Effects of intravenous immunoglobulin on platelet count and antiplatelet antibody disposition in a rat model of immune thrombocytopenia

First Report of the Italian Registry on Immune-Mediated Congenital Heart Block (Lu.Ne Registry)

Objective: Neonatal Lupus (NL) is a rare syndrome caused by placental transfer of maternal anti-SSA/Ro and anti-La/SSB autoantibodies to the fetus. The rarity of this condition requires the establishment of multidisciplinary registries in order to improve our knowledge.

Method: Inclusion criteria in this retrospective study were the maternal confirmed positivity for anti-SSA/Ro and/or anti-SSB/La antibodies, and the presence of II or III degree congenital heart block (CHB) in utero or neonatal period (up to 27 days after birth).

Result: Eighty-nine cases of CHB were observed in 85 women with 88 pregnancies that occurred between 1969 and 2017. CHB was mostly detected in utero (84 cases, 94.2%), while five cases were observed in the neonatal period. A permanent pacemaker was implanted in 51 of 73 children born alive (69.8), whereas global mortality rate was 25.8% (23 cases): 16 in utero, five perinatal, and two during childhood. By univariate analysis, factors associated with fetal death were pleural effusion (p = 0.005, OR > 100; CI 95% 2.88->100 and hydrops (p = 0.003, OR = 14.09; CI 95% 2.01–122). Fluorinated steroids (FS) were administered in 71.4% pregnancies, and its use was not associated with better survival. Some centers treated all cases with fluorinated steroids and some centers did not treat any case. CHB was initially incomplete in 24 fetuses, and of them five cases of II degree block reverted to a lower degree block after treatments. Recurrence rate in subsequent pregnancies was 17.6% (3 out of 17). A prophylactic treatment was introduced in 10 of these 16 subsequent (58.8%) pregnancies, mostly with FS or high dose intravenous immunoglobulins.

Conclusion: This is the first report from the Italian Registry of neonatal lupus/CHB. The live birth rate was nearly 80%, with nearly two thirds of the children requiring the implantation of a pacemaker. The management of fetuses diagnosed with CHB was heterogeneous across Italian Centers. The registry at present is mainly rheumatological, but involvement of pediatric cardiologists and gynecologists is planned.

The neonatal Fc receptor (FcRn) is not required for IVIg or anti-CD44 monoclonal antibody–mediated amelioration of murine immune thrombocytopenia

To definitively determine whether the neonatal Fc receptor (FcRn) is required for the acute amelioration of immune thrombocytopenia (ITP) by IVIg, we used FcRn-deficient mice in a murine ITP model. Mice injected with antiplatelet antibody in the presence or absence of IVIg displayed no difference in platelet-associated IgG between FcRn deficient versus C57BL/6 mice. FcRn-deficient mice treated with high-dose (2 g/kg) IVIg or a low–dose (2 mg/kg) of an IVIg-mimetic CD44 antibody were, however, protected from thrombocytopenia to an equivalent extent as wild-type mice. To verify and substantiate the results found with FcRn-deficient mice, we used β2-microglobulin–deficient mice (which do not express functional FcRn) and found that IVIg or CD44 antibody also protected them from thrombocytopenia. These data suggest that for both high-dose IVIg as well as low-dose CD44 antibody treatment in an acute ITP model, FcRn expression is neither necessary nor required.

Comparison of the effects of antibody-coated liposomes, IVIG, and anti-RBC immunotherapy in a murine model of passive chronic immune thrombocytopenia

The present work evaluated antibody-coated liposomes as a new treatment strategy for immune thrombocytopenic purpura (ITP) through the use of a mouse model of the disease. Effects of antimethotrexate antibody (AMI)-coated liposomes and intravenous immunoglobulin (IVIG)-coated liposomes (15, 30, 60 micromol lipid/kg) were compared with the effects of IVIG (0.4, 1, 2 g/kg) and anti-red blood cell (anti-RBC) monoclonal antibody immunotherapy (TER119, 5, 15, 25, and 50 microg/mouse) on MWReg30-induced thrombocytopenia. Each treatment was found to attenuate thrombocytopenia in a dose-dependent manner and, consistent with previous work, IVIG was found to increase antiplatelet antibody clearance in a dose-dependent manner. TER119 demonstrated greater effects on thrombocytopenia relative to other therapies (peak platelet counts: 224% +/- 34% of initial platelet counts for 50 microg TER119/mouse versus 160% +/- 34% for 2 g/kg IVIG, 88% +/- 36% for 60 micromol lipid/kg AMI-coated liposomes, and 80% +/- 25% for 60 micromol lipid/kg IVIG-coated liposomes). However, the effects of TER119 were associated with severe hemolysis, as TER119 decreased RBC counts by approximately 50%. The present work demonstrated that antibody-coated liposomes attenuated thrombocytopenia in this model at a much lower immunoglobulin dose than that required for IVIG effects and, in contrast with TER119, antibody-coated liposomes increased platelet counts without altering RBC counts.