Session Information
Session Type: ACR Poster Session C
Session Time: 9:00AM-11:00AM
Background/Purpose:
Antiphospholipid Syndrome (APS) is an autoimmune rheumatic
disorder in which antiphospholipid antibodies (aPL)
cause clinical events including vascular thrombosis (VT) and pregnancy
morbidity (PM). The key antigen in APS is beta-2-glycoprotein I (beta2GPI),
which consists of five domains. The N-terminal domain (DI) carries the main immunodominant epitope. We previously showed that
recombinant human DI blocks binding of serum IgG from patients with APS
(APS-IgG) to whole beta2GPI in ELISA and inhibits
thrombosis induced by APS-IgG in a mouse model. A modified variant containing
two point mutations (DI(D8S,D9G)) was a stronger
inhibitor than wild-type DI. Small molecules such as DI require modification to
make them viable as therapeutic agents. Chemical addition of polyethylene
glycol (PEGylation) is one such modification
, which increases half-life and reduces immunogenicity. Conversely,
PEGylation can also reduce binding to ligands/receptors and biological
activity. Larger PEG sizes may enhance half-life more but reduce activity more.
Therefore, we investigated whether PEGylated DI of various sizes retain the
ability to inhibit beta2GPI
-binding of serum IgG and IgA from patients with APS.
Methods:
DI was expressed in E.Coli and
PEGylated on its disulphide bonds. Three different PEGylated variants carrying
20kDa, 30 kDa and 40 kDa
PEG were produced as well as non-PEGylated DI. Serum samples from four patients
with APS, all fulfilling the Sydney classification criteria, were tested in an
inhibition ELISA. This ELISA tests for binding of IgG or IgA to beta2GPI
in the presence or absence of 100mcg/ml inhibitor. Results are expressed as the
retained binding in presence of each inhibitor compared to binding with no
inhibitor (defined as 100%).
Results:
Figure 1 shows results for IgG. All PEGylated and
non-PEGylated variants of DI significantly inhibit binding to beta2GPI
by between 43-55% (P<0.05). Figure 2 shows results for IgA. All
PEGylated and non-PEGylated variants of DI significantly inhibit binding to beta2GPI
by between 40-55% (P<0.005). There were no significant differences
between results for the different DI variants, showing that PEGylation does not
alter inhibitory capacity of DI in this binding assay.
Similarly we showed that DI (D8S,D9G)
carrying 20kDa PEG inhibits binding to beta2GPI of serum IgG (P<0.01) and IgA (P<0.005) from
patients with APS. PEG alone shows <10% inhibition.
Conclusion:
PEGylation of DI and DI (D8S,D9G) allows retention of their
ability to inhibit binding of both IgG and IgA from APS patients to beta2GPI,
an important step in potential development as a therapeutic agent.
To cite this abstract in AMA style:
McDonnell T, Pericleous C, Ioannou Y, Giles I, Rahman A. Pegylated Recombinant Domain I of Beta-2-Glycoprotein I, a Potential Therapeutic Agent for Antiphospholipid Syndrome, Fully Retains Its Ability to Inhibit Binding of IgG or IgA Antibodies from Patients with APS to Beta-2-Glycoprotein I in Vitro [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/pegylated-recombinant-domain-i-of-beta-2-glycoprotein-i-a-potential-therapeutic-agent-for-antiphospholipid-syndrome-fully-retains-its-ability-to-inhibit-binding-of-igg-or-iga-antibodies-from-patient/. Accessed .« Back to 2015 ACR/ARHP Annual Meeting
ACR Meeting Abstracts - https://acrabstracts.org/abstract/pegylated-recombinant-domain-i-of-beta-2-glycoprotein-i-a-potential-therapeutic-agent-for-antiphospholipid-syndrome-fully-retains-its-ability-to-inhibit-binding-of-igg-or-iga-antibodies-from-patient/