Dr. Drew et al., The human IgG3 hinge mediates the formation of antigen dimers that enhancehumoral immune responses to DNA immunisation, VACCINE, 19(30), 2001, pp. 4115-4120
A series of plasmid DNA constructs containing the 45W antigen gene from Tae
nia oris were used to investigate the impact of antigen dimerisation on the
humoral immune response to genetic immunisation. Genes encoding dimeric 45
W were generated via fusion to the hinge region of human IgG3 (hIg). This r
egion was selected because it is compact and contains 11 inter-chain disulp
hide-bridges. The DNA encoding the IgG3 hinge contains four exons, with the
last three exons being repeats and possibly superfluous. Plasmids containi
ng the 45W gene linked to exons 1-2, 1-3 or 1-4 of the hIgG3 hinge, were co
mpared to a control plasmid containing a form of the 45W gene which encodes
secreted, monomeric 45W protein. Western blot analysis was used to investi
gate the formation of the fusion-proteins in transfected Cos-7 cells. The f
ull-length fusion construct expressed predominantly dimeric forms of the fu
sion-protein, while truncation of the hinge region decreased the abundance
of dimeric fusion-protein and increased the proportion monomeric fusion ant
igen. In immunised BALB/c mice, 45W-specific antibody titres were increased
3 to 4-fold via fusion to the full-length hinge region, whereas the trunca
ted constructs were similar to the control. IgG subclass analysis indicated
that all mice generated predominantly IgG1, IgG2a and IgG2b antibodies. Th
erefore, these results suggest that the efficient formation of dimeric anti
gen, via fusion to the full-length hinge of human IgG3, can increase the im
munogenicity of expressed antigens without altering the form of the immune
response elicited by DNA immunisation. (C) 2001 Elsevier Science Ltd. All r
ights reserved.