Key Genes of the Immune System and Predisposition to Acquired Hemophilia A: Evidence from a Spanish Cohort of 49 Patients Using Next-Generation Sequencing

Acquired hemophilia A (AHA) is a rare bleeding disorder caused by the presence of autoantibodies against factor VIII (FVIII). As with other autoimmune diseases, its etiology is complex and its genetic basis is unknown. The aim of this study was to identify the immunogenetic background that predisposes individuals to AHA. HLA and KIR gene clusters, as well as KLRK1, were sequenced using next-generation sequencing in 49 AHA patients. Associations between candidate genes involved in innate and adaptive immune responses and AHA were addressed by comparing the alleles, genotypes, haplotypes, and gene frequencies in the AHA cohort with those in the donors' samples or Spanish population cohort. Two genes of the HLA cluster, as well as rs1049174 in KLRK1, which tags the natural killer (NK) cytotoxic activity haplotype, were found to be linked to AHA. Specifically, A*03:01 (p = 0.024; odds ratio (OR) = 0.26[0.06-0.85]) and DRB1*13:03 (p = 6.8 × 103, OR = 7.56[1.64-51.40]), as well as rs1049174 (p = 0.012), were significantly associated with AHA. In addition, two AHA patients were found to carry one copy each of the low-frequency allele DQB1*03:09 (nallele = 2, 2.04%), which was completely absent in the donors. To the best of our knowledge, this is the first time that the involvement of these specific alleles in the predisposition to AHA has been proposed. Further molecular and functional studies will be needed to unravel their specific contributions. We believe our findings expand the current knowledge on the genetic factors involved in susceptibility to AHA, which will contribute to improving the diagnosis and prognosis of AHA patients.

Unraveling the Influence of Common von Willebrand factor variants on von Willebrand Disease Phenotype: An Exploratory Study on the Molecular and Clinical Profile of von Willebrand Disease in Spain Cohort

The clinical diagnosis of von Willebrand disease (VWD), particularly type 1, can be complex because several genetic and environmental factors affect von Willebrand factor (VWF) plasma levels. An estimated 60% of the phenotypic variation is attributable to hereditary factors, with the ABO blood group locus being the most influential. However, recent studies provide strong evidence that nonsynonymous single nucleotide variants (SNVs) contribute to VWF and factor VIII phenotypic variability in healthy individuals. This study aims to investigate the role of common VWF SNVs on VWD phenotype by analyzing data from 219 unrelated patients included in the "Molecular and Clinical Profile of von Willebrand Disease in Spain project." To that end, generalized linear mixed-effects regression models were fitted, and additive and epistatic analyses, and haplotype studies were performed, considering five VWD-related measures (bleeding score, VWF:Ag, VWF:RCo, factor VIII:C, and VWF:CB). According to these analyses, homozygotes: for p.Thr789Ala(C) would be expected to show 39% higher VWF:Ag levels; p.Thr1381Ala(C), 27% lower VWF:Ag levels; and p.Gln852Arg(C), 52% lower VWF:RCo levels. Homozygotes for both p.Thr789Ala(C) and p.Gln852Arg(T) were predicted to show 185% higher VWF:CB activity, and carriers of two copies of the p.Thr1381Ala(T)/p.Gln852Arg(T) haplotype would present a 100% increase in VWF:RCo activity. These results indicate a substantial effect of common VWF variation on VWD phenotype. Although additional studies are needed to determine the true magnitude of the effects of SNVs on VWF, these findings provide new evidence regarding the contribution of common variants to VWD, which should be taken into account to enhance the accuracy of the diagnosis and classification of this condition. ClinicalTrials.gov identifier: NCT02869074.

Unraveling the effect of silent, intronic and missense mutations on VWF splicing: contribution of next generation sequencing in the study of mRNA

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074.

Role of multimeric analysis of von Willebrand factor (VWF) in von Willebrand disease (VWD) diagnosis: Lessons from the PCM-EVW-ES Spanish project

The multimeric analysis (MA) of plasma von Willebrand factor (VWF) evaluates structural integrity and helps in the diagnosis of von Willebrand disease (VWD). This assay is a matter of controversy, being considered by some investigators cumbersome and only slightly informative. The centralised study ‘Molecular and Clinical Profile of von Willebrand Disease in Spain (PCM-EVW-ES)’ has been carried out by including the phenotypic assessment and the genetic analysis by next generation sequencing (NGS) of the VWF gene (VWF). The aim of the present study was to evaluate the role of MA to the diagnosis of these patients and their potential discrepancies. Two hundred and seventy out of 480 patients centrally diagnosed with VWD had normal multimers, 168 had abnormal multimers and 42 a total absence of multimers. VWF MA was of great significance in the diagnosis of 83 patients (17.3%), it was also of help in the diagnosis achieved in 365 additional patients (76%) and was not informative in 32 cases (6.7%). With regard to discrepancies, 110 out of 480 (23%) patients centrally diagnosed with VWD presented some kind of discordance between VWF:RCo/VWF:Ag and/or VWF:CB/VWF:Ag ratios, multimeric study and/or genetic results. The VWF MA was key in the presence of novel mutations as well as in cases with phenotypic discrepancies. A comparison between the contribution of MA and VWF:CB showed a clearly higher contribution of the former in the diagnostic process. These data seem to reinforce the relevance of the VWF MA in VWD diagnosis, despite all its limitations.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): comprehensive genetic analysis by next-generation sequencing of 480 patients

