpose of this work was to search for anti-EA(D) antibodies in 130 samples with an isolated VCA IgG pattern at ELISA screening and classified as being indicative of past (102 cases) or acute (28 cases) infection on the basis of the immunoblotting results. Thirty-seven samples (28.5%) were positive for anti-EA(D), of which 25 (89.3%) had been classified by immunoblotting as indicating acute and 12 (11.8%) past EBV infection. This difference was statistically significant ( ). The results of our search for anti-EA(D) antibodies correctly identified nearly 90% of acute (presence) or past EBV infections (absence). When other tests are not available, the search for anti-EA antibodies may therefore be helpful in diagnosing patients with an isolated VCA IgG pattern at screening tests. 1. Introduction The most common manifestation of primary Epstein-Barr virus (EBV) infection is acute infectious mononucleosis, a self-limited clinical syndrome that most frequently affects adolescents and young adults. Serology is one of the cardinal means of diagnosing EBV infection as antibody search for viral capsid antigen (VCA), nuclear antigen (EBNA), and early antigen (EA) makes it possible to define the status of the infection [1, 2]. The three parameters of VCA IgG, VCA IgM, and EBNA-1 IgG generally make it simple to distinguish acute and past infection in immunocompetent patients [3]. The presence of VCA IgG and VCA IgM in the absence of EBNA-1 IgG is indicative of acute infection, whereas the presence of VCA IgG and EBNA-1 IgG in the absence of VCA IgM is typical of past infection. However, the presence of an isolated VCA IgG pattern may appear in about 8% of all subjects with at least one EBV infection marker [4] and may be difficult to interpret because it can be found in patients with prior infection as well as in those with acute infection. In fact, in some cases, VCA IgM may appear 1-2 weeks after VCA IgG, or for a very short time, or at such a low concentration as to be missed by conventional laboratory tests [5]; furthermore, VCA IgM may persist for a long time after acute infection and still