Genetic vaccination with Flt3-L and GM-CSF as adjuvants: Enhancement of cellular and humoral immune responses that results in protective immunity in a murine model of hepatitis C virus infection.
OBJECTIVE
To investigate whether transfection of plasmid DNA encoding these cytokines enhances both humoral and cellular immune responses to hepatitis C virus (HCV) in a murine model.


METHODS
We established a tumor model of HCV infection using syngenic mouse myeloma cells stably transfected with NS5. Co-vaccination of DNA encoding granulocyte macrophage colony-stimulating factor (GM-CSF) and Flt-3 ligand together with a plasmid encoding for the HCV NS5 protein was carried out. Mice were sacrificed 14 d after the last immunization event with collection of spleen cells and serum to determine humoral and cellular immune responses.


RESULTS
Co-vaccination of DNA encoding GM-CSF and Flt-3 ligand together with a plasmid encoding for the HCV NS5 protein induced increased antibody responses and CD4+ T cell proliferation to this protein. Vaccination with DNA encoding GM-CSF and Flt-3L promoted protection against tumor formation and/or reduction in mice co-immunized with cytokine-encoding DNA constructs. This suggests this strategy is capable of generating cytotoxic T lymphocyte activity in vivo. Following inoculation with plasmid DNA encoding Flt-3L, no increase in spleen size or in dendritic cell (DC) and natural killer cell numbers was observed. This was in contrast to a dramatic increase of both cell types after administration of recombinant Flt3-L in vivo. This suggests that vaccination with plasmid DNA encoding cytokines that regulate DC generation and mobilization may not promote unwanted side effects, such as autoimmunity, splenic fibrosis or hematopoietic malignancies that may occur with administration of recombinant forms of these proteins.


CONCLUSIONS
Our data support the view that plasmid DNA vaccination is a promising approach for HCV immunization, and may provide a general adjuvant vaccination strategy against malignancies and other pathogens.
Encke
Jens
J
Gastroenterology, Hepatology, Infectious Diseases, Intoxications, Department of Internal Medicine IV, University of Heidelberg Medical School, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany. jens_encke@med.uni-heidelberg.de
Bernardin
Jomo
J
Geib
Jasmin
J
Barbakadze
Gocha
G
Bujdoso
Raymond
R
Stremmel
Wolfgang
W
D000276:Adjuvants, Immunologic / Q000627:therapeutic use*; D000818:Animals; D000917:Antibody Formation; D000956:Antigens, Viral; D015870:Gene Expression; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000627:therapeutic use*; D016174:Hepacivirus / Q000276:immunology; D006526:Hepatitis C / Q000276:immunology / Q000517:prevention & control*; D007111:Immunity, Cellular; D008565:Membrane Proteins / Q000627:therapeutic use*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D010957:Plasmids; D013602:T-Lymphocytes, Cytotoxic; D014162:Transfection; D014611:Vaccination / Q000379:methods*; D019444:Vaccines, DNA / Q000627:therapeutic use; D017361:Viral Nonstructural Proteins; D012324:RNA-Dependent RNA Polymerase
D000276:Adjuvants, Immunologic; D000956:Antigens, Viral; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D008565:Membrane Proteins; D019444:Vaccines, DNA; D017361:Viral Nonstructural Proteins; C084881:flt3 ligand protein; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase