Plasmid DNA expressing a secreted or a nonsecreted form of hepatitis C virus nucleocapsid: comparative studies of antibody and T-helper responses following genetic immunization.
In a murine model, we have compared humoral and T-helper (Th) responses induced following genetic immunization with two hepatitis C virus (HCV) plasmid-derived immunogens: a plasmid expressing the full-length nucleocapsid (CAP) as a nonsecreted antigen (pCMVC2) and a plasmid expressing the amino-terminal part of CAP as a secreted antigen (pS2S.C2N). In BALB/c mice, intramuscular injection of either plasmid induced IgG2a antibodies associated with a Th1-like profile characterized by the in vitro splenic production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). The pS2S.C2N plasmid induced antibody titers three- to five-fold higher than those obtained with the pCMVC2 plasmid (maximal titers 1:1,500 versus 1:500). In control experiments, immunization using purified CAP antigen induced a predominant, but not exclusive, Th2-like profile as determined by the splenic production of IL-4 and IL-10. Six putative Th determinants were identified using a panoply of overlapping synthetic peptides in in vitro stimulation assays: amino acids 20-44, 39-63, 79-113, 89-113, 118-142, and 138-152. For all CAP immunogens, MHC haplotype of immunized mice was found to influence seroconversion rates but not the type of cytokines produced in vitro. H-2d mice were faster responders and displayed recall T-cell activation by a larger number of peptides than H-2b mice, whereas H-2s mice were overall very poor responders. Splenic stimulation by at least one determinant, amino acids 79-103, appeared to be highly specific of the H-2b background and of DNA immunization only. These data indicate that DNA immunogens expressing different forms of HCV-CAP are not associated with different Th profiles but rather different seroconversion rates and antibody titers and that collaboration of distinct T-help epitopes can be restricted by the MHC background.
Inchauspe
G
G
INSERM U271, Unité de Recherche sur les Virus des Hépatites, Rétrovirus Humains et Pathologies Associées, Lyon, France.
Vitvitski
L
L
Major
M E
ME
Jung
G
G
Spengler
U
U
Maisonnas
M
M
Trepo
C
C
D000818:Animals; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology*; D006183:H-2 Antigens / Q000276:immunology; D016174:Hepacivirus / Q000235:genetics / Q000276:immunology*; D018937:Hepatitis C Antibodies / Q000096:biosynthesis; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000096:biosynthesis; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D016131:Lymphocyte Subsets; D051379:Mice; D008807:Mice, Inbred BALB C; D010455:Peptides / Q000138:chemical synthesis; D010957:Plasmids / Q000235:genetics; D013154:Spleen / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D019444:Vaccines, DNA / Q000235:genetics / Q000276:immunology*; D014758:Viral Core Proteins / Q000235:genetics / Q000276:immunology*; D014765:Viral Vaccines / Q000235:genetics / Q000276:immunology*
D000956:Antigens, Viral; D006183:H-2 Antigens; D018937:Hepatitis C Antibodies; D007074:Immunoglobulin G; D007376:Interleukin-2; D010455:Peptides; D019444:Vaccines, DNA; D014758:Viral Core Proteins; D014765:Viral Vaccines; C069130:nucleocapsid protein, Hepatitis C virus; D007371:Interferon-gamma