ABSTRACT
The humoral response to DNA vaccination of mice with two important Fasciola antigens has been investigated. Both F. gigantica fatty acid binding protein (FABP) and F. hepatica cathepsin L5 (FhCatL5) were shown to be expressed in COS 7 cells and induced a humoral response when delivered as secretory constructs in mice. FABP induced an IgGl dominant response, with significant IgE, IgG2a, and IgG2b responses also present, indicating a mixed Th1/Th2 response. The total Ig response peaked at 1:24,500 and antibody titers were sustained for at least 32 weeks. In contrast, the delivery of FABP as a nonsecreted construct did not result in the induction of a measurable humoral response. FhCatL5 was delivered as a secretory construct, with secretion mediated by the native F. hepatica signal sequence, which was shown to operate in COS 7 cells. The humoral response peaked at 1:2000 at week 8 and was sustained for at least 20 weeks. Antibody isotype analysis demonstrated a Th2-like response, which was qualitatively different from that obtained for FABP with an IgE dominant response, and lower titers to IgG1 and IgG3. The results demonstrate that Fasciola antigens can be delivered as DNA vaccines, but that the quality of the response varies between antigens and is influenced by the method of vaccine delivery.
Subject(s)
Antibodies, Helminth/biosynthesis , Carrier Proteins/immunology , Cathepsins/immunology , Endopeptidases , Fasciola/immunology , Fascioliasis/prevention & control , Neoplasm Proteins , Nerve Tissue Proteins , Vaccines, DNA/immunology , Animals , Antigens, Differentiation/genetics , Antigens, Differentiation/immunology , Antigens, Helminth/genetics , Antigens, Helminth/immunology , Blotting, Western , Carrier Proteins/genetics , Cathepsin L , Cathepsins/genetics , Cysteine Endopeptidases , Enzyme-Linked Immunosorbent Assay , Fasciola/genetics , Fasciola hepatica/genetics , Fasciola hepatica/immunology , Fatty Acid-Binding Protein 7 , Fatty Acid-Binding Proteins , Female , Mice , Mice, Inbred BALB CABSTRACT
The humoral responses in mice following vaccination with DNA constructs encoding Fasciola hepatica glutathione S-transferase (GST) have been evaluated. GST47 cDNA was subcloned into two DNA vaccine vectors, VR1012 and VR1020, which direct expression to the cytoplasmic and extracellular compartments, respectively. Expression was confirmed by transfection into COS 7 cells. Groups of mice were vaccinated with these constructs, by either intramuscular injection with the VR1012-or VR1020-based constructs, or intradermal vaccination (with a gene gun) with the VR1020-based construct. Vaccination with the construct designed for secretion resulted in an increased humoral response compared to vaccination with the nonsecretory construct. The level of the total humoral response after vaccination with the secretion construct was not dependent on the route of vaccination. However, the isotype profile of the response differed between the groups; intramuscular vaccination with the construct directing cytoplasmic expression yielded an immuoglobulin (Ig)G2a dominant (Th1-type) response, intradermal vaccination with the secretory construct a IgG1/IgE dominant (Th2-type) response, and intramuscular vaccination with the secretory construct a mixed isotype response. These results demonstrate that the immunogenicity of a DNA vaccine based on Fasciola GST, as well as the isotype of the response against GST, is determined by the mode of vaccine administration.