Molecular diagnosis of patients with von Willebrand disease is pending in most populations due to the complexity and high cost of conventional molecular analyses. The need for molecular and clinical characterization of von Willebrand disease in Spain prompted the creation of a multicenter project (PCM-EVW-ES) that resulted in the largest prospective cohort study of patients with all types of von Willebrand disease. Molecular analysis of relevant regions of the VWF, including intronic and promoter regions, was achieved in the 556 individuals recruited via the development of a simple, innovative, relatively low-cost protocol based on microfluidic technology and next-generation sequencing. A total of 704 variants (237 different) were identified along VWF, 155 of which had not been previously recorded in the international mutation database. The potential pathogenic effect of these variants was assessed by in silico analysis. Furthermore, four short tandem repeats were analyzed in order to evaluate the ancestral origin of recurrent mutations. The outcome of genetic analysis allowed for the reclassification of 110 patients, identification of 37 asymptomatic carriers (important for genetic counseling) and re-inclusion of 43 patients previously excluded by phenotyping results. In total, 480 patients were definitively diagnosed. Candidate mutations were identified in all patients except 13 type 1 von Willebrand disease, yielding a high genotype-phenotype correlation. Our data reinforce the capital importance and usefulness of genetics in von Willebrand disease diagnostics. The progressive implementation of molecular study as the first-line test for routine diagnosis of this condition will lead to increasingly more personalized and effective care for this patient population.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): Proposal for a new diagnostic paradigm

The diagnosis of von Willebrand disease (VWD) remains difficult in a significant proportion of patients. A Spanish multicentre study investigated a cohort of 556 patients from 330 families who were analysed centrally. VWD was confirmed in 480. Next generation sequencing (NGS) of the whole coding VWF was carried out in all recruited patients, compared with the phenotype, and a final diagnosis established. A total of 238 different VWF mutations were found, 154 were not included in the Leiden Open Variation Database (LOVD). Of the patients, 463 were found to have VWF mutation/s. A good phenotypic/genotypic association was estimated in 96.5% of the patients. One hundred seventy-four patients had two or more mutations. Occasionally a predominant phenotype masked the presence of a second abnormality. One hundred sixteen patients presented with mutations that had previously been associated with increased von Willebrand factor (VWF) clearance. RIPA unavailability, central phenotypic results disagreement and difficult distinction between severe type 1 and type 3 VWD prevented a clear diagnosis in 70 patients. The NGS study facilitated an appropriate classification in 63 of them. The remaining seven patients presented with a VWF novel mutation pending further investigation. In five patients with a type 3 and two with a type 2A or 2B phenotype with no mutation, an acquired von Willebrand syndrome (AVWS) was suspected/confirmed. These data seem to support NGS as a first line efficient and faster paradigm in VWD diagnosis.

Neutrophil CD64: diagnostic accuracy and prognostic value in patients presenting to the emergency department

The purpose of this study was to evaluate the diagnostic accuracy and prognostic value of neutrophil CD64 expression for bacterial infection in febrile adult patients presenting to our hospital emergency department. We prospectively included 132 patients with fever ≥ 38ºC (≥ 100.4ºF) during the last 24 hours and we measured CD64 expression on neutrophils the day after admission at the emergency department. We followed the patients until full recovery or death. There were 115 (87%) patients with bacterial infection and 108 (94%) of them survived. There were 17 (13%) patients without bacterial infection and 12 (71%) of them survived. Patients with bacterial infection and patients who survived showed a CD64 index higher when compared with patients without bacterial infection and patients who died, respectively (3.7 ± 3.2 vs. 2.5 ± 2.3; p = 0.03; and 3.7 ± 3.1 vs. 1.7 ± 0.6; p = 0.002; Mann-Whitney U test). The receiver operating characteristic (ROC) curve analysis for detecting bacterial infection and predicting survival with the CD64 index showed an area under curve (AUC) of 0.66 (95% CI, 0.52-0.8; p = 0.03) and 0.71 (95% CI, 0.57-0.85; p = 0.01), respectively. Diagnostic accuracy and prognostic value of CD64 expression was good in adult patients with fever.

Neutrophil CD64 expression as marker of bacterial infection: a systematic review and meta-analysis

OBJECTIVE

We performed a systematic review and meta-analysis of studies to evaluate the diagnostic accuracy of expression of CD64 on polymorphonuclear neutrophils (PMN) as a marker for bacterial infection.

METHODS

The analysis included studies of patients from all age groups that prospectively evaluated CD64 expression on PMNs for the diagnosis of bacterial infection. We evaluated the methodological quality of the studies according to the 25-item criteria developed by the Standards for Reporting of Diagnostic Accuracy (STARD) committee. We calculated a summary receiver operating characteristic (SROC) curve across studies included in the meta-analysis.

RESULTS

The methodological quality score of the 13 included studies ranged from 9 to 16 points (maximum score was 25 points). The pooled sensitivity and specificity for CD64 expression on PMNs were 79% (95% CI: 70-86%) and 91% (95% CI: 85-95%), respectively. The area under curve (AUC) was 0.94.

CONCLUSIONS

On the basis of this meta-analysis, CD64 expression on PMNs could be a useful diagnostic cell-based parameter of bacterial infections. However, published studies about this topic showed a low methodological quality.