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A functional analysis of recombinant soluble CD46 in vivo and a comparison with recombinant soluble forms of CD55 and
D Christiansen1, J Milland, B R Thorley
1The Austin Research Institute, Heidelberg, Australia.
Insights
Recombinant soluble complement regulatory proteins CD46, CD55, and CD35 inhibit complement activation. Soluble CD46 demonstrated therapeutic potential by reducing inflammation in vivo.
Area of Science:
- Immunology
- Complement System Biology
Background:
- Cell surface proteins CD46, CD55, and CD35 regulate the complement system, protecting host cells.
- Recombinant soluble forms (rs) of these proteins have been explored for therapeutic applications in inflammatory conditions.
Purpose of the Study:
- To evaluate the in vitro efficacy of recombinant soluble CD46 (rsCD46), CD55 (rsCD55), and CD35 (rsCD35) in regulating classical and alternative complement pathways.
- To assess the in vivo therapeutic potential of rsCD46 in an immune complex-mediated inflammation model.
Main Methods:
- In vitro assays measuring the inhibition of human complement activation via classical and alternative pathways by rsCD46, rsCD55, and rsCD35.
- In vivo studies using a rat reverse passive Arthus reaction model to evaluate the effect of rsCD46 on immune complex-mediated inflammation.
Main Results:
- All three soluble proteins inhibited classical pathway activation in vitro, with rsCD35 being the most potent. A combination of rsCD46 and rsCD55 showed enhanced inhibition.
- rsCD46 and rsCD35 effectively inhibited alternative pathway activation in vitro, while rsCD55 was ineffective.
- In vivo, administration of rsCD46 significantly reduced lesion size, inflammatory infiltrate, and edema in the rat model.
Conclusions:
- rsCD46, rsCD55, and rsCD35 are effective inhibitors of complement activation, particularly the classical pathway.
- rsCD46 demonstrates significant therapeutic potential for inhibiting immune complex-mediated inflammation in vivo.
- These findings suggest that rsCD46, alongside rsCD55 and rsCD35, holds promise as a therapeutic agent for inflammatory diseases.
Abstract:
The human cell surface complement regulatory proteins CD46 (MCP), CD55 (DAF) and CD35 (CR1) protect autologous cells from complement-mediated damage by inhibiting C3 and C5 convertases. This regulatory potential has previously been exploited in the treatment of some models of inflammatory injury by the generation of recombinant soluble (rs) proteins, such as rsCD55 and rsCD35 . More recently, we have shown that rsCD46 inhibits complement activation in the fluid phase. In this report, the ability of rsCD46, rsD55 and rsCD35 to regulate human complement activation mediated by the classical pathway in vitro was clearly demonstrated by all three soluble proteins; however, rsCD35 was a more effective inhibitor than either rsCD46 or rsCD55. A combination of rsCD46+ rsCD55 was more potent than either of these proteins alone. Cell lysis via alternative pathway activation in vitro was efficiently regulated by rsCD46 and rsCD35 to a similar extent, whereas rsCD55 was not effective. Assays of rsCD46 in vivo have previously not been possible due to difficulties in expressing sufficient quantities of protein. This limitation has been overcome and now we report the ability of rsCD46 to inhibit immune complex-mediated inflammation in a rat using the reverse passive Arthus reaction model. Administration of rsCD46 significantly reduced the size of lesion, and histological examination showed a reduction in inflammatory infiltrate and edema. These data suggest that rsCD46, in addition to rsCd55 and rsCD35, may be useful a therapeutic agent.