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Updated: Feb 21, 2026
Intranasal Administration of Recombinant Influenza Vaccines in Chimeric Mouse Models to Study Mucosal Immunity
Published on: June 25, 2015
A novel C3d-containing oligomeric vaccine provides insight into the viability of testing human C3d-based vaccines in
Yong-Gang He1, Isabel Y Pappworth1, Andreas Rossbach2
1Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle-upon-Tyne, NE2 4HH, UK.
Abstract:
The use of C3d, the final degradation product of complement protein C3, as a "natural" adjuvant has been widely examined since the initial documentation of its immunogenicity-enhancing properties as a consequence of binding to complement receptor 2. Subsequently it was demonstrated that these effects are most evident when oligomeric, rather than when monomeric forms of C3d, are linked to various test protein antigens. In this study, we examined the feasibility of enhancing the adjuvant properties of human C3d further by utilizing C4b-binding protein (C4BP) to provide an oligomeric arrayed scaffold fused to the model antigen, tetanus toxin C fragment (TTCF). High molecular weight, C3d-containing oligomeric vaccines were successfully expressed, purified from mammalian cells and used to immunize groups of mice. Surprisingly, anti-TTCF antibody responses measured in these mice were poor. Subsequently we established by in vitro and in vivo analysis that, in the presence of mouse C3, human C3d does not interact with either mouse or even human complement receptor 2. These data confirm the requirement to develop murine versions of C3d based adjuvant compounds to test in mice or that mice would need to be developed that express both human C3 and human CR2 to allow the testing of human C3d based adjuvants in mouse in any capacity.
Insights
Human C3d, a complement protein fragment, was explored as an adjuvant. Researchers found it poorly elicited antibody responses in mice due to a lack of interaction with mouse complement receptor 2, necessitating further research.
Area of Science:
- Immunology
- Vaccine Development
- Complement System
Background:
- The complement protein C3d is a known natural adjuvant, enhancing immune responses by binding to complement receptor 2 (CR2).
- Oligomeric forms of C3d linked to antigens show enhanced immunogenicity compared to monomeric forms.
Purpose of the Study:
- To enhance the adjuvant properties of human C3d by creating oligomeric scaffolds using C4b-binding protein (C4BP).
- To evaluate the immunogenicity of C3d-based oligomeric vaccines fused to tetanus toxin C fragment (TTCF) in mice.
Main Methods:
- Constructed and expressed high molecular weight, C3d-containing oligomeric vaccines fused to TTCF in mammalian cells.
- Purified the vaccine constructs and immunized groups of mice.
- Assessed anti-TTCF antibody responses.
- Performed in vitro and in vivo analyses to investigate C3d-CR2 interactions in the presence of mouse complement C3.
Main Results:
- Successfully produced and purified C3d-TTCF oligomeric vaccines.
- Observed poor anti-TTCF antibody responses in immunized mice.
- Demonstrated that human C3d does not interact with mouse or human CR2 in the presence of mouse C3.
Conclusions:
- The poor immunogenicity of human C3d-based vaccines in mice is attributed to the lack of interaction with mouse complement receptor 2.
- Future studies require the development of murine C3d-based adjuvants or specialized mouse models expressing human C3 and CR2 for effective testing.
