Abstract
We have previously demonstrated the ability of the vaccine vectors based on replicon RNA of the Australian flavivirus Kunjin (KUN) to induce protective antiviral and anticancer CD8+ T-cell responses using murine polyepitope as a model immunogen (I. Anraku, T. J. Harvey, R. Linedale, J. Gardner, D. Harrich, A. Suhrbier, and A. A. Khromykh, J. Virol. 76:3791-3799, 2002). Here we showed that immunization of BALB/c mice with KUN replicons encoding HIV-1 Gag antigen resulted in induction of both Gag-specific antibody and protective Gag-specific CD8+ T-cell responses. Two immunizations with KUNgag replicons in the form of virus-like particles (VLPs) induced anti-Gag antibodies with titers of > or =1:10,000. Immunization with KUNgag replicons delivered as plasmid DNA, naked RNA, or VLPs induced potent Gag-specific CD8+ T-cell responses, with one immunization of KUNgag VLPs inducing 4.5-fold-more CD8+ T cells than the number induced after immunization with recombinant vaccinia virus carrying the gag gene (rVVgag). Two immunizations with KUNgag VLPs also provided significant protection against challenge with rVVgag. Importantly, KUN replicon VLP vaccinations induced long-lasting immune responses with CD8+ T cells able to secrete gamma interferon and to mediate protection 6 to 10 months after immunization. These results illustrate the potential value of the KUN replicon vectors for human immunodeficiency virus vaccine design.
Highlights
A major requirement for an effective human immunodeficiency virus (HIV) vaccine is the induction of potent, broad, and durable anti-HIV CD8ϩ T-cell immunity [11, 21, 28]
Immunization with KUNgag replicons delivered as plasmid DNA, naked RNA, or virus-like particles (VLPs) induced potent Gag-specific CD8؉ T-cell responses, with one immunization of KUNgag VLPs inducing 4.5-fold-more CD8؉ T cells than the number induced after immunization with recombinant vaccinia virus carrying the gag gene
In vitro-transcribed KUNgag RNA was transfected into BHK21 cells by electroporation and examined for KUN NS3 expression by indirect immunofluorescence (IIF) analysis with anti-NS3 antibodies and for HIV type 1 (HIV-1) gag expression and secretion by Radioimmunoprecipitation assay (RIPA) with anti-pr55gag antibody
Summary
A major requirement for an effective human immunodeficiency virus (HIV) vaccine is the induction of potent, broad, and durable anti-HIV CD8ϩ T-cell immunity [11, 21, 28]. Replicon vectors based on the flavivirus Kunjin (KUN) have recently been developed in our laboratories [18, 19, 40, 41] and show considerable potential for use as vaccine vectors for induction of protective CD8ϩ T-cell responses [3]. HIV Gag proteins are relatively conserved and the target of cross clade immunity [8, 26] Both CD4 and CD8ϩ T-cell immunity directed against Gag proteins are believed to be important for protection [10, 15]. T-cell and antibody responses and protected mice from challenge with recombinant vaccinia virus expressing the gag gene
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