Characterization of a major antigenic region on gp55 of human cytomegalovirus.

A major antigenic region localized to the C-terminal part of the 55K glycoprotein of human cytomegalovirus (HCMV) was mapped using synthetic peptides. Analysis of the region with six sera from healthy anti-HCMV seropositive blood donors showed that the length of the reactive sequence varied between four and eight amino acids (aa). The shortest sequence recognized was VTSG (aa 798 to 801 of the 130K precursor protein), but most sera required the three or four residues C-terminal to this to react, giving a major site of VTSGSTKD (aa 798 to 805). Using peptides immobilized on polyethylene pins, the importance of both interior (between aa essential for the binding of an antibody) and extension spacer residues was evident. Free peptides containing the reactive sequence were prepared for use in a conventional ELISA and optimal pH conditions for coating were determined. The best results were achieved at pH 2 to 3, which is in agreement with the advantageous net charge of these peptides at this low pH. Anti-HCMV positive sera showed a sensitivity of approximately 50% for both peptides on polyethylene pins and peptides coated onto plates.