Mechanisms of action of IVIg: What do we really know?

Transcription

1 Plasma Protein Biotechnology Meeting 2013, Lanzarote, Spain May 15, 2013 Mechanisms of action of IVIg: What do we really know? Alan H. Lazarus, PhD Canadian Blood Services St. Michael s Hospital University of Toronto

2 Outline How does IVIg work in autoimmunity? There are too many theories to explain how IVIg works! Present evidence against: FcRn Fc³ RIIB IgG sialylation Evidence for immune complexed IgG acting on Dendritic cells via activating Fc³ R œdc-sign

3 Intravenous Immunoglobulin IVIg is IgG Fc F(ab ) 2

4 Mechanisms of IVIg How does IVIg work in autoimmunity? ITP (murine passive ITP) Inflammatory arthritis (murine krn serum transfer) EAE (Murine model of MS)

5 IVIg Beneficial-Yes/likely CIDP ITP and HIV-ITP Hypogammaglobulinemia Guillain-Barré syndrome Kawasaki disease Kidney transplantation: HLA sensitization Toxic epidermal necrolysis, Stevens-Johnson syndrome Dermatomyositis, polymysitis Autoimmune uveitis Stiff-person syndrome Fetal/neonatal alloimmune thrombocytopenia Post transfusion purpura Autoimmune neutropenia Multifocal Motor Neuropathy Demyelinating Polyneuropathies associated with IgG or IgA monoclonal gammopathies Acute exacerbations in Myasthenia Gravis Lambert-Eaton Myasthenic syndrome Source: Immunoglobulin Therapy Lazarus AH, Semple JW, eds. Bethesda, MD: AABB Press, 2010

6 Most mechanistic studies in murine ITP Platelet count Yippee! Good idea? IVIg? Harrington hours Time post serum injection

7 Immune thrombocytopenia (ITP) Platelet

8 The first demonstration that IVIg has ameliorative effects in an autoimmune disease

9 How does IVIg work?

10 We don t know how IVIg works and the IVIg puzzle has been difficult to solve with results that often seem to be in conflict with each other

11 The players Block Fc receptors (RES blockade) Anti-idiotypic antibodies complement Neonatal Fc receptor Fc³ RIIB (Inhibitory) Immune complex Dendritic cells DC-SIGN Fc sialylation T regulatory cells Fc³ RIII (Activating)

12 The players: There are too many Block Fc receptors (RES blockade) Anti-idiotypic antibodies complement Immune complex Dendritic cells DC-SIGN Neonatal Fc receptor Fc³ RIIB (Inhibitory) Fc³ RIII (Activating)?? Fc sialylation? T regulatory cells

13 What is the FcRn and how does it work? FcRn protects IgG from degradation in adults From, Roopenian et al, Nature Reviews Immunology 7,

14 Hypothesis IVIg works (at least in part) by saturating FcRn, thereby increasing catabolism of all IgG antibodies, including pathogenic IgG.

15 FcRn deficient mice are protected from ITP to the same extent as wild-type mice. Platelet count x 10 9 /L Nil anti-plt IVIg Nil anti-plt IVIg Wild-type FcRn KO

16 FcRn: Conclusion IVIg can ameliorate murine ITP in the absence of FcRn or ² 2M (required for functional FcRn expression).

17 The players: There are too many Immune complex Dendritic cells DC-SIGN Neonatal Fc receptor Fc³ RIIB (Inhibitory) Fc³ RIII (Activating)?? Fc sialylation? T regulatory cells

18 What is the major signaling pathway involved in FcγRIIB inhibitory function? SHP-1 Not SHIP, SHP-1, or Btk Crow et al. Blood 102:558, 2003

19 IVIg ameliorated murine ITP in Fc³ RIIB deficient mice on the BALB/C background IVIg ameliorated murine ITP in Fc³ RIIB deficient mice only on a mixed (B6;129) genetic background

20 SLE Prone mice BALB/c C57BL/6 B6.129 Fc³ RIIB +/+ yes yes yes Fc³ RIIB -/- yes yes no

21 (NZW x BXSB) F1 male mice

22

23 There were no significant differences in the percentages or numbers of CD14+CD32B+ monocytes, or in the percentage of CD14+CD32B+ monocytes present in (20) children with ITP before and after IVIG therapy.

24 The players: There are too many Immune complex Dendritic cells DC-SIGN Fc³ RIIB (Inhibitory) Fc³ RIII (Activating)? Fc sialylation? T regulatory cells

25 DC-SIGN Fc³ RIIB (M ) IL-4 Baso IL-33

26 DC-SIGN Fc³ RIIB (M ) IL-4 Baso IL-33

27 The players: There are too many Immune complex Dendritic cells DC-SIGN Fc sialylation? T regulatory cells Fc³ RIII (Activating)

28 The players: There are too many Immune complex Dendritic cells DC-SIGN Fc³ RIII (Activating) T regulatory cells Block Fc receptors (RES blockade)

29 Cell-associated (anti-d like effect) Soluble or RBC OVA OVA OVA

30 Endogenous soluble antigens Platelet count x10 9/ L Treatment *** ** *** *** ** IVIG anti-albumin anti-transferrin non-immune IgG anti-platelet antibody

31 2006

32 Proposed model of IVIg action in murine ITP DC-SIGN Fc³ RIII Siragam et al, J Clin Invest 2005 Aloulou et al, Blood 2012 Siragam et al, Nat Med 2006 Huang et al, Blood 2010 ITP

33 Proposed model of IVIg action in ITP ITP Tha-In et al, Blood 2007 Ephrem et al, Blood 2008 Aubin et al, Blood 2010

34 Conclusions (IVIg) IVIg has beneficial effects in a large number of seemingly unrelated autoimmune diseases and inflammatory states Evidence against the concept that IVIg requires the neonatal Fc receptor (FcRn) for its function Evidence against the concept that IVIg interacts or requires the inhibitory Fc receptor (Fc³ RIIB) for its function Evidence against a simple role of Fc sialic acids in mediating IVIg effects IVIg may interact with activating FcRs on dendritic cells in the initiation of its effects

35 Acknowledgements Collaborators: Derry Ropenian John Semple Steve Mckenzie Mike Reilly Funding: CBS CIHR Health Canada

36 IVIg effectiveness and pharmacology in a model autoimmune disease A. IVIg; standard single dose B. IVIg; maximal continuous dosing C. IVIg; single dose with decay D. IVIg; low cont. Infusion E. IVIg; 2/week