Vaccines for the future--an update

Humoral and cell-mediated immune responses to recombinant vaccinia viruses in mice

Intravenous (i.v.) immunization of mice with recombinant vaccinia viruses stimulated the highest antibody and cytotoxic T lymphocyte (CTL) responses when i.v., intraperitoneal (i.p.), intranasal (i.n.), footpad (f.p.) and tail scarification (t.s.) routes were compared. Intraperitoneal immunization of mice resulted in high CTL activity, but low antibody responses. Antibody levels after i.n., f.p., and t.s. immunization were slightly lower than following i.v. immunization. Although very low levels of CTL primary activity were stimulated by i.n. or f.p. inoculation of recombinant vaccinia virus, levels of secondary CTL activity after in vitro restimulation of splenocytes were as high as those seen from i.v. immunized splenocytes. The effect of the thymidine kinase (TK) phenotype of the virus also was examined. Wildtype (TK positive) viruses replicated to a higher titre in vivo and stimulated higher antibody and CTL responses than a TK negative recombinant virus. A recombinant virus that expressed the TK gene from herpes simplex virus at a low level was intermediate between wildtype and TK negative virus, both in virus replication in vivo and in immunogenicity.

MHC-restricted recognition of immunogenic T cell epitopes of pertussis toxin reveals determinants in man distinct from the ADP-ribosylase active site

The S1 subunit of Pertussis toxin (PT) is responsible for the reactogenicity and in part the immunogenicity of Bordetella pertussis vaccine. The critical residues associated with the immunomodulatory effects of PT were located around Glu140 in the S1 subunit. In man, T cell responses to PT are directed at S1 peptides distinct from Glu140. Two such epitopes, p64-75 and p151-161, are immunogenic in a panel of individuals covering a wide range of HLA genotypes. The response to PT peptides is HLA class II restricted. The response to p64-75 is blocked by an anti-HLA-DQ mAb, while that to p151-161 is blocked by an anti-HLA-DR mAb. These findings may allow for the development of a B. pertussis vaccine free from reactogenicity.