and Division of Molecular Biology', CSIRO, North Ryde
Temporal regulation of influenza hemagglutinin expression in vaccinia virus recombinants and effects on the immune response*
Regulation of the expression of influenza AIPW8134 hemagglutinin (HA) by the vaccinia virus promoters PF (early), P7.5 (early and late) and P L l l (late) has been demonstrated using HA-vaccinia recombinant viruses W-PR8-HA3, W-PR8-HA6 and W-PR&HA, respectively. Levels of H A on the surface of W-PR8-HA3 (PF)infected cells were lower than with either W-PR8-HA6 (P7.5) or W-PR8-HA8 (PL11). Expression of H A under the control of the late promoter P L l l was inhibited in the absence of DNA replication. All three recombinant viruses stimulated a specific antibody response in mice which was dependent on the presence of infectious virus. Recognition of HA by cytotoxic T lymphocytes (CTL) was assessed by the ability of the viruses to stimulate naive precursors in vivo, to restimulate primed CTL in vitro and by target cell recognition. H A expressed under the control of either of the promoters with early function (PF or P7.5) was recognized by CTL when W-PR8-HA3 or VV-PR8-HA6 were used to prime or restimulate splenocytes or to infect target cells. On the other hand, H A expressed by W-PR8-HA8 (PL11) failed to prime for a CTL response in naive C B N H mice, was ineffective at restimulation of primed splenocytes and failed to produce target cells for recognition by specific CTL. However, in BALBIc mice W-PR8-HA8 did prime for a specific CTL response. These studies show that H A synthesized early in infection was recognized by both B and T cells while H A expressed after DNA replication was not generally recognized by T cells. The implications of the observations with the late promoter with respect to the use of late promoters in potential vaccinia virus-based vaccines are considered.
* This work was carried out as part of a joint CSIRO-ANU project.
Technical assistance was provided in part by a grant from the Reserve Bank of Australia, Rural Credits Development Fund.