Selection and characterization of two specific monoclonal antibodies directed against the two variants of human herpesvirus-6

Monoclonal antibodies (mAbs) specific for human herpesvirus-6 (HHV6) protei ns were derived from the splenocytes of mice immunized with HHV6 TAN isolat e-infected peripheral blood mononuclear cells. The two mAbs 8C8 and 7C7 rea cted by means of immunofluorescence and immunoperoxidase assays with both v ariant A and variant B isolates giving two different staining patterns. In infected cells, cytoplasmic diffuse staining was observed with mAb 8C8, whe reas intense nuclear staining was obtained with mAb 7C7, These different lo cations of viral target proteins were confirmed by confocal microscopy. The mAb 8C8 reacted with a family of six glycoproteins designated as the gp72 complex in the case of variant A strains and gp63 complex in the case of va riant B strains. The endoglycosidases H and F reduced those glycoproteins t o a putative precursor molecule of 58 kDa, The mAb 7C7 reacted with 116 and 109 kDa proteins with the two HHV6 variants. These two mAbs did not neutra lize virion infectivity in the absence of complement. No cross-reactivity w as observed when these mAbs were used in immunoperoxidase assay and immunob lotting against the proteins of human cytomegalovirus or other human herpes viruses. Thus, the two mAbs 8C8 and 7C7 may be valuable tools for the diagn osis and biological investigation of HHV6 infections.