Characterization of gamma2-human herpesvirus-8 glycoproteins gH and gL.

The gamma2 human herpesvirus-8 (HHV-8) or Kaposi's sarcoma associated herpesvirus (KSHV) ORFs 22 and 47 are counterparts to glycoproteins gH and gL, respectively, that are conserved among the members of herpesviruses. To define HHV-8 gH and gL, rabbit polyclonal antibodies were raised against GST-gH and GST-gL fusion proteins. Anti-gL and anti-gH antibodies reacted with the surface of virus carrying BCBL-1 cells. Both antibodies immunoprecipitated the HHV-8 envelope associated 120 kDa and 41-42 kDa proteins. In transfected COS-1 cells, gH was expressed as an endo-H sensitive 110 kDa glycoprotein, which was absent on the surface of the cells. However, after co-transfection with gL, gH was detected as an endo-H resistant 120 kDa glycoprotein, and was expressed on the surface of the cells. Non-covalent complex formation between gH and gL was detected in the transfected COS-1 cells. Anti-gH and anti-gL antibodies neutralized HHV-8 infectivity in the absence of complement, individually and more efficiently together. However, virus binding to the target cells was not inhibited. These studies suggest that HHV-8 gL is required for gH processing and expression on the cell surface membranes, and gH/gL complex plays an important role in the post-binding step of HHV-8 infection.