Epitope mapping of mouse monoclonal antibodies to the ppUL83 lower matrix phosphoprotein of human cytomegalovirus

Of nine mouse monoclonal antibodies (MAbs) directed against the lower matri x protein (pp65; ppUL83) of human cytomegalovirus (HCMV), all immunoprecipi tated the 65-kDa protein. Only five were reactive by Western blotting, howe ver, and four of these mapped to linear antigenic epitopes located between amino acids 184-195 (MAb C6), 343-357 (MAb C11), 448-462 (MAb C5), and 448- 459 (MAb C13). The epitope specificity of the fifth antibody (MAb C3) and t he four that recognised nonlinear sites could not be determined. Competitio n binding studies using HCMV antigen extracted from productively infected h uman embryonic lung fibroblasts (HELF), in an enzyme immunoassay (EIA), sho wed that three of the antibodies reactive with linear epitopes and two of t hose reactive with conformational epitopes (MAbs C3, C6, C11, C14, and C18) , were unique in their binding specificities. MAb C4 competed with MAb C8 a nd MAb C5 competed with MAb C13 for binding to ppUL83. One of the linear ep itopes identified, corresponding to amino acids SAFVFPTKDVAL (MAb C6), was an epitope described previously for CD8(+) cytotoxic T lymphocytes. J. Med. Virol. 57:290-297, 1999. (C) 1999 Wiley-Liss, Inc.