INDUCTION OF HIV-1 ENVELOPE (GP120)-SPECIFIC CYTOTOXIC T-LYMPHOCYTE RESPONSES IN MICE BY RECOMBINANT CHO CELL-DERIVED GP120 IS ENHANCED BY ENZYMATIC REMOVAL OF N-LINKED GLYCANS

Priming of CD8(+) cytotoxic T lymphocyte (CTL) responses with recombin ant proteins has been facilitated by the development of novel adjuvant s that deliver antigens into the class I major histocompatibility comp lex (MHC) pathway. However, the extent to which secondary structure or glycosylation of these proteins prevents priming of class I MHC-restr icted CTL responses is not clear. To address this issue, recombinant H IV-1 gp120 envelope proteins produced in yeast, insect, or mammalian c ells were compared for the ability to elicit CD8(+) CTL activity in mi ce. Envelope-specific CD8(+) T lymphocytes were detected in BALB/c mic e immunized with env 2-3, a 55-kDa yeast-derived envelope protein that is not glycosylated and lacks a native conformation. This response wa s directed against a previously described epitope in the V3 region of gp120, as well as a newly identified epitope located near the carboxy- terminus of the molecule. Similar levels of V3-directed CTL activity w ere observed in mice immunized with recombinant gp120 produced in inse ct (Spodoptera fugiperda) cells using a baculovirus expression system (gp120BAC). In contrast, induction of CTL responses was considerably l ess efficient when mice were immunized with gp120CHO, a native, fully glycosylated envelope protein produced in mammalian CHO cells. Denatur ation of gp120CHO prior to immunization was not sufficient to prime CT L responses. However, envelope-specific CD8(+) CTL activity was elicit ed when N-linked glycans were removed by treatment with an endoglycosi dase. Possible mechanisms by which N-linked glycans influence delivery or processing of recombinant proteins for class I MHC presentation, a nd the implications of these findings for the design of subunit vaccin es, are discussed.