TARGETING OF HIV-1 ANTIGENS FOR RAPID INTRACELLULAR DEGRADATION ENHANCES CYTOTOXIC T-LYMPHOCYTE (CTL) RECOGNITION AND THE INDUCTION OF DE-NOVO CTL RESPONSES IN-VIVO AFTER IMMUNIZATION

CD8(+) cytotoxic T lymphocytes (CTLs) have the ability to recognize an d eliminate virally infected cells before new virions are produced wit hin that cell. Therefore, a rapid and vigorous CD8(+) CTL response, in duced by vaccination, can, in principle, prevent disseminated infectio n in vaccinated individuals who are exposed to the relevant virus. The re has thus been interest in novel vaccine strategies that will enhanc e the induction of CD8(+) CTLs. In this study, we have tested the hypo thesis that targeting an antigen to undergo more efficient processing by the class I processing pathway will elicit a more vigorous CD8(+) C TL response against that antigen. Targeting a type I transmembrane pro tein, the HIV-1 envelope (env) protein, for expression in the cytoplas m, rather than allowing its normal co-translational translocation into the endoplasmic reticulum, sensitized target cells expressing this mu tant more rapidly for lysis by an env-specific CTL clone. Additionally , a greatly enhanced de novo env-specific CTL response was induced in vivo after immunization of mice with recombinant vaccinia vectors expr essing the cytoplasmic env mutant. Similarly, targeting a cytoplasmic protein, HIV-1 nef, to undergo rapid cytoplasmic degradation induced a greatly enhanced de novo nef-specific CD8(+) CTL response in vivo aft er immunization of mice with either recombinant vaccinia vectors or DN A expression plasmids expressing the degradation targeted nef mutant. The targeting of viral antigens for rapid cytoplasmic degradation repr esents a novel and highly effective vaccine strategy for the induction of enhanced de novo CTL responses in vivo.