Recommendation for validation and quality assurance of non-invasive prenatal testing for foetal blood groups and implications for IVD risk classification according to EU regulations

BACKGROUND AND OBJECTIVES

Non-invasive assays for predicting foetal blood group status in pregnancy serve as valuable clinical tools in the management of pregnancies at risk of detrimental consequences due to blood group antigen incompatibility. To secure clinical applicability, assays for non-invasive prenatal testing of foetal blood groups need to follow strict rules for validation and quality assurance. Here, we present a multi-national position paper with specific recommendations for validation and quality assurance for such assays and discuss their risk classification according to EU regulations.

MATERIALS AND METHODS

We reviewed the literature covering validation for in-vitro diagnostic (IVD) assays in general and for non-invasive foetal RHD genotyping in particular. Recommendations were based on the result of discussions between co-authors.

RESULTS

In relation to Annex VIII of the In-Vitro-Diagnostic Medical Device Regulation 2017/746 of the European Parliament and the Council, assays for non-invasive prenatal testing of foetal blood groups are risk class D devices. In our opinion, screening for targeted anti-D prophylaxis for non-immunized RhD negative women should be placed under risk class C. To ensure high quality of non-invasive foetal blood group assays within and beyond the European Union, we present specific recommendations for validation and quality assurance in terms of analytical detection limit, range and linearity, precision, robustness, pre-analytics and use of controls in routine testing. With respect to immunized women, different requirements for validation and IVD risk classification are discussed.

CONCLUSION

These recommendations should be followed to ensure appropriate assay performance and applicability for clinical use of both commercial and in-house assays.

Protein Signatures of NK Cell-Mediated Melanoma Killing Predict Response to Immunotherapies

Despite impressive advances in melanoma-directed immunotherapies, resistance is common and many patients still succumb to metastatic disease. In this context, harnessing natural killer (NK) cells, which have thus far been sidelined in the development of melanoma immunotherapy, could provide therapeutic benefits for cancer treatment. To identify molecular determinants of NK cell-mediated melanoma killing (NKmK), we quantified NK-cell cytotoxicity against a panel of genetically diverse melanoma cell lines and observed highly heterogeneous susceptibility. Melanoma protein microarrays revealed a correlation between NKmK and the abundance and activity of a subset of proteins, including several metabolic factors. Oxidative phoshorylation, measured by oxygen consumption rate, negatively correlated with melanoma cell sensitivity toward NKmK, and proteins involved in mitochondrial metabolism and epithelial-mesenchymal transition were confirmed to regulate NKmK. Two- and three-dimensional killing assays and melanoma xenografts established that the PI₃K/AKT/mTOR signaling axis controls NKmK via regulation of NK cell-relevant surface proteins. A "protein-killing-signature" based on the protein analysis predicted NKmK of additional melanoma cell lines and the response of patients with melanoma to anti-PD-1 checkpoint therapy. Collectively, these findings identify novel NK cell-related prognostic biomarkers and may contribute to improved and personalized melanoma-directed immunotherapies. SIGNIFICANCE: NK-cell cytotoxicity assays and protein microarrays reveal novel biomarkers of NK cell-mediated melanoma killing and enable development of signatures to predict melanoma patient responsiveness to immunotherapies.

Sarcoidosis Following Hematopoietic Stem Cell Transplantation: Clinical Characteristics and HLA Associations

Purpose

Extrinsic factors and genetic predisposition contribute to the etiology of sarcoidosis, converging in a phenotype of altered immune response associated with multisystemic inflammatory granulomatous tissue infiltration. Immunological reconstitution after hematopoietic stem cell transplantation (HSCT) may represent a unique window for the pathogenesis of the disease. We describe the incidence, clinicopathological features, and HLA associations of sarcoidosis after HSCT in a single-center cohort of patients, together with data from previously published cases.

Methods

We retrospectively analyzed clinical characteristics and HLA haplotypes from allogeneic (allo) or autologous (auto) HSCT patients from January 2001 through May 2021 at the University Medicine Goettingen (UMG), and data from previously published cases.

