Quantitative and qualitative analyses of the immune responses induced by a multivalent minigene DNA vaccine

Vaccine. 2000 Apr 14;18(20):2132-41. doi: 10.1016/s0264-410x(99)00546-0.

Abstract

Vaccines containing minigenes - isolated antigenic epitopes encoded by short open reading frames - can, under certain circumstances, confer protective immunity upon the vaccinee. Here we evaluate the efficacy of the minigene vaccine approach using DNA immunization and find that, to be immunogenic, a minigene-encoded epitope requires a perfect "Kozak" translational initiation region. In addition, using intracellular cytokine staining, we show that immunization with a plasmid encoding a full-length protein induces epitope-specific CD8(+) T cells which are detectable directly ex vivo, and constitute approximately 2% of the vaccinee's splenic CD8(+) T cells. In contrast, such cells are undetectable directly ex vivo in recipients of a minigene vaccine. Nevertheless, the minigene plasmid does induce a low number of epitope-specific CD8(+) T cells, which can be amplified to detectable levels by in vivo stimulation. Indeed, 4 days after in vivo stimulation (by virus infection), all vaccinated mice - regardless of whether they had been vaccinated with the minigene or with the full-length gene - had similar numbers of epitope-specific CD8(+) T cells. However, despite these strong responses at 4 days post-infection, recipients of the minigene vaccine showed no enhanced ability to limit virus replication and dissemination. We therefore observe a dichotomy; minigene vaccinees are not protected, despite the presence of strong virus-specific immune responses at 4 days post-challenge. We suggest that the protective benefits of vaccination exert themselves very soon - perhaps within minutes or hours - after virus challenge. If the vaccine-induced immune response is too low to achieve this early protective effect, virus-specific T cells will expand rapidly, but ineffectually, leading to the strong but non-protective response measured at 4 days post-infection. Thus, vaccine-induced immunity should be monitored very early in infection, since the extent to which these responses may later be amplified is largely irrelevant to the protection observed.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies, Viral / biosynthesis
  • Antibodies, Viral / immunology
  • Antigens, Viral / genetics
  • Antigens, Viral / immunology*
  • Base Sequence
  • CD8-Positive T-Lymphocytes / immunology
  • Codon / genetics
  • Cytokines / biosynthesis
  • Epitopes / genetics
  • Epitopes / immunology*
  • Genes, Synthetic
  • Immunity, Cellular
  • Lymphocyte Count
  • Lymphocytic choriomeningitis virus / genetics
  • Lymphocytic choriomeningitis virus / immunology*
  • Lymphocytic choriomeningitis virus / physiology
  • Mengovirus / genetics
  • Mengovirus / immunology*
  • Mengovirus / physiology
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Open Reading Frames
  • Plasmids / genetics
  • Plasmids / immunology
  • Regulatory Sequences, Nucleic Acid
  • Respiratory Syncytial Viruses / genetics
  • Respiratory Syncytial Viruses / immunology*
  • Respirovirus / genetics
  • Respirovirus / immunology*
  • Spleen / immunology
  • Time Factors
  • Vaccination
  • Vaccines, DNA / immunology*
  • Vesicular stomatitis Indiana virus / genetics
  • Vesicular stomatitis Indiana virus / immunology*
  • Viral Vaccines / immunology*
  • Virus Replication

Substances

  • Antibodies, Viral
  • Antigens, Viral
  • Codon
  • Cytokines
  • Epitopes
  • Vaccines, DNA
  • Viral Vaccines