Anti-CD32 (aa 287-316) polyclonal antibody

Polymorphisms in Fc-gamma-receptor (FCGR) genes as well as killer cell immunoglobulin-like receptor (KIR) and KIR ligand (KIRL) repertoires may influence antitumor effects of monoclonal antibodies (mAb). Here, we systematically analyzed high-and low-affinity FCGR2A and -3A genotypes as well as stimulating and inhibitory KIR/KIRL combinations in 53 neuroblastoma (NB) patients treated by long-term infusion (LTI) of anti-GD(2) IgG1 Ab ch14.18/CHO using validated real-time PCR methods. Patients with high-affinity FCGR2A and -3A genotypes showed a higher level of Ab-dependent cell-mediated cytotoxicity (ADCC) on day 8 after the start of ch14.18/CHO and superior event-free survival (EFS) compared to patients with low FCGR genotypes. Similar observations were made for patients with stimulatory KIR/KIRL haplotype B (combination of KIR genes including activating receptor genes) compared to inhibitory haplotype A (a fixed set of genes encoding for inhibitory receptors, except 2DS4) and stronger effects were found in patients when haplotype B and high-affinity FCGRs were combined. Surprisingly, independent analysis of KIRs showed a major role of activating KIR 2DS2 for high ADCC levels and prolongation of EFS. The greatest effect was observed in 2DS2-positive patients that also had high-affinity FCGR2A and -3A genotypes. In summary, the presence of the activating KIR 2DS2 has a major effect on ADCC levels and survival in NB patients treated by LTI of ch14.18/CHO and may therefore be a useful biomarker in combination with FCGR polymorphisms for Ab-based immunotherapies.

Introduction: The Fc gamma RIIa receptor is responsible for the clearance of large immune complexes and recently has been proved to be a C-reactive protein (CRP) receptor as well. A polymorphism in the corresponding FCG2RA gene resulting in an amino acid change (R131H) has been implicated, with conflicting results in the pathogenesis of various autoimmune or inflammatory disorders (e. g., atherosclerosis and coronary artery disease [CAD]). Methods: We recently developed a real-time polymerase chain reaction and melting curve analysis method for the genotyping of the above polymorphism. We further looked at its validity with bioinformatics study and DNA sequencing. Then we genotyped 134 CAD patients and 45 angiographically normal controls and determined serum high-sensitivity CRP by nephelometry (Dade-Behring). Also, we used apparently healthy platelet donors (n = 206) as a larger control group. Results: Our method is accurate and devoid of problems with homologs and copy number variants. The need for reference materials is stressed. There were statistically significant differences (p < 0.05) between the CAD patients and each of the two other control groups, with the percentage of RR genotype rising from 6.5% and 11% in the control groups to an average of 19% in all CAD patients (17%, 24%, and 18.5% in stable angina, unstable angina, and myocardial infarction, respectively). In a logistic regression model that included known risk factors for CAD including CRP, the RR genotype remained a significant predictor for CAD (odds ratio: 6.3 [1.1-36.3]). Also after linear regression analysis, CRP levels were reduced in the RR carriers (vs. HH + HR), controlling for age, sex, and disease (marginal p = 0.07). Conclusions: With our accurate genotyping method, the RR genotype was correlated with atherothrombotic CAD events. The inverse correlation found between CRP levels and genotype supports the in vitro data of RR cells binding CRP stronger than HH.