Results

A total number of 19 patients was identified. These included 4 patients from our center (3 allo HSCT and 1 auto HSCT) and 15 patients from the literature review. Thirteen patients had received an allo HSCT, and six patients had received an auto HSCT. Sarcoidosis occurred after a median interval of 20 (after allo HSCT) and 7 (after auto HSCT) months, respectively. The predominant HLA allele associated with sarcoidosis was HLA DRB1*03:01. Sarcoidosis involved the respiratory tract in 15 patients (three unknown, one without pulmonary involvement), and it was associated with graft-versus-host disease in 7 of 13 patients receiving allo HSCT. None of the donors or patients had a history of sarcoidosis before transplantation. Disease manifestations resolved with standard glucocorticoid treatment without long-term sequelae.

Conclusion

Sarcoidosis may occur at low frequency during reconstitution of the immune system after HSCT. HLA allele associations reflect the associations observed in the general population, particularly with DRB1*03:01. Further insights into the interplay between Tcell reconstitution and the development of sarcoidosis could also provide novel approaches to an improved understanding of the pathogenesis in sarcoidosis.

Targeted deletion of murine coagulation factor XII gene-a model for contact phase activation in vivo

To analyze the biological role of factor XII (FXII, Hageman Factor) in vivo, we generated mice deficient for FXII using a gene targeting approach on two distinct genetic backgrounds, i.e. mixed C57Bl/6J X 129X1/SvJ and inbred 129X1/SvJ. Homozygous FXII knockout (FXII-/-) mice showed no FXII plasma activity and had a markedly prolonged activated partial thromboplastin time (aPTT). In contrast, coagulation factors XI, VIII, IX, X,VII,V, II and fibrinogen did not differ between FXII-/- mice and their wild-type littermates. Heterozygous matings segregated according to the Mendelian inheritance indicating that FXII deficiency does not increase fetal loss. Furthermore, matings of FXII-/- males and FXII-/females resulted in normal litter sizes demonstrating that total FXII deficiency in FXII-/females does not affect pregnancy outcome. Also, gross and histological anatomy of FXII-/mice was indistinguishable from that of their wild-type littermates on both genetic backgrounds. Thus it appears that deficiency of murine FXII does not cause thrombophilia or impaired fibrinolysis in vivo. These results indicate that FXII deficiency does not affect hemostasis in vivo and we anticipate that the FXII-/mice will be helpful to elucidate the biological role(s) of FXII in health and disease.

HFE genotype and parameters of iron metabolism in German first-time blood donors - evidence for an increased transferrin saturation in C282Y heterozygotes

BACKGROUND

Hemochromatosis is usually inherited in an autosomal recessive mode and associated with missense mutations in the hemochromatosis gene (HFE), an HLA class 1 related gene. However the degree of penetrance is presently matter of debate.

METHODS

To elucidate the frequency of HFE mutations in a German population and the relationship between genotype and phenotype, we determined the HFE C282Y and H63D genotypes in 500 first-time blood donors using an allele-specific ligase chain reaction (LCR). Ferritin and transferrin saturation (TS) of all donors found to have at least one mutation were compared to gender- and age-matched controls.

RESULTS

The C282Y allele frequency was 46 in 1000 chromosomes (4.6 %). The allele frequency of H63D was 108 in 1000 (10.8 %) chromosomes. We found three persons homozygous for H63D, nine compound heterozygotes and none homozygous for C282Y. TS was elevated in C282Y heterozygotes (p = 0.002) and C282Y/H63D compound heterozygotes (p = 0.04) compared to wild-type controls. Serum ferritin tended to be elevated in compound heterozygotes (p = 0.053). Mean corpuscular volume (MCV) and hemoglobin (MCH) were not different from controls.

CONCLUSION

The frequency of HFE mutations in the tested population was comparable to those of other northern European populations. The elevated TS in subjects carrying a single copy of the C282Y mutation suggests that C282Y heterozygosity is associated with an increased intestinal iron absorption and might therefore offer a selection advantage in conditions of iron depletion.

Durchflußzytometrische Untersuchungen zur Verträglichkeit von Thrombozytentransfusionen

We developed a flow cytometric crossmatch (FC-CM) for the selection of compatible donors for thrombocytopenic patients and compared its predictive value for a successful platelet transfusion in a prospective study to LCT. In case of alloimmunization, FC-CM detects bound IgG on lymphocytes and/or platelets after incubation with patient’s serum. Based on the posttransfusion increment in 122 transfusions, the specifity was 81% for LCT and 96% for FC-CM (platelet gate). In conclusion, the FACS-CM is a rapid and useful assay for donor selection in cases of alloimmunized patients with lymphocytotoxic and/or platelet-specific antibodies.