HCMV is a highly complex virus harboring more than 20 different glycoproteins in its envelope [12, 13] . With respect to induction of neutralizing antibodies during natural infection, the glycoprotein (g) B dominates, but additional antigens such as the gM/gN complex and the gH/gL complex have also been identified as highly immunogenic [14] [15] [16] . Antibodies directed against gB can be detected in all naturally infected individuals [17] . Moreover, a major fraction of neutralizing antibodies in human sera seems to be directed against gB and the overall neutralizing capacity in sera from HCMV-seropositive donors correlates with anti-gB antibody titer [18] . In addition, anti-gB antibodies are effective in preventing cell-to-cell spread [19] . In the guinea pig CMV model, immunization with gB DNA vaccines confers protection from infection [20] . In a recent study protection from brain pathology in murine cytomegalovirus (MCMV) infected mice was accomplished by passive transfer of a gBspecific monoclonal antibody (mab) [21] . Thus, gB is an attractive antigen for inclusion in a human vaccine and has been part of a number of experimental vaccines [22, 23] . In fact, a recent phase 2 trial using recombinant gB as vaccine has shown significant protection from infection [24] . However, the spectrum of anti-gB antibodies developing during infection remains poorly defined.