Immunization with recombinant Semliki Forest virus induces protection against influenza challenge in mice

The replicon of Semliki Forest virus (SFV) offers the possibility to direct high-level, transient expression of heterologous proteins in vivo. We init iated studies to determine the possibility of employing the SFV expression system for recombinant vaccine purposes. Mice immunized with recombinant SF V encoding Influenza A nucleoprotein (NP) or E. coli LacZ developed long-la sting antigen-specific IgG levels and induction of cytotoxic T-cell (CTL) m emory that persisted for over one year. Predominantly type 1 T-helper cells were induced as shown by IgG subclass ELISA. Humoral and cell-mediated imm une responses could be induced upon delivery by several administration rout es and mucosal immunizations induced secretory IgA in the respiratory tract . Development of immune responses against the vector itself did not inhibit boost responses by subsequent immunizations with recombinant SFV. Immuniza tion of mice with vectors encoding the Influenza A virus antigens nucleopro tein (NP) and hemagglutinin (HA) resulted in immune responses that were pro tective against challenge infection with Influenza virus. (C) 1999 Elsevier Science Ltd. All rights reserved.